Anatomy Exam 3 Completed Study Guide
Anatomy Exam 3 Completed Study Guide BSC 215
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This 26 page Study Guide was uploaded by Mallory Ivy on Monday November 23, 2015. The Study Guide belongs to BSC 215 at University of Alabama - Tuscaloosa taught by Dr. Jason Pienaar in Fall 2014. Since its upload, it has received 109 views. For similar materials see Human Anatomy and Physiology in Biological Sciences at University of Alabama - Tuscaloosa.
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Exam 3 Study Guide: Chapter 9 Study guide ■ What are synarthroses, amphiarthroses, and diarthroses? ■ Synarthroses allow no movement ■ Amphiarthroses allow some movement ■ Diarthroses freely movable ■ Which of the joint types (fibrous, cartilaginous, synovial) have a joint cavity? ■ Synovial joints ■ What are syndesmoses? How does the length of the ligament influence movability? ■ Syndesmoses bones connected by a ligament (band of fibrous tissue) ■ Short ligaments immovable/little movement (synarthroses/amphiarthroses) ■ Long ligament considerable movement (diarthroses) ■ Ex: Tibia and Fibula ■ What are gomphoses? ■ Peginsocket fibrous joint; periodontal ligament ■ Can you give me examples of synchondroses and sympheses? What kind of joint are they (from both a structural and functional perspective)? ■ Synchondroses hyaline cartilage connects bones (most are amphiarthroses) ■ Sympheses bones covered with articular (Hyaline) cartilage fused into intervening pad (fibrocartilage); amphiarthroses ■ What are the 5 basic characteristics of a synovial joint ■ Articular cartilage covers opposing bone surfaces ■ Joint Cavity ■ Articular capsule ■ Synovial fluid ■ Reinforcing ligaments ■ What are the two components of the articular capsule of a synovial joint? ■ Outer fibrous capsule of dense irregular CT ■ Synovial membrane of loose CT ■ Are synovial joints synarthroses, amphiarthroses, or diarthroses? ■ Diarthroses 1 ■ What are bursa and tendon sheaths? What is their main function? ■ Closely associated with synovial cavity; lubricating “bags” that reduce friction ■ Bursa sacs lined by synovial membrane (where structures rub together) ■ Tendon sheaths bursa surrounding tendon ■ What types of things can stabilize a joint? ■ Shape of articular surface ■ Ligaments ■ Muscle tone ■ Extracapsular joint ligaments stabilize knee capsule and prevent hyperextension ■ Can you distinguish between the 6 main types of synovial joint if given pictures? Could you identify which ones are most (or least) movable (the # of planes that they can move through?). ■ Plane joints (nonaxial) metacarpals ■ Hinge joints (uniaxial) knee and elbow ■ Pivot joints (uniaxial)neck and radioulnar joint ■ Condyloid joints (biaxial) wrist and knuckles ■ Saddle joints (biaxial)thumb ■ Ballandsocket joints (multiaxial) shoulder and hip ■ What are the 3 joints associated with the knee? ■ Femoropatellar joint plane joint between patella and bottom of femur ■ Patella glides along distal end of femur during movement ■ Tibiofemoral joints (lateral and medial) hinge joint between femoral condyles and menisci ■ Ligaments and menisci reduce rotation ■ Can you distinguish between the three types of arthritis (and what causes them)? ■ Osteoarthritis wear and tear destruction of articular cartilages; restriction of joint movement as exposed bone tissue thickens ■ Rheumatoid Arthritis autoimmune disease; immune system attacks your own tissue (may be triggered by bacteria). Causes synovial membrane inflammation, degradation of articular cartilage and ossification ■ Gouty Arthritis deposition of uric acid crystals into soft tissues of joints, 2 inflammation Chapter 10 Study guide ■ What are the main functions of muscles? ■ Major purpose convert chemical energy in ATP to mechanical energy of motion ■ Movement contribute to breathing, circulation, feeding, etc. Key in communication (speech, writing, nonverbal) ■ Stability maintain posture by preventing unwanted movements; stabilize joints ■ Antigravity muscles resist pull of gravity and keep us upright ■ Control of openings/passageways ■ Sphincters internal muscular rings that control the movement of food,bile, blood, etc. ■ Heat Production produce roughly 85% of body heat ■ Shivering small muscle contractions to produce body heat ■ Glycemic control regulation of blood glucose concentration ■ Know the connective tissues and fascicles of muscular tissue and their main functions (i.e. Endomysium, Perimysium, Epimysium, Fascia, fascicles) ■ Endomysium thin sleeve of loose CT surrounding each muscle fiber. Allows room for capillaries/nerve fibers to reach each muscle fiber ■ Provides extracellular chemical environment for the muscle fiber and its associated nerve ending ■ Perimysium slightly thicker layer of CT, surrounds fasicles (bundles of muscle fibers) ■ Carry larger nerves and blood vessels, stretch receptors ■ Epimysium fibrous sheath surrounding the entire muscle ■ Outer surface grades into fascia ■ Inner surface sends projections between fasicles to form perimysium ■ Fascia sheet