Muscle Physiology Flashcards Preview

BMS242 - Phys/Pharm of Cells > Muscle Physiology > Flashcards

Flashcards in Muscle Physiology Deck (93)
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1

Recall the divisions of a muscle from largest to smallest?

Muscleà Muscle Fascicle à Muscle Fibre/Cell à Myofibril à Sarcomere à Myofilaments

2

What is defined as one sarcomere?

The length/distance between two successive Z-lines

3

What determines the degree of contraction in muscle?

Degree of overlap between the actin and myosin filaments

4

What is meant by the motor unit of a muscle?

The motor neuron and the muscle fibre it innervates

5

One motor neuron innervates a single muscle fibre, T or F?

F – one motor neuron innervates several muscle fibres

6

What attribute of motor units’ accounts for the ability to finely control muscle contraction?

Finer control of muscle contraction comes from the motor units where one motor neuron innervates a smaller number of muscle fibres

7

A single muscle has multiple motor units, T or F?

T

8

Which type of postsynaptic receptor is found on muscle cells and what class of receptor is it?

nAchR – ligand-gated ion channel

9

The skeletal muscle action potential has a very short duration, T or F?

T

10

At rest the membrane potential of skeletal muscle is more positive than normal due to open CLC1 and voltage-gated K+ channels, T or F?

F – membrane potential is very negative

11

Which channels mediate depolarisation in the action potential?

Na+ channels

12

Which channels mediate repolarisation during the action potential?

K+ channels

13

There are different types of K+ channel that mediate the resting membrane potential and the repolarisation phase of the action potential, T or F?

T

14

nAchRs are Na+ ion channels, T or F?

F – they are cation selective but allow both Na+ and K+ through

15

Activation of the nAchRs causes depolarisation, T or F?

T

16

Describe the subunit composition of nAchRs?

Describe the subunit composition of nAchRs? nAchRs are pentameric structures consisting of 2α subunits, and 1 β, γ and δ subunit

17

What can be said about the acetylcholine binding site(s) of nAchRs?

There are two binding sites for acetylcholine that lie at the interface between the α and γ subunits. This means that two acetylcholine molecules have to be bound to the receptor before the ion channel opens

18

How many transmembrane domains are there in the nAchR?

4

19

What allows for the vast array of different nAchRs?

There are different types of each subunit

20

Describe the gating process of nAchRs?

Closed with no agonists bound à closed with one agonist bound à closed with two agonists bound à open

21

What type of disease is myasthenia gravis?

Autoimmune disease

22

What are the symptoms of myasthenia gravis?

Weakness and tiredness in the skeletal muscle

23

What is the cause of myasthenia gravis?

Inappropriate antibodies against postsynaptic AchRs at the neuromuscular junction that prevent acetylcholine binding

24

What difference is seen in males and females with myasthenia gravis?

Female age of onset in much earlier (30s) whereas in males it occurs in 60s-70s

25

How can myasthenia gravis prove fatal?

Respiratory failure due to inability of the muscles to contract

26

Acetylcholinesterase inhibitors are used in the treatment of myasthenia gravis, how do these work?

By inhibiting acetylcholine breakdown you can prolong the effects of released acetylcholine allowing it to bind to the still functioning AchRs

27

How are corticosteroids effective in treating MG?

They are immunosuppressants that reduce levels of antibodies

28

Another treatment method for MG is using intravenous antibodies, how do these work?

They bind to the AchR antibodies and prevent them from binding to the receptors themselves

29

List two other treatment methods for MG?

Plasmaphoresis, thymectomy

30

What is meant by the muscle triad?

Structure consisting of the sarcoplasmic reticulum on both sides of a transverse tubule (T-tubule)