Session 2-Skeletal Muscle

Question 1

What are the functions of skeletal muscle? (4)

Answer 1

1) movement
2) posture
3) joint stability
4) heat generation

Question 2

Define fasciculation

Answer 2

Small, local, involuntary muscle contractions and relaxations

Question 3

What do circular muscles act as?

Answer 3

Sphincters to adjust opening

Question 4

True or false: circular muscles are arranged in concentric fibres

Answer 4

TRUE

Question 5

Where do circular muscles attach?

Answer 5

To skin, ligaments and fascia rather than bone

Question 6

What is the name of the circular muscles surrounding the eyes?

Answer 6

Orbicularis occuli

Question 7

What is the name of the circular muscle surrounding the mouth?

Answer 7

Orbicularis oris

Question 8

Which is the most common type of skeletal muscle?

Answer 8

Parallel muscles

Question 9

What are the three main categories of parallel muscles?

Answer 9

1) strap
2) fusiform
3) fan shaped

Question 10

What is another name for fan shaped muscles?

Answer 10

Convergent

Question 11

Give an example of a strap muscle

Answer 11

Sartorius (lower limb)

Question 12

Give an example of a fusiform muscle

Answer 12

Biceps brachii

Question 13

Give an example of fan shaped muscle

Answer 13

Pec major

Question 14

What are pennate muscles?

Answer 14

One or more aponeuroses run through muscle body from the tendon, fascicles attach to aponeuroses at an angle

Question 15

What are the three different types of pennate muscles?

Answer 15

1) unipennate
2) bipennate
3) multipennate

Question 16

True or false: a muscle’s insertion is more stable than its origin

Answer 16

FALSE - other way round

Question 17

What delineates the compartments of the limbs?

Answer 17

Fascia

Question 18

What could trauma in one compartment cause?

Answer 18

Internal bleeding which exerts pressure on blood vessels and nerves, giving rise to compartment syndrome

Question 19

How can compartment syndrome be treated?

Answer 19

Fasciotomy (relieves pressure)

Question 20

What are the symptoms of compartment syndrome? (4)

Answer 20

1) pain
2) paresthesia (pins and needles)
3) swollen, shiny skin (bruising)
4) compartment may feel tense and firm

Question 21

What does a muscle agonist do?

Answer 21

Prime mover-main muscle responsible for a particular movement

Question 22

What does a muscle antagonist do?

Answer 22

Opposes prime movers

Question 23

Why are muscle antagonists necessary?

Answer 23

Fine control

Question 24

What do muscle synergists do?

Answer 24

Assist prime movers

Question 25

What do muscle neutralisers do?

Answer 25

Prevent unwanted actions that an agonist can perform

Question 26

What do muscle fixators do?

Answer 26

Stabilise a joint - holds a body part immobile whilst another body part is moving

Question 27

What are the two types of skeletal muscle contraction?

Answer 27

1) Isotonic-constant tension, variable muscle length | 2) Isometric-constant length, variable tension

Question 28

What are the two types of isotonic contraction?

Answer 28

1) Concentric-muscle shortens (eg lifting a load with the arm) 2) Eccentric-muscle resists extension (eg walking downhill)

Question 29

True or false: in a first class lever, the effort is at one end and load at the other

Answer 29

TRUE

Question 30

Which is the most efficient type of lever?

Answer 30

First class

Question 31

What is an example of a first class lever?

Answer 31

Extension/flexion of the head

Question 32

True or false: in a second class lever, the effort is between the load and fulcrum

Answer 32

FALSE - that is in the third class lever. In a second class lever, the effort is at one end and the fulcrum at the other

Question 33

Give an example a second class lever

Answer 33

Plantar flexion of the foot

Question 34

Give an example of a third class lever

Answer 34

Biceps brachii in the flexion of the elbow

Question 35

What happens in rigor mortis?

