Histology of Nervous System 11st yr.pptx

Histology Nervous

1. Histology of Nervous System Anatomical Division: 1. Central Nervous System: Brain & Spinal Cord. 2. Peripheral Nervous System: Axons, Spinal Nerves, Cranial Nerves & Ganglia

2. Nervous Tissue Functions Receive/Analyze/Integrate-External & Internal Stimuli Response in Effector Organs; As Muscles, Glands etc….

3. 4 Nervous Tissue Controls and integrates all body activities within limits that maintain life Three basic functions sensing changes with sensory receptors interpreting and remembering those changes reacting to those changes with effectors

4. 5 Major Structures of the Nervous System Brain spinal cord cranial nerves spinal nerves ganglia enteric plexuses sensory receptors

5. Subdivisions of the PNS Central nervous system (CNS) Peripheral nervous system (PNS ): Divided into: A. Sensory (Afferent) component which receives and transmits impulses to CNS and B. Motor (Efferent) component which transmits orders to target organs. This motor component is further divided into : Somatic (voluntary) nervous system (SNS ) impulses sent to muscles via a single neuron. Autonomic (involuntary) nervous systems (ANS ): Impulses here sent via a single neuron to a Ganglia then a second order neuron send impulses to effector organs; Smooth, Cardiac muscles or Glands.

6. 7 Organization of the Nervous System CNS is brain and spinal cord PNS is everything else

7. 8 Organization Integration Motor Sensory SNS (Sensory) ANS (Sensory) Brain Spinal cord SNS (Motor) ANS (Motor) ENS (Sensory)

8. 9 Gray and White Matter White matter = myelinated processes (white in color ) (Inner in Brain) Gray matter = nerve cell bodies, dendrites, axon terminals, unmyelinated axons and neuroglia (gray color ) (Outer in Brain)

9. Neurons: Functional unit of nervous system 1. Nucleus and prominent nucleolus. Cell body: Soma/ Perikaryon Nissl bodies/RER Neurofilaments (Intermediate Filament) Mitochondria & Microtubules Lipofuscin pigment clumps; Residual lysosomal activity. Melanin pigment: Precursor of neurotransmitter methyldopa Cell processes Dendrites Axons

10. 1. 1. Two Subpopulation of Human Purkinje Neurons; An Electron Microscopy Study. Qasim A. El- Dwairi . Neuroendocrinology Letters in Vol. 28 No.3, June 2007. 2. Zaqout SI, Alhussain SM, Al Saffar R and Qasim El Dwairi (2012). A Golgi study of the camael cuneate nucleus. The Anatomical Record. 295: 2191-2204. 3. Deviation of the fully protracted tongue: is it a reliable indicator for language cerebral dominance? Abu Ghaida J, Hani SB, Mustafa A, Eldwairi Q. Med Hypotheses. 2014 Sep;83(3):270-2. doi : 10.1016/j.mehy.2014.05.014. Epub 2014 Jun 9. 4. A New Approach for GenCos Profit Based Unit Commitment in Day- Ahead Competitive Electricity Markets Considering Reserve Uncertaininty . Y.Y Yamin , Q. El- Dwairi and S. M. Shahidehpour . International Journal of Electrical Power & Energy Systems 29(2007) 609-616.

11. 13 Parts of a Neuron Nucleus with Nucleolus Axons or Dendrites Cell body Neuroglial cells

12. 14 Structural Classification of Neurons Based on number of processes found on cell body multipolar = several dendrites & one axon most common type (Motor) bipolar neurons = one main dendrite & one axon found in retina, inner ear & olfactory unipolar neurons = one process only(develops from a bipolar) are always sensory neurons

13. 15 Structural Classification of Neurons Based on number of processes found on cell body multipolar = several dendrites & one axon most common type (Motor) bipolar neurons = one main dendrite & one axon found in retina, inner ear & olfactory unipolar neurons = one process only(develops from a bipolar) are always sensory neurons

