The nervous system is composed of two main divisions: the central nervous system (CNS) containing the brain and spinal cord, and the peripheral nervous system (PNS) containing nerves. Sensory neurons carry messages from receptors to the CNS, which then integrates the information and sends motor commands through efferent pathways and motor neurons. Motor actions are either somatic, occurring in skeletal muscle voluntarily, or autonomic, occurring involuntarily in smooth and cardiac muscle. The cells of the nervous system are neurons, which transmit nerve impulses, and neuroglial cells which support neurons. Myelination of neurons by oligodendrocytes in the CNS and Schwann cells in the PNS increases transmission rates.

1. Introduction to Nervous
System

3. Composition of Nervous System
 Two main divisions
 1) Central Nervous
system (CNS) brain
and spinal chord
 2)Peripheral Nervous
System (PNS) nerves

4. Remember from Homeostasis
 Message is received from sensory
receptor along sensory neuron
(afferent pathway)
 Messages reaches brain and is
integrated (control center)
 Reaction command sent down
efferent pathway along motor neuron
(motor output)

5. Types of Motor Actions
 Somatic
 Happens in skeletal
muscle
 voluntary
 Autonomic
 Happens in smooth
and cardiac muscle
 Involuntary
 2 parts
 Sympathetic and
parasympathetic

6. Cells of the Nervous System
 Broken down into two
groups
 1) supporting cells
 2) neurons

7. Examples of Neuroglia (supporting
cells)
 1) astrocytes –
anchor neurons to
capillaries
 2) microglia –
phagocytes (digest
debris and dead cells)
 3) Ependymal cells-
ciliated; always on
surface near spinal
fluid; circulates fluid

8. One more Neuroglial cell (in CNS)
 4)Oligodendrocytes –
fatty; insulated nerve
fibers
 Produce myelin
sheath which
surround and insulate
the nerve fiber

9. In PNS
 Instead of
oligodendrocytes,
they have Schwann
cells, which insulate
the nerve fiber
 Satellite cells – form
protective layer
around nerve cell
body

10. Neurons
 Specifically designed
to transmit message
(nerve impulse)

11. Parts of a Neuron
 1)Cell Body- contains
nucleus
 2) fiber (process)-
carries message to
next neuron
 Toward cell body =
dendrites
 Away from cell body =
axon

12. Axonal Terminal
 As an axon ends, it
branches into
hundreds of
synapses.
 Releases
neurotransmitters to
next neuron or
muscle

13. Myelination of Neurons
 In CNS, the fatty
covering is
oligodendrocyte
 In PNS, fatty myelin
forms Schwann cells,
which increase
transmission rate.
 Gaps between
Schwann cells= Nodes
of Ranvier