12. Control of Blood Pressure

Question 1

Describe the Intrinsic Correction (autoregulation) of blood flow in response to low blood pressure.

Answer 1

1. Homeostasis disturbed = inadequate local blood flow and BP
2. Precapillary sphincters open in response to chemical changes in interstitial fluid.
3. Local decrease in resistance and increase in blood flow.
4. Homeostasis restored

Question 2

What controls the intrinsic control mechanisms of blood vessels?

Answer 2

Vasodilatory metabolites, produced by metabolism in active tissues.

H+, CO2, K+, adenosine, lactate.

Question 3

How to Vasodilatory Metabolites change blood vessels?

Answer 3

In an inactive tissue the vessel is constricted in the absence of excess metabolites.

If tissue becomes active, metabolism produces chemical vasodilatory mediators (H+, CO2, K+, adenosine, lactate) which cause vasodilation. = more blood is brought to the vessels

Question 4

Effect of decreased Oxygen on pulmonary arterioles.

Why does this happen?

Answer 4

Decrease O2 + increased CO2 = constriction of arterioles
(opposite to systemic circulatory system)

Under normal O2 rich conditions, pulmonary vessels dilate and blood flow increases to absurd O2.

When O2 is depleted, pulmonary vessels constrict to shunt O2 to the alveoli cells.

Question 5

Describe the effect of inadequate blood supply or fall in blood pressure.

Answer 5

Baroreceptors are inhibited

Cardioacceloratory Centre is activated.
Cardioinhibitory Centre is inhibited.
= Increased CO + HR

Vasomotor Centres are Activated. = Vasoconstriction

Question 6

Describe the effect of rise in blood pressure.

Answer 6

Baroreceptors are stimulated.

Cardioacceloratory Centre are inhibited.
Cardioinhibitory Centre is activated.
= decreased CO + HR

Vasomotor Centres are Inhibited. = Vasodilation

Question 7

How is blood flow to the brain controlled?

Answer 7

Chemoreceptors/sensors in the medulla oblongata detect rise in CO2 or fall in pH.
= Vasodilation of cerebral vessels
= Increase blood flow to the brain.

Question 8

How is blood flow to the body controlled?

Answer 8

Chemoreceptors/sensors in the carotid artery detect rise in CO2 or fall in pH.
= Stimulate cardioacceleractory centres. Stimulate Vasomotor centres. Inhibit Cardioinhibitory sensors.
= Increase CO + HR

Chemoreceptors respond to decreased O2 = increased respiratory rate.

Question 9

What happens when autoregulation of blood flow is insufficient?

Answer 9

Stimulation of an endocrine system respond occurs in the kidney.
= long-termm increase in blood pressure (vasoconstriction e.g. angiotensin II) and blood volume (aldosterone, ADH< etc)

Question 10

Describe the role of the kidneys in regulating blood pressure.

Answer 10

• Kidneys are largely responsible for sodium and water transport. We use fluid dynamics to increase or decrease blood volumes and hence regulate blood pressure values.
• Kidney is targeted by hormones and produces hormones that are integral to blood pressure homeostasis.

Question 11

Describe the process of Long-term regulation of blood flow in response to low blood pressure.

Answer 11

1. Low BP detetected in kidneys
2. Angiotensin renin system releases renin.
3. Renin acts upon angiotensinogen, released from the liver to produce angiotensin I.
4. Angiotensin I is converted in the lungs by angiotensin converting enzyme to angiotensin II.
5. Vasoconstriction of vessels + aldosterone secretion from adrenal gland in the adrenal cortex.
   aldosterone secretion = Na+ retention increases + Fluid retention increases.

Question 12

What are the 2 principles of Angiotensin II?

Answer 12

• It is a post potent vasoconstrictor - causes decrease in blood vessel diameter = ↑ BP.
• Signal for the initiation of the release of the steroid aldosterone.
• Aldosterone is released from adrenal glands = ↑ sodium retention in the kidneys = ↑ osmosis = ↑ blood volume.

Question 13

Describe the effects of Antidiuretic Hormone (ADH).

Answer 13

Antidiuretic Hormone (ADH) = ↑ thirst = ↑drinking = ↑ fluid retention

Question 14

Describe the effects of Erythropoietin (EPO).

Answer 14

Erythropoietin (EPO) = ↑ formation of RBCs

Question 15

What happens when there is reduced blood pressure due to blood loss?

(receptors)

Answer 15

Blood Loss
= Decreased Arterial Pressure
= Baroreceptor Reflex
//
= Altered Blood Gasses
= Chemoreceptive reflex

== Cardiac Stimulation + Systemic Vasoconstriction + Fluid & Volume Redistribution

Question 16

What happens when there is reduced blood pressure due to blood loss?

(hormones)

Answer 16

Blood Loss
= Renin- Angiotensin System Activation
+ Catecholamine Release
+ Vasopressin Release

== Cardiac Stimulation + Systemic Vasoconstriction + Fluid & Volume Redistribution

Question 17

Describe the Short-term regulation of blood flow in response to low blood pressure.

Answer 17

Cardiovascular centres in CNS bring about short-term changes in BP by the sympathetic nervous system.

Question 18

Where are pressure sensors found? (blood pressure)

Answer 18

Pressure sensors are found in the walls of the internal carotid artery.

Question 19

Describe role of Chemoreceptors in the Short-term regulation of blood flow in response to low blood pressure.

Answer 19

• Bring about short-term elevation of BP. = increase in HR & vasoconstriction.
• Chemoreceptive cells in the carotid body act as chemical sensors.
• Chemosensitive cells are inside the blood vessels of the central nervous system. Both these chemosensitive cells send signals to the cardio regulatory centres in the medulla oblongata.

Question 20

Describe role of Baroreceptors in the Short-term regulation of blood flow in response to low blood pressure.

Answer 20

• Baroreceptors or pressure detectors in the aortic arch generate electrical responses that can be relayed to CNS.