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Hypertensiona > The Systemic Arterial Blood Pressure > Flashcards

The Systemic Arterial Blood Pressure Flashcards

1
Q

What can the arterial pulse be described as?

A

reflected pressure wave

pumping blood out the heart with resistance to this blood flow

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2
Q

What does the lowest pulse pressure correspond to?

A

diastolic BP

around 70mmHg

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3
Q

What causes the increase in pulse pressure?

A

ejection phase

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4
Q

What does the peak pulse pressure correspond to?

A

systolic BP

around 120 mmHg

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5
Q

What causes a slight second notch/peak in pressure after systole?

A

closure of aortic valve

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6
Q

What can be calculated if diastolic and systolic BPs are known?

A

Mean Arterial Pressure

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7
Q

How to calculate the mean blood pressure

A

mean BP = (DBP + 1/3PP)

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8
Q

What is the pulse pressure?

A

difference between SBP and DBP

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9
Q

What is SBP determined by?

A

stroke volume

aortic elasticity

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10
Q

How is SBP affected when stroke volume is increased?

A

increase in SBP

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11
Q

How is SBP affected when aortic elasticity is decreased?

A

increase in SBP

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12
Q

Why does aortic elasticity affect SBP?

A

elastic aorta takes up kinetic energy from the blood during systole and dampens the rise in pressure

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13
Q

Clinical relevance of aortic elasticity and SBP

A

aortic elasticity reduces as age increases

therefore inelastic aortas may cause systolic hypertension in the elderly

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14
Q

What is DBP determined by?

A

mainly peripheral resistance
aortic elasticity
heart rate

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15
Q

How is DBP affected if total peripheral resistance is increased?

A

increased DBP

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16
Q

How is DBP affected when aortic elasticity is decreased?

A

decreased DBP

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17
Q

Why is does aortic elasticity affect DBP?

A

kinetic energy taken up during systole is given back in diastole, adding to the pressure
if less is taken up, there is less to give back

18
Q

How is DBP affected when heart rate decreases?

A

decreased DBP

19
Q

Clinical relevance of aortic elasticity and DBP

A

less taken up, less to give back

causes wide pulse pressure in elderly

20
Q

How to calculate mean arterial blood pressure

A

cardiac output x total peripheral resistance

21
Q

How does systemic and pulmonary circulation compare?

and why?

A

systemic resistance around 20 au, pulmonary is 2 au

due to much lower mean pulmonary arterial pressure (cardiac output is the same)

22
Q

Why is control of arterial blood pressure important?

A

provides a pressure head to drive blood flow

permits activity, postural changes - protects against effects of gravity

23
Q

How is control of arterial BP achieved?

A

feedback system:
pressure sensors in circulation to brain (afferent)
integration centres in CNS - output (efferent)
effector mechanisms via autonomic nervous system

24
Q

What are the pressure sensors?

and where are they located?

A

arterial (high pressure) baroreceptors - walls of carotid sinus and aortic arch
cardiopulmonary (low pressure) baroreceptors - pulmonary vasculature, atrial-vena caval junctions, ventricular walls

25
Q

How do the arterial baroreceptors work?

A

increase in transmural pressure increases afferent nerve discharge and vice versa
carotid sinus/aortic nerves, glossopharyngeal and vagus (IX and X cranial nerves)

26
Q

What are effector mechanisms?

A

autonomic control of the circulation

27
Q

What do effector mechanisms affect?

A

Heart and total peripheral resistance

28
Q

How do effector mechanisms affect the heart?

A

activation of:
parasympathetic - acetylcholine, muscarinic receptors, decrease HR
sympathetic - noradrenaline, β1-adrenoceptors, increase HR and force

29
Q

How do effector mechanisms affect total peripheral resistance?

A

sympathetic activated
release of NA, bind onto α1-adrenoceptors on smooth muscle cells
causing vasoconstriction which increases total peripheral resistance

30
Q

How do the cardiopulmonary baroreceptors work?

A

‘volume receptors’ - reflection of volume as blood returned to the heart
increase in transmural pressure - oncrease in afferent nerve discharge (vagus)

31
Q

Where are the integration centres?

A

medulla

32
Q

What occurs to the afferent nerve activity in the integration centres?

A 
goes to nucleus of the tractus solitarius (NTS)
passed to 3 subsets of the medulla:
1. caudal ventrolateral medulla
2. rostral ventrolateral medulla
3. cardiac vagal nuclei
33
Q

What effect does a nerve activity in the caudal ventrolateral medulla have?

A

it is a depressor
decreases sympathetic efferent activity
decrease total peripheral resistance and BP

34
Q

What effect does a nerve activity in the rostral ventrolateral medulla have?

A

it is a pressor
increases sympathetic efferent activity
increases total peripheral resistance and BP

35
Q

What effect does a nerve activity in the cardiac vagal nuclei have?

A

sends signal to nucleus ambiguus
control cardiac vagal efferent activity
switched on - increase parasympathetic activity

36
Q

How are pressor areas activated?

A

tonically active

baroreceptors tonically inhibit it

37
Q

How are depressor areas activated?

A

not tonically active

activated by an increase in baroreceptor afferent nerve discharge

38
Q

What happens when arterial BP decreases?

A

unload arterial baroreceptors
decreases afferent nerve discharge (decreased vagal nerve activity)
decreases tonic inhibition at pressor area
increase in sympathetic nerve activity
increased HR + force (=StV) and therefore cardiac output
increase in peripheral resistance (α1)
returns BP towards normal

39
Q

What occurs when someone goes from a supine position to standing?

A

gravity causes blood to pool in legs and abdomen
decreases venous return (immediate)
decreases cardiac output and MAP (F-S law)
blood pressure fallen

40
Q

What is the body’s postural reflex to standing from supine?

A

unload cardiopulmonary and arterial baroreceptors
decrease afferent discharge via NTS/medulla
decrease vagal efferent, increase sympathetic efferent
increased HR, StV and vasoconstriction
BP restored

41
Q

How does the steady state of someone just gone from supine position to standing differ to normal?

A 
lower StV - decreases SBP
lower than normal cardiac output, 
higher HR - increases DBP 
higher than normal TPR (due to acticated sympathetic NS) - increases DBP
same BP

Hypertensiona (8 decks)

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