9 Regulation of Skeletal Muscle Contraction

Question 1

each muscle depends on innervation by a

Answer 1

motor nerve

Question 2

motor unit

Answer 2

one motor neuron plus all of the muscle fibers it innervates

Question 3

the transfer of a signal from nerve to muscle takes place at the

Answer 3

neuromuscular junction
motor end plate
myoneuronal junction

(same thing)

Question 4

presynaptic portion of NMJ contains vesicles with

Answer 4

acetylcholine

Question 5

postsynaptic portion of NMJ contains

Answer 5

nicotinic acetylcholine receptors (ligand-gated)

Question 6

order of events during neuromuscular transmission

Answer 6

1. action potential at axon terminal
2. Ca2+ enters axon terminal
3. Acetylcholine released across synaptic cleft, binds to postsynaptic membrane
4. Na+ and K+ ion channels open
5. Postsynaptic membrane becomes depolarized
6. Muscle AP triggered
7. Ach hydrolyzed
8. Choline is taken up, vesicles are refilled with Ach

Question 7

cardiac cells are interconnected by

Answer 7

gap junctions

Question 8

force of contraction in cardiac cells is dependent on

Answer 8

extracellular Ca2+ conc

Question 9

calcium enters cardiac cells via

Answer 9

voltage-dependent slow calcium channels
or
L-type calcium channels

Question 10

cardiac mm calcium comes from 2 sources

Answer 10

1/ extracellular Ca2+
2/ Ca2+ in SR
“calcium-induced calcium release”

Question 11

_____ transfers a phosphate group to ADP to make it ATP

Answer 11

creatine phosphate

Question 12

____ has ATPase activity

Answer 12

myosin

Question 13

glycolysis

Answer 13

anaerobic

2 ATP net

Question 14

citric acid cycle/ox phos

Answer 14

aerobic

36 ATP net

Question 15

oxygen debt

Answer 15

extra oxygen consumption that occurs after exercise; stores are taken from hemoglobin and myoglobin; lactic acid is the largest contributor

Question 16

3 sources of ATP production during muscle contraction

Answer 16

1/ creatine phosphate
2/ anaerobic glycolysis
3/ oxidative phosphorylation

Question 17

isometric contraction

Answer 17

a contraction that generates force with no muscle shortening

Question 18

isotonic contraction

Answer 18

a contraction that results in a shortening against a constant force

Question 19

twitch

Answer 19

contraction and relaxation of a skeletal mm to a single stimulus (single AP)

Question 20

total tension in a muscle depends on 2 things

Answer 20

1/ # of mm fibers contracting within a mm (recruitment)

2/ tension of each fiber (frequency of APs)

Question 21

____ of _____ can influence the tension developed by each mm fiber

Answer 21

frequency of stimulation

Question 22

summation

Answer 22

the force provided by the second stimulus (AP) adds to the force provided by the first (mm is re-stimulated before relaxation is complete)

Question 23

tetanus

Answer 23

maximal sustained contraction; mm is stimulated so rapidly it does not have a opportunity to relax between stimuli

Question 24

___ is achieved by increasing the excitatory synaptic input to the motor neuron

Answer 24

recruitment

Question 25

red muscle fibers

Answer 25

AEROBIC (lots of myoglobin)
mitochondria abundant
fast twitch/slow twitch

Question 26

white muscle fibers

Answer 26

ANAEROBIC
fast twitch only, fatigue quickly
fewer mitochondria