Integrated control of blood pressure
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What are baroreflexes?
A homeostatic mechanism that helps to maintain BP at a constant. It adjusts cardiac output & peripheral vascular tone to stabilise arterial pressure.
Where are the two arterial baroreceptors in the heart?
The aortic arch Carotid sinus
Where do the baroreceptors terminate?
At the nucleus tractus solitarus (NTS) in the medulla of the brain stem
What are the two nerves involved in cardiac responses?
Vagus nerve (X) - aortic arch Glossopharyngeal (IX) - carotid sinus
What is the response when there is an increased MAP?
Increased pressure = Increased baroreceptor firing = Increased PNS(vagal) tone - stimulates the nucleus ambiguus = increased Ach resulting in a decrease in HR Theres a decrease in sympathetic tone - CVLM - Inhibits the RVLM = Decreased HR and TPR
What is the response when there is a decreased MAP?
Decreased BR firing = Decreased PNS tone (this inhibits the nucleus ambiguus) = decreased Ach = increased HR Increased SNS tone (stimulates RVLM) = Increased nor. adrenaline = Increased HR, TPR
What cell bodies does the nucleus ambiguus have?
For the vagus
What does the vagus innervate?
The pacemaker regions SAN & AVN