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Physiology & Pharmacology > The Muscular System > Flashcards

The Muscular System Flashcards

1
Q

Functions of skeletal muscle

A
  • Produce movement of body parts
  • Support soft tissues
  • Maintain body posture and body position
  • Communication
  • Control of openings and passage ways
  • Maintain body temerature
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2
Q

Universal characteristics of muscles

A
  • Reponsiveness
  • Conductivity
  • Contractility
  • Extensibility
  • Elasticity
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3
Q

What are myofibrils surrounded by?

A

Epimysium

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4
Q

How many heads does each myosin filament have?

A

About 300 heads

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5
Q

How many cycles does a head go through each second?

A

About 5

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6
Q

What does Cap Z do? Where is it present?

A

Caps actin polymerisation. Present on Z disc/line

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7
Q

What does nebulin do?

A

Binds to actin and acts as a molecular ruler to establish the length of the actin filament

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8
Q

What does tropomodulin do?

A

Caps depolymerisation on actin on minus end

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9
Q

Which end of actin is at the Z discs/lines?

A

Plus end

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10
Q

What does titin do?

A

Acts as a spring. Folds and unfolds for myosin

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11
Q

Sarcomere: Power stroke

A
  1. ATP binds to myosin head, causing dissociation of the actin-myosin complex
  2. ATP hydrolysed –> myosin head returns to resting conformation
  3. Cross-bridge forms and myosin head binds to new position on actin
  4. P is released. Myosin heads change conformation –> power stroke
  5. ADP is released
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12
Q

How is a contraction initiated?

A
  1. Nerve impulse reaches neuromuscular junction. Ca2+ channels open and influx of Ca2+ causes release of Each by exocytosis
  2. Binding of ACh to post-synaptic receptors causes Na+ channels to open and Na+ enters sarcoplasm which results in AP
  3. Ca2+ released by sarcoplasmic reticulum and binds to troponin –> conformational change which displaces tropomyosin thus unmasking myosin binding sites
  4. Myosin heads slide along actin filament - requires ATP
  5. Process terminates when nerve impulse stops. ACh then degraded by acetylcholinesterase. Ca2+ reabsorbed and detaches from troponin
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13
Q

What do calcium ions bind do in the sarcomere?

A

Troponin (C)

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14
Q

Give an example of a chemical that blocks Na+ channels

A

Tetrodotoxin

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15
Q

Give an example of a chemical that blocks Ca2+ channels

A

omega-Conotoxin

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16
Q

Give an example of a chemical that blocks K+ channels

A

Dendrotoxin

17
Q

Give an example of a chemical that stops ACh release

A

Tetanus toxin

Botulinum toxin

18
Q

Give an example of a chemical that blocks AChR channels

A

d-Tubocurarine

19
Q

What does dendrotoxin act on?

A

K+ channels

20
Q

What is botulinum toxin often found in?

A

Homemade preserves (jams)

21
Q

What does botulinum toxin produce? What does the product do?

A

Endoproteinase - cleaves proteins required for ACh exocytosis

22
Q

Clinical uses of botulinum toxin

A
  • Treatment of strabismus - cross-eyed
  • Bleapharospasm - uncontrolled eyelid muscles
  • Botox
23
Q

Which fibres are metabolically expensive: slow or fast ?

A

Fast

24
Q

What colour muscle is slow oxidative muscle?

A

Red

25
Q

Example of slow oxidative muscle

A

Soleus

26
Q

What colour is fast glycolytic (IIb) muscle?

A

White

27
Q

Slow oxidative or fast glycolytic: Which is fatigue resistant?

A

Slow oxidative

28
Q

Slow oxidative or fast glycolytic: Which has a low glycogen content?

A

Slow oxidative

29
Q

Slow oxidative or fast glycolytic: Which has few mitochondria?

A

Fast glycolytic

30
Q

What are type IIb muscle fibres? Give an example

A

Fast oxidative. Gastrocnemius

31
Q

Phosphocreatine reaction

A

Creatine Phosphocreatine

Requires creatine kinase

32
Q

What is fatigue?

A

Weakening of a muscle
Shortage of glycogen
Increase in lactic acid levels
Failure of motor neurone to produce ACh

Physiology & Pharmacology (25 decks)

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