The nervous system senses the environment using receptors and transmits signals between parts of the body via neurons. It interprets incoming information in the brain which can then direct various responses, such as muscle movement. Neurons transmit electrochemical impulses along their axons to dendrites of other neurons at junctions called synapses using neurotransmitters. The central nervous system includes the brain and spinal cord while the peripheral nervous system connects it to the rest of the body. Reflex arcs allow for fast, involuntary responses without brain involvement. Diseases like multiple sclerosis and Isaac's syndrome can impair neural functioning.

1. Nervous System
Grade 10

2. What is the Nervous System?
In the simplest form,
the nervous system is
an organ system
specifically designed
to sense the
environment and to
produce a response
to changing
conditions

3. How Does the Nervous System
Sense its Surroundings?
• The nervous system
has a number of
receptors designed to
accumulate
information about the
environment
• Examples of these
receptors include:
taste buds, rods and
cones on the retina,
pressure sensors in
the skin

4. How Does the Nervous System
Transmit Information from One Part
of the Body to the Next?
• The nervous
system transmits
signals from one
part of the body
to another (taste
to brain) by
using neurons

5. How Does the Nervous System
Interpret the Information?
• The brain acts as the
main filter for information
coming from all over the
body
• The brain then has to
prioritize information that
is more important than
others
• The brain has to then
decide upon a set of
actions to respond the
environment

6. What type of Responses can the
Brain Direct?
• The brain can cause a multitude of reactions to
respond to the environment such as:
• the movement of a muscle to avoid a moving object
• the increase of heart rate to escape from a bear
• the increase in pupil sight to see in the dark

7. What is a Neuron?
• A neuron is the smallest unit of the nervous system
• Every part of the nervous system is composed of
specialized neurons

8. Parts of the Neuron
The Cell Body
is the center of
the cell. Here
most chemical
reactions occur,
DNA is in the
nucleus, most
of the
organelles are
located here

9. Neuron Continued
Dendrites receive
information. This
can come from
two sources,
other neurons or
specialized
receptors (like
taste buds)

10. Neuron Continued
The axon
transmits the
message along
the rest of the
neuron to the
next neuron

11. Electrical
Impulses
•Electrochemical impulses transmit signals to other
parts of the nervous system.
•There is an all or none response to stimulus (either
the nerve cell decides to send a message, or it
remains inactive)
•There is no difference in the strength of the impulse
•Once it decides to send a message, the message
cannot be recalled

12. Axon
•Although the stregth of an impulse cannot be changed, it can
become faster
•Sometimes Schwann Cells wrap around the axon and
produce a Myelin Sheath
•These nerve cells are called Myelinated
•The myelin sheath in conjunction with the Nodes of Ranvier
speeds up the electrochemical impulse
Schwann Cells
Node of Ranvier

13. Why do Some Things Hurt More
Than Others?
• Because the number
of nerve cells that
receive the stimulus
increase
• The more nerve cells
that send an impulse,
the greater the
sensation of pain

14. How Does the Impulse go From one Neuron
to the Next?
• The axon of the first
neuron is connected to
the dendrites of a second
neuron by a space called
the SYNAPSE
• Chemicals called
NEUROTRANSMITTERS
send a signal to the
second neuron asking it
to continue sending the
information

15. Neurotransmitters
• Neurotransmitters
are transported to
the edge of the
synapse by synaptic
vessicles
• Many drugs that
target the brain
affect the
transmissions of
singals across the
synaptic cleft

16. Divisions of the Nervous
System
• CNS- the central
nervous system
includes the brain and
spinal cord
• PNS- the peripheral
nervous connects the
CNS with the rest of
the body

17. Divisions of the Nervous System
• Somatic
Nervous
System-
voluntary control
of functions
• Autonomic
Nervous
System-
involuntary
control for
automatic
functions

18. Reflex Arc
• In a reflex arc, your
body responds to a
stimulus without the
direct intervention of
the brain
• This is because
sending information to
your brain and waiting
for a decision to be
made would take too
much time

19. Reflex Arc
• A reflex arc is made up of three different types
of neurons:
1. Sensory Neurons- Brings information to the
Central Nervous System (Brain and Spinal
Cord)
2. Association (Interneurons) Neurons- Found
only in the Central Nervous System (CNS)
3. Motor Neurons- Carries impulses from the
CNS to effectors (muscles or glands)

20. Reflex Arc
• A Reflex Arc must always contain the
following:
1. Receptor (ex. pain receptor)
2. Sensory Neuron
3. Interneuron
4. Motor Neuron
5. Effector (Muscles)

23. Diseases of the Nervous System
• Multiple Sclerosis (MS)- Deterioration of the myelin sheath
(slower impulses)
• Scar tissue builds up on the axon
• No impulse transmission
• Impared neural functioning (loss of co-ordination, tremors,
paralysis)
• Cause remains unknown

24. Diseases of the Immune System
• Isaacs Syndrome:
• Rare
• Involuntary muscle
contractions
• May interfer with
speech and
breathing