Properties of Whole Muscle Contraction

Question 1

What is a motor unit?

Answer 1

One motor neuron and all the muscle fibers it supplies

Question 2

Fine control muscles have…

Answer 2

smaller motor units

Question 3

Large, weight-bearing muscles have…

Answer 3

larger motor units

Question 4

Every muscle fiber has ______ innervation

Answer 4

its own innervation

Question 5

Name the two ways muscle responses are graded

Answer 5

frequency of stimulation
# of motor units recruited (strength)

Question 6

What does it indicate about the motor units if a muscle contraction reached its maximum?

Answer 6

All the motor units would be activated

Question 7

What size muscle fibers are recruited for large amounts of force?

Answer 7

small, medium, AND large-fiber motor units are recruited

Question 8

Hypotonia (lack of muscle tone) indicates a problem with what?

Answer 8

spinal reflexes; could be due to lack of oxygen during birth, cerebral palsy, problems with brain development or formation in womb

Question 9

What is muscle tension?

Answer 9

The force exerted on object to be moved

Question 10

what is a load?

Answer 10

the opposing force exerted on the muscle by the object being moved

Question 11

What is the same during an isometric and isotonic contraction

Answer 11

both have cross-bridge cycling, both create tension, contraction, both doing work, both going to fatigue

Question 12

What is different about isotonic contraction versus isometric?

Answer 12

isotonic- tension great enough to move load, muscle shortens, filaments slide
isometric- tension not enough to move load, muscle does not shorten, filaments not sliding

Question 13

What are the two types of isotonic contractions?

Answer 13

concentric- muscle contracts

and eccentric- muscle elongates

Question 14

What happens during direct phosphorylation

Answer 14

Who knows?

Question 15

No but seriously, what happens during direct phosphorylation?

Answer 15

Creatine kinase pulls phosphate off CP to make ADP–>ATP, only good for about 15 seconds of energy

Question 16

How many ATP per glucose does an anaerobic pathway create?

Answer 16

2, and it’s only good for 30-40 seconds or so

Question 17

How many ATP per glucose does aerobic pathway create?

Answer 17

32, good for multiple hours of activity

Question 18

Why is there excess postexercise oxygen consumption (EPOC)?

Answer 18

the body needs to replenish stored ATP

& oxygen, and convert lactic acid –> pyruvic; aka oxygen “debt”

Question 19

Muscle fatigue is caused by lack of ATP. True or false?

Answer 19

FALSE; muscle fatigue can be due to ionic imbalances that disrupt membrane potential, too much inorganic phosphate that prevents calcium release, too much magnesium, or too much lactic acid

Question 20

Name two of the four factors affecting the number of cross-bridges that are formed (force of contraction)

Answer 20

frequency of stimulation
number of muscle fibers recruited
size of muscle fibers
amount of stretch (a little over 100% is ideal)

Question 21

What are the three muscle fiber types?

Answer 21

Slow oxidative
Fast oxidative
Fast glycolytic

Question 22

Which fiber types use aerobic metabolism?

Answer 22

Oxidative (not glycolytic)

Question 23

Which fiber types hydrolyze ATP quickly?

Answer 23

Fast fibers (not slow)

Question 24

What’s the recruitment order for the three muscle fiber types?

Answer 24

first-slow oxidative
second-fast oxidative
third-fast glycolytic

Question 25

which muscle fiber type has the fewest mitochondria?

Answer 25

fast glycolytic

Question 26

Which is the least fatigue-resistant muscle fiber type?

Answer 26

fast glycolytic muscle fibers

Question 27

Small load and high recruitment –> ___ velocity and ___duration

Answer 27

high velocity, high duration

Question 28

What happens to the muscles of people who do a lot of endurance training? Name a few things.

Answer 28

more capillary  &mitochondrial density
more activity of aerobic metabolic pathways
more capacity  to use fat  for energy
less lactate accumulation
more myocardial efficiency
more oxygen delivery
weakened stress hormone responses

Question 29

What happens to the muscles of people who do a lot of isometric exercise?

Answer 29

More immediate ATP energy delivery
more glycolytic energy delivery
More force and  power output
larger muscle fibers (NOT more muscle fibers)
more movement efficiency

Question 30

When does disuse atrophy happen?

Answer 30

immobilization or loss of neural stimulation (to maintain muscle tone)

Question 31

At what point is regeneration of muscle impossible?

Answer 31

If there is only 25% of muscle mass left, paralysis is imminent