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Physiology 1 > Muscle Contraction > Flashcards

Muscle Contraction Flashcards

1
Q

What causes Myasthenia gravis?

A

It is autoimmune and it is caused by defects in signalling from nerve to muscle at neuromuscular junctions

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2
Q

What is contraction ?

A

The ability of a muscle to actively shorten and develop tension

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3
Q

What is skeletal muscle attached to?

A

Bone via a tendon

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4
Q

What makes up muscle ?

A 
Muscle
Fasciculus
Fibre/Cell
Myofibril
Sarcomere
Filaments
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5
Q

What are the thick and thin filaments ?

A

Thick - myosin

Thin - actin

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6
Q

When are H bands and I bands at maximum width?

A

In a relaxed muscle

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7
Q

What disappears in a fully contracted muscle ?

A

The H zone

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8
Q

What remains unchanged during muscle contraction and relaxation ?

A

A band width

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9
Q

What are T tubules important for ?

A

Spread of the AP across the membrane

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10
Q

What is stored in the sarcoplasmic reticulum ?

A

Calcium ions

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11
Q

Where do ATP and actin bind to myosin ?

A

At the double head

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12
Q

How could you describe the actin filament ?

A

Double stranded F-actin molecules comprising polymerised G-actin molecules

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13
Q

What regulatory protein is on the actin filament ?

A

Tropomyosin

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14
Q

What regulatory proteins lies on the tropomyosin ?

A

Troponin

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15
Q

Why is troponin important ?

A

This is where calcium binds enabling the muscle to contract

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16
Q

What happens when there is low Ca++ in the cell?

A

Tropomyosin blocks access to the myosin binding site of actin

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17
Q

What happens when troponin binds to Ca++?

A

There is a structural change which allows myosin to access its binding site on actin

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18
Q

What does the hydrolysis of ATP produce ?

A

ADP and Pi

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19
Q

What is released and what forms when myosin head attaches to myosin-binding site on actin?

A

Phosphate is released

Cross-bridge forms and myosin head pivots from 90-45

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20
Q

In the sliding filament hypothesis what causes actin to slide past myosin?

A

After the release of ADP, the cross-bridge generates force which causes actin to slide past myosin

21
Q

What causes the cross bridge to detach ?

A

When another ATP is bound

22
Q

What is the optimal length of a sarcomere ?

A

2.1-2.2 microns

23
Q

Why are sarcomere usually at optimal length in the body ?

A

Tendon attachment

24
Q

What happens at the neuromuscular junction?

A

Nerve and muscle cells are meeting and that incites that excitation which generates the high calcium conditions

25
Q

What does acetylene choline bind to and what does this cause?

A

Nicotinic receptor

Opens receptor-operated channels, inward current produces local depolarisation (a graded potential)

26
Q

How does the local currents depolarise the muscle membrane ?

A

Influx of Na+ ions

27
Q

Where does the AP flow?

A

Via the T-tubules

28
Q

What senses the T tubules during muscle contraction ?

A

Dihydropyridine receptors (L-type channels)

29
Q

What do L-type channels trigger?

A

Ca++ release channels on sarcoplasmic reticulum to open and realise Ca++ init sarcoplasm

The channels are called ryanodine receptors

30
Q

What happens during Rigor Mortis?

A

Ca++ leak out after death of the SR into the cell enabling actin-myosin binding however no ATP is synthesise and therefore cross-bridges cannot detach

31
Q

What does the total force produced by single muscle fibre depend on?

A

The rate of muscle fibre stimulation by motor nerve

32
Q

What does 2 close APs cause ?

A

Wave summation

33
Q

What do a number of APs that are relatively close together cause?

A

Unfused tetanus

34
Q

What do a number of APs that are very very close together cause?

A

Fused tetanus

35
Q

What is an isotonic contraction ?

A

Constant tension

Change in length

36
Q

What are the two types of isotonic contractions ?

A

Concentric - muscle shortens

Eccentric - muscle lengthens

37
Q

What is an isometric contraction ?

A

Constant length

Produces tension

38
Q

What are the 3 types of skeletal muscle fibres ?

A

Type I - slow
Type IIA - fast
Type IIB - fast

39
Q

Describe slow twitch type I muscle fibre.

A
  • postural muscle of back
  • slow, sustained contractions required
  • oxidative metabolism
  • many mitochondria
  • red - myoglobin
  • resist fatigue
40
Q

Describe fast twitch type IIA muscle fibre.

A
  • soleus in calf
  • fast contraction
  • oxidative metabolism
  • many mitochondria
  • red-pink myoglobin
  • intermediate fatigue resistance
41
Q

Describe fast twitch type IIB muscle fibre.

A
  • extraocular muscle
  • rapid contractions
  • anaerobic glycolysis
  • few mitochondria
  • white - little myoglobin
  • high glycogen content
42
Q

What are the two types of smooth muscle ?

A

Single unit smooth muscle

Multi unit smooth muscle

43
Q

What are T-tubules called in smooth muscle ?

A

Caveolae

44
Q

What does Ca++ bind to in smooth muscle contraction ?

A

Calmodulin

45
Q

What type of muscle doesn’t have spontaneous activity ?

A

Skeletal muscle

46
Q

What muscle has MLCK?

A

Smooth muscle

47
Q

List the types of muscles from fastest and slowest contraction speed.

A

Skeletal
Cardiac
Smooth

48
Q

Where can CA++ be found in Cardiac and smooth muscle ?

A

SR and ECF

Physiology 1 (2 decks)

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