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Musculoskeletal case > Functions of the muscle > Flashcards

Functions of the muscle Flashcards

1
Q

Functions of the muscle 4

A

Movement

Control posture

Remove from blood) and
store glucose

Generate heat (temperature 
regulation)
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2
Q

How is the contractile filament laid out?

A

http://www.ks.uiuc.edu/Research/telethonin/MuscleL1.jpg

Z line/disc

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3
Q

What are the A band and I band referred to as

A

A - dArk A Band

I - lIght I Band

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4
Q

What is the name given to repeating unit of the microfilaments

A

Sarcomere

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5
Q

What is the sarcomere

A

repeating unit of the microfilaments

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6
Q

What happens to the sarcomere when contraction happens?

A

I band filament appears to have shortened but is only obscured by the A band whcih pulls it in
Sarcomere shortens

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7
Q

What are the types of contractions

A

Isotonic

Isometric

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8
Q

What is isometric contraction

A

Constant length
Taking load at a constant length
Tension increases

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9
Q

What is isotonic contraction

A

Constant load

Picking something up changing velocity of load

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10
Q

What is tension

A

Force exerted on an object by a contracting muscle

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11
Q

What is load

A

Force exerted on muscle by the weight of an object

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12
Q

What are the types of isotonic contraction?

A

Concentric

Eccentric

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13
Q

What is eccentric contraction

A

Muscle contracting but lengthening at the same time

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14
Q

What is Concentric contraction

A

Muscle contracting and shortening

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15
Q

How is a muscle stimulated

A

Action potential across Motor neuron synapses onto n muscle at motor endplate

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16
Q

Where are the cell bodies of motor neurons located

A

Ventral horn of spinal cord

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17
Q

What is an action potential

A

A regenerating depolarization of membrane potential that propagates along an excitable membrane

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18
Q

What does regeneration mean?

A

uses energy to move along membrane at constant amplitude

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19
Q

What does propagates mean?

A

Moves along the membrane as an ‘active’ membrane event

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20
Q

What does excitable mean?

A

capable of generating action potential

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21
Q

What is the name given to the measurement of peripheral nerve conduction

A

Extracellular/ transmural

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22
Q

How is excitation clinically detected in the body?

A

Measurement at the body surface

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23
Q

What can record action potentials extracellualrly?

A

ECG
EMG
EEG

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24
Q

Where does EEG measure action potential

A

Brain

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25
Q

Where does ECG measure action potential

A

Heart

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26
Q

Where does EMG measure action potential

A

Skeletal muscles

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27
Q

How does action potential meter work?

A

Electrodes place in two areas
Resting:
Positive membrane potential on outside and no action potential means positive whole way through so no potential difference (0V on voltmeter)
Action potential:
When action potential occurs negative membrane potential relative to inside but area of the nerve where action potential has not reached yet will be negative. So electrode 1 positive electrode 2 negative = potential difference across meter (-V of voltmeter

28
Q

In terms of action potential graph what is depolarisation?

A

Moving towards 0V x-axis

29
Q

In terms of action potential graph what is hyperpolarisation?

A

Moving away 0V x-axis

30
Q

Why is action potential at a synapse one way?

A

Neurotransmitter on end of presynaptic cell to receptors on post-synaptic cell

31
Q

What is a receptor

A

ligand-gated ion channel / receptor- operated channel

32
Q

General Synapse- what happens?

A

AP in pre-synaptic cell causes release of vesicles.
Transmitter diffuses to receptors on post-synaptic cell.
Activation of receptors depolarises (via Na* entry) cell to threshold and initiates an AP in post-synaptic cell.

33
Q

What does a nerve synpase look like? structure real life photo

A

Hand like structure of endplate on muscle fibres

34
Q

If nerve is removed what would the depression be?

A

Primary synaptic cleft and branching from it secondary synaptic clefts which leaves trophs

35
Q

What does a post-synaptic neuron have?

A

Trophs infoldings ‘clefts’

36
Q

Muscle synapse

A

Transmitter released from vesicles at ‘active zones’.
- Active zones aligned with infoldings or ‘clefts’ in the post-junctional membrane.
Top of the clefts = nACh receptors
Bottom of clefts = voltage-gated Na+ channels.

37
Q

What is nACh receptors?

