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Human physiology > Lecture 7: Cardiac muscle tissue > Flashcards

Lecture 7: Cardiac muscle tissue Flashcards

1
Q

Cardiac muscle tissue characteristics (6)

A 
Sarcomeric arrangement (striated)
Mononucleated
Central nuclei
Syncytium
Intercalated discs
Cells may branch
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2
Q

Amplitude of action potential in ventricular fiber

A

Average 105mv (-85—+20)

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3
Q

What causes plateau

A

Sodium channels close rapidly, calcium channels stay open longer. Potassium channels open later and plateau is due to both calcium and potassium channels being open simultaneously

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4
Q

Where are T-tubules found in cardiac muscle, and how many cisternae

A

Along the Z-line, form diads with sarcoplasmic reticulum (one cisterna, one t-tubule)

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5
Q

Sarcoplasmic reticulum is more or less extensive in cardiac tissue compared to muscle

A

Less extensive

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6
Q

Special requirements of cardiac action potential (3)

A

Must be self generated
Must be prolonged
Must propogate from myocyte to myocyte in proper sequence.

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7
Q

Action potential is generated in the ______ in cardiac muscle

A

SA node

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8
Q

Action potential slows down at the _____

A

AV node

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9
Q

Action potential speeds up in

A

Bundle fibers and purkinje system

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10
Q

Fast action potentials are found

A

In the atria, ventricles and perkinje fibers

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11
Q

Perkinje fibers are contractile or non contractile

A

non contractile

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12
Q

Amplitude of fast potentials

A

~100mv

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13
Q

Slow potentials are found where

A

SA and AV nodal tissues

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14
Q

What happens during resting phase in slow tissues

A

They automatically begin to depolarize (more rapidly in SA than AV)

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15
Q

Amplitude of slow potential

A

~60mv

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16
Q

Slow potentials are contractile or non contractile

A

non contractile

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17
Q

Phase 4

A

resting phase

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18
Q

Phase 0

A

rapid depolarization

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19
Q

Phase 1

A

Initial, incomplete repolarization

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20
Q

Phase 2

A

Plateau or slow decline of membrane potential

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21
Q

Phase 3

A

repolarization

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22
Q

Fast action potentials are due to , and the conductance pattern is due to

A

Changes in conductance of calcium, sodium and potassium ions

Voltage dependent gates

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23
Q

These 3 things result in faster conduction velocity

A

Greater AP amplitude
Greater rate of rise of phase 0
Larger cell diameter

24
Q

Upstroke in slow action potentials is due to

A

Calcium (so it proceeds slowly)

25
Q

Slow action potentials have Na+ gates: T or F

A

False

26
Q

Resting potential of fast and slow potentials

A

Fast: -85
Slow: -60

27
Q

Amplitude is lower in ____ potentials

A

Slow potentials (60 compared to 105 in fast)

28
Q

Which tissues spontaneously depolarize, which have the fastest intrinsic rate of pulsation

A

SA, AV nodal tissues and perkinje fibers

SA nodal tissues

29
Q

What causes the spontaneous depolarization

A

Special leaky sodium channels that open after phase 3

30
Q

Characteristics of fast type contractile myocytes (3)

A

Large diameter
High amplitude
Rapid onset of action potential

31
Q

Characteristics of fast type non-contractile myoctyes (2)

A

Very large diameter

Very rapid upstroke

32
Q

Characteristics of slow type non-contractile myocytes (3)

A

Small diameter
Low amplitude
Slow rate of depolarization (slow upstroke)

33
Q

Action potential in ventricular fiber is due to what? What causes the initial spike

A

Opening of fast sodium channels and also slow calcium-sodium channels.
Initial spike caused by fast sodium channels

34
Q

What is the source of calcium for electro-mechanical coupling

A

From the T-tubules via diffusion through voltage dependent calcium channels called DHP receptors.
From cisternae of the SR through channels called Ryanodine receptors

35
Q

What is the normal pacemaker of the heart

A

SA node

36
Q

What happens when there is early premature contraction (contraction during early stage relative refractory period)

A

Amplitude is lower

37
Q

Resting potential and threshold of SA node

A
  • 55/-60

- 40

38
Q

At -40mv, which channels open in SA node

A

Slow sodium-calcium channels

39
Q

When do Potassium channels open in SA node

A

When sodium-calcium channels close

40
Q

Action potentials that did not originate in the SA nodes are said to be from

A

An ectopic focus or pacemaker

41
Q

Action potentials originating in the SA node generate

A

A “sinus” rhythm

42
Q

of calcium-induced calcium release channels in cardiac muscle compared to skeletal muscle- what impact does this have

A

Far fewer in cardiac muscle, allowing fine control over sarcoplasmic calcium concentration and contractility

43
Q

SERCA returns calcium to the SR during _____, which allows for

A

Diastole

allows for even greater calcium release on next beat and fast clearance of calcium from sarcoplasm

44
Q

What pumps calcium out of sarcoplasm besides SERCA

A

Sodium-calcium antiporter. Gradient is created by Na/K ATPase

45
Q

What % of blood flows from atria to ventricles before atrial contraction

A

80%, last 20% after contraction

46
Q

AV valves are closed during ____, which means:

A

Ventricular systole

Blood cannot flow into ventricles, but still flows into atria

47
Q

AV valves open at the ___ of ____ because of what

A

At the end of systole because of increased pressure in the atria

48
Q

First third of diastole what happens

A

Rapid filling of ventricles

49
Q

Middle third of diastole

A

Small amount of blood flows into ventricles representing blood that continues to flow into atria during diastole

50
Q

Last third of diastole

A

Atria contract to push final 20% of blood into ventricles

51
Q

Isovolumic contraction

A

Ventricles contract, but semilunar valves do not open for .02-.03 seconds

52
Q

Period of rapid ejection occurs at what pressure in L and R ventricles

A

Left: a little above 80 mm hg
Right: a little above 8 mm hg

53
Q

What occurs during rapid ejection- which valves open, how much blood is ejected, what portion of the total ejection does this take up

A

Semilunar valves open
70% of blood is ejected
Occurs during first third of ejection

54
Q

Slow ejection

A

Last 30% ejected during final 2/3 of ejection

55
Q

Frank starling law

A

The greater the heart muscle is stretched during filling, the greater the force of contraction and the greater the quantity of blood pumped into the aorta.

56
Q

What causes the greater force created in frank starling law

A

The stretching of cardiac muscle brings the actin and myosin filaments to a more nearly optimal degree of overlap for force generation

Human physiology (16 decks)

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