Transcript Nervous System

Nervous System
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Your body’s communication
network & control center
Peripheral Nervous System
(PNS)-gathers info from inside &
outside the body
Central Nervous System (CNS)receives this info & initiates a
response-composed of the brain
& spinal cord
Messengers & receivers of these
transmissions are NEURONS
BASIC STRUCTURE OF NEURON
 Cell body-contains
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nucleus & cell membrane
Dendrites-branching
projections of the cell body,
carry impulses into the cell
Axon-Threadlike extension
carries impulses to & from
the cell, at the end of axon
is the axon terminal
Myelin Sheath-Insulates
the axon & speeds up
transmission of the impulses
Synapse-point of contact
at which impulses are
passed from one cell to
another
Voluntary Actions vs Reflex Actions
 Impulses passed via the brain
 What is the chain of events that
happens from the instant you
hear the phone ring until you
pick up the phone?
 Every time a stimulus—such as
a ringing telephone—is
detected, the body's neurons
send a nerve impulse through
the nervous system.
 If the safety of our body
requires a very quick
response, the signals may
pass directly to a motor
neuron for instant,
unthinking action. This is a
reflex action. Signals sent
via the spinal cord
Education Portal: Neurons, Neurotransmitters
and The Nervous System
 http://education-
portal.com/academy/lesson
/neurons.html#lesson
 http://educationportal.com/academy/lesson
/neurotransmitters.html#le
sson
 http://educationportal.com/academy/lesson
/nervoussystem.html#lesson
REACTION TIME: The Ruler Test
 The nervous system helps information travel through your body. It consists of
the 5 senses, your brain, your spinal column, and the nerves that connect them
all together. Suppose your eyes see a baseball sailing toward your head. They
send a message about the approaching ball to your brain. This message travels to
a part of your brain called the cerebrum through nerves.Your cerebrum sends
this information to the cerebellum, which has to choose whether to move
away, duck, or put a hand up to catch the ball. It finally decides that you should
catch it—after all, you’re wearing your baseball glove! The cerebellum sends
this decision as message through other nerves to the arm and hand, activating
the muscles used to catch the ball.
 The time it takes from when your eye first notices the ball to when your arm
reaches up to catch it is an example of reaction time. Even though stimuli—
or changes in your environment that you react to—travel very quickly along
your nervous system as messages, your body doesn’t react instantly. Many
athletes spend hours practicing to improve their reaction time. In this activity,
you will conduct a simple, measurable experiment (the ruler drop test) to study
reaction time and determine how it can be improved with practice.
Problem: How can reaction time
be measured and improved?
Procedure
1. volunteer sits in a chair with good upright posture
2. volunteer places forearm so it extends over the edge of the table.
3. volunteer to places thumb and index (pointer) finger on either side of the
bottom of the vertically placed ruler. The number “1” should be on the
bottom, the “30” near the top.
4.Let your volunteer practice holding the ruler with those two fingers.
5.Now, ask the volunteer to remove their fingers from the ruler while you
continue hold it so that the bottom of the ruler is at a height of 2cm above
their fingers.
6.Tell your volunteer that you will release the ruler without telling them. Their
job will be to catch it with the thumb and forefinger as soon as they senses it
dropping.
7.Drop the ruler. When your volunteer catches it, record the number on the
ruler displayed just over their thumb. The lower the number, the faster their
reaction time.
8.Conduct several trials with the same volunteer.
9.Make sure to record the results for each trial in a table similar to the
following:
Volunteer cm trial 1 cm trial 2 cm trial 3 cm trial 4 cm trial 5 cm trial 6
NAME
NAME
Results
 Your results will vary depending on technique and which
volunteers you used, but you should expect that many of your
volunteers will show a slight improvement with practice.
 Why?
 When we begin to acquire a new physical skill through repetition,
our nervous system creates new neural pathways. Here’s an
example: when we practice something like catching a ruler over
and over again, all the members of that neural pathway (eye, brain,
muscles) become more well-connected and efficient. This
phenomenon is often referred to as muscle memory. However,
no matter how good your muscle memory for this task becomes,
it will always take some time for the falling ruler to travel as a
message from your eyes to your brain and from your brain to your
fingers!