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Introduction to cns


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Introduction to cns

  2. 2. We will study Classification of nervous system. Neuron and its details. Details of synapse. Classification of neurons. Composition of nervous system. Receptors and their details.
  3. 3. Classification of CNSMade up of grey & white matter Classification Anatomical Functional l Central Peripheral Autonomic Somatic Brain Nerves Involuntary Voluntary Spinal cord Cranial nerves Spinal nerves Ganglion Sympathetic Parasympathetic Dorsal Root.Gang
  4. 4. Classification of CNS
  5. 5. Neuron Basic structural & functional unit of the nervous system PARTS OF A NEURON SOMA OR PROCESSES CELL BODYCell membrane Neuroplasm Axons Dendrites Carry impulses Carry impulses Central nucleus Nissel bodies Away from Towards the Cell body Cell body Neurofibrils Mitochondria Golgi apparatus Axon hillock
  6. 6. NeuronBasic structural & functional unit of the nervous system
  7. 7. NeuronBasic structural & functional unit of the nervous system
  8. 8. NeuronBasic structural & functional unit of the nervous system
  9. 9. A B C DE F G H
  10. 10. Structure of neuron A  Dendrite B  Soma C  Node of Ranvier D  Axon terminal E  Nucleus F  Axon G  Myelin sheath-Faster conduction.-High insulation. H  Schwann cell are responsible for myelination in PNS. They are absent in CNS.
  11. 11. Impulse transmission
  13. 13. Wave of depolarization causesrelease of neurotransmitter Depolarization of Presynaptic terminal Opening of calcium Channels in the membrane Ca2 influx into Presynaptic neuron Ca2 binds to release site On inside of cell membrane Transmitter vesicles fuses With the release site Exocytosis& Neurotransmitter released
  14. 14. Action of neurotransmitter onpostsynaptic membrane (function ofreceptor proteins) Receptor proteins of Postsynaptic membrane An Ionophore component A binding component (passes all the way through (Protrude outward from Membrane into interior of Membrane into cleft) Postsynaptic neuron) Second messenger Ion channel activator
  15. 15. Ion Channels Ion channels of Postsynaptic membrane Cation channels Anion channels (Lined with negativity) (Lined with positivity)Conduct Na ions Conduct Cl ions Opened by excitatory Opened by inhibitory neurotransmitter neurotransmitter
  16. 16. Second messenger system 2nd messenger system G protein Attached to interior of receptor protein Alpha Beta Gamma component component component The activator
  17. 17. Second messenger system Nerve impulse causes Neurotransmitter release Activation of G-protein Associated receptor Alpha portion separates From other components Opening of specific Activation of Ion channel cAMP Activation of Activation of gene Intracellular enzyme transcription
  18. 18. Second messenger system
  19. 19. Receptors of postsynapticmembrane Postsynaptic receptors Excitatory Inhibitory Opening of Opening of Na channels Cl channelsDecrease conduction Increase conduction of Through Cl or K K ions channels Increase in numbers of Increase in number of excitatory Or dec in Inhibitory or dec in inhibitory receptors Excitatory receptors
  20. 20. Chemical substances that functionas synaptic transmitters Synaptic transmitters Rapidly acting Slowly acting (Small molecule) Class I Class II Class III Class IV
  21. 21. Small molecule, rapidly actingtransmitters
  22. 22. Neuropeptide, slowly actingtransmitters
  23. 23. Acetylcholine Terminals of large pyramidal cells from the motor cortex. Neurons in the basal ganglia Motor neurons that innervate skeletal muscle Preganglionic neurons of ANS. Post ganglionic neurons of sympathetic nervous system.
  24. 24. Norepinephrine Widespread areas of brain. Locus ceruleus in the pons. Post ganglionic neurons of sympathetic nervous system.
  25. 25. Dopamine In substantia nigra. In the strial region of basal ganglia Action is usually inhibitory.
  26. 26. GABA Inhibitory neurotransmitter. Secreted in nerve terminals in -cerebellum -spinal cord -basal ganglia -many areas of cerebral cortex
  27. 27. Glutamate Excitatory neurotransmitter. Secreted in -presynaptic nerve terminal of sensory pathways entering CNS -many areas of cerebral cortex.
