1. Nervous System
Hazel Anne L. Tabo

2. Nervous System
Important in transmission of nerve impulses to coordinate the wholistic response coming from the impulse perceived by the body.
Neurotransmitters – chemical messengers that is transmitted between neuronal cells.
In the response: Stimuli  Afferent (sensory) nerve  Center (spinal cord, brain)  Motor (efferent) nerve  Target organ

3. Nervous tissue
Can be organized by anatomical and functional divisions.
Anatomical Divisions:
Central nervous system
Peripheral nervous system
Functional Divisions
Sensory component (impulse towards to CNS)
Motor component (impulse from CNS to effector or target organs)
2.1 – Somatic nervous system
2.2 – Autonomic nervous system (sympathetic and parasympathetic)

4. Anatomical Division Central nervous system (CNS)
Includes Brain and Spinal cord (SC)
Peripheral nervous system (PNS)
Includes nerves outside CNS and associated ganglia.

6. Cells of Nervous Tissue
Neuron structure
a. Neuronal cell body (soma/perikaryon) – contains nucleus, cytoplasmic organelles, inclusions and cytoskeletons.
- Nucleus – aggregates of cell bodies in the CNS (do not confuse it with the nucleus organelle!)
- Ganglion – cell bodies in the PNS
b. Dendrites
c. Axons
Neuroglial cells – supporting cells located in the CNS
Schwann cells – neuroglia-equivalent in the PNS

8. The Neuron Cell Body / Soma / Perikaryon
1) Nucleus – centrally located in the soma of most neurons; euchromatin and dark nucleolus (“owl-eyed nucleus”)
2) Cytoplasmic organelles and inclusions:
Nissl bodies – dark clumps in the cytoplasm made of polysomes and rough ER
Cytoskeletons: neurofilaments (regulates neuronal axon diameter); microtubules (in cytoplasm); microfilaments (in plasma membrane)
Dendrites – receive stimuli (signals) from adjacent sensory cells, axons or other neurons and converted into electrical impulse; abundant mitochondria.
Axons – conduct impulses away from the soma and sends it to effector/target organs or adjacent nervous tissue.
Axon hillock – specialized area of soma with high neurofilaments
Axoplasm (axon cytoplasm) – contains sER, rER and long mitochondria
Axolemma – plasma membrane of axon
Axon terminals – ends of axon

11. Electrical Impulse runs through:
Synapse are functional sites where electrical signals are transmitted from 1 neuron to another or to another target cell (myofiber).
Dendritic spines increase surface area for synapse formation with other neurons
Terminal buttons – structure in the ends of axon terminal; form synapse to another cell or dendrite.

12. Example of a neuron: Multipolar neuron

13. Types of Neuron Unipolar – one dendrite Bipolar – two dendrites
Multipolar – multiple dendrites
Pseudounipolar – looks like multipolar but unipolar
Functional types – responds to chemical transmitters (neurotransmitter)
Excitatory neuron
Inhibitory neuron
Neurotransmitters – chemical messengers that may promote or inhibit a certain neural response (impulse).
Ex: Acetylcholine – presents in the myoneural junctions (neuromuscular junctions).
Dopamine, Serotonin, GABA

14. Neuroglial cells Supporting cells of CNS
Small-sized and numerous than neuron; origin: neural crest cells
Support, nourishes and protect neurons
Types: astrocytes, oligodendrocytes, microglia, ependymal cells, Schwann cells

15. Astrocytes – largest neuroglial cell; contain many processes forming pedicels (vascular feet) around a blood capillary forming the “blood-brain barrier”; scavenges ion and debris from neuron metabolism and supplies energy for metabolism; support and protects nervous tissue; forms “scar tissue” after injury to CNS.

16. Oligodendrocytes – have small, round, condensed nucleus that lives symbiotically with neurons; necessary for neuron survival; produces myelin in CNS; present in CNS gray and white matter.

17. Microglia – small, phagocytotic neuroglial cell that arised from monocytes in the bone marrow; they become APCs (antigen-presenting cell) in the CNS tissue when activated by trapped foreign bodies.

18. Ependymal cells – epithelial cells that line the neural tube and ventricles of the brain; they have cilia that aids in moving the CSF (cerebrospinal fluid); cells of the choroid plexus (CSF production)

19. Schwann cells – the only neuroglial cell-equivalent in the PNS; function is similar with oligodendrocytes to produce myelin, the myelin sheath consists of several Schwann cell plasmalemma.
Myelinated nerve fibers – faster impulse conduction
Unmyelinated fibers – slower conduction

20. Schwann cell – triangles
Axon - arrows

21. Peripheral Nervous System
Branches from the spinal cord
Spinal nerves, Ganglion, peripheral nerves
Nerve fiber – individual axons enveloped by myelin sheath
Myelin sheath – insulator of heat, myelinated fibers have higher firing rate, than unmyelinated fibers. It is interrupted by nodes of Ranvier (saltatory conduction) along an axon, these gaps are produced by adjacent Schwann cells.
Nerves – bundles of nerve fibers; appear whitish due to (+) myelin; CT wrappings
Ganglia – encapsulated aggregations of soma or cell bodies

22. Peripheral Nervous System

23. Connective tissue wrappings of Peripheral Nerve
Epineurium – covers the whole nerve bundle that forms external coat of nerves formed by dense CT(fascia).
Perineurium – surrounds each nerve bundle (fascicle); flattened cells are joined by tight junctions (z. occludens) prohibiting passage of macromolecules.
Endoneurium – forms a thin layer of reticular fibers produced by Schwann cells that surrounds individual nerve fibers (neurofiber).

25. Central Nervous System
Brain and Spinal Cord
Matter: Gray Matter and White Matter
Gray Matter (GM) – neuronal cell bodies (nucleus), more neuroglial cells and many unmyelinated fibers
White Matter – mostly myelinated fibers and some neuroglial cells
Brain GM – cortex; WM – medulla
Spinal cord WM – cortex; GM – medulla (H-section)

26. Brain, Frontal section

27. Spinal cord section

28. Meninges Dura mater – connected to the endosteum of the skull
Arachnoid mater – sublayer between periosteum and brain, contains network (cobweb) of blood vessels.
Pia mater – covers the brain parenchyma

31. Skin Sensory Receptors
Merkel’s disks – free nerve endings (unencapsulated), unmyelinated nerve fibers (skin: stratum basale)
Meissner’s corpuscle – sensitive to light touch (skin dermis)
Pacinian corpuscle – deep pressure or coarse touch (skin dermis)
End bulb of Krause – sensitive to cold (oropharynx lining & eye conjunctiva)
Ruffinian corpuscle – sensitive to heat (soles of feet)

32. Da Lamarcke’s theory of use and disuse can be associated with microcephaly. Such condition may happen if you don’t exercise your brain!

33. THANK YOU FOR LISTENING!