Skeletal Muscle Physiology

Question 1

Name some of the overall physiological functions of skeletal muscle

Answer 1

Maintaining posture
Purposeful movement
Respiratory movement
Heat production

Question 2

What are the three types of muscles in the body?

Answer 2

Skeletal
Cardiac
Smooth

Question 3

Which types of muscle are striated?

Answer 3

Skeletal

Cardiac

Question 4

Skeletal muscle is innervated by the somatic/autonomic nervous system and is subject to voluntary/involuntary control.

Answer 4

Somatic

Voluntary

Question 5

Skeletal muscle has neurogenic/myogenic initiation of contraction

Answer 5

Neurogenic

Question 6

What is the neurogenic transmitter?

Answer 6

ACh

Question 7

What are skeletal muscle fibres organised into?

Answer 7

Motor units

Question 8

Define a motor unit

Answer 8

A single alpha motor neuron and all the skeletal muscle fibres it innervates

Question 9

Muscles serving precise movements have many muscle fibres per motor unit. True/false?

Answer 9

False - have few muscle fibres per motor units

Question 10

Give some examples of muscles with few fibres per motor unit

Answer 10

Intrinsic hand muscles

Extra-ocular muscles

Question 11

What is the overall organisation of skeletal muscle?

Answer 11

Muscle -> muscle fibre -> myofibril -> sarcomere

Question 12

What is the functional unit of muscle?

Answer 12

Sarcomere

Question 13

Actin and myocin are arranged into sarcomeres. True/false?

Answer 13

True

Question 14

What produces muscle tension?

Answer 14

Actin sliding on myosin

Question 15

What is required for contraction and relaxation of muscle?

Answer 15

ATP

Question 16

What switches on cross-bridge formation between actin and myosin?

Answer 16

Calcium

Question 17

Calcium binds to what in switching on cross bridge formation?

Answer 17

Troponin

Question 18

What occurs when there is no ATP to contract or relax skeletal muscle?

Answer 18

Rigor complex

Question 19

What are the two main factors in the gradation of skeletal muscle tension?

Answer 19

Number of muscle fibres contracting

Tension developed by each contracting fibre

Question 20

What effect does a shorter action potential than the duration of twitch have on muscle contraction?

Answer 20

It means repeated stimulation can bring about stronger and eventually tetanic contraction

Question 21

Tetanic contraction of cardiac muscle is normal. True/false?

Answer 21

False

Question 22

What is the optimum length of the muscle fibre for contraction?

Answer 22

Its normal resting length

Question 23

What is isotonic contraction of muscle?

Answer 23

When muscle tension remains constant but muscle fibre length changes

Question 24

When do isotonic contractions occur?

Answer 24

Body movements

Moving objects

Question 25

What is isometric contraction of muscle?

Answer 25

When muscle fibre length remains constant but muscle tension changes

Question 26

When do isometric contractions occur?

Answer 26

Supporting objects in fixed positions | Maintaining body posture

Question 27

What are the main differences between types of skeletal muscle fibres?

Answer 27

Pathway for ATP synthesis Resistance to fatigue Activity of myosin ATPase

Question 28

Each motor unit usually contains only one type of fibre. True/false?

Answer 28

True

Question 29

What are the metabolic pathways supplying ATP in muscle fibre?

Answer 29

Creatine phosphate Oxidative phosphorylation Glycolysis

Question 30

Name the three types of skeletal muscle fibres.

Answer 30

``` Type I (slow-oxidative) Type IIa (fast-oxidative) Type IIx (fast glycolytic) ```

Question 31

Why are type I fibres slow?

Answer 31

Low myosin ATPase activity

Question 32

What is the main difference between type IIa and IIx muscle fibres?

Answer 32

IIa have high oxidative phosphorylation capacity | IIx have low

Question 33

What are type I fibres used for?

Answer 33

Prolonged low work aerobic activities (walking)

Question 34

What are type IIa fibres used for?

Answer 34

Prolonged moderate work activities (jogging)

Question 35

What are type IIx fibres used for?

Answer 35

Short-term high intensity activities (jumping)

Question 36

What occurs in the stretch reflex?

Answer 36

Stretching of muscle spindle increases afferent neuron firing which synapse in the spinal cord with the alpha motor neurons resulting in contraction of stretched muscle

Question 37

The knee jerk assesses which peripheral nerve?

Answer 37

Femoral

Question 38

Give some causes of myopathy

Answer 38

Congenital Muscular dystrophy Inflammation Toxicity

Question 39

Give some symptoms of myopathy

Answer 39

Muscle weakness Myalgia Muscle stiffness