week7.pdf EXSC 223 001
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This 5 page Class Notes was uploaded by Chase Heffron on Friday October 16, 2015. The Class Notes belongs to EXSC 223 001 at University of South Carolina taught by Thompson in Summer 2015. Since its upload, it has received 33 views. For similar materials see Anatomy and Physiology 1 in Physical Education at University of South Carolina.
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Date Created: 10/16/15
At the epiphyseal plate or growth plate there is more hyaline cartilage Growth occurs at the epiphyseal plate In the uppermost region of the growth plate is the growth zone In this zone there are chondroblasts dividing and laying down new cartilage At the other end of the growth plate there is the ossi cation zone Here all the cartilage is replaced with new bone In the middle there are two zone There is the hvpertrophic zone This is where cartilage cells chondrocytes become stressed They don39t have easy access to nutrients So they get larger hypertrophy and enter apoptosis programed cell death After hypertrophy they secrete calcium which triggers their death In this kind of bone growth the diaphysis gets longer and larger Growth hormone hormone that regulates bone growth This hormone does not work well unless another hormone thvroid hormone is secreted These hormones regulate growth at the growth plate Once the epiphyseal plate seals bone no longer grows longer but it can grow thicker or get thinner This is called remodeling This starts as soon as bones begin to form and continues until death Bone is taking away from some places but is added in others Bone is dynamic 57 of bone is mass is recycled each week Deposition the formation of new bone Osteoblasts are going to ll in a groove They come in and lay down osteoid collagen which provides the framework for the osteoblasts to mineralize and form new bone After collagen is laid down it takes about a week to become mineralized Deposition is occurring at all times It is greatest in bones that are stressed the most There are nutritional elements that affect this process Vitamin C promotes collagen synthesis Vitamin D promotes absorption of calcium in the gut Vitamin A serves as a balance between deposition and resorption Minerals such as calcium phosphorous and magnesium make up bone Resorption breakdown of bone matrix Osteoclasts secrete enzymes known as lysozymes and hydrochloric acid Enzymes break down the protein and the acid breaks down the minerals Bone remodeling regulation a negative feedback loop Two hormones regulate calcium in the blood When you increase the level of calcium in your body you trigger a hormonal response The thyroid gland secretes calcitonin Calcitonin39s primary function is to inhibit the parathyroid hormone Calcitonin also stimulates calcium salt deposit in bone By decreasing the activity of parathyroid hormone you favor deposition When calcium levels in the blood fall below the homeostasis level this triggers the parathyroid gland This gland secretes parathyroid hormone pth This is a potent hormone The parathyroid hormone stimulates osteoclasts This raises blood calcium levels back up Bone remodeling regulation part II mechanical stress In the bones that are being stressed you promote bone deposition Wolfs law bones grow or remodel according to the stress you place on it Part of the bone that receives the most stress remodels The compact and spongey bone will remodel Trabeculae adjust to absorb the most stress Bone Homeostatic Imbalances Osteomalacia rickets Often is a result of a vitamin D de ciency Without vitamin D not enough calcium is absorbed Collagen is laid down in bone but it does not mineralize well This makes the bones weak Osteoporosis Bone resorption is greater that deposit Osteoclast activity is greater than osteoblast activity Bone becomes much weaker Sex steroids effect strength of bone This is why women are more susceptible than men after they go through menopause Pagets disease Imbalance in the formation of spongey bone Lots of spongey bone is produced A lot of compact bone is replaced with spongey bone Not entirely clear what causes it This disease is localized it will only affect one or two bones Possibly due to a virus Muscular System Skeletal muscle multinucleated a bunch of cells that have formed together to form very large cells Some cells have 100 s of nuclei some have 100039s it depends on size Has striations The striations re ect the organization of the proteins within the bers Associated with a Movement b maintaining posture c Stabalize joints d Heat production e metabolism Cardiac muscle makes up heart involuntary Cardiac muscle cells have 1 to 4 nuclei Also has striations Function is to pump blood Cardiac muscle beats on its own This is because it s regulated by the autonomic nervous system Smooth muscle always mononucleated Does not have striations Found in blood vessels job is to maintain blood pressure Also found in the gastrointestinal tract Helps move food through your digestive system Skeletal muscle cont Skeletal muscle cell and skeletal muscle ber is interchangeable A muscle ber is a muscle cell Skeletal muscle and all other muscles come from the same layer of the embryo as connective tissue the mesoderm Myoblasts are the cells that will become muscle cells These are capable of cell division A myotube is something that occurs during development Myotubes are not capable of cell division They are multinucleated This is between myoblast and myo ber A myo ber is the matured muscle Somites are region within an embryo In the somites there are myoblasts Myoblasts are dividing As the myoblasts divide they start to bump up against one another This triggers changes