Regulation of blood pressure and flow

Question 1

What do baroreceptors do?

Answer 1

They function as sensors in the homeostatic maintenance of mean arterial pressure.

Question 2

Where are baroreceptors located?

Answer 2

The aortic arch and carotid sinuses where they monitor pressure - thinner walls that can be stretched.

Question 3

What is baroreceptor nerve firing proportional to?

Answer 3

Magnitude and changes in the mean arterial pressure.

Question 4

What kind of pathway are baroreceptors a part of?

Answer 4

A negative feedback pathway that regulates mean arterial pressure via the brain (central control).

Question 5

What coordinates actions?

Answer 5

The medulla oblongata.

Question 6

What hormones are involved in the regulation of arterial pressure?

Answer 6

Adrenaline (increases MAP), angiotensin II and vasopressin (increase MAP).

Question 7

How is the autonomic nervous system involved in the regulation of arterial pressure?

Answer 7

The sympathetic increases MAP whereas the parasympathetic decreases MAP.

Question 8

What are sympathetic nerves mediated by?

Answer 8

Noradrenaline via beta adrenergic recepots and alpha-1 adrenergic receptors in arterioles (apart from skeletal muscle which is alpha2-adrenergic).

Question 9

What are parasympathetic nerves mediated by?

Answer 9

Acetylcholine via muscarinic receptors that inhibit heart rate.

Question 10

What is hypotension?

Answer 10

The large reduction in arterial pressure.

Question 11

What causes hypotension?

Answer 11

Loss of blood, salts (burns/sweating or diarrhea or vomiting) and stress or emotions.

Question 12

How can arterial pressure be increased?

Answer 12

Baroreceptors decrease firing which stimulates the sympathetic system and decreases the parasympathetic system.

Question 13

What is standing up associated with and why?

Answer 13

A drop in mean blood pressure and possible fainting. There is pooling of blood in the legs and reduced blood volume of lowering of central venous pressure. Reduced venous return, reduced end-diastolic pressure, reduced stroke volume and reduced blood pressure. The baroreceptor reflex will compensate.

Question 14

What is blood volume mostly determined by?

Answer 14

The venous volume.

Question 15

What is an important long term regulator of mean arterial pressure?

Answer 15

Blood volume - regulated by the kidneys (renin-angiotensin system).

Question 16

What is the equation for mean arterial pressure?

Answer 16

Cardiac output x total peripheral resistance.

Question 17

What is local flow regulated by?

Answer 17

Local, neural and hormonal factors. It varies between different tissues.

Question 18

What is the myogenic response?

Answer 18

Vasoconstriction of arterioles due to the stretch of smooth muscle in order to keep blood flow within a certain range.

Question 19

What metabolites can induce vasodilation?

Answer 19

A decrease in oxygen and increase carbon dioxide, increase in H+, increase in adenosine, increase in K+ and increase in osmolarity.

Question 20

When are autocoids released and what are they?

Answer 20

They are released as a result of inflammation and bleeding and include histamine, bradykinin and prostaglandins.

Question 21

What does nitric oxide and prostacyclin do?

Answer 21

Cause vasodilation.

Question 22

What does endothelin-1 do?

Answer 22

Cause vasoconstriction.

Question 23

What is active hyperemia?

Answer 23

A response to increased metabolic activity in an organ which results in a decrease in oxygen and metabolites in the organ interstitial fluid. Arteriolar dilation will occur which increases the blood flow to the organ.

Question 24

What is flow atuoregulation?

Answer 24

A response to reduced blood flow in an organ. There is decreased oxygen, metabolites and stretch in the vessel wall of the organ which results in arteriolar dilation which restores the blood flow towards the normal.

Question 25

What happens if the body is cold, fearful or there is a loss of blood?

Answer 25

Sympathetic discharge is increased and arterioles vasoconstrict and there is diverted bloodflow to essential organs.

Question 26

What happens if the body temperature is increased?

Answer 26

There is reduces sympathetic discharge and arterioles vasodilate. There is blood flow to the skin to allow cooling.

Question 27

Where is vasopressin released?

Answer 27

The posterior pituitary gland.

Question 28

What does atrial natriuretic peptide do and where is it released?

Answer 28

It causes vasodilation and is released from the cardiac atria.

Question 29

What does the body need to do when exercise is increased?

Answer 29

Boost O2 uptake and CO2 removal; increase blood flow to muscles, heart and skin; stabilise arterial blood pressure (despite changes in cardiac output and peripheral resistance).

Question 30

What does the brain do to increase cardiac output?

Answer 30

It switches off baroreceptors, as it doesn’t want to cause the opposing effect.

Question 31

What nervous systems need to be increased and decreased to boast cardiac output?

Answer 31

Reduce the parasympathetic system and increase the sympathetic nervous system.

Question 32

What happens to the blood flow to organs such as the kidneys and abdominal organs in strenuous exercise?

Answer 32

It is decreased.

Question 33

What happens to the total peripheral resistance during exercise?

Answer 33

It decreases.

Question 34

What happens to the heart rate during exercise?

Answer 34

It increases.

Question 35

What happens to the stroke volume during exercise?

Answer 35

It increases.

Question 36

In which situations does forced expiration against a closed or narrowed airway occur?

Answer 36

Coughing, lifting heavy weights, clearing ears and defecation.

Question 37

What does forced expiration against a closed or narrow airway cause?

Answer 37

An increase in intrathoracic pressure.