Download Neurons - MrsMcFadin

Lesson Overview
The Neuron
Lesson Overview
31.1 The Neuron
Lesson Overview
The Neuron
Functions of the Nervous System
Lesson Overview
The Neuron
Functions of the Nervous System
• Peripheral nervous system = (made up of
nerves and supporting cells) collects
information about the body’s external and
internal environment.
• Also delivers instruction from brain to the
appropriate part of the body.
Lesson Overview
The Neuron
Functions of the Nervous System
• Central nervous system
(brain and spinal cord)
processes information
and creates a response
• Draw CNS in the space
below:
Lesson Overview
The Neuron
Neurons
• Messages carried by the nervous system are
electrical signals called impulses.
• Nervous system impulses are transmitted by
cells called neurons.
• Recall on page 1 of your notes that Neurons
are the cells that carry nerve impulses and
glial cells surround and protect neurons
Lesson Overview
The Neuron
Types of Neurons
• Neurons are classified according to the direction in
which an impulse travels:
1. Sensory neurons = carry impulses from sense
organs (eyes and ears) to spinal cord and brain.
2. Motor neurons = carry impulses from brain and
the spinal cord to muscles and glands.
3. Interneurons = process information from sensory
neurons and then send commands to motor
neurons.
Lesson Overview
The Neuron
Structure of Neurons
• Cell body = contains the nucleus and much of
the cytoplasm
• Dendrites = receive impulses from other
neurons and carry impulses to the cell body.
• Axon = carries impulses away from the cell
body
• Neurons may have dozens of dendrites, but
usually they have only one axon.
Lesson Overview
The Neuron
Structure of Neurons
• Axon terminals = series of small swellings at
the end of the axon
• Myelin sheath = an insulating membrane that
surrounds the axon and speeds up impulses
oThe myelin sheath has many gaps, called
nodes, where the axon membrane is
exposed and where impulses travel slower.
Lesson Overview
The Neuron
Label the picture:
Lesson Overview
The Neuron
The Nerve Impulse
• An impulse begins when a neuron is stimulated by
another neuron or by the environment.
• A neuron remains in its resting state until it receives
a stimulus to its dendrites large enough to start a
nerve impulse from the cell body
• Once it begins, the impulse travels quickly down the
axon away from the cell body toward the axon
terminals.
Lesson Overview
The Neuron
The Synapse
• At the end of the neuron, the impulse reaches
an axon terminal where a synapse is created
to cross the synaptic cleft
• Synapse = the point at which a neuron
transfers an impulse to another cell
• Synaptic cleft = the space that separates the
axon terminal from the adjacent cell.
Lesson Overview
The Neuron
The Synapse
• The axon terminal at a
synapse contains tiny
vesicles filled with
neurotransmitters.
• Neurotransmitters =
chemicals that transmit
an impulse across a
synapse to another cell.
Lesson Overview
The Neuron
Review: steps of synapse transmission
1. Impulse arrives at the synapse from the axon
terminals
2. Neurotransmitters are released from the axon
3. Neurotransmitters diffuse across the synaptic cleft
and bind to receptors on the dendrites of the
receiving cell
4. This binding stimulates a new impulse begins in
the second cell.
Lesson Overview
The Neuron
Draw the nerve synapse:
axon
terminal
neurotransmitters
Axon of
first cell
impulse
New impulse
in dendrite of
second cell