Chapter 12 - The Autonomic Nervous System PDF

The Autonomic Nervous System Dr. Ali Ebneshahidi ebneshahidi  Autonomic Nervous System (ANS) 1. Cranial and spinal nerves that function independently, autonomously, and continuously, without conscious effort. 2. Controls smooth and cardia...

The Autonomic Nervous System Dr. Ali Ebneshahidi ebneshahidi  Autonomic Nervous System (ANS) 1. Cranial and spinal nerves that function independently, autonomously, and continuously, without conscious effort. 2. Controls smooth and cardiac muscles, and glands. 3. Regulated largely by reflexes where stimuli are detected by sensory neurons, after processing by the brain or spinal cord, motor neurons produce activities at the effector organ. 2. subdivided into sympathetic ("in agreement") and parasympathetic ("disagreement ") nerves; where in general sympathetic nerves stimulate the effector organ (except certain digestive organs) and parasympathetic nerves inhibit the effector organ (except certain digestive organs). ebneshahidi ebneshahidi ebneshahidi  Sympathetic Division most sympathetic nerves secrete norepinephrine and as a result are referred to as adrenergic fibers. location of ganglia is within few cm of CNS, along the vertebral column. sympathetic fibers originate from the thoracolumbar region of the spinal cord (mostly thoracic)[T1- L2]. short preganglionic fibers. Long postganglionic fibers. ebneshahidi  Preganglionic sympathetic neurons in the gray matter of the spinal cord produce the lat. horns. after leaving the cord via ventral root the preganglionic sympathetic fibers pass through a white ramus communicans and enter paravertebral chain ganglion forming part of the sympathetic trunk (chain). ebneshahidi  All sympathetic preganglionic fibers release Acetylcholine. Most postganglionic fibers release Norepinephrine. Postganglionic fibers run from the ganglion to the organs that they supply. ebneshahidi ebneshahidi  Parasympathetic Division preganglionic fibers of parasympathetic nerves arise from the CNS (brain stem) and sacral region of spinal cord (S2- S4). ganglia are close to visceral organs served. long preganglionic fibers. short postganglionic fibers. All fibers release Ach. (cholinergic fibers). ebneshahidi ebneshahidi ebneshahidi  Cranial Nerves with Parasympathetic Outflow 1. Oculomotor nerve III 2. facial nerve VII 3. Glossopharyngeal nerve IX 4. Vagus nerve X - when vagus nerve pass through the thorax, it send branches to following plexuses: a. Cardiac - supply the heart. b. Pulmonary - supply the lungs and bronchi. c. Esophageal- supply the esophagus. - when the main trunk of vagus nerve reaches the esophagus, it forms the Vagal Trunk. ebneshahidi  Effects of Autonomic Stimulation Skin: Apocrine gland Eccrine gland s) sympathetic: ↑ secretion P) parsympathetic: No Action Special senses: Iris of eye S) sympathetic: dilation P) parasympathic: constriction Tear gland: S) inhibitory P: greatly ↑ secretion Endocrine system: Adrenal cortex & Adrenal medulla S: ↑ secretion P: No Action ebneshahidi  Digestive system: Gall bladder S: relaxation P: contraction Intestine S: ↓ peristaltic Action P: ↑ peristaltic Action Pancreas S: ↓ secretion P: ↑secretion Respiratory system S: dilate bronchioles P: constrict bronchioles Heart muscle S: ↑rate of heartbeat P: ↓ rate of heartbeat ebneshahidi  Blood vessels suppling skin and other blood vessels S: constriction P: no action Muscles of bladder S: relaxation P: contraction Urinary sphincter S: contraction P: relaxation Penis S: causes erection P: causes ejaculation Vagina S: causes erection of clitoris P: causes contraction of vagina ebneshahidi