Download File

The Nervous System &
Neurons
Overview of the Nervous
System
• STRUCTURES: brain, spinal
cord, & peripheral nerves
• FUNCTION: Recognizes and
coordinates the body’s
response to changes in its
internal and external
environments
Overview of the
Nervous System
• The ultimate
control of all the
organ systems
is done by the
nervous system.
A. Neurons
• Neurons are nerve
cells that carry
electrical impulses
through the body
• Impulse = message
• Neurons are
classified according
to the direction an
impulse travels.
• 3 Types of Neurons
– 1. Sensory: carry impulses from sense
organs to the brain
– 2. Motor: carry impulses from the brain to
muscles & glands
– 3. Interneurons: connect sensory and
motor neurons and process impulses
Interneuron
Sensory Neuron
Motor Neuron
Reflex Arc
Sensory Neuron
Interneuron
Motor Neuron
• Structure of a Neuron
Nucleus
Dendrites
Axon
terminals
Cell body
Myelin sheath
Nodes
Axon
– 1. Dendrites: receive impulses
– 2. Cell body: contains nucleus &
cytoplasm, largest part of cell
– 3. Axon: transmit impulses away
from cell body
– 4. Myelin Sheath: covering that
insulates the axon, sending the
impulse faster and gives axon a
whitish appearance
– Neurons with axons that have myelin make up
“white matter” in the brain, while neurons without
myelin are called “gray matter”
– 5. Nodes: gaps in the myelin
sheath where membrane is
exposed
– Impulses jump from one node to
the next
– 6. Axon terminals: transmits
impulse (message) to next cell