Muscle Structure and Function Part 1 W4

Question 1

What are the functions of skeletal muscle?

Answer 1

Force production for locomotion and breathing
Force production for postural support
Heat production during cold stress
Act as an endocrine organ

Question 2

What are flexors muscle actions?

Answer 2

Decreases joint angles

Question 3

What are extensors muscle actions?

Answer 3

Increases joint angles

Question 4

What is the sarcolemma?

Answer 4

Muscle cell membrane

Question 5

What is the basement membrane?

Answer 5

Just below endomysium

Question 6

What is the endomysium?

Answer 6

Surrounds muscle fibres

Question 7

What is the perimysium?

Answer 7

Surrounds fascicles

Question 8

What is the epimysium?

Answer 8

Surrounds entire muscle

Question 9

What is the microstructure of myofibrils?

Answer 9

Contains contractile proteins:
- Actin (thin filament)
- Myosin (thick filament)

Question 10

What is the microstructure of the sarcomere?

Answer 10

Z line
M line
H zone
A band
I band

Question 11

What is the sarcoplasmic reticulum?

Answer 11

Storage sites for calcium
Terminal cisternae

Question 12

What is the transverse tubules?

Answer 12

Extend from sarcolemma to sarcoplasmic reticulum

Question 13

How does satellite cells play a key role in muscle growth and repair?

Answer 13

They increase the number of nuclei in mature muscle fibres

Question 14

What is the myonuclear domain?

Answer 14

Volume of sarcoplasm surrounding each nucleus
Each nucleus can support a limited myonuclear domain

Question 15

What is myonuclei and muscle hypertrophy relationship?

Answer 15

Increased myonuclei

Question 16

What is myonuclei and muscle atrophy relationship?

Answer 16

Decreased myonuclei

Question 17

What allows for greater protein synthesis?

Answer 17

More myonuclear

Question 18

What is the neuromuscular junction?

Answer 18

Junction between motor neuron and muscle fibre

Question 19

What is the motor end plate?

Answer 19

Pocket formed around motor neuron by sarcolemma

Question 20

What is the neuromuscular cleft?

Answer 20

Short gap between neuron and muscle fibre

Question 21

What is acetylcholine?

Answer 21

Ach is a neurotransmitter released from the motor neuron
Causes an end-plate potential (EPP)
Depolarization of muscle fibre
Signal for muscle contraction

Question 22

In the sliding filament model, what causes muscle shortening to occur?

Answer 22

Movement of actin filament over the myosin filament

Question 23

What is cross-bridge formation?

Answer 23

Actin and myosin form to create a “power stroke”

Question 24

What is a repeated contraction cycle?

Answer 24

A single contraction cycle shortens the muscle by 1% of resting length
Some muscles can shorten up to 60% of resting length

Question 25

What is excitation-contraction coupling?

Answer 25

Sequence of events where nerve impulses reaches muscle membrane and leads to muscle shortening by cross-bridge activity

Question 26

What is contraction mediated by?

Answer 26

Calcium

Question 27

What is fatigue?

Answer 27

A decline in muscle power output

Question 28

What does a decline in muscle power output occur due to?

Answer 28

Decrease in muscle force production at the cross-bridge level Decrease in muscle shortening velocity

Question 29

What are the possible causes of fatigue in heavy intensity exercise?

Answer 29

Decreased Ca2+ release from the sarcoplasmic reticulum Accumulation of metabolites that inhibit myofilament sensitivity to Ca2+

Question 30

What are the key metabolites contributing to fatigue during heavy intensity exercise?

Answer 30

Pi, H+ and free radicals - Pi and free radicals modify cross-bridge head and reduce number of cross-bridges bound to actin - H+ ions bind to Ca2+ binding sites on troponin, preventing Ca2+ binding and contraction

Question 31

What are the possible causes of fatigue in moderate intensity exercise?

Answer 31

Increased radical production Glycogen depletion

Question 32

What are the key metabolites contributing to fatigue?

Answer 32

Accumulation of Pi and H+ do not contribute to fatigue during moderate intensity exercise Radical accumulation of modifies cross-bridge head and reduces number of cross-bridges bound to actin Depletion of muscle glycogen reduces TCA cycle intermediates and decreases ATP production via oxidative phosphorylation

Question 33

What is EAMS (Exercise-associated muscle cramps)?

Answer 33

Spasmodic, Involuntary muscle contractions

Question 34

What is EAMS likely to cause in the spinal cord?

Answer 34

Hyperactive motor neurons High-intensity exercise can alter muscle spindle and Golgi Tendon Organ function Increased excitatory activity of muscle spindles and reduced inhibitory effect of the Golgi Tendon Organ

Question 35

What strategies can be used to alleviate EAMS?

Answer 35

Passive stretching often relieves this type of muscle cramp Possible that activating ion channels (transient receptor potential channels) in the mouth/ throat could send inhibitory signals to the spinal cord, and thus inhibit overactive motor neurons