PHYL2001 Lecture Notes - Lecture 3: Cold Shock Response, Parasympathetic Nervous System, Peripheral Chemoreceptors
Document Summary
Tends to dominate in quiet, relaxed situations: often termed rest and digest . Under these conditions body is concerned with general housekeeping activities. Parasympathetic: digestion emptying of the urinary bladder, secretion. Parasympathetic system can also rapidly slow down the activities enhanced by sympathetic stimulation i. e. bring the body back to normal after stress has passed. Therefore the dual innervation of organs by the sympathetic and parasympathetic systems allow precise control over an organ"s activity. Exceptions: not all organs receive dual innervation. Receive only sympathetic nerve fibres: sympathetic and parasympathetic stimulation are not always antagonistic in their effects. E. g. salivary glands have both sympathetic and parasympathetic innervation but both are stimulatory for saliva secretion. The dogma is that the opposite effects of sympathetic and parasympathetic on the heart are actively separately or sequentially. However evidence now mounting that both systems can be activated simultaneously in certain situations leading to pathophysiological consequences.
