Lesson 2 Chapter 17 – Autonomic Nervous System

Lesson 2 Chapter 17 – Autonomic Nervous System 1 Unit 6 Study Guide Overview of the Nervous System Comprised of the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). - The Central Nervous System comprises of the brain and the spinal cord. The Peripheral Nervous System comprises of the autonomic nervous system and the somatic nervous system. The CNS handles involuntary information while the PNS handles voluntary information. CNS: - Integrates, processes, and coordinates. Intelligence, memory, learning, and emotion. PNS: - Neural tissue outside the CNS o Provides sensory info to the CNS o Carries motor commands to peripheral tissues o The PNS is subdivided into two divisions: 1) Afferent division: brings sensory information to the CNS. 2) Efferent division: carries motor commands to muscles and glands. Divided into two divisons: a. Somatic Nervous System (SNS) b. Autonomic Nervous System (ANS) The somatic nervous system deals with voluntary muscles; the autonomic nervous system deals with automatic functions. For instance, you're driving in your car texting on your phone. You look up and there's a car stopped right in front of you and you're about to rear-end it. You slam on your brakes. Immediately, your heart starts pounding, you breathe faster, and you may even begin to sweat. Did you have to consciously tell your body to do all those things? Nope- that's autonomic. That's actually the sympathetic division of the autonomic nervous system. Sympathetic speeds everything up. It's called the "Fight or Flight." The other part of the autonomic nervous system is the PARAsympathetic, which does the opposite- it kinda slows everything down. It's called "Rest and Digest." Somatic is everything you purposely do – chewing, kicking, waving, etc. Lesson 2 Chapter 17 – Autonomic Nervous System 2 Lesson 2 Chapter 17 – Autonomic Nervous System 3 Somatic Nervous System - Consciously perceived sensations Excitation of skeletal muscles One Motor neuron connects CNS to organ Autonomic Nervous System - Unconsciously perceived visceral (any of the body’s organs located in the chest or abdomen) sensations Involuntary inhibition or excitation of smooth muscle, cardiac muscle or glandular secretion. Two Motor neurons needed to connect CNS to organ (preganglionic and postganglionic neurons) ANS: Ganglion (Glial cells) Preganglionic neuron at the anterior grey horn. - Cell body in the brain or spinal cord - Axon is myelinated type B fiber that extends to autonomic ganglion (faster impulse) Postganglionic neuron an autonomic ganglion to an effector (smooth/cardiac muscle, glands) Lesson 2 Chapter 17 – Autonomic Nervous System - Cell body lies outside the CNS in an autonomic ganglion - Axon is unmyelinated type C fiber that terminates in a visceral effector. (slower impulse) Divisions of the ANS 2 Major divisions: Parasympathetic Nervous System and Sympathetic Nervous System Both can be distinguished by: origin sites, different lengths in fibers, and location of their ganglion. o Sympathetic origin: Thoracic and lumbar region o Parasympathetic origin: Four (4, 7, 9, 10) cranial nerves and sacrum (2, 3 ,4) Neurotransmitters released: ACh = acetylcholine for sympathetic. Norepinephrine = epinephrine for parasympathetic (released from adrenal medulla) Sympathetic: short preganglionic fibers Parasympathetic: long preganglionic fibers, very short postganglionic. (Preganglionic fiber synapse with only 4-5 postganglionic neuron – localized response) 4 Lesson 2 Chapter 17 – Autonomic Nervous System 5 Parasympathetic Origin: Cranial Nerves: Sacral: Cranial Nerve III (Oculomotor) - S2 to S4 - Ciliary ganglion - Pelvic splanchnic nerve Cranial Nerve VII (Facial) - Pytergopalantine ganglion Submandibular ganglion Cranial Nerve IX (Glossopharyngeal) - Otic ganglion Cranial Nerve X (Vagus) - Carries 75% of all preganglionic fibers, travels down the neck Lesson 2 Chapter 17 – Autonomic Nervous System 6 Most body organs receive dual innervation. Innervation of both sympathetic & parasympathetic (with some exceptions) Hypothalamus regulates balance (tone) between sympathetic and parasympathetic activity levels. Some organs have only sympathetic innervation. - Sweat glands - Adrenal medulla - Arrector pili muscles (goosebumps) - Many blood vessels Autonomic Reflex Arc 1) 2) 3) 4) 5) Receptor Sensory neuron (afferent) Integrating center (hypothalamus) Motor neuron (efferent) [2 sets: preganglionic and postganglionic] Effector (smooth muscle, cardiac muscle, and glands)