Transcript Introductory Assignment to the Nervous System

 What
organ coordinates most of the activities
of the nervous system?
 Through what part of the body do most
messages reach or leave the brain?
 The brain and spinal cord form what part of
the nervous system?
 What connects the central nervous system to
muscles and sense organs throughout the
body?
 What carries signals throughout the nervous
system?
 Name some parts of a nerve cell, or neuron.
 What
do we call the tiny space between
neurons over which signals must pass from
neuron to neuron?
 What do we call the electrical signals that
have reached the end of an axon and have
become chemical signals?
 What special nerve cells allow us to see,
hear, feel, taste, and smell the world around
us?
 What special nerve cell allows us to move?
 Anything
that brings about a response
Examples
* stimulus – step on nail
* response – jerk foot up
* stimulus – see bright light
* response – squint Eyes
 Basic
units of the nervous system
Axon tips
 Dendrites
reach out and “grab” sensory
information and send it to the cell body
 Axons carry the message away from the cell
body to another neuron
 sensory
neurons – receive sensory info
from environment and send it to the brain
or spinal cord
 interneurons – in the brain and spinal
cord, they decide what to do with the
message from the sensory neuron
 motor neurons – carry reaction message
away from the brain toward muscles
 Neurons
do not touch. Messages are
transferred by chemicals jumping across the
gap between two neurons, called a synapse.
Sensory neurons in the ear
hear breaking glass.
The brain takes the message
from the sensory neurons
and decides if a response is
necessary.
The brain decides the
response should be to cover
eyes with hands. This
message leaves the brain via
a motor neuron.
The motor neuron deadends in a muscle, telling the
muscle to contract and jerk
up the arms.
Example taken from an issue of National Geographic, p. 528
 Central
is brain and spinal cord, only
 Peripheral is all nerves outside the brain
and spinal cord. It connects the body to
the brain and spinal cord.
 Sensory neurons travel toward the brain
or spinal cord for message interpretation.
 Motor neurons travel away from the brain
or spinal cord for responses.
• Spinal
cord’s
diameter gets
larger and
larger as you go
up the back
toward the
brain.
•
Spinal nerves have both sensory and
motor neurons, so messages travel in
two directions
 somatic
– nerves that go to the skeletal
muscles, so voluntary
 autonomic – involuntary (sympathetic and
parasympathetic)
 Involuntary,
automatic responses to stimuli
 Controlled by spinal cord, not brain
 Leaving out the brain enables the body to
react faster