14. 16 Structural Classification of Neurons Based on number of processes found on cell body multipolar = several dendrites & one axon most common type (Motor) bipolar neurons = one main dendrite & one axon found in retina, inner ear & olfactory unipolar neurons = one process only(develops from a bipolar) are always sensory neurons

15. 17 Association or Interneurons transmit information between Sensory and Motor neurons within the CNS; analyze inputs, coordinate outputs are the most common type of neuron ( 20 billion ) are all multipolar

16. 18 Dendrites Conducts impulses towards the cell body Typically short, highly branched & unmyelinated Surfaces specialized for contact with other neurons Contains all organelles EXCEPT Nucleus and Golgi. impulse

17. Dendrite - cell process extending away from the perikaryon 3. has tiny rough projectons or spines called gemmules or dendritic spines that are points of synaptic contact 4. dendrites from larger neurons may be lightly myelinated by oligodendroglia 5 . Cytoplasm in these processes similar to that of perikaryon , but no Golgi bodies . 2. forms receptive area for synaptic contacts from other neurons

18. 20 Axons Conduct impulses away from cell body Long, thin cylindrical process of cell Arises at axon hillock Impulses arise from initial segment ( trigger zone ) Side branches ( collaterals ) end in fine processes called axon terminals Swollen tips called synaptic end bulbs contain vesicles filled with neurotransmitters. Contain lots of Mitochondria

19. Axon Single extension from Cell Body at Axon Hillock. Site of Action Potential Trigger Zone . No RER, has Neurofilament and Microtubules. Abundant Mitochondria at Axon Terminal (Terminal button) that end at membrane of effector organs (Neuromuscular junction) 21

20. 23 Neuroglial Cells Half of the volume of the CNS Smaller cells than neurons 50X more numerous Cells can divide rapid mitosis in tumor formation (gliomas) 4 cell types in CNS astrocytes, oligodendrocytes, microglia & ependymal 2 cell types in PNS schwann and satellite cells

21. 24 Neuroglial Cells (CNS): Astrocytes Star-shaped cells Form blood-brain barrier In the brain, processes abut against the basement membrane of capillary endothelium (pedicles) forming the blood-brain barrier Metabolize neurotransmitters Provide structural support

22. 25 Neuroglial Cells (CNS): Oligodendrocytes Most common glial cell type Each forms myelin sheath around more than one axons in CNS Analogous to Schwann cells of PNS

23. 26 Neuroglial Cells (CNS): Microglia Small cells found near blood vessels Phagocytic role -- clear away dead cells Derived from cells that also gave rise to macrophages & monocytes

24. 27 Neuroglial Cells (CNS): Ependymal cells Form epithelial membrane lining cerebral cavities & central canal Produce cerebrospinal fluid (CSF)

25. 28 Neuroglial Cells (PNS): Satellite Cells Flat cells surrounding neuronal cell bodies in peripheral ganglia Support neurons in the PNS ganglia

26. 29 Neuroglial Cells (PNS): Schwann Cell Cells encircling PNS axons Each cell produces part of the myelin sheath surrounding an axon in the PNS

27. 30 Myelination Insulation of axon Increase speed of nerve impulse

28. 31 Myelination: PNS All axons surrounded by a lipid & protein covering ( myelin sheath ) produced by Schwann cells Neurilemma is cytoplasm & nucleus of Schwann cell gaps called nodes of Ranvier Myelinated fibers Unmyelinated fibers Node of Ranvier

29. 32 Myelination: PNS Schwann cells myelinate (wrap around) axons in the PNS during fetal development Schwann cell cytoplasm & nucleus forms outermost layer of neurolemma with inner portion being the myelin sheath Tube guides growing axons that are repairing themselves

30. 33 Myelination: CNS Oligodendrocytes myelinate axons in the CNS Broad, flat cell processes wrap about CNS axons, but the cell bodies do not surround the axons No neurilemma is formed Little regrowth after injury is possible due to the lack of a distinct tube or neurilemma

31. Myelination Process

32. Axonal Transport Axonal transport of materials between the Soma And The Axon terminals . In antero grade transport, the direction is form the cell body to the axon terminal. It is Fast Retrograde transport the direction is from the Axon Terminal To The Cell Body . It is Slow Anterograde transport is used in the translocation of Organelles And Vesicles, Macromolecules such as Actin and Myosin Retrograde transport include protein building blocks of Neurofilaments Subunits Of Microtubules soluble enzymes and materials taken up by endocytosis ( e.g Viruses And Toxins ) Clinical Correlations retrograde axonal transport is used by certain viruses as Herpes simplex and Rabies and Toxins As Tetanus to spread from one neuron to the other.

