Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download 13 Central regulation of autonomic functions
Transcript
Central regulation of autonomic functions Levels of ANS Control Figure 14.9 4 Influence of Brain on Autonomic Functions Central Regulation of Visceral Function 1. Spinal cord bladder and rectum reflex (micturition and defecation) sexual reflex the baroreceptor reflex sweating of the skin Reflex control of micturition Bladder filling facilitated by tonic neural activity: • sympathetics – inhibits bladder contraction • sacral somatic motor nerves – contracts external sphincter Bladder filling activates Mechanoreceptors Voiding (micturition): threshold reached • sympathetic and somatic motor neurons inhibited • parasympathetic outflow to detrusor m. activated • bladder smooth muscle contracts Neural Control of Defecation. Filling of the rectum with feces stimulates stretch receptors, which transmit impulses to the spinal cord. A spinal reflex stimulates contractions of the rectum and relaxation of the internal anal sphincter. Defecation normally does not occur unless voluntary impulses relax the external anal sphincter. 2. Medulla oblongata Vital (respiratory and cardiovascular) center: Other autonomic reflexes: Swallow, cough, sneeze, gag, and vomit. 3. Hypothalamus Tu :19.17 Hypothalamic Control Centers of the hypothalamus control: Heart activity and blood pressure Body temperature, water balance, and endocrine activity Emotional stages (rage, pleasure) and biological drives (hunger, thirst, sex) Reactions to fear and the “fight-or-flight” system Hypothalamic Functions 2). Food intake: ventromedial and paraventricular nuclei are satiety centers, lesion causes obesity; lateral HT (feeding center) stimulates food and water intake Hypothalamus Functions 3) Water balance ADH (vasopressin) Osmotic pressure in hypothalamus – Thirst - Drink 4) Sleep/wake cycle: suprachiasmatic nuc is biological clock; preoptic nuc. can initiate sleep; lat HT can change cortical arousal; post HT lesion can cause coma or impaired arousal Hypothalamus Functions 5). Emotions and behavior: ventromedial lesions can cause viciousness/rage Posterior HT stimulates sympathetic functions Anterior HT stimulates parasympathetic functions Mamillary nuclei: recent memory Circadian rhythms of physiological functions. Central control of the Autonomic NS Amygdala: main limbic region for emotions -Stimulates sympathetic activity, especially previously learned fearrelated behavior -Can be voluntary when decide to recall frightful experience - cerebral cortex acts through amygdala -Some people can regulate some autonomic activities by gaining extraordinary control over their emotions Hypothalamus: main integration center Reticular formation: most direct influence over autonomic function Visceral Reflexes The visceral sensory neurons are the first link in the autonomic reflexes These neurons send information concerning chemical changes, stretch, and irritation of the viscera Visceral Reflexes Visceral reflex arcs have essentially the same components as somatic reflex arcs Receptor Sensory neuron Integration center Motor neuron Effector Visceral Reflexes Visceral reflex arcs differ in that they have a twoneuron chain Autonomic Reflexes Visceral Reflexes Additional cutaneous areas to which visceral pain is referred Autonomic reflexes a) viscero-visceral b) viscero-dermal (viscero-somatic) c) dermato-visceral (somato-visceral) Cornea Iris Lens Eye Effector Radial muscle Sphinctor Ciliary muscle Ciliary muscle Sympathetic Parasympathetic Contraction — (mydriasis, 1) — Contraction (miosis) Slight relaxa- Contraction (near tion (2) vision) Effector SA node Atria AV node Ventricles Sympathetic Tachycardia (1,2) contractility and conduction (1,2) conduction and automaticity (1,2) contractility, conduction, and automaticity (1,2,1) Parasympathetic Bradycardia contractility, conduction (usually) conduction — Blood vessels Effector Skin and mucosa Skeletal muscle Salivary glands Erectile tissue Sympathetic Constriction (1,2) Constriction (), dilation (2) Constriction (1,2) Constriction () Parasympathetic Dilation (?) — Dilation Dilation Lungs and salivary glands Effector Bronchial sm. musc. Bronchial glands Salivary glands Sympathetic Parasympathetic Relaxation (2) Constriction (1),(2), secretion Viscous, amylase secretion (1,1,2) secretion Profuse watery secretion Gastrointestinal tract and liver Effector Smooth muscle Sympathetic Parasympathetic motility and motility and tone tone (1,2,1,2) Sphincters Contraction Relaxation (1) Secretions secretion (2) secretion Liver Glycogenolysis, Glycogen gluconeogene- synthesis sis (1,2) • • afferent input integrated in CNS centers impacts autonomic efferent outflow EXAMPLE: • blood pressure falls • sinus nerve activity falls • sympathetic outflow increases to the: vasculature – vasoconstriction heart – increased cardiac output adrenal medulla – increased epinephrine release Reflex control of GI function • smell, taste of food and/or foods in the stomach LOCATION OF SENSORY STRUCTURES? • central integration • reflex parasympathetic efferent stimulation which leads to: increased motor activity (stomach, gallbladder and intestine) increased secretory activity (stomach and pancreas) Fight or flight response This is a coordinated, massive increase in sympathetic outflow to all target organs in response to fear, stress, or exercise. Parasympathetic outflow ceases. The coordinated physiologic response is a survival mechanism which includes: • • • • • • Increased heart rate, cardiac output, and blood pressure Contraction of the spleen to mobilize blood cells Bronchial dilation Decreased GI activity Liberation of glucose into the bloodstream Inhibition of insulin secretion However, under normal non-stressful situations, autonomic efferent outflow is more discrete. Autonomic reflexes play an important role in regulating physiologic function.
