Study Guide 2

Study Guide 2 - Introduction to ANS Homeostasis maintenance...

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Introduction to ANS Homeostasis: maintenance of the internal environment: focus on efferent (motor) functions ANS works closely with the endocrine system to maintain homeostasis Sensory information from somato-sensory and visceral receptors goes to centers in hypothalamus, medulla, and pons. These centers are important for temperature, blood pressure, and water regulation Spinal Reflexes include urination, defecation and penile erection; bodily functions that can be influenced by descending pathways that do not require input from brain. Afferent: carrying information towards to CNS from periphery. The book pretends that the autonomic nervous system is primarily efferent: this is wrong. There has to be a sensory component of autonomic nervous system. It needs input in order to make appropriate actions. 2 Types of Afferents. 1. Somatosensory : touch, pain, pressure. 2. Visceral Afferents : internal afferents from head and neck region; especially from organs in the thoracic and abdominal body cavities: this is essential for autonomic system: sesnsing blood pressure or pH: Pressure in small arterioles that surround the nephrons. 3 Division: Sympathetic, Parasympathetic, and Enteric (doesn’t fit into other two). Enteric refers to the gut/digestive tracts; as many neurons as brain. Motility, secretion, blood flow. These collectively mediate 2 types of responses 1. Sympathetic : fight or flight emergency responses: Potential threat from a snake 2 . Parasympathetic : body wide conservation of energy; rest and digest If you are resting quietly after a meal, parasympathetic is dominant. Sympathetic vs. Parasympathetic Sympathetic: immediate response Vasodilation: less resistance, so more blood flow to muscles. Vasoconstriction: more resistance in visceral in abdominal organs Vasoconstriction when scared causes paleness. Smooth muscle in airway dilates to increase oxygen in blood Decrease secretion of saliva in kidney Increase alertness Parasympathetic: Recovery from this emergency state; Kick in when danger has passed 1
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Respiration to resting level Heart rate to resting level Vasoconstriction in limb muscles Vasodilation in viscera Constriction of lung airways Secretion returns to normal Alertness returns to normal ***Exam questions will focus on the mechanisms that cause these responses and drugs that are modified to hit these.Vast majority of drugs are ventured towards ANS*** CNS Regulating Centers CNS centers regulate ANS that are both command centers and for reflex control. The highest level of control is the hypothalamus and the pons. Many small nuclei in hypothalamus, in the walls next to the 3rd ventricle that control eating behavior, water balance, etc. Centers in hypothalamus also send info to other parts of the brain; to produce
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Study Guide 2 - Introduction to ANS Homeostasis maintenance...

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