Muscles

Question 1

What’s a fasciculation

Answer 1

Small, local, involuntary skeletal muscle contraction and relaxation (twitch)

Question 2

Describe the origin of a skeletal muscle

Answer 2

Bone
Usually proximal
Greater mass and more stable during contraction than the insertion

Question 3

Describe the insertion of a skeletal muscle

Answer 3

Bone, tendon or CT
Usually distal
Usually moved by contraction

Question 4

What are the 3 arrangements of skeletal muscle

Answer 4

Circular
Parallel
Pennate

Question 5

Describe circular skeletal muscle

Give examples

Answer 5

Fibres form concentric rings around sphincter or opening

Orbicularis occuli, orbicularis oris

Question 6

What do circular skeletal muscles attach to

Answer 6

Skin
Ligaments
Fascia of other muscles

Question 7

Describe parallel skeletal muscles

Answer 7

Fibres run parallel to force generating axis

Question 8

What are the types of parallel skeletal muscle

Give an example of each

Answer 8

Strap - sartorius
Fusiform - biceps brachii
Fan shaped/convergent - Pectoralis major

Question 9

Describe Pennate skeletal muscle

Answer 9

Has 1 or more aponeuroses through muscle body from tendon

Fascicles attach to aponeuroses at an angle (pennation angle) to direction of movement

Question 10

Types of Pennate skeletal muscle

Give an example of each

Answer 10

Unipennate (fascicles on same side as tendon) - extensor digitorum longus
Bipennate (fascicles on both sides of tendon) - rectus femoris
Multipennate (central tendon branches) - deltoid

Question 11

What separates compartments of muscle

Answer 11

Fascia

Question 12

What is compartment syndrome

Answer 12

Bleeding within compartment exerts pressure on nerves and blood vessels

Question 13

Symptoms of compartment syndrome

Answer 13

Constant poorly localised pain
Paresthesia 
Compartment feels tense 
Swollen shiny skin
Bruising and blistering 
Prolonged capillary refill time

Question 14

Treatment of compartment syndrome

Answer 14

Fasciotomy

Question 15

Define agonist

Answer 15

Main muscle responsible for a particular movement

Question 16

Define antagonist

Answer 16

Opposes action of agonist

Question 17

Define synergist

Answer 17

Assists agonist

Acting alone it can’t perform the movement of the agonist

Question 18

Define neutraliser

Answer 18

Prevents unwanted actions that an agonist performs

Example: rotator cuff muscles prevent shoulder Flexion during elbow Flexion (biceps brachii)

Question 19

Define fixator/stabiliser

Answer 19

Holds a body part immobile whilst another is moving

Question 20

What are the types of muscle contraction

Answer 20

Isotonic contraction
Isometric contraction
Passive stretch

Question 21

Describe isotonic contraction

Answer 21

Tension is constant

Muscle length changes

Question 22

Types of isotonic contraction (describe)

Answer 22

Concentric - muscle shortens

Eccentric - muscle exerts force while extending

Question 23

Effect of eccentric isotonic contraction

Answer 23

Damages muscles and causes delayed onset muscle pain

Question 24

Describe isometric contraction

Answer 24

Muscle length is constant

Tension changes

Question 25

When does isometric contraction occur

Answer 25

Load against muscle equals contractile force being generated E.g. Holding weight in fixed position

Question 26

Describe passive stretch | Give an example

Answer 26

Muscle is lengthened while in passive state | Example: hamstrings lengthen when touching toes

Question 27

``` Describe first class lever Give example ```

Answer 27

Effort at one end, load at other end | Extension/Flexion of head

Question 28

``` Describe second class lever Give an example ```

Answer 28

Effort at one end, load between effort and fulcrum | Plantar Flexion of foot

Question 29

``` Describe third class lever Give an example ```

Answer 29

Effort between load and fulcrum | Lifting weight

Question 30

What's a motor unit

Answer 30

Alpha motor neurone and muscle fibres it innervates (connected by neuromuscular junction)

Question 31

Demonstrate with examples the variety in muscle fibre number in motor units

Answer 31

Muscles that produce precise movements have few muscle fibres - inferior rectus has 9 Powerful movements have lots of muscle fibres - gastrocnemius has 2000

Question 32

How do types of muscle fibres differ

Answer 32

Myosin heavy chain expression

Question 33

What are the main types of muscle fibre

Answer 33

Slow oxidative type 1 Fast oxidative type 2a Fast glycolytic type 2x

Question 34

What's the significance of the muscle fibres in each motor unit

Answer 34

All the same type | Therefore a motor unit is either fast, intermediate or slow contracting

Question 35

Properties of type 1 muscle fibres

Answer 35

