Exam 2 Study Guide
Exam 2 Study Guide 80887 - BIOL 3150 - 001
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Anatomy Study Guide Chapter 6 Cartilage and Bone Connective Tissue 1 Describe the skeleton and determine why it is dynamic The skeleton is an internal framework that supports the organs and constantly rebuilds and remodels bone while it interacts with organ systems It is a composite structure of bone cartilage ligaments and other connective tissues that stabilize and connect bones What is cartilage and name the 3 functions it serves Cartilage is semirigid CT that is weaker yet more flexible and resilient than bone It serves as a support system for soft tissues like the trachea it provides gliding surfaces for articulations and provides a model for bone formation What are the 3 types of cartilage and describe characteristics they possess Hyaline cartilage is the most abundant that supports the body and is flexible and resilient at the same time It is surrounded by the perichondrium It is prevalent in articulation sites Fibrocartilage is numerous in thick collagen fibers and is used for tensile and compressional forces which is a reason it lacks the perichondrium It is found in our vertebrae and intercalated discs as shock absorbers Elastic cartilage is highly branched elastic fibers that are highly flexible and the form support Is the perichondrium which is composed of dense CT it is found in articulation sites and other parts of the body like the ears Describe the cells in cartilage and which ones are maintain destroy and build These types of cartilage have cells scattered throughout the matric of protein fibers embedded in the ground like substance that are called chondroblasts secrete the matrix and these mature into chondrocytes which is where the cell is found along with mature cartilage cells and lacunae The chondrocyte maintains matrix and tissues overall for our health and viability Describe hyaline cartilage Hyaline cartilage has fibroblasts in the pericardium that helps lay down dense CT A chondrogenic cell becomes a chondroblast The chondroblasts lay down the matrix by secretion and becomes a chondrocyte The chondrocyte maintains the integrity of the cartilage Lacunae are in the chondrocytes There are chondrocyte nests that are isogenous groups these are groups with the same genotypes or similar genotypes What are the growth patterns of cartilage and how do they grow throughout aging Cartilage grows interstitially and appositionally during embryonic development however the interstitial declines rapidly as cartilage matures with the later growth of mainly appositional growth Once cartilage is mature the new cartilage growth typically stops but it resumes when damage occurs Appositional growth is growing on the outside near the perichondrium and the interstitial growth grows within Define what a bone is and what it is composed of Cone is a complex dynamic organ that is primarily composed of osseous tissue that is observed in other tissue types to keep in mind The bone is sturdy and rigid due to mineral deposition within ECM What are the functions of the bone Support and protection structural support and serves as internal framework for the entire body It protects delicate tissueorgans from injury like the ribcage Movement attachment sites for skeletal muscles as well as other soft tissues and organs The skeletal muscle pulls on the skeleton using the bones as a series of levers Movement can be gross or precise Hemopoiesis in the medullary cavity blood formation occurs in the red bone marrow and the location varies with age Storage of mineral and energy reserves Ca and Phosphate storage release yellow bone marrow is for adipose tissue sites that serves as energy reserves How are bones classified Bones can be classified as long length is longer than the width with an elongated shaft called the diaphysis and 2 distinct ends called the epiphyses Short length and width are similar for ex patella Flat thin flattened and usually curved This provides extensive SA for muscle attachment and protection for underlying soft tissues lrregular elaborate complex shape ex coccyx bone 10 Discuss the structure and anatomy of a long bone 11 N Eiphyeealdieke Articular cartilage quot Prcmmal Spiel39le acne z epiphyeie Space cccupied by red marrcw Endcetelum 39 ma h sis Ccmpact y y 391 p y I I filled ullary cavity 1quot Yellow marrcw L Periceteumv H Dietal epiphyeie Femur Proximal closest to the body Metaphysis holds the epiphyseal line Articular cartilage is usually hyaline cartilage and connected to periosteum and inner layer endosteum Medullary cavity yellow marrow in there with vascularization Perforating fibers inner layer of periosteum helps keep periosteum associated with the bone What is the periosteum what is it comprised of and what functions does it serve The periosteum is comprised of dense irregular CT with a fibrous outer layer and cellular inner layer It isolates and protects the bone from surrounding structures anchors blood vessels and 12 13 14 15 16 17 18 19 20 21 22 nerves to surface and provides osteoprogenitor cells and osteoblasts for bone growth appositional and fracture repair What is the endosteum and what is it responsible for It is an incomplete layer than contains osteoprogenitor cells osteoblasts and osteoclasts which are important for bone growth repair and remodeling What is an osteoprogenitor cell and its function These arise from mesochyme and become osteoblasts They are located in the inner cellular layer of the periosteum the endosteum and lining osteonic canals What is an osteoblast and its function Osteoblast build the ECMosteoid What is an osteocyte and its function Osteocytemaintains the bone matrixhealth of the bone and it is a sensor for stress What does a healthy bone have to have as far as cells go in the bone Osteoblasts and osteoclasts must balance each other What are the organic components of the bone matrix Cells osteocytes osteoblasts and osteoclasts as well as the osteoid ground substance and collagen fiberssynthesized or secreted by osteoblasts What are the inorganic components of the matrix and what do these serve a purpose for Hydroxyapatites or mineral salts accounts for about 65 of bone mass Ca phosphate Ca3PO4 also interacts with another salt Ca hydroxide CaOH2 to form crystals of hydroxyapatite Ca10PO46OH2 as crystals form incorporate other Ca salts and ions like Na Mg amp F It forms around collagen fibers gives bone its hardness What are characteristics of a compact bone Compactdenselamellarcortical bone What are characteristics of a spongy bone Cancelloustrabecular bone Where is spongy and compact bone found Spongy is found in the head and down the diaphysis of a long bone and compact is found on the outside Describe the anatomy of a compact bone and include central canal lacuna caniculi osteons and the lamellae in the osteons 23 24 25 26 27 Compact Bone Tissue External circumferential lamellae Osteon Central canal Canallcull Lamellae Venule Arteriole Perforating fibers 3quot A A f 391 39 39 9 22in J Imam raw H 39 Blood vessels a Innervation is in the central canal The little dots that look like spiders are the lacuna with the little legs that come off are caniculi The osteocytes are in the lacuna Within the osteons we have lamellae concentric interstial circumferential Spongy bone do not have osteons they have parallel lamella Trabeculae of spongy bone Perforating Central canals canal The compact bone is constructed of plates or lamellae of bone Osteon group of hollow tubes of bone matrix each placed outside the next collagen fibers run in same direction within a lamellae but in opposite direction in adjacent lamellae The function of this is to resist forces that are upon it such as twisting What do spongy bone lack that compact bones have They lack osteons and they have parallel lamella What is the significance of a salt crystal in compact bone It is the inorganic compound of the matrix and it keeps spaces open for lacunae What is the mineralized bridges for in a bone Mineralized bridges break when there is a force of on the compact bone instead of the bone breaking This is advantageous for not breaking or fracturing the bone but it is able to deal with the forces that act upon it The minerals dissipate after the bridges break The bone is able to handle MORE stress because of these bridges Describe the