Chapter 11 Efferent Division

Chapter 11 Efferent Division - Efferent Peripheral NS: The...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Efferent Peripheral NS: The Autonomic & Somatic Motor Divisions Divisions Running Problem: Smoking Review (again) (again) Homeostasis and the Homeostasis Autonomic Division Autonomic s BP, HR, Resp., H2O balance, Temp. . . balance, s Mostly dual reciprocal innervation s s i.e., agonist/antagonist or excitatory/inhibitory Sympathetic: s s s AKA Thoracolumbar flight-or-fight Parasympathetic: s AKA Craniosacral s rest and digest Autonomic Targets Autonomic s Smooth Muscle s Cardiac Muscle s Exocrine Glands s Some Endocrine glands s Lymphoid Tissue s Adipose Two Efferent Neurons in Series Neurons Autonomic pathway: Preganglionic neuron cell body in CNS Synapse in autonomic ganglion outside CNS (often Synapse divergence!) divergence!) Postganglionic neurons target cells target N1 N2 = Thoracolumbar division (T1 to L2) Preganglionic neurons (N1)from thoracolumbar region of spinal cord Pre and paravertebral ganglia Long postganglionic neurins (N2) secrete NE onto adrenergic receptors = Craniosacral Division Long preganglionic axons from brain & S2- S4 Intramural ganglia Postganglionic (nonmyelinated) neurons secrete ACh onto cholinergic muscarinic receptors Most Common Autonomic NTs: NTs: s Acetylcholine (ACh) ACh neurons & ACh receptors are called ACh cholinergic (nicotinic or muscarinic). Located cholinergic at autonomic preganglionic & paraat sympathetic postganglionic synapses sympathetic s Norepinephrine (NE) NE neurons & receptors are called (nor) adrenergic NE (α and β ). Located at sympathetic postganglionic synapses postganglionic Fig 11-7 NTs of Autonomic NS NTs Compare to Fig 11-7 N1 N2 N1 N2 α and β Neuroeffector Junction Neuroeffector = Synapse between Synapse postganglionic cell and target postganglionic s Most are different from model Most synapse (compare to Fig 8-20, p. 270) p. s ANS synapse: axon has ANS varicosities containing neurotransmitter neurotransmitter s May supply many cells, May resulting in less specific communication communication s Synthesis of NT is in the Synthesis varicosity varicosity Fig 11-8 Summary: Pre- & Postganglionic Summary: Parasympathetic Neurons Release ACh Parasympathetic N1 N2 nicotinic muscarinic Receptors Two Types of Cholinergic Receptors: Nicotinic and Muscarinic Receptors: 1) Nicotinic cholinergic receptor 2. Nicotine = agonist In autonomic ganglia & somatic NS 3. Directly opens a Na+ & K+ channel: ⇒ ? 4. Curare = antagonist 1. 2) Muscarinic 2) cholinergic receptor cholinergic s Muscarine = agonist Muscarine Amanita muscarina s Found in neuro-effector junctions of Found parasympathetic branch parasympathetic s G-protein coupled mechanisms s Atropine = antagonist N1 N2 Muscarinic ACh are G-protein Mediated Receptor Mechanism of Sweat Glands: Glands Also some 2nd messenger mechanisms Adrenergic Receptors Receptors s Found in neuroeffector junctions of Found sympathetic branch sympathetic s nd G protein linked, with various 2nd mess. Mech mess. s NT is NE s α- and β- Receptors NE Action Sympathetic Receptors Sympathetic α Receptors: •NT is NE •(most common) ⇒ Excitation [Ca2+] In↑ ⇒ muscle contraction or secretion by exocytosis. ∀⇒ Inhibition of GI tract and pancreas β − Receptors Clinically more important Clinically s β ⇒ Excitation heart ([E] = [NE]) heart 1 s “β - blockers” = Antagonists (e.g.: Propranolol) (e.g.: s β 2 usually inhibitory: smooth muscle relaxation of inhibitory smooth some blood vessels and bronchioles ([E] > [NE]) bronchioles ([E] s β3 s “β -blockers” = Antagonists (e.g.: Propranolol) (e.g.: Adipose; [NE]>[E] Adipose; Termination of NT Activity Activity Fig 8-22 s ACh: s s ACh esterase Catecholamine Catecholamine reuptake reuptake ¥ repackaging ¥ degradation (MAO) ¥ Blocked by cocaine Fig 11-9 Somatic Motor Division Somatic s Pathway consists of single Pathway neuron from CNS to target neuron s Neuromuscular junction: nicotinic Neuromuscular cholinergic receptors cholinergic s Similar to synapse; post – Similar synaptic membrant called Motor End Plate End s Recall Motor Unit s Always excitatory ⇒ muscle Always contracts contracts s All Ach mediated s Degraded by Ach esterase Fig 11-13 Myasthenia gravis MG: Antibodies block, alter, or destroy the receptors for acetylcholine at the neuromuscular junction Direct (Ant)agonist = mimic or block the NT receptor receptor (Ant)agonist = mimic or block secretion, (Ant)agonist reuptake or degradation of NT reuptake Direct Antagonists Antagonists s Atropine → muscarinic s Curare → nicotinic Curare s Propranolol → β1 and β2 Propranolol s Metoprolol → β1 Metoprolol Strychnos Toxifera ( Curare) from Koehler's MedicinalPlants 1887 Indirect (Ant)agonists Indirect s Botulinum toxin s s Parathion, malathion s s organophosphate insecticides → organophosphate inhibit AChE (anticholinesterases) inhibit Cocaine s s → inhibits ACh release inhibits → prevents NE reuptake prevents Amphetamines s → stimulates NE release stimulates Summary of Efferent NS Summary ...
View Full Document

Ask a homework question - tutors are online