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Foundation of Medicine > Negative Feedback Control in Cardiovascular System > Flashcards

Negative Feedback Control in Cardiovascular System Flashcards

1
Q

What is blood pressure

A

Outward hydrostatic pressure exerted by the blood on blood vessel walls

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2
Q

What is Systemic systolic arterial blood pressure

A

Pressure exerted by blood on walls of the aorta and systemic arteries when heart contracts

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3
Q

What is Systemic diastolic arterial blood pressure

A

Pressure exerted by the blood on walls of the aorta and systemic arteries when heart relaxes

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4
Q

What is the normal range of systolic arterial blood pressure

A

90-120 mmHg

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5
Q

What is the normal range of diastolic arterial blood pressure

A

60-80mmHg

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6
Q

What is hypertension

A

Clinical blood pressure of 140/90mmHg or higher & Day time average of 135/85mmHg or higher

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7
Q

What is pulse pressure

A

Difference between systolic and diastolic blood pressures

-Normally between 30-50mmHg

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8
Q

What is mean arterial blood pressure (MAP)

A

Average arterial blood pressure during a single cardiac cycle - Contraction and relaxation of heart

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9
Q

Why is Mean arterial blood pressure NOT obtained by averaging systolic and diastolic pressures

A

As in normal cardiac cycle,
- Diastolic portion is TWICE as long as systolic portion

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10
Q

How is mean arterial blood pressure (MAP) calculated

A

By using formula:

MAP= [(2x diastolic) + Systolic] /3

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11
Q

What is MAP of 120mmHg systolic and 80mmHg diastolic

A

MAP= [(2x80) + 120] /3
MAP= (280) /3
MAP= 93.3 mmHg

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12
Q

What is the normal range of mean arterial blood pressure

A

70-105mmHg

  • MAP of at least 60 needed to perfuse vital organs (Brain, heart and kidneys)
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13
Q

Why must Mean arterial blood pressure be regulated within narrow window

A
  • Pressure must be high enough to perfuse vital organs like brain, heart and kidneys
    BUT
    -Not too high that damage to blood vessels occurs or places extra strain on organs
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14
Q

What is the mechanism of baroreceptor reflex in short-term regulation of MAP

A

Negative feedback control

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15
Q

What is the sensor of detecting MAP variable

A

baroreceptors

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16
Q

What is the control centre being informed by baroreceptor (the sensor) in MAP

A

Medulla (The Cardiovascular control centre)

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17
Q

What is the effector that’s sent instructions from medulla (control centre)

A
  1. Heart
  2. Blood vessels
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18
Q

What do effectors in negative feedback control do

A

Bring about a compensatory response to restore the regulated variable to desired range

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19
Q

Where are the baroreceptors

A

Aortic arch= Aortic baroreceptors
Each carotid sinus= Carotid baroreceptors

20
Q

How do baroreceptor signals reach the medulla

A

Carotid baroreceptors signals via 9th cranial nerve to medulla
Aortic baroreceptors signals via 10th cranial nerve to medulla

21
Q

What kind of receptors are baroreceptors

A

Mechanoreceptors which are sensitive to stretch

22
Q

What does increasing MAP cause the firing rate in baroreceptors afferent neurons

A

Increases

23
Q

What does decreasing MAP cause the firing rate in baroreceptors afferent neurons

A

Decreases

24
Q

What impulses are sent from baroreceptors to cardiovascular control centre

A

Afferent impulses sent to CV control centre in medulla of the brainstem

(Means they carry information from sensory receptors of the skin and other organs to the central nervous system)

25
Q

What is the Cardiac Output (CO)

A

Volume of blood pumped by each ventricle of the heart per minute

26
Q

What is stroke volume (SV)

A

Volume of blood pumped by each ventricle of the heart per heart beat

27
Q

How is Cardiac Output calculated

A

CO= Stroke volume x Heart rate

28
Q

What is systemic vascular resistance (SVR)

A

Sum of resistance of all vasculature in systemic circulation

29
Q

How is MAP calculated using Systemic vascular resistance (SVR)

A
  1. MAP= Cardiac output x systemic vascular resistance
  2. MAP= stroke volume x Heart rate x systemic vascular resistance
30
Q

What 3 factors mean MAP can be regulated by regulating:

A
  1. Heart rate
  2. Stroke volume
  3. Systemic vascular resistance
31
Q

Heart is electrically controlled, where are the electrical signals generated

A

Within the heart itself

32
Q

What is auto rhythmicity

A

Heart is capable of beating rhythmically in the ABSENCE of external stimuli

33
Q

What system modifies heart rate

A

Autonomic (involuntary) Nervous System ANS

34
Q

What does the sympathetic division of Autonomic nervous system do

A

Stimulation accelerates the heart rate (Tachycardia)

-noradrenaline acts on Beta1 receptors

35
Q

What does the parasympathetic division of Autonomic nervous system do

A

Stimulates the vagus nerve (10th cranial nerve) slowing the heart rate (bradycardia)

-acetylcholine acts on muscarinic M2 receptors

36
Q

What system modifies stroke volume

A

Autonomic nervous system

37
Q

How does autonomic nervous system regulate stroke volume

A

SV increases if contractile strength of heart is increased

Sympathetic nerves innervate the ventricular myocardium, and stimulation increases the force of contraction therefore increases SV

38
Q

What are the major resistance vessels in systemic vascular resistance

A

Arterioles

39
Q

What regulates systemic vascular resistance

A

Vascular smooth muscles

40
Q

What does contraction of vascular smooth muscles do to SVR and MAP

A

Increases SVR and MAP
-DUE to vasoconstriction

41
Q

What does relaxation of vascular smooth muscles do to SVR and MAP

A

Decreases SVR and MAP
-Due to vasodilation

42
Q

What supplies vascular smooth muscle

A

Sympathetic nerve fibres- neurotransmitter is noradrenaline acting on alpha receptors

43
Q

What is Vasomotor tone

A

Vascular smooth muscles are partially constricted at rest

44
Q

What is vasomotor tone caused by

A

Tonic discharge of sympathetic nerves resulting in continuous noradrenaline release

45
Q

What increases vasomotor tone

A

Increases sympathetic discharge, resulting in vasoconstriction

46
Q

What decreases vasomotor tone

A

Decreases sympathetic discharge, resulting in vasodilation

Foundation of Medicine (23 decks)

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