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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
Slow action potentials have Na+ gates: T or F
False
26
Resting potential of fast and slow potentials
Fast: -85 Slow: -60
27
Amplitude is lower in ____ potentials
Slow potentials (60 compared to 105 in fast)
28
Which tissues spontaneously depolarize, which have the fastest intrinsic rate of pulsation
SA, AV nodal tissues and perkinje fibers | SA nodal tissues
29
What causes the spontaneous depolarization
Special leaky sodium channels that open after phase 3
30
Characteristics of fast type contractile myocytes (3)
Large diameter High amplitude Rapid onset of action potential
31
Characteristics of fast type non-contractile myoctyes (2)
Very large diameter | Very rapid upstroke
32
Characteristics of slow type non-contractile myocytes (3)
Small diameter Low amplitude Slow rate of depolarization (slow upstroke)
33
Action potential in ventricular fiber is due to what? What causes the initial spike
Opening of fast sodium channels and also slow calcium-sodium channels. Initial spike caused by fast sodium channels
34
What is the source of calcium for electro-mechanical coupling
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
What is the normal pacemaker of the heart
SA node
36
What happens when there is early premature contraction (contraction during early stage relative refractory period)
Amplitude is lower
37
Resting potential and threshold of SA node
- 55/-60 | - 40
38
At -40mv, which channels open in SA node
Slow sodium-calcium channels
39
When do Potassium channels open in SA node
When sodium-calcium channels close
40
Action potentials that did not originate in the SA nodes are said to be from
An ectopic focus or pacemaker
41
Action potentials originating in the SA node generate
A "sinus" rhythm
42
of calcium-induced calcium release channels in cardiac muscle compared to skeletal muscle- what impact does this have
Far fewer in cardiac muscle, allowing fine control over sarcoplasmic calcium concentration and contractility
43
SERCA returns calcium to the SR during _____, which allows for
Diastole | allows for even greater calcium release on next beat and fast clearance of calcium from sarcoplasm
44
What pumps calcium out of sarcoplasm besides SERCA
Sodium-calcium antiporter. Gradient is created by Na/K ATPase
45
What % of blood flows from atria to ventricles before atrial contraction
80%, last 20% after contraction
46
AV valves are closed during ____, which means:
Ventricular systole | Blood cannot flow into ventricles, but still flows into atria
47
AV valves open at the ___ of ____ because of what
At the end of systole because of increased pressure in the atria
48
First third of diastole what happens
Rapid filling of ventricles
49
Middle third of diastole
Small amount of blood flows into ventricles representing blood that continues to flow into atria during diastole
50
Last third of diastole
Atria contract to push final 20% of blood into ventricles
51
Isovolumic contraction
Ventricles contract, but semilunar valves do not open for .02-.03 seconds
52
Period of rapid ejection occurs at what pressure in L and R ventricles
Left: a little above 80 mm hg Right: a little above 8 mm hg
53
What occurs during rapid ejection- which valves open, how much blood is ejected, what portion of the total ejection does this take up
Semilunar valves open 70% of blood is ejected Occurs during first third of ejection
54
Slow ejection
Last 30% ejected during final 2/3 of ejection
55
Frank starling law
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
What causes the greater force created in frank starling law
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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