MSK Physiology

Question 1

State the level of organisation in skeletal muscle.

Answer 1

Whole muscle
Muscle Fibre
Myofibril
Sarcomere

Question 2

Which two proteins do myofibrils and sarcomeres contain?

Answer 2

Myocin

Actin

Question 3

How do myocin molecules appear?

Answer 3

Thick filaments (darker)

Question 4

How do actin molecules appear?

Answer 4

Thin filaments (lighter)

Question 5

Do fine motor body parts have more or less muscle fibres?

Answer 5

Less (generate less power)

Question 6

How are skeletal muscles attached to the skeleton?

Answer 6

By tendons

Question 7

What is the name of the system that bones, muscles and joints form?

Answer 7

Lever system

Question 8

Where is the sarcomere found?

Answer 8

Between 2 Z-lines in the myofibril

Question 9

Name the 4 zones of the sarcomere?

Answer 9

A-band

H-zone

M-line

I-band

Question 10

Where is the M-line found?

Answer 10

Running down the middle of the A-band

Question 11

How is muscle tension produced?

Answer 11

By actin filaments sliding across myosin filaments.

Sliding filament theory

Question 12

Is ATP required for:

a) Muscle contraction
b) Muscle relaxation
c) Both

Answer 12

c) Both

Question 13

When is calcium released from the sarcoplasmic reticulum in skeletal fibres?

Answer 13

When the surface action potential spreads down the transverse tubule.

Question 14

What happens when the muscle fibre is relaxed?

Answer 14

No cross-bridge binding

The cross-bridge binding site on actin is physically covered by the troponin-tropomyosin complex.

Question 15

What happens when the muscle fibre is excited?

Answer 15

Calcium binds with troponin, pulling the troponin-tropomyosin complex aside to expose the cross-bridge binding site.

Cross-bridge binding occurs.

Question 16

What is the name of the transmitter at the neuromuscular junction?

Answer 16

Acetylcholine

Question 17

Why is calcium needed for muscle contraction?

Answer 17

Needed to switch on cross-bridge formation

Question 18

What is motor unit recruitment?

Answer 18

When more motor units are stimulated to allow a stronger contraction to be achieved

Question 19

What does the tension developed by each contracting muscle fibre depend on?

Answer 19

• Frequency of stimulation
• Summation of contractions
• Length of muscle fibre at the onset of contraction
• Thickness of muscle fibre

Question 20

Can tetanus occur in cardiac muscle?

Answer 20

NO

Question 21

What is isotonic contraction used for?

Answer 21

Body movements

Moving objects

Question 22

What is isometric contraction used for?

Answer 22

Supporting objects in fixed positions

Maintaining body posture

Question 23

What happens in isometric contraction?

Answer 23

Skeletal muscle contraction develops at constant muscle length.

Question 24

What happens in isotonic contraction?

Answer 24

Skeletal muscle contraction remains constant as the muscle length changes

Question 25

What is an immediate source of ATP to muscle?

Answer 25

Transfer of high energy phosphate from creatine phosphate to ADP.

Question 26

What is the main source of ATP when oxygen is present?

Answer 26

Oxidative phosphorylation

Question 27

What is the main source of ATP when oxygen is not present?

Answer 27

Glycolysis

Question 28

Name the three types of skeletal muscle fibres.

Answer 28

Slow-oxidative (type I) Fast-oxidative (type IIa) Fast Glycolytic (Type IIx)

Question 29

Which neutron is involved in a reflex action?

Answer 29

Alpha neuron

Question 30

What acts as sensory receptors for the stretch reflex?

Answer 30

Muscle spindles (intrafusal fibres)

Question 31

Which efferent neurons supply the muscle spindles?

Answer 31

Gamma motor neurons

Question 32

What is myotonia?

Answer 32

Abnormalities in muscle membrane ion channels

Question 33

Which investigations are used in neuromuscular disease?

Answer 33

EMG Nerve conduction studies Muscle enzymes Inflammatory markers Muscle biopsy

Question 34

What are the mechanisms of joint disease?

Answer 34

Changes in one of the three major components of cartilage (water, collagen, proteoglycans) If the rate of extracellular matrix degradiation exceeds the rate of its synthesis.