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Anaesthetic FRCA Primary - Teaching Days > Basic Sciences - Cardiovascular Physiology > Flashcards

Basic Sciences - Cardiovascular Physiology Flashcards

1
Q

Definition of flow

A

Quantity of fluid being moved passed a point in a given time

Not velocity

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2
Q

Cardiac output equation

A

CO = SV x HR

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3
Q

Approximate CO in average person

A

5 L/min

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4
Q

Approximate SV in average person

A

70 ml

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5
Q

Requirement to generate flow of a fluid

A

Pressure gradient

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6
Q

Main types of receptor present in the heart

A

Muscarinic cholinergic receptors - parasympathetic

Beta 1 adrenergic - sympathetic

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7
Q

Main types of receptor present in peripheral blood vessels

A

Alpha 1 adrenergic - sympathetic

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8
Q

Factors which impact flow of fluid

A
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9
Q

Most efficient type of flow

A

Laminar flow

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10
Q

Correlation between pressure, flow and resistance

A

Pressure = Flow x Resistance

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11
Q

Correlation of pressure, flow and resistance in human circulation

A

MAP = CO x SVR

Mean arterial pressure
Cardiac output
Systemic vascular resistance

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12
Q

How to calculate flow under laminar flow conditions

A

Poiseuille’s law

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13
Q

Poiseuille’s law

A
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14
Q

Which factor has greatest influence on flow

A

Radius of vessel / pipe (according to Poiseuille’s law)

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15
Q

Calculations for MAP

A

MAP = CO x SVR

MAP = 2/3 Diastolic BP + 1/3 (Systolic - Diastolic BP)

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16
Q

Reason for MAP representing 2/3 Diastole and 1/3 Systole

A

Cardiac cycle is 2/3 in diastole

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17
Q

Arterial BP waveform

A

Dicrotic notch - the change in wave form on the descent

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18
Q

Dicrotic notch on arterial waveform representation

A

Elastic recoil of aortic wall immediately after aortic valve closure

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19
Q

Normal pressures of right atrium

A

Systole 5 mmHg
Diastole 2 mmHg

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20
Q

Normal pressures of right ventricle

A

Systole 25 mmHg
Diastole 0 mmHg

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21
Q

Normal pressures of left atrium

A

Systole 6 mmHg
Diastole 3 mmHg

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22
Q

Normal pressures of left atrium

A

Systole 120 mmHg
Diastole 0 mmHg

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23
Q

Reason for large pressure difference in left ventricle between systole and diastole

A

Diastole pressure must be less than left atrial pressure in order to fill

Systole pressure must overcome aortic resistance

24
Q

Reason right ventricle has lower systolic pressure than left ventricle

A

Pulmonary circulation has lower resistance than systemic circulation

Less pressure needed to perfuse it

25
Q

Pressure changes in different circulation vessels

A
26
Q

Why does biggest drop in pressure occur in the arterioles

A

Small radius produces high resistance

Resistance is inversely proportional to radius^4 according to Poiseuille’s law

27
Q

What happens to coronary vessels during systole

A

Pressure generated by LV in systole occludes the coronary vessels running through which provides cardiac blood supply

28
Q

During which cardiac cycle phase does most coronary blood flow occur

A

Diastole - LV is relaxed

29
Q

Two main systems that regulate cardiovascular system

A

Nervous (autonomic nervous system)

Humoral (essentially Renin-angiotensin-aldosterone system)

30
Q

Speed of response of autonomic nervous system to hypotension

A

Seconds - minutes

31
Q

Sensor of autonomic nervous system to hypotension + location

A

Baroreceptors

Carotid sinus

32
Q

Effector of autonomic nervous system response to hypotension

A

Sympathetic outflow

33
Q

Response caused by autonomic nervous system from hypotension

A

Vasoconstriction
Tachycardia

34
Q

Speed of response of Humoral system to hypotension

A

Minutes - hours

35
Q

Sensor of Humoral system to hypotension + location

A

Juxtaglomerular apparatus

Kidney

36
Q

Effector of Humoral system response to hypotension

A

Renin-angiotensin
and subsequently aldosterone

37
Q

Response caused by Humoral system from hypotension

A

Vasoconstriction
Na+ / water retention

38
Q

Duration of action of nervous vs humoral systems

A

Humoral system is longer lasting but slower onset

39
Q

Actions of renin

A

Activates cascade which produces angiotensin II

Stimulates aldosterone release from adrenal cortex

40
Q

Where is angiotensin I converted to angiotensin II

A

Lung

41
Q

Effects of hypervolaemia to reduce circulating volume

A

Distention of atria

Causes release of ANP (atrial natriuretic peptide)

Results in sodium and water excretion

42
Q

Stages of hypovolaemic shock

A
43
Q

Other useful measurements to assess hypovolaemia

A

Urine output
Respiratory rate
Central venous pressure

44
Q

Cardiac myocyte action potential

A
45
Q

How is simultaneous cardiac muscle fibre contraction achieved

A

Specialised conduction system
Syncitial nature of cardiac muscle
Prolongation of action potential

46
Q

How is cardiac action potential prolonged

A

Slow Ca2+ inflow through L type channels

47
Q

Duration of cardiac action potential

A

300 ms

48
Q

Duration of nerve cell action potential

A

1 to 2 ms

49
Q

How is tetanic / sustained contraction of cardiac muscle prevented

A

Ion channel inactivation - prolonged refractory period

50
Q

Natural firing rate of the SA node

A

100 - 120 bpm

51
Q

Why is heart rate slower than intrinsic firing rate of SA node

A

Dominant vagal parasympathetic activity

52
Q

Ionic sequence of SA node action potentials

A

1) Continuous slow inward leak of Na+ until the threshold potential of -40 mV is reached

2) Main depolarization brought about by Ca2+ (not Na+) inflow through L-type channels

3) Repolarization from K+ outflow

There is no resting phase or resting membrane potential, and phases 1 and 2 of the action potential are absent. The cycle length determines the heart rate.

53
Q

How is heart rate changed from an action potential / ionic perspective

A

Phase 4 slope is altered to make cycle length shorter or longer

Increased Na+ permeability -> Tachycardia

Increased K+ permeability -> Bradycardia

54
Q

Pacemaker cell action potential graph

A
55
Q

Time delay applied to impulse by AV node

A

~100 ms

56
Q
A

Anaesthetic FRCA Primary - Teaching Days (64 decks)

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