2. Skeletal muscle

Question 1

What is the structure of skeletal muscle?

Answer 1

Striated
Multi-nucleated
fused cells
voluntary
myoglobin present

Question 2

What is fasciculation?

Answer 2

Small , local involuntary contraction of muscle

Question 3

What is fibrillation?

Answer 3

Involuntary contraction of individual muscle fibres

Question 4

What are the 3 categories of parallel muscles?

Answer 4

Strap
Fusiform
Fan-shaped

Question 5

What is an example of a strap muscle?

Answer 5

Sartorius

Question 6

What is an example of a fusiform muscle?

Answer 6

Biceps brachii

Question 7

What is an example of a fan-shaped muscle?

Answer 7

Pectoralis major

Question 8

What are the 3 types of pennate muscles?

Answer 8

Unipennate
Bipennate
Multipennate

Question 9

What is an example of a unipennate muscle?

Answer 9

Extensor digitorum longus

Question 10

What is an example of a bipennate muscle?

Answer 10

Rectus femoris

Question 11

What is an example of a multipennate muscle?

Answer 11

Deltoid

Question 12

What is compartment syndrome?

Answer 12

Limbs are divided into compartments by fascia. Trauma in one compartment could cause internal bleeding or swelling which increases pressure on blood vessels and nerves.

Question 13

How is compartment syndrome treated?

Answer 13

Fasciotomy - cutting fascia to relieve pressure

Question 14

What is a motor unit?

Answer 14

An alpha-motor neurone and the muscle fibres it innervates.

Each fibre is innervated by one neurone, but one neurone can innervate many fibres.

Question 15

What is isometric contraction?

Answer 15

A muscular contraction in which the length of the muscle does not change despite being under tension.

Question 16

What is isotonic contraction?

Answer 16

A muscular contraction in which the length of the muscle changes.

Question 17

How is isotonic contraction categorised?

Answer 17

Concentric - muscle shortens e.g bicep in flexion

Eccentric - muscle lengthens e.g bicep in extension

Question 18

What is an example of a first class lever?

Answer 18

Very few in body

Flexion and extension of the head at the neck

Question 19

What is an example of second class lever?

Answer 19

Plantar flexion of foot

Question 20

What is an example of a third class lever?

Answer 20

Biceps brachii

Most common in the body

Question 21

What determines the power of a muscle?

Answer 21

Higher number of fibres per motor unit

Question 22

What determines the fine control of a muscle?

Answer 22

Lower number of fibrils per motor unit

Question 23

What are the 3 main types of muscle fibre, what is this based on?

Answer 23

Slow type 1
Fast type 2a
Fast type 2x
based on myosin heavy chain expression
Each muscle has a different proportion of fibres depending on function.

Question 24

What are the properties of type 1 muscle fibres?

Answer 24

• Slow oxidative
• aerobic
• high myoglobin
• many mitochondria
• rich capillary supply
• fatigue resistant

Question 25

Which muscle fibres are the first to be recruited?

Answer 25

Type 1

Question 26

What movements/actions utilise type 1 muscle fibres?

Answer 26

Standing | Walking

Question 27

What are the properties of type 2a muscle fibres?

Answer 27

- fast oxidative - aerobic - high myoglobin - many mitochondria - moderate fatigue

Question 28

What muscle fibres are the second to be recruited?

Answer 28

Type 2a

Question 29

What actions utilise type 2a fibres?

Answer 29

Walking, running

Question 30

What are the properties of type 2x muscle fibres?

Answer 30

- fast glycolytic - anaerobic - low myoglobin - few mitochondria - rapidly fatigue

Question 31

What muscle fibres are the last to be recruited? During what type of exercise?

Answer 31

Type 2x | Running, sprinting, jumping

Question 32

What are intrafusal muscle fibres?

Answer 32

Muscle spindles within the muscle belly that act as proprioceptors and sense stretch. Separated form rest of muscle by collagen sheath.

Question 33

Explain the innervation if intrafusal fibres.

Answer 33

Innervated by 2 sensory and 1 motor neurone: - Gamma motor neurone keeps fibres taught - Type 1a sensory neurones relay rate of change in muscle length to CNS - Type 2 sensory neurones provide position sense.

Question 34

What will patients with large fibre sensory neuropathy be unable to do?

Answer 34

Impeded output from muscle spindles, unable to perform accurate movement without visual input (e.g eyes closed)

Question 35

What are the 2 main ways to control muscle force?

Answer 35

1. Size principle | 2. Rate code

Question 36

Explain the size principle.

Answer 36

``` Small motor neurones are recruited before large motor neurones.Motor units with most fibre types: Slow type 1 (smallest) first Fast 2a Fast 2x (largest) last. ```

Question 37

Explain the rate code.

Answer 37

More action potentials increase the force produced. | Subsequent AP produce summation up to a limit.

Question 38

What is hypotonia?

Answer 38

Symptom of lack of normal basal skeletal muscle tone. | Most common in babies after birth (floppy baby syndrome)

Question 39

Why is the resting membane potential of skeletal muscle more negative than other cells?

Answer 39

Also have a high concentration of Cl- leak channels (Cl- has negative equilibrium potential).