BP Control Flashcards

1
Q

Pulse Pressure

A

Systolic BP - Diastolic BP

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2
Q

How to calculate mean arterial pressure

A

Diastolic BP + (Pulse Pressure)/3

heart spends more time in systole than diastole which is why pp is divided by 3

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3
Q

Factors affecting Systolic BP

A

Stroke Volume - Increased SV, increased SBP

Aortic Elasticity - Decreased elasticity, increased SBP

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4
Q

Factors affecting diastolic BP

A

Peripheral resistance - Increase PR, increase DBP

Aortic elasticity - Decrease elasticity, decrease DBP

Heart Rate - Decrease HR, decrease DBP

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5
Q

How does aging of the aorta cause hypertension in the elderly

A

Normally, the elastic aorta takes up kinetic energy from blood during systole & dampens rise in BP

During aging though, the aorta loses elasticity, causing systolic hypertension

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6
Q

Formula for Mean Arterial BP (MAP)

A

Cardiac Output x Total Peripheral Resistance

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7
Q

Typical MAP, Cardiac Output and Total Peripheral Resistance in Systemic Circulation

A

MAP - 100mmHg
Cardiac Output - 5 L/min
TPR - 20 Units (mmHg/L/min)

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8
Q

Typical MAP, Cardiac Output and Total Peripheral Resistance in Pulmonary Circulation

A

MAP - 10mmHg
Cardiac Output - 5 L/min
TPR - 2 Units (mmHg/L/min)

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9
Q

Mechanisms that support control of arterial BP

A

Pressure Sensors (in circulation) - Afferent Input

Integration centres (in CNS)

Effector Mechanisms (via ANS) - Efferent Output

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10
Q

Arterial Baroreceptors - What are they, Where, What do they do/how

A

High Pressure BP Sensors

In walls of carotid arteries & aortic arch

They detect an increase in stretch of vessels, increasing afferent nerve discharge via IX and X (vagus) cranial nerves

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11
Q

Effector Mechanisms to Control BP via ANS in heart

A

Parasympathetic - ACh, Muscarinic Receptors; decrease HR

Sympathetic - NA, B1 Adrenoceptors; Increase HR & StV

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12
Q

Effect of SNS on arteries

A

Sympathetic nervous system activates a2 adrenoceptors causing vasoconstriction, increasing resistance and thus BP

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13
Q

Low Pressure Baroreceptors - Where, What do they do/how

A

Located in pulmonary vasculature, Atrial-vena caval junctions, ventricular walls

‘volume receptors’ of the heart

Increase in transmural pressure increases afferent nerve discharge - vagus

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14
Q

What are the groups of neurons in the medulla that play a role in BP control

A

The caudal depressors only a role in highly elevated BP

**FOCUS ON MIDDLE ROW

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15
Q
How do the following values changes when going from a supine to standing position to maintain BP:
HR
Stroke Volume
Cardiac Output
Total Peripheral Resistance
A
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16
Q

Discuss the neuronal/nervous changes that occur when arterial BP drops

A

Baroreceptors reduce afferent nerve discharge. This reduces vagal nerve activity (PNS). This decreases tonic inhibition at pressor area and increase in SNS activity

Heart Rate & StV increase along with cardiac output (B1) as result
Peripheral resistance increases (a1 adrenoceptors activated)

BP returns to normal

17
Q

Discuss the neuronal/nervous changes that occur when arterial BP increases

A

Afferent nerve discharge increases; this increases vagal activitys (PNS) and decreases SNS activity

Depressor is activated & pressor’s inhibition is increased

These systems work to reduce heart rate & StV and thus cardiac output (B1)

Peripheral resistance is thus reduced (a1 adrenoceptors)

All this reduces BP to normal