1. AUTONOMIC NERVOUS SYSTEM
Sultan Ayoub Meo, MBBS, PGCMed Ed, M.Phil, Ph.D
Professor, Department of Physiology, College of Medicine King Khalid University Hospital, Riyadh, Saudi Arabia

2. THE NERVOUS SYSTEM Central Nervous System Peripheral Nervous System
A. Brain
Fore brain: Cerebrum, Diencephalon (Thalamus, Metathalamus, Epithalamus, Hypothalamus and subthalamus
Mid brain
Hind brain: Pons, Medulla oblongata, Cerebellum
Spinal cord

3. THE NERVOUS SYSTEM 2. Peripheral nervous system:
a) Somatic Nervous System:
b) Autonomic Nervous System
i. Sympathetic nervous system
ii. Para sympathetic nervous system

4. THE NERVOUS SYSTEM
The nervous system monitors and controls almost every organ / system through a series of positive and negative feedback loops.
The Central Nervous System (CNS): Includes the brain and spinal cord.
The Peripheral Nervous System (PNS): Formed by neurons & their process present in all the regions of the body. It consists of cranial nerves arises from the brain & spinal nerves arising from the spinal cord. This again divided into
Somatic Nervous system
Autonomic nervous system

5. THE PERIPHERAL NERVOUS SYSTEM
The peripheral nervous system is divided into:
Somatic nervous system: which controls organs under voluntary control (mainly muscles)
Autonomic Nervous System (ANS): It regulates individual organ function and homeostasis and for the most part is not subject to voluntary control. It is also known as the visceral or automatic system.

6. CHEMICAL DIVISION OF THE ANS
Cholinergic
Nor Adrenergic
The neurons that are cholinergic are
Are pre ganglionic neurons
Anatomicallt para syampatheic post ganglionic neuron
Anatomical;lt syampatheic post ganglionic neuron ineervate sweet glands
Anatomically syampatheic neurons that end on blood vessels in skeletal muscles & produce vasodilatation
The remaining post ganglionic sympathetic neurons are nor adrenergic

7. SOMATIC NERVOUS SYSTEM
The somatic nervous system includes the nerves supplying the skeletal muscles.
Thus the somatic nervous system controls the movements of the body by acting on skeletal muscles.

8. THE AUTONOMIC NERVOUS SYSTEM
Autonomic nervous system (ANS):
Innervates organs whose functions are not usually under voluntary control.
Effectors include cardiac and smooth muscles and glands.
Effectors are part of visceral organs and blood vessels

9. THE AUTONOMIC NERVOUS SYSTEM
The Autonomic nervous system is concerned with regulation of visceral or vegetative function. Therefore also called vegetative or involuntary nervous system
The autonomic nervous system (ANS) is a regulatory structure that helps people adapt to changes in their environment.
It adjusts or modifies some functions in response to stress.

10. THE AUTONOMIC NERVOUS SYSTEM
Anatomical & functional basis ANS is divided into two separate divisions:
Sympathetic systems
Parasympathetic system
Both of these systems consist of myelinated preganglionic fibres which make synaptic connections with unmyelinated postganglionic fibres, and then innervate the effector organ
These synapses usually occur in clusters called ganglia.

11. DIVISION OF THE AUTONOMIC
NERVOUS SYSTEM
Subdivision
Nerves Employed
Location of Ganglia
Chemical Messenger
General Function
Sympathetic
Thoracolumbar
Alongside vertebral column
Norepinephrine
Fight or flight
Parasympathetic
Craniosacral
On or near an effector organ
Acetylcholine
Conservation of body energy

12. BASIC ANATOMY OF ANS Preganglionic neuron:
Cell body in brain or spinal cord
Axon is myelinated type fiber that extends to autonomic ganglion
Postganglionic neuron:
Cell body lies outside the CNS in an autonomic ganglion
Axon is unmyelinated type fiber that terminates in a visceral effector

13. BASIC ANATOMY OF ANS 2 neurons in the efferent pathway.
1st neuron has its cell body in gray matter of brain or spinal cord.
Preganglionic neuron.
Synapses with 2nd neuron within an autonomic ganglion.
Postganglionic neuron.
Autonomic ganglion has axon which extends to synapse with target tissue.

