Neuron
Structure and
Function
Nervous System
 Nervous
system is
composed of specialized
cells called neurons.
 Neurons have long
“arms” called axons and
dendrites.


Axons carry impulses
away from cell body.
Dendrites carry impulses
to the cell body
 Connections
between axons and dendrites forms
our intelligence.
Central Nervous system
contains the brain &
spinal cord.
Cell bodies, axons, & dendrites in the
human brain.
Peripheral Nervous system (PNS)
 contains
all nerves
leading to and from
the Central Nervous
System
 Sensory receptors:
Nerves that carry
impulses towards
CNS

Detect light, pressure and
heat.
Motor neurons
 Nerves
that carry impulses from the CNS to
muscles or glands.
 Impulses
are
referred to as
action potentials.
 Dendrites
receive
action potentials
from other
neurons.
 Axons carry
action potentials
to other neurons.
 Dendrites take
action potential
to cell body,
axons away from
cell body.
Neuron
Structure
Axons
Cell bodies of neurons
myelin sheath
 Serves
to insulate axons &
dendrites and therefore
speed up the action
potential.
 The
myelin sheath is
made up of Schwann
cells.
Nodes of Ranvier
The
gaps between Schwann cells are
called the Nodes of Ranvier.
The action potential jumps from
Node of Ranvier to Node of Ranvier.
Resting Potential
 When
no impulse is occurring along neuron.
 Potential refers to differences in charges
inside and outside the membrane.
Distribution of charge


Positive
charges are on
the outside of
neuron.
Negative
charges are on
the inside of
neuron.
Sodium / Potassium pump




Due to more Na+
on outside &
more K+ on the
inside.
Negative protein
ions on inside.
The neuron is
said to be
polarized.
This is due to the
Na+/K+ pump.
Action Potential

Voltage gated channels
open.



Na+ moves in.
K+ moves out
Proteins stay inside
depolarization
 Charges
reverse.
 Outside
turns
negative.
 Inside turns
positive.
 This
is how the
nerve sends a
signal – through
electrical
impulses.
Pair share: do you think it take energy
for the cell to reverse the charge after an
impulse is sent? Why?
Refactory Period


Period of time after depolarization when neuron cannot
create action potential.
 Voltage gated channels close.
 Sodium/potassium pump must create resting potential.
 Uses ATP to do this.
Neuron is now back to resting potential.
Neuron Structure
 The
space
between neurons
is called the
synapse.
(Synaptic cleft)
Synapse
neurotransmitter
 The
action potential is
transferred across the
synapse by a chemical:
neurotransmitter.
 The neurotransmitter is
released from vesicles in
the axon.
 The neurotransmitter is
released when the action
potential reaches the
axon terminal.