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Physiology > Cardiac Muscle TIssue > Flashcards

Cardiac Muscle TIssue Flashcards

1
Q

What do valves do?

A

prevent blood from flowing in the wrong direction.

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2
Q

What does the right heart do?

A

pumps blood to the lungs

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3
Q

What does the left heart do?

A

pumps blood through circulation to various parts of the body.

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4
Q

What does the atrium do?

A

It is a primer pump for a ventricle and moves blood to it.

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5
Q

What is a cardiac muscle referred to as?

A

syncytium

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6
Q

What are features of cardiac muscle tissue?

A

it is striated, mononucleated, has discs and branching cells.

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7
Q

What is the plateau?

A

Region of the cardiac action potential that stays flat for a period of time before repolarization occurs. It allows contraction to last 15 times longer in cardiac tissue.

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8
Q

What is a purkinje fiber?

A

A fiber that conducts an AP in the ventricular wall. It is a modified cardiac muscle cell.

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9
Q

How are the T-tubules and SER different in cardiac muscle fibers?

A

The t-tubules are larger and the SER is not as extensive.

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10
Q

Where are fast cardiac action potentials found?

A

in the atria, ventricles and conduction system. They are rapidly conducting and contractile with a high amplitude.

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11
Q

Where are slow cardiac action potentials found?

A

the SA and AV nodal tissues; they automatically depolarize during resting phase and have a low amplitude.

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12
Q

How many phases are in the fast action potentials?

A

4

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13
Q

What is the resting potential of a fast action potential?

A

-90 mV

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14
Q

What phase is the resting potential?

A

4

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15
Q

What phase does depolarization occur

A

0; Fast Na channels open and depolarize to +20 mV.

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16
Q

What phase does incomplete repolarization occur?

A

1; Na closes and K opens

17
Q

What phase does the plateau occur, and why does it occur?

A

2; Ca channels open and K close; increased Ca and decreased K causes plateau

18
Q

What phase does repolarization occur?

A

3; Ca closes, slow K opens, K rapidly enter and resting potential is restored.

19
Q

What causes fast action potentials?

A

changes in conductance of K, Na and Ca ions. The conductance pattern is due to voltage dependent gates.

20
Q

What results in a greater conduction velocity?

A

greater AP amplitude, more rapid rate of rise of phase 0, larger cell diameter.

21
Q

What are features of slow action potentials?

A

no fast sodium ion gates, smaller change in potential

22
Q

What is the resting phase potential of of a slow action potential?

A

-60 mV

23
Q

What are characteristics of fast type contractile myocytes?

A

large diameter, high amplitude and rapid onset of potential.

24
Q

What are characteristics of fast type non-contractile muscles?

A

large diameter and rapid upstroke

25
Q

What are characteristics of slow type non-contractile myocytes?

A

small diameter, low amplitdue and slow rate of depolarization.

26
Q

What causes an action potential in a ventricular fiber?

A

the opening of fast sodium channels and slow calcium-sodium channels.

27
Q

Where does the calcium come for the electrical-mechanical coupling?

A

from the T tubues via diffusion through voltage-gated calcium channels.

28
Q

What cannot be generated during an absolute refractory period?

A

another action potential

29
Q

What determines the length of the refractory period?

A

the ability of ion channels and gates to return to phase 4 (resting membrane) state.

30
Q

What determines the rhythmicity of the cell?

A

the rate of depolarization; gradual depolarization is caused by special Na channels that open during phase 4

31
Q

What tissues gradually depolarize during phase 4?

A

SA and AV nodes, purkinje fibers.

32
Q

Which node usually reaches threshold first and becomes the normal pacemaker of the heart’s rhythmicity?

A

SA node

33
Q

What allows fine control over sarcoplasmic calcium concentration and contractility?

A

fewer calcium induced calcium release channels.

34
Q

What results in relaxation of cardiac muscle fibers?

A

SERCA and sodium-calcium exchanger in the sarcolemma

Physiology (8 decks)

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