of CT that separates neighboring muscles/muscle groups from each other and subcutaneous tissue 3 ■ Fascicles orientation determines strength of muscle and direction of its pull ■ Fusiform Biceps Brachii (thick center, strong) ■ Parallel rectus abdominus (ability to shorten) ■ Triangular Pectoralis Major (small, but strong) ■ Unipennate Palmar interosseous ■ Bipennate Rectus femoris ■ Multipennate Deltoid (Pennates = many fibers = most force) ■ Circular obicularis oculi (contraction constricts opening, some are smooth muscle) ■ What is the function of a tendon? What are aponeuroses, retinaculum? ■ Tendons connect muscle to bone ■ Collagen fibers in muscle continue into tendon, then into the perioseum and matrix of bone ■ Aponeurosis tendon is a broad, flat sheet (palmar aponeurosis) ■ Retinaculum CT band that tendons from separate muscles pass under ■ What s the difference between a direct and indirect attachment of skeletal muscle to bone? What s the difference between the origin and insertion of a muscle? In which direction do muscles contract (towards the origin or towards the insertion)? ■ Direct (fleshy) attachment little separation between muscle and bone; muscle seems to emerge directly from bone ■ Ex: margins of brachialis, lateral head of triceps brachii ■ Origin stationary end of muscle (doesn’t move) ■ Belly thick region between origin and insertion ■ Insertion bony attachment to moving/rotating end of muscle Four categories of muscle functional groups (depends on action): ■ Prime mover (agonist) produces most of the force (Ex: brachialis) ■ Synergist aids the prime mover (stabilizes nearby joint, modifies direction of movement) (Ex: biceps brachii) ■ Antagonist opposes the prime mover (relaxes to give prime mover control, prevents excessive movement/injury) (Ex: triceps brachii) ■ Fixator prevents movement of bone (Ex: rhomboids hold scapula in place) ■ Muscles contract toward the origin ■ Which nerves innervate the muscles of the head and the neck? Below the 4 neck? ■ Head and neck cranial nerves ■ Spinal nerves innervate muscles below the neck ■ What is compartment syndrome? What causes this syndrome? What are the effects of this syndrome? What are the treatments? (Page 317) ■ Compartment Syndrome mounting pressure on the muscles, nerves, and blood vessels triggers a sequence of degenerative events. If a blood vessel in a compartment is damaged, blood and tissue accumulate in the compartment (build pressure) ■ Fasciae (encloses muscle compartments) prevent compartment from expanding with increasing pressure, pressure obstructs blood flow ■ If ischemia (poor blood flow) persists more than 24 hours, nerves start to die. After 6 hours, muscles start to die ■ Nerves can regenerate if pressure is relieved, muscles can not ■ Compartment syndrome indicated by myoglobin in urine Treatment: immobilization of limb and fasciotomy (incision to relieve pressure) ■ What is a hernia? What are the causes? Know the 3 main types of hernias, their locations, and characteristics. (Page 343) ■ Hernia viscera protrudes through a weak point in the muscular wall of the abdominopelvic cavity ■ Inguinal hernia most common (rare in women), viscera enter inguinal canal or even the scrotum ■ Hiatal hernia stomach protrudes through diaphragm into thorax; in overweight people over 40 ■ Umbilical hernia viscera protrude through the navel ■ Be familiar with the most common athletic injuries to muscles (Page 374). Be able to “ diagnose ” each of them if given a description. What are some methods of prevention and treatment of muscle injuries? What is RICE? ■ Common injuries: ■ Compartment syndrome pressure in muscles, causes poor blood 5 ■ flow and nerve/muscle death ■ Shinsplints injury/pain in the crural region. Can be tendinitis of the tibialis posterior muscle, inflammation of the tibial periosteum, anterior compartment syndrome ■ Pulled hamstring ■ Tennis elbow ■ Pulled groin ■ Rotator cuff injury ■ RICE: Rest, ice, compression, elevation Chapter 11 Study guide ■ What are the five characteristics of muscle tissue? Which one is ONLY found in muscles? ■ Responsiveness (excitability) response to stimuli (Ex: neurotransmitter) ■ Conductivity local electrical charge triggers wave of excitation that travels along the muscle fiber ■ Contractility ability to shorten when stimulated (unique to muscles) ■ Extensibility ability to stretch (even past resting length) when relaxed ■ Elasticity ability to recoil after being stretched ■ What are the 3 types of connective tissue associated with skeletal muscle, and where are they found (e.g., around a muscle fiber …) ■ Endomysium wraps around individual muscle fibers (areolar and reticular CT) ■ Perimysium fibrous CT sheath that wraps around fascicles (groups of muscle fibers) ■ Epimysium dense irregular CT surrounding the entire muscle; continuous with tendons to facilitate bone movement ■ Be able to describe the following structures associated skeletal muscle: ■ sarcolemma muscle cell plasma membrane ■ sarcoplasm cytoplasm of skeletal muscle cell. Contains glycosomes (stored glycogen) and