nervous system p.1

The nervous system
The nervous system can be organized by anatomical or functional divisions.
A. Nervous system is divided anatomically into the central nervous system (CNS), which includes the brain and spinal cord, and the peripheral nervous system (PNS), which includes the nerves outside the CNS and their associated ganglia.
B. Nervous system is divided functionally into a sensory component, which transmits electrical impulses (signals) to the CNS, and a motor component, which transmits impulses from the CNS to various structures of the body. The motor component is further divided into the
somatic and autonomic systems.
C. Nervous tissue contains two types of cells: nerve cells (neurons), which conduct electrical impulses, and glial (neuroglial) cells, which support, nurture, and protect the neurons.
Supporting cells of the CNS (neuroglia cells) :
1-Oligodenderocytes present in white and gray matter.
2-Astrocytes stellate morphology.
3-Ependymal cells line ventricles .
4-Microglia highly phagocytic cells.
Supporting cells of the PNS. Schwann cells :
1-Satellite schwann cells surround cell bodies in ganglia.
2- EnsheathIng schwann cells surround unmyelinated axons and produce the myelin sheath around axons.
** Neurons consist of a cell body and its processes, which usually include multiple dendrites and a single axon.
** Functional classification of neurons
a. Sensory neurons receive stimuli from the internal and external environments. They conduct impulses to the CNS for processing and analysis.
b. Interneurons connect other neurons in a chain or sequence. They commonly connect sensory and motor neurons; they also regulate signals transmitted to neurons.
c. Motor neurons conduct impulses from the CNS to other neurons, muscles, and glands.