Muscle Contraction Introduction

Question 1

Describe synaptic transmission from neurone to muscle

Answer 1

=ACh release into synaptic cleft
=Rapidly degraded by Acetylcholinesterase
=AChR binding at motor end plate opens ion-channel
=Na+ influx / K+ efflux causes depolarisation of muscle
=Depolarisation triggers propagation of AP in muscle fibre

Question 2

What are the components of a muscle?

Answer 2

Tendon
Epimysium (connective tissue) 
Perimysium
Endomysium
Fascicle
Muscle fibre

Question 3

Anatomy of a muscle fibre

Answer 3

Repeating unit is the sarcomere
Sarcomere comprises: Z-disc, thick (actin) and thin (myosin) filaments
Actin is blocked from interacting with myosin by tropomyosin, in turn controlled by troponin.

Question 4

Describe muscle contraction

Answer 4

=Ca+ influx binds to troponin and unblocks the action of tropomysosin exposing actin activity sites
=Myosin heads alternatively attach and detach, pulling the actin filaments towards the centre of the sarcomere
=Ca+ actively removed by uptake into the SR
=Tropomyosin block restored

Question 5

What are the types of contraction?

Answer 5

Twitch= single contraction
Wave summation= repeatedly to increase tension
Tetany= maximum contraction

Question 6

What are the physiological types of muscle?

Answer 6

Slow
Fast, fatigue resistant
Fast, fatigable

Question 7

How do we measure muscle function in clinical neurophysiology?

Answer 7

Electromyography= tiny electrodes into muscle