myoglobin (oxygenstoring pigment) ■ myofibril rodlike structure running parallel to length of muscle fiber ■ Has contractile elements of skeletal muscle ■ Organelles squeezed between myofibrils ■ A band dark striations running along myofibril ■ I band light striations alternating with Abands along myofibril ■ Z disc darker area in I band, contains proteins that anchor actin 6 ■ Sarcomere smallest contractile unit of muscle fiber; segment from zdisc to zdisc ■ Thick filament (myosin) runs along entire A band. Composed of myosin with a tail of wound up polypeptide chains and 2 expanded heads ■ Thin filament (actin) extend across I band into A band. Composed of actin with attachments for myosin heads ■ Troponin (and its three polypeptide subunits) ■ TnI binds actin ■ TnT binds tropomyosin ■ TnC binds calcium ions ■ Tropomyosin rod shaped protein spiraling around actin, blocks myosin binding sites ■ Sarcoplasmic reticulum sER surrounding each myofibril, longitudinal channels + cross channels at Aband and Iband ■ Junction (terminal cisternae)* Regulates intracellular calcium levels through storage and release ■ Terminal cisternae A band and I band junction ■ T tubule at Aband/Iband junction; sarcolemma penetrates muscle cell, forms triad with terminal cisternae ■ Conducts impulses from sarcolemma into cell interior to signal calcium release from terminal cisternae ■ What is a motor neuron and what is the point of its contact with muscle called? ■ Motor neuron cell bodies in brain/spinal cord that stimulate skeletal muscle cells; axons travel to muscle ■ Neuromuscular junction point of contact between motor neuron and muscle fiber ■ Which structures in the axon of a motor neuron contain neurotransmitter? ■ Synaptic vesicles house acetylcholine (ACh), a neurotransmitter ■ Which neurotransmitter is released from motor neurons to induce muscle contraction? ■ ACh released into synaptic cleft, trickles into junctional folds of sarcolemma motor end plate (contains ACh receptors) ■ What is the space ” between the axon of a motor neuron and the motor end plate called? ■ Synaptic cleft ■ Which structure folds to create the motor end plate? 7 ■ Sarcolemma ■ When a muscle is in ‘resting phase , the sarcolemma is polarized. Is this polarization from a more negative charge on the inside or outside of the cell? ■ inside ■ When acetylcholine binds its receptor, which cation moves into the muscle fiber? ■ Sodium (Na+) ■ How does movement of sodium ions into the muscle fiber relate to depolarization? What is depolarization? ■ inside cell becomes less negative ■ Describe in as much detail as possible the sequence of events leading to muscle contraction and relaxation (i.e. Excitation, ExcitationContraction coupling, Contraction, Relaxation). Start with the acetylcholine in synaptic vesicles in the axon of the motor neuron and go from there, being sure to identify structures, molecules, etc. that are essential for the process. The following things should make it into your answer at some point: axon terminal, acetlycholine, synaptic vesicle, synaptic cleft, acetylcholine receptor, Na+,Ca+2, sodium potassium pump, sarcolemma, sarcoplasmic reticulum, terminal cisternae, Ttubule, troponin (and its 3 subunits), Tropomyosin, ATP, ADP, actin, myosin, polarized, depolarizaiton, motor end plate. *Hint* The detail in the lecutre notes is sufficeient to answer any question that may appear on the exam! ■ Excitation nerve action potentials lead to muscle action potentials ■ Nerve signal opens voltagegated calcium channels in synaptic knob ■ Calcium stimulates exocytosis of ACh from synaptic vessels ■ ACh released into synaptic cleft, 2 bind to each receptor protein, opening Na+ and K+ channels ■ Na+ enters cell, inside of cell becomes less negative (depolarization), quick voltage change called endplate potential (EPP) ■ Excitationcontraction coupling events that link action potentials in sarcolemma to activation of myofilaments, preparing them to contract 8 ■ Action potential propagates down sarcolemma into Ttubule ■ Activates voltagesensitive receptors in sarcoplasmic reticulum, causes release of Ca2+ ■ Ca2+ binds troponin causing conformational change (which twists tropomyosin to expose myosin binding sites on actin) ■ Contraction muscle fiber develops tension, shortens. ■ Power stroke initiated when myosin binds actin and pulls it toward the sarcomere center ■ ATP binds myosin, detaching it from actin. ATP hydrolysis reloads myosin for next round ■ Relaxation muscle fiber returns to resting length. Nerve stimulation and ACh release stop, stimulation by ACh stops ■ AChE breaks down ACh fragments reabsorbed into synaptic knob ■ Ca2+ pumped back into SR by active transport ■ Tropomyosin reblocks active sites ■ How does Rigor Mortis occur? ■ Rigormortis hardening of muscles and stiffening of body (starts 34 hours after death) ■ Deteriorating Sarcoplasmic reticulum releases Ca2+, allowed to enter cytosol through deteriorating sarcolemma ■ Ca2+ activates myosinactin crossbridging ■ Muscle contracts, but cannot relax (relaxation requires ATP, no longer