  28. 28. Classification of neurons Basis of Classification On the basis On the basis On the basis of Of poles Of function Length of axonUnipolar Motor Sensory Golgi typeI Golgi typeII Bipolar neurons neurons Long axon Short axonMultipolar
  29. 29. Classification of neurons -Unipolar neurons, Single pole for axons & dendrites Mesencephalic nucleus of V cranial nerve. A  BIPOLAR Two poles, one for axons, one for dendrites. Retina, inner ear Olfactory mucosa. B  MULTIPOLAR Multi poles, one for axons, other for dendrites. Most neurons of CNS
  30. 30. Classification of neurons A  BIPOLAR Two poles, one for axons, one for dendrites. Retina, inner ear Olfactory mucosa. B  MULTIPOLAR Multi poles, one for axons, other for dendrites. Most neurons of CNS.
  31. 31. Composition of CNS:In cereberal cortex and cerebellum, grey matter is outside & whitematter is inside.In spinal cord, grey matter is inside & white matter is outside. CNS -Neurons and -Supporting cells neuroglia GREY White Matter Matter Nerve cell bodies Nerve fibers Embeded in Axons, neuroglia neuroglia -White-myelin sheath
  32. 32. NEUROGLIA-Non excitable cells forming interstitialsupporting tissues of CNS. They are present in both grey & white matter. NEUROGLIA -Support -Insulation Astrocytes Oligodendrocytes Microglia Ependyma Formation Myelination in Formation of of blood Phagocytosis CNS CSF Brain barrier
  33. 33. Sensory receptors Sensory Receptors s Mechanoreceptors Thermoreceptors Electromagnetic Nociceptors receptors Chemoreceptors
  34. 34. LABELED LINE PRINCIPLE Each of principal type of sensation that we can experience- pain, touch, sight, sound, and so forth is called a modality of sensation. The specificity of nerve fibers for transmitting only one modality of sensation is called the labeled line principle.
  35. 35. Classification of receptors
  36. 36. Classification of receptors
  37. 37. Classification of receptors
  38. 38. PACINIAN CORPUSCLEDeeply located receptorse.g Periosteum, ligaments & joint capsulesCarry light touch, pressure & vibration sensations
  39. 39. Free nerve endingsPresent superficially in the Epidermis & dermis Carry touch, pain & Temperature sensations
  40. 40. Golgi tendon organPresent in the muscle tendonsCarry information related to Muscle contractions& Proprioceptions.
  41. 41. Muscle spindlesPresent in belly of the muscle Related to stretch reflex & Proprioception
  42. 42. Meissner’s corpusclesPresent superficially in fingers, lips Nipples & external genitalia Carry fine touch sensations
  43. 43. Tactile hair Present on skin Carry touch, pressure,Vibration & pain sensations
  44. 44. Properties of receptors Receptors propertiesModality of Receptor Receptor receptors potential adaptation
  45. 45. Modality of receptors Modality of receptors Each type of Receptor is sensitive To each type of stimulus Pain Touch Sight Sound
  46. 46. Receptor potential Effect of application of stimulus is to change the potential across receptor membrane, this change is called receptor potential. Mechanisms Mechanical Application Change in temp Effects of deformation Of chemical Of membrane electromagneticsStretch of receptor Opening of Alters the memb. Light on membrane Ion channel permeability Visual receptors Opening of Ion flow across Ion channel membrane
  47. 47. Action potential of paciniancorpuscle
  48. 48. Receptor potential & action potentialwhen receptor potential rises above the threshold for eliciting actionpotential.
  49. 49. Stimulus intensity & receptorpotential
  50. 50. Adaptation of receptorsWhen a stimulus is continuously applied, receptors becomes less sensitive to thestimulus and ignore it, this is called adaptation. Receptors Adaptation Slowly adapting Rapidly adapting receptors receptors Detect continuous Detect change in Stimulus strength Stimulus strength Recp In vestibular Pain receptors Pacinian corpuscle apparatus Barroreceptors of Chemoreceptors of Arterial tree Carotid & aortic bodies
  51. 51. Adaptation of receptors