Autonomic nervous system & neurotransmitter in psychiatry


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Autonomic nervous system & neurotransmitter in psychiatry

  1. 1. INTRODUCTION:-The organs (the "viscera") ofour body, such as the heart, stomach andintestines, are regulated by a part of thenervous system called the autonomicnervous system (ANS). The ANS is part ofthe peripheral nervous system and itcontrols many organs and muscles withinthe body. In most situations, we areunaware of the workings of the ANSbecause it functions in an involuntary,reflexive manner. For example, we do notnotice when blood vessels change size orwhen our heart beats
  2. 2. The ANS is most important in twosituations: In emergencies that cause stress andrequire us to"fight" or take "flight" (run away)and In nonemergencies that allow us to"rest" and "digest."
  3. 3. The ANS regulates: Muscles in the skin (around hair follicles; smooth muscle) around blood vessels (smooth muscle) in the eye (the iris; smooth muscle) in the stomach, intestines and bladder (smoothmuscle) of the heart (cardiac muscle) Glands The ANS is divided into two parts:1.The sympathetic nervous system2. The parasympathetic nervous
  4. 4. 1. Sympathetic Nervous System:-The sympathetic nervous system originatesin the spinal cord. Specifically, the cell bodiesof the first neuron (the preganglionic neuron)are located in the thoracic and lumbar spinalcord. Axons from these neurons project to achain of ganglia located near the spinal cord.In most cases, this neuron makes a synapsewith another neuron (post-ganglionic neuron)in the ganglion. A few preganglionic neuronsgo to other ganglia outside of the sympatheticchain and synapse there. The post-ganglionicneuron then projects to the "target" - either amuscle or a
  5. 5. 2. Parasympathetic Nervous System:-The cell bodies of theparasympathetic nervous system arelocated in the spinal cord (sacral region)and in the medulla. In the medulla, thecranial nerves III, VII, IX and X form thepreganglionic parasympathetic fibers. Thepreganglionic fiber from the medulla orspinal cord projects to ganglia very closeto the target organ and makes a
  6. 6. AUTONOMIC NERVOUS SYSTEMStructure Sympathetic Stimulation Parasympathetic StimulationIris (eye muscle) Pupil dilation Pupil constrictionSalivary Glands Saliva production reduced Saliva production increasedOral/NasalMucosaMucus production reduced Mucus production increasedHeart Heart rate and force increased Heart rate and force decreasedLung Bronchial muscle relaxed Bronchial muscle contractedStomach Peristalsis reduced Gastric juice secreted; motilityincreasedSmall Intestine Motility reduced Digestion increasedLarge Intestine Motility reduced Secretions and motility increasedLiver Increased conversion ofglycogen to glucoseKidney Decreased urine secretion Increased urine secretionAdrenalmedullaNorepinephrine andepinephrine secretedBladder Wall relaxedSphincter closedWall contractedSphincter
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  8. 8. NEUROTRANSMITTERSDEFINATION:-Neurotransmitters are chemicals located and released inthe brain to allow an impulse from one nerve cell to passto another nerve cell.DESCRIPTION:-There are approximately 50 neurotransmitters identified.There are billions of nerve cells located in the brain, whichdo not directly touch each other. Nerve cells communicatemessages by secreting neurotransmitters.Neurotransmitters can excite or inhibit neurons (nervecells). Some common neurotransmitters areacetylcholine, norepinephrine, dopamine, serotonin andgamma aminobutyric acid (GABA). Acetylcholine andnorepinephrine are excitatory neurotransmitters whiledopamine, serotonin, and GABA are inhibitory. Eachneurotransmitter can directly or indirectly influenceneurons in a specific portion of the brain, thereby
  10. 10. A nerve impulse travels through a nerve in a long, slender cellularstructure called an axon, and it eventually reaches a structurecalled the presynaptic membrane, which containsneurotransmitters to be released in a free space called thesynaptic cleft. Freely flowing neurotransmitter molecules arepicked up by receptors (structures that appear on cellularsurfaces that pick up molecules that fit into them like a "lockand key") locatedNeurotransmitters are chemicals that transmit messages from onenerve cell (neuron) to another. The nerve impulse travels fromthe first nerve cell through the axon—a single smooth bodyarising from the nerve cell— to the axon terminal and thesynaptic knobs. Each synaptic knob communicates with adendrite or cell body of another neuron, and the synaptic knobscontain neurovesicles that store and release neurotransmitters.The synapse lies between the synaptic knob and the next cell.For the impulse to continue traveling across the synapse toreach the next cell, the synaptic knobs release theneurotransmitter into that space, and the next nerve cell isstimulated to pick up the impulse and continue
  11. 11. NEUROTRANSMITTERS IN CNS:-I. Cholinergics :-a) Acetylcholine:-Function:- Acetylcholine are manifold &include sleep, arousal, painperception, modulation & coordination ofmovement, & memory acquisition &retention. Cholinergic mechanisms mayhave some role in certain disorders ofmotor behaviour & memory, such asParkinson’s, Huntington’s, & Alzheimer’sdiseases.