33. 36 Continuous versus Saltatory Conduction Continuous conduction (unmyelinated fibers) Saltatory conduction (myelinated fibers) A.P. Na Na Na Na Na Na Na Na Na Na

34. 37 Saltatory Conduction Nerve impulse conduction in which the impulse jumps (Salta) from node to node A.P. Na Na Na Na Na

35. Axon (Peripheral Nerve) Peripheral nerves contain a considerable amount of connective tissue. The entire nerve is surrounded by a thick layer of dense connective tissue, the Epineurium . Nerve fibres are frequently grouped into distinct Bundles, Fascicles , within the nerve. The layer of connective tissue surrounding the individual bundles is called Perineurium . The perineurium is formed by several layers of flattened cells, which maintain the appropriate microenvironment for the nerve fibres surrounded by them. The space between individual nerve fibres is filled by loose connective tissue, the Endoneurium . 38

36. Axons 39

37. Anatomical structure of Nerves epineurium extending between fascicles nerve fibers

38. Ganglia Ganglia Are Masses Of Neuronal Somas, Usually Defined As Being Outside The Central Nervous System. They Seem To Act As Coordinating Way Stations. Two type Ganglia: 1. Sensory. 2. Autonomic 41

39. Anatomy of Autonomic (Involuntary) Motor Pathways In Somatic System One Neuron in CNS connected to effector Organ) ANS Posses 2-Neurons between CNS & Effector Organ i.e : 1. Preganglionic neuron: Lie in CNS, axons Synapse with Multipolar Neuron that is PGN (Acetylcholine) 2. Postganglionic neuron (PGN): Fibers Connect To Effector Organ (Cardiac, Smooth Muscles & Glands. (Norepinephrine) Two divisions: Sympathetic: Prepare Body ((Flight or Fight)) Parasympathetic: Opposite Function ((Rest or Digest)) 42

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42. Sympathetic Ganglia Sympathetic Ganglia are the ganglia of the sympathetic nervous system. They deliver information to the body about stress and impending danger, and are responsible for the familiar Fight-or-flight Response . They contain approximately 20,000–30,000 nerve cell bodies and are Located Close To And On Either Side Of The Spinal Cord In Long Chains. Sympathetic ganglia are the tissue from which neuroblastoma tumours arise. 45

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44. Sensory Ganglia Made of Sensory Neurons (Unipolar). Associated with Special senses i.e V, VII, IX and X Cranial Nerves. Forms a Swelling within the nerve inside or Outside the Skull. Called Dorsal Root Ganglia surrounded by a capsule Connections: Peripheral processes with receptors to transduce stimuli to the neurons Central connection to the brain/Spinal cord within cranial or spinal nerves 47

45. Autonomic Ganglia Have Neurons of postganglionic Autonomic nerves. Motor in Functions causing Glandular Secretions or Smooth and Cardiac Muscles contraction 48

46. Spinal/Sympathetic Ganglia Spinal Ganglia Cell bodies Lie on posterior Nerve Root of Spinal Cord. Have Sensory Neurons (Unipolar). Closely packed Sympathetic Ganglia Multipolar Type: Hence Many Dendrites Hence Widely Apart. 49

47. 50 Regeneration & Repair Plasticity maintained throughout life sprouting of new dendrites synthesis of new proteins changes in synaptic contacts with other neurons Limited ability for regeneration (repair) PNS can repair damaged dendrites or axons CNS no repairs are possible