Regulation of Arterial Blood Pressure and Blood Volume

Question 1

What types of receptors help regulate release of hormones to regulate flow and pressure?

Answer 1

Arterial and cardiopulmonary baroreceptors
Arterial chemoreceptors
Pulmonary stretch receptors
Chemosensitive receptors in heart and viscera
‘Ergoreceptors’ in skeletal muscle (metabolites produced during exercise)
Trigeminal receptors (exposure of face to water, “diving reflex”)

Question 2

What are baroreceptors?

Answer 2

Sensory nerve endings that signal the CNS to changes in arterial blood pressure

Question 3

How do baroreceptors function?

Answer 3

1) they inhibit sympathetic activity and promote parasympathetic activity
2) they serve as a negative feedback mechanism to changes in blood pressure

Question 4

What two neural pathways are involved in sensing changes in blood pressure?

Answer 4

Carotid sinus nerves (CN IX)

Aortic depressor nerves (CN X)

Question 5

What factors determine baroreceptor activity?

Answer 5

1) Mean arterial pressure
2) Rate of change in pressure [fast changes trigger fast response]
3) Large artery compliance

Question 6

What is the pressure threshold for a baroreceptor?

Answer 6

The minimum pressure at which baroreceptors fire (usually 40-60 mm Hg)

Question 7

What is the sensitivity of a baroreceptor?

Answer 7

The slope of an activity-pressure relationship; sensitivity is usually highest near baseline

Question 8

What is the saturation pressure?

Answer 8

The pressure above which baroreceptors no longer fire with increasing intensity

Question 9

How does a baroreceptor respond to increasing arterial blood pressure?

Answer 9

It sends signals to the CNS that will ultimately promote:

1) increased parasympathetic activity
2) decreased sympathetic activity
3) decreased vasopressin release

Question 10

How does a baroreceptor respond to decreasing arterial blood pressure?

Answer 10

It sends signals to the CNS that will ultimately promote:

1) decreased parasympathetic activity
2) increased sympathetic activity
3) increased vasopressin release

Question 11

What happens to baroreceptors during sustained changes in blood pressure?

Answer 11

Baroreceptors adapt to the sustained changes as a new normal

Question 12

How are baroreceptors affected in chronic hypertension?

Answer 12

Their activity reduces and their sensitivity to changes reduces

Question 13

What other conditions can reduce baroreceptor effectiveness?

Answer 13

atherosclerosis, myocardial ischemia and infarction, heart failure, diabetes mellitus, obesity, and aging

Question 14

What are consequences in the reduction of baroreceptor sensitivity?

Answer 14

1) Increased variability in blood pressures
2) Increased risk of arrhythmias and sudden heart death
3) Promotes high sympathetic activity

Question 15

Which receptors are primarily responsible for detecting volume changes?

Answer 15

Cardiopulmonary (vagal afferent) baroreceptors

Question 16

How do cardiopulmonary receptors respond to diminished blood volume?

Answer 16

Promote pathways that:

1) Increase sympathetic activity
2) Increase vasopressin

Question 17

How do cardiopulmonary receptors respond to heightened blood volume?

Answer 17

Promote pathways that:

1) Reduce sympathetic activity
2) Reduce vasopressin

Question 18

What are long term factors that influence blood volume and pressure?

Answer 18

1) Renal mechanisms–fluid and sodium retention
2) Arterial wall thickening
3) Neurohormonal/paracrine effects
4) Environmental factors
5) Genetics

Question 19

What is the role of the carotid body cell?

Answer 19

A glomus cell detects changes in oxygen, carbon dioxide, and pH in the blood.

Question 20

What is the effect of glomus cell activation?

Answer 20

The CNS promotes increased respiration, sympathetic activity to increase vascular resistance, and parasympathetic activity to decrease heart rate; the change in ventilation will negate the latter two.

Question 21

What is the Bezold-Jarisch reflex?

Answer 21

Certain conditions like ischemia promote chemoreceptors that trigger both vagal and sympathetic afferent activity. The sympathetic system will attempt to increase heart rate and arterial pressure whereas the parasympathetic system will try to slow these down

Question 22

How does a patient with the Bezold-Jarisch reflex happening present?

Answer 22

Has bradycardia and hypopnea