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medscionefourtwo > Cardiovascular (Dr Rohit) > Flashcards

Cardiovascular (Dr Rohit) Flashcards

1
Q

what function does the heart serve

A
  • demand and supply
  • biochemical processes need energy which creates a demand for oxygen (demand)
  • Heart generates pressure and creates a pressure gradient (critical for supply)
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2
Q

Cardiac output =

A

heart rate x stroke volume (~80mL/beat)

= amount of blood ejected per unit time

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3
Q

systole

A

contraction

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4
Q

diastole

A

relaxation

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5
Q

isovolumetric relaxation

A

ventricular blood volume unchanged. All 4 valves closed.

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6
Q

ejection fraction

A

percentage of blood pumped out of a full ventricle

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7
Q

end-diastolic volume

A

~130mL

Blood volume after atrial systole and ventricular diastole

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8
Q

at rest, cardiac output =

A

4-7 Litres/minute

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9
Q

Venous return

A

volume of blood returning to the heart from the vasuclature every minute (linked to CO)

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10
Q

cardiac reserve

A

difference between maximum cardiac output and cardiac output at rest

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11
Q

Frank-starling law of the heart

A

the more the heart fills with blood (during diastole), the more the ventricular myocytes stretch, and the greater the force of contraction (systole)

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12
Q

preload

A
  • degree of stretch of the myocardial fibres, at the end of diastole, before they contract
  • preload is proportional to end-diastolic volume (the greater the EDV, the more forceful the next contraction)
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13
Q

contractility

A

force of contraction, of ventricular myocytes, at any given preload

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14
Q

afterload

A

pressure that must be exceeded before ejection of blood from the ventricles can occur

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15
Q

a healthy heart pumps out all the blood that has entered its chambers during the previous diastole TRUE/FALSE

A

TRUE

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16
Q

draw a stroke volume loop

A

(check it on page 73)

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17
Q

two mechanisms by which stroke volume is regulated

A
  1. intrinsic regulation of the force of contraction - governed by the degree of stretch of the myocardial fibre (end of diastole)
  2. extrinsic regulation - determined by activity of autonomic nervous system and levels of certain hormones
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18
Q

increase in filling pressure leads to…

A

increase in end-diastolic volume and increase in stroke volume

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19
Q

work done by the heart

A

change in pressure x change in volume

area of the ‘pressure-volume loop’

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20
Q

how does pressure in the ventricle change during filling

A

pressure falls at first due to suction effects of relaxation, then it rises as the volume increases

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21
Q

how does a positive inotrope effect contractility?

A

increases force of contraction by promoting Ca2+ inflow

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22
Q

effect of the calcium store, in the sarcoplasmic reticulum, on the membrane potential of the myocyte

A

NO EFFECT

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23
Q

excitation is initiated by specialised cells in the _________ ______ which lies close to the point of entry of the ______ _______ into the _____ atrium. A ______ ___ ________ is then conducted throughout the myocardium of the _____. The cells of the ____ ____ have an _______ resting potential. Between successive APs there is a ______ ________ due to the slow ___ inflow. This is the _______. When _______ is reached (-40mV) an AP is triggered to initiate a ________.

A

excitation is initiated by specialised cells in the sinoatrial node which lies close to the point of entry of the vena cava into the right atrium. A wave of depolarisation is then conducted throughout the myocardium of the atria. The cells of the SA node have an unstable resting potential. Between successive APs there is a progressive depolarisation due to the spontaneous Na+ inflow. This is the pacemaker. When threshold is reached (-40mV) an AP is triggered to initiate a heartbeat.

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24
Q

what do the action potentials of the atria, ventricles and conducting system have in common?

A

fast initial upstroke followed by a plateau phase of depolarisation before repolarisation.

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25
Q

what causes the plateau phase?

A

inward movement of calcium ions through L-type Ca2+ channels

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26
Q

what is the importance of the long plateau phase?