produced after death) ■ Fibers stay contracted until myofilaments start to decay ■ Peaks 12 hours postmordem, subsides over next 4860 hours ■ What is muscle tension? Load? ■ Tension force generated by contraction ■ Depends on actinmyosin interactions and muscle fiber lengths (depends on muscle’s length when stimulated) ■ Overly contracted at rest weak contraction results (thick filaments too close to Z discs, cannot slide) ■ Overly stretched before stimulation weak contraction results (small overlap of thick/thin doesn’t allow crossbridges to form) ■ Load force exerted on muscle by weight of object ■ How does muscle fiber length relate to muscle tension? ■ Longer fiber = less tension 9 ■ What is a motor unit? ■ a motor neuron and the skeletal muscle fibers innervated by that motor neuron’s axon terminals ■ What is muscle twitch? ■ Muscle twitch is response of a motor unit to a single action potential (rapid contraction, then relaxation) ■ What are the three periods associated with a muscle twitch? Are the durations of these three periods the same for all muscles? ■ Latent period excitationcontraction coupling (muscle tension increases, but no muscle movement) ■ Contraction period active crossbridges; if tension is large enough to overcome load, muscle shortens ■ Relaxation period reentry of Ca2+ into sarcoplasmic reticulum; cross bridges become inactive, muscle tension drops to zero ■ What is wave summation and how does it relate to how the frequency of muscle stimulation affects contraction? ■ Wave summation muscle exposed to two stimuli in rapid succession; 2nd contraction stronger than the 1st ■ If motor neurons increase firing rate, this increases force of muscle contraction ■ What is incomplete tetanus? Complete tetanus? Would you be able to recognize them on a graph? ■ Incomplete (unfused) tetanus sustained but “quivering” contraction in response to increased rate of muscle stimulation ■ small, quivering waves on graph ■ Complete (fused) tetanus maximum muscle tension yielding smooth contraction plateau (prolonged contraction leads to fatigue) ■ What is the threshold stimulus for muscle contraction? The maximum stimulus? How do these relate to how the strength of a stimulus affects contraction? ■ the threshold stimulus is the minimum voltage required to generate an action potential and produce a contraction. ■ The maximum stimulus = complete tetanus ■ the more increased the firing rate → increased forced of muscle ■ Differentiate between the two forms of isotonic contraction. ■ Isotonic contraction muscle length changes 10 ■ Concentric muscle shortens ■ Eccentric muscle lengthens ■ What is isometric contraction, and how does it differ from isotonic contraction? ■ Isometric contraction muscle length does not change ■ When load exceeds force, tension builds but muscle does not move ■ Does skeletal muscle store a lot of ATP? ■ Muscle stores only enough ATP for a few seconds of contractile activity ■ How does creatine phosphate replenish ATP in skeletal muscle? ■ Creatine phosphate is a highly energized molecule that provides a phosphate to ADP ■ Overall: Creatine phosphate + ADP > Creatine + ATP, uses Creatine kinase ■ What are the differences between anaerobic and aerobic metabolism? ■ Anaerobic Metabolism Glycolysis and lactic acid formation ■ Glucose obtained from blood or from muscle glycogen stores ■ Conversion of glucose to pyruvic acid yields ATP in the absence of oxygen ■ Pyruvic acid then converted to lactic acid ■ Aerobic Metabolism aerobic cellular respiration ■ Glucose taken from blood or from muscle glycogen stores ■ Conversion of glucose to pyruvic acid, which enters mitochondria to generate ATP ■ Processes in the mitochondria require oxygen ■ Which factors drive muscle fatigue? ■ Muscle fatigue inability of muscle to contract despite receiving stimuli ■ Cramps lack of ATP to drive detachment of myosin from actin ■ Aches accumulation of lactic acid (lowers pH) ■ If given various characteristics, could you distinguish between slow oxidative fibers and fast glycolytic fibers (Table 11.3)? ■ Slow oxidative fibers slow contraction and myosin ATPase activity, slow rate of fatigue (fatigue resistant) ■ Aerobic pathway of ATP synthesis ■ High myoglobin content, low glycogen storage ■ First recruitment order ■ Best suited for endurancerequiring activities (Marathons, etc.) ■ Structure: Small, red, many mitochondria and capillaries 11 ■ Fast glycolytic fibers high rate of fatigue, fast contraction speed and myosin ATPase activity ■ Anaerobic glycolysis pathway of ATP synthesis ■ Low myoglobin content, high glycogen storage ■ Third recruitment order ■ Best suited for shortterm, intense, powerful movements (throwing a punch, hitting a baseball, etc.) ■ Structure: large, white, few mitochondria or capillaries ■ How do aerobic exercise and resistance exercise differ in their effects on skeletal muscle tissue? ■ Aerobic (endurance) exercise Increases: ■ Capillaries surrounding muscle fibers ■ Number of mitochondria within muscle fibers ■ Synthesis of myoglobin within muscle fibers ■ Efficiency of muscle