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Cardiorespiratory Biology > Control of Blood Pressure > Flashcards

Control of Blood Pressure Flashcards

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1
Q

why is blood pressure so tightly controlled

A

BP - driving force of tissue perfusion
too low bp - tissue will not perfuse properly
too high bp - pathological damage occurs in tissues

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2
Q

poor renal perfusions lead to

A

drop in filtration and acute kidney injury

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3
Q

poor brain defusion leads to

A

unconsciousness and death

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4
Q

too high blood pressure in the eye

A

retinopathy (damage to the capillaries in the eye)

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5
Q

too high blood pressure in the nephrons

A

– nephropathy (damage to the nephrons in the kidney)

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6
Q

too high blood pressure in the CVS

A

remodelling of the cardiovascular system (both heart and vasculature)

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7
Q

pressure gradient /_\

A

flow (Q) x Resistance (R)

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8
Q

flow is equal to

A

pressure gradient / resistance

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9
Q

how does flow vary in relation to pressure gradient

A

• Flow varies proportionally with the pressure gradient and inversely with resistance

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10
Q

mean arterial pressure

A

product of the volume of blood in the
circulation and the resistance to flow
– mean arterial pressure = cardiac output x total peripheral resistance

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10
Q

mean arterial pressure

A

product of the volume of blood in the
circulation and the resistance to flow
– mean arterial pressure = cardiac output x total peripheral resistance

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11
Q

systemic arterial pressure

A

120/80 mmHg

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12
Q

pulmonary arterial pressure

A

25/10 mmHg

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13
Q

Systemic Pulse Pressure

A

40 mmHg

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14
Q

Pulmonary Pulse Pressure

A

15mmHg

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15
Q

Systemic Mean Arterial Pressure

A

93 mmHg

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16
Q

Pulmonary Mean arterial pressure

A

15

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17
Q

Systemic capillary pressure

A

17

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18
Q

pulmonary capillary pressure

A

6-10

19
Q

systemic venous pressure

A

0-4

20
Q

pulmonary venous pressure

A

2-6

21
Q

how is blood pressure monitored and mediated

A 
baroreceptor reflex 
Sensory afferents (baroreceptors) -> Central relays -> CVS centres of brain stem (medulla oblongata) -> effector efferents (innervating heart and blood vessels)
22
Q

what do baroreceptors sense

A

rate of rise in pressure and the magnitude of pressure
– rate = dynamic sensitivity
– magnitude = static sensitivity

23
Q

as the arterial pressure increases what happens to the baroreceptors

A

baroreceptor firing rate increases too

24
Q

A fibres of baroreceptors

A

fewer - fast conducting (small diameter unmyelinated)
high threshold 70-140mmHg
no. activated increases as pressure rises

25
Q

where is the primary site for regulating SNS and PNS outflow

A

medulla oblongata

26
Q

what part of the medulla oblongata receives input from baroreceptors and chemoreceptors

A

nucleus tractus solitarius

27
Q

what modifies the activity of the medullary centres

A

hypothalamus and higher centres

28
Q

how does the venous return change when in the supine position

A

When supine, venous return is increased

– effect of gravity is reduced and so preload is ample (Starling’s Law)

29
Q

how does venous return change when standing and why

A

On standing, gravity causes venous pooling and venous return falls
– with falling preload, so cardiac output drops (Starling’s Law again)
– as so does cardiac output (since VR = CO

30
Q

how does a fall in cardiac output change the blood pressure

A

A falling cardiac output leads to a decrease in blood pressure
– MAP = CO x TRP, so if CO falls so does MAP

31
Q

baroreceptor reflex

A

drop in blood pressure
firing of baroreceptors
central control - medulla and hypoth
drop in PNS - increase heart rate
Increase in SNS - increase force of contraction, venoconstriction and vasoconstriction
Thus increasing peripheral resistance and cardiac output

32
Q

cardiac effects of baroreceptor reflec

A

– increased heart rate (due to increased SNS/decreased PNS)
– increased contractility (due to increased SNS)
– increased preload (due to SNS venoconstriction)
– overall increase in cardiac output

33
Q

vascula r effect of baroreceptor reflex

A 
increased vasoconstriction (due to increased SNS)
– overall increased in total peripheral resistance
34
Q

how can chemoreceptor in carotid body induce change in blood pressure

A

pH/PaO2

sensors in carotid bodies, primarily involved in ventilation control

35
Q

cardiopulmonary reflexes

A

contribute to overall circulatory regulation

– diverse group of receptors located mainly on low pressure side of circulation

36
Q

how long will baroreceptor reflex last

A

1-2 days

37
Q

long term regulation example

A

fluid regulation

38
Q

examples of fluid regulation

A

renin-angiotensin system (RAS)
– anti-diuretic hormone (vasopressin)
– natriuretic peptides

39
Q

Renin-Angiotensin System

A 
Angiotensinogen (453 aa) - from liver
SNS drops = increase in blood pressure
Angiotension I - inactive precursor
Angiotensin II - > vasocontriction
Aldosterone - promotes water expansion by increasing Na+ retention 
Salt and water retention
40
Q

Renin-Angiotensin System is regulated

A

by production of renin

41
Q

when is renin relesaed

A

in response to SNS activity particularly due

to low blood pressure and/or volume

42
Q

how is renin released

A

SNS activation via the baroreceptor reflex (β1
-AR)
– intrarenal stretch receptor (juxtaglomerular cells)

43
Q

hypertension

A 
Consistent readings with a systolic over 140 mmHg or a diastolic over
90 mmHg (Grade I)
44
Q

grade II hypertension

A

150/100mm

45
Q

grade II hypertension

A

150/100mm hG

46
Q

HOW DOES SYSTOLIC Pressure change with age

A

~120 mmHg at 20 to an average of
160 mmHg by 70 years of age
– mainly due to arterial stiffening

Cardiorespiratory Biology (25 decks)

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