A
  • the action potential lasts almost as long as the contraction of the cell
  • enough time for efficient contraction (if it was just a twitch that would be poor)
  • ensures unidirectional excitation of the myocardium
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27
Q

when does repolarization of myocardial occur

A

when voltage-dependent calcium channels inactivate

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28
Q

AV node

A

slows the AP, which allows time for atrial systole

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29
Q

AV bundle/bundle of His

A

conducts from the AV node to the purkinje fibres i.e. carries the wave of depolarisation from the right atrium, through the insulating fibrous skeleton, to the ventricles

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30
Q

purkinje fibres

A

carry depolarisation through the ventricle walls

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31
Q

3 steps to an action potential in a ventricular contractile fibre

A
  1. Rapid depolarisation -
    due to Na+ inflow when voltage-gated fast Na+ channels open
  2. Plateau -
    due to Ca2+ inflow when voltage-gated slow Ca2+ channels open and K+ outflow when some K+ channels open
  3. repolarisation -
    due to closure of Ca2+ channels and K+ outflow when additional voltage-gated K+ channels open
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32
Q

pressure [over]load

A

ventricle has to contract while experiencing increased afterload. Therefore, contractility must increase which will lead to ventricle hypertrophy

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33
Q

volume [over]load

A

too much blood in the ventricle which leads to increased preload

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34
Q

does cardiac myocyte depolarise spontaneously?

A

nuh bruv

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35
Q

ECG measures_________ activity not ________

A

ECG measures_electrical_ activity not contraction

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36
Q

how does an increase in heart rate affect the ECG?

A

P-Q and Q-T interval decrease in time

37
Q

depolarisation of the atrial contractile fibres is represented on an ECG by…

A

P wave

38
Q

what happens at the end of the P wave

A

Atrial systole (contraction)

39
Q

QRS complex represents

A

the onset of ventricular depolarisation

40
Q

at which point on an ECG does the left ventricle contract?

A

at the end of the QRS complex

41
Q

how is the shape of the ECG determined?

A

by the position of the electrodes on the person

42
Q

‘down-up-down-up’ shape of the QRS

A

due to the direction the wave of depolarisation is moving, relative to the electrodes.

43
Q

repolarization of ventricular contractile fibres occurs at which stage?

A

T wave

44
Q

why is the T wave unidirectional?

A

because everything is repolarizing at the same time

45
Q

how would Ventricular diastole be represented on the ECG?

A

flat section after the T wave

46
Q

sensory receptors which…

  1. monitor movement of joints =
  2. monitor blood acidity, CO2 and O2 =
  3. monitor blood pressure =
A
  1. monitor movement = proprioreceptors
  2. monitor blood acidity, CO2 and O2 = chemoreceptors
  3. monitor blood pressure = baroreceptors
47
Q

sympathetic nerves

A
  • also called: “cardiac accelerator nerves)
  • increases the heart rate by increasing the rate of spontaneous depolarisation in the SA node
  • increases the stroke volume by increasing the contractility of the atria and ventricles
  • NOREPINEPHRINE enhances Ca2+ entry
48
Q

parasympathetic nerves

A
  • also called: “VAGUS”
  • decreases heart rate by decreasing the rate of spontaneous depolarisation in the SA node
  • ACh
49
Q

chronotrophy

A

regulation of heart rate

50
Q

the sympathetic and parasympathetic nerves arise in the __________ _________ which is found in the ________ ___________. The sympathetic nerve then travels down the _______ ______. The vagus nerve ___ ___ do this.

A

the sympathetic and parasympathetic nerves arise in the cardiovascular centre which is found in the medulla oblongata. The sympathetic nerve then travels down the spinal cord. The vagus nerve does not do this.

51
Q

control of the heartbeat is by the _______ nervous system

A

autonomic

52
Q

inotropy

A

control of the force of contraction

53
Q

how does mean arterial blood pressure differ from systolic and diastolic blood pressure?

A

120mmHg during systole

80mmHg during diastole

54
Q

blood flow

A

volume of blood that flows through any tissue in a given time period

55
Q

4 ways that blood pressure is regulated (intrinsically) by hormones

A
  1. RAA system
  2. Epinephrine/norepinephrine
  3. ADH
  4. ANP
56
Q

how is blood pressure regulated (intrinsically) neuronally

A

baroreceptor reflexes

57
Q

constriction of the arterioles leads to a(n) ________ in blood flow.
constriction of the veins leads to a(n) _______ in bloodflow.

A

constriction of the arterioles leads to a(n) decrease in blood flow.
constriction of the veins leads to a(n) increase in bloodflow.

58
Q

blood distribution in the cardiovascular system:

  • systemic veins and venules
  • systemic arteries and arterioles
  • pulmonary vessels
  • heart
  • systemic capillaries
A
  • systemic veins and venules 64%
  • systemic arteries and arterioles 13%
  • pulmonary vessels 9%
  • heart 7%
  • systemic capillaries 7%
59
Q

When listening with a stethoscope and measuring blood pressure and the occluded artery opens slightly, as the pressure is dropped, when the first sound is heard, that pressure is the __________ blood pressure. When pressure drops and the artery opens fully and there is no more turbulence, that pressure is the ________ blood pressure. These sounds are called _______ sounds.

