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GOATED BRS > Muscular contraction+microstructure > Flashcards

Muscular contraction+microstructure Flashcards

1
Q

How is smooth muscle controlled?

A

Involuntary control from ANS

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2
Q

How is cardiac muscle controlled?

A

Circulating chemicals and ANS

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3
Q

How is skeletal muscle controlled?

A

Voluntary control-To bring about movement

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4
Q

Label types of muscle fibres

A

Parallel
Fusiform
Triangular

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5
Q

Label types of muscle fibre

A

Unipennate
Bipennate
Multipennate

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6
Q
A
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7
Q
A
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8
Q

What is the present in the sarcoplasm?

A

Myoglobin
Mitochondria

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9
Q

What are myofibres composed of?

A

Myofilaments(Actin, myosin)

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10
Q

What is the Z-disc?

A

Actin base chain-separate sarcomeres

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11
Q

What is the H-zone?

A

Zone where only myosin is present

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12
Q

Diameter of a myofibril

A

1-2um

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13
Q

Do myofilaments and myofibrils extend along the whole length of the myfibres?

A

Myofilaments don’t
Myofibrils do

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14
Q

What is the A-band?

A

Whole length of actin chain

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15
Q

What is the I-band

A

Zone with only actin

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16
Q

What is the structure of a myosin filament?

A

2 globular heads
Single tail formed by 2 a-helices
-Several hundred form 1 filament

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17
Q

What 2 other molecules exist on the actin chain?

A

Troponin
Tropomyosin

18
Q

What occurs to the H zone, I band and A-zone during contraction

A

H zone decreases/disappears
I band decreases
A band stays same

19
Q

What enzyme breaks down ACh in an NM junction

A

Acetylcholine esterase

20
Q

How is the ryanodine receptor opened?

A

Dihydropyridine (DHP) receptor in T-tubule membrane: senses ΔV & changes shape of the protein linked to ryanodine receptor

21
Q

How do muscle contractions stop through Ca2+ removal?

A

Ca2+ is actively transported into the SR continuously while action potentials continue. ATP- driven pump (uptake rate < or = release rate).

22
Q

For muscle contraction control, where are the upper and lower motor neurones?

A

Upper-brain
lower-Brainstem and spinal cord

23
Q

Approximately how many neurones and muscle fibres do humans have?

A

Humans have approximately 420,000 motor neurons and 250 million skeletal muscle fibres.

24
Q

Roughly how many muscle fibres does each motor neurone innervate/

A

600

25
Q

What does stimulation of a motor unit lead to?

A

Contraction of all the muscles innervated by that motor neurone

26
Q

What does this table show?

A

Huge variation in ratio of neurone to muscle fibres innervated

27
Q

Characteristics of a Type I motor unit

A

Slow
smallest diameter cell bodies
small dendritic trees
thinnest axons
slowest conduction velocity

28
Q

Characteristics of a Type IIa motor unit

A

Fast fatigue resistant
larger diameter cell bodies
larger dendritic trees
thicker axons
faster conduction velocity

29
Q

Characteristics of a Type IIb motor unit

A

Fast fatiguable
larger diameter cell bodies
larger dendritic trees
thicker axons
faster conduction velocity

30
Q
A
31
Q

What method can tell you the variety in muscle fibre types?

A

ATPase staining method

32
Q

How are motor units classified?

A

Tension generated
Speed of contraction
Fatiguability of the motor unit

33
Q

Generally what order are motor units recruited in?

A

Slow
Fast fatigue resistant
Fast fatiguable

34
Q

Outline the 2 methods by which motor unit activation is regulated?

A

Recruitment
Smaller motor units are recruited first, as more force is needed more(larger) units are recruited
-Allows for fine movement e.g writing

Rate coding
Slower units fire at a slower frequency
as firing speed increases, force generated increases
-Summation occurs when firing frequency is too fast for the muscle to relax in between contractions

35
Q

2 functions of neurotrophic factors

A

Prevent neuronal death
Promote growth of neurons after injury

36
Q

What occurs if a fast and slow twitch muscle are cross innervated?

A

The slow one becomes fast and vice versa

37
Q

Label types of contraction

A

Isometric
Concentric
Eccentric

38
Q

Outline how ageing affects the proportion of muscle fibre types?

A

Loss of type I and II fibres but also preferential loss of type II fibres. This results in a larger proportion of type I fibres in aged muscle (evidence from slower contraction times).

39
Q

What most likely occurs to muscles in terms of type switching with training?

A

IIB to IIA

40
Q

What can cause a shift from type I to type II muscle fibres?

A

Severe deconditioning
Spinal cord injury
Spaceflight micorgravity

GOATED BRS (57 decks)

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