Transcript Slide 1

What gets on your
“nerves”?
STIMULUS

Any change or signal in the environment
that can make an organism react.
EX: A soccer ball comes zooming toward
you.
 EX: A friend tells you a funny joke.
 EX: You touch a hot stove.

How do you react?
RESPONSE

What your body does in reaction to the
stimulus.
EX: You kick the soccer ball toward the
goal.
 EX: You laugh at the joke.
 EX: You scream, pull your hand away, hop
around, and shake your arm.

VOLUNTARY VS.
INVOLUNTARY RESPONSES

VOLUNTARY


Body chooses to
respond to the
stimulus.
EX: Choose to kick the
ball, choose to not
answer the phone
when a friend calls.

INVOLUNTARY

Body automatically
responds to the
stimulus.

EX: heart beats,
salivate when
something yummy is
put in front of you,
wrinkle your nose
when you smell
something stinky.
HOMEOSTASIS

The process by which an organisms internal
environment is kept stable in spite of changes in
the external environment.

The nervous system helps maintain homeostasis
by directing the body to respond appropriately to
the information it receives.

EX: When you are hungry, your nervous system
directs you to eat. This action maintains
homeostasis by supply your body with energy it
needs.
The Three
Functions
Of The
Nervous System
Receive information
1. RECEIVES INFORMATION

Your body checks conditions outside of
the body and inside the body.

SENSES help monitor changes and keeps
the body informed externally.
Nerves also receive information of
changes happening internally.
Respond to information
voluntary
involuntary
2. RESPOND TO
INFORMATION

Any change or signal in the environment
that can make an organism react to a
stimulus.

Body (Brain) voluntarily or involuntarily
chooses to react to the stimulus.
Maintain homeostasis
3. MAINTAINING
HOMEOSTASIS

The nervous system maintains
homeostasis by directing the body to
respond appropriately to the information it
receives.

EX: Keeping body temp., glucose levels,
and blood pressure regulated.
HOW IS A STIMULUS AND
RESPONSE TRASMITTED?

NERVE
CELLS…NEURONS!

A cell that carries
information through
your nervous system.

The message that a
neuron carries is
called a nerve
impulse.
The neuron
Dendrites
Dendrites
axon
axon
Cell body and
Cell body and
nucleus
nucleus
Dendrites
DENDRITE

Thread-like extensions on a cell body.

Carries impulses toward the cell body.

Impulse will be transmitted from the
dendrite, to the cell body, and down the
axon.
axon
AXON

Carries impulses away from the cell body.

All nerves cells have ONE axon.

The end of the axon is an AXON TIP.

The AXON TIP transmits the piece of
information to the next nerve cell.

Each neuron can have one or more axon tip.
PATH OF NERVE IMPULSE
(STIMULUS/RESPONSE)

SENSORY NEURON

INTERNEURON

MOTOR NEURON
SENSORY NEURON

Picks up stimulus from the internal or external
environment and converts each stimulus into a
nerve impulse.

The impulse travels along the sensory neurons
until it hits an INTERNEURON.

EX: Nerve receptors (dendrites) in ears pick up
the sound of the phone ringing. The stimulus is
converted to a nerve impulse that travels to the
interneuron.
INTERNUERON
From the sensory neurons, the nerve
impulse passes to interneurons in the
brain.
 The brain interprets the impulses from
many interneurons.


EX: The interneurons make you realize the
phone is ringing. Your brain decided that
you should answer the phone.
MOTOR NEURONS

The message from the brain travels from the
INTERNEURON to the MOTOR NEURON.

The motor neurons send the impulses
(message) to the muscles to carry out the
response.

EX: Your muscles walk you to the ringing phone,
you pick up the phone, and say “hello?”
Path of a nerve impulse
Sensory neuron
Stimulus
Response
Motor
neuron
interneuron
PATH OF A NERVE IMPULSE
How does the nerve impulse
cross the gap between the axon
tip and the next neuron?
The axon tips release
chemicals that enable the
impulse to cross the gap at the
synapse.
Synapse
SYNAPSE

Space between each
axon tip and the next
dendrite.

Chemical
messengers cross
this space to pass the
message to the next
nerve cell.
REACTION TIME

The time it takes for a message to travel
along your nerve pathways beginning from
picking up the stimulus to the delivery of
the response