characteristics of a spongy bone and the function of the composition of spongy bone It appears to be disorganized but trabeculae align along lines of stress to assist the bone when multidirectional stress is applied The trabeculae are only a few cell layers thick It doesn t have any osteons it has irregular lamellae that is parallel The function of spongy bone is for cross bracing reducing weight and supports and protects marrow red and yellow What is ossification ontogenesis calcification 28 29 30 31 32 33 34 35 36 37 Osteogenesis physical process of bone formation Ossification process of replacing other tissue with bone Calcification deposition of calcium salts Does a bone grow in width or inside throughout life A bone grows in thickness throughout life When does bone skeleton begin 8 weeks of development What does the skeleton growth determine It determines size and proportions of the body Define the intramembranous ossification and name what it gives rise to dermal ossification It is the embryonic development of flat bones from an embryonic tissue called the mesenchyme It gives rise to flat bone This is more in depth of the process Osteoblast lay down osteoid then it becomes calcified and we are building bone The osteoblast form woven bone primary bone first bone type that is make in this ossification and it is NOT well organized as this process is going on The areas forms trabecular vascularization and mesenchyme layers start to differentiate which forms the periosteum Woven bone is replaced with IameIIar bonesecondary bone It can be compact or spongy bone Describe endochondral ossification specifically in long bones and then list differences in short and irregular bones The hyaline cartilage model develops cartilage calcifies and periosteal bone collar forms around the diaphysis brings in vascular and other cell types like bone forming cells and this becomes the primary ossification center in the shaft region The secondary ossification happens in the epiphyses and then the bone replaces the cartilage except for the articular cartilage In a short bone there is only 1 primary ossification center Irregularossification is all over What is vascularized spongy bone in the middle called Diploid Why does endochondrial bone formation involve so many steps It ensures the newborn has a working bone and can develop to an adult form The multiple stages give us flexibility It allows us to modify flexibility and reshape for an adult the skeleton needs options to grow and modify its shape to keep its body proportional Why is the endochondrial not completely formed in a fetus The template allows us to do this during fetal development and during adolescents Remodeling gives us the ability to change the shape and modify our skeleton for when we mature How does bone grow The bone grows in length interstitial growth or in diameter appositional We know what interstitial growth it can you name the 5 regions that are continuous in the bone Zone 1 secures epiphysis to EP zone of cartilage 38 39 40 41 42 43 44 45 46 47 48 Zone 2rapidly growing enlarge arranged in longitudinal columns proliferation Zone 3stops dividing and enlarges hypertrophy Zone 4 narrow minerals deposited in matrix between columns chondrocytes die calcification Zone 5 longitudinal channels form invaded by capillaries and osteoprogenitor cells lay down bone on matrix frame newly formed bone What is epiphyseal cartilage and how does it grow Hyaline cartilage plate in the metaphysis at each end of a long bone The plate is found in children and adolescents in adults who have stopped growing As long as epiphyseal cartilage can grow enlarge the bone will continue to increase in length Osteoblasts new bone amp epiphyseal cartilage grow at same rate At puberty combination of sex hormones GH amp TH stimulate bone growth dramatically with osteoblasts producing bone at a greater rate than epiphyseal cartilage expansion Epiphyseal cartilage gradually disappears completing epiphyseal growth closure Where does appositional growth take place What does it do in a bone It occurs within the periosteum and along medullary cavity in the bone matrix in parallel to surface circumferential lamellae It increases structures width It resorption of bone matrix and retains proportions Define bone remodeling Bone remodeling or bone metabolism is a lifelong process where mature bone tissue is removed from the skeleton a process called bone resorption and new bone tissue is formed a process called ossification or new bone formation How is bone remodeling stimulated It is stimulated by stress placed on the bone Where does bone remodeling happen What does it do in these places It occurs at both periosteal and endosteal surfaces this modifies architecture of bone and changes the total amount of mineral deposited in skeleton maintains Ca and P levels in body fluids Why does bone remodeling differ depending on location The age influences rates and compact bone replaces slower than spongy bone What does wolff s law state It states the importance of needing mechanical stress and cardioweight baring exercise to help the bone grow and remodel in response to applied forces and stress The medial side of the leg is for compression forces and the lateral side of the leg is for tension forces What does it mean if you say bone is mechanosensitive It is an organ that alters structure to suit to its mechanical environment What does mechanical loading generate in the bone Pressure gradients that drive IF through the lacunarcanalicular system that is sensed by the osteocytes and lets the bone know how much and where the IF is moving What is mechanotransduction It is the process by which physical forces are converted into biochemical signals which are integrates into cellular response Describe the blood supply and innervation in a bone where does it arise from Where does it enter from Where do the NUTRIENTS arise from 49 50 51 52 53 54 55 56 57 It arises from nervous tissue and enters from the periosteum The nutrients such as nutrient vessels supply diaphysis and enter central canals of osteons within compact bone and marrow cavity The metaphyseal vessels supply the diaphyseal side of the EP The epiphyseal vessels supply the epiphysis The periosteal vessels supply the superficial osteons within compact bone at external ends of the shaft enter perforating canals within the shaft What does vascularization tell to our bones Mainly sensory and signal injury Where do nerves enter the bone through when accompanied by the blood vessels Nutrient foramen artery What are the effects of hormones on bones What activity do hormones focus on in bones It controls growth patterns by alter activity of osteoblasts and osteoclasts It focuses on osteoclasts activity Name some of the hormones and their functions in bones Growth Hormone stimulate liver somatomedins that directly stimulate cartilage growth at EP Thyroid Hormone influences the BMR of bone cells Calcitonin T encourage Ca deposition into bone depresses osteoclast activity Parathyroid Hormone always wins even when it is detriment to skeleton stimulates osteoclast activity to resorb bone Sex hormones dramatically accelerate bone growth stimulate osteoblasts at Epiphyseal growth plate HOWEVER at puberty signal EP closure Glucocorticoids quotstress hormones produces by adrenal gland normal levels no effect but if chronically high increase bone resorptionloss of bone mass when the levels are chronically high What does Vitamin A C and D do Vitamin A accelerates osteoblasts Vitamin c required for normal cartilage synthesis Vitamin D stimulates absorption and transport of Ca and P ions into the blood What are the effects of exercise How does a bone gain strength Stress in the form of exercise is required for bone remodelings and is needed to maintain bone growth A bone gains strength by increasing the amount of mineral salt deposition and collagen fibers synthesized which increases the mineralization What happens when a bone has a fracture A hematoma forms and capillaries invade the structure Then fibrocartilagous callus forms which is irregular and regular CT that is used as a template The bony callus forms trabecular bone that looks like woven bone and finally the bone is remodeled which can take around 3 4 months because osteoclasts remove excess bony material at both the external and internal surfaces compact bone replaces the