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Excitable Cells > ELM17: Muscle 2 > Flashcards

ELM17: Muscle 2 Flashcards

1
Q

What are the characteristics of a muscle twitch and why does this happen?

A

Longer and delayed
More time for calcium concentration to rise and decrease

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2
Q

What is the tetanus state of a muscle?

A

The state where a muscle is maximally stimulated

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3
Q

What is Hennemans size principle?

A

When a muscle is stimulated motor neurons are recruited in order of size

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4
Q

What is the function of muscles using Hennemans size principle?

A

Can regulate the force of contraction
Can make small or large contractions

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5
Q

What are the three types of skeletal muscle?

A

Slow twitch oxidative
Fast twitch glycolytic
Fast twitch oxidative

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6
Q

What are the properties of slow fibre skeletal muscle?

A

Posture maintenance
Myoglobin red as oxygen store
Many mitochondria

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7
Q

What are the properties of fast fibre skeletal muscle?

A

Fast myosin isoform
Fast
Ca transient
Rapid shortening at high energy cost as ATP hydrolysed quickly

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8
Q

What are type IIA fibres?

A

Fast oxidative
Lots of mitochondria
Good blood supply
Good glycogen stores
Resist fatigue

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9
Q

What are type IIB fibres?

A

Fast glycolytic fibres
Lactate accumulation and acidosis can limit contraction

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10
Q

What is duchenne muscular dystrophy?

A

X linked disorder caused by dystrophin gene mutation
Skeletal muscle not linked to ECM properly
Excess calcium enters and muscle fibres die
Progressive muscle weakness

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11
Q

What happens in animals with myostatin deficiencies?

A

Extra muscle mass and little fat

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12
Q

What are the differences between cardiac and skeletal muscle?

A

Branched syncytium
Cells not fused completely
Joined by intercalated discs
Different control mechanisms
Only in heart

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13
Q

What causes the rising phase in cardiac muscle?

A

Opening of sodium channels

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14
Q

What causes the broad plateau phase in cardiac muscles?

A

Opening of voltage gated calcium channels

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15
Q

What is the process of excitation contraction coupling in cardiac muscle?

A
  1. L type calcium channel on membrane lets calcium in
  2. Calcium induced calcium release from sarcoplasmic reticulum using ryanodine receptor
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16
Q

How is contraction initiated in cardiac muscle?

A

Myogenic as pacemaker potentials generated

17
Q

What are pacemaker potentials?

A

Slow depolarisation of the membrane that happens independently

18
Q

What occurs when the slope of pacemaker potential steepens?

A

SNS is activated

19
Q

What occurs when the slope of the pacemaker potentials unsteepens?

A

PNS is activated

20
Q

What determines the force of contraction?

A

Degree of stretch of cardiac muscle
Concentration of cytoplasmic reticulum

21
Q

Why is smooth muscle different?

A

No striations
No T tubules
Gap junctions or independent

22
Q

Where is smooth muscle usually found?

A

In hollow organs

23
Q

What is the function of smooth muscle?

A

Propel contents
Regulate flow
Usually controlled by ANS

24
Q

What is the difference in the contraction mechanism of smooth muscle?

A

Slowly
More energy efficient
Contracts well over greater range

25
Q

What is the first mechanism of excitation contraction coupling in smooth muscle?

A
  1. Depolarisation
  2. L type calcium channels open and calcium enters
  3. Triggers calcium induced calcium release from ryanodine receptor
26
Q

What is the second mechanism of excitation contraction coupling in smooth muscle?

A
  1. Agonist binds to GPCR
  2. Activates phospholipase C
  3. Activates IP3
  4. Releases calcium
27
Q

What is the third mechanism of excitation contraction coupling in smooth muscle|?

A
  1. SR runs out of calcium and signals store operated calcium channels
  2. Open and calcium enters
28
Q

What is the role of calcium in smooth muscle?

A

Increase the low ATPase activity of smooth muscle myosin heads

29
Q

How does calcium increase the ATPase activity in smooth muscle?

A
  1. Calcium binds to calmodulin
  2. Interacts and activates MLCK
  3. MLCK phosphorylates regulatory light chains
  4. Switches on ATPase activity
30
Q

How is smooth muscle excited?

A

Myogenic
Initiated by AP from neuronal stimulation
APs superimposed on myogenic activity
Graded response to depolarisation
Modulated by NTs and hormones

Excitable Cells (23 decks)

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