Download Autonomic Nervous System

AUTONOMIC
NERVOUS SYSTEM
assoc. prof. Edyta Mądry MD, PhD
Department of Physiology
Poznań University of Medical Sciences
Basic Functions of the Nervous
System
1.
Sensation

2.
Integration

3.
Monitors changes/events occurring in and outside the
body. Such changes are known as stimuli and the cells
that monitor them are receptors.
The parallel processing and interpretation of sensory
information to determine the appropriate response
Reaction

Motor output.
–
The activation of muscles or glands (typically via the release
of neurotransmitters (NTs))
Nervous System’s Organization

2 big initial divisions:
1. Central Nervous System

The brain + the spinal cord
– The center of integration and control
2. Peripheral Nervous System


The nervous system outside of the
brain and spinal cord
Consists of:
– 31 Spinal nerves
 Carry info to and from the
spinal cord
– 12 Cranial nerves
 Carry info to and from the brain
Peripheral Nervous System


Responsible for communication btwn the CNS and the
rest of the body.
Can be divided into:
Sensory Division =Afferent division
– Conducts impulses from receptors to the CNS
– Informs the CNS of the state of the body interior and exterior
– Sensory nerve fibers can be
somatic (from skin, skeletal muscles or joints) or
visceral (from organs)
Motor Division=Efferent division
– Conducts impulses from CNS to effectors (muscles/glands)
– Motor nerve fibers
Motor Efferent Division

Can be divided further:
– Somatic nervous system
 Somatic nerve fibers that conduct impulses from
the CNS to skeletal muscles
– Autonomic nervous system
 Conducts impulses from the CNS to smooth
muscle, cardiac muscle, and glands.
Autonomic Nervous System

Can be divided into:
– Sympathetic Nervous System
– Parasympathetic Nervous
System
These 2 systems are antagonistic.
Typically, we balance these 2 to
keep ourselves in a state of
dynamic balance.
Autonomic Nervous System
– Sympathetic Nervous
System
 “Fight or Flight”
– Parasympathetic
Nervous System
 “Rest and Digest”
These 2 systems are antagonistic.
Typically, we balance these 2 to keep ourselves in a state of
dynamic balance.
Principal components of ANS

Central components:
hypothalamus, certain
brain stem regions and
nuclei, spinal cord

Peripheral
components:
ganglia and nerves
(both sensory and
efferent neurons)
Functional anatomy of ANS

Sympathetic division of ANS – central neurons
(preganglionic nerve cells) in the intermediolateral cell
column of the spinal cord (Th1-12 i L1-3)

Parasympathetic division of ANS - central neurons in the
nuclei of cranial nerves: oculomotor (III), facial(VII),
glossopharyngeal(IX), vagus(X) and in the
intermediolateral cell column of the spinal cord (S2-4)

Enteric nervous system (ENS) – neurons lying within the
walls of the gastrointestinal system (control of motility,
secretion and blood flow)
 adrenal
medulla !!!
Efferent pathways of ANS
(Th1-12 i L1-3)
(III, VII, IX, X, S2-4)
Autonomic ganglion
Gangionic transmision
Neuromodulation is the change in synaptic plasticity
EPSPs and IPSPs are examples of ways the non-all-or-none response
at the synapse can be changed.
Hexamethonium
Atropine
Hexamethonium
Collateral
inhibition
Adenosin
Postganglionic fibers
Amplifier and recorder
Neuronal potentials
Autonomic and somatic efferent
innervation
Efectors of ANS
smooth muscles
 heart
 glands
 nervous tissue
 adipose tissue

Principal components of ANS

Central components:

Peripheral components:
hypothalamus, certain
brain stem regions and
nuclei, spinal cord
ganglia and nerves (both
sensory and efferent
neurons)
Autonomic Nervous System:

controls visceral functions

conscious control – minimal (UNVOLUNTARY)
Somatic Nervous System:

controls skeletal muscles

under conscious control (VOLUNTARY)
AUTONOMIC
NERVOUSSystem
SYSTEM
Autonomic Nervous

