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Nervous system

Nervous system. Nervous system. CNS. PNS. P. e. r. i. p. h. e. r. a. l. N. e. r. v. o. u. s. S. y. s. t. e. m. S. k. e. l. e. t. a. l. A. u. t. o. n. o. m. i. c. (. S. o. m. a. t. i. c. ). S. y. m. p. a. t. h. e. t. i. c. P. a. r.

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Nervous system

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  1. Nervous system

  2. Nervous system CNS PNS

  3. P e r i p h e r a l N e r v o u s S y s t e m S k e l e t a l A u t o n o m i c ( S o m a t i c ) S y m p a t h e t i c P a r a s y m p a t h e t i c Peripheral Nervous System

  4. Peripheral nervous system • Sensory (Afferent) : conveys information to the CNS from the sensory receptors (specific neurons or groups of neurons) • Motor (efferent) division: conveys information away from the CNS • Somatic (voluntary) nervous system: neurons go to skeletal muscle • Autonomic (involuntary): neurons go to smooth,cardiac muscle and all glands.

  5. Autonomic nervous system Parasympathetic Sympathetic “ Fight or flight” response Release adrenaline and noradrenaline Increases heart rate and blood pressure Increases blood flow to skeletal muscles Inhibits digestive functions • “ Rest and digest ” system • Calms body to conserve and maintain energy • Lowers heartbeat, breathing rate, blood pressure

  6. Nervous tissue cells • Neurons: respond to stimuli and conduct impulses • Supporting cells (or neuroglia) : support, nourish, repair and protect neurons.

  7. Neuron • Cell body: central part of neuron which contains nucleus, and the sorrounding cytoplasm, exclusive of cell processes. • Responsible for nutrition, growth, and repair of neuron

  8. Nucleus • It contains DNA and the nucleus also contains nucleolus which in turn is made of RNA.

  9. Nissle bodies: rough endoplasmic reticulum • Dendrites : Conduct incoming messages toward cell body • Axon: conducts nerve impulses away from cell body. • Axon hillock : portion of cell body from where axon originates.

  10. Neuron classification • By structure : • Multi-polar neuron • Bipolar neuron • Pseudounipolar neuron • By function: • Sensory (afferent) neurons • Motor (efferent) neurons • Association (Interneurons) neurons

  11. Multi-polar neuron: one axon and many dendrites • Multipolar neurons constitute the majority of neurons in the brain and include motor neurones

  12. Bipolar neuron: two processes: one axon and one dendrite • Bipolar cells are specialized sensory neurons for the transmission of special senses. • As such, they are part of the sensory pathways for smell, sight, taste, hearing and vestibular functions. • Pseudounipolar neuron: single process comes off to the cell body and divides into two branches • The cell bodies are located in the dorsal root ganglion.

  13. Neuron classification • Sensory (afferent) neurons : bring information to the CNS • Motor (efferent) neurons : take information from CNS to the other parts of the body • Association (Interneurons) neurons : allows for communication between neurons within CNS

  14. Supporting cells The following are present in CNS • Microglia : ingests damaged neurons and foreign substances. Microglia are a type of glial cells that are the resident macrophages • Astrocytes • Oligodendrocytes : Myelinate axons in CNS. Speeds up conduction • Ependymal cells : lines central canal and ventricles – help circulate CSF

  15. Astrocytes • Astrocytes: regulates transfer of nutrients from blod to the brain;helps form a part of blood brain barrier. • Astrocytes (also known collectively as astroglia) are characteristic star-shaped glial cells in the brain and spinal cord

  16. Supporting cells in CNS

  17. Supporting cells • Satellite cells : sorround neuron cell bodies in spinal ganglia. {Ganglion : group of neuron cell bodies located outside CNS}. They supply nutrients to the surrounding neurons , protects, cushioning of cells. • Schwann Cells : myelinate axons in PNS

  18. Myelination of Axon • Myelination = process of wrapping an axon with myelin,which speeds up conduction • One schwann cells wrap around a portion of an axon successively • Cytoplasm and nucleus of schwann cells gets squeezed to the periphery

  19. Myelination of Axon • Inner successive layers of myelin sheath are the cell membrane of the schaawn cells • Schwann cells don’t contact each other. They are seperated by nodes of ranvier. • This allows for the electric impulses to skip along the axon,calledsaltatory conduction

  20. Myelination in CNS is the same as PNS but one oligodendrocyte myelinates portions of many axons.

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