primary bone What happens if cartilage is not contained in the bone The limb or whichever bone will not grow in length bc the epiphyseal plate is broken What are the 2 ways the aging effects the bones The tensile strength decreases reduced rate of protein synthesis leads to reduced production of organic portion of bone matrix and inorganic portion increases and the bone becomes 58 59 brittle Secondly the loss of Ca and other minerals result in demineralization thinner and weaker bone results from insufficient ossification osteopenia Discuss the imbalances of the bone With age bone becomes thinner and weaker The bone loss in men 3decade and bone loss in women 8decade it usually starts in 3050 year olds Osteopenia is the weakening of bones below normalon way to osteoporosis it refers to bone mineral density that is lower than the normal peak BMD measures the level of minerals in the bone which indicates how dense and strong they are Osteoporosis is a condition characterized by reduction in bone mass sufficient to compromise normal function Less bone is in osteoporosis but that doesn t mean it is necessarily bad bone What is pagets disease It is a chronic disorder that can result in enlarged and misshapen bones Paget39s is caused by the excessive breakdown and formation of bone followed by disorganized bone remodeling Chapter 9 Articulations 60 61 62 63 64 65 66 67 What are articulations A joint or place of contact that is between bones bones and cartilage or bones and teeth What is the relationship ofjoints and motion Joints can permit varied range of motion There is an inverse relationship that exists between a joints mobility and stability9the more moveable a joint is the less stable it is What is arthrology Study of joints Is this the strongest or weakest part of the skeleton Why Weakest because it is the most moveable How are joints classified Function amount of movement at a joint range of motion Structure organization of a joint material binding bones together and presenceabsence of joint cavity What is EDS disorder A group of inherited disorders that mostly affect the skin joints and blood vessels It is a disorder with hypermobility The functional classification ofjoints is synarthrotic amphiarthotic and diarthrotic what do all these imply about the joints Synathrotic immovable Amphiarthroticslightly moveable Diarthrotic freely moveable predominate in limbs Describe the characteristics of fibrous joints and name the 3 typesfunctions These are joined by fibrous tissue and have no joint cavity The amount of movement depends on fiber length Synarthrotic and amphiarthrotic make up the majority of these joints 3 types sutures articulating bone edges interdigitate by overlapping or interlocking very short CT fibers continuous with periosteum and penetrate bone An example synostoses fibrous tissue ossifies skull bones fuse together as a single unit Syndesmoses bone connected by ligament cord or band or fibrous tissue dense regular connective tissue fibers vary in length and it is considered amphiarthrotic An example 68 69 70 71 72 73 74 interosseous membraneligament articulating bones held sidebyside by a ligamentous sheet provides pivot point for bones to rotate against each other Gomphoses quotpeginsocket joint that articulated the teeth in bony alveolar socket Discuss cartilaginous joints and the 2 types of them Articulating bones united by cartilage and these also do not have a joint cavity 2 types synchondroses bar or plate of hyaline cartilage Symphyses articular cartilage fused to a pad or plate of fibrocartilage designed for strength with flexibility amphiarthrotic It resists compression and tension stressed and acts as a resilent shock absorber Discuss the synovial jointscharacteristicsdistinctive features These are articulating bones are separated by a fluidcontaining joint cavity separates articulating surfaces of bone amp are enclosed within a capsule These are the most abundant and provide the widest range of motion diarthrotic Articular capsule fibrous capsule that is continuous with periosteal The synovial membrane is loose CT covered incompletely with epithelial cell layer site of synovial fluid origination The joint synovial cavity filled with synovial fluid Synovial fluid blood filtrate viscous thins with the joint cavity weeping lubricationsynovial fluid comes out and releases itself It also contains phagocytic cells and provides nutrients Articular cartilage cushion lacks perichondrium Reinforcing ligamentsstrengthens and reinforces joint intrinsic and extrinsic What are accessoryjoint structures The types of them include bursae tendon sheath fat pads and tendons describe these Not part of the joint but it is closely related Bursae reduces friction flattened fibrous sacs with synovial membrane amp thin layer of synovial fluid tendon sheathin hand elongated and creates a friction free environment elongated bursa that wrap around tendon subjected to friction fat padsprotection distributed along periphery of synovial joint tendons dense regular CT that attaches muscle to bone How are skeletal muscles attached to bones origin and insertion Skeletal muscle is attached to bone or other structures by no fewer than 2 points origin muscle attached to immovable bone insertion muscle attached to movable bone How does movement of articulations happen Movement occurs when muscles contract across joints and insertion moves toward the origin can be in directional terms Describe the ranges of motion uniaxial movement movement in one plane biaxial movement movement in two planes multiaxial movement movement in multiple planes Describe the types of synovial joints and describe the functions of each Planar Joints Planar joints have bones with articulating surfaces that are flat or slightly curved These joints allow for gliding movements therefore the joints are sometimes referred to as gliding joints 75 The range of motion is limited and does not involve rotation Planar joints are found in the carpal bones in the hand and the tarsal bones of the foot as well as between vertebrae Hinge Joints In hinge joints the slightlyrounded end of one bone fits into the slightlyhollow end of the other bone In this way one bone moves while the other remains stationary similar to the hinge of a door The elbow is an example of a hinge joint The knee is sometimes classified as a modified hinge joint Pivot Joints Pivot joints consist of the rounded end of one bone fitting into a ring formed by the other bone This structure allows rotational movement as the rounded bone moves around its own axis An example of a pivot joint is the joint of the first and second vertebrae of the neck that allows the head to move back and forth The joint of the wrist that allows the palm of the hand to be turned up and down is also a pivot joint Condvloid Joints Condyloid joints consist of an ovalshaped end of one bone fitting into a similarly ovalshaped hollow of another bone This is also sometimes called an ellipsoidal joint This type of joint allows angular movement along two axes as seen in the joints of the wrist and fingers which can move both side to side and up and down Saddle Joints Each bone in a saddle joint resembles a saddle with concave and convex portions that fit together Saddle joints allow angular movements similar to condyloid joints but with a greater range of motion An example of a saddle joint is the thumb joint which can move back and forth and up and down it can move more freely than the wrist or fingers ndSocket Joints Ballandsocket joints possess a rounded balllike end of one bone fitting into a cuplike socket of another bone This organization allows the greatest range of motion as all movement types are possible in all directions Examples of ballandsocket joints are the shoulder and hip joints Know all of the types of movements gliding angular rotational and special movements Gliding royal wave simplest bone surface gliding or slipping over other surfaces it is also known as translation Angular movements flexion downward angle in anteriorposterior place bending movement usually along sagittal plane extensionupward angle in the anteriorposterior place straightening along the sagittal plane Hyperextension extension of joint beyond 180 degrees Lateral flexion trunk moves in coronal plane laterally away from the body mainly cervical and lumbar regions abduction movement of limb