2024 Autonomic Nervous System Notes

Autonomic Imbalance (Neurotransmission and Function of ANS) Year 2, Unit I, Problem 4 Academic year 2024/2025 Dr. Tarik AlShaibani 10/5/2017 1 General Structure of the Nervous System autonomic nervous system :...

Autonomic Imbalance (Neurotransmission and Function of ANS) Year 2, Unit I, Problem 4 Academic year 2024/2025 Dr. Tarik AlShaibani 10/5/2017 1 General Structure of the Nervous System autonomic nervous system : what happens without our consious The sensory division carries impulses toward the CNS from the body’s muscle : from brain to brain sensory receptors. efferent Somatic sensory fibers # exiting the · brain to Afferent transmit impulses from the brain going at the the muscles joints, skeletal muscles, and skin. Visceral sensory fibers transmit impulses from the visceral organs of the ventral body cavity. imprises from Somatic transmit - joints - Skeletal muscle - skin visceral transmits imprises from - visceral organs  The autonomic nervous system is an involuntary system that controls and modulates the functions primarily of visceral organs. The axons of the postganglionic neurons then travel to the periphery, where they synapse on visceral effector organs such as the heart, bronchioles, vascular smooth muscle, gastrointestinal tract, bladder, and genitalia. * ANS Helps to regulate arterial pressure, bladder emptying, sweating, body temperature. Also, it regulates the cardiovascular and respiratory systems, Loading… gastrointestinal tract, exocrine and some endocrine glands throughout the body. ANS is very rapid and intense in changing visceral function, for example, it takes 3-5 seconds to increase the heart rate by twofold and 10-15 seconds to double the arterial blood pressure. * ANS is controlled by centers located in the spinal cord, brain stem, the hypothalamus, limbic system and frontal lobes, which are concerned with arousal and behavioral responses to threat. - Autonomic IS an involuntary system Controls - & modulate functions of visceral organs axons travel to periphery and synapse on like heart GIT bladder and organs bronchioles, vascular smooth muscle ganglia. - , , , Autonomic nervous system regulate arterial pressure bladder emptying Sweating body temperature regulate cardiovascular and respiratory systems GIT , exocrine and some endocrine gland ANS IS rapid and intense functions very in changing visceral - 3-5 seconds to increase heart rate 10-15 seconds to double arterial blood pressure - ANS is controlled by centers located in , Spinal cord , brain Stem , hypothalamus , limbic system , and frontal lobes. I ↓ all are concerned with arousal and behavioral responses to threat  Sympathetic NS: rest and Parasympathetic digest Parasympathetic NS: (skr11) back) cranium sacrum (lower Thoraco-lumbar Outflow (T1 – L2) acetylcholine chemical is a Cranio-sacral Outflow cranial nerves sacral nerves Thorax - lumbar 12 cranial nerves I receptors recieving acetylcholine are called receptors cholinergic two types of cholinergic receptors 1. Nicotinic receptors cholinergic Muscurinic receptors 2. cholinergic X five categories M1-g1T M write nara 2 and complete the A3-eyes , rotate 3 and draw eyes M4- chS M5-chS fight or flight Sympathetic :noradrenaa B1 : rotate B heart Alpha : muscles around blood vessels contracting causing vaso constriction Alphan &thing e upt h Betaz : cause vasodilation nerve before ganglion nerve after ganglion Autonomic Efferent Pathways has Sweat gland cholinergic receptor in sympathetic, it's the only exception Loading… 3 T facial nerve a naso Pharngeal 10 vagus e It goes everywhere  Autonomic Efferent Pathways- Ctd Parasympatheti c Act Sympathetic ACh & NE 10/5/2017 6 General Characteristics of the Parasympathetic and Sympathetic Nervous Systems Widespread effect Usually causes specific localized responses General Concepts for Autonomic Function -Autonomic Tone Muscles cardiac muscles intestines Sympathetic and Parasympathetic tone , , are a little bit contracted. Autonomic motor neurons have a resting This basal tone allows for an increase or decrease in level of spontaneous activity even when there the activity of an autonomic nerve, allowing for are no stimuli. This determines the autonomic better control. tone. resting level : It is the basal (resting) level of activity of autonomic nerves. vasoconstriction quasoconstriction Sympathetic tone normally keeps most blood vessels partially constricted (50% vasoconstriction in arterioles), thus maintaining blood pressure. Parasympathetic tone: keeps 70-80 heart rate. provides background G.I. activity. maintains the resting heart rate at 70-80 beats/min. If the Vagus nerve was cut, the heart would beat at its own intrinsic rate of 100 beats/min. Parasympathetic node - reduces spontaneous. If there is a loss of tone, then BP could rapidly drop. discharge node rate of sinus it's withdrawal : increases it - Parasympathetic tone reduces the spontaneous discharge rate of the sinus node, whereas its withdrawal accelerates sinus node  General Concepts for Autonomic Function- Dual Innervation for example: reproductive system Dual innervations: Most organs have both sympathetic and parasympathetic innervation. These innervations operate reciprocally or synergistically to produce coordinated responses. ANS cooperation (synergism) is best seen in control of the external genitalia Parasympathetic fibers cause vasodilation and are responsible for erection of the penis and clitoris. Sympathetic fibers cause ejaculation of semen in males and reflex peristalsis in females. Parasympathetic : erection Sympathetic : ejaculation 10/5/2017 9 Autonomic motor neurons have a resting level of spontaneous activity even when there are no stimuli. This determines the autonomic tone, which is an important function of the ANS. By keeping a resting level of activity constant, an autonomic nerve can decrease or increase its activity, allowing for better control. Increasing or decreasing “tone” can change vessel diameter and thus increase or decrease arteriole resistance and blood flow. A decrease in the autonomic tone of smooth muscle in blood vessels will cause an increase in vessel diameter.  