Week 9 CBIO 2200
Popular in Anatomy and Physiology I
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This 10 page Class Notes was uploaded by Bailey Dickinson on Thursday October 6, 2016. The Class Notes belongs to CBIO 2200 at 1 MDSS-SGSLM-Langley AFB Advanced Education in General Dentistry 12 Months taught by in Fall 2016. Since its upload, it has received 8 views. For similar materials see Anatomy and Physiology I in Cellular biology at 1 MDSS-SGSLM-Langley AFB Advanced Education in General Dentistry 12 Months.
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Date Created: 10/06/16
WEEK 9 NOTES (10/4-10/6) Your patient is a 26 year old gymnast who is complaining about muscle weakness in her face and arms. “My jaw gets tired when I’m eating” and it’s getting harder for me to “spot” my students in the gym. Electromyographic studies of the muscles in her arms reveal progressive weakness in decreased tension that develops during repeated muscle contraction You notice that her eyelids are droopy and have a sleepy appearance Three types of muscle Skeletal • Striated muscle, voluntary muscle • Muscles of movement Cardiac • Heart Smooth • Involuntary • Hollow organs, vessels, respiratory passages Skeletal muscle ^^ striated, multiple nuclei Each muscle fiber is as long as the muscle itself Cardiac muscle ^^ intercalated disc; the cells respond to electrical signals at the same time; can also be multi nucleated; fibers tend to be branched Smooth muscle^^ organized in sheets; contracts in a squeeze Back to the patient: What type of muscle tissue appears to be the source of the problem? Skeletal muscle Why do you think electrical studies of her muscle were conducted? Voluntary muscles; brain and muscles are connected; muscles are receiving signals- might be having an disuse with that; to see if the muscles are responding to the signals; skeletal muscle is electrically active tissue Functions of muscle tissue • Movement • Maintain posture/stabilize joints • Storage and movement of substances -Entrances and exits “guarded” by muscle sphincters • Generates heat • Support soft tissue Properties of muscle tissue • Excitability/Irritability -Responds to stimulus with an electrical signal that produces contraction • Contractility -Shortens forcibly • Extensibility -Can be stretched or extended • Elasticity -Returns to resting length Skeletal muscle > fascicle > muscle fiber > myofibrils Tendons: dense regular connective tissue You’re more likely to break the bone than to pull the tendon off of the bone Epimysium- covers the muscle Perimysium- covers the fascicle Endomysium- superficial to cell membrane- covers the muscle fiber Sarcoplasmic reticulum- stores calcium t-tubules- extensions of sarcolemma Thick filaments are surrounded by thin filaments Sarcomere: z-disc to z-disc A band is dArk I band is lIght Thick filament Thin filament- troponin (binding site for calcium) and tropomyacin regulate an active site on the active molecule Sliding Filament Theory • Thick filaments (myosin) form crossbridges with thin filaments • Thick filaments propel the thin filaments toward the center of the sarcomere • Thin filaments slide past the thick filaments, toward the M-line Contraction cycle • Events that occur in the myofibril/sarcomere • Interaction between thick and thin filaments For the active site to become active, Ca has to bind to troponin Why are the ends of the A bands the darkest region of the sarcomere when viewed under the light microscope? The ends of the A band have both thin and thick filaments. Myosin molecules have binding sites for what molecules? ATP and actin The ATP binding to myosin makes myosin’s affinity for actin less Myosin hydrolyzes ATP to ADP and Pi. We could call myosin a protein phosphatase What would happen if ATP were depleted in the muscle fiber? The cells die. The crossbridges form and don’t detach. Rigor mortis. Eventually the cross bridges detach because the proteins in the cells break down. Can use to help determine the time of death. What prevents the filaments from sliding back to their original position each time a myosin head releases? The myosin heads can release at staggered times and attach to other actin. What happens to the features of the sarcomere when skeletal muscles contract? M line is in the same spot. H zone, and I band are smaller in width. Z disks are closer together. The whole thing is darker. The A band doesn’t change size because the A band is the length of the thick filaments What tells the myofibril to shorten? • Electrical impulse from a neuron (a nerve cell in the central nervous system) • The neuron communicated with the muscle fiber chemically and the chemical signal is converted into an electrical signal • The signal in the muscle fiber causes Ca2+ release from the sarcoplasmic reticulum Action Potential • Electrical signal produced by ion movements • Nervous tissue and muscular tissue Sarcoplasmic reticulum is membrane bound and stores calcium Normally calcium is low in the cytoplasm. Need calcium to be increased in the cytosol so it can bind to troponin Sarcoplasmic reticulum and t-tubules = triad Calcium leaves the sarcoplasmic reticulum by facilitated diffusion because such a large amount of CA is on the inside as compared to the outside. Active transport pump puts the Calcium back in to the sarcoplasmic reticulum, or we wouldn’t be able to stop the contraction. As the length of the sarcomere decreases, tension increases (to a certain point) After that maximum tension point, as the length of the sarcomere is still decreasing, the tension decreases. Too much overlap of the myosin and actin; there’s nowhere left to go When the sarcomere is resting, it ahs more potential to develop tension (optimum length) When the sarcomere is too long, the myosin and actin cant attach because they aren’t overlapped Cardiac muscle is also striated so it has sarcomeres as well. We want this to happen in a forceful way so we can expel blood. Optimal length gives us a sufficient contraction.