A

When listening with a stethoscope and measuring blood pressure and the occluded artery opens slightly, as the pressure is dropped, when the first sound is heard, that pressure is the SYSTOLIC blood pressure. When pressure drops and the artery opens fully and there is no more turbulence, that pressure is the DIASTOLIC blood pressure. These sounds are called KOROTKOFF sounds.

60
Q

blood flows from _____ to ______ pressure

A

blood flows from high to low pressure

61
Q

Blood flow =

A

(change in pressure) / (resistance)

62
Q

mean artery pressure =

A

dBP + (sBP - dBP) / 3

63
Q

poiseuille’s law

A

resistance ∝ 1 / radius^4

64
Q

3 things that determine resistance

A
  1. viscosity
  2. radius
  3. blood vessel length
65
Q

which blood vessel is the largest contributor to the TPR and why?

A

arterioles because they can change their diameter best

66
Q

blood pressure =

A

cardiac output x TPR

67
Q

what is the reason for the large total cross-sectional area in capillaries

A

large CSA slows down the velocity to allow transfer of substances

68
Q

why does venule constriction lead to increased blood flow?

A

in venule constriction the precapillary sphincters are contracted, therefore blood takes a shorter route = less resistance

69
Q

4 hormones involved in vasoconstriction. what effect do they have on BP?

A
  1. Angiotensin II
  2. Antidiuretic hormone (ADH)
  3. norepinephrine
  4. epinephrine
    INCREASE THE BLOOD PRESSURE
70
Q

3 hormones involved in vasodilation. what effect do they have on BP?

A
  1. ANP
  2. epinephrine
  3. nitric oxide
    DECREASE THE BP
71
Q

effector nerves fire a nerve impulse to have a positive effect TRUE/FALSE

A

FALSE, the increase their frequency in a positive resonse. Input to the CVC is by nerve impulse

72
Q

what is the rate limiting factor for conversion of Angiotensinogen to Angiotensin I ? (where are they all made)

A

RENIN which is made by the kidneys

angiotensinogen is made in the liver

73
Q

How is Angiotensin I converted to Angiotensin II?

A

by the enzyme ACE

74
Q

2 effects of Angiotensin II

A
  1. causes vasoconstriction of arterioles and increases BP

2. increases Na+ and water retention (kidneys)

75
Q

response when BP is too high

A
  1. baroreceptors stretch more
  2. nerves fires back to the CV centre faster
  3. vasodilation, increased parasympathetic and decreased sympathetic follow
  4. Vasodilation decreases TPR, parasympathetic decreases HR
76
Q

nerves which are always firing

A

tonically active

77
Q

response when BP is too low

A
  1. baroreceptors stretch less
  2. nerves fire less
  3. increased renin → increased angiotensin II → vasoconstriction and water/salt retention
  4. ADH released from the hypothalamus → vasoconstriction and water/salt retention
  5. increased sympathetic → increased contractility
  6. BP increases
78
Q

total peripheral resistance

A

All of the vascular resistances offered by systemic blood vessels (mainly arterioles)

79
Q

blood hydrostatic pressure

A

pressure that water in blood plasma exerts on the walls of blood vessels, generated by the hearts pumping action.
arterial end = 35mmHg
venous end = 26mmHg

80
Q

interstitial fluid hydrostatic pressure

A

pressure which opposes blood hydrostatic pressure, pushes fluid from interstitial space back into capillaries
1 → 0mmHg

81
Q

blood colloid osmotic pressure/ oncotic pressure

A

force caused by the colloidal suspension of large proteins in blood plasma.
26mmHg in capillaries

82
Q

interstitial fluid osmotic pressure

A

pressure which opposes oncotic pressure and pulls fluid out of capillaries. very small because the small ammount of protein which leak are carried away by the lymphatic system.
0.1→5mmHg

83
Q

hypertension

A

high BP

84
Q

tachycardia

A

elevated resting heart rate

85
Q

bradycardia

A

resting heart rate under 50BPM

86
Q

baroreceptor

A

monitor the stretching of major arteries and veins, caused by the pressure of blood flowing through them. BP increases, baroreceptors fire at a higher frequency. Tonically active.

87
Q

Hemorrhage

A

loss of blood. Blood volume decreases

88
Q

starling’s law of the capillaries

A

The near equilibrium between the volumes of fluid filtered and volume of fluid reabsorbed.
BHP greater than BCOP at arterial end = movement out
BCOP greater than BHP at venous end = move in

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