Atutonomic Nervous System

main function of autonomic nervous system

maintan homeostasis

what does the ANS control

• arteral pressure

• sweating

• body temp

• gastrointestinal motility nad secretion

• bladder emptying

three parts of ANS

sympathetic, parasympatheitc, and enteric

sympathetic ANS

fight or flight

parasympathetic ANS

yield rest and digest response

enteric ANS

controls responses in GI tract

Sympathetic ANS morphology

• originates in spinal cord between T1 and L2

• has pre and post ganglionic neuron

preganglionic neuron

• cell body in intermediolateral horn of spinal cord

• passes thru the ventral root of spinal cord and can synapse with postganglionic nerve in ganglia

three paths of preganglionic synapse

• synapse at ganglion

• travel thru sympathetic ganglion chain and synapse at another ganglion

• synapse with sympathetic nerve at peripheral ganglion

parasympathetic ANS morphology

• originates in spinal cord from CN III, VI, IX, and X

• pre and post ganglionic neuron

two paths of parasympathetic ANS

preganglionic neuron cell body leaves CNS and synapses with postganglionic neuron at gnaglia or within the walls of the organ

general control of sympathetic ANS

• fight or flight

• increase heart rate

• increase respiration rate, dilate bronchi

• increase blood flow to skeletal muscle

• dilate pupils

• reduce activity of digestive tract

general control of parasympathetic ANS

• rest and digest response

• decrease heart rate

• decrease respiration rate, constrct bronchi

• decrease blood flow to skeletal muscle, increase flow to skin

• constrict pupils

• increase activity in GI tract

what can ANS nerves secrete

acteylcholine (cholinergic) and norepinephrine (adrenergic)

all preganglionic neurons are…

cholinergic

almost all parasympathetic postganglionic neurons are…

adrenergic

most sympathetic postganglionic neurons

• adrenergic

• sweat galnds and some blood vessels are cholinergic

ACh synthesis

• produced in terminal endings

• stored in vesicles

• released to tissue and persist for a few seconds before being broken down by enzymes

norepinephrine production

• starts in terminal endings and ends in storage vesicles

• can be retaken up by nerve endings, secreted into circulation, or borken down by enzymes

• most norepinephrine is converted to epi and released into circulation

adrenal medulla

• inner part of adrenal cortex

• makes norepinephrine

what is rrsponsible for the inhibition/excitation of target tissues ??

receptors on cell membranes

chromaffin cell

• on adrenal medulla

• can synpase with sympathetic neuron

• dumps epi and norepi into blood so they can travel to target organs

ACh activates…

muscarinic or nicotinic receptor

muscarinic receptor

• activated by toadstool poision muscarine

• blocked by atropine

• use G proteins

nicotinic receptor

• activated by nicotine

• ligand gated

• blocked by hexamethonium

atropine

• dilates pupils for eye exams

• reduces saliva when given sublingually

class of adrenergic receptor

alpha and beta, linked to two different G proteins

alpha 1 receptor

increases vascular smooth muscle contraction

alpha 2 receptor

inhibit norepi and insulin release

beta 1 receptor

increase cardiac output

beta 2 output

• increase hepatic glucose output

• decrease contraction of blood vessles, bronchioles, and uterus

beta 3 output

• increase hepatic glucose output

• increase lipolysis

Alpha receptor functions

• vasoconstriction

• iris dilatio

• intestinal relaxation

• intestinal and ballder spinchter contraction

• pilomotor contraction

• inhibits neurotransmiter release

beta receptor function

• vasodilation

• cardioacceleration and increased myocardial strength

• intestinal and uterine relaxation

• bronchodilaiton

• calorigenesis

• glycogenesis/lipolysis

• bladder relaxation

• thermogenesis

brainstem components

• nucleus tract solitani

• area postrema

• ventrolateral medulla

• medulla raphe

• retricular formation

• parabrachial nucleus

brainstem controls

• bladder control

• heart rate

• bp

• respiration

• pneumotoxic center

forebrain compoenents

• hypothalamus

• prefrontal cortex

• entorhinal cortex

• insula

forebrain controls

• hunger, thirst, temp

• coordinating autonomic output

• can trigger fight or flight

what controls feedback loop in ANS

CNS

examples of decending cortial control of ANS

• fear

• panic attacks

• emotional stress

• seizures

• chronic stress

• sleep deprivation

• cognitive activity

• nervousness

when does visceral afferent overwhelms cotical function

• hunger

• thirst

• nausea

• visceral pain

• bladder and bowel distension

• hypo and hyperhtermia

broken heart syndrome

• caused by sudden emotional stress

• surge release of stress hromones, epi, norepi, and presence of sympathetic NS hyperactivity

• stress induced cardiomyopathy

phenylephrine

• sudafed, preparation h

• alpha 1 adrenergic agonist

albuterol

• bronchodilator for asthma and COPD

• beta 2 adrenergic agonist

amphetamine

causes relase of norepi from nerve endings

reserpine (serpasil)

• treats high bp

• blocks norepi synthesis

prazosin

• treats high bp

• alpha 1 adrenergic blocker

propanolol

• used for atrial fibrilation and high bp

• blocks beta 1 and 2 adrenergic receptor

pilocarpine

• used to treat dry mouth

• muscarinic agonist