Transcript 31.1 The Neuron

31.1 The Neuron
Functions
Nerve Impulse
The Synapse
Objectives:
• 1) Students will be able describe the
anatomy and purpose/function of
neurons.
• 2) Students will be able to describe how
a nerve impulse (action potential) is
generated and travels from neuron to
neuron.
Functions of the Nervous System
• The nervous system records sensory data
from the body’s external and internal
conditions, sends that information to the
Central Nervous System for processing and
then responds to the stimuli.
Peripheral Nervous System
• Role: Collects sensory
information about the
body’s internal and
external environment
and relays it to the
Central Nervous
system
• Structures: Nerves
and supporting cells.
The Central Nervous System
• Role: Processes
information sent to it
by Peripheral Nervous
system, processes that
information and sends
out a signal (response)
to the correct body
part.
• Structures: Brain and
Spinal Column
Thinking Question:
• What do you think happens when
you receive a stimulus from one of
your senses. In your notes write out
the path it would take from outside
the body and through the aspects
of the nervous system.
The Nerve Impulse
The Nerve Impulse
• Resting Potential: -70 mV
(milli-volts). This is caused
by K+ (Potassium ions)
being pumped into the cell
and Na+ ions being pumped
out of the cell.
• This voltage is the
difference between the
inside and the outside of the
cell (across the membrane)
Action Potential
• Another name for
a “nerve impulse”
this is when the
neuron “fires”
and transmits a
signal down its
axon and passes
it on to another
neuron or a cell.
Threshold
• This is the voltage
the neuron has to
reach before it
“fires” or sends a
signal. This is
approximately 55mV
The Nerve Impulse
• Neuron starts at the
resting potential
• (-70mV difference
between the inside
and outside of the
cell)
• Na+ is actively
transported out of
the cell, K+ in. K+
slowly leaks out.
The Nerve Impulse
• A Stimulus is received from
the external and internal
environment.
• If the stimulus is strong
enough to overcome the
threshold, sodium channels
open at the beginning of the
axon and the internal cell
environment become
positive. This sends the
nerve impulse down the
axon to the axon terminals.
The Synapse
• Synapse: The
point where the
action potential of
one neuron is
transferred across
the synaptic cleft
into the dendrites
of another neuron
in the form of a
neurotransmitter.
Synaptic Cleft
• The gap between the
Axon terminals of one
neuron and the
dendrites of the next
neuron or receptors
of the target cell.
• Neurotransmitters
pass across the
synaptic cleft to pass
on signals
Neurotransmitters
• Neurotransmitters
are chemicals that
are transmitted
from the synapse
across the
synaptic cleft to
another neuron or
cell.