In: Anatomy and Physiology
describe the physiological functions of parasympathetic neurons
The Parasympathetic neurons are of two types: Preganglionic and postganglionic. Preganglionic neurons arise from the brain as well as from spinal cord. In the brain they arise from visceral efferent nuclei and leave the cranium through 3rd, 7th, 9th and 10th cranial nerves -cranial outflow. In the spinal cord, they arise from lateral grey column of 2nd 3rd and 4th sacral segments-sacral outflow.
The ganglia are located near to the effector organ therefore the preganglionic neurons are longer and postganglionic neurons are shorter. Both the neurons release Acetylcholine as their neurotransmitter.
Organ | Parasympathetic effect |
Pupil of the eye | constriction |
Lacrimal gland | secretomotor |
Salivary gland | produce watery saliva |
Bronchial gland | increases secretions |
Bronchioles | constriction |
Muscles of GIT | increases peristalsis but relaxes the sphincters |
Glands of GIT | increases secretions |
Muscles of bladder | contraction of the muscle of bladder wall but relaxation of the sphincter |
Blood vessels | no effect |
Sweat glands | no effect |
Muscles of hair follicle | no effect |
Penile tissue | causes erection |
Heart | decrease heart rate |