metabolism ■ Resistance exercise Increases: ■ Size of individual muscle fibers ■ dominal cavities (heart, lungs, stomach, bladder) ■ Motor (efferent) division carries signals from CNS to gland/muscle cells that carry out response ■ cells/organs that respond to signals from CNS ■ Somatic Motor carries signals to skeletal muscles ■ Output causes muscle contraction as well as somatic reflexes (involuntary muscle contractions) ■ Visceral Motor (autonomic) carries signals to glands, cardiac/smooth muscle ■ Visceral reflexes involuntary responses ■ Sympathetic arouses body for action (accelerates heartbeat/respiration, inhibits digestion) ■ Parasympathetic calming effect, slows heart/breathing, increases digestion/urinary tract Chapter 12 ■ Know the 3 basic steps of nervous system function. ■ Sensory input sensory organs receive information about changes in the 12 body and external environment, transmit coded messages to spinal cord and brain ■ Integration Brain and spinal cord process information, relate it to past experiences, and determine appropriate response for situation ■ Motor output Brain and spinal cord issue commands to muscles and gland cells to carry out response ■ Know the anatomical subdivisions of the nervous system ■ Central Nervous system (CNS) brain and spinal cord enclosed in bony coverings (cranium and vertebral column) ■ Peripheral Nervous system (PNS) composed of nerves and ganglia (everything except brain/spinal cord) ■ Nerve bundle of axons (nerve fibers) wrapped in fibrous CT ■ Ganglion knotlike swelling in a nerve where neuron cell bodies are concentrated ■ Distinguish between the central and peripheral nervous systems. ■ CNS brain and spinal cordc ■ PNS sensory and motor subdivisons ■ Sensory (afferent) division carries sensory signals to CNS, informs CNS ■ Somatic sensory carries signals from receptors in skin, muscles, joints, bones ■ Visceral sensory carries signals from viscera of thoracic and abdominal cavities (heart, lungs, stomach, bladder) ■ Motor (efferent) division carries signals from CNS to gland/muscle cells that carry out response ■ ells/organs that respond to signals from CNS ■ Somatic Motor carries signals to skeletal muscles ■ Output causes muscle contraction as well as somatic reflexes (involuntary muscle contractions) ■ Visceral Motor (autonomic) carries signals to glands, cardiac/smooth muscle ■ Visceral reflexes involuntary responses ■ Sympathetic arouses body for action (accelerates heartbeat/respiration, inhibits digestion) ■ Parasympathetic calming effect, slows heart/breathing, increases digestion/urinary tract ■ Within the peripheral nervous system, what distinguishes sensory 13 (afferent) and motor (efferent) pathways? ■ afferent sends signals to the CNS ■ efferent carries signals away from CNS ■ Within the sensory (afferent) division, what distinguishes the visceral from the somatic division? ■ where they carry signals from: ■ Somatic from the skin, muscles, bones,& joints ■ Visceral from the viscera of the thoracic & abdominal cavities (heart, lungs, stomach, & urinary bladder) ■ Within the motor (efferent) pathway, what distinguishes the visceral from the somatic division? ■ Somatic carries signals to skeletal muscles ■ Visceral carries signals to glands, cardiac muscle, & smooth muscle ■ Within the visceral motor division, what distinguishes the sympathetic and parasympathetic divisions? ■ Sympathetic → arouses for action, accelerating heart beat ■ Parasympathetic → tends to have a calming effect, slows heart rate Section 12.2 Read ALL ■ Understand the parts of a neuron for describing neuron function. Save detailed identification of neuron structures for the lab. ■ What is the ‘contro l center for the neuron? ■ cell body the Soma ■ What is the function of the dendrites? ■ receive signals/ convey incoming signals toward the cell body (graded potentials) ■ What is the function of the axon? ■ send signals ■ Do you know the function of the axon hillock, terminal branches, and axon terminals of an axon? 14 ■ Where are neurotransmitters concentrated? ■ ganglion ■ isn’t it the synaptic knobs? ■ Describe three functional properties found in all neurons. ■ Excitability (irritability) response to stimuli ■ Conductivity production/communication through electrical signals ■ Secretion when signal reaches end of nerve, neurotransmitter ■ Define the three most basic functional classes of neurons. ■ Sensory (afferent) neurons detect stimuli, transmit info to CNS ■ Begin in almost every organ of the body, end in CNS ■ Afferent= direct signals to CNS ■ Interneurons (association) lie only in CNS, 90% of all neurons ■ Receive signals, carry out integrative function ■ Process, store info to “make decisions” ■ Interconnect incoming sensory pathways and outgoing motor pathways of CNS ■ Motor (efferent) neurons effectors send signals to muscle/gland cells ■ Efferent= conduct signals away from CNS ■ Can you distinguish between multipolar, bipolar, unipolar, and anaxonic neurons? ■ Multipolar → one axon multiple dendrites, most common, most in brain and spinal cord ■ Bipolar → on axon