Ch. 15 The Autonomic Nervous System

Objectives Know the general function of the ANS Be able to describe the characteristics of the ANS Know the two divisions of the ANS Be able to describe the anatomical differences between the parasympathetic and sympathetic systems Know the role of the adrenal medulla in the sympathetic system

Divisions of Nervous System legacy.owensboro.kctcs.edu

Autonomic Nervous System System of motor neurons that innervates smooth, cardiac muscle, and glands Involuntary nervous system General visceral motor system

Characteristics Effectors – Cardiac and smooth muscle – Glands Efferent Pathway – Involves two neurons Ganglia – Preganglionic neuron > preganglionic axon > ganglionic neuron > postganglionic axon > effector Neurotransmitter – All preganglionic neurons release acetylcholine – Norepinephrine, acetylcholine – Excitatory, inhibitory

Divisions of ANS Sympathetic – Fight or flight – Norepinephrine – Adrenergic fibers Parasympathetic – Rest and digest – Acetylcholine – Cholinergic fibers Dual innervation – Counterbalance – Tonic activity Ongoing activity of both divisions virtual.yosemite.cc.ca.us

Parasympathetic Division Anatomically simpler Craniosacral origin – Cranial nerves III, VII, IX, X Oculomotor – Smooth muscle Facial – Lacrimal and mucus glands – Salivary glands Glossopharyngeal – Parotid glands Vagus – Innervates thoracic and abdominal viscera – Splanchnic nerves S2 - S4 Innervate pelvic organs antranik.org

Sympathetic Division Anatomically more complex – Innervates more organs Thoracolumbar origins – T1 – L2 Sympathetic trunk ganglia – Paravertebral ganglia studyblue.com

Chain Ganglia Synapse within same chain ganglion Ascend or descend then synapse in chain ganglion Pass through chain ganglion without synapsing – Collateral ganglia anatomy.med.umich.edu

Sympathetic Chain Ganglia chain ganglia Collateral ganglia – Unpaired – Only in abdomen and pelvis – Lie on abdominal aorta Celiac, sup. and inf. Mesenteric, inf. hypogastric wps.aw.com

Adrenal Medulla Inner portion of the adrenal gland Largest sympathetic ganglia – Chromaffin cells Secrete norepinephrine and epinephrine into blood stream wikis.lib.ncsu.edu