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. -adrenergic (3 subtypes) a. 1, 2, and 3 receptors b. usually inhibitory c. both epi and norepi bind strongly (especially to 1) IV. Adrenergic Stimulation C. Two broad classes 2. -adrenergic (3 subtypes) 1: increase heart rate 2: smooth muscle relaxation, anabolism in skeletal muscle 3: lipolysis in adipose tissue, often causes tremors 3. both and 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