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feedback control with cardiovascular system Flashcards

1
Q

what is blood pressure?

A

outward pressure exerted by blood on blood vessel walls

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2
Q

what is systolic blood pressure?

A

-pressure exerted by blood on the walls of the aorta and systemic arteries when the heart CONTRACTS
-normal 120 mmHg (resting)

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3
Q

what is diastolic blood pressure?

A

pressure exerted by blood on the walls of the aorta and systemic arteries when the heart RELAXES
-normal 80 mmHg (resting)

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3
Q

what is normal systolic range?

A

90-120 mmHg

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4
Q

what is normal diastolic range

A

60-80 mmHg

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5
Q

what is hypertension (what are the numerical values)?

A

-high blood pressure
-clinical bp 140/90 mmHg
-day time average 135/85 mmHg or higher

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6
Q

what is pulse pressure?

A

different between systolic and diastolic blood pressures
-normal range 30-50 mmHg

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7
Q

what is mean arterial blood pressure?

A

average arterial blood pressure during a single cardiac cycle (contraction/relaxation)

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8
Q

what occurs during a normal cardiac cycle?

A

diastolic period is twice as long as the systolic period

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9
Q

how is MAP calculated?

A

-MAP = [(2 x Diastolic) + Systolic] / 3 OR
MAP = Diastolic + (pulse pressure/3)

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10
Q

what is the normal range of MAP?

A

70-105 mmHg

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11
Q

what is the least amount of MAP needed and why?

A

-at least 60 mmHg
-needed to perfuse vital organs (brain/heart/kidney)

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12
Q

why can the MAP not be too high?

A

-damages blood vessels (brain/kidney/eyes)
-extra strain on the heart

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13
Q

what is hypotension?

A

-low blood pressure
-bp less than 90/60 mmHg

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14
Q

what kind of mechanism does the CV system use?

A

negative feedback mechanism

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15
Q

what are the sensors of the CV system

A

baroreceptors

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16
Q

what are baroreceptors sensitive to?

A

pressure/stretch

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17
Q

what do baroreceptors do?

A

when they detect stretch/pressure they send an impulse to the control centre (medulla)

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18
Q

what happens when firing rate of baroreceptors increases?

A

-MAP increases

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19
Q

what do baroreceptors regulate?

A

MAP

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20
Q

what is the control centre of the CV system?

A

the medulla

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21
Q

what does the medulla do?

A

receives afferent signals and sends instructions to the effectors (heart and blood vessels)

22
Q

what are the 2 types of baroreceptors?

A

-aortic baroreceptors
-carotid baroreceptors

23
Q

what is the nucleus tracts solitaries (NTS)?

A

1st synapse site for all CV system afferents in the medulla

24
Q

what are the effectors of the CV system?

A

-heart
-blood vessels

25
Q

do baroreceptors respond to acute or chronic changes

A

-ONLY acute
-firing rate will decrease if high blood pressure is sustained

26
Q

what varies in the heart as an effector?

A

-heart rate
-stroke volume

27
Q

what varies in the blood vessels as an effector?

A

systemic vascular resistance

28
Q

how CAN MAP be calculated in relation to negative feedback?

A

MAP = Cardiac Output (CO) x Systemic Vascular Resistance (SVR)

29
Q

how is cardiac output (CO) calculated?

A

CO = Stroke Volume (SV) x Heart Rate (HR)

30
Q

what is cardiac output (CO)?

A

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

31
Q

what is stroke volume?

A

volume of blood pumped by each ventricle of the heart per heartbeat

32
Q

what is systemic vascular resistance?

A

the sum of all resistance in the systemic circulation (everything BUT lungs)

33
Q

how ELSE CAN MAP be calculated in relation to negative feedback? (3 factors)

A

MAP = SV x HR x SVR

34
Q

how can MAP be regulated?

A

increasing/decreasing:
-heart rate
-stroke volume
-systemic vascular resistance

35
Q

what is autorhythmicity?

A

hearts capability to beat rhythmically without external stimuli

36
Q

what is the heart modified by?

A

Autonomic (”involuntary”) Nervous system (ANS)

37
Q

what is the sympathetic division?

A

-simulation of the vagus nerve accelerates heart rate (tachycardia)
-Noradrenaline acts on B1 receptors

38
Q

what is the parasympathetic division?

A

-simulation of the vagus nerve slows the heart rate (bradycardia)
-Acetylcholine acts on muscarinic M2 receptors

39
Q

how is stroke volume regulated?

A

-sympathetic nerves
-stimulation increases force of contraction

40
Q

how is heart rate increases

A

-sympathetic stimulation
- noradrenaline acts on β1 receptors

41
Q

how is the systemic vascular resistance regulated?

A

vascular smooth muscles - sympathetic nerve fibres

42
Q

what are the main resistance vessels

A

arterioles

43
Q

what happens when there is a contraction of vascular smooth muscles?

A

-vasoconstriction
-increases SVR and MAP

44
Q

what happens when there is a relaxation of vascular smooth muscles?

A

-vasodilation
-decreases SVR and MAP

45
Q

what happens when there’s an increase in BP

A

-barorecptors discharge increases
-send impulse to medulla
-decrease in sympathetic activity
-increase in vagal (parasympathetic) activity
→decreases HR
→decreases SV (ventilation)
(both cause decrease in CO)
-decrease in sympathetic constrictor tone
→vasodilation
→decreases SVR This brings blood pressure back to normal (decreases BP)

46
Q

what happens when there’s a decrease in BP

A

-barorecptors discharge is low
-send impulse to medulla
-increase in sympathetic activity
-decrease in vagal (parasympathetic) activity
→increase HR
→increases SV (venoconstriction)(both cause increase in CO)
-increase in sympathetic constrictor tone
→vasoconstriction
→increases SVR
This brings blood pressure back to normal (increases BP)

47
Q

what is vasomotor tone?

A

tonic discharge of sympathetic nerves

48
Q

why are vascular smooth muscles partially constricted at rest?

A

continuous release of noradrenaline → because of tonic discharge

49
Q

what happens if there an increase in sympathetic discharge?

A

increase the vasomotor tone→ vasoconstriction

50
Q

what happens if there an decrease in sympathetic discharge?

A

decrease the vasomotor tone→ vasodilation

51
Q

is there any significant parasympathetic innervation of arterial smooth muscles?

A

no, except in penis and clitoris

52
Q

arterial and arteriolar smooth muscles are mainly supplied by….

A

sympathetic nerves

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