Control of Blood Pressure Flashcards

1
Q

List 6 determinants of capillary perfusion pressure.

A

Arteriolar factors:

1 - Endothelial influences.

2 - Myogenic influences.

3 - Metabolic influences.

Venous factors:

4 - Gravity.

5 - The respiratory pump.

6 - The musculoskeletal pump.

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2
Q

List 3 products of reflexes in the cardiovascular system.

A

1 - Release of catecholamines.

2 - Release of ADH.

3 - Activation of the renin-angiotensin system.

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3
Q

List 5 actions that trigger complex reflexes that might lead to changes in the cardiovascular system.

A

1 - Exercise.

2 - Feeding.

3 - Alerting.

4 - Thermoregulation.

5 - Reproduction.

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4
Q

What is the function of the baroreceptor reflex?

A

To regulate blood pressure.

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5
Q

What type of receptors are baroreceptors?

What do they respond to?

A
  • Stretch receptors.

- They respond to the magnitude of stretch and the rate of change of stretch.

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6
Q

To which area of the CNS does afferent activity from baroreceptors travel?

A

The nucleus tractus solitarius (NTS).

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7
Q

List 2 locations of baroreceptors.

Which nerves carry the afferent activity of each of these groups of baroreceptors?

A

1 - In the aortic arch, carried by the vagus nerve.

2 - The bifurcation of the common carotid arteries (on the internal carotid at the carotid sinus), carried by the glossopharyngeal nerve.

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8
Q

List the stages of the baroreceptor reflex in response to a fall in arteriolar blood pressure

A

*Arterioles, veins, heart, ADH.

1 - A fall in arterial blood pressure is detected by a decrease in baroreceptor activity.

2 - The CNS increases arteriolar vasoconstriction , which increases TPR.

3 - Arteriolar vasoconstriction also decreases capillary hydrostatic pressure, increasing filtration of tissue fluid into capillaries and increasing EDV (and therefore SV).

4 - The CNS also causes venoconstriction, which also increases EDV (and therefore SV).

5 - The CNS increases heart contractility (and therefore SV) and rate by increasing sympathetic activity and decreasing parasympathetic activity.

6 - Increased ADH production increases circulating volume and therefore EDV, increasing SV.

7 - The increased SV and increased heart rate result in an increased cardiac output.

8 - ABP = CO * TPR, both of which have increased.

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9
Q

Describe the neural pathway taken by parasympathetic nerves innervating the heart in the baroreceptor reflex.

A

1 - Parasympathetic preganglionics originate in the nucleus tractus solitarius (NTS).

2 - Parasympathetic preganglionics synapse with the vagus nerve at the nucleus ambiguus.

3 - Parasympathetic postganglionics innervate the SAN and AVN via the vagus nerve.

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10
Q

Describe the neural pathway taken by sympathetic nerves innervating the heart and peripheral vessels in the baroreceptor reflex.

A

1 - First preganglionics originate in the nucleus tractus solitarius (NTS).

2 - First preganglionics synapse with second preganglionics that originate in the preoptic hypothalamus.

3 - Second AND first preganglionics (the preoptic hypothalamus can be skipped) synapse with third preganglionics at the rostral ventrolateral medulla (RVLM).

4 - Third preganglionics synapse with short sympathetic preganglionics in the sympathetic chain.

5 - Short sympathetic preganglionics synapse with long sympathetic postganglionics.

6 - Long sympathetic postganglionics synapse with the SAN, AVN, arterioles and veins.

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11
Q

Describe the neural pathway taken by nerves innervating the pituitary gland in the baroreceptor reflex.

A

1 - Preganglionics originate in the nucleus tractus solitarius (NTS).

2 - Preganglionics synapse with postganglionics in the supraoptic and paraventricular nuclei.

3 - Postganglionics innervate the pituitary gland.

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12
Q

In which area of the body does the baroreceptor reflex have the strongest effect?

Why is this advantageous?

A
  • The gastrointestinal tract (GIT).

- Because the GIT contributes to 25% of TPR at rest.

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13
Q

What proportion of TPR do arterioles supplying skeletal muscle comprise at rest?

A

20%

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14
Q

Where are volume receptors located?

A

In the right atrium.

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15
Q

What type of receptors are volume receptors?

What do they respond to?

A
  • Stretch receptors.

- They respond to changes in right atrial stretch, and therefore CVP indirectly.

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16
Q

Describe the Bainbridge reflex.

Which nerve carries afferent information from the receptors, and where is the information carried to?

A

1 - The reflex is initiated by increased stretch of volume receptors.

2 - The reflex increases sympathetic activity to the heart, increasing heart rate.

3 - The reflex also decreases sympathetic activity to the kidney, increasing renal perfusion and therefore urine production (decreases blood volume), and decreasing renin release.

4 - The reflex also decreases ADH release from the posterior pituitary (decreases blood volume).

  • The vagus nerve carries afferent information from volume receptors to the nucleus tractus solitarius.
17
Q

What is the function of the Bainbridge reflex?

A

To regulate ABP over a longer time scale than the baroreceptor reflex (since the baroreceptor reflex is faster and shorter acting than the Bainbridge reflex).

18
Q

List 3 causes of decreased distension of the atrium.

A

1 - Standing (causes venous pooling).

2 - Haemorrhage.

3 - Dehydration.

19
Q

List 3 causes of increased distension of the atrium.

A

1 - When supine.

2 - Large fluid intake.

3 - Over-transfusion.

20
Q

List 3 conditions / situations in which the sensitivity and / or set point of the baroreceptor reflex can be changed.

A

1 - Exercise.

2 - Chronic hypertension.

3 - Emotional stress.