Anatomy nervous tissue chap 13


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Anatomy nervous tissue chap 13

  1. 1. The Nervous Tissue - Nervous SystemThe Nervous Tissue - Nervous System  Human nervous system is the most complex system in the body formed by a network of many billion of nerve cell called neuron and all assisted by many more supporting glial cell  Neurons (nerve cell )  long processes respond to environmental change (stimuli)  Glial cell (Neuroglia ) “glue cell”  short processes and support protect neurons  participate in  neural activity  neural nutrition  defence of cell in Central nervous system
  2. 2. Development of nerve tissueDevelopment of nerve tissue Nerve system develop from the outer embryonic layer (ectoderm) 3rd week of human embryonic life
  3. 3. 1. Central nervous system (CNS)  Component: Brain (cerebrum and cerebellum) and Spinal cord  Function : Overall “command center” processing and integrating information  Location: CNS nerve cell bodies are present only in the gray matter 1. Peripheral nervous system (PNS)  Component: nerve (Cranial and spinal) and ganglia  Function: receives and projects information to and from the CNS  Location: found in ganglia and in some sensory region like olfactory mucosa Two Anatomical Divisions of the nervous system
  4. 4. Neuron structure
  5. 5. 1. Cell body (perikaryon)  Trophic center for the entire nerve cell and is receptive to stimuli 2. Dendrites  Many elongated process specialized to receive stimuli from the environment 3. Axon  Single process specialized in generating and conducting nerve impulse to other cell(nerve,muscles gland cell) Synapse: interact with other neurons or nonnerve cells Responsible for the transmission of nerve impulse Contact between neurons and other effector cell by releasing neurotransmitters
  6. 6. Structural classes of neurons : • Anaxonic neurons  no anatomical clues to determine axons from dendrites  functions unknown • Multipolar neuron  multiple dendrites & single axon  most common type • Bipolar neuron  two processes coming off cell body – one dendrite & one axon  only found in eye, ear & nose • Pseudounipolar (Unipolar) neuron  single process coming off cell body, giving rise to dendrites (at one end) & axon (making up rest of process)
  7. 7. 3 Main Types of Neuron 1. Sensory (afferent) involved in the reception of sensory stimuli from the environment and from within the body through presence of receptors transmit sensory information from receptors of PNS towards the CNS  most sensory neurons are unipolar, a few are bipolar 2. Association (interneurons) interpretation of sensory information (information processing); complex (higher order) functions are all multipolar 3.Motor (efferent)  control muscle contraction and glandular secretion (muscles/glands/adipose tissue) all are multipolar
  8. 8. Neuroglia (glial cells) CNS neuroglia: • Astrocytes create supportive framework for neurons create “blood-brain barrier” monitor & regulate interstitial fluid surrounding neurons Metabolic exchanges Origin : neural tube •Oligodendrocytes create myelin sheath around axons of neurons in the CNS, Myelinated axons transmit impulses faster than unmyelinated axons Origin: neural tube
  9. 9. •Microglia “brain macrophages” phagocytize cellular wastes & pathogens Immune-related activity Origin: bone marrow •Ependymal cells  produce, monitor & help circulate CSF (cerebrospinal fluid) Lining of CNS Origin:Neural tube
  10. 10. PNS neuroglia: •Schwann cells (Neurolemmocytes)  surround all axons of neurons in the PNS creating a neurilemma around them. Neurilemma allows for potential regeneration of damaged axons  creates myelin sheath around most axons of PNS Orgin : neural tube Satellite cells  support groups of cell bodies of neurons within ganglia of the PNS
  11. 11. Things to know:Things to know:  The axons of neurons are bundled together to form nerves in the PNS & tracts/pathways in the CNS. Most axons are myelinated so these structures will be part of “white matter  The cell bodies of neurons are clustered together into ganglia in the PNS & nuclei/centers in the CNS. These are unmyelinated structures and will be part of “gray matter” Ganglia
  12. 12. •Most axons of the nervous system are surrounded by a myelin sheath (myelinated axons) •The presence of myelin speeds up the transmission of action potentials along the axon •Myelin will get laid down in segments (internodes) along the axon, leaving unmyelinated gaps known as “nodes of Ranvier” •Regions of the nervous system containing groupings of myelinated axons make up the “white matter” •“gray matter” is mainly comprised of groups of neuron cell bodies, dendrites & synapses (connections between neurons)
  13. 13. Blood brain barrier Fuction : shields the brain from toxic substances in the blood,  supplies brain tissues with nutrients,  filters harmful compounds from the brain back to the bloodstream. Compotents : Capillary endothelium Meninges The skull and the vertebral column protect the CNS Between the bone and nervous tissue are membranes of connective tissue Three layer: 1.Dura mater : outer layer lining of skull 2.Arachnoid mater : contain blood vessel subarachoid space : filled with CSF 3.Pia mater : cover the brain Choroid plexus Fuction : remove water from blood and release it as CSF
  14. 14. Microscopic specimenMicroscopic specimen
  15. 15. Cross section of a nerveCross section of a nerve
  16. 16. Peripheral nerve connective tissuePeripheral nerve connective tissue
  17. 17. Cross section of the spinal cordCross section of the spinal cord
  18. 18. Neuron and neurogliaNeuron and neuroglia
  19. 19. AstrocytesAstrocytes
  20. 20. MicrogliaMicroglia
  21. 21. ependymal cellsependymal cells
  22. 22. GangliaGanglia
  23. 23. Cerebral cortexCerebral cortex
  24. 24. cerebellumcerebellum
  25. 25. Choroid plexusChoroid plexus
  26. 26. the end