The nervous system is composed of the central nervous system (CNS) and peripheral nervous system (PNS). The CNS consists of the brain and spinal cord and coordinates all body functions. The PNS connects the CNS to the limbs and organs through nerves and ganglia. Neurons are the basic cells of the nervous system and transmit electrochemical signals through axons and dendrites to control sensation, movement, and organ function. Glial cells support and protect neurons. The spinal cord has gray matter containing neuron cell bodies surrounded by white matter of myelinated axons.

1. Nervous Tissues
By Rasha Mohammed

2.  The nervous system is a complex collection of nerves and specialized cells
known as neurons that transmit signals between different parts of the
body. It is essentially the body's electrical wiring.
 nervous system is the major controlling, regulatory, and
communicating system in the body. It is the center of all mental activity
including thought, learning, and memory
 Like other systems in the body, the nervous system is composed of
organs, principally the brain, spinal cord, nerves, and ganglia. Together
these carry out the complex activities of the nervous system.
 Structurally, the nervous system has two components:
 * the central nervous system(CNS)
 * the peripheral nervous system(PNS).

3. The central nervous system (CNS)
CNS is the part of the nervous system consisting
of the brain and spinal cord. The central nervous
system is so named because it integrates
information it receives from, and coordinates and
influences the activity of all parts of the bodies

4. The peripheral nervous system (PNS)
 (PNS) is the part of the nervous system that
consists of the nerves and ganglia outside of
the brain and spinal cord. The main function of
the PNS is to connect the (CNS) to the limbs
and organs, essentially serving as a
communication relay going back and forth
between the brain and the extremities

5. Functions of the Nervous System
 1. Gathers information from both inside and outside
the body - Sensory Function
 2. Transmits information to the processing areas of
the brain and spine
 3. Processes the information in the brain and spine –
Integration Function
 4. Sends information to the muscles, glands, and
organs so they can respond appropriately – Motor
Function

6. 
Basic Cells of the Nervous System
Nerves are cylindrical bundles of fibers that start at the brain and
central cord and branch out to every other part of the body.
The nervous system comprises of two group of cells:-
1)glialcells2)neurons.
Neurons are responsible for sensing change and communicating
with other neurons. Glial cells work to support, nourish, insulate
neurons and remove waste products.
Neurons send signals to other cells through thin fibers called
axons, which cause chemicals known as neurotransmitters to be
released at junctions called synapses

7.  1) Neuron •
 The neuron is the basic unit
in the nervous system. It is
a specialized conductor cell
that receives and transmits
electrochemical nerve
impulses. A typical neuron
has a cell body and long
arms that conduct impulses
from one body part to
another body part.

8. Parts of a Neuron
Cell Body with nucleus & most of cytoplasm •
 Cell body or Soma – contains the nucleus, the neuron’s intracellular organelles (such as the
mitochondria and Golgi apparatus) and it is the location for cellular metabolism. It is also
contains the Nissl Substance. These are granules containing rough endoplasmic reticulum
and free ribosomes, making it the site of protein synthesis.

9.  •
Dendrite
 The cell body has several highly branched, thick extensions that appear like cables and are
dendrites. The exception is a sensory neuron that has a single, long dendrite instead of many
dendrites, The dendrite's function is to carry a nerve impulse into the cell body.
 Axon – fiber
 An axon is a long , thin process that carries impulses away from the cell body to another neuron
tissue. There is usually only one axon per neuron
 It arises from the soma from an area called the axon hillock, where action potentials are
action potentials are conducted through the axon to the axon terminal.

10.  .
 Schwann Cells-
 The neurilemma is the layer of Schwann cells with a nucleus. Its function is to allow damaged nerves to
regenerate. Nerves in the brain and spinal cord do not have a neurilemma and, therefore cannot recover
damaged.
 cells which produce myelin or fat layer in the Peripheral Nervous System •
 Myelin sheath
 The neuron is covered with the Myelin Sheath or Schwann Cells. These are white segmented covering
axons and dendrites of many peripheral neurons. The covering is continuous along the axons or
dendrites except at the point of termination and at the nodes of Ranvier.

 Node of Ranvier
 gaps or nodes in the myelin sheath •
 Impulses travel from dendrite to cell body to axon

11.  Glia, also called glial cells or neuroglia, are non-neuronal cells in the
central nervous system (brain and spinal cord) and the peripheral nervous
system that do not produce electrical impulses
 They maintain homeostasis, form myelin, and provide support and
protection for neurons.
 . They have four main functions:
 (1) to surround neurons and hold them in place
 (2) to supply nutrients and oxygen to neurons
 (3) to insulate one neuron from another
 (4) to destroy pathogens and remove dead
 neurons.
2- Neuroglial

12. * SPINAL CORD :-- In cross section spinal cord is oval in shape , from dorsal side is divided into two
halves, left and right half by dorsal median septum From the anterior ( ventral ) side there is fissure
called the median fissure
The spinal cord surround by the connective tissue layers of the MENINGES :-
1- the thick and fibrous outer DURA MATER.
2- the thinner and middle ARACHNOID
3- the delicate inner PIA MATER , which they closely
adheres to the surface of the spinal cord .
The PIA MATER occur directly around the
white mater and the gray mater.
Spinal cord

13.  The spinal cord in cross-section has a central region of darker gray
matter which look like a butterfly or H- shape and the rest is lighter
white matter. The gray matter is made up of neuroglia cells and
neuron cell bodies. The white matter is made up of neuron axons,
mostly but not all myelinated
the CNS is devoid of neurons and consist primarily
of myelinated axons .the myeline sheath around the
axons imparts a white color to this region, while the
lack of myelin imparts a gray and the color to the
gray mater of the CNS