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PSIO 258: Elementary Physiology I > Cardiovascular System > Flashcards

Cardiovascular System Flashcards

1
Q

The pulmonary circuit is supplied by the _____ side of the heart.

A

right

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2
Q

The systemic circuit is supplied by the ______ side of the heart.

A

left

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3
Q

What are the 3 layers of the heart wall?

A
  • Epicardium
  • Myocardium
  • Endocardium (endothelium)
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4
Q

Pressure within chambers of the heart varies with …

A

heartbeat cycle

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5
Q

How do pressure differences in the chambers of the heart drive blood flow?

A
  • High pressure to low pressure
  • Valves prevent backward flow of blood
  • All valves open passively based on pressure gradient
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6
Q

What is autorhythmicity?

A

the ability to generate own rhythm

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7
Q

What do autorhythmic cells do?

A
  • electrical signal passageway

- cells provide a pathway for spreading excitation through the heart

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8
Q

What do pacemaker cells do?

A
  • Spontaneously depolarizing membrane potentials generate action potentials
  • Coordinate and provide rhythm to heartbeat
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9
Q

What do conduction fibres do?

A
  • Rapidly conduct action potentials

- Initiated by pacemaker cells

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10
Q

Spread of excitation between cells make the _____ contract then _______.

A
  • atria

- ventricles

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11
Q

The coordination of the spread of excitation between cells is due to:

A
  • gap junctions

- conduction pahtways

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12
Q

What is concentrated at the intercalated discs?

A
  • desmosomes

- gap junctions

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13
Q

Intercalated discs are junctions between …

A

adjacent myocardial cells

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14
Q

What do desmosomes do?

A

resist mechanical stress

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15
Q

What do gap junctions do?

A
  • link cardiac cells

- electrical coupling

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16
Q

Why doesn’t contraction of the heart doesn’t occur the same way we think of blood flow?

A

Both atria contract and then both ventricles contract

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17
Q

Describe the path of the initiation and conduction of an impulse.

A
  • action potential initiated at SA node
  • interatrial pathway
  • AV node (some delay)
  • to ventricals
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18
Q

Impulse travels to ventricals via…

A
  • bundle of His
  • right and left bundle branches
  • purkinje fibres
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19
Q

Describe the intertribal pathway.

A
  • SA node → right atrium → left atrium
  • Rapid
  • Simultaneous contraction of right and left atria
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20
Q

Describe the internodal pathway.

A

SA node → AV node

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21
Q

Describe AV node transmission.

A
  • Only pathway from atria to ventricles
  • Slow conduction: AV nodal delay = 0.1 sec
  • Atria contract before ventricles
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22
Q

How can heartbeat be controlled by pacemakers?

A
  • Autorhythmic cells (“pacemaker potentials”)

- Spontaneous depolarizations (Caused by channels opening/closing)

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23
Q

Describe electrical activity in pacemaker cells.

A
  • no external stimulus required
  • no steady resting membrane potential
  • Changes in membrane permeability to: Na+, K+ and Ca++
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24
Q

No steady resting membrane potential means…

A
  • Immediate depolarization

- “ramping” = pacemaker potential

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25
Q

Name the 3 channels for changes in membrane permeability.

A
  • K+ channels
  • Funny channels
  • T-type & L-type channels
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26
Q

What happens in the first part of pacemaker potential (slow depolarization)?

A
  • K+ close

- funny channels open

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27
Q

What happens in the last part of pacemaker potential (slow depolarization)?

A

T-type open

28
Q

What happens during rapid depolarization?

A

L-type open

29
Q

What happens during repolarization?

A
  • L-type close

- K+ open

30
Q

What are the steps of cardiac action potential?

A
  • depolarization
  • brief repolarization
  • plateau
  • repolorization
  • rest
31
Q

What happens during depolarization?

A

Na+ in

32
Q

What happens during brief repolarization?

A

Ca2+ in

33
Q

What happens during depolarization?

A

K+ out

34
Q

Cardiac contractile cells takes how long?

A

250-300 msec

35
Q

Skeletal muscles take how long?

A

1-2 msec

36
Q

How does excitation-contraction coupling in cardiac contractile cells have properties similar to skeletal muscles?