Function of ANS is reflex
(see the end of presentation) and
simple autonomic reflexes
in the peripheral parts of
ANS may occur within
one organ
Adrenal medulla
medulla
Adrenal
Functionally related to the symathetic nervous system.
 It is regarded as a sympathetic ganglion in which the
postganglionic neurons have lost their axons and become
secretory cells
 After hypothalamic stimulation it releases catecholamines,
which may affect autonomic adrenic receptors

Polygraphy
Lie detection,
truth verification
Autonomic
Nervous
System
AUTONOMICZNY UKŁAD

Techniques based on
meditation allow, to a
certain degree,
consciously control
AUN.
The relaxation response -  in oxygen consumption,  HR,  RR,  respiration rate
Regulatory systems
Regulatory
systemsof
ofANS
ANS

Limbic system - „cerebral cortex of the ANS”
(cortically stored past experiences can be evoked
by external stimuli (smells,
sounds, sights).They can cause
emotional reactions leading
to strong visceral responses
coordinated by ANS)



Hypothalamus
Solitary nucleus of the medulla – coordinates heart and
respiratory functions
Circulating catecholamines – affect adrenergic receptors
General characteristics
characteristics of
General
of ANS
ANS

usually dual and antagonistic innervation of the
visceral organs

ganglia in the efferent pathways

large quantity of synapses in the ganglia

cotransmitters and neuromodulators
(they may coexist at most
ganglionic synapses )

postganglionic unmyelinated
nerve fibers in the efferent pathways
Comparison of efferent pathways
SNS and PNS
Anatomical
localization
PrePostTransmitter Transmitter
(nerve fiber
ganglionic ganglionic (ganglia)
ends)
fibers
fibers
Sympathetic Thoracolumbar
segments
(Th1-12; L13)
Short
Long
ACh
NE
ParaCranial and
sympathetic sacral
segments
Long
Short
ACh
ACh
(III, VII, IX,
X; S2-4)
Different nerve endings in ANS
Discrete („precise”) synapses of
PNS
Diffuse synapses of SNS activate
large surface area of one cell or
large number of cells
SNS – fight-or-flight respons

in the emergency situations; mobilization of
energy sources

increase in heart rate and force; RR

redistribution of blood from viscera
to active skeletal muscles and heart

inhibition of gastrointestinal activity

ACTH secretion and secretion of
catecholamines

dilation of respiratory airways

widening of pupil and accomodation for far
vision

„cold” sweating

total activation !!!
PNS –
feeding and vegetative behavior
“rest-and-digest”

energy accumulation from food (intestinal digestion and absorption);
waste products removal
increases intestinal motility
urination and defecation
activated partially according to body demands !!!!

dominates during the night



Sympathetic Trunks and
Pathways
A preganglionic fiber follows one of
three pathways upon entering the
paravertebral ganglia:
1. Synapses with the ganglionic
neuron within the same ganglion
2. Ascends or descends the
sympathetic chain to synapse in
another chain ganglion
3. Passes through the chain
ganglion and emerges without
synapsing
Paradoxical fear

PNS- normally dominates over
sympathetic impulses
Paradoxical fear
when there is no escape
route or no way to win
– causes massive
activation of
parasympathetic
division
– loss of control over
urination and
defecation
Acetylcholine metabolism
Acetylcholine
Choline acetyltransferase (ChAT)
Acetyl-CoA
+
Choline
Acetylcholinesterase (AchE)
Acetate
+
Choline
Norepinephrine metabolism
-NE may be recycled back into vesicles
for later release (80%)
-NE they may be degraded by the
enzymes: monoamine oxidase (MAO)
or catechol-O-methyltransferase
(COMT)
-NE may travel to the blood
NON-adrenergic sympathetic
fibers - examples

