MSK Session 2- Skeletal Muscle Structure, Morphology And Mechanics

Question 0

What are the four functions of skeletal muscle?

Answer 0

• aid movement
• stabilise joints
• posture
• heat generation

Question 1

Describe skeletal muscle.

Answer 1

• striated
• unbranched, long fibres
• multiple, peripheral nuclei.

Question 2

Give an example of a unipennate muscle.

Answer 2

The lateral tibial muscle.

Question 3

Give an example of a bipennate muscle.

Answer 3

Rectus femoris muscle

Question 4

Give an example of a multipennate muscle.

Answer 4

Deltoid

Question 5

Give an example of a fusiform muscle

Answer 5

Biceps brachii

Question 6

Give an example of a convergent muscle

Answer 6

Pectoralis major

Question 7

Give an example of a circular muscle

Answer 7

Orbicularis oris (mouth)

Question 8

Give an example of a parallel muscle.

Answer 8

Sartorius

Question 9

Describe the gross anatomy of skeletal muscle.

Answer 9

Muscle fibres are surrounded by endomysium and lie in parallel.
They form bundles to form fascicles, which are surround by perimysium.
Fascicles make up the muscle, which is surrounded by epimysium.

Question 10

What do tendons do?

Answer 10

Attach muscle to bone

Question 11

What is fasciculation?

Answer 11

It is muscle twitching due to fascicles making small twitching motions.

Question 12

What is excessive muscle twitching a potential sign of?

Answer 12

Motor neurone disease.

Question 13

What is the origin and insertion of the triceps brachii?

Answer 13

Origin- the scapula and humerus

Insertion- tendon inserts on the ulna

Question 14

What is the origin and insertion of the biceps brachii?

Answer 14

Origin- the scapula

Insertion- the tendon inserts on the radius

Question 15

Describe a first class lever and give an example.

Answer 15

Acts like a see saw.

An example is the skull- contraction of the muscle on the posterior wall of the neck pulls the skull back.

Question 16

Describe what a second class lever is and give an example.

Answer 16

It acts like a wheelbarrow.
An example is the gastrocnemius muscle on the posterior of the lower leg. When it contracts and you are standing on tiptoes.

Question 17

What is a third class lever and give an example.

Answer 17

It acts like a fishing rod.

An example is when the biceps contract and the arm is flexed about the elbow joint.

Question 18

Which type of lever is the most: efficient, inefficient?

Answer 18

Efficient- first class lever 
Inefficient-third class lever

Question 19

What are agonist muscles?

Answer 19

They are prime movers and produce a specific movement.

Question 20

What are antagonist muscles?

Answer 20

They oppose the action of prime movers.

Question 21

What are synergistic muscles?

Answer 21

They are muscles that complement the movement of prime movers. They therefore keep the force in one direction.

Question 22

What are fixator muscles and what do they do?

Answer 22

They stabilise the action of prime movers.

Question 23

What is compartment syndrome?

Answer 23

When a blood haematoma forms in the in extensible compartment of a muscle. This puts pressure on the blood vessels and nerves within the compartment and can therefore cause a loss of nervous innervation and muscle contraction.

Question 24

What is isotonic contraction, and what are the two types?

Answer 24

It is when there is constant tension, but the muscle length changes in relation to the production of movement to move the load.

• concentric- when the muscle shortens, causing movement
• eccentric- when the muscle lengthens and therefore relaxes, while exerting a force.

Question 25

What is isometric contraction?

Answer 25

When the muscle length remains the same, no movement occurs, but the force is increased.

Question 26

What are the three muscle fibre types?

Answer 26

Slow twitch
Fast twitch IIa
Fast twitch IIb

Question 27

What are the differences between fast twitch IIa and fast twitch IIb fibres? (7)

Answer 27

A- aerobic respiration, lots of myoglobin, red in colour, lots of mitochondria, rich capillary supply, can fatigue, used for walking/sprinting
B- anaerobic respiration, few myoglobin, white in colour, few mitochondria, poor capillary supply, fatigues rapidly, used for short intense movement.

Question 28

What are slow twitch fibres used for? (2)

Answer 28

Endurance activity

Posture

Question 29

Which type of respiration do slow twitch fibres undergo?

Answer 29

Aerobic

Question 30

Are slow twitch fibres easily fatigued?

Answer 30

No

Question 31

What is proprioception?

Answer 31

It is an awareness of self. That proprioreceptors will recognise muscle stretch and tension and inform the brain, as well as informing it where the muscle is in 3D space.

Question 32

What is a motor unit?

Answer 32

A motor neurone and the muscle fibres it Innervates.

Question 33

If fine control is required, does a motor neurone innervate many or few muscle fibres?

Answer 33

Few

Question 34

What is cross talk?

Answer 34

It is the communication between neurones and muscles via signalling molecules.

Question 35

When do muscles relax, with regards to calcium?

Answer 35

When calcium is taken up in the SR., or is bound by calmodulin.

Question 36

What causes muscle cramp?

Answer 36

Anaerobic conditions cause pyruvate to be converted to lactate. If this builds up, it causes muscle cramps.

Question 37

What is intermittent claudication?

Answer 37

It is intermittent muscle pain caused by a lack of blood flow to muscle, due to a partial blockage.

Question 38

What is Rigor Mortis?

Answer 38

An example of continuous muscle contraction.

When death occurs, ATP is depleted, therefore myosin heads can’t detach and muscles remain in a contracted state.

Question 39

How long after death does Rigor Mortis peak?

Answer 39

12-13 hours.