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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

23
Q

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

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
What is the Cardiac Output (CO)
Volume of blood pumped by each ventricle of the heart per minute
26
What is stroke volume (SV)
Volume of blood pumped by each ventricle of the heart per heart beat
27
How is Cardiac Output calculated
CO= Stroke volume x Heart rate
28
What is systemic vascular resistance (SVR)
Sum of resistance of all vasculature in systemic circulation
29
How is MAP calculated using Systemic vascular resistance (SVR)
1. MAP= Cardiac output x systemic vascular resistance 2. MAP= stroke volume x Heart rate x systemic vascular resistance
30
What 3 factors mean MAP can be regulated by regulating:
1. Heart rate 2. Stroke volume 3. Systemic vascular resistance
31
Heart is electrically controlled, where are the electrical signals generated
Within the heart itself
32
What is auto rhythmicity
Heart is capable of beating rhythmically in the ABSENCE of external stimuli
33
What system modifies heart rate
Autonomic (involuntary) Nervous System ANS
34
What does the sympathetic division of Autonomic nervous system do
Stimulation accelerates the heart rate (Tachycardia) -noradrenaline acts on Beta1 receptors
35
What does the parasympathetic division of Autonomic nervous system do
Stimulates the vagus nerve (10th cranial nerve) slowing the heart rate (bradycardia) -acetylcholine acts on muscarinic M2 receptors
36
What system modifies stroke volume
Autonomic nervous system
37
How does autonomic nervous system regulate stroke volume
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
What are the major resistance vessels in systemic vascular resistance
Arterioles
39
What regulates systemic vascular resistance
Vascular smooth muscles
40
What does contraction of vascular smooth muscles do to SVR and MAP
Increases SVR and MAP -DUE to vasoconstriction
41
What does relaxation of vascular smooth muscles do to SVR and MAP
Decreases SVR and MAP -Due to vasodilation
42
What supplies vascular smooth muscle
Sympathetic nerve fibres- neurotransmitter is noradrenaline acting on alpha receptors
43
What is Vasomotor tone
Vascular smooth muscles are partially constricted at rest
44
What is vasomotor tone caused by
Tonic discharge of sympathetic nerves resulting in continuous noradrenaline release
45
What increases vasomotor tone
Increases sympathetic discharge, resulting in vasoconstriction
46
What decreases vasomotor tone
Decreases sympathetic discharge, resulting in vasodilation

Foundation of Medicine (23 decks)

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