2 - Skeletal Muscle

Question 1

Give four functions of skeletal muscle

Answer 1

MovementPostureStability of joints Heat generation

Question 2

Why is a mechanical effiency of 20% useful for skeletal muscle?

Answer 2

Large amount of energy lost as heat e.g. shivering

Question 3

Give 7 types of skeletal muscle

Answer 3

CircularConvergentParallelUnipennateMultipennateFusiformBipennate

Question 4

What is a first class lever muscle?

Answer 4

Force —- Fulcrum — LoadLoad and force on opposing sides

Question 5

Give an example of a first class lever muscle

Answer 5

The muscles in the posterior region of the neck attached to the skull

Question 6

What is a second class lever?

Answer 6

Force – Load – FulcrumForce and load on same side of fulcrum, with load between force and fulcrum

Question 7

Give an example of a second class lever

Answer 7

The muscles in the back of the calf flex the foot by exerting force on the calcaneus

Question 8

What is a third class lever

Answer 8

Fulcrum – Force – Load

Question 9

Give an example of a third class lever

Answer 9

Biceps

Question 10

What is the most common type of lever? How efficient are they?

Answer 10

Third class, the least efficient

Question 11

What is an agonist?

Answer 11

Prime movers (main muscles responsible for a particular movement

Question 12

What is an antagonist?

Answer 12

Oppose prime movers (agonists)

Question 13

What are synergists?

Answer 13

Assist prime movers (neutralise extra motion)

Question 14

What are fixators?

Answer 14

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

Question 15

What is a compartment?

Answer 15

Limbs are divided into comparments, which are lined and defined by fascia.

Question 16

What is COMPARTMENT SYNDROME?

Answer 16

Trauma in a compartment can cause internal bleeding, which could exert pressure on blood vessels and nerves in the compartment. This can give rise to a variety of symptoms and is called compartment sydrome.

Question 17

What is an isotonic contraction? What are the two types?

Answer 17

Constant tension, variable muscle length Concentric and eccentric

Question 18

What is a concentric isotonic contraction?

Answer 18

Muscle shortens e.g. lifting a load with the arm

Question 19

What is an eccentric contraction?

Answer 19

The muscle exerts a force while being extended

Question 20

What is isometric contraction?

Answer 20

Constant length of muscle, variable tension e.g. hand grip

Question 21

What are three types of muscle fibre?

Answer 21

Type 1, Type IIa and Type IIb

Question 22

What is type I?

Answer 22

High oxidative capacity and are resistant to fatigue. Maintain contractions over long periods of time and are very important in postural muscles.

Question 23

What is type IIb?

Answer 23

Mostly obtain energy via glycolysis and rapidly fatigue

Question 24

What is proprioception?

Answer 24

touches noseFeedback control of movement

Question 25

How is proprioception determined

Answer 25

By special nerve endings known as proprioceptors and muscle spindles in muscles, which sense the degree of stretch and tension in the muscle.

Question 26

Why are muscle spindles clinically useful?

Answer 26

Give rise to some reflexes in the body which can be tested

Question 27

What is a motor unit?

Answer 27

A motor neurone and the muscle fibres that it innervates

Question 28

How many muscle fibres per motor neurone?

Answer 28

Anywhere between 2 and 2000 muscle fibres, depending on degree of fine control required

Question 29

What is cross-talk?

Answer 29

Signalling molecules communicate between nerve and muscle. If one atrophys, so does the other

Question 30

How do muscles increase force generated?

Answer 30

More motor units activated, via process known as recruitment. Termed spacial summation.

Question 31

What aids in recruitment?

Answer 31

Motor neurones, feedback from muscle spindles, joint receptors and golgi tendon organs

Question 32

What is temporal summation?

Answer 32

Increased frequency of action potentials causes summation and tetanus

Question 33

What occurs in tetanus?

Answer 33

Toxin from bacterium clostridium tetani blocks inhibitors motor feedback control which leads to unopposed muscle contraction

Question 34

What is EMG?

Answer 34

Method of measuring electrical activity in muscle, via method known as electromyography

Question 35

How do muscle cells relax?

Answer 35

Ca 2+ pumped back into the SR via Ca 2+ pumpsSome Ca2+ binds to a protein known as calmodulin