The presentation on the functional unit of nervous system-Neurones.pptx

Presentation

1. Cells and tissues of the nervous system 1

2. Classification of the Nervous System

3. Neurons The entire nervous system is made up of Neurons (Functional units) Each neuron consist of a cell body and its processes, one axon and many dendrites. Bundles of axons bound together = Nerves 3

4. Neurons generate and transmit electrical impulses called action potential . Some neurons initiate nerve impulses while others act as ‘relay stations’ where impulses are passed on. Transmission of nerve signals is both electrical and chemical . 4

5. Neuron Cell body Axons and dendrites Cell body : Cell bodies form the grey matter of the nervous system. Grey matter is found at the periphery of the brain and in the centre of the spinal cord. Groups of cell bodies in CNS = nuclei Group of cell bodies in PNS = ganglia Important exception: basal ganglia is situated within cerebrum 5

6. Axons and dendrites are extensions of cell bodies and form the white matter of nervous system. Within the brain, groups of axon = tracts Groups of axon outside brain and spinal cord are called nerves or nerve fibres . Each nerve cell has only one axon which begins from an area called axon hillock. 6

7. Structure of Axon 7

8. Action potential Node or Ranvier Schwann cell a. Non- myelinated neuron, b. Myelinated neuron 8

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11. After an action potential arrives at an axon terminal and calcium ions enter the cell, synaptic vessicles fuse with the presynaptic membrane. 11

12. Neurotransmitter molecules are released and bind to on the postsynaptic membrane. 12

13. When a stimulatory neurotransmitter binds to a receptor, Na + diffuses into the postsynaptic neuron. 13

14. Nerves Within brain and spinal cord (CNS) = Tracts Outside CNS = Nerves or nerve fibres A nerve consists of numerous neurones collected into bundles and each bundle has several coverings of protective connective tissue. Endoneurium Perineurium Epineurium 14

15. Transverse section of a peripheral nerve showing the protective covering 15

16. Sensory or Afferent nerves They carry information from the body to the spinal cord and the brain. Sensory receptors: They respond to changes inside & outside the body. Somatic, cutaneous or common senses Propriorceptor senses Special senses Autonomic afferent nerves. Originate from internal organs, glands & tissues. e.g. baroreceptors & chemoreceptors 16

17. Motor or efferent nerves Originate from the brain, spinal cord and the autonomic ganglia and transmit impulses to the effector organs. There are two types: Somatic nerves Autonomic nerves (sympathetic and parasympathetic) 17

18. Neuroglia Neurons of CNS is supported by four non-excitable glial cells which continue to replicate throughout life. Astrocytes – constitute the BBB Oligodendrocytes Ependymal cells Microglia – derived from monocytes 18