-
-
Cholinergic:
sweat glands (except hands)
vascular smooth muscles in skeletal muscle
salivary glands
vascular smooth muscles of penis (erection)
Histaminic:
- vascular smooth muscles of skeletal muscle, skin,
brain

Reflexes of ANS
Viscero-visceral
Viscero-somatic
Somato-visceral
From interoreceptors
– to internal organs
(effectors)
e.g. micturition,
defecation
From internal organs
to SNS
e.g. reffered pain or
muscular defense
From exteroreceptors
to internal organs
e.g. acupuncture,
warm compresses
(convergention of the
afferent pathways onto
one spinal segment)
Referred Pain
Pain stimuli arising
from the viscera are
perceived as
somatic in origin
- due to the fact that
visceral pain afferents
travel along the same
pathways as somatic
pain fibers
Referred Pain
Referred Pain
Referred Pain
Dr n. med. Edyta Mądry
Receptors for autonomic
transmitters
Cholinergic:
 Adrenergic:
nicotinic (N)
- muscarinic (M)
-
alpha 
-
beta 
-
Cholinergic nicotinic receptors( N)


-
ionotropic receptors are ion channels to which
neurotransmitters bind directly in order to open
them.
localization:
autonomic ganglia
adrenal medulla
motor end plate

activation (via Ach) produces fEPSP of
the ganglionic neurons

The effect of ACh binding to nicotinic receptors


is always stimulatory
agonist - nicotine
antagonist - atropine, hexamethonium (ANS),
curare (motor end plate)
Cholinergic muscarinic receptors
(M1-M8)
Work via the second messenger system (IP3 and DAG)
 M1 – postsynaptic membranes;
M2 – presynaptic membranes
 Agonist - muscarine
 Antagonist –
- atropine,scopolamine M2),
-pirenzepine (M1, M4)
 The effect of ACh binding:

– Can be either inhibitory or excitatory
– Depends on the receptor type of the target organ
Receptor type M2 – inhibition of adenylate
cyclase – outflux of K ions – membrane
hyperpolarization
Amanita muscaria-source of muscarine
Adrenergic receptors

Alpha receptors – norepinephrine
 Beta receptors - epinephrine
Adrenergic receptors 1




Rec 1 - salivary glands, mucus glands of bronchi,
muscles of: blood vessels, uterus, gastrointestinal tract
They work via the second messenger system (IP3)
Agonist – methoxamine,
phenylephrine
Antagonist –
prazosin (1)
and phentolamine
(nonselective)
Adrenergic
receptors
2
Adrenergic receptors 2


Rec 2 – mainly in the presynaptic terminals - autoreceptors;
their activation controls the amount of neurotansmitter that is
released (inhibition of reuptake-feedback inhibition)
Inhibition of adenylate cyclase and inhibition of cAMP
generation
Agonist – clonidine
Antagonist - yohimbine
Adrenergic receptors 1 and 2





1 - heart, kidney, adipose tissue; 2 – smooth muscles of
airways
second messenger - cAMP
Activation of presynaptic 2 receptors increases release of NE
(feedback excitation)
Agonist - phenoterol (2)
Antagonist - propranolol (nonselective), metoprolol (1)
Ganglionic transmission
Which of the autonomic receptors
is most important in ganglionic
transmission?
Phase 1:
ACh binds to N receptor on ganglionic cell causes depolarization
(fEPSP);
ACh binds to M1 receptor (SIF cells) causes dopamine release;
Dopamine binds to D1 receptor causing K+ permeability and hyperpolarization
(IPSP)
Phase 2:
ACh binds to M1 and M4 receptors causing K+ permeability andslow
depolarization (sEPSP)
Phase 3:
(lsEPSP) Gn-RH as a neuromodulator causes slow depolarization
The effects of ANS
1.
2.
Which system is responsible for
stress response?
Describe the changes in fight-orflight reaction
Adrenergic and cholinergic stimulation
Organ
SNS
PNS
Heart
 rate and force
(β1)
Bronchi
dilation (β2)
constriction (M3)
mucus–inhibition (α1) mucus-increase (M1)
Pupil
dilation (α1)
constriction (M1)
Adipose tissue
 lipolysis (β3)
no effect
Kidney
 urine production
(α1, β1)
 urine production
External male
reproductive organs
ejaculation (α1)
erection (M1)
 rate and force
(M1)
Adrenergic and cholinergic stimulation
Organ
SNS
PNS
Bladder
relaxation of
detrusor (β2, β3),
contraction of
internal sphincter(α)
contraction of
detrusor (M2, M3),
relaxation of
internal sphincter
Rectum
contraction of
internal sphincter,
relaxation of
smooth muscles
relaxation of
internal sphincter
contraction of
smooth muscles
Gastrointestinal
system
 peristalsis (β2 )
and gastric juice
production (α1, α2)
 peristalsis (M1)
and gastric juice
production (M1)
Salivary glands
production of high
viscosity saliva (α1)
 production of
watery saliva (M1)
Disorders of the Autonomic Nervous
System: Raynaud’s Disease

