11. Blood Pressure Flashcards by Madison Chu

Large arteries:

Elastic vessels with high

blood flow, under high pressure

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Small arteries/arterioles:

Strong muscular
walls allowing them to regulate their
lumen size and thus resistance. The high
resistance results in a large pressure drop.

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Capillaries:

exchange vessels, low flow,

thin walls

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Veins:

Smooth muscle allows modulation

of the diameter.

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Capacitance vessels:

example

can “store” large changes in blood volume with little
change in pressure
vein

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When veins are constricted large quantities of blood are
transferred to the heart thereby increasing _______ _____
Any given change in volume within the arterial tree results in
larger increases in pressure than in ____

cardiac output

veins

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Compliance

The stretchability at various points along the P/V curve. i.e. the local change in volume for a given pressure change. Reflects the elasticity of the vessel.

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Blood pressure (mmHg)

is the force exerted by the blood against any unit area of vessel
wall

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Mean Systemic Arterial pressure=?
What is Systolic
Distolic

= ~100 mmHg
Systolic ~ 120 mmHg
Distolic ~ 90 mmHg
Does tends to increase with age

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Mean Pressure formula=

MAP = CO x TPR

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Determinants of Pulse Pressure

Systolic pressure
- Aortic compliance
- Stroke volume (and ejection rate)
Diastolic pressure
- Aortic compliance
- Diastolic run off:
Heart rate
Total peripheral resistance

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Pulse pressure =

Systolic pressure – diastolic pressure

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During ____the aorta stretches to

absorb the blood

systole

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Flow continues during diastole due to
_______nature (elastic recoil) of
blood vessels

compliant

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The more _____ large blood vessels

the smaller the pulse pressure.

compliant

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The compliance of the arteries ensures
capillary flow continues throughout the
cardiac cycle. Flow becomes _________by the time it reaches the
_____arterioles

nonpulsatile

small

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Compliance (∆V/ ∆P) of the aorta tends to decrease with

age

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As a result of a decrease in compliance:

Systolic pressure increases

- Diastolic pressure may decrease

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A less compliant aorta will result in a larger

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pulse pressure

Increasing the stroke volume delivered

to the aorta increases

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the arterial pulse

pressure

SV determined by:

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preload
afterload
chronotropy
Inotropy

exercise can increase ________ pressure

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systolic pressure

Diastolic pressure is determined by the

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“diastolic run off”, i.e. the ability of the

blood to flow forward,

Diastolic pressure is dependent on:

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• Total peripheral resistance (increased
resistance increases diastolic
pressure)
• Heart rate (increased heart rate
increases diastolic pressure)

Different mechanisms dominant in blood pressure control over different time scales:

``` •Short term: neural reflexes •Minutes to hours: hormonal (Ang II) and fluid shifts •Hours to days: blood volume regulation (renal mechanisms) ```

Blood pressure control comprises | multiple mechanisms and a high amount of ?

redundancy i.e. backups to cope with changes in environmental factors

The ______ rapid changes in arterial pressure ensure that perfusion (delivery of blood to a capillary bed) of vital organs remain adequate during day to day activity

Buffers

Increase in arterial pressure results in | an increase in what firing?

in baroreceptor firing | afferent activity

``` • Increase in activity to the ________control centres results in an increase in vagal activity and inhibition of _______nerve activity (_____pathway) ```

cardiovascular sympathetic efferent

The decrease in cardiac output and vascular resistance restores ________

arterial pressure

Receptor endings: located in the adventitia of the ??? i.e. in large arteries

carotid | bifurcation and aortic arch,

Afferent activity carried in: | Carotid sinus nerve –

``` glossopharyngeal nerve (IX cranial) ```

Afferent activity carried in: | Aortic depressor nerve –

vagus (X cranial)

Pressure-activity relationship of the arterial baroreceptors

Response is almost linear over physiological range, in the presence of an arterial pulse

Baroreceptor responses to a | step change in pressure

Stretch receptors: increased stretch = increased firing. Mediated by non-selective cation channels. Very sensitive to rapid changes in pressure, but show adaptation

Afferent baroreceptor endings 1st | synapse in the

NTS (Nucleus tractus | soltarius).

Interneurons project to both :

vagal and | sympathetic pathways:

Vagal activity activated via the

``` Nucleus Ambiguus (NA), and dorsal motor nucleus. ```

2. Sympathetic activity pathway | involves the _ _ _ _

caudal ventrolateral medulla (CVLM) INHIBITING the rostral ventrolateral medulla (RVLM)

Peripheral chemoreceptor reflex come from?

carotid bodies and aortic bodies (i.e. | very close to the baroreceptor endings). Central - medulla.

chemoreceptor reflex Respond to

decrease in arterial oxygen (peripheral) or pH or increase in arterial CO2 (central) . Needs to be big change in pressure!

chemoreceptor reflex Sensory information carried in

glossopharyngeal and vagus nerve (i.e. afferent nerves fibres are in the same bundles as the baroreceptor afferents)

chemoreceptor reflex Primary cardiovascular response to a reduction in oxygen is

an increase sympathetic tone and vasoconstriction. Cardiac effects are complicated

cerebral ischemia

is a condition in which there is insufficient blood flow to the brain to meet metabolic demand An “emergency” or “last ditch” response. Unsustainable

CNS ischemic response Only seen once BP is ? Responds to high what or low what? Dramatic increase in what activity?

~ 60 mmHg, and strongest when BP <20 mmHg. Responds to high CO2 or low pH as a response to decreased brain blood flow sympathetic activity driving increased peripheral resistance.

Cerebral | Ischemia affects what body systems?

Vasomotor Center Incr Sympathetic Activity Incr Arterial Pressure

11. Blood Pressure Flashcards

(46 cards)