Chapter 18 Autonomic Nervous System PDF

Chapter 18 Autonomic Nervous System By: Dr. R. Knudsen Copyright © McGraw-Hill Education. Permission required for reproduction or display. 1  Outline Comparison of the Somatic and Autonomic Nervous Systems Divisions of the Autonomic Nerv...

Chapter 18 Autonomic Nervous System By: Dr. R. Knudsen Copyright © McGraw-Hill Education. Permission required for reproduction or display. 1  Outline Comparison of the Somatic and Autonomic Nervous Systems Divisions of the Autonomic Nervous System Parasympathetic Division Sympathetic Division CNS Control of Autonomic Function 2  Comparison of Somatic and Autonomic Nervous Systems The somatic nervous system (SNS) includes processes that are perceived (sensory) or controlled consciously “skeletal muscle” The autonomic nervous system (ANS) includes processes regulated automatically conscious level = Subconscious 3  Comparison of Somatic and Autonomic Motor Nervous Systems Figure 18.1 4  Comparison of Somatic and Autonomic Nervous Systems In the SNS, somatic motor neurons innervate skeletal muscle fibers, causing conscious voluntary movement ANS motor neurons innervate smooth muscle fibers, cardiac muscle fibers, or glands ANS motor neurons can either excite or inhibit cells in the viscera 5 Motor Neurons of the Somatic VS Autonomic Nervous Systems In the SNS, a single lower motor neuron axon extends uninterrupted from the spinal cord to one or more muscle fibers In the ANS, a two-neuron chain innervates muscles and glands – Preganglionic and ganglionic neurons 6  Lower Motor Neurons of the Autonomic Nervous System Figure 18.2 7 Motor Neurons of the Somatic VS Autonomic Nervous Systems The first neuron in the ANS pathway is the preganglionic neuron, and its cell body is in the brain or spinal cord A preganglionic axon extends to the second cell body housed within an autonomic ganglion in the peripheral nervous system The second neuron in the pathway is called a postganglionic neuron A postganglionic axon extends from its cell body to effector (target) cells 8 Motor Neurons of the Somatic VS Autonomic Nervous Systems A two-neuron pathway allows for greater communication and control due to: – Neuronal convergence: Axons from numerous preganglionic cells synapse on a single ganglionic cell – Neuronal divergence: Axons from one preganglionic cell synapse on numerous ganglionic cells 9  Comparison of Somatic and Autonomic Motor Nervous Systems 10  Divisions of the Autonomic Nervous System Parasympathetic division: Conservation of energy and replenishment of nutrient stores (“rest- and-digest”); maintains homeostasis Sympathetic division: Preparation of body for emergencies (“fight-or-flight”); increased alertness and metabolic activity 11  Anatomic Differences Between Parasympathetic and Sympathetic Neurons Figure 18.4 12 Comparison of Parasympathetic and Sympathetic Divisions 13  Parasympathetic Division Also called craniosacral division because preganglionic neurons are housed within nuclei in the brainstem and sacrum Synapse between “pre and Post” is found in either terminal ganglia close to the target organ, or intramural ganglia in the wall of the target organ 14  Overview of Parasympathetic Pathways Figure 18.5 15  Parasympathetic Division Outflow – You are NOT responsible for testing purposes 16  Sympathetic Division Also termed thoracolumbar division because preganglionic neuron cell bodies are housed between first thoracic (T1) and second lumbar (L2) spinal segments 17 Organizational Anatomy of the Sympathetic Division More complex than the parasympathetic division Preganglionic neuron cell bodies are also housed in the lateral horn Preganglionic axons travel with somatic motor neuron axons to exit the spinal cord and enter the anterior roots Then synapse either in synaptic chain or a ganglion close to vertebral column 18  Overview of Sympathetic Pathways Figure 18.6 19  White and Gray Rami Branch off spinal trunk anteriorly Carries sympathetic ANS motor nerve/Neuron Leads to sympathetic chain of ganglia 20  Types of Sympathetic Pathways Figure 18.8a 21  Types of Sympathetic Pathways Figure 18.8b 22  Types of Sympathetic Pathways Figure 18.8c 23  Types of Sympathetic Pathways Figure 18.8d 24  Sympathetic Pathways The sympatho-adrenal medulla pathway involves the adrenal medulla – This is the internal region (medulla) of adrenal gland that releases hormones within the bloodstream to help promote fight-or-flight response – The hormones are epinephrine and norepinephrine 25  Autonomic Plexuses Figure 18.9 26  Overview of ANS Neurotransmitters All preganglionic axons release acetylcholine (ACh), which has an excitatory effect on the ganglionic cell All postganglionic parasympathetic axons (and a few postganglionic sympathetic axons) release ACh on the effector Depending on the receptor, ACh from parasympathetic axons may have either an excitatory or inhibitory effect 27  Overview of ANS Neurotransmitters ACh released from sympathetic axons is excitatory only Sweat glands, blood vessels in skeletal muscle Most postganglionic sympathetic axons release norepinephrine on the effector Depending on the receptor, norepinephrine has an excitatory or an inhibitory effect 28  Comparison of Neurotransmitters in the Autonomic Nervous System Figure 18.10 29  CNS Control of Autonomic Function Autonomic function is influenced by the: – Cerebrum – Hypothalamus – Brainstem – Sinal cord 30  Control of Autonomic Functions by Higher Brain Centers Figure 18.12 31