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
▪ Monitors changes/events occurring in and outside the body. Such changes are known as stimuli and the cells that monitor them are receptors.
2. Integration
▪ The parallel processing and interpretation of sensory information to determine the appropriate response
3. 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.
◼ Central components:
hypothalamus, certain brain stem regions and nuclei, spinal cord
◼ Peripheral
components:
ganglia and nerves (both sensory and efferent neurons)
Principal components 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 !!!
Functional anatomy of ANS
(Th1-12 i L1-3) (III, VII, IX, X, S2-4)
Efferent pathways of ANS
Autonomic ganglion
Ganglionic transmision
Autonomic and somatic efferent
innervation
◼
smooth muscles
◼
heart
◼
glands
◼
nervous tissue
◼
adipose tissue
Effectors of ANS
◼ Central components:
hypothalamus, certain brain stem regions and nuclei, spinal cord
◼ Peripheral components:
ganglia and nerves (both sensory and efferent
neurons)
Principal components of ANS
Autonomic Nervous System :
◼ controls visceral functions
◼ conscious control – minimal (UNVOLUNTARY)
Somatic Nervous Syste m:
◼ controls skeletal muscles
◼ under conscious control (VOLUNTARY)
AUTONOMIC NERVOUS SYSTEM
◼ 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
Autonomic Nervous System
Adrenal medulla
◼ 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
Adrenal medulla
Lie detection, truth verification
Polygraphy
AUTONOMICZNY UKŁAD
◼ Techniques based on meditation allow, to a certain degree,
consciously control AUN.
Autonomic Nervous System
The relaxation response - in oxygen consumption, HR, RR, respiration rate
Regulatory systems of 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
Regulatory systems of ANS
General characteristics of 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
General characteristics of ANS
Anatomical
localization Pre-
ganglionic fibers
Post-
ganglionic fibers
Transmitter
(ganglia) Transmitter
(nerve fiber ends)
Sympathetic Thoraco- lumbar segments (Th1-12; L1- 3)
Short Long ACh NE
Para-
sympathetic Cranial and sacral
segments (III, VII, IX, X; S2-4)
Long Short ACh ACh
Comparison of efferent pathways
SNS and PNS
Different nerve endings in ANS
Diffuse synapses of SNS activate large surface area of one cell or
large number of cells Discrete („precise”) synapses of
PNS
◼ 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 !!!
SNS – fight-or-flight respons
◼ 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
PNS –
feeding and vegetative behavior“rest-and-digest”
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
Sympathetic Trunks and
Pathways
◼
Paradoxical fear
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
PNS- normally dominates over
sympathetic impulses
Acetyl-CoA Choline+
Acetylcholine
Acetate Choline+
Choline acetyltransferase (ChAT) Acetylcholinesterase (AchE)
Acetylcholine 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
Norepinephrine metabolism
◼ 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
NON-adrenergic sympathetic
fibers - examples
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
(convergention of the afferent pathways onto
one spinal segment)
From exteroreceptors to internal organs
e.g. acupuncture, warm compresses
Reflexes of ANS
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
Referred Pain
VERY IMPORTANT
◼
The students are supposed to study the material about the receptors in ANS
( cholinergic and adrenergic) from the
textbook Guyton and Hall Textbook of
Medical Physiology ( pocket edition).
Adrenergic and cholinergic stimulation
Organ SNS PNS
Heart rate and force
(β1) rate and force
(M1) Bronchi dilation (β2)
mucus–inhibition (α1)
constriction (M3) 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)
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)
cAMP receptors:
ATP cAMP
Protein kinase A
Cellular effects: e.g. increased influx of Ca++ in heart; activation of lipase in the adipose tissue → lipolysis
Adenylate cyclase
Quick repetition
Phosphatidylinositol cycle receptors:
Phospholipase C
Phosphatidylinositol
biphosphate (PIP2) Phosphatidylinositol (PIP)
IP3
Inositol triphosphate
- release of Ca++ from ER
diacylglycerolDG Protein kinase C - proton pump activation
- protein phosphorylation
T+R+Gs+GTP
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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
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When a first messenger binds to a G-protein coupled receptor, the receptor changes its conformation and activates several G-protein 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)
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https://www.youtube.com/watch?v=ShBAvYDAV9I&index=6&list=PLXwnjgs_UWpIyKAZ 9yaEUbv8Sz1AMve45
Action of
Epinephrine
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Action of Epinephrine
Amplification
When a first messenger binds to a G-protein coupled receptor, the receptor changes its conformation and activates several G-protein 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
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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.
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