A
  • t-tubules
  • troponin-tropomyosin regulation
  • SR and Ca2+
37
Q

How does excitation-contraction coupling in cardiac contractile cells have properties similar to smooth muscles?

A
  • Gap junctions

- Extracellular Ca2+

38
Q

What are the steps of excitation-contraction coupling in the heart?

A
  1. Depolarization of cardiac contractile cell (Gap junction)
  2. Calcium channels (Plasma membrane)
  3. T tubules
  4. Calcium release from the SR
  5. Calcium binds to filaments
  6. binding sites exposed
  7. cross bridge cycle
39
Q

AP travels down _______.

A

t tubules

40
Q

Extracellular Calcium influx induces (“tells”) ____ to release ______ as well as signaled from ___ travelling down _____.

A
  • SR
  • calcium (CICR)
  • AP
  • t-tubules
41
Q

Calcium binds to ______.

A

troponin

42
Q

What is troponin?

A
  • a protein on tropomyosin

- causes tropomyosin to “move” out of the way and expose binding sites on actin for myosin filaments stays bound

43
Q

What happens in the cross bridge cycle?

A

myosin binding to actin- slide-release

44
Q

How does relaxation of cardiac muscle occur?

A
  • calcium removed from cytosol

- resting conditions reestablished

45
Q

What are the 3 ways calcium is removed from cytosol in the heart?

A
  • SR ATPase-pumped back into SR
  • Plasma membrane atpase-pumped out into extracellular matrix
  • Na+-Ca++ exchanger in plasma membrane
46
Q

What happens during resting conditions?

A

Troponin and tropomyosin move back to their positions and cover binding sites

47
Q

What does a electrocardiogram do?

A
  • gives a look at the electrical activity of the heart on the surface of the skin
  • Using electrical leads and electrodes – detects synchronicity of electrical signal provides a picture of what is happening
  • Used clinically to detect abnormalities – collect HR data
48
Q

How is your body a conductor?

A

Currents in body can spread to surface (ECG, EMG, EEG)

49
Q

Distance and amplitude of spread depend on two factors:

A
  • Size of potentials
  • Synchronicity of potentials from other cells
    (Heart electrical activity = synchronized)
50
Q

What are the parts of the electrical activity of the heart?

A
  • P wave
  • QRS complex
  • T wave
51
Q

P wave signals:

A

atrial contraction

52
Q

QRS complex signals:

A

ventricular contraction/systole

53
Q

T wave signals:

A

ventricular relaxation/diastole

54
Q

What is the P-Q interval?

A

time between conduction of signal through AV node

55
Q

What is the Q-T interval?

A

time of ventricular systole (length of contraction phase)

56
Q

What is the T-Q interval?

A

length of diastole or ventricular relaxation (when the heart is filling with blood

57
Q

What is the R-R interval?

A

measure of HR, beginning of ventricular systole to the next contraction

58
Q

What are the 2 main periods of the cardiac cycle?

A
  • systole

- diastole

59
Q

What happens during systole?

A

contraction of ventricles

60
Q

What happens during diastole?

A

relaxation of ventricles

61
Q

Valve opening is dependent on…

A

pressure differences

62
Q

What are the 4 phases of cardiac cycle?

A
  1. ventricular filling
  2. isovolumetric ventricular contraction
  3. ventricular ejection
  4. isovolumetric ventricular relaxation
63
Q

Describe the ventricular filling phase.

A
  • venous return
  • AV valves open
  • blood fills atria
  • passive until atrial contraction
64
Q

Describe the isovolumetric ventricular contraction phase.

A
  • start of systole
  • no change in volume
  • all valves closed
  • pressure in ventricles starts to increase
65
Q

Describe the ventricular ejection phase.

A
  • end of systole
  • Ventricular pressure exceeds aortic- blood pumped out
  • AV valves closed
  • Semilunar open
  • Valves close when pressure is greater outside chambers (aortic)
66
Q

Describe the isovolumetric ventricular relaxation phase.

A
  • beginning of diastole
  • no change in volume
  • relaxation: no blood in or out
  • valves closed

PSIO 258: Elementary Physiology I (14 decks)

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