I. Visceral Reflexes A. All effectors except most skeletal muscle 1. glands 2. cardiac muscle 3. smooth muscles (visceral) There is really no longer a clear-cut distinction between voluntary and involuntary.

I. Visceral Reflexes B. Autonomic neurons 1. NOT somatic (which is CNS to skeletal muscle)

I. Visceral Reflexes B. Autonomic neurons 2. require 2 neurons per autonomic reflex pathway a. preganglionic b. postganglionic c. synapse with each other in autonomic ganglia d. postgangs supply autonomic effectors

I. Visceral Reflexes C. Effectors 1. skeletal muscles - flaccid paralysis w/o innervation 2. visceral effectors - function w/o stimulation a. heart - beats following denervation b. smooth muscle maintains resting tone c. ANS activity just modified (faster/slower)

I. Visceral Reflexes D. Receptors - stretch, pain, blood chemistry

II. ANS Divisions A. Sympathetic division (thoracolumbar) 1. preparation for physical activity (“fight or flight”) a. increase in heart rate and blood pressure b. dilation of respiratory passages

II. ANS Divisions A. Sympathetic division c. sweat d. inhibits some resting functions (such as digestion)

II. ANS Divisions A. Sympathetic division 2. axons emerge from spinal cord and travel to ganglia a. sympathetic chain ganglia

II. ANS Divisions A. Sympathetic division large amount of branching of pregang axons lots of divergence as well as convergence Mass activation (unit activation of sympathetic division)

II. ANS Divisions A. Sympathetic division b. pregangs synapse with postgangs in ganglia - paravertebral (chain) or (vertebral) - collateral (prevertebral)

II. ANS Divisions A. Sympathetic division c. all sympathetic postgangs arise in ganglia many more postgangs than pregangs

II. ANS Divisions A. Sympathetic division 3. adrenal glands a. cortex secretes steroids

II. ANS Divisions A. Sympathetic division b. medulla - derived from neural crest cells modified sympathetic ganglion releases epi, norepi, and some dopamine

II. ANS Divisions B. Parasympathetic division (craniosacral) 1. vegetative activities (digestion, secretion) 2. reduces heart rate and respiration 3. pregangs travel to terminal ganglia

III. ANS Neurotransmitters A. Acetylcholine (ACh) 1. secreted by all pregangs 2. parasympathetic postgangs 3. some sympathetic postgangs 4. cholinergic synapses

III. ANS Neurotransmitters B. Norepinephrine (noradrenaline) 1. most sympathetic postgangs 2. adrenergic synapses 3. other catecholamines - epinephrine (as adrenaline)

IV. Adrenergic Stimulation A. Excitatory and/or inhibitory effects B. Due to membrane receptor types

IV. Adrenergic Stimulation C. Two broad classes (both metabotropic) 1.  -adrenergic (2 subtypes) a.  1 and  2 receptors b. usually excitatory c. smooth and cardiac muscle d. epi only binds weakly

IV. Adrenergic Stimulation C. Two broad classes  1-adrenergic smooth muscle contraction a lot of vasoconstriction

IV. Adrenergic Stimulation C. Two broad classes  2-adrenergic inhibition of insulin contraction of GI sphincters

IV. Adrenergic Stimulation C. Two broad classes 2. ß-adrenergic (3 subtypes) a. ß1, ß2, and ß3 receptors b. usually inhibitory c. both epi and norepi bind strongly (especially to ß1)

IV. Adrenergic Stimulation C. Two broad classes 2. ß-adrenergic (3 subtypes) ß1: increase heart rate ß2: smooth muscle relaxation, anabolism in skeletal muscle ß3: lipolysis in adipose tissue, often causes tremors 3. both  and ß classes tend to promote “fight or flight”

V. Cholinergic Stimulation A. Usually excitatory 1. preganglionic autonomics always excitatory 2. postganglionics usually excitatory (parasympathetic) exception: decreases heart rate

V. Cholinergic Stimulation B. Receptor types 1. muscarinic: on all cholinergic target (effector) cells ACh binding can be excitatory or inhibitory metabotropic

V. Cholinergic Stimulation B. Receptor types 2. nicotinic a. on all postgang cell bodies b. adrenal medulla c. neuromuscular junction (not autonomic) d. always an EPSP upon binding of ACh

VI. Dual Innervation A. Antagonistic effects 1. sympathetics increase heart rate; parasympathetics decrease - same effector cells 2. sympathetics dilate pupil; parasympathetics constrict - different effector cells

VI. Dual Innervation B. Cooperative effects 1. act on different effectors to produce similar (desired) effects 2. saliva a. parasympathetics: watery saliva w/enzymes b. sympathetics: mucus c. both are necessary components of saliva

VII. No Dual Innervation A. Many effectors receive sympathetic only adrenal, most blood vessels, sweat glands, arrector pili muscles B. Blood pressure regulation 1. sympathetic tone (baseline frequency of action potentials) 2. creates vasomotor tone (constant partial constriction) 3. increase or decrease in action potential frequency affects tone 4. can be used to shunt blood flow