MSK Session 2 (Lecture 2.1)

Question 1

What are the functions of skeletal muscle?

Answer 1

1) Movement
2) Posture
3) Stability of joints
4) Heat generation

Question 2

What are the 7 arrangements of skeletal muscle?

Answer 2

1) Circular
2) Convergent
3) Parallel
4) Unipennate
5) Bipennate
6) Multipennate
7) Fusiform

Question 3

What is fasciculation? Can it be harmful?

Answer 3

Involuntary local twitch of a muscle fibre caused by a spontaneous depolarization of a lower motor neuron. Can be benign and harmless or can be indicative of motor neurone disease?

Question 4

Describe and give an example of a first class lever.

Answer 4

Where the fulcrum is in the middle with the force and load on either side. It is very efficient e.g. moving head upwards by contraction of neck muscles

Question 5

Describe and give an example of a second class lever.

Answer 5

Load is in the middle with the force being at one end and the fulcrum being at the other. It is efficient e.g. gastrocnemius elevating heel of foot.

Question 6

Describe and give an example of a third class lever.

Answer 6

The fulcrum is at one end with the resistance and force on the same side near the fulcrum. e.g. biceps brachii flexing forearm

Question 7

What are the four muscle groups?

Answer 7

1) Agonists
2) Antagonists
3) Synergists
4) Fixators

Question 8

Define an agonist.

Answer 8

Prime movers (main muscles responsible for a particular movement)

Question 9

Define an antagonist.

Answer 9

Oppose prime movers

Question 10

Define synergists.

Answer 10

Assist prime movers (neutralise extra motion) e.g. side motion

Question 11

Define fixators.

Answer 11

Stabalizes action of prime mover e.g. fixes non-moving joint when prime mover acting over two joints.

Question 12

What is compartment syndrome?

Answer 12

Build up of pressure in one of the body’s compartments containing muscles and nerves. This causes nerve compression and in severe cases muscle and nerve ischaemia.

Question 13

What are the two types of muscle contraction?

Answer 13

1) Isotonic

2) Isometric

Question 14

Describe isotonic contraction and its two subdivisions

Answer 14

Constant tension, variable muscle length

1) Concentric - muscle shortens
2) Eccentric - muscle exerts force while being extended

Question 15

Describe isometric contraction.

Answer 15

Constant length, variable tension e.g. hand grip

Question 16

State the three types of muscle fibre.

Answer 16

1) Type 1 (slow oxidative) - red
2) Type 2a (fast oxidative) - intermediate
3) Type 2b (fast glycolytic) - white

Question 17

Describe type 1 fibres.

Answer 17

Aerobic
High myoglobin
Many mitochondria
Rich capillary supply
Fatigue resistant

Question 18

Describe type 2a fibres.

Answer 18

Aerobic
High myoglobin 
Many mitochondria
Rich capillary supply
Moderate fatigue resistance

Question 19

Describe type 2b fibres

Answer 19

Anaerobic glycolysis
Low myoglobin
Few mitochondria
Poor capillary supply
Rapidly fatigable

Question 20

What is proprioception ? Where can proprioceptors be found?

Answer 20

Feedback control of muscle tension and movement. Proprioceptors can be found in muscle spindles which are located in the muscle belly sensing how stretched the muscle is. They travel along afferent sensory nerves towards the brain.

Question 21

What is a motor unit? Describe how it can affect fine vs crude control of muscles.

Answer 21

A motor neurone and the muscle fibres it innervates.

If a motor neurone innervates fewer muscles then this will give rise to fine control as there would be individual fibre recruitment rather than inervating 1000s of muscle fibres giving crude control.

Question 22

Give examples of signalling molecules that communicate between nerve and muscle.

Answer 22

Neurotrophin-3, cardiotrophin-1, IGF1

Question 23

What determines muscle tone?

Answer 23

1) Motor neurone activity

2) Muscle elasticity

Question 24

How can hypotonia arise? List 3 different causes.

Answer 24

Hypotonia is a low level of muscle tone

1) Cerebral or spinal neural shock
2) Lesion of lower motor neurones e.g. polyneuritis
3) Primary degeneration of muscle e.g. myopathies

Question 25

What is spatial summation?

Answer 25

More motor neurones activated so more muscle fibres recruited to develop more force

Question 26

What is temporal summation?

Answer 26

Increased frequency of action potentials to muscle fibres over time. Can cause tetanus if constant stimulation occurs leading to prolonged muscle contraction. (e.g. Clostridium tetani)