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Autonomic nervous system

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AUTONOMIC NERVOUS SYSTEM PRESENTED BY: LAHARI PALADUGU PHARM D (09-10) ENTERIC NERVOUS SYSTEM. Consists of intramural nerve plexesus: (a) myenteric plexus (b ... – PowerPoint PPT presentation

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Title: Autonomic nervous system


1
Autonomic nervous system
  • Presented by
  • Lahari paladugu
  • Pharm d (09-10)

2
definition
  • The autonomic nervous system (ANS or visceral
    nervous system or involuntary nervous system) is
    the part of the peripheral nervous system that
    acts as a control system, functioning largely
    below the level of consciousness, and controls
    visceral functions.
  • The ANS affects heart rate, digestion,
    respiratory rate, salivation, perspiration,
    pupillary dilation, micturition, and sexual
    arousal.
  • Most autonomous functions are involuntary but a
    number of ANS actions can work alongside some
    degree of conscious control.

3
LOCATION
  • Within in the brain, the autonomic nervous system
    is located in the medulla oblongata in the lower
    brainstem.
  • The hypothalamus, just above the brain stem, acts
    as an integrator for autonomic functions,
    receiving ANS regulatory input from the limbic
    system to do so.

4
  • DIVISIONS

5
A N A T O M Y
6
Sympathetic nervous system
  • It has
  • A central controlling part
  • A peripheral portion which takes origin in the
    lateral horn of the spinal cord from T1 to L2.
    The main cerebral controlling center is the
    posterior hypothalamus.
  • The peripheral portions has
  • Afferent fibers
  • Efferent fibers

7
(thoracolumbar) Outflow of sympathetic fibers
  • Consists of cell bodies in the lateral horn of
    the spinal cord (intermediolateral cell columns)
    from T1 to L2/3.
  • Because its cells begin in the thoracic and
    lumbar regions of the spinal cord, the SNS is
    said to have a thoracolumbar outflow.

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Organization.
  • Take origin from the lateral horn cells of T1 to
    L2 and come out of the spinal cord via the
    anterior root.
  • Axons of these nerves leave the spinal cord
    through the anterior rootlet/root. They pass near
    the spinal (sensory) ganglion, where they enter
    the anterior rami of the spinal nerves. However,
    unlike somatic innervation, they quickly separate
    out through white rami connectors that connect to
    either the paravertebral (which lie near the
    vertebral column) or prevertebral (which lie near
    the aortic bifurcation) ganglia extending
    alongside the spinal column.

10
Synaptic transmission.
  • To reach target organs and glands, the axons must
    travel long distances in the body, and, to
    accomplish this, many axons relay their message
    to a second cell through synaptic transmission.
    The ends of the axons link across a space, the
    synapse, to the dendrites of the second cell. The
    first cell (the presynaptic cell) sends a
    neurotransmitter across the synaptic cleft where
    it activates the second cell (the postsynaptic
    cell). The message is then carried to the final
    destination.

11
Some terms
  • In the SNS and other components of the peripheral
    nervous system, these synapses are made at sites
    called ganglia. The cell that sends its fiber is
    called a preganglionic cell, while the cell whose
    fiber leaves the ganglion is called a
    postganglionic cell. As mentioned previously, the
    preganglionic cells of the SNS are located
    between the first thoracic segment and third
    lumbar segments of the spinal cord.
    Postganglionic cells have their cell bodies in
    the ganglia and send their axons to target organs
    or glands.

12
  • Presynaptic nerves' axons terminate in either the
    paravertebral ganglia or prevertebral ganglia.
    There are four different ways an axon can take
    before reaching its terminal

13
  • The postsynaptic cell then goes on to innervate
    the targeted end effector (i.e. gland, smooth
    muscle, etc.). Because paravertebral and
    prevertebral ganglia are relatively close to the
    spinal cord, presynaptic neurons are generally
    much shorter than their postsynaptic
    counterparts, which must extend throughout the
    body to reach their destinations.
  • The ganglia include not just the sympathetic
    trunks but also the cervical ganglia (superior,
    middle, and inferior), which sends sympathetic
    nerve fibers to the head and thorax organs, and
    the celiac and mesenteric ganglia (which send
    sympathetic fibers to the gut).

14
An exception the adrenal medulla
  • Specialized ganglion of the SNS.
  • Presynaptic neurons pass through paravertebral
    ganglia, on through prevertebral ganglia and then
    synapse directly with suprarenal tissue. This
    tissue consists of cells that have pseudo-neuron
    like qualities in that when activated by the
    presynaptic neuron, they will release their
    neurotransmitter (epinephrine) directly into the
    blood stream.
  • Preganglionic fibers synapse directly on
    chromaffin cells in the adrenal medulla.
  • These chromaffin cells secrete epinephrine and
    norepinephrine into the circulation.

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Mechanism of action.
  • The SNS is designed for a quick immediate and
    massive action and in conjunction with adrenal
    medulla initiate reactions in conditions of
    stress Fight or flight reaction.

