Chapter 14

Nervous System Central Nervous System (CNS) Brain Spinal Cord Peripheral Nervous System (PNS) Motor (efferent) Autonomic (involuntary) Sympathetic (Fight or flight)- adrenergic Parasympathetic (Rest and digest)- cholinergic Somatic (voluntary) Sensory (afferent) Human Nervous System Divisions Integration & Command Info in & out

Comparing Somatic and Autonomic Effectors Innervates skeletal muscle Innervates visceral organs and glands Efferent pathways Single axon = faster signal Two axons = slower signal Target organ responses Cholinergic synapses  exite Cholinergic, adrenergic, or noradrenergic synapses  excite or inhibit

Autonomic Nervous System Stabilize internal environments Adjustments from changes to sensory stimuli Dual innervation 2 divisions counter the effects of each other Parasympathetic Nonstressful situations (rest and digest) Sympathetic Emergency or threatening situations (fight or flight) Rare in actuality Antagonistic relationship with continuous adjustments by both Anatomical characterizations Origin: craniosacral or thoracolumbar regions Length of fibers: long preganglionic, short post- or opposite Location of ganglia: in effectors or close to spinal cord

Parasympathetic Roles D division (digest, defecate, diuresis) Pupils constrict Stimulates salivary, lacrimal, and pancreas glands Decrease heart rate Causes contraction and emptying of hollow organs: Bladder, gallbladder, stomach, intestines (peristalsis) Vasodilation of penis (erection) No effect on blood vessels

Sympathetic Roles E division (exercise, excitement, emergency, embarrassment) Dilates pupils Inhibits secretion of glands Stimulates sweating Stimulates arrector pili Stimulates medulla of adrenal gland to secrete epi- and norepinephrine Increases heart rate Decreases digestive processes Decreases urine output Causes ejaculation Stimulates glycogenolysis in liver (glucose release) Blood vessel constriction/dilation and blood coagulation Bronchiole dilation

CN III From midbrain  ciliary ganglia CN VII From pons  pterygopalatine and submandibular ganglia CN IX From medulla  otic ganglia CN X (90%) From medulla  cardiac, pulmonary, esophageal, and abdominal aortic (celiac, superior mesentric, and hypogastric) plexuses S2 – S4 Lateral gray spinal mater  pelvic splanchnic nerves into the inferior hypogastric plexus Craniosacral Division

Pre- from gray matter in lateral horns of T1 – L2 to sympathetic trunk via white rami communicates Synapse varies W/ a postganglionic neuron w/i same ganglion (1) Ascend/descend w/i sympathetic trunk to another ganglion (2) Pass through ganglion w/o synapsing (collateral ganglia or adrenal medulla)(3) Thoracolumbar Division

Trunk Ganglia Post- enter rami via gray rami communicates Superior cervical ganglion Dilates pupils Inhibit nasal and salivary secretions Stimulates sweating, contraction of arrector pili muscles, and vasodilation Branches to carotid body, larynx, and pharynx Middle cervical ganglion Heart and skin Inferior cervical ganglion Heart, aorta, bronchiole dilation, and esophageal sphincter constriction

Collateral Ganglia Pre- form splanchnic nerves which synapse w/ collateral ganglia Post- from collateral ganglia to effectors Greater splanchnic nerve Celiac ganglia Stomach, adrenal medulla, liver, kidney, and intestine Lesser splanchnic nerve Superior mesenteric (via celiac) Small intestine Lumbar splanchnic nerve Inferior mesentreric ganglion Large intestine Hypogastric ganglion Bladder, urethra, and genitalia

ANS Neurotransmitters Acetylcholine (cholinergic fibers) All pre- and all parasympathetic post- Nicotinic receptors (stimulatory) Skeletal muscle, all ganglionic neurons, and adrenal medulla Muscarinic receptors (stimulatory or inhibitory) All parasymapthetic targets and some sympathetic organs Norepinephrine (adrenergic fibers) Most sympathetic post- Alpha (generally stimulatory) Beta (generally inhibitory)

Select ANS Effecting Drugs Atropine Anticholinergic (blocks muscarinic receptors) Prevent salivation, dilate pupils, and dry up respiratory secretions Neostigmine Anticholinesterase Treat myasthenia gravis by preventing ACh degradation Ephedrine Stimulates alpha adrenergic receptors Beta-blockers Inhibit beta receptors Reduce heart rate and arrhythmias w/o disrupting other sympathetic effects