Ch 14 - Autonomic Nervous System PDF

BIOL243 – HUMAN ANATOMY & PHYSIOLOGY I Charles Smith, PhD CSCS HUMAN ANATOMY & PHYSIOLOGY Ch. 14 – Autonomic Nervous System AUTONOMIC NERVOUS SYSTEM Subconsciously makes adjustments to ensure optimal support for body activities Innervates smooth muscle, cardiac muscle, glands S...

BIOL243 – HUMAN ANATOMY & PHYSIOLOGY I Charles Smith, PhD CSCS HUMAN ANATOMY & PHYSIOLOGY Ch. 14 – Autonomic Nervous System AUTONOMIC NERVOUS SYSTEM Subconsciously makes adjustments to ensure optimal support for body activities Innervates smooth muscle, cardiac muscle, glands Shunts blood to needed areas, adjusts HR & BP, regulates digestive processes, etc. Central nervous system (CNS) Peripheral nervous system (PNS) Sensory (afferent) Motor (efferent) division division Somatic nervous Autonomic nervous system system (ANS) Sympathetic Parasympathetic division division AUTONOMIC V. SOMATIC NERVOUS SYSTEM Autonomic Somatic 2 Neuron Chain: Single axon extending to effector Preganglionic: cell body in CNS; axon extending to autonomic ganglion with cell body in CNS Postganglionic: axon extends to effector Innervates skeletal muscle organ Innervates smooth muscle, cardiac muscle, Only releases ACh & glandular tissue Always excitatory effects Release multiple neurotransmitters Preganglionic: ACh Postganglionic: either norepinephrine (sympathetic) OR acetylcholine (parasympathetic) Effects either excitatory or inhibitory AUTONOMIC NERVOUS DIVISIONS Parasympathetic (Rest & Sympathetic (Fight or Flight) Digest) Thoracolumbar fibers (thoracic & lumbar Craniosacral fibers (brain & sacral spinal cord origin) spinal cord origin) Short preganglionic, Long postganglionic fibers Long preganglionic, Short Ganglia located near spinal cord postganglionic fibers Ganglia located in or near effector organ Increases HR, BP, and respiration Increase blood, oxygen & nutrient delivery Decreases HR, BP, and respiration Decreases digestion Increases digestion Dilates eye pupils (mydriasis) Constricts pupils (miosis) Increase situational awareness Allows for better close-up vision AUTONOMIC RECEPTORS ACh gets released from cholinergic fibers while NE gets released from andrenergic fibers Effects depend on the receptor they bind to Cholinergic Receptors bind ACh Nicotinic receptors: always excitatory effects (i.e., skeletal muscle excitation) Muscarinic receptors: either excitatory or inhibitory Found for heart muscle, smooth muscle, & glands Effect depends on receptor type on organ i.e., ACh will reduce cardiac contraction to slow heart rate but will increase intestinal contraction to hasten digestion Andrenergic receptors bind E & NE Alpha (α): vasoconstrict, increase BP, close bladder, reduce digestion Beta (β): vasodilate, increase HR & heart contraction, bronchodilate, and increase fuel usage (metabolism) SYMPATHETIC- PARASYMPATHETIC INTERACTIONS By and large, the two seem to oppose each other Antagonistic S – raises HR, BP, Respiration; inhibits digestion & elimination P – lowers HR, BP, Respiration; promotes digestion & elimination Sometimes, however, they work together Cooperatively Example: Reproductive control of external genitalia S – stimulates ejaculation (male or AMAB) & reflexive vaginal contractions (female or AFAB) during intercourse P – stimulates vasodilation causing erection of penis or vaginal clitoris SYMPATHETIC DIVISION IS A LITTLE UNIQUE Both Sympathetic & Parasympathetic serve all organs Usually cause opposing effects, sometimes cooperative Sympathetic Division has some roles all by itself Return to homeostasis brought on by decreasing Sympathetic Drive rather than Parasympathetic action 1. Thermoregulation to Heat When body temp rises, sympathetic nerves will… Dilate cutaneous (skin) blood vessels – facilitate surface cooling Activate sweat glands 2. Renin Release from Kidneys Sympathetic division stimulates release of Renin to help raise blood pressure Renin-Angiotensin-Aldosterone mechanism (to be discussed in BIOL244) 3. Metabolic Effects Fighting or fleeing requires energy Metabolic rate of cells increases Blood glucose levels increase – increased breakdown of carb stores (glycogen) Increased fat burning for energy This is why pre-workouts & fat burners have caffeine and other stimulants DRUG INFLUENCES ON ANS Autonomic nervous function can be regulated/altered by drugs Anesthetics: used in surgery to allow patient intubation & prevent movement during procedure (hopefully) Aka Paralytics Nicotinic cholinergic receptor antagonist i.e., Succinylcholine or Vecuronium Scopolamine: muscarinic receptor antagonist preventing communication with brain centers for vomiting Helps prevent/abate nausea or vomiting post-op or from motion/sea-sickness More drugs in table on next slid AUTONOMIC NERVOUS SYSTEM SUMMARY ANS job is to subconsciously regulate the body’s internal functions to meet the necessary demands Whether that’s ramp things up for Fight or Flight (sympathetic)… …or bring you back down to Rest & Digest (parasympathetic) Sympathetic and Parasympathetic by and large oppose each other Help keep things balanced; maintain a dynamic homeostasis But can act cooperatively when necessary Sympathetic division has some unique roles that are not directly countered by the parasympathetic Wind back down simply by a decrease in sympathetic stimulation Different drugs can help to better regulate or change autonomic function to fit a specific need SAMPLE QUESTIONS 1. Name two differences between the Autonomic and Somatic nervous systems. 2. Which autonomic nervous fibers can release acetylcholine? 3. How do the sympathetic and parasympathetic divisions affect heart rate differently? 4. To what type of autonomic receptor does epinephrine & norepinephrine bind? 5. What drug binds to beta-andrenergic receptors to help treat asthma?  COPYRIGHT © Pearson Edited by Charles Smith, PhD CSCS 2024