away from body line Adduction movement of limb to the body line Circumductionmovement of limb that describes a cone in space observe distal tip of limb moves in a circle while point of the cone is more or less stationary Extension Flexion Hyperextension Hyperextension Q Extension Extension a b c Lateral flexion Flexion Extension 1 e Abduction Adduction Action Adduction Abduction Adduction a b c Abduction Adduction d a b c E The McGrawHill Companies incPhoto by JW Ramsey 5 The McGrawHill Companies InclPhoto by Eric Wise Rotational movements rotation turning of bone around longitudinal axis can occur toward or away from midline Supinationpronation forearm with movement of radius around ulna supination radius and ulna are parallel and involves rotating arm laterally while pronation forearm rotates medially and distal radius crosses the ulna forming an x supinationmoving your palm up and pronationmove palm down Lateral nation IMeda retation a b g Medial rotation M Pronation Supination c d Rotation M a J Lateral rotation Special movements elevation and depression movement of body part superiorly with body part movement inferiorly Dorsiflexion plantar flexion movement of the foot at the ankle either up or down Protractionretraction nonangular anterior posterior movements in a horizontal place 76 77 Elevation Depression Plantar llexion J 1 Opposition of thumb and little finger I Inversion Eversion Retraction C d Opposite movement reposition lnversioneversion foot with sole moving medially or laterally Describe the tempromandibular joint and its characteristicsfunctionality It is small complex joint only moveable articulation between skull bones exhibits hinge gliding and some pivot joint movements Tempromandibular ligament Stabilizes the lateral side of the temporomandibular joint and helps prevent the mandible from dislocating when it is opened Stylomandibular ligament this helps the joint stay in place Sphenomandibular ligament It helps limit depression of the mandible and prevent dislocation when opening the mouth Discuss the knee joint and why it is comprised of quotthree joints It is the largestmost complexdiarthrotic joint It is made of 3 joints because there is a medial portionlateral portion patella because there is a place coming into contact with each other when the patella is articulating with the anterior portion of the femur 2 joints the meniscus divides the knee joint into lateral and medial compartments tibiofemoral and the patellofemoral The meniscus serves as cushioning and helps improvefit of bones which is important for the condyles that articulate with the tibia The wedges of the cartilage improve the fit in the meniscus Articular capsule not unified bc the patella is on the anterior part Dital end of the femur medial and lateral condyles Most superior portion of the tibia flat surfaces 78 79 80 81 Knee has constantly changing surfaces Extracapsular ligaments lies outside the knee joint lntracapsular ligaments lie inside the knee joint fibrocartilage wedge articular discs divides synovial cavity into 2 separate cavities improves fit suprapatellar bursa prepatellar bursa infrapatellar bursae fat pads decrease friction What are common joint injuries Sprains ligament reinforcing joint are stretched or torn cartilage injury tearing knee menisci growth plate fissures overuse damage of articular cartilage repair slow to not at all luxation bones forced out of alignmentsubluxation bursitisinflammation of bursa due to excessive stress a blow or friction tendonitisinflammation of tendon sheath What does inflammatory condition mean A localized protective response elicited by injury or destruction of tissues which serves to destroy dilute or wall off both the injurious agent and the injured tissue What is osteoarthritis and what happens when you have this Degenerative joint disease involves deterioration of articular cartilage at ends of bones muscles ligaments amp tendons holding joint together become weaker amp joint itself becomes deformed stiff amp painful The articular cartilage is lost eventually and the bone is left grinding against each other OA most often occurs at the ends of fingers thumbs neck knees amp hips Fingers neck hips and knees coxal bone and sacrum regions quotwear and tear arthritis What is Rheumatoid arthritis and how is it different from CA Chronic inflammato disease an autoimmune disez may occur at all ages but arises at 4050 affects more women 3X s than men early stages of RA include joint tenderness amp stiffness due to inflammation of synovial membrane cause is unknown pannus formation inflamed thickened synovial membrane erodes cartilage resulting in scar tissue formation connecting bone ends replacing tissue with another tissue loss of mobility and anyklosis occurs immobilized joint course of RA variable amp marked by flareups amp remissions arthritis is active and then goes to an inactive state other manifestations anemia osteoporosis muscle atrophy amp cardiovascular problems RA targets synovial membrane vs OA targets the articular cartilage No they are different diseases Rheumatoid arthritis is caused by inflammation in the lining of the joint Osteoarthritis is more like a wear process in which the cartilage in the joint fails to 82 83 84 85 withstand the loads placed on it Some inflammation does occur in osteoarthritis but it is not the same as that in rheumatoid arthritis Some wear may take place in damaged joints in rheumatoid arthritis but this is a late complication of the disease The two diseases are quite different in their treatment and it is important not to confuse the two Chapter 10 Muscle Tissue and Organization What is the muscle tissue responsible for Movement of the human body and the movement of materials within the throughout body What are the muscle tissues comprised of They are comprised of muscle fibers cells that exhibit specific characteristics What do muscle fibers exhibit a excitability i responsiveness ii reacts to various stimuli utilize changes in electrical charge across PM which signal internal events that lead to muscle contraction b contractility i stimulation of muscle tissue generates tension within cell c elasticity i contracted muscle recoils back to its resting length after the tension has been removed very important d extensibility i capacity to extend in length in response to contraction of opposing muscle What are the characteristics of skeletal muscle 0 striated elongated with peripherally located nuclei long cells which are usually the length of the muscle usually attaches to one or more bones varies widely in shape each muscle fiber runs the length of the muscle 00000 86 What are the functions of skeletal muscle tissue 0 body movement nervous system coordinates this 0 skeletal bones move when SkM contracts pull on tendons which are attached to the bone 0 highly coordinated movement is the result of the integrated functioning of muscles bones and joints 0 maintenance of posture postural muscles 0 specific SkM s stabilizes joints and help to maintain posture or body s position 0 temperature regulation 0 byproduct of muscle activity 0 maintains our normal body temperature 0 storage amp movement of materials o Sphincters skeletal permit you to eliminate wastes when it is convenient for you There are also muscular sphincters 0 support 0 arranged in sheets or layers which protect organs amp support their weight within the abdominal cavity 87 Describe the structure organization of the skeletal muscle 0 Skeletal muscle layers of muscle fibers blood vessels nerves amp CT sheets that surround muscle fibers and connect to bone tendon Deep Fasiadeep layers of the CT Epimysiumwraps around all the fascicles Perimysiumwrapes around a fascicle Endomysiumwraps around individual muscle fibers inside the fascicle 0000 0 Function provide protection bld vessel amp nerve distribution means to attach to skeleton o Neurovascular bundle body nerves arteries veins and lymphatics that tend to travel together in the body 88 What are the organizational levels of the skeletal muscle Smallest to largest order thick and thin filaments actin thin and myosin thick myofilaments myofibril each muscle fiber muscle fibermany myofibrils in a bundle that the endomysium is wrapped around fasicleswhat the perimysium wraps around musclewhat the epimysium wraps around all of these form to make the tendon and attach to the bone