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Nervous System
The Nervous System
1. Role of the Nervous
system:
– Receives, processes and
transmits information that
comes from the various
parts of the body and the
external world
2. Neurons
• The nervous system functions with the help of
neurons.
• Neurons are specialized cells that receives and
transmits messages
• Parts of a neuron:
–
–
–
–
Dendrites
Cell Body
Axon
Axon terminals
2. Neurons
• A) Role of neurons:
– picks up stimuli, transforms them into nerve
impulses and transmits these impulses
***A stimulus is anything that can be
perceived by a living organism and that can
trigger a reaction.
• Sound, light, heat, electrical shocks, odors and
hormones are examples of stimuli.
***A nerve impulse:
– Electrical signal transmitted by a neuron
Transmission of nerve impulses
2. Neurons
• B) Characteristics of neurons
– Neurons can be stimulated
– They are conductive
– Consumes a great deal of oxygen and glucose
– Can live more than 100 years
– Cannot reproduce itself
C) Parts of the Neuron
Nerve Impulses
• How it works?
– The dendrites receives the message or stimuli and
transforms it into a nerve impulse
– The nerve impulse is transmitted along the axon
– Nerve impulses travel from one neuron to another via
neurotransmitters (chemical substance) secreted by
axon terminals
• A synapse is the transition zone between 2 neurons that
allows a nerve impulse to be transmitted
D) How it works?
• Dendrites: receive and transform information into a
nerve impulse
• Axon: Carries impulse to axon terminal
• Axon Terminal: Via neurotransmitters, passes on the
impulse to another neuron or nerve
– A synapse is the transition zone between 2 neurons
that allows a nerve impulse to be transmitted
3. Central and Peripheral
Nervous system
A) Central Nervous System
• Made of the brain and the spinal cord
– The brain:
• Cerebrum: command central for voluntary motion,
interpretation of sense and of intelligence
• Cerebellum: center of balance and movement coordination
• Brain stem: control center of internal stimuli and of
involuntary movement
– Spinal cord:
• carries information from the various parts of the body to the
brain. It is also the reflex center.
– A reflex is a rapid and involuntary reaction to a stimulus
– A reflex arc is the path taken by a nerve impulse during a reflex
A) Central Nervous system
Parts
Function
Cerebrum
Voluntary motion
Thought
Interpretation
Cerebellum
Movement coordination
Center of balance
Involuntary movement
Control of internal stimuli
Brain Stem
Spinal Cord
Reflexes
B) Peripheral Nervous system
• Connects different parts of the body to the
central nervous system
• Nerves are structures that help transmit
information between the central nervous system
and various regions of the body
• There are two main types of nerves:
– Sensory
– Motor
4. Passing on a message
• Sensory receptors
– Picks up stimuli and transforms the stimuli into a nerve impulse
• Sensory Nerves
– Transmit information, in the form of a nerve impulse from
sensory receptors to the central nervous system
– Also pick up information from vital organs
• Analysis from the Central Nervous system
• Motor Nerves
– Transmit impulses from the central nervous system to the
muscles in order to produce voluntary and involuntary motion
For Example
•
Kicking a soccer ball
1. You see the ball (sight – sensory receptor)
2. The eye transforms the information into a
nervous impulse
3. The sensory nerves transmit the impulse to
the central nervous system
4. The brain analyses the information
5. The motor nerves send the “kick” impulse
from the brain to the leg muscles