Skeletal Muscle Physiology 2 02/10/18

Question 1

What do factors does the gradation of skeletal muscle tension depend on?

Answer 1

Number of muscle fibres contracting within the muscle

Tension developed by each contracting muscle fibre

Question 2

What is motor unit recruitment?

Answer 2

A stronger contraction can be achieved by stimulation of more motor units

Question 3

What helps to prevent muscle fatigue?

Answer 3

Asynchronus motor unit recruitment during submaximal contractions

Question 4

What does the tension development of a muscle fibre depend on?

Answer 4

Frequency of stimulation
Summation of contractions
Length of muscle fibre
Thickness of muscle fibre

Question 5

Which is longer, the duration of an action potential or the duration of the resulting twitch?

Answer 5

The muscle twitch

Question 6

How can a stronger contraction be brought about?

Answer 6

Summating twitches through repetitive fast stimulation of skeletal muscle

Question 7

What is tetanus and how is it brought about?

Answer 7

Maximal sustained contraction

When the muscle fibre is stimulated so rapidle that it does not have an opportunity to relax between stimuli

Question 8

Can cardiac muscles be tetanised and why/why not?

Answer 8

No

The long refractory period prevents generation of tetanic contraction

Question 9

What is the resulting action when a skeletal muscle is stimulated once?

Answer 9

Twitch

Tia/Tamera

Question 10

Can a single twitch bring about meaningful muscle activity?

Answer 10

No

Question 11

When the frequency of stimulation increases what happens to the tension?

Answer 11

Increases

Question 12

When is skeletal muscle at its optimal length?

Answer 12

When it is resting

Question 13

How is skeletal muscle tension transferred to bone?

Answer 13

Through tissue and tendons

Question 14

What are the two types of skeletal muscle contraction?

Answer 14

Isotonic contraction

Isometric contraction

Question 15

What is isotonic contraction?

Answer 15

Muscle tension remains the same as the muscle length changes

I.e. in body movements and moving objects

Question 16

What is isometric contraction?

Answer 16

Muscle tension develops at constant muscle length

I.e. supporting objects in fixed position or maintaining body posture

Question 17

What happens to the velocity of muscle shortening as the load increases?

Answer 17

It decreases

Question 18

Are all skeletal muscle fibres the same?

Answer 18

No

Question 19

What are the 3 differences in skeletal muscle fibres?

Answer 19

Enzymatic pathways for ATP synthesis
Resistance to fatigue
Activity of myosin ATPase

Question 20

Which muscle fibres are more resistant to fatigue?

Answer 20

Muscle fibres with a greater capacity to synthesise ATP

Question 21

What does the activity of myosin ATPase determine?

Answer 21

The speed at which energy is made available for cross bridge cycling

Question 22

What are the three types of metabolic pathway that supplies ATP to muscle fibres?

Answer 22

Transfer of high energy phosphate from creatine phosphate to ADP
Oxidative phosphorylation (when O2 is present)
Glycolysis (When O2 is not present)

Question 23

What are the three types of skeletal muscle fibre?

Answer 23

Slow-oxidative (Type 1)
Fast-oxidative (Type 2a)
Fast-glycolytic (Type 2x)

Question 24

What are type 1 fibres mainy used for?

Answer 24

Prolonged, low work aerobic activities

Question 25

What are Type 2a fibres used for?

Answer 25

Aerobic and anaerobic metabolism and prolonged moderate work

Question 26

What are type 2x fibres used for?

Answer 26

Anaerobic metabolism and short term high intensity activities

Question 27

What is the definition of a reflex?

Answer 27

Stereotyped response to a specific stimulus

Question 28

What are the simplest form of coordinated movement?

Answer 28

Reflex actions

Question 29

What are the neural pathways for reflexes important for localising?

Answer 29

Lesions in the motor system

Question 30

What is the simplest monosynaptic spinal reflex?

Answer 30

The stretch reflex

Question 31

Is the stretch reflex positive or negative feedback?

Answer 31

Negative

Question 32

What is the sensory receptor in the stretch reflex and what is it activated by?

Answer 32

Muscle spindle activated by muscle stretch

Question 33

What does stretching the muscle spindle do?

Answer 33

Increases firing in the afferent neurons

Question 34

Where do the afferent neurons synapse and what with?

Answer 34

In the spinal cord with the alpha motor neurons

Question 35

What does activation of the reflex result in?

Answer 35

Contraction of the stretched muscle

Question 36

What coordinates the stretch reflex?

Answer 36

Simultaneous relaxation of antagonist muscle

Question 37

How can the stretch reflex be elicited?

Answer 37

Tapping the muscle tendon with a rubber hammer

Question 38

What nerve and spinal segment are responsible for the Knee jerk?

Answer 38

L3,L4 | Femoral

Question 39

What nerve and spinal segment are responsible for the Ankle jerk?

Answer 39

S1,S2 | Tibial

Question 40

What nerve and spinal segment are responsible for the Biceps Jerk?

Answer 40

C5, C6 | Musculocutaneos

Question 41

What nerve and spinal segment are responsible for the Brachioradialis Jerk?

Answer 41

C5,C6 | Radial

Question 42

What nerve and spinal segment are responsible for the Triceps Jerk?

Answer 42

C6-C7 | Radial

Question 43

What are muscle spindles?

Answer 43

Sensory receptors for stretch reflex

Question 44

What are muscle spindles a collection of?

Answer 44

Specialised muscle fibres

Question 45

What are muscle spindles known as?

Answer 45

Intrafusal fibres

Question 46

What are ordinary muscle fibres known as?

Answer 46

Extrafusal fibres

Question 47

What direction do muscle spindles and fibres run in?

Answer 47

Parallel

Question 48

What are the sensory nerve endings on muscle spindles known as?

Answer 48

Annulospiral fibres

Question 49

As the muscle is stretched, what happens to the discharge from muscle spindles?

Answer 49

It increases

Question 50

Do muscle spindles have their own efferent motor nerve supply?

Answer 50

Yes

Question 51

What are the efferent neurones that supple the muscle spindles called?

Answer 51

Gamma motor neurons

Question 52

Does the contraction of intrafusal fibres contribute to the overall strength of the muscle?

Answer 52

no

Question 53

What are 4 causes of impairment of skeletal muscle function?

Answer 53

Intrinsic muscle disease Disease of the NMJ Disease of lower motor neurons Disruption of input to motor nerves

Question 54

What are some causes of intrinsic muscle disease?

Answer 54

``` Genetic -Congenital -Muscular dystrophy -Myotonia Acquired -Inflammatory -Non-inflammatory (fibromyalgia) -Endocrine (cushings) -Toxic (alcohol) ```

Question 55

What are 4 symptoms of muscle disease?

Answer 55

Muscle weakness Delayed relaxation Muscle pain Muscle stiffness

Question 56

What are some useful investigations for neuromuscular disease?

Answer 56

``` Electromyography Nerve conduction studies Muscle enzymes Inflammatory markers Muscle biopsy ```