INTRODUCTION TO NERVOUS SYSTEM

2. Introduction to Nervous System.
General Functional Organization of Nervous System.
Neuron as a functional unit of Nervous System.
Neuroglial Cells.
Blood Brain Barrier.

4. A. Sensory receptors at the ends of peripheral nerves gather
information and convert it into nerve impulses.
B. When sensory impulses are integrated in the brain as
perceptions, this is the integrative function of the nervous
system.
C. Conscious or subconscious decisions follow, leading to
motor functions via effectors.

6.  Neurons are the cells responsible for receiving
sensory input from the external world, for sending
motor commands to our muscles or glands, and for
transforming and relaying the electrical signals at
every step in between.

9.  The neuroglia are a diverse class of cells
that provide developmental, physiological
and mental support for neurons. They are
responsible for maintaining homeostatic
control and immune surveillance in the
nervous system.
 There are two types of neuroglial cells in
peripheral nervous system.
 Schwann cells and Satellite cells

10. 1. Schwann cells: (Neurolemmocytes)
Which forms myelin sheaths around
peripheral axons.
Schwann cells respond quickly to injury and
aid axon regeneration. Schwann cells are
associated with a number of demyelinating
disorders, infected during leprosy and are
responsible for the tumors in both
neurofibromatosis type 1 and type 2.

11. 2. Satellite cells: glial cells that
surround some neurons in the
P.N.S.
They provide nutrient support and
protection. They may also help to
regulate the neuronal environment
and be involved in
neurotransmission.

12. There are four types of neuroglial cells in
peripheral nervous system.
1. Oligodendrocytes:
Which forms myelin sheaths around axons of
C.N.S.
They are the end product of a cell lineage
which has to undergo a complex and precisely
timed program of proliferation, migration,
differentiation, and myelination to finally
produce the insulating sheath of axons.

13. 2. Microglia: These cells are
located throughout the Brain and
Spinal Cord. Microglia account 10-
15% of all cells found in the brain.
They act as the First and main
form of active immune defence in
the C.N.S.

14. 3. Astrocytes: Astrocytes are the most
numerous cell type within the C.N.S.
and perform a variety of tasks, from
axon guidance and synaptic support,
to the control of the blood brain
barrier and blood flow. To perform
these roles, there is a great variety of
astrocytes.

15. 4. Ependymal Cells: Which are
epithelial cells that lines the Ventricles
of the brain and central canal of the
spinal cord.
Contributes to the formation of
Cerebrospinal Fluid (C.S.F).
Cilia Assist in circulation of C.S.F.

17.  Blood Brain Barrier is a highly Selective Semipermeable
border of endothelial cells that prevents solutes in the
circulating blood from non selective crossing into
extracellular fluid of the C.N.S.
 B.B.B. allows these vessels to tightly regulate the movement
of ions, molecules, and cells between the Blood and the
Brain.