Unit 10 Autonomic Nervous System (ANS)

Objectives: Comparison of Somatic & Autonomic Nervous Systems Structure of the Autonomic Nervous System Anatomical Components

Functions of the Somatic and Autonomic Nervous Systems http://study.com/academy/lesson/functions-of-the-somatic-autonomic-nervous-systems.html

Comparison: SomaticNS vs AutonomicNS SNS Controls skeletal muscle Conscious, voluntary control Motor pathway: one neuron from CNS to effector Does include sensory neurons (from skin, skeletal muscles, and special sense organs) All release the neurotransmitter ACh ANS Controls viscera: smooth and cardiac muscle, and glands Unconscious, involuntary Motor pathway: series of two neurons from CNS to effector Does include sensory neurons (monitors viscera) Two divisions: sympathetic, parasympathetic Release either ACh or NE

Somatic Nervous System Copyright 2010, John Wiley & Sons, Inc.

Introduction to the ANS Somatic nervous system (SNS) + ANS  peripheral nervous system (PNS) ANS Is regulated by hypothalamus, brainstem The ANS supplies nerves to viscera Smooth muscle (stomach, blood vessels) Cardiac muscle (heart) Glands (sweat and digestive glands)

ANS Motor Pathways Autonomic motor pathway includes two motor neurons CNS  (Autonomic ganglion) Preganglionic  Postganglionic neuron  to effector

Autonomic Nerve Fibers 11-61 Copyright 2010, John Wiley & Sons, Inc.

Autonomic Nervous System Two Divisions Sympathetic – prepares body for fight or flight situations Parasympathetic – prepares body for resting and digesting activities

Divisions of the ANS Sympathetic (S) + parasympathetic (P) Most viscera supplied with nerves of both S and P divisions: dual innervation S and P have opposite (antagonistic) effects Heart rate: S stimulates, P inhibits Digestive organs: S inhibit, P stimulate Some viscera receive only S (not P) nerves: Sweat glands, many blood vessels, hair muscles

Control of Autonomic Activity Largely CNS Medulla oblongata cardiac, vasomotor and respiratory activities Hypothalamus regulates balance between sympathetic and parasympathetic activity visceral functions Limbic system & cerebral cortex emotional responses https://www.youtube.com/watch?v=qqU-VjqjczE 11-70

ANS Motor Pathways Copyright 2010, John Wiley & Sons, Inc.

Objectives: Organization of the Sympathetic Division Organization of the Parasympathetic Division

Sympathetic (S) Preganglionic Cell bodies located in lateral gray of spinal cord segments T1-T12 + L1-L2 called “thoracolumbar” Axons pass through ventral roots of spinal nerves May branch many times May ascend or descend (from cervical to sacral) Can synapse with 20 or more postganglionic cell bodies Results: widespread effects (viscera respond with one another)

Sympathetic Division 11-62 Copyright 2010, John Wiley & Sons, Inc.

Sympathetic (S) Postganglionic Cell bodies located “Trunk ganglia” 2 long chains lateral to vertebrae “Prevertebral ganglia” Anterior to 3 large abdominal arteries

“Trunk ganglia” From cervical to sacral regions  widespread effects Many axons pass back into spinal nerves to reach skin sweat glands, hair muscles, blood vessels

“Prevertebral ganglia” Named celiac, superior and inferior mesenteric ganglia Supply abdominal viscera: stomach, intestine, kidneys, liver, spleen Axons pass from ganglia to viscera in S nerves

Sympathetic Division 11-63 Copyright 2010, John Wiley & Sons, Inc.

Sympathetic Division 11-64 Copyright 2010, John Wiley & Sons, Inc.

Parasympathetic (P) Preganglionic Cell bodies located in brainstem + in spinal cord segments S2-S4 “Craniosacral”

Parasympathetic Preganglionic Axons in cranial nerves III, VII, IX and X and in pelvic nerves from S2-S4 Vagus nerves (cranial nerves X) carry 80% of all P nerve impulses. Vagus nerves carry both motor and sensory neurons to/from viscera within the thorax and most of the abdominal cavity. Axons do not branch or pass though S trunk ganglia but pass directly almost to viscera

Parasympathetic Division 11-66 Copyright 2010, John Wiley & Sons, Inc.

Parasympathetic (P) Postganglionic Cell bodies lie in terminal ganglia Located within or near the innervated organ cause precise, localized (not widespread) effects S nerves supply all viscera but P nerves do not reach some sweat glands, arrector pili muscles, kidneys, spleen, adrenal medullae, and the walls of most blood vessels. Axons pass from ganglia to viscera in P nerves

Parasympathetic (P) Division Copyright 2010, John Wiley & Sons, Inc.

Objectives: Functions of the Autonomic Nervous System ANS Neurotransmitters Activities of the ANS Sympathetic Activities Parasympathetic Activities

ANS Neurotransmitters: Comparison Acetylcholine (ACh) More common Released by: All S and P preganglionic axons All P postganglionic axons Some S postganglionic axons (to sweat glands) Destroyed by enzyme ACh-ase Short-lived response Norepinephrine (NE) Less common Released by: Almost all S postganglionic axons Longer lasting effects Enhanced by epinephrine + NE from adrenal medullae

Sympathetic Effects Fight-or-flight activities Increase heart rate and contraction, and blood pressure (BP) Dilate pupils Dilate airways Dilate vessels to skeletal muscles, heart, liver and adipose tissue Constrict blood vessels to nonessential organs: skin, GI tract, kidneys Mobilize nutrients for energy: glucose and fats http://study.com/academy/lesson/fight-or-flight-response.html

Parasympathetic Effects Rest-and-digest activities SLUDD Salivation Lacrimation Urination Digestion Defecation Decrease Heart rate, Airway diameter, Pupil diameter

Aging and Autonomic Nervous System http://study.com/academy/lesson/how-age-affects-our-autonomic-nervous-system-changes-examples.html