36 - Blood Control and Hypertension Flashcards

1
Q

Short-term blood pressure regulation

A

Primarily neural.

The baroreflex

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2
Q

Part of brain that mediates baroreflex

A

Brainstem autonomic centres, in the medulla.

Nucleus and tractus solitarius

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3
Q

Baroreceptor locations
1)
2)
3)

A

1) Carotid sinus
2) Aortic arch
3) Pre-glomerular arteriole (near justaglomerular apparatus)

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4
Q

Carotid sinus

A

Thin-walled, highly-innervated, dilated bulb at base of internal carotid.
Baroreceptor

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5
Q

Neural signals from baroreceptors

A

More stretch leads to more neural firing.

Therefore brain responds to less firing with sympathetic activation.

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6
Q

Significance of thin wall of carotid sinus

A

Thinner wall is more compliant than a thicker one.

Therefore more sensitive (more easily-deformable) to changes in blood pressure.

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7
Q

How quickly can baroreceptors respond to changes in bp?

A

Within one cardiac cycle

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8
Q

How does your body normally assess adequacy of blood flow to organs?

A

Using blood pressure monitoring

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9
Q
Effect of sympathetic stimulation on cardiovascular function 
1)
2)
3)
4)
5)
A

1) Increase heart rate
2) Decrease AV conduction time
3) Increase cardiac contractility (Ca2+ released in cardiac cells upon sympathetic stim)
4) Increase total peripheral resistance (keep blood in arteries)
5) Increase venous tone (keep blood in arteries)

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10
Q

Effect of parasympathetic stimulation on cardiovascular system
1)
2)
3)

A

1) Increase AV conduction time
2) Decrease heart rate.
3) Doesn’t really cause vasodilation (except in blood vessels of sweat glands)

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11
Q

Overall effect of baroreflex

A

Stabilises blood pressure, smooths out variations

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12
Q

Effect of de-innervating carotid baroreceptors

A

Have great swings in bloodpressure with things like speaking, standing up, eating, defecating.

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13
Q

How quickly can the threshold for baroreflex be changed?

A

Resets to new pressure levels within one to two days

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14
Q

When to carotid baroreceptors stop firing to medulla?

A

Below about 60mmHg

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15
Q

How is blood pressure below 60mmHg detected?

A

By chemoreceptors

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16
Q

Where are chemoreceptors located?

A

Carotid and aortic bodies outside arteries

17
Q

What do chemoreceptors detect?

A

Low O2, high CO2, pH differences.

Linked to poor organ O2 perfusion.

18
Q

Mean male MAP

A

94

19
Q

Mean female MAP

A

89

20
Q

Shape of blood pressure distribution graph in population

A

Unimodal (one peak), tail towards upper end of distribution)

21
Q

Progression of systolic blood pressure with age

A

Increases with age

22
Q

Progression of diastolic blood pressure with age

A

Increases until ~60 years of age.

After 60, stops increasing, or decreases because of hardening of arterial walls (decreased compliance)

23
Q

Time of greatest blood pressure increase

A

Just after birth

24
Q

When do male and female mean MAPs diverge?

A

At puberty.

25
Q

How do body size and bp correlate?

A

Positively

26
Q

Diurnal variation of bp
1)
2)
3)

A

1) About 20mmHg lower at night
2) Less variation at night
3) Less sympathetic stimulation at night

27
Q

Seasonal variation of bp
1)
2)

A

1) About 3mmHg lower in summer than winter

2) Because of increased heat (vasodilation), sweat (water loss), increased body weight in winter.

28
Q

Why has the cutoff for hypertension been falling for the past few years?

A

Because the cutoff is calculated by the earliest time that treatment benefits outweigh negatives.
Now drugs are safer, more efficacious, so makes sense to treat earlier.

29
Q

Current cutoff for hypertension

A

140mmHg systolic