``` Aerobic High myoglobin Red Many mitochondria Rich capillary supply Fatigue resistant Recruited in standing and walking ```

Question 36

Properties of type 2a muscle fibres

Answer 36

``` Aerobic High myoglobin Red/pink Many mitochondria Rich capillary supply Moderate fatigue resistance Recruited in walking and running ```

Question 37

Properties of type 2x muscle fibres

Answer 37

``` Anaerobic Low myoglobin Pale Few mitochondria Poorer capillary supply Rapidly fatiguable Recruited in running, sprinting and jumping ```

Question 38

What factors control contractile force

Answer 38

Size principle | Rate code

Question 39

Describe size principle

Answer 39

Small motor neurones are recruited before larger ones Therefore motor units are recruited in order of: Slow type 1 Fast type 2a Fast type 2x

Question 40

Describe rate code and summation

Answer 40

More APs gives higher contractile force Subsequent APs results in summation giving a slightly larger contractile force with each contraction. Limit where no further force can be produced is called tetany

Question 41

What causes baseline muscle tone

Answer 41

Elasticity of muscle | Low level of motor neurone activity

Question 42

What controls skeletal muscle tone

Answer 42

Motor control centres in brainstem

Question 43

What is hypotonia

Answer 43

Lack of skeletal muscle tone

Question 44

Causes of hypotonia

Answer 44

Cerebellum lesions Lesions of sensory afferents from muscle spindles Lower motor neurone lesions Degeneration of muscle

Question 45

Describe excitation contraction coupling

Answer 45

ACh release at neuromuscular junction opens L-type calcium channels in T tubules These channels are in close association with ryanodine receptors in SER Ryanodine receptors are activated by calcium influx Calcium is released into sarcolemma and binds to troponin Bonding sites on actin are revealed

Question 46

Describe malignant hyperthermia

Answer 46

Rare dominant condition triggered by volatile anaesthetic agents and succinylcholine

Question 47

Effect of malignant hyperthermia

Answer 47

Uncontrolled increase in oxidative metabolism and resulting increase in body temperature Increase in intracellular Ca leads to increased rate of SERCA which leads to massive heat production

Question 48

Treatment of malignant hyperthermia

Answer 48

Dantrolene | Antagonist of ryanodine receptor

Question 49

Most common cause of malignant hyperthermia

Answer 49

Polymorphism (2 or more alleles at 1 locus) in ryanodine receptor

Question 50

What is myotonia

Answer 50

Inability to relax muscles at will

Question 51

Symptoms of myotonia congenita

Answer 51

Muscle stiffness enhanced by cold/inactivity and relieved by exercise Muscle hypertrophy

Question 52

Cause of myotonia congenita

Answer 52

Mutations in chloride channel (CLCN1)

Question 53

What are intrafusal muscle fibres

Answer 53

Type of muscle fibre that facilitates proprioreception (unconscious perception of own body's movement and spacial orientation) Contains muscle spindle

Question 54

What are muscle spindles

Answer 54

Sensory receptors in belly of intrafusal muscle fibres that respond to muscle stretch/length

Question 55

Innervation of intrafusal fibres and function of neurones

Answer 55

Gamma motor neurone - keep fibres taught Type 1a sensory neurone - relays rate of change in muscle length to CNS Type 2 sensory neurone - provides position sense

Question 56

What happens in patients with large fibre sensory neuropathy

Answer 56

Can perform accurate movements with eyes open but with eyes closed they are grossly inaccurate

Question 57

Functions of skeletal muscle

Answer 57

Movement Posture Joint stability Thermogenesis

Question 58

What is sarcopenia

Answer 58

Loss of muscle mass due to loss of muscle fibres and reduced muscle cross sectional area