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Neurotransmitter ppt

Types of neurotransmitters

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Neurotransmitter ppt

  1. 1. NEUROTRANSMITTERS Dr. LAKSHMI PAVANI P. (PT)
  2. 2.  DEFINITION- Neurotransmitter is a chemical substance that acts as the mediator for the transmission of nerve impulses from one neuron to another neuron through synapse. It a messenger of neurologic information from one cell to another.  HISTORY-Evidence of neurotransmitter was first discovered by an Australian scientist named Otto Loewi in 1921. He dreamt of an experiment, which he did practically and came out with this discovery.
  3. 3. CRITERIA FOR NEUROTANSMITTER Nowadays, many substances are categorized as neurotransmitters. To consider a substance as a neurotransmitter, it should fulfill certain criteria as given below  The substance must be found in a neuron 1. It must be produced by a neuron 2. It must be released by a neuron 3. After release, it must act on a target area and produce some biological effect. 4. After the action it must be inactivated
  4. 4. CLASSIFICATION OF NEUROTANSMITTERS  DEPENDING UPON CHEMICAL NATURE- 1. Amino Acids- The neurotransmitters of this group are involved in fast synaptic transmission and are inhibitory and excitatory in action. Eg. GABA, glycine, glutamate and aspartate. 2. Amines- Amines are the modified amino acids. The neurotransmitters of this group involve in slow synaptic transmission and are inhibitory and excitatory in action. Eg. Noradrenaline, adrenaline, dopamine, serotonin and histamine. 3. Others- the one which do not fit in any of these categories. Eg. Acetyl choline and nitric oxide.
  5. 5. DEPENDING UPON FUNCTION  Excitatory Neurotransmitters:  It is the chemical substance which is responsible for the conduction of impulses from presynaptic neurons to post synaptic neurons.  The neurotransmitter released from the presynaptic axon terminal does not cause development of action potential in the post synaptic neuron.  Rather, it causes some changes in the resting membrane potential- slight depolarization by the opening of sodium channels in the post synaptic membrane and the influx of sodium ions from ECF.  The slight depolarization is called excitatory post synaptic potentials (EPSP).  EPSP in turn causes development of action potential in the initial segment of the axon of the postsynaptic neuron.  The common excitatory neurotransmitters are acetylcholine and noradrenaline.
  6. 6.  Inhibitory Neurotransmitters:  It is the chemical substance which inhibits the conduction of impulses from the presynaptic neuron to the postsynaptic neuron.  When it is released from the presynaptic axon terminal due to the arrival of action potential, it causes opening of potassium channels in the postsynaptic membrane and efflux of potassium ions.  This leads to hyperpolarization which is called inhibitory postsynaptic potentials (IPSP).  When IPSP is developed, the action potential is not generated in the postsynaptic neuron.  The common inhibitory neurotransmitters are gamma amino butyric acid (GABA) and dopamine.
  7. 7. TRANSPORT AND RELEASE OF NEUROTRANSMITTERS  The neurotransmitter is produced in the cell body of the neuron and is transmitted through the axon.  At the axon terminal, the neurotransmitter is stored in small packets called vesicles.  Under the influence of a stimuli, theses vesicles open and release the neurotransmitter into the synaptic cleft.  It binds to specific receptors on the surface of the postsynaptic cell.  The receptor G proteins, protein kinase or ligand- gated receptors.
  8. 8. INACTIVATION OF NEUROTRANSMITTERS  After the execution of the action, neurotransmitter is inactivated by four mechanisms: 1. It diffuses out of the synaptic cleft to the area where it has no action. 2. It is destroyed or disintegrated by specific enzymes 3. It is engulfed and removed by astrocytes 4. It is removed by means of reuptake into the axon terminal.
  9. 9. REUPTAKE OF NEUROTRANSMIITERS Reuptake is a process by which the neurotransmitter is taken back from synaptic cleft into the axon terminal after execution of its action. The reuptake process involves a specific carrier protein for each neurotransmitter.
  10. 10. AMINO ACIDS GROUPS NAME SITE OF SECRITION ACTION Amino acids GABA Cerebral cortex, cerebellum, basal ganglia, spinal cord and retina Inhibitory Amino acids Glycine Forebrain, brainstem, spinal cord and retina Inhibitory Amino acids Glutamate Cerebral cortex, brainstem and cerebellum Excitatory Amino acids Aspartate Cerebellum, spinal cord and retina Excitatory
  11. 11. AMINES GROUPS NAME SITE OF SECRITION ACTION Amines Noradrenalin e Postganglionic adrenergic sympathetic nerve endings, cerebral cortex, hypothalamus, basal ganglia, brainstem and spinal cord Excitatory and Inhibitory Amines Adrenaline Hypothalamus, thalamus and spinal cord Excitatory and Inhibitory Amines Dopamine Basal ganglia, hypothalamus, limbic system, neo cortex, retina and synaptic ganglia. Inhibitory Amines Serotonin Hypothalamus, limbic system, cerebellum, spinal cord, retina, GI tract, lungs and platelets. Inhibitory Amines Histamine Hypothalamus, cerebral cortex, GI tract and mast cells Excitatory
  12. 12. OTHERS GROUPS NAME SITE OF SECRITION ACTIOPN Others Nitric oxide Many parts of CNS, neuromuscular junction and GI tract Excitatory Others Acetylcholi ne Pre ganglionic parasympathetic nerve endings Post ganglionic parasympathetic nerve endings Pre ganglionic sympathetic nerve endings Post ganglionic sympathetic cholinergic nerve endings Neuromuscular junction, cerebral cortex, hypothalamus, basal ganglia, thalamus and retina Excitatory
  13. 13. THANK YOU!

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