14. BASIC ANATOMY OF ANS

15. Adrenergic Cholinergic
ANS Neurotransmitters:  Classified as either cholinergic or adrenergic neurons based upon the neurotransmitter released
Adrenergic
Cholinergic

16. ANS
Preganglionic autonomic fibers originate in midbrain, hindbrain, and upper thoracic to 4th sacral levels of the spinal cord.
Autonomic ganglia are located in the head, neck, and abdomen
Presynaptic neuron is myelinated and postsynaptic neuron is unmyelinated
Autonomic nerves release NT that may be stimulatory or inhibitory.

17. LOCATIONS OF AUTONOMIC GANGLIA
Overview of actions
LOCATIONS OF AUTONOMIC GANGLIA
Sympathetic Ganglia:
Trunk (chain) ganglia near vertebral bodies
Prevertebral ganglia near large blood vessel in gut
celiac superior mesenteric
inferior mesenteric
Parasympathetic Ganglia:
Terminal ganglia in the wall of organ

18. AUTONOMIC PLEXUSES Cardiac plexus Pulmonary plexus Celiac plexus
Overview of actions
AUTONOMIC PLEXUSES
Cardiac plexus
Pulmonary plexus
Celiac plexus
Superior mesenteric
Inferior mesenteric
Hypogastric

19. SYMPATHETIC & PARASYMPATHETIC NERVOUS SYSTEM
Blue= Para symp; Red symp

20. The Sympathetic Nervous System

21. The Parasympathetic Nervous System

22. THE AUTONOMIC NERVOUS SYSTEM
The ANS is predominantly an efferent system transmitting impulses from the Central Nervous System (CNS) to peripheral organ systems.
Its effects include:
Control of heart rate and force of contraction
Constriction and dilatation of blood vessels
Contraction and relaxation of smooth muscle
Visual accommodation
Pupillary size and secretions from exocrine and endocrine glands.

23. The Autonomic Nervous System
Structure
Sympathetic Stimulation
Parasympathetic Stimulation
Iris (eye muscle)
Pupil dilation
Pupil constriction
Salivary Glands
Saliva production reduced
Saliva production increased
Oral/Nasal Mucosa
Mucus production reduced
Mucus production increased
Heart
Heart rate and force increased
Heart rate and force decreased
Lung
Bronchial muscle relaxed
Bronchial muscle contracted
Stomach
Peristalsis reduced
Gastric juice secreted; motility increased
Small Intes
Motility reduced
Digestion increased
Large Intes
Secretions and motility increased
Liver
Increased conversion of glycogen to glucose
    
Kidney
Decreased urine secretion
Increased urine secretion
Adrenal medulla
Norepinephrine and epinephrine secreted
Bladder
Wall relaxed Sphincter closed
Wall contracted Sphincter relaxed

24. Sympathetic (adrenergic, with exceptions)
Parasympathetic (muscarinic)
circulatory system
cardiac output
increases
M2: decreases
SA node: heart rate (chronotropic)
β1, β2: increases
cardiac muscle: contractility (inotropic)
M2: decreases (atria only)
conduction at AV node
β1: increases
vascular smooth muscle
M3: contracts; α = contracts; β2 = relaxes
---
platelets
α2: aggregates
mast cells - histamine
β2: inhibits

25. Sympathetic (adrenergic, with exceptions) Parasympathetic (muscarinic)
Overview of actions
Sympathetic (adrenergic, with exceptions)
Parasympathetic (muscarinic)
respiratory system
smooth muscles of bronchioles
β2: relaxes (major contribution); α1: contracts (minor contribution)
M3: contracts
nervous system
pupil of eye
α1: relaxes
ciliary muscle
β2: relaxes

