Chapter 19 - Autonomic Nervous System

ANS

1. Autonomic sensor neurons in visceral to convey info to CNS 2. Integrating centers in the CNS 3. Autonomic motor neurons propagate from CNS to various effector tissues to regulate activity of smooth muscle, cardiac muscle, and many glands 4. Enteric division - specialized network of nerves and ganglia forming an independent nerve network within the wall of the GI (gastrointestinal) tract

4 Cranial Nerves of Parasympathetic Division

1. Oculomotor CN III 2. Facial CN VII 3. Glossopharyngeal CN IX 4. Vagus CN X 3,7,9,10

Two-Neuron Chain in ANS

1st neuron in ANS pathway - *Preganglionic Neuron - in CNS, brain, or spinal cord Preeganglionic axon - extends to 2nd cell body housed w/in autonomic ganglion in PNS 2nd neuron in ANS *Ganglionic Neuron Postganglionic axon - extends from cell body to effector cells

Trunks of Sympathetic trunks

Anterior to spinal nerves and lateral to vertebral column Right and Left Trunks Sympathetic trunk ganglia house sympathetic ganglionic neuron cell bodies each with spinal nerve

Comparison with SNS and ANS

Both use sensory AND motor neurons SNS - innervates skeletal muscle fibers - >conscious voluntary movement Single lower motor neuron axon -> uninterrupted from spinal cord to one or more muscle fibers ANS - motor neurons innervate smooth muscles and either EXCITE or INHIBIT cells in viscera 2 neuron chain in series to innervate muscles and glands

Rami Communicantes

Connects sympathetic trunk to reach spinal nerve Preganglionc sympathetic axons of T1-L2 spinal nerves are carried by white rami. Myelinated Postganglionic sympathetic axons are carried from the sympathetic trunk to the spinal nerve by gray rami communicantes (or gray rami). Gray rami connect to all spinal nerves including cervical, sacral and coccygeal spinal nerves. Unmyelinated

Parasympathetic Divions

Craniosacral divison Preganglionic neurons are housed in brainstem and S2-S4 (lateral gray regions) Ganglionic neurons are either in Terminal Ganglia in target organ or intramural ganglia in the wall of target organ

Pathway of Sympathetic Post-Ganglionc Neurons

Does one of the following 1. From all ganglia of chain (gray communicantes) to anterior ramus of spinal nerve -> distributed to blood vessels, sweat glands, arrector pili muscles 2. From cervical -> supply of heart or blood vessels in brain, beck, and shoulder region 3. upper thoracic - lower abdominal, pelvic sympathetic trunkg anglia exit trunk in nerves that enter plexuses that follow blood vessels of those regions

Pathway of Sympathetic Pre-Ganglionc Neurons

Extends from white ramus into trunk ganglion -> termination or synapse 1. Synapse in first ganglion at level of entry 2. pass up or down trunk for a distance -> sympathetic chains 3. preganglionc axons pass through trunk w/o terminating -> splanchnic nerves -> extension or termination of outlying prevertabral gangli -> organs from abdominal portion of gut tube

Divisions of ANS

Parasympathetic - conservation of energy and replenishment of nutrient stores - rest and digest Sympathetic Division - preparation of body for emergencies - fight or flight - increased activity of this division results in increased alertness and metabolic activity

Anatomic Differences between Parasympathetic and Sympathetic

Parasympathetic - long preganglionic axon, short postganglionic axon Sympathetic - shorter preganglionic axon, longer postganglionic axon

Inferior mesenteric gnaglion

Postganglionc axons - intervate distal colon, rectum, urinary bladder, distal ureter, and REPRODUCTIVE ORGANS

Cervical Sympathetic Ganglia

Postganglionc axons cell bodies in superior cervical ganglion -> distribute structures in head and neck innervate sweat glands, smooth, dilation, superior tarsal of eye Middle and inferior cervical ganglia - extend postganglionic axons to thoracic viscera

Celiac ganglion

Postganglionic axons - innervate stomach, spleen, liver, gallbladder, proximal duodenum, part of pancreas

Prevertebral vs Paravertebral Ganglion

Pre - goes to abdominal portion of gut Para - goes to liver or stomach or intestines

Prevertebral (or Collateral) Ganglia

Splanchnic nerves terminate in this section Ganglia are unpaired and anterior to vertebral column Clusters around the major abdominal arteries and are named for them Sympathetic postganglionic axons extend away from ganglionic neuron cell bodies in ganglia and innervate many abdominal organs Has the following: celiac ganglion, Superior Mesenteric ganglion, Inferior Mesenteric ganglion

Sympathetic vs Parasympathetic

Sympathetic = E situations Exercise, emergency, excitement, embarrassment Longer lasting effects Pupil/blood vessel dilation, heart rate/BP increase LIVER BREAKS DOWN GLYCOGEN -> GLUCOSE Parasympathetic = SLUDD salivation, lacrimation, urination, digestion, defecation 3 decreases: heart rate, bronchoconstriction, pupil constriction

Sympathetic Division

Thoracolumbar division preganglionic neuron cell bodies are in lateral horn between T1 and L2 (spinal) Preganglionc axons travel to exit spinal cord and enter anterior roots and then T1 and L2

Splanchnic Nerves

composed of preganglionic sympathetic axons that did not synapse in sympathetic trunk ganglion Runs anteriorly from sympathetic trunk to most of viscera won't interact with other ganglions

Superior Mesenteric Ganglion

postganglionc axons - innervate distal duodenum - part of pancreas, remainder of small intesting, large intestine, uterus

ACh

released by all preganglionic axons to have an excitatory effect on ganglionic cell released by all postganglionic and a few sympathetic on the effector -> release norepinephrine if sympathetic -> inhibitory or excitatory For parasympathetic - has inhibitory or excitatory effect

Dual Innervation

visceral effectors by postganglionc axons from both ANS divisions Has opposing actions (antagonistic effect)