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Phys, pharm > Muscle > Flashcards

Muscle Flashcards

1
Q

Function of skeletal muscle

A

Controls inspiration by contraction of the diaphragm
Skeletal muscle pump

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2
Q

Structure of skeletal muscle

A

Myofilaments ->
Myofibril ->
Muscle cell/fiber ->
Muscle (fascicle)

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3
Q

What is a sarcomere?

A

An individual unit of myofibrils

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4
Q

Appearance of a muscle cell

A

Striated due to organisation of sarcomeres

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5
Q

How does muscle contraction occur?

A

Myosin heads interact with actin to allow for muscle contraction

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6
Q

Where do actin project from?

A

Z disc

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7
Q

What is the I band?

A

Light
Actin fibres
Gets smaller as the muscle contracts

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8
Q

What is the A band?

A

Dark
Actin and myosin heads overlap here

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9
Q

How is a contraction initiated?

A

Acetylcholine is released and an action potential occurs in the plasma membrane of the muscle fibre ->
A wave of depolarisation goes through the sarcomere, through the t tubule and into the cell interior ->
Depolarisation triggers the release of intracellular calcium

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10
Q

Describe the contraction of a sarcomere

A
  1. ATP binds to myosin head, actin-myosin dissociates
  2. ATP is hydrolysed, myosin heads return to resting
  3. A cross bridge forms, myosin head binds to new position on actin
  4. Pi is released
  5. A conformational change in the myosin head causes a power stroke, filaments slide past each other
  6. ADP is released
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11
Q

Name the stages of actin-myosin cross bridge formation

A

Attached state
Released state
Cocked state
Weak cross bridge state
Strong cross bridge state
Post powerstroke state

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12
Q

How many myosin heads are in a thick filament?

A

300 approx

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13
Q

What are the 3 classes of muscle fibres?

A

Slow oxidative
Fast oxidative
Fast glycolytic

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14
Q

Which classes of muscle fibre are resistant to fatigue?

A

Slow oxidative
Fast oxidative

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15
Q

What colour is a fast glycolytic muscle fibre?

A

White

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16
Q

Example of slow oxidative muscle

16
Q

Example of slow oxidative muscle

17
Q

Example of fast oxidative muscle

A

Gastrocnemius

18
Q

Example of fast glycolytic muscle

A

Biceps brachii

19
Q

How long does a fast muscle fibre take to contract?

A

10msec or less

20
Q

Mechanism of botulinum toxin

A

Muscle weakness/paralysis leading to death

21
Q

Symptoms of botulinum toxin

A
  1. dry mouth and double vision
  2. GI issues
  3. paralysis of limbs and respiratory muscles
22
Q

Name 3 clinical uses of botulinum toxin

A

Treatment of strabismus
Blepharospasm
Cosmetic treatments (botox)

Phys, pharm (31 decks)

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