26. Overview of actions Sympathetic (adrenergic, with exceptions)
Parasympathetic (muscarinic)
digestive system
salivary glands: secretions
β: stimulates viscous, amylase secretions; α1 = stimulates potassium cation
stimulates watery secretions
lacrimal glands (tears)
decreases
M3: increases
kidney (renin)
secretes
---
parietal cells
M1: secretion
liver
α1, β2: glycogenolysis, gluconeogenesis
adipose cells
β3: stimulates lipolysis
GI tract motility
M1, M3: increases
smooth muscles of GI tract
α, β2: relaxes
M3: contracts
sphincters of GI tract
α1: contracts
M3: relaxes
glands of GI tract
inhibits
M3: secretes

27. Overview of actions Sympathetic (adrenergic, with exceptions)
Parasympathetic (muscarinic)
ENDOCRINE
pancreas (islets)
α2: decreases secretion
---
adrenal medulla
N: secretes epinephrine
urinary system
bladder wall
β2: relaxes
contracts
ureter
α1: contracts
relaxes
sphincter
α1: contracts; β2 relaxes
reproductive system
uterus
α1: contracts; β2: relaxes
genitalia
α: contracts
M3: erection
integument
sweat gland secretions
M: stimulates (major contribution); α1: stimulates (minor contribution)
arrector pili
α1: stimulates

28. PARASYMPATHETIC NERVOUS SYSTEM
The preganglionic outflow of the parasympathetic nervous system arises from
Cell bodies of the motor nuclei of the cranial nerves III, VII, IX and X in the brain stem
Second, third and fourth [S2-S4] sacral segments of the spinal cord. It is therefore also known as the cranio-sacral outflow

29. PARASYMPATHETIC NERVOUS SYSTEM
The cranial nerves III, VII and IX affect the pupil and salivary gland secretion
Vagus nerve (X) carries fibres to the heart, lungs, stomach, upper intestine and ureter
The sacral fibres form pelvic plexuses which innervate the distal colon, rectum, bladder and reproductive organs.

30. PARASYMPATHETIC NERVOUS SYSTEM
The parasympathetic nervous system has "rest and digest" activity.
In physiological terms, the parasympathetic system is concerned with conservation and restoration of energy, as it causes a reduction in heart rate and blood pressure, and facilitates digestion and absorption of nutrients, and consequently the excretion of waste products
The chemical transmitter at both pre and postganglionic synapses in the parasympathetic system is Acetylcholine (Ach).

31. PARASYMPATHETIC RESPONSE
Overview of actions
PARASYMPATHETIC RESPONSE
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
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

32. ORGANS INNERVATED BY SYMPATHETIC NS
Overview of actions
ORGANS INNERVATED BY SYMPATHETIC NS
Structures innervated by each spinal nerve:
Sweat glands, arrector pili, blood vessels to skin & skeletal mm.
Thoracic & cranial plexuses supply: Heart, lungs, esophagus & thoracic blood vessels Plexus around carotid artery to head structures
Splanchnic nerves to prevertebral ganglia supply:
GIT from stomach to rectum, urinary & reproductive organs

33. SYMPATHETIC NERVOUS SYSTEM
Cell bodies of the sympathetic preganglionic fibres are in the lateral horns of the spinal segments T1-L2, called thoraco-lumbar outflow.
The preganglionic fibres travel a short distance in the mixed spinal nerve and then branch off as white rami (myelinated) to enter the sympathetic ganglia.
These are mainly arranged in two paravertebral chains which lie anterolateral to the vertebral bodies and extend from the cervical to the sacral region. They are called the sympathetic ganglionic chains.

34. SYMPATHETIC NERVOUS SYSTEM
The short preganglionic fibres which enter the chain make a synapse with a postsynaptic fibre either at the same dermatomal level, or at a higher or lower level
The longer postganglionic fibres usually return to the adjacent spinal nerve via grey rami (unmyelinated) and are conveyed to the effector organ.

