Guidelines for Exam 3 CHAPTER 14 THE ANS involved The ANS control center is primarily the hypothalamus but parts of the spinal cord may also be The output of the ANS regulates the following effectors The ANS consists of motor neurons that The ANS differs from the SNS in the following three areas Innervate supply of nerves smooth and cardiac muscle and glands Smooth muscle Cardiac muscle Exocrine and endocrine glands Adipose tissue Make adjustments to ensure optimal support for body activities Operate via subconscious control Have viscera as most of their effectors Effectors away from Efferent pathways Target organ responses Axons of the ANS are a two neuron chain An action potential arising from the spinal cord propagates along the myelinated axon of the preganglionic neuron The preganglionic neuron synapses with the cell bodies of a non myelinated postganglionic neuron at anautonomic ganglion o The preganglionic first neuron has a lightly myelinated axon o The ganglionic second neuron extends to an effector organ Efferent pathways Ganglia in ANS divisions Each division of the ANS has two kinds of motor neurons o Preganglionic first neuron has a lightly myelinated axon synapse in the chain paravertebral ganglia o Postganglionic second neuron muscle smooth muscle or a gland effector organs innervate the numerous organs of the body Two major groups of autonomic ganglia o Sympathetic ganglia between sympathetic preganglionic and postganglionic neurons are the sites of synapses Are near the spinal cord or major abdominal has an unmyelinated axon ending at cardiac arteries Connect with preganglionic motor neurons from the thoracic and lumbar segments of the spinal cord Two major types sympathetic trunk ganglia and prevertebral ganglia Paravertebral ganglia they form part of the sympathetic trunk or chain primarily innervate organs above the diaphragm Prevertebral ganglia innervate organs below the diaphragm Fibers from T5 L2 form splanchnic nerves abdomen and synapse with collateral prevertebral ganglia o Parasympathetic ganglia craniosacral division preganglionic axons of the parasympathetic division synapse with postganglionic neurons in terminal intramural ganglia Most of the parasympathetic ganglia are located very close to the organs of intended action ANS anatomy Parasympathetic and sympathetic Pathways to the adrenal medulla Sympathetic division helps support exercise of emergency actions the fight or flight responses o Involves E activities exercise excitement emergency and embarrassment o Regulates many functions not subject to parasympathetic influence These include the activity of the adrenal medulla sweat glands kidneys and most blood vessels o The sympathetic division promotes metabolic effects that are not reversed by the parasympathetic division Increases the metabolic rate of body cells Raises blood glucose levels Mobilizes fat as an energy source o Some sympathetic preganglionic axons pass thru the sympathetic trunk without terminating in it forming nerves know as splanchnic nerves which extend to outlying prevertebral ganglia Fibers of the thoracic splanchnic nerve pass directly to the adrenal medulla Upon stimulation medullary cells secrete norepinephrine NE and epinephrine EPI into the blood o The effects of sympathetic division are longer lasting and more widely spread than the parasympathetic division because 1 Motor pathways diverge to more effectors 2 Norepinephrine is deactivated more slowly than acetylcholine 3 Norepinephrine secreted from the adrenal medulla during times of stress increases and spreads the overall effect of NE that is released as a neurotransmitter Parasympathetic division takes care of rest and digest activites o Involves the D activities digestion defecation and diuresis o Its activity is illustrated in a person who relaxes after a meal Blood pressure heart rate respiratory rates are low Gastrointestinal tract activity is high The skin is warm and the pupils are constricted Think after lunch nap o responses of the parasympathetic nervous system Salivation increased Urination increased Digestion increased Defecation increased Visceral reflexes Most visceral organs are innervated by both sympathetic and parasympathetic fibers This results in dynamic antagonisms that precisely control visceral activity Sympathetic fibers increase heart and respiratory rates and inhibit digestion and elimination Parasympathetic fibers decrease heart and respiratory rates and allow for digestion and the discarding of wastes ANS physiology Neurotransmitters NT and receptors the effects of drugs are not included The inhibitory and stimulatory effects of catecholamines and Ach on the effector organs Cholinergic fibers ACh releasing fibers o Cholinergic neurons include 1 all sympathetic and parasympathetic preganglionic neurons 2 sympathetic postganglionic neurons that innervate most sweat glands 3 all parasympathetic postganglionic neurons o The effect of ACh binding Can be either inhibitory or excitatory Depends on the receptor type of the target organ o In postsynaptic cell membranes ACh binds with Nicotinic receptors always depolarize excite a cell when activated Muscarinic receptors may depolarize excite or hyperpolarize inhibit a cell when activated o ACh is rapidly removed from the synapse by acetylcholinesterase Adrenergic fibers sympathetic postganglionic axons that release NE o NE binds with receptors on the postsynaptic cell membrane and either depolarizes excites or hyperpolarizes inhibits the cell o The two types of adrenergic receptors are alpha and beta o Each type has two or three subclasses a1 a2 b1 b2 b3 o Effects of NE binding to a receptors is generally stimulatory b receptors is generally inhibitory o NE is slowly inactivated by monoamine oxidase MAO Chromaffin cells of adrenal medullae release epinephrine and norepinephrine NTs secreted by preganglionic and postganglionic autonomic neurons ACh and NE are the two major neurotransmitters of the ANS All sympathetic and parasympathetic preganglionic neurons secrete Ach All parasympathetic postganglionic neurons release Ach Most sympathetic postganglionic neurons release NE those to most sweat glands release ACh Chromaffin cells of adrenal medullae release epinephrine and norepinephrine CHAPTER 16 ENDOCRINE SYSTEM The endocrine system an overview The chemistry of hormones classification based on chemical structure Hormones are chemical substances secreted by cells into the blood that regulate the
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