Where is adrenaline and noradrenaline secreted from?
The adrenal medulla
What are situations adrenaline and noradrenaline secreted in response to?
Fight, flight, fear, exercise, hypotension and hypoglycaemia
Where are baroreceptors located?
In the aortic arch and carotid sinus
Afferent fibres from which cranial nerves are in the carotid sinus and aortic arch?
IX (glossopharyngeal) and X (vagus)
What do baroreceptors do?
They detect and respond to changes in blood pressure
What type of receptors are baroreceptors?
Increased pressure in the artery causes distention - what effect does this have on baroreceptors?
This excites the receptors
What effect does the following have on the heart? a) increased sympathetic activity b) decreased parasympathetic activity
a) increased HR and contractility
b) increased HR
What effect does increased sympathetic activity have on blood vessels?
Why can baroreceptors not regulate blood pressure in the long term?
As baroreceptors adapt to the prevailing level of arterial pressure e.g. in animals that are hypertensive long term the baroreceptors come to accept this as normal and regulate pressure at the elevated level
What are the three other ways the baroreceptor reflex tries to increase blood volume by?
Increasing the sensation of thirst
Increasing ADH which decreases urine flow from the kidneys
Increases renin which acts to produce aldosterone which decreases Na excretion