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AN SC 310 - 13
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Who were the 2 most influential scientists of muscle physiology?
Luigi Galvani
Alessandro Volta
What are the 3 classifications of muscles?
Skeletal
Smooth
Cardiac
What is a muscle?
Group of fascicles
What are muscles fixed to?
Bones
Tendons
What is muscle membrane called?
Sarcolemma
What is muscle cell plasm called?
Sarcoplasm
What is the reticulum in muscle called and what is it similar to?
Sarcoplasmic reticulum
Smooth endoplasmic reticulum
What gives muscles a striated appearance?
Myofibrils: actin and myosin
What is thick filament?
Actin
What is thin filament?
Myosin
What is the smallest functional unit of muscle?
Sarcomeres
1. A band
2. I band
3. H band
4. Crossbridges
5. Actin
6. Myosin
7. Z line
8. M line
9. Sarcomere
10. Myofibril
1. Sarcomere
2. Z line
3. M line
4. H band
5. A band
6. I band
What is a contractile protein?
Actin
What are 2 regulatory proteins?
Tropomyosin
Troponin
What are the 3 types of troponin and what do they do?
A - Actin binding
T - Tropomyosin binding
C - Calcium binding
What are the 2 binding sites on actin heads?
Actin-binding site
ATPase site
What is the "bare zone"?
Site on thick filament that has no crossbridges (heads)
Which line/band are myosin head and tail near?
Tail - toward M line
Head - toward I band
What provides elasticity in muscles?
Titin
What is the sliding-filament model?
Thick and thin filaments do not shorten, they overlap and slide past e/o
What bands shorten during contraction?
I band
H band
What are crossbridge cycles?
Cyclical formation of links btwn actin and myosin resulting in the sliding of thin filaments toward the M ling of a sarcomere
Crossbridge cycle
What is the power stroke?
Myosin head pivots, pulling the actin filament with it
Crossbridge Cycle
What is rigor?
Myosin and actin are tightly bound
Crossbridge Cycle
What is binding?
P
i
is realeased from the ATPase site
Crossbridge Cycle
What is cocking?
ATP is hydrolyzed; myosin is in its high-energy form
Crossbridge Cycle
What is unbinding?
The myosin head detaches from the actin
What is asynchronous cycling and why does it occur?
Crossbridge cycles are purposely out of step with e/o
Muscle cells can continuously generate force during contraction
What is excitation-contraction coupling?
Sequence of events whereby an AP in the sarcolemma causes contraction
What are the 2 most important factors in muscle contraction?
Neural input from motor neuron
Ca
2+
release from sarcoplasmic reticulum
What is the role of Ca
2+
in contraction?
Binds to troponin = movement of troponin = movement of tropomyosin = exposed binding sites for myosin on actin = crossbridge cycle = contraction
What are the 6 steps of excitation-contraction coupling?
1. AP in sarcolemma
2. AP down T tubules
3. DHP receptors of T tubules open Ca
2+
channels in lateral sacs of SR
4. Ca
2+
increases cytosol
5. Ca
2+
binds to troponin, shifting tropomyosin
6. Crossbridge cycling occurs
What are the 2 receptors involved in Ca
2+
release?
DHP
Ryanodine
What must happen to terminate contraction?
Ca
2+
must leave troponin
Tropomyosin covers myosin binding site on actin
How is Ca
2+
removed from cytosol?
Ca
2+
ATPase in SR transports it from cytosol into SR
Author
ebacker
ID
180909
Card Set
AN SC 310 - 13
Description
Lecture 13 - Muscle Physiology
Updated
10/31/2012, 4:34:20 AM
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