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Physiology Exam #1 > Muscle Physiology > Flashcards

Muscle Physiology Flashcards

1
Q

Muscles contain bundles of fibers called _______

A

Myofibrils

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2
Q

Review the sarcomere on 6-2. Know I band, A band, Z line, M line

A

Always comes back to haunt us

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3
Q

What is an H zone?

A

A central region of A band where thin filaments do not overlap with thick filaments

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4
Q

Do thick or thin filaments change length in muscle contraciton?

A

No

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5
Q

What theory explains muscle contraction?

A

The Sliding Filament Hypothesis

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6
Q

What are thick filaments made of?

A

Myosin

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7
Q

What proteins are thin filaments made of?

A

Actin, Tropomyosin, and Troponin

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8
Q

Structure of actin in a thin filament?

A

Polymerized globular protein entwined in a helix

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9
Q

Function of troponin/tropomyosin?

A

regulate the interaction of myosin with the actin molecule

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10
Q

What does the hydrolysis of ATP bound to myosin do?

A

Causes the myosin head to pivot

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11
Q

Describe the cross-bridge cycle

A
  1. Baseline – Myosin with ATP is next to Actin
  2. Hydrolysis of ATP causes pivot of the myosin head
  3. Pivoted head binds Actin
  4. ADP+Pi is released, causing myosin head to un-pivot, pulling actin
  5. ATP binds, causing the myosin head to release the Actin
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12
Q

In resting muscle, what covers the myosin binding site?

A

Tropomyosin

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13
Q

Purpose of troponin?

A

Locks tropomyosin in position

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14
Q

What causes the troponin-tropomyosin complex to release actin for binding?

A

Ca ions

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15
Q

Where do the Ca ions that free up the actin come from?

A

Sarcoplasmic Reticulum

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16
Q

What triggers Sarcoplasmic Reticulum release of Ca?

A

AP traveling the transverse tubule system.

Linkage of calcium-induced calcium-release channels lead to channel changes.

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17
Q

What is the Transverse Tubule system?

A

Periodic infoldings of the plasma membrane

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18
Q

Describe the two receptors involved in Calcium release.

A

Voltage activated Ca channel in T Tubule activated calcium induced calcium release channel.

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19
Q

Main difference between skeletal and heart muscle?

A

Individual cardiac muscle cells are linked via gap junctions.

20
Q

How does smooth muscle signalling get going

A

Phosphatidyl inositol cleaved to IP3
IP3 binds to calcium release channel to sarcoplasmic reticulum
Calcium release

21
Q

What major player is no longer involved in smooth muscle

A

Troponin

22
Q

How is smooth muscle myosin regulated?

A

Phosphorylation-dephosphorylation of myosin

Myosin Light Chain Kinase and Myosin Light Chain Phosphotase

23
Q

What regulates MLCK?

A

Calmodulin

24
Q

What determines the force of a muscle fiber?

A

Amount of overlap of thick and thin filaments

25
Q

During a maintained contraction, how much of the muscle’s ATP is used to fuel the cross bridge? Pumping into the Sarc?

A

50-80%

20-30%

26
Q

Two methods muscles use to generate ATP

A

Ox Phos and Anerobic glycolysis

27
Q

Pros and Cons of Ox Phos?

A

Efficient, can operate continually

Slow process, cannot meet maximal ATP consumption rated

28
Q

Pros and Cons on Anerobic glycolysis?

A

Fast

Limited by glycogen stores, inefficient

29
Q

How many muscle fibers can a neuron innervate?

A

Many

30
Q

How many neurons can innervate a muscle fiber?

A

One

31
Q

What is the innervation ratio?

A

The number of fibers innervated by a single motoneuron.

32
Q

Which is longer, muscle AP or twitch?

A

The twitch (10 to 100 ms)

33
Q

What happens when repeated stimulations are happening faster than twitches are ending?

A

Tension developed by twitches summates

34
Q

What happens if you make the muscles stimulate at their highest frequencies?

A

Twitches fuse – Tetanus

35
Q

Three categories of motor units.

A

Slow, Fast Fatigue Resistant (FR), and Fast Fatiguable (FF)

36
Q

Describe S units.

A

Contract slow, small peak force

Highly resistant to fatigue

37
Q

Describe FF units

A

Contract fast, forcefully

Easy to fatigue

38
Q

Describe FR units.

A

Similar to FF, but with smaller peak forces and higher fatigue resistance

39
Q

Nerve properties may influence what properties of muscles.

A

Metabolic and contractile characteristics

40
Q

How is force of contraction increased?

A
  1. Recruiting more motor units

2. Increasing firing rate of individual units

41
Q

Order in which recruitment occurs.

A

S –> FR –> FF

FR and FF only for strenuous activities

42
Q

Name for the rule about the order in which recruitment occurs.

A

The Size Principle

43
Q

What does the size principle allow?

A

Higher motor centers determine the overall level of drive and not the exact combination of motor units to be recruited

44
Q

What is malignant hypothermia? What do you do?

A

A mutation of ryanodine receptors. Provide muscle relaxants

45
Q

What is myotonic dystrophy?

A

A disease with muscle weakness, cataracts, baldness, heart disease, and muscle failure.

Physiology Exam #1 (7 decks)

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