the deep fascia ensheathes wrapped muscle and serves as organizing and filling spaces between muscles and binding the muscles together 89 How are muscles attached By tendons at the end of a muscle where the CT elements merge to form a thickfibrous structure or by aponeurosis a tendon in the form of a thinflattened sheath 90 Where do the blood vessels and nerves extend through What is it called Epimysium and perimysium It is called a neurovascular bundle 91 What do the blood vessels do Blood vessels deliver nutrients and remove wastes 92 What are the blood vessels and nerves controlled by What makes them voluntary Controlled by nerves of Somatic Nervous System the motor neurons that stimulate muscle contractions by the axons This is caused by information flowing out And the neuromuscular junction is between the axon and the muscle ben 93 Discuss the microscopic anatomy of skeletal muscle SkM cells contain long cylindrical myofibrils that extend entire length of muscle fiber consist of bundles of short myofilaments During contraction myofibrils shorten as myofilaments change position since attachment at end of muscle fiber causes fiber to shorten SkM cells are multinucleate due to myoblasts fusing during embryonic development Some myoblasts do not fuse remain in adult SkM as satellite cells can be initiated to differentiate to assist in repairregeneration of injured SkM Skeletal muscle fibers have PM called the sarcolemma with sarcoplasm which is like the cytoplasm sarcoplasmic reticulum stores calcium T Tubules invaginations of the sarcolemma forming a tubular system inside the cell itself9 communication link occurs between these 2 called the Triad Terminal cist are an elaboration of the sarcoplasmic reticulum A motor neuron comes in and is associated with the sarcolemmahow do you get the info In the fiber The mechanism Use T Tubules bc Ca is the go signal for contraction by using the signal from the motor neuron9muscular junction9activate the sarcolemma and the signal flows through the T tubules releasing Ca After all this the myosin is activated and during contraction the signal causes the myofilaments to act with one another and change position by shortening their structures The neuromuscular junction is where the synaptic end bulb of a motor neuron meets the motor end plate on the sarcolemma of a muscle fiber 94 What filaments make up the myofilaments and what are the functions 0 MyosinThick filament myosin tails point toward center while the heads point toward the edges Thin filament subunit G actin polymerizes to form F actin These filaments overlap each other to a greater or lesser extentThe pattern of this overlap at rest is described by a number of specific zones and bands striations are due to size and density difference between thin amp thick filaments The regulatory proteins determine how strong the contraction will be 95 What is the organization of a sarcomere and explain the components Sarcomere functional contractile unit of SkM fiber defined as the distance between 2 2 lines Each myofibril contains multiple sarcomeres O O O O O A band contain entire thick filament some thin filament I band contains thin filament only H zone central region of A band lighter only thick filaments M line thin protein meshwork structure in center of H zone attachment site for thick filament amp keeps aligned during contraction 2 line thin protein structure attachment site for thin filaments connectin or titin impt in extension amp elasticity single strand of quot300 tightly folded domains molecular coiled spring 96 97 98 Sarcomere Thin lillament M line vov quot 39 39 v 00000 yo i oonn o39o39o39o o39o quot quot 39 39 quot 39 quot 39 Illo39o39o o39i 39 9 0390 o39o i o 39I 000000 o39o o39o390 3909 00000 gt LIJ Thick filament LIJ 2 disc Titin 2 disc band 5 A band 5 I band 5 C What is the sliding Filament Theory and what happens during it 0 Interaction between thick amp thin filaments cause muscle to contract 0 SFT states that as a muscle contracts the thin filaments slide past thick filaments and the sarcomere shortens 0 Observe A band remains constant but H zone disappears I bands narrows 2 lines move closer together in adjacent sarcomeres sarcomere narrows o gtThick amp thin filaments retain same length it is the relative position between them thatchanges Note the filaments themselves do not change in basic structure during a contraction but the amount of overlap between them does This whole process can be broken down into five phases a Resting Phase b ExcitationContraction Coupling Phase c Contraction Phase d Recharge Phase e Relaxation Phase What is a neuromuscularjunction and what does it do Muscle contractions begins when a nerve impulse traveling along a motor neuron stimulates a muscle fiber occurs at the neuromuscular junction Describe the physiology of muscle contraction Synaptic knob A nerve Impulse triggers release ol ACh trom the synaptic knob into 58m the synaptic clelt ACh binds to synaptic m8 ACh receptors in the motor end plate oi the neuromuscular mggnmsw39a39 anemic cleft Myoftbril junction initiating a muscle impulse in the sarcolemma ot the musde ber As the muscle impulse spreads quickly lrom the sarcolernma along Ttubules calcium ions are released from terminal cisternae into the sarcoplasm till we saw blocked When the impulse stops calcium ions are actively Calcium ion3 bind to troponin Troponin changes shape moving transponed into the sarcoplasmic reticulum tropomyosin on the actin to expose active sites on actin molecules tropomyosin recovers active sites and filaments ol thin laments Myosin heads 0 thick filaments attach to exposed passivety slide back to their relaxed state active sites to lorm crossbridges Thin filament Thidt filament Myosin heads pivot moving thin laments toward the sarcomere center ATP binds myosin heads and is broken down into ADP and P Myosin heads detach lrom thin laments and return to their preplvot The repeating cysts of attachpivordetach retum slides thick and thin filaments past one another The sarcomere shortens and the muscle contracts The cycle continues as long as calcium ions remain bound to troponin to keep active sites exposed 39 Axonal temlna39 Neurotransmitter released ditiuses across the synaptic cleft and attaches synaptic to ACh receptors on the sarcolemma cleft Sarcolemma T tubule 6 Action potential B along the sarcolemma ACh ACh ACh and down in C8 fl trom tenhlnai cisternae oi SR 39 39 3039squot C39squot 62 Tropomyosin blockage restored blocking actin Calcium ions bind to troponin active sitecontraction troponin changes shape removing ends and Ca the blocking action at tropomyosin muscle actin active sites exposed fiber relaxes Removal of Ca2 by active transport a into the SR after the action potential ends Caquot 39 39 Contraction myoeln cross bridges alternately attach to actin and detach pulling the actin filaments toward the center of the sarcomere release at energy by ATP hydrolysis powers the cycling process Copyright 13239 2004 Domain Educator Inc pubiuthng as Bengamm Cumming 0 Events of muscle contraction have been called quotexcitationcontraction coupling 0 stimulation of a muscle fiber by a nerve impulse results in a series of events that leads to muscle contraction o excitationcontraction coupling represented by steps 14 99 What are motor units What are they responsible for What makes motor units up How is it controlled 0 A motor unit is made up of a motor neuron and the skeletal muscle fibers innervated by that motor neuron39s axonal terminals Groups of motor units often work together to coordinate the contractions of a single muscle all of the motor units within a muscle are considered a motor pool 0 Although each muscle fiber has only one neuromuscular junction the axon of a motor neuron can branch off many times and form junctions with many different fibers 100 101 102 103 104 Therefore the single motor neuron branch and all the different fibers it innervates are collectively known as the motor unit This is an important principle of neuromuscular functioning for a few reasons which are summarized below a Fine vs Gross Motor Skills Fine movement small motor units Gross movements shaking your butt b quotAll Or Nonequot Principle force and precision are deepening on how many muscle fibers are being asked to be contracted c Factors of Muscle Tension Development A single motor neuron controls several