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Sensory neurons
afferent (into CNS)
-
Motor Neurons
efferent (instructions from CNS)
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Effects of Sympathetic Division
"fight or flight"
- increase HR
- increase cardiac contractility
- vasodilate skeletal muscle (increase blood flow)
- vasoconstriction in viscera/skin (decrease blood flow)
- Bronchodilation
- Inhibit GI and urinary tracts
- Sweating
- Piloerection
- Mydriasis (dilation)
- Accomodation for far vision
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Effects of Parasympathetic Division
"rest and digest"
- -decrease HR
- -decrease cardiac contractility
- -bronchoconstriction
- -Stimulation of GI and urinary tracts
- -miosis (constriction)
- -accomodation for near vision
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Systems only under Sympathetic control
- -most blood vessels
- -sweat glands
- -pilomotor muscles
- -adrenal medulla
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Systems predominantly controlled by Parasympathetic Division
- -GI tract
- -Urinary tract
- -eye
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Adrenal Medulla
- -secretes EPI and small amounts of NE into blood
- -activated during 'fight or flight'
- -innervated by thoracolumbar cord
-
Termination of ANS NT actions
- 1. Enzyme inactivation (ACh by AChE)
- 2. Reuptake by presynaptic fiber (NE uptake by NET)
- 3. Diffusion away from junction
- 4. Uptake by extraneuronal sites
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Cholinergic Receptors
- 1. Nicotinic (ligand gated ion channels)
- -NN: on all ANS post-ganglionic neuron somas
- -NM: on SKM
- 2. Muscarinic (GPCR)
- -M1 (Gq): on somas of postganglionic neurons in ANS ganglia
- -M2 (Gi): on heart
- -M3 (Gq): on smooth muscle and glands, on VSM (non innervated)
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Adrenergic Receptors
- 1. alpha
- -a1 (Gq): smooth muscle, eye, pilomotor, sphincters of GI and urinary tract
- -a2 (Gi): a little on smooth muscle, in the CNS, on sympathetic and parasympathetic postganglionic fibers
- 2. beta
- -b1 (Gs): heart (SA, AV node, atria, ventricles), kidney (granular cells)
- -b2 (Gs): smooth muscle (vascular, bronchial, GI, ciliary muscle)
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