Cardiovascular Regulation

Autoregulation

Local control at blood vessel site causing immediate localised homeostatic adjustments

Local factors that cause vasodilation

hypoxia = decreased partial pressure of oxygen, hypercapnia = increased partial pressure of oxygen, acidosis = decreased pH or increased hydrogen ion concentration, hyperkalaemia = increased concentration of extracellular potassium ions, increased adenosine concentration, increased temp, increase osmolarity

Neural mechanisms

Respond quickly to changes such as sympathetic system, controlled by cardiovascular centres/vasomotor centre (cluster of sympathetic neurons in medulla that oversee changes in blood vessel diameter) in medulla oblongata

Function of cardiovascular centres

Maintains vasomotor tone, receives input from baroreceptors, chemoreceptors and higher brain centres

Endocrine mechanisms

Direct long term changes

Endocrine mechanisms - renin-angiotensin-aldosterone system (RAAS)

Increases bp by causing powerful vasoconstriction, increases bp by increasing blood volume

Endocrine mechanisms - antidiuretic hormone (ADH)

Increases bp by increasing blood volume, may also cause vasoconstriction

Endocrine mechanisms - erythropoietin (EPO)

Released at kidney, responds to decreased bp or low oxygen content in the blood, stimulates red blood cell production which increases bp

Baroreceptors

Located in carotid sinus and aortic arch, respond to degree of stretch in arterial walls

How baroreceptors function

High bp = more stretch in arterial walls, baroceptors send action potentials to medulla, medulla responds to reduce bp to normal range

Chemoreceptors

Sense changes in the composition of arterial blood

Peripheral chemoreceptors

In carotid and aortic bodies, highly sensitive to hypoxia, moderately sensitive to hypercapnia and acidosis

Central chemoreceptors

In medulla oblongata, highly sensitive to hypercapnia and acidosis

Baroreceptors and high BP

Increase in map sensed by receptors, increase in APs to medulla (medullary inhibitory area), sends messages via parasympathetic system to heart and reduces effect of sympathetic system, vasodilation at arterioles and decreased hr and sv = decreased map

Chemoreceptors and low BP

Senses change in pH/carbon dioxide/oxygen, sends message to medullary vasomotor centre, vasoconstriction at arterioles and increased hr and sv = increased map