muscle fibers within a muscle referred to as a motor unit Muscle fibers within a motor unit are not clustered but distributed within muscle A relationship exists between size of the motor unit amp degree of control with smaller motor units involved with finer movements A relationship exists between size of the motor unit amp degree of control with smaller motor units involved with finer movements Why are some motor units active even when a muscle is at rest Even in a relaxed state the muscle is slightly contracted bc it needs to keep itself firm healthy and ready to respond to simulation This represents the resting tension in a skeletal model How are motor units stimulated And what are the functions it serves motor units are stimulated randomly assists to stabilize position of bones stabilize joints amp maintain posture Discuss the differences between isometric and isotonic contractions isotonic muscle changes length and moves load isometric muscle neither shortenslengthens generates tension even if you are not physically moving something In general what does contraction refer to In general contraction refers to active process of generating force within a muscle by crossbridge activity does not mean muscle has to shorten What kind of muscle fibers make up the skeletal muscle What are their function Fiber Types 0 slow oxidative SO fibers suited for prolonged contractionswhen dominate in a muscle termed red muscle a lot of myoglobin they love oxygen and go through oxidative phosphorylation This can still be fatigues but it takes longer to happen 0 fast glycolytic F0 fibers fast twitchslow twitch that is easily fatigued 105 106 0 fast glycolytic FG fibers suited for rapid intense movementswhen dominate in a muscle termed white muscle low in myoglobin it uses glycolysis to generate ATP and it fatigues early on Most body muscles are a mixture of fiber types gives muscle a range of contraction speeds and varying resistance levels to fatigue A genetically determined feature What is muscle tension Muscle tension is the force exerted by a contracting muscle on some object while the weight reciprocal force exerted by object on the muscle is the load How is the skeletal muscle fiber organized Muscle fibers are bundled into fascicles which lie parallel to each other BUT fascicle organization in different muscles can vary muscle power varies think about direction of tension generation and number of muscle fibers contracting Copyright T McGrrM Hull EdJcaucn Pmrrussion leisured lot rcrcltfuctr1 039 fsg m39 Table 105 Skeletal Muscle Architecture Pattern of Muscle Fiber Description Example Circular Hhers arranged concentrically around an opening Functions as a sphincter to close a passageway or opening cg orbits mouth anus Orbicularis oris Parallel Fascicles are parallel in the long axis of the mmcle Body of muscle increases in diameter with contraction High endurance not very strong Be 6quot l Rectus abdominis Convergent 39l riangular muscle with common attachment site Direction of pull nl muscle can he changed Does not pull as hard as equalsited parallel mucle Pectoralis major l enmte Muscle body has one or rnure tendnm fascicles at oblique angle In tendon l ulls harder than 1 parallel muscle olequul site Unipermate All muscle bers on the some side nl the tendon Brpemmtc Muscle bers on both sides of the tendon Multimmmrr 39l39endon branches within the muscle Extensor digitorum Rectus lemons Deltoid uniponnate bipennato multipennate 107 What does location and nature of the muscle contraction to skeleton influence speed range and force of the movement 108 What is the relationship between the muscle contraction and skeletal element compared to What is this known as 109 110 111 112 113 114 a Firstclass lever T 39v 39r 3914 395 Iquot r 39 115 0 relationship between muscle contraction and skeletal element often compared to the mechanics of a lever which is known as biomechanics the practice of applying mechanical principles to biology What do the skeletal muscles involve Use of most skeletal muscles involves leverage and lever systems A lever is a rigid bar that moves on a fixed point fulcrum when a force is applied What are joints Fulcrums What are bones What is load 0 bones are levers with effort being provided by muscle contraction by applying to muscle s insertion point on bone 0 load is bone associated tissue and anything else you are trying to move What do levers allow the body to do 0 Levers allow a given effort to move a heavier load or to move a load farther or faster than it otherwise can What are the mechanical advantages and disadvantages of lever systems Mechanical disadvantage speed level this may be fast but the force is lost Advantage power lever useful for heavier load that is slow and stable First class levers oad and applied force are on opp sides of the fulcrum Only a few of these in the human body Few applied force AF amp resistance R on opposite sides of fulcrum F i 1 Resistance A Fulcrum MOVemem completed Second class levers oad and R is placed bw the fulcrum and force being generated power lever mechanical advantagelimited how much you can move Load is the weight baring down on the foot Few resistance located between AF and F small force can balance larger weight but slower amp short distance moved Effective force increased Movement completed b Secondclass lever 116 Third class levers speed and range of motion is a priority Most common levers Sacrifices the force that we generate Most common AF between F amp R have greater speed and increased distance but sacrifice effective force Movement completed c Thirdclass lever 117 How do skeletal muscles work Do they pull or push Skeletal muscles do not typically work in isolation rather they work together to produce movement Muscles pull not push 118 What are the 3 primary actions of skeletal muscle 0 prime moversagonistsmuscle provides major force 0 antagonistsoppose or reverse particular movement 0 synergistsaid agonists in directional of the pull of prime mover and gets rid of interference of what it is doing 0 a muscle can act as any of these depending on the movementthey can play diff parts the muscles 119 Discuss the characteristics of cardiac muscle a cardiac muscle cells are arranged in thick bundles within the heart wall b characteristics i fibers are striated but shorter and thicker ii 1 to 2 nuclei per cell iii large number of mitochondria 1 aerobic respiration c form Yshaped branch and join adjacent muscle fibers via intercalated discs made up of DESMOSOMES makes sure muscle cells don t pull apart AND GAP JXNS d auto rhythmic cardiac muscle cellscontract on their owninvoluntary bc don t need nervous system to tell them to move and they can do this bc of the GAP jxns 120 Discuss the characteristics of a smooth muscle a characteristics i short fusiform shape ii single centrally located nucleus iii nonstriated 1 thick amp thin filaments present but not precisely aligned no sarcomeres 2 thin filaments attached to dense bodies iv SR sparce Ttubules as well as 2 discs absent b contraction in SmM is slow resistant to fatigue amp sustained for extended periods of time c Thick filament and thin are attached to dense bodies attached to int filament that forms a network around the cell No restriction so you can contract more and smooth muscle scrunch bc of actin and myosin movements pull on dense bodies and those pull on the inter Filaments netting d involuntary i modulated by autonomic Nervous System Chapter 14 Nervous Tissue 121 What are the functions of the nervous tissue 0 Body s primary communication amp control system 0 Complex 0 Divided into structural and functional categories 122 What are the structure organization of the nervous system Based on anatomic components Subdivided into Central NS and Peripheral NS 123 What are 3 general functions of the nervous system a collect information via R s of PNS pass to CNS i sensory input receptors 124 125 126 b process amp evaluate information CNS determines what if any response c response to information CNS initiates PNS carries commands to effectors i motor output effectors Be able to understand the functional organization of the NS Functional Organization of the Nervous System Nervous system SGHSOI V nervous system Contains receptors Transmits information from receptors to the CNS I Motor nervous system Transmits information from CNS to the rest of the body Sends