Raynaud’s disease – characterized by
constriction of blood vessels
– Provoked by exposure to cold or by
emotional stress
Disorders of the Autonomic
Nervous System: Hypertension

Hypertension – high blood pressure
– Can result from overactive sympathetic
vasoconstriction
Disorders of the Autonomic Nervous
System: Achalasia of the Cardia

Achalasia of the
cardia
– Defect in the
autonomic
innervation of the
esophagus
Quick repetition
cAMP receptors:
ATP
Adenylate cyclase
cAMP
Protein kinase A
Cellular effects: e.g. increased influx of Ca++ in heart; activation of
lipase in the adipose tissue  lipolysis
Quick repetition
Phosphatidylinositol cycle
receptors:
T+R+Gs+GTP
Phosphatidylinositol
biphosphate (PIP2)
Phospholipase C
Phosphatidylinositol
(PIP)
IP3
Inositol triphosphate
- release of Ca++ from ER
Protein kinase C
- protein phosphorylation
DG
diacylglycerol
- proton pump activation
Quick repetition
Convertion of an extracellular event - the binding
of a signal molecule – into an intracellular response
that modifies the behavior of target cell

Phase I – binding of first messenger (transmitter) to the receptor
(T+R)

Phase II – transduction of a signal into the intracellular
compartment. T+R complex interacts with a specific G-protein;
T+R+G complex binds GTP, which activates  subunit of G protein

Phase III – activated  subunit of G protein activates (or inhibits) a
specific enzyme (eg. adenylate cyclase or phospholipase C), which
causes synthesis of second messenger
Quick repetition
When a first messenger binds to a G-protein coupled receptor,
the receptor changes its conformation and activates several Gprotein  subunits. Each  subunit breaks away from the 
complex, and activates a single effector protein, which,
in turn, generates many
intracellular second
-messenger molecules.
One second messenger activates
many enzymes, and each
activated enzyme can regulate many
target proteins (amplification)
Quick repetition
Parasympathetic Responses
• Enhance “rest-and-digest” activities
• Mechanisms that help conserve and restore body energy during
times of rest
• Normally dominate over sympathetic impulses
• SLUDD type responses = salivation, lacrimation, urination,
digestion & defecation and 3 “decreases”--- decreased HR, diameter
of airways and diameter of pupil
• Paradoxical fear when there is no escape route or no way to win
– causes massive activation of parasympathetic division
– loss of control over urination and defecation
Quick repetition
Quick repetition
Reflexes
•
Reflex is a fast, involuntary, unplanned sequence of actions that occurs in
response to a particular stimulus.
•
•
Some reflexes are inborn ( pulling your hand away from a hot)
Other reflexes are learned or acquired.
60
Quick repetition
Reflex arc
•
•
The pathway followed nerve impulses that produce a reflex is a
reflex arc.
A reflex arc includes the following five function components:
– sensory receptor
– sensory neuron
– integrating center
– motor neuron
– effector