muscle part 2

Question 1

contraction produces…

Answer 1

tension

Question 2

isometric contraction

Answer 2

no shortening, muscle tension increases but doesn’t exceed the load

Question 3

isotonic contraction

Answer 3

muscle shortens because muscle tension exceeds the load

concentric contraction: shortens and does work (going up during push ups)
OR
eccentric contraction: muscle contracts as it lengthens (going down during a push up)

Question 4

force and duration of contraction depend on…

Answer 4

frequency and intensity of stimuli

Question 5

motor unit

Answer 5

a motor neuron and all muscle fibers it supplies. axons of motor neurons divide into a number of axon terminals that form neuromuscular junctions with each muscle fiber

Question 6

twitch

Answer 6

briefest muscle contraction, just contraction and then relaxation

Question 7

small motor unit

Answer 7

in muscle that control fine movements (fingers, eyes)

Question 8

large motor units

Answer 8

in large weight bearing muscles (thighs, hips)

Question 9

why can you control individual muscle cells?

Answer 9

1. because of individual connections with motor endplates
2. endomysium stops every cell from firing

Question 10

motor unit contraction

Answer 10

contract asynchronously, helps prevent fatigue (allows us to hold heavier loads for longer w/o getting tired)

Question 11

myogram

Answer 11

1. latent period: time of endplate potential and excitation phase
2. stimulus, then contraction phase
3. contraction period: cross bridge formation, tension increases
4. peak of graph is maximum tension, then calcium goes away, leading to a decrease in tension
5. calcium is pumped back in by active transport

Question 12

muscle twitch comparison

Answer 12

different strength and duration of twitches due to variation in enzyme function between muscles

more specifically:
if ATP can be broken down faster by ATPase, the muscle can twitch faster

Question 13

gastrocnemius

Answer 13

springing, jumping

Question 14

soleus

Answer 14

standing, walking

Question 15

a single stimulus results in…

Answer 15

a single twitch

Question 16

what happens if we increase the frequency of stimulus?

Answer 16

-muscle doesn’t have time to completely relax between stimuli

-calcium release stimulates further contraction (summation waves)

-further increase in stimulus frequency leads to incomplete tetanus

Question 17

muscle cramp

Answer 17

complete tetanus:
when every myosin head is already attached because all the calcium has been dumped

Question 18

what happens if we increase the intensity of a stimulus?

Answer 18

-stimulus must pass threshold (when first observable muscle contraction occurs)

-muscle contracts more vigorously as stimulus strength goes above threshold

-contraction force is controlled by recruitment

Question 19

recruitment principle

Answer 19

brings more motor units so more cells are connected by motor neuron’s branches

importance: can control strength of contraction to meet the needs of the moment

Question 20

size principle

Answer 20

motor units with larger and larger fibers are recruited as stimulus intensity incrases

Question 21

size principle

Answer 21

motor units with larger and larger fibers are recruited as stimulus intensity increases

Question 22

muscle tone

Answer 22

constant, slightly contracted state of all muscles

Question 23

muscle’s source of energy for contraction

Answer 23

ATP is muscle’s only source for contraction
available stores of ATP are depleted in 4-6 seconds

Question 24

how is ATP regenerated?

Answer 24

ADP into ATP by phosphorylation by creating phosphate (CP)

anaerobic pathway (glycolysis)

aerobic respiration (supplies most of ATP. but if not enough Oxy, muscle go through lactic acid fermentation)

Question 25

anaerobic pathway

Answer 25

at 70% contractile activity:
bulging muscles compress blood vessels
oxygen delivery is impaired
lactic acid is formed (and diffuses into bloodstream)

Question 26

aerobic pathway

Answer 26

below 70% contraction

produces 95% of ATP during rest and light-moderate exercise

fuels in order: stored glycogen, glucose in blood, pyruvic acid, fatty acids

Question 27

muscle fatigue

Answer 27

physiological inability to contract

nervous fatigue:
cramps. nerve ion imbalance can’t send same intensity of signal anymore

metabolic fatigue:
lack of fuel (ATP- very rare) or lactic acidocis interferes with calcium function (pH changed, so calcium can’t work anymore)

Question 28

oxygen deficity

Answer 28

extra oxy needed after exercise for:

replenishment of oxygen reserves, glycogen stores, ATP and CP reserves

Question 29

heat production during muscle activity

Answer 29

40% of energy released in muscle activity is used for work

remaining 60% is lost as heat

to get rid of the heat, blood vessels open and skin turns red