motor information to effectors Somatic sensory Visceral sensory Receives sensory information from skin fascia Receives sensory information from viscera Somatic motor Autonomic motor Voluntary Involuntary nervous system nervous system innervates innervates joints skeletal muscles special senses skeletal muscle cardiac muscle smooth muscle glands Describe the 2 cell types of nervous tissue and determine the functionality of each type a neurons i excitable cells that initiate and transmit nerve impulses ii basic functional unit b glial cells i nonexcitable cells that support amp protect neurons Discuss the characteristics of glial cells Also known as neuroglia found within both CNS amp PNS Differ from neurons tend to be smaller capable of mitosis Not excitable but do assist neurons in their functions Collectively protect amp nourish neurons provide an organized supporting framework for all nervous tissue Very little CT present Far outnumber neurons 127 128 129 130 neurons 131 How can glial cells be distinguished in the CNS and PNS table 144 Size intracellular organization and presence of specific cytoplasmic processes What are the type of glial cells in the PNS Astrocytes most abundant versatile Function perivascular feet cling to neurons amp capillaries brace amp anchor neurons to nutrient supply role in exchange between neurons amp vasculature bloodbrain barrier regulate tissue fluid composition brain IF structural framework cytoskeletal elements replacing damaged neurons this could be good but it is essentially replacing a functional neuron with a nonfunctional astrocyte neuronal development Satellite cells flattened cells arranged around neuron cell bodies in ganglia physically separate cell bodies from IF control chemical environment regulate exchange of nutrients amp wastes products between neuron amp environment Schwann cell also known as neurolemmocyte surround amp form myelin sheaths around PNS axons can act as phagocytes to remove dead cell debris impt in peripheral nerve fiber regeneration What are the type of glial cells in the CNS Ependymal cells epithelial cells varied shapes many ciliated line cavities of brain amp spinal cord slender processes branch extensively to make contact with other glial cells choroid plexus CSF production Microglia small cells with thorny processes which touch nearby neurons monitoring their health When activated transform into a type of macrophage to protect CNS from invading microbes amp dead neural tissue lmpt since immune system denied access Oligodendrocytes large cells with bulbous body and slender cytoplasmic processes that enshealthe portions of multiple axons myelin sheath What are neurons What are the function of neurons What are the characteristics of Basic structural unit of the NS Conduct nerve impulses from one part of body to another Display special characteristics high metabolic rates extreme longevity amitotic PM site of electrical signaling Discuss the neuron structure table 142 Neuron cell body also termed soma biosynthetic center of neuron Usual organelles but no centrioles Nissl bodies elaborate Golgi neurotubules amp neurofibrils extend into processes pigment inclusions these are either nuclei or ganglia Neuronal processes cytoplasmic extensions Dendrites short tapered amp diffusely branched represent receptive or input region provides large surface area for this purpose conduct electrical events toward soma Axon single arises from axon hillock represents conducting amp secretory component uniform diameter amp can be short or long in length collaterals branch at terminals telodendria and end with synaptic terminals synaptic knobs conduct electrical events away from soma Dendritic 39 spines r Direction of Dendrites II39 V39 J39 nerve impulse 5 A 4 quotinputquot l quot x ChromatophM g I pr 1 g I substances I l quot I l Nucleolus r J Nucleus f 39I N r body t 31 39 Direction 39 of nerve impulse quotoutputquot Axon Axon collateral Neurolemmocyte U Neurofibril node 39 s l Myelln sheath Telodendria Synaptic knobs gt Input gt Output 132 How are neurons classified Classified according to either structure or function Structural number of neuron processes unipolar bipolar multipolar Functional direction nerve impulse travels relative to CNS sensory motor interneuron 133 What is myelinated of axons Where does it occur What is impacted by the myelination Conduction of a nerve impulse is an electrical event along the PM Occurs as a result of a change in voltage across the PM of an axon Conduction of a nerve impulse is impacted by myelination 134 What is myelinated What are these advantages axon wrapped by a myelin sheathmyelin is a lipidprotein composite protective coating supports protects and insulates axon no change in voltage can occur in insulated region of axon Formed by Schwann cells amp oligodendrocytes 135 136 D Neurolemmocyte starts to wrap around a portion ol an axon r Axon Neurolemmocyte Neurolemmocyte cytoplasm and plasma membrane begin to term consecutive layers around axon The overlapping inner layers of the neuralemmocyte plasma membrane term the myelin sheath Otoplasm ol the neurolemmocyte Myelin sheath Eventually the neurolemmocyte cytoplasm and nucleus are pushed to the periphery ol the cell as the myelin sheath 395 termed 39 Myelin sheath Discuss myelination in oligodendocytes and Schwann cells Oligodendrocytes CNS can myelinate 1 mm sized portions on many axons whereas in the PNS an individual Schwann cell myelinates a 1 mm area on the axon What does myelination produce 137 138 139 Myelination produces faster nerve impulse conduction by salutatory conduction also know as quotnode jumping 9 is the propagation of action potentials along myelinated axons from one node of Ranvier to the next node Can axons be unmyelinated Not all axons are myelinated In PNS Schwann cells associate with axons but no myelin sheath is formed In CNS oligodendrocytes do not associate with axons Observe continuous conduction slower What are synapse What are the functions Axon terminals contact other neurons muscle cells or gland cells Involves a presynaptic amp postsynaptic neuron separated by a narrow space synaptic cleft9connection established between cell body process of presynaptic neuron to cell body process of postsynaptic neuron What are the 3 types of synapse Axonsomatic Axondendritic Axoaxonic don t get confused with anaaxonicneuron with dendrites and no axon no synapses where myelination occurs Copyright C hicGrmvHill Education Permission required for reproduclion or display Presynaplic neuron Poslsynaptlc neuron i I II I Dendrile Synaplic knobs Synapses at synapses k v 39 0 4 x f I 9 I Axon I a Synapse Cell body Axon Synapse i i a o b Simplified representation of a synapse N 23 Dendrites Axosomatic 39 Axodendrltlc synapse 394 synapse k e g nj Cell body quotquot Axon hillock A70quot Axoaxonic synapse V Telodendria c Types of synapses 140 Discuss the types of synaptic communication and compare them a electrical synapses i PM s of pre amp postsynaptic cells bound tightly together and gap junctions formed by connexons between both PM s ii no delay in passage of nerve impulse between cells iii Infrequent iv Info passes from one cell to the next local flow of currentmovement of a charged ion b chemical synapses i most numerous ii use of a NT iii synaptic delay chemical synapses most numerous involves very precise sequence of events once initiated rate of nerve impulse conduction can only be influenced by 2 factors axon diameter larger the diameterbetter the speed presenceabsence of myelin sheath eectrica synapse occurs in smooth and cardiac muscle for the most part The advantage of the electrical synapse is that it is a group of cells that can function as one unit bc the movement is so fast 141 What allows the NS to be able to coordinate and integrate nervous activity What are neuronal pools based on NS is able to coordinate amp integrate nervous activity because neurons are organized into complex patterns called neuronal pools circuit Neurona pools are based on function into 4 types of circuits converging diverging reverberating amp parallel afterdischarge Converging many inputs into a SINGLE output concentrating circuit strong stimulationinhibition coming out Diverging 1 input sends to 3 and out to 5 amplifies circuit amplifys single in many motor pathways Reverberating input input output input input input input