Regulation of blood pressure and flow Flashcards
What do baroreceptors do?
They function as sensors in the homeostatic maintenance of mean arterial pressure.
Where are baroreceptors located?
The aortic arch and carotid sinuses where they monitor pressure - thinner walls that can be stretched.
What is baroreceptor nerve firing proportional to?
Magnitude and changes in the mean arterial pressure.
What kind of pathway are baroreceptors a part of?
A negative feedback pathway that regulates mean arterial pressure via the brain (central control).
What coordinates actions?
The medulla oblongata.
What hormones are involved in the regulation of arterial pressure?
Adrenaline (increases MAP), angiotensin II and vasopressin (increase MAP).
How is the autonomic nervous system involved in the regulation of arterial pressure?
The sympathetic increases MAP whereas the parasympathetic decreases MAP.
What are sympathetic nerves mediated by?
Noradrenaline via beta adrenergic recepots and alpha-1 adrenergic receptors in arterioles (apart from skeletal muscle which is alpha2-adrenergic).
What are parasympathetic nerves mediated by?
Acetylcholine via muscarinic receptors that inhibit heart rate.
What is hypotension?
The large reduction in arterial pressure.
What causes hypotension?
Loss of blood, salts (burns/sweating or diarrhea or vomiting) and stress or emotions.
How can arterial pressure be increased?
Baroreceptors decrease firing which stimulates the sympathetic system and decreases the parasympathetic system.
What is standing up associated with and why?
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.
What is blood volume mostly determined by?
The venous volume.
What is an important long term regulator of mean arterial pressure?
Blood volume - regulated by the kidneys (renin-angiotensin system).
What is the equation for mean arterial pressure?
Cardiac output x total peripheral resistance.
What is local flow regulated by?
Local, neural and hormonal factors. It varies between different tissues.
What is the myogenic response?
Vasoconstriction of arterioles due to the stretch of smooth muscle in order to keep blood flow within a certain range.
What metabolites can induce vasodilation?
A decrease in oxygen and increase carbon dioxide, increase in H+, increase in adenosine, increase in K+ and increase in osmolarity.
When are autocoids released and what are they?
They are released as a result of inflammation and bleeding and include histamine, bradykinin and prostaglandins.
What does nitric oxide and prostacyclin do?
Cause vasodilation.
What does endothelin-1 do?
Cause vasoconstriction.
What is active hyperemia?
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.
What is flow atuoregulation?
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.
