Muscle Physiology

Question 1

Unused muscle is degraded or muscle protein degraded faster than it is replaced are two ways that ________ can occur.

Answer 1

Muscular atrophy

Question 2

What does troponin inhibit and what prevents troponin from doing so?

Answer 2

Cross-bridging and Ca++ (troponin has a high affinity for Ca++)

Question 3

A ________ is all muscle fibers that are innervated by a single neuron.

Answer 3

Motor unit

Question 4

What adds new sarcomeres to the ends of muscles?

Answer 4

Stretching

Question 5

When is phosphocreatine used and for how long?

Answer 5

At the beginning of contraction (maximal) for approximately 5-8 seconds

Question 6

What are I bands and how do they appear under a light microscope?

Answer 6

Regions composed entirely of actin and appear white

Question 7

Fewer mitochondria, larger, extensive sarcoplasmic reticulum, minimal blood supply, less myoglobin (white), and glycolytic enzymes present are all characteristics of ________ type muscle fibers.

Answer 7

Fast

Question 8

How can hypertrophy be described in muscle?

Answer 8

Existing muscle fibers gain more actin and myosin. New muscle fibers are not created

Question 9

How much energy from nutrients gets used to make ATP and how much of nutrients can be converted to Work, under optimal conditions?

Answer 9

50% and 25%

Question 10

What happens when a muscle is at rest?

Answer 10

The muscle receives impulses from the spinal cord so a certain amount of tautness remains in the muscle at all times

Question 11

Lots of mitochondria, smaller, smaller nerves, extensive blood supply, and large supplies of myoglobin (red) are all characteristics of ________ type muscle fibers.

Answer 11

Slow

Question 12

What is believed to attach tropomyosin to actin?

Answer 12

Troponin

Question 13

What are the two types of contractions and their respective subdivisions?

Answer 13

Isometric: contraction where muscle does not change length

Isotonic:

• eccentric: contraction where muscle gets longer
• concentric: contraction where muscle gets shorter

Question 14

What are Z disks and what is the region between 2 Z disks called?

Answer 14

The anchoring site of actin. Sarcomere

Question 15

What is required for Ca++ to be pumped back into the sarcoplasmic reticulum?

Answer 15

ATP

Question 16

What anaerobic method of ATP production can be used to supply muscle? How long does it last?

Answer 16

Glycolysis. Approximately 1 min

Question 17

Small motor units are recruited initially followed by larger motor units (if necessary) is a process known as ________.

Answer 17

Multiple fiber summation

Question 18

How does each head of myosin act when “walking” across the actin?

Answer 18

Independently

Question 19

How many myofibrils is each muscle fiber composed of?

Answer 19

Hundreds to thousands (approximately 1500 myosin filaments and 3000 actin filaments)

Question 20

What are the spaces between muscle fibers filled with and what does it contain?

Answer 20

Sarcoplasm. K, Mg, PO4, enzymes, lots of mitochondria, sarcoplasmic reticulum

Question 21

________ motor muscles have motor units consisting of a few muscle fibers whereas ________ motor muscles have motor units consisting of many muscle fibers.

Answer 21

Fine, gross

Question 22

________ occurs when there is an increased frequency of action potentials (which can lead to tetany or maximal sustained contraction).

Answer 22

Frequency summation

Question 23

What are A bands and how do they appear under a light microscope?

Answer 23

Composed of myosin filaments, either alone or overlapping with I bands. They appear dark

Question 24

What links Z disks with myosin filaments?

Answer 24

Titin

Question 25

What metabolic pathway supplies 95% of sustained contraction?

Answer 25

Oxidative phosphorylation

Question 26

A ________ is a normal physiological mechanism via an action potential and Ca++ release, whereas a ________ is tightening due to collagenous bands laid down by fibroblasts.

Answer 26

Contraction, contracture

Question 27

How far do muscle fibers span and how many neurons innervate one fiber?

Answer 27

The entire length of the muscle and only 1 neuron per fiber

Question 28

If loss of signal from neurons causes atrophy in muscle, what will eventually happen over time if there is no recovery?

Answer 28

Replacement by fibrous and fatty tissue which contracts over time