memorize this Actions of the ANS on Different Organs Sympathetic and parasympathetic divisions typically function in opposition to each other. The sympathetic division typically functions in actions requiring quick responses. Loading… The parasympathetic division functions with actions that do not require immediate reaction. For an analogy, one may think of the sympathetic division as the accelerator and the parasympathetic division as the brake. Higher CNS Centers that Control Autonomic Responses ANS activity is mediated by centers located in the spinal cord, brain stem, the hypothalamus, limbic system and frontal lobes. The efferent activity of the ANS is largely regulated by autonomic reflexes. In many of these reflexes, sensory information from visceral organs is transmitted to homeostatic control centers, in particular those located in the hypothalamus and brainstem. Subconscious reflex responses are returned directly back to the visceral organs to control their activities. Figure 61-6. Autonomic control areas in the brain stem and hypothalamus. 10/5/2017 12 Sympathetic Parasympathetic Increases decreases heartrate heartrate I sometimes they synergetic (gig50) can be - Ex : reproductive system Parasympathetic : erection Sympathetic : ejaculation The autonomic nervous system is regulated by integrated reflexes through the brainstem to the spinal cord and organs. Autonomic functions include control of respiration, cardiac regulation (the cardiac control center), vasomotor activity (the vasomotor center), and certain reflex actions such as coughing, sneezing, swallowing and vomiting. The hypothalamus, just above the brain stem, acts as an integrator for autonomic functions, receiving autonomic regulatory input from the limbic system. The medulla oblongata controls autonomic functions and connects the higher levels of the brain to the spinal cord. It is also responsible for regulating several basic functions of the autonomic nervous system, including respiration: chemoreceptors. Cardiac center: sympathetic system, parasympathetic system. Comparison of Somatic and Autonomic NS voluntary think muscles - involuntary involuntary 10/5/2017 14 ANS Cholinergic Receptors Nicotinic: found in autonomic ganglia at the synapses Muscarinic Important location Action between the preganglionic and post-ganglionic receptors neurons of both the sympathetic and parasympathetic nervous systems. M1 GIT Activating GIT, 1 Salivation M2 Heart 92 Bradycardia Muscarinic: M1, M2, M3, M4, and M5 are found on all effector cells that are stimulated by the M3 Smooth muscles, Bronchoconstriction postganglionic cholinergic neurons of either the sweat glands, , bladder parasympathetic nervous system (or the sympathetic Airways, bladder, contraction, miosis Eyes It system, as some postganglionic sympathetic nerves are cholinergic). M4-M5 CNS Decreased locomotion 10/5/2017 15 Adrenergic Receptors and Function epinephrine on alpha : vasoconstriction On beta : Vasodilation A: contraction B1 : Metabolic functions B2: relaxation of smooth muscle Cell surface glycoproteins that recognize and selectively bind the catecholamines, norepinephrine and epinephrine, - which are released from sympathetic nerve endings and the adrenal medulla. α or β receptors. Those two classes are further subdivided into α1 (α1A, α1B α1D), α2, β1, β2, and β3. The α receptors cause contraction of smooth muscle such as vascular smooth muscle, gastrointestinal and bladder sphincters and the radial muscle of the iris. The β1 receptors are involved in metabolic functions such as gluconeogenesis, lipolysis, renin secretion, and in all functions of the heart. The β2 receptors cause relaxation of smooth muscle in bronchioles, wall of the bladder, and wall of the gastrointestinal tract. Receptors Different Effect with Different Receptor L & A B B1 B2 B3 Al A2 A Epinephrine (adrenaline) reacts with both α- and β-adrenoreceptors, causing vasoconstriction and vasodilation, respectively. e 16 Function of the Adrenal Medulla Adrenal medulla: Sympathetic Adrenal medulla Considered to be large sympathetic ganglion. Receives preganglionic sympathetic cholinergic neurons which synapses with Chromaffin cells. Chromaffin cells are cells with granules or vesicles containing adrenaline or noradrenaline and they are the secretory cells of the adrenal medulla. When stimulated releases epinephrine (80%) and norepinephrine (20%) into the blood. Stimulation of cardiovascular function and metabolic rate. Involved in stress response and help our body to deal with stress. chromafin cell tumor ↑ Pheochromocytoma is a tumour that arises from chromaffin cells present in the adrenal medulla. Excessive secretion of catecholamines. snaring 10/5/2017 17  Stress Response - Mass sympathetic discharge: The sympathetic NS is usually activated during stress and excitement to elicit a “fight or flight” response. Causes increase in arterial pressure, heart rate and contractility, blood flow to muscles, blood glucose, metabolic rate, muscle strength, mental activity, and blood coagulation. Prepares the body for vigorous activity need to deal with a life- threatening situation. Fight or Flight Response Examples of Autonomic Reflexes Baroreceptor reflex : control of blood pressure Micturition reflex : Emptying bladder hair stands Gastrointestinal reflexes 10/5/2017 18. THE END THANK YOU