35. SYMPATHETIC NERVOUS SYSTEM
FEAR, FLIGHT OR FIGHT
The sympathetic system enables the body to be prepared for fear, flight or fight
Sympathetic responses include an increase in heart rate, blood pressure and cardiac output
Diversion of blood flow from the skin and splanchnic vessels to those supplying skeletal muscle
Increased pupil size, bronchiolar dilation, contraction of sphincters and metabolic changes such as the mobilisation of fat and glycogen.

36. FUNCTIONS OF SYMPATHETIC NERVOUS SYSTEM
Frequently referred to as the fear, flight or fight system
It has a stimulatory effect on organs and physiological systems, responsible for rapid sensory activity (pupils in the eye) and movement (skeletal muscle).
It diverts blood flow away from the GIT and skin via vasoconstriction.
Blood flow to skeletal muscles, lungs is not only maintained, but enhanced (by as much as 1200%), in case of skeletal muscles.

37. FUNCTIONS OF SYMPATHETIC NERVOUS SYSTEM
Bronchioles dilate, which allows for greater alveolar oxygen exchange.
It increases heart rate and the contractility of cardiac cells (myocytes), thereby providing a mechanism for the enhanced blood flow to skeletal muscles.
Sympathetic nerves dilate the pupil and relax the lens, allowing more light to enter the eye.

38. Emergency, Embarrassment, Excitement, Exercise
Overview of actions
SYMPATHETIC RESPONSE
Dominance by the sympathetic system is caused by physical or emotional stress “E situations”
Emergency, Embarrassment, Excitement, Exercise
Alarm reaction = flight or fight response:
Dilation of pupils
Increase heart rate, force of contraction & BP
Decrease in blood flow to nonessential organs
Increase in blood flow to skeletal & cardiac muscle
Airways dilate & respiratory rate increases
Blood glucose level increase

39. ADRENALINE & NOR ADRENALINE
Adrenaline and noradrenaline are both cate-cholamines
Both synthesized from the essential amino acid phenylalanine by a series of steps, which includes the production of dopamine.
The terminal branches of the sympathetic postganglionic fibres have varicosities or swellings, giving them the appearance of a string of beads.
These swellings form the synaptic contact with the effector organ, and are also the site of synthesis and storage of noradrenaline.

40. ADRENALINE & NOR ADRENALINE
On the arrival of a nerve impulse, noradrenaline is released from granules in the presynaptic terminal into the synaptic cleft.
The action of noradrenaline is terminated by diffusion from the site of action, re-uptake back into the presynaptic nerve ending where it is inactivated by the enzyme Monoamine Oxidase in mitochondria or metabolism locally by the enzyme Catechol-O-Methyl-Transferase.

41. Overview of actions
RECEPTORS
The parasympathetic nervous system uses only acetylcholine (ACh) as its neurotransmitter.
The ACh acts on two types of receptors, the muscarinic and nicotonic choloinergic receptors.
Most transmissions occur in two stages: When stimulated, the preganglionic nerve releases ACh at the ganglion, which acts on nicotinic receptors of the postganglionic nerve.
The postganglionic nerve then releases ACh to stimulate the muscarinic receptors of the target organ.

42. TYPES OF MUSCARINIC RECEPTORS
Overview of actions
TYPES OF MUSCARINIC RECEPTORS
The three main types of muscarinic receptors:
M1 muscarinic receptors: located in the neural system.
M2 muscarinic receptors: located in the heart, and act to bring the heart back to normal after the actions of the sympathetic nervous system: slowing down the heart rate, reducing contractile forces of the atrial cardiac muscle, and reducing conduction velocity of the SA and AV node.
Note, they have no effect on the contractile forces of the ventricular muscle.

43. TYPES OF MUSCARINIC RECEPTORS
Overview of actions
TYPES OF MUSCARINIC RECEPTORS
M3 muscarinic receptors: located at many places in the body, such as the smooth muscles of the blood vessels, as well as the lungs, which means that they cause vasoconstriction & bronchioconstriction and.
They are also in the smooth muscles of the GIT, which help in increasing intestinal motility and dilating sphincters.
M3 receptors are also located in many glands that help to stimulate secretion in salivary glands and other glands of the body.

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