one dendrite, olfactory cells, retina, inner ear ■ Unipolar → single process leading away from soma, sensory from skin and organs to spinal cord ■ anaxonic → many dendrites no axon, help in visual processes ■ Can axons synthesize proteins? Why not? Where (and how) do they get their necessary proteins? ■ NO ■ Rely on cell body to synthesize proteins ■ Axonal transport twoway movement of proteins, organelles along the axon ■ Explain how neurons transport materials between the cell body and 15 tips of the axon (axonal transport). ■ Microtubules guide materials along axon ■ Kinesin → anterograde transport ■ Dynein → retrograde transport Section 12.3 Read ALL ■ Use table 12.1 to know and understand the 6 neuroglial cell types and basic function. Know whether they are found in the PNS or CNS. ■ Astrocytes CNS: ■ Anchor neurons to capillaries ■ Facilitate neuronal migration ■ Assist in synapse formation ■ Recycle neurotransmitters ■ Can release neurotransmitters ■ Influence neuron function ■ Microglia CNS ■ Monitor neuron health ■ Detect microorganism presence ■ Detect cell death ■ Transform into phagocytic cells ■ Ependymal Cells CNS ■ Line cavities of brain, spinal cord ■ Produce CSF ■ Permeable barrier between CSF and CNS cells ■ Oligodendrocytes CNS ■ Wrap neuron fibers ■ Responsible for myelin sheath ■ Schwann Cells PNS ■ "neurilemmocytes" ■ Form myelin sheaths around ■ nerve fibers of PNS ■ Assist in PNS neuron regeneration ■ Satellite Cells PNS ■ Envelop neuron cell bodies ■ Provide electrical insulation around the soma 16 ■ Describe the myelin sheath that is found around certain nerve fibers and explain its importance in speed of nerve signals. What are internodes and nodes of Ranvier? ■ the myelin sheath around the nerve fibers acts as insulation to the nerve and also as a way to help the signal travel faster down the nerve. ■ the node of Ranvier are the spaces between the myelin sheaths where they don’t connect ■ How does the conduction of nervous impulses relate to axon diameter? ■ nerve impulses travel along surface of a fiber, larger fibers have more surface area and conduct signals more rapidly ■ How is does myelination differ in PNS versus CNS neurons? ■ Schwann cells (PNS) indent to receive axon and then wrap tightly around a single axon, adjacent schwann cells don’t touch and have node of ranvier ■ Myelination in CNS by oligodendrocytes, can coil around MANY neurons simultaneously, Nodes of Ranvier are more spaced out ■ Explain how damaged nerve fibers regenerate. Which nerve fibers can regenerate: CNS, PNS, both? ■ The damaged nerve can only regenerate if the soma is intact and at least some neurliemma remains. ■ macrophages clean up tissue debris at the point of injury and beyond ■ soma swells, ER breaks up, and nucleus moves off center ■ axon stump sprouts multiple growth processes ■ Regeneration tube guides the growing sprout back to the original target cells and reestablishes synaptic contact ■ nucleus returns to normal shape ■ This ONLY happens in PNS, cannot occur in CNS Section 12.4 Read ALL ■ Explain why a cell has an electrical charge difference (voltage) across its membrane. ■ There is an unequal electrolyte distribution between extracellular fluid and intracellular fluid ■ What is the resting membrane potential? 17 ■ charge difference across the plasma membrane ■ Describe how K+, Na+, and Na+K+ pumps maintain the resting membrane potential. ■ K+ : plasma membrane is more permeable to K+ than any other ion ■ Leaks out until electrical charge of cytoplasmic anions attract it back in and equilibrium is reached and net diffusion of K+ stops ■ Na+ : some leaks and diffuses into the cell down its concentration gradient ■ Resting membrane is much less permeable to Na+ than to K+ ■ What is a Local potential local disturbance in membrane potential (acts over short distances) ■ What are the four differences between a local potential and an action potential? ■ Graded: vary in magnitude with stimulus strength ■ Decremental: get weaker the farther they spread from the point of stimulation ■ Reversible: when stimulation ceases, K+ diffusion out of cell returns the cell to its normal resting potential ■ Either excitatory/inhibitory: some neurotransmitters make it the membrane potential more negative hyperpolarize it so it becomes less sensitive and less likely to produce an action potential ■ Define depolarization. Can you recognize depolarization if given a graph showing changes in membrane potentials? ■ Case in which membrane voltage shifts to a less negative value ■ Define hyperpolarization. Can you recognize hyperpolarization if given a graph showing changes in membrane potentials? ■ a shift in a membrane voltage to a value that is more negative than the resting membrane potential ■ What is an action potential? ■ more dramatic change produced by voltageregulated ion gates in the plasma membrane ■ Can you label the major phases of the action potential on a graph? (resting, 18 depolarization, repolarization, and hyperpolarization) ■ Describe in detail how an action potential is generated, including