Hypotension - Sympathetic Response
The receptors that detect hypotension are BARORECEPTORS. They are located in
The Aortic arch and Carotid sinuses. Decreased stimulation of these receptors will stimulate the cardioacceleratory centre and the vasomotor centre in the medulla of the brainstem
The Sympathetic division of the autonomic nervous system will be stimulated therefore
Adrenaline and Noradrenaline (which are hormones and neurotransmitters) are released from sympathetic nerves and the Adrenal Medulla.
Apha-1 Receptors on smooth muscle cells of arterioles and venules will cause vasoconstriction which will increase TPR
Beta 1 receptors on SA and AV nodes will increase HR (chronotropy) and increase electrical conduction speed (dromotropy)
Beta 1 receptors on cardiac muscle myocardium will increase contractility (inotropy) and therefore increase stroke volume
BP increases because BP=CO x TPR and CO =HRxSV