behavior of skeletal muscle

Question 1

structure of neuromuscular junction

Answer 1

axon terminal (synaptic end bulb), synaptic vesicles (contains neurotransmitter), synaptic cleft, acetylcholine receptors

Question 2

sliding filament theory of skeletal muscle contraction

Answer 2

myosin stays but while actin slides towards the center which causes muscle shortening
–> actin (thin) pulled toward center (M-line) by myosin

Question 3

sequence of events involved in the contraction of skeletal muscle fiber

Answer 3

1. motor neuron fires (release and binding of acetylcholine, depolarization)
2. action potential travels along sarcolemma
3. action potential travels to T tubules (release of calcium)
4. contraction

Question 4

motor neuron process

Answer 4

1. action potential reaches axon terminal to trigger opening of calcium channels
2. calcium enters and causes acetylcholine release
3. acetylcholine cross synaptic cleft and binds to receptors
4. ion channels open and allows sodium in + potassium out to depolarize

Question 5

muscle fiber excitation

Answer 5

action potential moves across sarcolemma (depolarization –> repolarization)

Question 6

excitation contraction coupling

Answer 6

1. action potential goes to T tubules
2. terminal cisterns release calcium
3. calcium binds to troponin
4. troponin undergoes conformational change to reveal binding sites for myosin

Question 7

cross bridge cycle

Answer 7

1. cocking myosin head where ATP is hydrolyzed and loaded into position
2. cross bridge formation where myosin head binds to site on actin
3. power stroke where filament slides as myosin head flexes and pulls actin
4. ATP attaches to myosin head and release from actin

Question 8

twitch

Answer 8

minor involuntary contraction of muscle
–> depends on length of muscle, fatigue, temperature

Question 9

motor unit

Answer 9

single neuron innervating few fibers

Question 10

myogram

Answer 10

graph that measures twitch
–> latent period, contraction phase, and relaxation phase

Question 11

isotonic vs isometric contraction

Answer 11

isotonic –> tension is the same while muscle length changes
isometric –> no change in muscle length

Question 12

concentric vs eccentric contraction

Answer 12

concentric –> muscle shortens
eccentric –> muscle lengthens