Answer 35

If ATP is depleted, myosin heads cannot detach. Approx 3 hours after death, body reaches maximum stiffness

Question 36

Complete the sentence: Muscle fibres making up a motor unit are all of the _______ contractile type so each motor unit is fast or slow contracting

Answer 36

Same

Question 37

True or false: each individual muscle fibre is innervated by one motor neuron

Answer 37

TRUE

Question 38

How many different myosin heavy chains (MHC) are there?

Answer 38

8 different isoforms

Question 39

What are the three main types of fibre types in skeletal muscle?

Answer 39

1) Slow type I (beta cardiac) 2) Fast type IIA 3) Fast type IIX

Question 40

What are type I muscle fibres known as?

Answer 40

Slow oxidative

Question 41

What are type IIA muscle fibres known as?

Answer 41

Fast oxidative

Question 42

What are type IIX muscle fibres known as?

Answer 42

Fast glycolitic

Question 43

True or false: type IIA muscle fibres have few mitochondria and carry out anaerobic glycolysis

Answer 43

FALSE - ^ is type IIX

Question 44

Complete the sentence: ___________ muscle fibres facilitate proprioception

Answer 44

Intrafusal

Question 45

What are patients with large-fibre sensory neuropathy unable to do?

Answer 45

Perform accurate movements in the absence of vision

Question 46

What innervates intrafusal muscle fibres?

Answer 46

Two sensory and one motor axons

Question 47

What does the gamma motor neurone do?

Answer 47

Alters sensitivity of the fibres and keeps the fibres taut

Question 48

What do type Ia sensory neurones do?

Answer 48

Relay the rate of change in muscle length back to the CNS

Question 49

What do type II sensory neurones do?

Answer 49

Provide position sense

Question 50

What two factors control muscle force?

Answer 50

1) size principe-small motor neurones recruited before large | 2) rate code-more action potentials=more force. Subsequent action potential produce summation up to a limit (=tetani)

Question 51

True or false: healthy muscles never fully relax

Answer 51

TRUE

Question 52

When is the only time healthy muscles relax?

Answer 52

In REM (rapid eye movement) sleep because part of the brain controlling muscle tone stops working

Question 53

What is baseline muscle tone due to? (2)

Answer 53

1) motor neurone activity | 2) muscle elasticity

Question 54

What is hypotonia?

Answer 54

Lack of skeletal muscle tone

Question 55

True or false: hypotonia is most common in babies and is called floppy baby syndrome

Answer 55

TRUE

Question 56

What can cause hypotonia?

Answer 56

Damage to motor cortex or cerebellum or spinal cord OR degeneration of muscle (myopathy)

Question 57

Where do DHP receptors come into contact with SR?

Answer 57

At triads

Question 58

Which Ca2+ release channels in SR are closely associated with DHP receptors, allowing rapid signalling from action potential to Ca2+ release?

Answer 58

Ryanodine receptors

Question 59

True or false: skeletal muscle fibres only have leaky K+ channels

Answer 59

FALSE - also have high concentration of Cl- leak channels

Question 60

What is a common example of a channelopathy?

Answer 60

Cystic fibrosis

Question 61

What does myotonia mean?

Answer 61

Inability to relax muscles at will

Question 62

What are the symptoms of myotonia congenita?

Answer 62

Muscle stiffness and hypertrophy

Question 63

What causes myotonia congenita?

Answer 63

Mutations in chloride channel CLCN1

Question 64

What type of drugs can relieve symptoms of myotonia congenita?

Answer 64

Anticonvulsant drugs

Question 65

True or false: there are both recessive and dominant forms of myotonia congenita

Answer 65

TRUE

Question 66

In skeletal muscle, what is the resting membrane potential usually equal to?

Answer 66

Cl- Nernst equilibrium potential

Question 67

What are the sources of ATP in muscle? (4)

Answer 67

1) short term stores of ATP in muscle fibre 2) creatine phosphate (short term) 3) glycolysis 4) oxidative phosphorylation

Question 68

What does anaerobic glycolysis form?

Answer 68

Lactate