Study of
the parts
&
functions of
neurons
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WHAT A NEURON LOOKS LIKE
3 MAIN TASKS OF NEURONS
Cells are specialized to…
1.) Receive information from the neurons
that feed it.
2.) Process the information
3.) Pass on information to the next
neuron.
3 TYPES OF NEURONS:
SENSORY NEURONS
Carries sensory information toward the
brain & spine.
What are your senses?
3 TYPES OF NEURONS:
MOTOR NEURONS
Transport messages away from the brain
to the muscles, organs and glands.
3 TYPES OF NEURONS
INTERNEURONS
aka the middle man
Sensory and motor neurons do not
communicate directly with each other.
Found in the brain and spine
REFLEXES
EVEN A HEADLESS WARM BODY COULD DO THAT!
parts
&
functions
PARTS & FUNCTION: DENDRITES
Receives messages from incoming
terminal branches of other cells
Passes message to cell body
PARTS & FUNCTION: CELL
BODY
Contains the cell’s nucleus (life-support)
Assesses all messages & passes on info
at the appropriate time
PARTS & FUNCTION: AXON
Cell body sends the message down the
axon
Moves info from cell body to terminal
branch
This is a one way street
Brain; the axons are very short
Leg; they can reach 3 feet long
PARTS OF THE AXON:
MYELIN SHEATH
Layer of fatty tissue
that insulates the axon
and speeds up the
impulse and protects
the message
Covering on your
headphones
If myelin sheath
deteriorates:
Communication to
muscles slows
leading to eventual
loss of muscle
control aka,
Multiple Sclerosis
(MS)
PARTS & FUNCTION:
TERMINAL BRANCH
Forms junction with next cell by
releasing the message into the
synapse
How neurons
communicate!!!!
ELECTROCHEMICAL COMMUNICATION
Information travels along the axon
electrochemically (chemical change
causes an electric signal)
What are the messages?
Neurotransmitters & hormones
HOW THE CELL BODY KNOWS WHEN TO
SEND AN ACTION POTENTIAL
Dendrites send two types of messages to
the cell body
If ‘excitatory’ messages outnumber
‘inhibitory’ messages, the cell reached
absolute threshold
Now the cell body releases an impulse that
sends the message down the axon
The impulse and the movement of the
message is called ACTION POTENTIAL
HOW THE MESSAGE GETS
‘THERE’…WHERE?
Once the cell body releases an Action
Potential, the message gets carried
down the axon and ends at the terminal
branches
PARTS OF ACTION POTENTIAL
 While the neuron is waiting to receive a message, its
called ‘resting potential’
 The cell body processes the message and if absolute
threshold is reached, the impulse is fired.
 Once the cell body fires an impulse, there is no going
back!
 ALL OR NOTHING PRINCIPLE
 It fires in the same direction every time (dendrites to
terminal branches)
 Once the cell body fires, it needs time to reset; refractory
period
 Just because the signal is stronger doesn’t mean the
message goes faster!
 How do we tell the difference between a tap and a slap?
WHAT HAPPENS AT THE
TERMINAL BRANCH?
When an action potential reaches a terminal
branch, it releases the message into the
synapse
These neurotransmitters stimulate the
dendrites on the next cell; the whole process
starts over again
MR. N GOES TO THE
BATHROOM