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Autonomic Nervous System ANS Honors Anatomy & Physiology for copying.

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Presentation on theme: "Autonomic Nervous System ANS Honors Anatomy & Physiology for copying."— Presentation transcript:

1 Autonomic Nervous System ANS Honors Anatomy & Physiology for copying


3 Comparison Of Autonomic & Somatic Nervous Systems

4 2 Neuron Chain


6 Preganglionic Neurons SympatheticParasympatheitc 1st neuron in spinal cord: thoracic and lumbar spinal nerves 1st neuron in 4 cranial nerves in the brain stem (III, VII, IX, X) or in S2 –S4 of spinal cord

7 Postganglionic Neurons SympatheticParasympathetic 2 nd neuron in sympathetic trunk ganglion, a chain of ganglion that is found on either side lateral to spine 2 nd neuron in individual ganglion closer to organ it serves both sympathetic & parasympathetic neurons lie outside CNS

8 Axons of Autonomic Nerves Preganglionic: – in cranial or spinal n. (from CNS  ganglion) – myelinated Postganglionic: – from ganglion  visceral effector – unmyelinated

9 ANS Neurotransmitters based on the neurotransmitter they produce & release autonomic neurons are classified as either: 1.Cholinergic release acetylcholine (ACh) 1.Adrenergic release norepinephrine (NE) aka noradrenalin

10 Cholinergic Neurons & Receptors Cholinergic neurons include: 1.all Sympathetic & Parasympathetic preganglionic neurons 2.Sympathetic postganglionic neurons that innervate most sweat glands 3.all Parasympathetic postganglionic neurons

11 Receptors that bind ACh called cholinergic receptors 2 types: 1.Nicotinic receptors in plasma membranes & dendrites of symp. & parasymp postganglionic neurons & in NMJ 1.Muscarinic receptors in plasma membrane of all effectors (smooth muscle, cardiac muscle, glands) Muscarine: mushroom poisonmimics actions of ACh

12 ACh when activates nicotinic receptors  depolarization (excitation) when activates muscarinic receptors  sometimes depolarization, sometimes hyperpolarization (inhibition) depending on the cell


14 NE most sympathetic postganglionic neurons are adrenergic Adrenergic receptors bind both NE & Epinephrine (Epi) 2 types receptors: 1.Alpha receptors (α) – subtypes: α1, α2 2.Beta receptors (β) – subtypes: β1, β2, β3

15 αlpha & βeta Receptors α1 & β1 produce excitation when activated α2 & β2 receptors cause inhibition of effector tissues β3 found only on cells of brown adipose where activation causes thermogenesis (heat production)

16 αlpha & βeta Receptors cells of most effectors have either α or β receptors some visceral effectors contain both NE stimulates α more strongly than β Epi is potent stimulator of both

17 MAO MonoAmine Oxidase: inactivates NE in synaptic cleft group of pharmaceuticals that are MAO inhibitors so prolong effect of NE

18 Agonists substance that binds to & activates a receptor in the process mimicking the effect of a natural neurotransmitter or hormone example: phenylephrine is an adrenergic agonist @ α1 receptors; used in cold remedies – constricts blood vessels in nasal mucosa  reduces production of mucus

19 Antagonists substance that blocks receptors so prevents the natural neurotransmitter or hormone from exerting its effect example: propanolol a β1 blocker, used to treat HTN  decreases heart rate & force of contraction  lowers BP – side effects: hypoglycemia, mild bronchoconstriction, decreases frequency & severity of migraines


21 Autonomic Tone balance between sympathetic & parasympathetic activity regulated by hypothalamus – if turns up sympathetic tone, turns down parasympathetic tone @ same time

22 Sympathetic Responses dominate during physical or emotional stress occur during “E situations” – Exercise – Emotions – Emergency – Excitement

23 Sympathetic Responses Fight or Flight Response – pupils dilate – HR, force of contraction, & BP increase – airways dilate – vessels to kidneys & GI tract constrict slowing down digestion & urine production – vessels  muscles (skeletal & cardiac), liver, & adipose tissue  dilate – hepatocytes increase glycogenolysis & adipose increase lipolysis  blood glucose increases – anything nonessential slowed down

24 Sympathetic Stimulation effects longer lasting than parasympathetic responses (NE lasts longer in synaptic cleft than ACh) effects are more widespread (more tissues activated)

25 Parasympathetic Responses enhance “rest & digest” activities remeber SLUDD: – Salivation – Lacrimation – Urination – Digestion – Defecation


27 Disorders of the ANS Raynaud’s phenomena: digits become ischemic after exposure to cold or w/ emotional stress due to excessive sympathetic stimulation of smooth muscle in arterioles in digits & increased response to stimuli that cause vasoconstriction

28 Raynaud’s Phenomenon treatment options: Ca++ channel blockers to relax smooth muscle Prazosin: blocks α receptors which blocks smooth muscle contractions

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