17
Mechanism
  • Its effect is mediated by catecholamines through
    three types of receptors
  • epinephrine and norepinephrine are mediated by
    a-receptors and ß-receptors
  • a1-receptors
  • a2-receptors
  • ß1-receptors
  • ß2-receptors
  • dopamine action is mediated through D receptors

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Receptors for catecholamines on different tissues
21
PARASYMPATHETIC NERVOUS SYSTEM (CRANIOSACRAL
SYSTEM)
  • The parasympathetic system is responsible for
    stimulation of "rest-and-digest" or feed and
    breed activities that occur when the body is at
    rest, especially after eating, including sexual
    arousal, salivation, lacrimation, urination,
    digestion, and defecation
  • Its action is described as being complementary to
    the sympathetic nervous system.

22
Location.
  • Parasympathetic nerve fibers arise from the
    central nervous system with the S2, S3, and S4
    spinal nerves and from third, seventh, ninth, and
    tenth cranial nerves. Because of its location,
    the parasympathetic system is commonly referred
    to as having "craniosacral outflow", which stands
    in contrast to the sympathetic nervous system,
    which is said to have "thoracolumbar outflow".
  • The parasympathetic nerves that arise from the
    S2, S3, and S4 spinal nerves are commonly
    referred to as the pelvic splanchnic nerves or
    the "nervi erigentes".

23
Pathways.
  • The main controlling center is present in the
    anterior hypothalamus. The parasympathetic
    nervous system also has
  • 1) Afferent fibers
  • 2) Efferent fibers
  • The afferent fibers are concerned with the
    detection of volume and pressure changes in the
    viscera.
  • The efferent fibers are concerned with
    secretomotor activity of the viscera.

24
Outflow.
  • The outflow has two divisions
  • 1) Cranial division
  • 2) Sacral division

25
Cranial division.
26
  • The preganglionic nerve fibers of these neurons
    synapse in the appropriate ganglia. These ganglia
    are present near the target organ.
  • Postganglionic nerve fibers starts from these
    ganglia and supply to the organ.
  • Preganglionic fibers are longer and the
    postganglionic fibers are shorter.

27
Cranial division.
  • The cranial outflow is through III, VII, IX, and
    X.
  • Occulomotor III
  • Constrictor pupillae
  • Ciliaris
  • Facial VII
  • Lacrimal gland
  • Submaxillary gland and sublingual gland
  • Glossopharyngeal IX
  • Parotid gland
  • Vagus X
  • CVS, RS, GIT, up to transverse colon.

28
SACRAL DIVISION
  • The preganglionic neurons are present in the
    lateral horns of sacral segments (S2, S3, and
    S4).
  • Preganglionic fibers come out through the
    anterior root and form nervi erigentis or pelvic
    nerve.
  • The postganglionic neurons are present in the
    target organ itself.
  • Nervi erigentis supplies the descending colon,
    sigmoid colon, and rectum. It also supplies the
    urinary bladder, erectile tissue of the penis and
    the uterus.

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receptors
  • The parasympathetic nervous system uses chiefly
    acetylcholine (ACh) as its neurotransmitter,
    although peptides (such as cholecystokinin) may
    act on the PSNS as a neurotransmitter.
  • The ACh acts on two types of receptors, the
    muscarnic and nicotinic cholinergic receptors.
  • Most transmissions occur in two stages When
    stimulated, the preganglionic nerve releases ACh
    at the ganglion, which acts on nicotinic
    receptors of postganglionic neurons. The
    postganglionic nerve then releases ACh to
    stimulate the muscarinic receptors of the target
    organ.

31
Nicotinic receptors.
32
Muscarnic receptors.
33
Interaction of the two divisions sns psns.
  • Most of the organs receive dual nerve supply.
    Though the actions of these two systems appear to
    be opposed, they are in-fact complementary.
    Depending on the situation at one moment, the
    sympathetic dominates and the PSNS is inhibited
    and in the next moment, the PSNS dominates and
    the SNS is inhibited.

ANS IS RESPONSIBLE FOR THE BODY HOMEOSTATSIS.
34
ENTERIC NERVOUS SYSTEM.
  • Consists of intramural nerve plexesus
  • (a) myenteric plexus
  • (b) Meissners plexus
  • These are present in the GIT and contain the
    sensory, motor, and interneurons.
  • Their activity is modulated by the sympathetic
    and parasympathetic nerve fibers. Several
    neurotransmitters are associated with this
    system. They influence
  • Smooth muscle peristalsis and villi movements
  • Gland secretion of enzymes, electrolytes, and
    the mucous
  • Blood vessels alter blood flow
  • APUD cells release of various GIT hormones

35
Central control of the autonomic nervous system.
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Disorders of the ans.
  • Autoimmune autonomic gangliopathy
  • Congenital central hypoventilation syndrome
  • Familial dysautonomia
  • Holmes-Adie syndrome
  • Horner syndrome
  • Multiple system atrophy
  • Neurally mediated syncope
  • Orthostatic hypotension
  • Postural tachycardia syndrome
  • Striatonigral degeneration
  • Vasovagal syncope
  • Erectile dysfunction
  • Etc

39
Drugs affecting AUTONOMIC ACTIVITY.
40
References.
  1. https//en.wikipedia.org/wiki/Sympathetic_nervous_
    system
  2. https//en.wikipedia.org/wiki/Parasympathetic_nerv
    ous_system
  3. http//www.nlm.nih.gov/medlineplus/autonomicnervou
    ssystemdisorders.html
  4. http//www.dana.org/news/brainhealth/detail.aspx?i
    d9780
  5. Fundamentals of Medical Physiology 4th Edition
    LPR
  6. BRS Physiology 5th edition - Costanzo
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