Transcript Autonomic
Chapter 33 Regulation of the Visceral Function by the Nervous System I Autonomic Nervous System 1. Basic of the Anatomy Autonomic Nervous System Including parasympathetic, sympathetic, and enteric divisions. Coordinates cardiovascular, respiratory, digestive, excretory and reproductive systems. The enteric system is essentially an independent nervous system responsible for regulation of digestive functions. Somatic and Autonomic Nervous System Somatic and Autonomic Nervous System Somatic Skeletal muscle Conscious and unconscious movement Skeletal muscle contracts One synapse Acetylcholine Autonomic Smooth and cardiac muscle and glands Unconscious regulation Target tissues stimulated or inhibited Two synapses Acetycholine by preganglionic neurons and ACh or norepinephrine by postganglionic neurons 侧副神经节 Sympathetic Division Preganglionic cell bodies in lateral horns of spinal cord T1-L2 Parasympathetic Division Preganglionic axons innervated Preganglionic cell bodies in nuclei of brainstem or lateral parts of spinal cord （S2-S4） – Preganglionic axons from brain pass to ganglia through cranial nerves – Preganglionic axons from sacral region pass through pelvic nerves to ganglia pass to ganglia within wall of or near organ Parasympathetic and sympathetic nerve distribution 2. Neurotransmitters and Neuroreceptors Acetylcholine and Norepinephrine All preganglionic neurons are cholinergic Parasympathetic post ganglionic neurons are cholinergic Sympathetic post ganglionic neurons are adrenergic except – Sympathetics innervating sweat glands, blood vessels in skeletal muscle, and piloerection muscles are cholinergic Neurotransmitters SOMATIC NERVOUS SYSTEM AUTONOMIC NERVOUS SYSTEM Sympathetic ACh ACh ACh Parasympathetic Ad. M. ACh ACh Striated muscle NE Heart Sm. mus. Glands ACh Sweat glands ACh Heart Sm. mus. Glands E, NE Acetylcholine Nicotinic receptors – Nm (muscular-type or N2): skeletal muscle – Nn (neuron-type, or N1): autonomic ganglia, CNS Muscarinic receptors – Postganglionic parasympathetic and a few sympathetic sites, CNS – Receptor subtypes: M1-5 Catecholamines Norepinephrine – Postganglionic sympathetic, CNS, adrenal medulla – Receptors: a1, a2, b1 Epinephrine – Adrenal medulla, CNS – Receptors: a1, a2, b1 , b2 Dopamine – Autonomic ganglia, CNS – Receptors: D(1-5), a1, b1 Location of ANS Receptors 3 Function of the Sympathetic and Parasympathetic Nerve Properties of the ANS Tonic discharge Double innervation – Most blood vessels are innervated only by sympathetic nerves. – Parasympathetic activity dominates the heart and GI tract. Dependent on the states of the target organ Different physiological significance – Sympathetic nerve: fight and flight reaction – Parasympathetic nerve: Wind down, relaxation, digestion SNS Sympathetic nervous system prototypically “fight” or “flight”. Associated with increased energy expenditure, cardiopulmonary adjustments for intense activity, blood flow adjustments for maximum energy expenditure. SNS - Fight & Flight Reaction You’re walking alone at night and all the sudden you hear an unfamiliar noise near by… In a matter of seconds, your heart rate increases dramatically, blood vessels in your skeletal muscles dilate, blood vessels in the visceral muscles constrict, digestion is ceased, your liver ramps up glucose release, your pupils dilate, salivary production decreases, sweat increases. Parasympathetic Nervous System If that noise turns out to be the result of wind, the body is returned to “pre-noise” state. This is the job of the parasympathetic nervous system. Autonomic Nervous System • Parasympathicus • Sympathicus • Wind down, relaxation, digestion • Dominated by Acetylcholine • Fight & Flight Reaction • Dominated by Noradrenaline (Adrenaline) • Fear, exercise, rage II. Central Regulation of Visceral Function 1. Spinal cord bladder and rectum reflex (micturition and defecation) the baroreceptor reflex sweating of the skin 2. Medulla oblongata Vital (respiratory and cardiovascular) center: Other autonomic reflexes: Swallow, cough, sneeze, gag, and vomit. 3. Hypothalamus Tu :19.17 Hypothalamic Functions Food Intake Water Balance Sleep/wake cycle Emotions and behavior Circadian Endocrine Functions Body Temperature Autonomic Nervous System Food Intake Ventromedial and Paraventricular Nuclei are satiety centers – Lesion causes obesity – Through disrupting satiety input to the periventricular nucleus Lateral HT is feeding center – Stimulation cause food and water intake – Lesion causes starvation behavior – Through damage the medial forebrain bundle, leading to neglect syndrome – no motivation to eat Water Balance Thirst center in the hypothalamus (supraotic nucleus) is stimulated by: – Cellular dehydration – Decreased salivary production – Increased blood osmotic pressure – Decreased blood volume Thirst center response – Release vasopressin – Cause sensation of thirst Sleep/Wake Cycle suprachiasmatic nuc is biological clock preoptic nuc can initiate sleep lateral hypothalamus can change cortical arousal post hypothalamus lesion can cause coma or impaired arousal Emotions and Behavior Ventromedial lesions can cause viciousness/rage Posterior HT stimulates sympathetic functions Anterior HT stimulates parasympathetic functions Mamillary nuclei recent memory Circadian Almost all land animals coordinate their behavior according to circadian rhythms Suprachiasmatic Nuclei (SCN) Circadian Rhythms of Physiological Functions Endocrine Function Regulation of Adenohypophysis Secretion of Hormones (Vasopressin and Oxytocin) Functions of the Hypothalamus Food intake Water balance Sleep/wake cycle Emotions and behavior Circadian Endocrine Function Body temperature Autonomic Nervous System 4 Influence of Brain on Autonomic Functions III Function of Sympathetic and Parasympathetic nerve on the target organs Physiology (Table 5-1) Eye Effector Radial muscle Sphinctor Ciliary muscle Cornea Iris Lens Ciliary muscle Sympathetic Parasympathetic Contraction — (mydriasis, a1) — Contraction (miosis) Slight relaxa- Contraction (near tion (b2) vision) Heart Atria SA node AV node Ventricles Effector SA node Atria AV node Ventricles Sympathetic Tachycardia (b1,b2) contractility and conduction (b1,b2) conduction and automaticity (b1,b2) contractility, conduction, and automaticity (b1,b2,a1) Parasympathetic Bradycardia contractility, conduction (usually) conduction — Blood vessels Effector Skin and mucosa Skeletal muscle Salivary glands Erectile tissue Sympathetic Constriction (a1,a2) Constriction (a), dilation (b2) Constriction (a1,a2) Constriction (a) Parasympathetic Dilation (?) — Dilation Dilation Lungs and salivary glands Effector Bronchial sm. musc. Bronchial glands Salivary glands Sympathetic Parasympathetic Relaxation (b2) Constriction (a1),(b2), secretion Viscous, amylase secretion (a1,b1,b2) secretion Profuse watery secretion Gastrointestinal tract and liver Effector Smooth muscle Sympathetic Parasympathetic motility and motility and tone tone (a1,a2,b1,b2) Sphincters Contraction Relaxation (a1) Secretions secretion (a2) secretion Liver Glycogenolysis, Glycogen gluconeogene- synthesis sis (a1,b2)