FORM & FUNCTION (Skeletal Muscle Physiology)

Question 1

Endomysium:

Answer 1

-more delicate connective tissue surrounding each muscle fiber
-blood vessels and nerve endings penetrate the muscle within it’s connective tissue

Question 2

Fascicle:

Answer 2

-bundles of muscle fibers

Question 3

Perimysium:

Answer 3

-connective tissue surrounding each fascicle

Question 4

Epimysium:

Answer 4

-external sheath of dense connective tissues

Question 5

Muscle spindles:

Answer 5

-are stretch receptors
-intrafusal fibers
-detect changes in length of the surrounding striated muscle fibers

Question 6

Golgi tendon organ:

Answer 6

-detect changes in tension within tendons produced by muscle contraction
-inhibit motor nerve activity if tension becomes excessive

Question 7

Afferent nerve fibers:

Answer 7

-Ex. muscle spindles and Golgi tendon organ
-relay information to the CNS and regulate muscular contractions

Question 8

Motor unit:

Answer 8

-a motor neuron and all the muscle fibers it innervates
*a functional contractile unit

Question 9

Motor nerve:

Answer 9

-a bundle of many motor neurons
-innervates many motor units

Question 10

Size of motor units:

Answer 10

-small: muscles that control fine movements (fingers, eyes)
-large: large-weight bearing muscles (things, hips)

Question 11

Series-elastic component:

Answer 11

-non-contractile tendons, connective tissue and structural proteins within sarcomeres have elasticity
*absorb tension as the muscle contracts
*need to stretch out before they will actually move something (time lag/latent period)

Question 12

Graded muscle responses are:

Answer 12

-variations in the degree of muscle contraction
-required for proper control of skeletal muscle
*possible by changing the frequency or strength of stimulation

Question 13

Muscle twitch:

Answer 13

-response of a muscle to a single stimulus

Question 14

Periods of muscle twitch:

Answer 14

1. Latent period
2. Period of contraction
3. Period of relaxation

Question 15

Latent period:

Answer 15

-due to AP travelling down T-tubule, pulling the proteins, Ca2+ release and the elastic component coupling (stretching)

Question 16

Period of contraction:

Answer 16

-cross bridges form
>muscle shortens

Question 17

Period of relaxation:

Answer 17

-Ca2+ reabsorbed
>muscle tension goes to zero

Question 18

Facilitation/wave summation: different effects/stages

Answer 18

-muscle response
-wave summation
-incomplete tetanus
-complete tetanus

Question 19

Muscle response:

Answer 19

-a single stimulus leads to one muscle twitch

Question 20

Wave summation:

Answer 20

-when stimuli are frequent and muscles cannot relax=force of contraction increases

Question 21

Incomplete tetanus:

Answer 21

-very rapid stimuli result in stronger but incomplete tetanus

Question 22

Complete tetanus:

Answer 22

-sustained contraction occurs when twitches are fused together due to high-frequency stimuli

Question 23

Skeletal muscle physiological responses of one motor unit:

Answer 23

1. Threshold
2. Facilitation
3. Tetanic contraction
4. Refractory period

Question 24

Threshold:

Answer 24

-minimum stimulus need to trigger a twitch

Question 25

Facilitation:

Answer 25

-happens when a new stimulation arrives after a twitch, but before the muscle has fully relaxed or its elastic components have fully recoiled

Question 26

Tetanic contraction:

Answer 26

-results from frequent stimuli leading to sustained muscle force
-individual twitches no longer evident

Question 27

Refractory period:

Answer 27

-duration when muscle cannot respond to a second stimulus

Question 28

Recruitment:

Answer 28

-activation of additional motor units in response to increased stimulus

Question 29

Threshold stimulus: recruitment

Answer 29

-minimum stimulus required for muscle contraction

Question 30

Stimulus and response: recruitment:

Answer 30

-muscle contracts with greater force as the stimulus intensifies

Question 31

Maximum contraction:

Answer 31

-achieved when all motor units are recruited and fully activated

Question 32

2 types of muscle contraction:

Answer 32

1. Isotonic
2. Isometric

Question 33

Isotonic contraction:

Answer 33

-generate tension by shortening the muscle

Question 34

Isometric contraction:

Answer 34

-muscle length remains constant
Ex. yoga

Question 35

Length-tension (LT) relationship:

Answer 35

-relationship between muscle length and the force it can produce

Question 36

LT: optimal length

Answer 36

-at a specific length, muscle fibers overlap perfectly for maximum force

Question 37

LT: stretched muscle

Answer 37

-reduced overlap of actin-myosin
-decreased force

Question 38

LT: compressed muscle

Answer 38

-too much overlap
-decreased force

Question 39

Force-velocity (FV) relationship:

Answer 39

-relationship between the force a muscle produces and the velocity of its contraction

Question 40

FV inverse relationship:

Answer 40

-as load (or force) on a muscle increases, the velocity of a contraction decrease

Question 41

Maximum velocity: FV

Answer 41

-achieved during no-load conditions
*property of muscle fiber type
>related to the rate of ATP hydrolysis of the myosin head

Question 42

Maximum force: FV

Answer 42

-seen at zero velocity (isometric contraction)

Question 43

Metabolic demands of skeletal muscle:

Answer 43

-largest consumer of ATP in the body
-metabolic flexibility to match energy supply with demand
-adapts to different types and durations of exercise