in the myoblasts which results in the myoblasts fusing together When they fuse together they form a myotube A myotube is an immature muscle ber Myotubes can really contract or produce a meaningful amount of force For the myotube to become a myo ber a neuron must form a relationship with the myotube If the neuron forms a synapse with the myotube then the myotube will convert to a myo ber If a neuron does not form a synapse the myotube dies Muscle bers can grow or shrink Not all the myoblasts go away after maturity Extra myoblasts sit outside of muscle bers They can fuse to muscle bers and make the muscle get larger They can also help muscles heal when they or torn If you do not exercise your muscles will atrophy Muscles will get smaller and nuclei within muscle cells will die Wrapped around the outside of muscle is the epimysium These is a dense irregular connective tissue Separates different muscles lt ties to a tendon or helps the muscle attach to bone directly The primary job is to wrap around to form the whole muscle The next level or organization for a muscle is the fascicle Muscles contain multiple fascicles Muscles cont Any individual muscle such a bicep is considered an organ cause it consists of multiple different tissues Epimysium is the sheet of connective tissue that wraps around the muscle lt bundles smaller units called fascicles A fascicle consist of another layer of connective tissue that binds together multiple muscle bers The outer layer of a fascicle is the perimysium Typically what we consider 39meat39 is skeletal muscle When you slow cook food this causes the collagen bers to break down Connective tissue is what makes meat tough When you break down connective tissue meat becomes tender Fascicles bundle muscle bers together Muscle bers are the extremely long multinuclei cells Myo brils are organelles within muscle cells Muscle cells have many myo brils Myo brils run the length of the muscle cell Myo brils are unique in striated muscle It is the organization of the myo brils that create the striations A sarcomere is an anatomical unit within the myo bril It represents the smallest functional unit in muscle This is where contraction takes place There are many sarcomeres attached end to end on a myo bril The longer the muscle the more sarcomeres Sarcomeres are de ned by two boundaries Sarcomeres run from the Z M to the next Z disc The sarcomere consists of thick and thin proteins These laments are made up of proteins The thick laments are made up of a protein called myosin Myosin has globular heads These globular heads interact with proteins in the thin laments The primary protein in the thin laments is actin Light does not pass through the A band This is where the thick laments are Light does not pass through because there is more protein Light does pass through the l band This is because there is less protein The Zdiscs are dark bands rich in protein These are high stress points The thin laments are attached to the Zdisc The Zdisc is pulled on from both sides by the thin laments so it must be very strong There is another protein that attaches to the Zdisc It is called Titin attaches the Zdisc to the center of the sarcomere This is the largest protein in the body and it is very elastic At the center of the thick laments in the center of the sarcomere there is the M line The thick laments are xed in place by the M line Titin is anchored to the M line so titin runs from the Zdisc to the M line In a relaxed sarcomere the thin laments do not reach the M line On either side of the M line there is a space that has only thick lament This space is called the H m The H Zone is only thick laments In the A band stretches from one end of the thick lament to the other In the outer stretches of the A band thick and thin laments overlap at a ratio of 1 thick to 6 thin laments The globular heads of the thick laments interact with the thin laments These heads are made of myosin Myosin consists of distinct regions Myosin exists as a dimertwo proteins In the region of myosin called the tail you can see the 2 proteins wrapped around each other This region is what anchors the molecule into the thick lament Near the head is the hinge region of the myosin It is called the hinge because it moves The shape of myosin is regulated at the hinge The hinge exists in 2 positions cocked or uncocked The head is another region This sticks out The myosin head has an area that binds to actin This is called the actin binding site The globular head also has a binding site for ATP the ATP binding site Myosin is known as an ATPase Myosin is also an enzyme The thin lament is made up of small proteins called actin Actin forms a string like structure On each active site of actin there is a binding site for myosin Our body regulates how often myosin binds to actin There are two proteins that help regulate this Trooomvsosin interferes with myosin binding to actin The protein troponin is responsible for removing tropomyosin When your muscle is relaxed tropomyosin is covering up the binding sites When your muscle is contracted the sites are not covered The T tubule transverse tubule is part of the sarcolemma These tubules run all throughout the muscle In addition to myo brils within the muscle cell there is the sarcoolasmic reticulum SR The SR is really just the endoplasmic reticulum except that it stores calcium When it gets the signal it releases calcium into the cytosol Calcium left into a cell is bad so calcium must be regulated carefully The SR consists of regions The edge of the SR is the cistern The cistern is adjacent to the Ttubule This region is called the m This arrangement is critical to muscle contraction The triad communicates to release calcium into the cell