nervous system n.
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Nervous system

Nervous system

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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.