A

nicotine acetylcholine receptors

38
Q

Why is it important that nACh receptors are at the top of the celfts?

A

Minimal distance for diffusion

39
Q

Why is it important that nACh receptors are at the top of the celfts?

A

Minimal distance for diffusion

40
Q

What is important about the Na+ channels being at the bottom of the clefts and not the nACh receptors

A

Activated by voltage change not transmitter, so distance unimportant

41
Q

Name muscle relaxants

A

Botulinum toxin
Curare
Succinylcholine

42
Q

How does Botulinum toxin prevent contraction of the muscles What does this cause?

A

Prevents release of ACh-containing vesicles.

Causes paralysis of muscle and inhibition of secretion from exocrine glands normally stimulated by parasymp NS

43
Q

How does Curare prevent contraction of the muscles What does this cause?

A 
Blocks nAChRs
Cause paralysis (used during surgery to prevent muscle spasm)
44
Q

How does Succinylcholine prevent contraction of the muscles

A

Short-acting block of nAChR (used during intubation)

45
Q

What is Succinylcholine also called?

A

‘suxemethonium’

46
Q

OneDrive Personal > uni > Brainscape pictures > Capture 2

A 
A- Sarcoplasm
B- Sarcolemma (plasmalemma of muscle)	.C-Mitochondria
D- Triad (SR-T-SR)
E- T tubule opening
F- Sarcoplasmic reticulum
G-Diameter of fibre
H-Myofibril
47
Q

What is the function of sarcoplasmic reticulum

A

Ca Store

48
Q

What is the function of T tubules

A

Conduct quickly muscle action potential into fibres

49
Q

What is the role of T tubule and sarcoplasmic reticulum in muscle contraction

A

T-tubules and SR membranes very
T tubule AP stimulates Ca release from SR
Released Ca stimulates contraction
Ca then taken back into SR

50
Q

What T-tubules

A

Tubes continuous with the surface membrane roght through the muscle fibres

51
Q

How calcium is stored and released in the SR?

A

Leaves through channel

Pumped back in using ATP-driven calcium pumps) from low to high conc

52
Q

What is a calcium store in the muscle

A

Sarcoplasmic reticulum

53
Q

How is action potential used spread through muscle fibres

A

Action potential moves along the sarcolemma

goes down into the tunnels where these T tubules are

54
Q

What is the Triad structure

A

T-tuubule + SR on either side

55
Q

How is the action potential lead to calcuim release?

A

Dihydropyridine acts as voltage-sensors on t-tubule membrane
detects voltage change of the action potential and communicate it to -
Ryanodine receptors acts as calcium release channels on SR membrane which when stimulated releases calcium

56
Q

What triggers malignant hyperthermia

A

Volatile anaestetics

57
Q

What causes malignant hyperthermia

A

Mutation in the ryanodine receptor

58
Q

What is the effect of malignant hyperthermia

A

Constant leak of calcium from SR that is matched by increased ATP-dependent calcium pumping

59
Q

What is the treatment of malignant hyperthermia

A

Withdrawal of trigger and dantroline (blocks the ryanodine receptor)

60
Q

Summation

A

Where action potentials are fired quickly so that force is accumulated before going back down
Myoplasmic Ca falls (initiating relaxation) before muscle makes maximum force
therefore Further stimulation before relaxation complete results adding of force (summation)

61
Q

What is it called when there is no relaxation between each calcium rise

A

Fused tetanus or tentanic contraction

62
Q

When does tetanus contraction occur

A

In posture

63
Q

What is in the A band of the microfilament

A

myosin

64
Q

What is in the I band of microfilament

A

actin

65
Q

Full process of Excitation-Contraction Coupling 1-10

A
  1. AP travels across surface of muscle fibre.
  2. AP moves down T tubules
  3. DHP receptors sense voltage change and open ryanodine receptors
  4. Ca2+ ions are released from the SR.
  5. Ca2+ ions bind troponin causing tropomyosin to move and uncover myosin-binding sites on actin.
  6. The cross-bridge cycle drives muscle contraction.
  7. Ca2+ ions are pumped into the SR by the Ca2+-ATPase.
  8. Ca2+ removal from troponin restores tropomyosin inhibition
  9. Actin and myosin no longer form bridges
  10. Muscle relaxes

Musculoskeletal case (8 decks)

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