where on the neuron it typically begins, and the roles of voltagegated sodium channels, depolarization threshold, membrane permeability, voltagegated potassium channels, and the sodiumpotassium pump. (the lecture notes may be useful for this, as it is summarized on slides 4647) ■ Trigger zone: where action potential is generated ■ If excitatory local potential spreads all the way to the trigger zone and is still strong enough when it arrives, it can open these gates and generate an action potential ■ On graph: Depolarization > Action potential (peak) > Repolarization > Hyperpolarization (dip) > Resting ■ Actual process: Resting: all channels closed membrane (axon hillock) depolarized by local currents → Na+ channels open and Na+ pours into cell membrane becomes more depolarized, more VGNa+ channels open causing even more depolarization → once depolarization reaches threshold (55 mV), more VGNa+ channels open depolarization VGNa+ channels are open → membrane permeability to Na+ has skyrocketed and membrane potential overshoots to +30 mV (all in 1 millisecond) inactivation gates of Na+ close after about 1 19 millisecond permeability to Na+ decreases potential “spike” rising → VGK+ channels open and K+ pours cell (along its gradient) inside neuron becomes more negative = repolarization while for VGK+ channels to close, resulting in hyperpolarization sodiumpotassium pump restores ion distribution across neuron membrane resting ■ In which direction does an action potential propagate in a neuron? Why? ■ It travels down the axon because the purpose of it is to release neurotransmitters that signal another cell, located at the axon terminal of the neuron ■ Why are action potentials “allornone ” phenomena? ■ If threshold is reached → action potential ■ If threshold is NOT reached → no action potential ■ The action potential does not get weaker ■ The action potential goes to completion and it cannot be stopped ■ What are the absolute refractory period and relative refractory period, and how do these limit how quickly a neuron can fire another action potential? ■ Absolute no stimulus of any strength will trigger AP, as long as Na gates are open ■ From AP to RMP Relative only especially strong stimulus will trigger new AP ■ How does the conduction of nervous impulses relate to myelination? Can 20 you describe salutatory conduction of nervous impulses? ■ Myelination = faster diffusion ■ Saltatory Conduction nerve signal seems to jump from node to node (AP are sometimes called these) Section 12.5 Read ALL ■ What are presynaptic and postsynaptic neurons? i. The first neuron in the signal path = presynpatic neuron (releases neurotransmitter); may synapse with a dendrite, soma, or axon of postsynaptic neuron to form axodendrite, axosomatic, or axoaxonic synapses ii. Second neuron = postsynaptic neuron (responds to neurotransmitter) i. What is a neurotransmitter; what is a synaptic cleft? i. Synaptic cleft: fluidfilled space between presynaptic and postsynaptic neurons ii. Neurotransmittersynthesized by the presynaptic neuron i. released in response to stimulation ii. bind to specific receptors on the postsynaptic cell iii. alter the physiology of that cell ii. Differentiate between axodendritic, axosomatic, and axoaxonic synapses. iii. Presynaptic neuron may synapse with a dendrite, soma, or axon of postsynaptic neuron to to form: i. Axodendritic Synapse: axon of pre to dendrites of post ii. Axosomatic Synapse: axon of pre to soma of post iii. Axoaxonic Synapse: axon of pre to axon of post ii. Know the steps of an excitatory cholinergic synapse and the neurotransmitter involved. i. Cholinergic synapse: employs acetylcholine (ACh) as its neurotransmitter; ACh excites some postsynaptic cells (Skeletal muscle) i. arrival of nerve signal opens voltagegated Ca2+ channels ii. Ca2+ enters knob and triggers release of ACh (exocytosis) iii. empty vesicles reload ACh 21 iv. ACh diffuses into synaptic cleft and bind to ligandgated channels on the postsynaptic neuron (Na+ enters cell, K+ leaves) v. As Na+ enters, depolarization occurs creating a local potential called the postsynaptic potential iv. Know the steps of an inhibitory GABAergic synapse and the neurotransmitter involved. i. Cholinergic synapse: employs acetylcholine (ACh) as its neurotransmitter; ACh excites some postsynaptic cells (Skeletal muscle) vi. arrival of nerve signal opens voltagegated Ca2+ channels vii. Ca2+ enters knob and triggers release of ACh (exocytosis) viii. empty vesicles reload ACh ix. ACh diffuses into synaptic cleft and bind to ligandgated channels on the postsynaptic neuron (Na+ enters cell, K+ leaves) x. As Na+ enters, depolarization occurs creating a local potential called the postsynaptic potential v. Know the steps of an excitatory adrenergic synapse and the neurotransmitter involved. What are 3 effects of this synapse? i. the unstimulated norepinephrine (NE) receptor is bound to a G protein ii. binding of NE to the receptor causes G protein to dissociate iii. G protein binds and activates adenylate cyclase to convert ATP to cAMP iv. Three effects: Can