Types of Neurons of ANS To review the different types of neurons associated with the ANS. Ganglion – Collection of nerve cell bodies To clearly identify the position and role of the outside of the CNS. sympathetic trunk & collateral ganglia. To address the two different types of receptors for Preganglionic Neurons – CB in CNS which neurotransmitters of the sympathetic ANS: projects its axon to a peripheral ganglion - Cholinergic Receptors Postganglionic Neurons – CB in peripheral - Adrenergic Receptors ganglion its axon projects to an effector . To relate how drugs interact (influence) the receptors seen in the sympathetic ANS. Spinal cord Sympathetic Dorsal root Trunk Ventral root Rib Paravertebral Sympathetic ganglia trunk ganglion 3 cervical Sympathetic 11 trunk thoracic Ventral ramus 4 lumbar of spinal nerve 4 sacral 1 Gray ramus coccygeal communicans White ramus communicans Thoracic splanchnic nerves (a) Location of the sympathetic trunk Figure 14.5a Pathways with Synapses in Collateral Ganglia Most fibers from T 5 –L2 synapse in collateral ganglia They form thoracic, lumbar, and sacral splanchnic nerves Their ganglia include the celiac and the superior and inferior mesenteric Neurotransmitter Effects Two-neuron chain from CNS to effector organs Somatic nervous system ACh NE Unmyelinated Ganglion postganglionic axon All somatic motor neurons release acetylcholine (ACh) Lightly myelinated Epinephrine and preganglionic axons norepinephrine + ACh Effects are always stimulatory SYMPATHETIC Stimulatory or inhibitory, depending ANS Adrenal medulla Blood vessel on neuro- transmitter and Preganglionic fibers release ACh ACh ACh Smooth muscle receptors (e.g., in gut), on effector AUTONOMICNERVOUS SYSTEM organs Postganglionic fibers release norepinephrine or ACh at Lightly myelinated Unmyelinated glands, cardiac preganglionic axon muscle Ganglion postganglionic axon effectors PARASYMPATHETIC Effect is either stimulatory or inhibitory, depending on Acetylcholine (ACh) Norepinephrine (NE) type of receptors Figure 14.2 Neurotransmitters Cholinergic Receptors I. Cholinergic fibers release the neurotransmitter Two types of receptors bind ACh ACh 1. Nicotinic (stimulatory) All ANS preganglionic axons Found on: All ganglionic neurons both (sympath & para) All parasympathetic postganglionic axons Motor end plates of skeletal muscle cells II. Adrenergic fibers release the neurotransmitter Hormone-producing cells of the adrenal medulla NE 2. Muscarinic (inhibitory or excitatory)* Most sympathetic postganglionic axons Found on: All effector cells stimulated by postganglionic Exceptions: sympathetic postganglionic fibers secrete cholinergic fibers ACh at sweat glands and some blood vessels in skeletal * depends on target muscles organ Adrenergic Receptors Two types Alpha ( α) (subtypes α1, α2) - Excitatory Beta ( β) (subtypes β1, β2 , β3) Effects of NE depend on which subclass of receptor predominates on the target organ. β1 – increases heart activity β2 – relaxes smooth muscle of bronchioles Table 14.2 Effects of Drugs Over-the-counter drugs for colds, allergies, and nasal congestion Stimulate α-adrenergic receptors Beta-blockers Drugs that attach to β2 receptors to dilate lung bronchioles in asthmatics; other uses Table 14.2 Stimulus 1 Sensory receptor Dorsal root ganglion Visceral Reflexes in viscera 2 Visceral sensory Spinal cord Visceral reflex arcs have the same components as neuron somatic reflexes 3 Integration center • May be preganglionic Main difference: visceral reflex arc has two neurons in neuron (as shown) • May be a dorsal horn the motor pathway interneuron • May be within walls Visceral pain afferents travel along the same pathways of gastrointestinal tract Autonomic ganglion as somatic pain fibers, contributing to the 4 Efferent pathway phenomenon of referred pain (two-neuron chain) • Preganglionic neuron • Ganglionic neuron 5 Visceral effector Response Figure 14.7 HW for Week 4 Due in lab: Diseases & Disorders of the nervous system W.S. Labeling: pg 337 (spinal cord) pg. 378 (eye) Study Guide will be provided for in lab (Tuesday) Preview dissection of eye and eye related reflexes..