Lecture 2 The Autonomic Nervous System James B. Parker Ph.D. Physiology 1 Lecture Outline 2 Lecture Outline 2

The Autonomic Nervous System n OBJECTIVES: n 1. The student should be able to define the organization and function of the autonomic nervous system (ANS). n 2. The student should be able to define the effects of the ANS. n 3. The student should be able to list the receptors and neurotransmitters of the ANS. n 4. The student should be able to list the sympathetic stress response.

ANS Organization n The ANS affects visceral function and chiropractic affects the ANS, therefore, chiropractic affects visceral function n How then is the ANS organized? n A. Hypothalamus n B. Brain Stem n C. Spinal Cord n D. Visceral Reflexes

ANS Organization

n E. Sympathetic Nervous System –1. Paravertebral sympathetic chains of ganglia –2. Prevertebral ganglia n a. Celiac n b. Hypogastric –3. T-1 to L-2

ANS Organization n F. Parasympathetic Nervous System n - Craniosacral Division n G. Tissues Regulated - Involuntary Organs –1. Visceral (Hollow) Organs –2. Exocrine Glands –3. Endocrine glands –4. Blood Vessels –5. Heart

ANS Organization n H. Cell Types –1. Smooth Muscle –2. Cardiac Muscle –3. Gland Cells n I. Functions –1. Homeostatic conditions in the body –2. Coordinating body response to stress –3. Assist endocrine system reproduction

Sympathetic Nervous System n A. Thoracolumbar Division n B. Preganglionic Neuron - generally short axon in spinal column –1. Cell body in intermediolateral horn –2. Fibers pass through anterior horn

Sympathetic Nervous System –3. Synapse n a. In immediate ganglia (near spinal cord) n b. Pass upward or downward to another ganglia n c. On organ

Sympathetic Nervous System –4. 3 major central ganglia n a. Celiac ganglia (solar plexus) n b. Superior mesenteric ganglia n c. Inferior mesenteric ganglia

Sympathetic Nervous System n C. Postganglionic Neuron –1. Originate in the sympathetic chain ganglia or in one of the prevertebral ganglia

Sympathetic Nervous System –2. Destinations n a. Skeletal Nerves (about 8% are sympathetic) –1. Blood vessels (some are cholinergic) –2. Sweat glands (cholinergic) –3. Piloerector muscles of the hairs (cholinergic)

Sympathetic Nervous System b. Segmental distribution of sympathetic nerves – T1 and T2 head and neck, T3-T6 thorax, T7-T11 abdomen, T12-L2 legs c. c. Adrenal medullae –1. Medullar secretes epinephrine and norepinephrine into the blood stream –2. Fight or flight response n a. Capable of firing all at once in a coordinated fashion n b. Generalized sympathetic response

Sympathetic Nervous System n D. Functions –1. Emergency responses –2. Utilization of resources (Redistribution)

Parasympathetic Nervous System n A. Cranial-sacral Division –1. Cranial nerves III, VII, IX, X –2. 2nd & 3rd sacral spinal nerves (Sometimes 1st & 4th) n B. 75% are in the vagus nerve (X) n C. Preganglionic fibers generally synapse at site of organ

Parasympathetic Nervous System n D. Cholinergic-acetylcholine like actions –1. Restoration and buildup of body reserves –2. Elimination of waste –3. Digestion and absorption of food –4. Rest and relaxation

Neurotransmitters n A. Acetylcholine (Parasympathetic nervous transmitter) –1. Secreted by cholinergic fibers –2. All preganglionic neurons –3. All (almost) parasympathetic postganglionic neurons (some release GABA a neural inhibitor)

Neurotransmitters n B. Norepinephrine (Sympathetic transmitter) –1. Secreted by adrenergic fibers –2. All postganglionic neurons except, preganglionic fibers are cholinergic (Ach) n a. Sweat glands (Ach) n b. Piloerector muscle (Ach) n c. Some blood vessels(Ach)

Receptors n A. Acetylcholine receptors (Ach is the most prevalent neurotransmitter in the peripheral nervous system) –1. Muscarinic Receptors n a. Activated by the fungus muscarine n b. Found in the effector cells

Receptors –2. Nicotinic Receptors n a. Found in the synapse between the preganglionic and postganglionic neurons of both the sympathetic and parasympathetic systems and Skeletal muscle fibers

Receptors n B. Adrenergic Receptors –1. Alpha receptors n a. Alpha1 n b. Alpha2 n c. Excited by Norepinephrine & Epinephrine

Receptors –2. Beta Receptors n a. Beta1 n b. Beta2 n c. Excited primarily by epinephrine

Effects of Sympathetic & Parasympathetic Stimulation n SYM PSYM n EyesPupil dilation Pupil Constriction n GlandsIncreased Increased nasal, Sweating salivary, and GI secretions n GIdecreased Increased GI activity – activity n HeartIncreased decreased activity – activity

Stress Response - Sympathetic Nervous System n A. Fight or flight response n B. Mass sympathetic discharge n C. Stimulation of adrenal medulla - (epinephrine release) –1. Catacholamine –2. All effects have adrenergic receptors –3. From adrenal medulla chromaffin cells –4. Enhances mobilization of glucose and fatty acids, blood clotting and distribution, immune and tissue responses to injury

Stress Response - Sympathetic Nervous System n D. Response –1. Increased arterial pressure –2. Increased blood flow –3. Shunting of blood to active sites –4. Increased cell metabolism –5. Increased blood glucose concentration –6. Increased glycolysis in liver –7. Increased muscle strength –8. Increased mental activity –9. Increased rate of blood coagulation