Autonomic Nervous System: A Pharmacological Perspective Flashcards by An Nakamura

Definition of autonomic nervous system

Neuronal groups and fibre connections they control heart, visceral organ, blood vessels ad gland activity and maintains homeostasis

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Definition of adrenergic

Relating to nerve cells where adrenaline, noradrenaline or similar substances act as a neurotransmitter

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Definition of cholinergic

Relating to nerve cells where acetylcholine acts as a neurotransmitter

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Definition of contransmission

When other neurotransmitters are released along with acetylcholine or noradrenaline

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Responses to a change in the environment and the varying demands on the body
Rapid
2 types

Voluntary, somatic nervous system => skeletal muscles

Involuntary, ANS => CV system, other organs

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What is the autonomic nervous system

Neuronal groups and fibre connections that control activity of heart, viscera and vasculature, smooth muscle and glands

Maintains homeostasis directly/indirectly

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Function of the parasympathetic branch

Digestion, excretion, visual accommodation
Rest and digest state
Localized innervation

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Function of the sympathetic branch

Ongoing control of cardiovascular system and reflex response to stressful situations
Fight/flight state
More widespread innervation and effects

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Type of efferent nerve pathways, parasympathetic salivary gland

Long preganglionic, Ach released onto N receptors

Ach released onto M receptors (salivary gland)

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Type of efferent nerve pathways,

Sympathetic vasculature

Short preganglionic, Ach released onto N receptors

NA released onto adrenergic receptors (blood vessels)

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Type of efferent nerve pathways,

Sympathetic sweat glands

Short preganglionic, Ach released onto N receptors

Ach released onto M receptors (sweat gland)

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Type of efferent nerve pathway

Sympathetic adrenals

Long nerve, Ach released onto N receptors on adrenal medulla

NA/A released into blood, adrenergic receptors

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Types of cholinergic receptors

Muscarinic

Nicotinic

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Muscarinic receptors

Structure
M2?
M3?

5 subtypes M1-M5
G protein coupled

M2, cardiac => Gai/o => decrease in cAMP, slow HR and contractile force
M3, smooth muscle/glandular => Gaq => increase in IP3 and DAG => contract

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Nicotinic receptors

Structure
N1
N2

5 subunits

N1, muscle receptor
N2, ganglionic receptor

Non selective cation channel, mainly admits Na+, K+, causes rapid cell depolarization

2 Ach binds to a1 subunits

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a adrenergic receptors

Subtypes and functions

2 subtypes
a1, a2, each has 3 sub subtypes

a1 = Gq, stimulates IP3/DAG => increase [Ca2+]
In blood vessels

a2 = Gi, inhibits AC => decreases cAMP
Presynaptically, decrease release of NA

b adrenergic receptors

Subtypes and functions

3 subtypes, all activate Gs, increase cAMP via PKA

b1, main cardiac subtype
b2, main vascular, airways subtype (SMOOTH MUSCLE)
b3, mainly found in adipose and detrusor

Non adrenergic, non cholinergic neurotransmitters (NANC)
What are they
Why are they useful

Sometimes, Ach/NA released w other NT = cotransmitters
Stronger levels of stimulation => different NT release patterns
Allows for differential target cell function control
Occurs in ganglionic and post ganglionic synapses
V imp in CNS and ENS

Opposing sympathetic and parasympathetic effects
Heart rate

Nerves responsible

SAN stimulated => increased HR, BP, CO, force

VIA VAGUS
SAN inhibited => decreased HR, BP, CO
AVN innervated => decreased conduction speed to B of H

Opposing sympathetic and parasympathetic effects

GI tract, bladder and defaecation

Decreased GI motility, sphincter contraction, decreased digestion
Relaxed detrusor

VIA VAGUS
Relaxed sphincters, peristalsis

VIA PELVIC
Detrusor contracts, defaecation

Opposing sympathetic and parasympathetic effects

Airways

Increased bronchodilation

VIA VAGUS
Increased bronchoconstriction

Opposing sympathetic and parasympathetic effects

Pupils

Pupil dilation via iris dilator contraction

VIA OCULOMOTOR
Pupil constriction via iris sphincter
Visual accommodation via cililary muscle contraction

Opposing sympathetic and parasympathetic effects

Erection

Ejaculation

VIA PELVIC
Erection

Effects of the sympathetic and parasympathetic on vasculature

VC of splanchnic circulation
Heart artery dilation and skeletal muscle

VIA VAGUS
VD of splanchnic, renal (does not affect TPR)

VIA PELVIC
VD of penile (does not affect TPR)

Antagonistic effects of SNS and PNS on HR

SNS and PNS drive to organ is reciprocal Opposing effects provide wide dynamic range over which organs can alter behavior Under rest, HR is PNS dominated One is excitatory, the other is inhibitory

The baroreceptor reflex

Increase in BP distends arterial wall, stimulates afferent nerve endings Signal sent to brain stem (Nucleus tracts solitairius), compares BP to set point Innervates parasympathetic, decrease HR and CO Innervates sympathetic, decrease HR, CO, arterial constriction, TPR, venous constriction BP falls to set point

Process of cholinergic neurotransmission

Acetyl CoA + Choline => Ach with choline acetyletransferase Ach stored in vesicel to be released when [Ca2+] is high Ach binds to receptor, depolarizes post synaptic membrane Acetylcholinesterase breaks down Ach into choline and acetate and reabsorbed by presynaptic membrane

Inhibition of Ach breakdown Medication? Effects?

Ecothiopate/NEOGISTIME inhibits cholinesterase in the eye Increases pupillary constriction increases aqueous humous decreases intraocular pressure Increased salivation/sweating

ENS What are the 2 types What do they release

Myenteric and submucosal plexus of sensory, motor and interneurons, form 2 layers in GI tract walls Uses variety of NANC NT, including Ach, vasoactive intestinal polypeptides and NO

Function of ENS

Coordinates and controls peristalsis, fluid transport, glandular secretion, blood flow Effects on PNS, SNS on GI tract indirectly exerted by ENS

Effects of the sympathetic nervous system on the kidney and skin

Increased renin release from JGA | Piloerection

Inhibition of ACh Medication? Effects?

Botulinum toxin prevents Ach exocytosis Prevents M receptor stimulation -bladder relaxation

Importance of PKA in Gs

PKA phosphorylates L type, Ryanodine receptors, PLB, SR in b1 Myosin light chain kinase in b2