Muscles 3

Question 1

Tension produced in individual muscle fibers can vary due to?

Answer 1

• length-tension relationship

- frequency of stimulation

Question 2

Tension produced by entire muscle can vary even more widely due to?

Answer 2

• number of muscle cells receiving nerve stimulation, commanding them to contract
• muscle cells are grouped in motor units

Question 3

all the muscle fibers innervated by?

Answer 3

one motor neuron

Question 4

Amount of tension produced in a muscle determined by?

Answer 4

number of motor units activated

Question 5

What kind of motor unit summation for sustained contractions?

Answer 5

asynchronous motor unit summation

Question 6

Small motor unit

Answer 6

precise control

-one motor neuron innervates a small number of muscle fibers

Question 7

large motor unit

Answer 7

gross movement control

-one motor neuron innervates a large number of muscle fibers

Question 8

muscle tone is caused by?

Answer 8

• resting tension in skeletal muscle
• Some motor units are always active; tense and firm the muscle
• active motor units are constantly changing, muscle tone is not produced by a specific subset of motor units

Question 9

Muscle tone functions

Answer 9

• stabilizes bones and joints

- greater resting muscle tone causes higher resting rate of metabolism

Question 10

Isotonic contraction

Answer 10

tension rises, length of muscle changes

Question 11

Concentric contraction

Answer 11

muscle tension exceeds resistance and muscle shortens

Question 12

Eccentric contraction

Answer 12

peak tension developed is less than the resistance, muscle elongates

Question 13

physiology of isometric contractions

Answer 13

• tension produced never exceeds resistance
• individual muscle fibers shorten until internal connective tissues and tendons are taut
• cannot shorten further bc tension doesn’t exceed resistance

Question 14

lengthening a muscle

Answer 14

• no active mechanism for muscle fiber elongation

- muscle cell doesn’t cause itself to length after contraction process ends

Question 15

how does a muscle return to resting length?

Answer 15

• recoil in elastic components in connective tissue
• contraction of opposing muscle groups
• gravity

Question 16

How long to high energy molecules in the muscle last and what are they?

Answer 16

~15 sec once contraction begins, of ATP and creatine phosphate (CP)

Question 17

Creatine Phosphate reserves

Answer 17

• muscle cell makes more ATP than needed; extra ATP transfers high energy phosphate to creatine for storage
• CP reserves releases stored energy to convert ADP to ATP when ATP is needed

Question 18

Cellular respiraton

Answer 18

uses O2 and releases CO2

• occurs in mitochondria
• citric acid cycle
• electron transport chain

Question 19

citric acid cycle

Answer 19

CO2 is produced

Question 20

Electron transport chain

Answer 20

• ATP synthesis

- O2 is used

Question 21

Resting muscle fibers rely o what to generate ATP?

Answer 21

Aerobic metabolism of fatty acids

Question 22

how is aerobic metabolism of FA used to generate ATP?

Answer 22

• FA absorbed from circulation
• broken down to 2 C units of acetyl CoA which enter into the CAC
• Excess ATP used to store glucose into glycogen, create creatine phosphate

Question 23

explain pyruvate metabolism

Answer 23

Anaerobic

-insufficient oxygen converts pyruvate to lactic acid

Question 24

What does conversion of pyruvate to lactic acid do to cofactors

Answer 24

Recycles cofactors needed by glycolysis enzymes

Question 25

what happens in resting muscle metabolism?

Answer 25

fatty acids to mitochondria to produce atp

Question 26

what happens in moderately active muscle metabolism

Answer 26

still functions aerobically, glucose and fatty acids are catabolized, ATP produces is used to power contraction

Question 27

What happens in peak activity muscle metabolism?

Answer 27

ATP is produced through glycolysis with lactic acid as a by-product. Mitochondrial activity provides 1/3 of the ATP consumed.

Question 28

Advantage of anaerobic metabolism

Answer 28

produces ATP rapidly at an O2 deficit

Question 29

Disadvantage of anaerobic metabolism

Answer 29

inefficient use of glucose | -lactic acid lowers intracellular pH

Question 30

When does the recovery period starts?

Answer 30

immediately after activity ends

Question 31

What is oxygen debt?

Answer 31

- excess post-exercise oxygen consumption - more intense exercise=larger O2 debt - amt of O2 req. during resting period needed to get rid of lactic acid and restore creatine phosphate reserves

Question 32

What happens during the recovery period?

Answer 32

- oxygen debt - rebuild ATP and creatine phosphate levels - recycle lactic acid to make pyruvate - rebuild glycogen reserves

Question 33

Fatigued muscle

Answer 33

a muscle that can no longer perform at required level of activity

Question 34

causes of fatigue

Answer 34

- exhaustion of energy resources - build up of lactic acid and lowering of pH - psychological fatigue