1 A N S  NERVOUS SYSTEM  PNS CNS   EFFERENT AFFERENT   ANS SOMATIC  ENTERIC  PARASYMPATHETIC  SYMPATHETIC

2 Efferent neurons of ANS  brain stem or spinal cord  preganglionic neuron  ganglionic transmitter  Post ganglionic neuron  neuroeffector transmitter   effector organ 

3 ANS – Controls involuntary body functions BPDigestionElimination Some voluntary control Thermoregulation

4 ANS Anatomy Sympathetic & Parasympathetic – Sympathetic (Thoracolumbar) Neurons in thoracic and upper lumbar spine – Parasympathetic (Craniosacral) » Neurons in midbrain, brainstem, sacral region of spine

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7  Efferent neuron—from cns to effector organs  Afferent—neurons—important for reflex regulation of the system  Sympathetic neurons—originate in the cns and emerge from two different spinal cord regions==thoracic and lumbar regions of the spinal cord  Parasympathetic neurons—preganglionic fibers arise from cranium and sacral areas of spinal cord  Enteric neurons—collection of nerve fibers which innervate the gi tract, pancreas and gall bladder.

8 Functional Aspects of SNS & PNS » SNS _ fight or Flight – Increased cardiac output – Decreased visceral blood flow -- Increased cellular metabolism

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12 » PNS REST AND DIGEST REST AND DIGEST _ Conserves energy – Slows heart rate – Increased digestion _Increased absorption

13 PARASYMPATHETIC RESPONSES  slows heart rate  lowers blood pressure  increases gastrointestinal motility  empties the bowel and bladder  promotes absorption of nutrients

14 NERVE TERMINAL

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16  Cholinergic transmission :  acetylcholine is the neurotransmitter  primary means of terminating action is break down of acetylcholine into acetate & choline by acetylcholine esterase (AchE), found principally in neurons & neuromuscular junctions  cholinergic receptors are present in the parasympathetic nervous system, brain, ganglia of the sympathetic nervous system, and skeletal muscle  two main types of receptors present –muscarinic (principally autonomic nervous system) –nicotinic (principally skeletal muscle)

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18  Adrenergic transmission :  catecholamines (dopamine, norepinephrine, epinephrine) are the neurotransmitters  primary means of terminating action is by neural membrane reuptake of the transmitter, although metabolism by catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO) is important in some tissues.  adrenergic receptors –alpha-1: principally found in peripheral vascular smooth muscle –alpha-2: occur both presynaptically & postsynaptically

19  beta-1: located in the myocardium, SA node, ventricular conduction system, and adipose tissue  beta-2: vascular smooth muscle of the skin, muscles, mesentery & bronchial tree; stimulation results in vasodilation and bronchodilation

20 Function of the Adrenal Medulla – Synthesizes and secretes Epi & NE Sympathetic control » Fight or flight: pumps out Epi & NE to fight » Epinephrine : Adrenaline – Increases cardiac function & cellular metabolism more effectively than NE – Higher affinity for beta receptors » Norepinephrine (NE): Noradrenaline

21 Autonomic Receptors 2 main types 2 main types – Cholinergic: » ACH synapses – Adrenergic: » NE synapses

22 Cholinergic receptors Cholinergic receptors – 2 main categories » Nicotinic: Junction btwn preganglionic & postganglionic neurons in PNS & SNS Junction btwn preganglionic & postganglionic neurons in PNS & SNS – Any drug that affects nicotinic receptors affects both PNS & SNS 2 types of Nicotinic receptors: 2 types of Nicotinic receptors: – Type I (N N ): ANS – Type II (N M ): skeletal NMJ » Muscarinic

23 – Muscarinic – Muscarinic » All synapses btwn cholinergic postganglionic neurons & terminal effector cells PNS & SNS PNS & SNS – 5 subclasses: M 1, M 2 to M5 » Muscarinic receptors mediate effect on tissue

24 Adrenergic Receptor Sub classifications 2 Main Classes 2 Main Classes – Alpha (  ) »  -1 »  -2 – Beta (  ) »  -1 »  -2

25 RESPONSES ASSOCIATED WITH TYPES OF ADRENOCEPTORS Alpha1  arterial and arteriolar constriction (cutaneous, visceral, skeletal & pulmonary)  venous constriction  uterine contraction  pupillary dilation ( mydriasis )  (contraction of radial smooth muscle of iris)  contraction of ureter  contraction of spleen  contraction of pilomotor muscles

26 Alpha 2  inhibition of NE release  inhibition of ganglionic transmission  vasoconstriction (quantitatively less important than α1)

27 Beta 1  cardiac stimulation  (chronotropic, inotropic, dromotropic)  stimulation of lipolysis  stimulation of renin secretion

28 Beta 2  arteriolar dilation  (skeletal muscle, coronary visceral beds)  intestinal relaxation  bronchiolar relaxation  uterine relaxation  bladder body relaxation  Decrease of insulin release  skeletal muscle tremor  stimulation of glycogenolysis

29 chief therapeutic uses  vascular smooth muscle contraction…………………… …. α1  inhibition of transmitter release……………………… ……… α2

30 chief therapeutic uses  cardiac stimulation…………………………… β1  vascular smooth muscle relaxation…………………………. Β2  bronchiolar smooth muscle relaxation………………………. Β2