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Bio 277 Unit 4

by: Elizabeth Weathers

Bio 277 Unit 4 BIO 277-01

Elizabeth Weathers

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These notes cover all the learning objectives for our iRAT tomorrow
Human Physiology
Elizabeth S. Tomlin
Class Notes
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This 5 page Class Notes was uploaded by Elizabeth Weathers on Tuesday September 20, 2016. The Class Notes belongs to BIO 277-01 at University of North Carolina - Greensboro taught by Elizabeth S. Tomlin in Fall 2016. Since its upload, it has received 88 views. For similar materials see Human Physiology in Biology at University of North Carolina - Greensboro.


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Date Created: 09/20/16
1. Describe the role of skeletal muscle in a homeostasis loop. Skeletal muscles are effector tissues controlled by somatic motor neurons 2. Compare and contrast the anatomy of smooth, skeletal and cardiac muscle. 3. Describe and draw the excitation­contraction coupling mechanism for both skeletal and smooth muscle. 4. Be able to explain how toxins and diseases can cause flaccid or tetanic paralysis, given their specific mode of action. Flaccid – prevents muscle contraction (toxin blocks Acetyl coA binding/prevents Acetyl coA release) Tetanic – keeps muscle contracted (toxin blocks Acetylcholinesterase) 5. Explain the relationship between cytosolic calcium levels and muscle contraction and relaxation. Higher levels of cytosolic calcium needed for contraction  voltage­gated protein changes shape, which opens calcium channel next to it & allows calcium out of cell  (calcium stored in Sarcolemic reticulum in muscle cell)  calcium ATPase pulls calcium back into cell to stop muscle contraction 6. For the actin­myosin crossbridge cycle, describe how ATP is used. The sliding filament theory describes how the hydrolysis (breaking apart) of ATP causes the myosin “heads” to flex  and pull the actin filaments closer to the center of a sarcomere to shorten the muscle. The only way that muscles  generate force is by shortening. 7. Describe the metabolic types of skeletal muscle and give their distinguishing features Slow­twitch – responds to repetitive stimulation; stores myoglobin; have the highest density of capillaries; has the  smallest average diameter Fast­twitch – responds quickly and to repetitive stimulation  Fast­glycolytic – used for quick bursts of strong activation 8. List 3 ways in which skeletal muscle uses ATP. Active transport (uses ATP to restore ion gradients) Actin­Myosin crossbridge cycle  hydrolysis (breaking apart) of ATP causes the myosin “heads” to flex and pull the actin filaments closer to the  center of a sarcomere to shorten the muscle  ATP is used to separate actin and myosin, and cause the power stroke 9. Give 2 specializations of skeletal muscle that increase oxygen storage and ATP production. Slow­twitch muscles have myoglobin to store oxygen inside the cells 1. Substrate phosphorylation   ­occurs during glycolysis (4 ATP/glucose)   ­occurs during Krebs cycle (2ATP/glucose)   ­in skeletal and cardiac muscle using phosphocreatine  phosphocreatine + ADP   creatine + ATP using the enzyme creatine kinase   2. Oxidative phosphorylation (34 ATP/glucose)  ADP + Pi  ATP using the enzyme ATP synthase  (uses the energy stored in the H+ gradient that was created by reduced coenzymes and the electron transport chain) 10. Describe the various gating mechanisms for calcium channels on the plasma membrane of smooth  muscle. Smooth muscle can contract in response to graded potentials alone, as well as AP’s (caused by GP’s of course!).  Ligands or mechanical stretch can also lead to contraction, usually with calcium channel gating mechanisms  (voltage, ligand or mechanically­gated). Bladder – Stretch­gated channels Gut ­ Voltage­gated channels 11. Describe the excitation­contraction coupling process in smooth muscle.  AP on motor neuron causes release of Acetyl coA  Acetyl coA binds w/ ligand­gated sodium channel  Na+ enters cytosol, causes GP  starts an AP, AP goes down t­tubuoles  voltage­gated protein changes shape, which opens calcium channel next to it & allows calcium out of cell  (calcium stored in Sarcolemic reticulum in muscle cell)  calcium ATPase pulls calcium back into cell to stop muscle contraction  Acetylcholinesterase (enzyme) breaks down acetyl coA to stop contraction signal 12. Describe the similarities and differences in excitation­contraction coupling between smooth muscle and  skeletal muscle


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