  12. 12. II. Monoamines:-a) Norepinephrine:-Functions:- It include the regulation ofmood, cognition, perception,locomotion, cardiovascularfunctioning, & sleep & arousal. Theactivity of norepinephrine also hasbeen implicated in certain mooddisorders such as depression &mania, in anxiety state &
  13. 13. b) Dopamine:-Functions:- It include regulation of movement &coordination, emotions, voluntary decision-making ability. Increased levels of dopamine areassociated with mania & schizophrenia.c) Serotonin:-Functions:- It may play a role in sleep & arousal,libido, appetite, mood, aggression, & painperception. The serotoninergic system has beenimplicated in the etiology of certainpsychopathological conditions including anxietystates, mood disorders, &
  14. 14. d) Histamine:-The role of histamine inmediating allergic & inflammatoryreactions has been well documented. It’srole in the CNS as a neurotransmitter hasonly recently been confirmed, & theavailability of information is limited. Thehighest concentrations of histamine arefound within various regions of thehypothalamus. The exact processesmediated by histamine with the CNS areuncertain, some data suggest thathistamine may play a role in thedepressive
  15. 15. III. Amino Acids:-a) Gamma-Aminobutyric Acid:-Function:- It prevent postsynapticexcitation, interrupting the progressionof the electrical impulse at the synapticjunction. This function is significant whenslowdown of body activity isadvantageous.Alterations in the GABA systemhave been implicated in the etiology ofanxiety disorders, movement disorders(eg: Huntington’s disease), & variousforms of
  16. 16. b) Glycine:-The highest concentration of glycinein the CNS are found in the spinal cord &brainstem. Glycine appears to be theneurotransmitter of recurrent inhibition ofmotor neurons within the spinal cord, & ispossible involved in the regulation ofspinal & brainstem reflexes. It has beenimplicated in the pathogenesis of certaintypes of spastic disorders & in “glycineencephalopathy”, which is known to occurwith toxic accumulation of theneurotransmitter in the brain &cerebrospinal
  17. 17. c) Glutamate and Aspartate:-Functions:- Glutamate & aspartatefunction in the relay sensory information &in the regulation of various motor & spinalreflexes.-Alteration in this systems has beenimplicated in the etiology of certainneurodegenerative disorder, such asHuntington’s disease, temporal lobeepilepsy, & spinal cerebellar
  18. 18. IV. Neuropeptides:-a.) Opioid Peptides:-Function:- Opioid pepties are thought to have arole in pain modulation, which their naturalmorphine-like properties. They are released inresponse to painful stimuli, & may beresponsible for producing the enalgesic effectfollowing acupuncture.Opioid peptides alter the release of dopamine &affect the spontaneous activity of thedopaminergic neurons. These finding may havesome implication for opioid peptide-dopamineinteraction in the etiology of
  19. 19. b.) Substance P. :-Functions:- It has been found to be highlyconcentrated in sensory fibers, & for thisreason is thought to play a role in sensorytransmission, particularly in the regulationof pain.It has been associated with Huntington’sdisease, dementia of the Alzheimer’s type& mood
  20. 20. c.) Somatostatin:-It (also called growth hormone-inhibiting hormone) is found in the cerebralcortex, hippocampus, thalamus, basalganglia, brainstem, & spinal cord & has multipleeffect on the CNS. It exerts inhibitory effects onthe release of norepinephrine & stimulatoryeffects on serotonine. It stimulates the turnover& release of dopamine in the basal ganglia &acetylcholine in the brainstem & hippocampus.Postmortem examinations have revealed highconcentrations of somatostatin in brainspecimens of clients with Huntington’sdisease, & low concentrations in those withAlzheimer’s
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