go all the way through and then goes to output once it is started it doesn t stop until a inhibitory signal stops the flow or a synaptic fatigue happens neuron runs out of neuron transmitterslow levels rhythmic activities short term memory Parallel after discharge single output common the pathway of inputs are a burst of impulses When the input comes in it comes out like bang bang bang a burst complex thinking lnput Outputl t 1 Input 4 fw 3 l at 1 i 39Y39 1quot Input 7 K r I 339 5 l 4 In ut 39 39 I tx p I rquot i l npu A 3 T quotfr 39 39F39 39nPUt Input it 1 l gtv39 9 w 397 1quot a lOutput 39p Output l 1 Outputs 1 l a Converging b Diverging c Reverberating d F circuit circuit circuit 142 How are axons regenerated 143 144 145 146 PNS regeneration 1 amt of damage 2 secretion of nerve growth factors amp 3 distance between site of damage and effector organ really close to synapse there is likelihood of reconnection if it is far away 34 mm or less then the likelihood drops Neuron in the PNS synapsing with skeletal muscle fiber myelinated schwann cells neurolemma The schwann cells enhance the growth of the axon and have axonal sprouts to reest Connection When trauma happens the end of the axon seals itself and swells up anything distal to the injury degrades and is called Malaren degeneration We hope the endomysium stays intact along with the Schwann cells that can make a regeneration tube which allows the neuron to reconnect and make the synaptic connection There is a possibility to reestablish the connection in the PNS CNS regeneration very limited due to 1 no release of nerve growth factors the oligodendricytes spit out things when they hurt but there is no release to say im hurt 2 high cellular density tends to complicate regrowth amp 3 both astrocytes amp CT coverings may form scar tissue obstructs axon regrowth Astrocytes respond by replicating and fill in the space neuron isn t healed or replaced with a neuron and CT coverings form a glial scar Why is it anti regeneration It doesn t want to make a wrong connection What are nerves in the PNS and CNS cablelike bundle of parallel axons in the PNS It is referred to as a tract in the CNS in the PNS a collection of cell bodies is called ganglia and in the CNS it is called nucleus What are nerves surrounded by Surrounded by 3 consecutive CT wrappings endoneurium perineurium amp epineurium A nervetract is surrounded by CT layers Individual axon is wrapped on the endoneurium organize in a group fascicle and wrapping around a fascicle is called a perineurium Wrapping ENTIRE collection with an epineurium How are nerves classified Sensory motor or mixed Sensory PSN to CNS afferent Motor CNS out to the PSN efferent How does the chemical synapse occur Step 1 Neurotransmitter Synthesis There are two general classes of neurotransmitters large neuropeptides or smaller aminesamino acids The large peptides are synthesized in the cell body of the neuron and are transported to the synaptic terminal through the axon The smaller aminesamino acids can generally be synthesized at the presynaptic terminal itself Step 2 Neurotransmitter Packaging Once the neurotransmitters are synthesized they need to be put into small groups ready to be launched across the synaptic cleft The small groups of neurotransmitters are released into the synaptic cleft when they receive an order from Ca 2 ions to do so When the electrical signal reaches the presynaptic terminal it opens some channels in the membrane these are called voltage gated Ca 2 channels Once these channels are open calcium ions from the surrounding extracellular environment rush into the presynaptic terminal As the calcium ions encounter the vesicles the membrane of the vesicles fuse with the membrane of the presynaptic terminal right at the synaptic cleft As the vesicles fuse with the membrane the neurotransmitters are expelled into the synaptic cleft Step 4 Neurotransmitter Binding The neurotransmitters can now swim diffuse through the synaptic cleft until they reach the postsynaptic neuron The membrane of the postsynaptic neuron contains a few channels receptors that control how a neurotransmitter can be translated into an electrical signal Step 5 Stopping the Chemical Signal Once the chemical neurotransmitter signal has been translated into an electrical signal the postsynaptic receptors need to be cleared very quickly so that they can receive new transmitters from new signals otherwise you d end up with neurotransmitter traffic worse than any traffic you ve ever experienced on the freeway Some neurotransmitters will be degraded some will be transported back to the presynaptic terminal to be recycled and sometimes they are absorbed by the postsynaptic terminal Minimum To Remember In order to jump across two neurons the electrical signal needs to be converted into a chemical one then back into an electrical one Synaptic transmission is a 5 step process Synthesis of the chemical message Neurotransmitter synthesis Grouping of the chemical message Neurotransmitter packaging Release to the neurotransmitter Translating the chemical message back into an electrical one at the postsynaptic membrane Clearing of the postsynaptic receptors Electrical 7 39 Smooth synapse I 39 muscle cells 39 I i Presynaptic quot Postsynaptlc I l I ce cell Nerve Impulse I L w Axon of presynaptic neuron Gap junction Local current j quot 2 i m Mitochondria w A l Calcnum Microtubules 39 Ca2 Ions of cytoskeleton l H o o A quot l quotX I Voltageregulated r Synaptic vesicles calcium Ca2 v containing V J channel acetylcholine ACh Posmve quot Connexons Synaptic charged tons 39 cleft Inner surface Plasma membrane z 0 p39asma 2 embrane a Electrical synapse b Chemical synapse 147 How does excitation retraction coupling happen An action potential in the skeletal muscle cell is what triggers muscle cell contraction We have seen that calcium ions regulate whether or not contraction can occur Thus what is needed is a way to link muscle excitation the depolarization of the action potential to Ca release from the sarcoplasmic reticulum This link is known as excitationcontraction coupling Ttubules are tubeshaped invaginations of the sarcolemma skeletal muscle plasma membrane that penetrate throughout the muscle fiber The action potential in the muscle fiber is conducted into the interior of the muscle cell along the Ttubules The lumen of the Ttubule is continuous with the extracellular fluid and the membrane depolarization during an action potential occurs across the Ttubule membrane On either side of the Ttubule are swellings of the sarcoplasmic reticulum called lateral sacs The lateral sacs are in close apposition to the Ttubule Subsequent molecular studies have identified the feet as being part of the calcium channel protein in the membrane of the sarcoplasmic reticulum SR Ca channel Located in the Ttubule membrane closely associated with the foot of the SR Ca channel is the Ttubule voltage sensor The voltage sensor changes conformation in response to the depolarization of the action potential This conformational change is transmitted to the foot of the SR Ca channel causing it to open and allowing Ca release Note that this direct mechanical interaction between the Ttubule voltage sensor and the SR Ca channel is specific for excitationcontraction coupling in skeletal muscle 148 all Eaten terminal Sereellern ma muscle cell iplleeme membrane eeextyleheline eeeptur Sweetie ellle l t eeeteleheline meetylleltelirne Sa m la mic Aeetylehellneetereee retieulllum imueele eellll entleelaemie reticulum eeetyleheline ireleeeett item the extra terminal lairidle t teeeptere en the eateellemme en aetieh petntiel ie generated ehtl tretile dieturn the T tubule Ce ie telleeeee here the eereeeleemie retienlum in reeeenee te the change in eehege Cegt hinde trepeznin Greasebridges ferni between aetin anti myeein Aeetyleheliheetereee temeeee eeetyleheline hem the synaptic eleti E iiieat ie treneeerteel heel imte the eereepleerhie reticulum T Trepemyeein tiihtle eetiwe eitee en eetin eeueini the ereeeltni uge te dieteellt What is resting membrane potential The resting membrane potential of a neuron is about 70 mV mVmiivot this means that the inside of the neuron is 70 mV less than the outside At rest there are relatively more sodium ions outside the neuron and more potassium ions inside that neuron
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