O verview o f neuron com m unication w ithin th e nervous system • Figure 7.7
NNER
3
Brain
neuron
I Within the brain, multiple synapses between interneurons conduct the
information through the brain tissue. The interneuron synapses with the
upper motor neuron to begin to signal to the effector.
I Synaptic transmission between the sensory neuron
and an interneuron stimulates an action potential in
the interneuron that travels to the brain.
Touching the pen stimulates the
sensory receptors in the fingers.
Stimulation of these receptors
triggers an action potential in
the sensory neuron that
travels to the spinal cord.
Left side of brain
Cerebral cortex
Interneuron
Upper
motor
neuron
Sensory
receptor
Right side of brain
\
Interneuron
Spinal cord
Lower motor neuron
3
The upper motor
neuron synapses on
a lower motor neuron.
Key:
— ► Graded potential
— ► Nerve action potential
— -^Muscle action potential
The lower motor neuron conducts the
signal to the muscle, causing movement
of the hand and pen.
Neuromuscular junction
Skeletal muscles
sensory receptors that gather data about the internal or
external environment of the body. Interneurons link the
sensory neurons with motor neurons and assist with infor-
mation processing. Motor neurons are involved in sending
signals out to effector organs (such as muscles or glands) to
produce a response. In motor neuron connections to skeletal
muscles, two neurons form the motor pathway. The upper
motor neuron begins at the brain and relays the message to
the lower motor neuron in the spinal cord. The lower motor
neuron then sends the signal to the muscle cell. All neu-
rons involved in such a pathway use action potentials and
synaptic transmissions from one neuron to another to move
information along (Figure 7.7).
CONCEPT CHECK
1.
What
is the relationship between the enteric
nervous system and the autonomic nervous
system?
2.
What
is the function of the dendrites of a neuron?
3.
What
ionic changes occur in each of the phases
of the action potential?
4.
How
does an action potential in a presynaptic
cell elicit an action potential in a postsynaptic
cell?
Nerve Cells "Talk" to Each Other 199
PROCESS DIAGRAM
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