produce a ligand that binds and opens ion channel (Na+) from the inside= depolarizes the cell v. enzyme activation that leads to metabolic changes vi. Genetic transcription= new enzymes for metabolic functions vii What is the first step of stopping a synaptic signal? The second step involves 3 possibilities, know them. vii. Step one: Stop adding neurotransmitter viii. Step two: Get rid of neurotransmitter already there 1. Diffusion 2. Reuptake 3. Degradion in the synaptic cleft 22 Chapter 13 Required Reading and study guide 13.1 ■ Know the 4 principal functions of the spinal cord. ■ Conduction: nerve fibers that conduct information up and down the cord, connecting different levels of the trunk with each other and the brain ■ Neural integration: input from multiple sources, integrated, and executed output ■ Locomotion: repetitive, coordinated contractions of several muscle groups in the limbs ■ Reflexes: involuntary stereotyped responses to stimuli 13.3 ■ Define reflex and explain how reflexes differ from other motor actions. ■ Reflexes: involuntary stereotyped responses of glands or muscle to stimulation ■ automatic responses to sensory input that occur with or without intent or our awareness ■ What are the four important properties of a reflex? 23 ■ Reflexes require stimulation: not spontaneous actions, but responses to sensory input ■ Reflexes are quick: involve few if any interneurons and minimum synaptic delay ■ Reflexes are involuntary: occur without intent and difficult to suppress; automatic response ■ Reflexes are stereotyped: occur essentially the same way every time ■ Describe the general components of a typical reflex arc. ■ Pathway of arc: ■ somatic receptors: in skin, muscles, and tendons ■ afferent nerve fibers: carry information from receptors to posterior horn of spinal cord or the brainstem ■ integrating center: a point of synaptic contact between neurons in grey matter of spinal cord or brainstem; determines whether efferent neurons issue signals to muscles ■ efferent nerve fibers: carry motor impulses to skeletal muscle ■ effectors: the somatic effectors carry out the response ■ Describe the parts of a muscle spindle and their function. ■ Muscle spindles: stretch receptors embedded in skeletal muscles (inform the brain of muscle length and body movement) ■ Parts: ■ Intrafusal fibers: muscle fibers within the spindle (informs brain of muscle length, and speed of change in length ■ Extrafusal fibers: all other “normal” muscle fibers doing work ■ Nerve fibers: ■ 1) Primary afferent fiber: sensitive to small changes in length ■ 2) Secondary afferent fiber: inform brain of length 24 ■ 3) Gamma motor neurons: adjust sensitivity of the spindle ■ Describe the Stretch reflex and its basic function. Is it mediated primarily by the brain or spinal cord? ■ Stretch reflex: when a muscle is stretched, it “fights back” and contracts, maintaining increased tonus and making is stiffer than unstretched muscle ■ Helps maintain equilibrium and posture (EX: head starts to tilt as you fall asleep, muscles contract to lift head) ■ Mediated primarily by the brain ■ Know the 7 steps of the tendon reflex (Figure 13.21). Is it mediated by the brain or spinal cord? ■ 1) Tap on patellar ligament excites nerve endings of muscle spindle in quadriceps femoris ■ 2) Stretch signals travel to spinal cord via primary afferent fiber and dorsal root ■ 3) Primary afferent neuron stimulates alpha motor neuron in spinal cord ■ 4) Efferent signals in alpha motor nerve fiber stimulate quadriceps to contract, producing knee jerk ■ 5) At the same time, a branch of the afferent nerve fiber stimulates inhibitory motor neuron in spinal cord ■ 6) That neuron inhibits alpha motor neuron that supplies hamstring muscles ■ 7) Hamstring contraction is inhibited so hamstrings (knee flexors) do not antagonize quadriceps (knee extensors) ■ Mediated by: spinal cord byby: spinal cord prim ■ How do monosynaptic reflex arcs and reciprocal inhibition contribute to reflexes? ■ Knee is a monosynaptic reflex, one synapse between the afferent and efferent neurons. Reciprocal inhibition is a reflex phenomenon that prevents muscles from working against each other by inhibiting the antagonist. ■ Understand Flexor and crossed extension reflexes and how they work together (see text and Figure 13.22). Are they mediated by the brain or spinal cord? 25 ■ Flexor reflex: the quick contraction of flexor muscles resulting in withdrawal of limb from an injurious stimulus ■ Crossed extension reflex: contraction of extensor muscles in limb opposite of the one that is withdrawn ■ Together: CER maintain balance by extending other leg ■ Ex: when you step on a broken glass you move your foot (flexor reflex) and your weight is on the other leg (crossed extension reflex) ■ Understand the basics of the tendon reflex ■ A tendon reflex is in response to excessive tension on the tendon ■ Inhibits muscle from contracting strongly ■ Moderates muscle contraction before it tears a tendon or pulls it loose from the muscle of bone 26
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