The Nervous System
Lesson 5: Standard 9b. Students know how the nervous
system mediates communication between different parts of
the body and the body’s interactions with the environment.
Standard 9d. Students know the functions of the nervous
system and the role of neurons in transmitting
electrochemical impulses.
The Nervous System
• Consists of the brain,
spinal cord, and
peripheral nerves
• Controls and
coordinates functions
throughout the body
and responds to
internal and external
stimuli
• Helps maintain
homeostasis in the
body through feedback
loops
The Central Nervous System (CNS)
• Consists of the brain and spinal
cord
• Both the brain and spinal cord are
wrapped in a membrane called
the meninges
• Meningitis is caused by a
bacterial infection that causes the
meninges to swell. It can be fatal.
There IS a vaccine for meningitis.
• Between the meninges and the
CNS, there is a liquid called
cerebrospinal fluid that cushions
the CNS and acts as a shock
absorber. It also allows for the
exchange of nutrients and waste
between the brain and the blood.
The Brain
• The place nerve impulses flow to and originate
from
• The cerebrum is the largest area of the brain and
is the site of learning, intelligence, and judgment.
It is divided into two hemispheres that are
connected by a band of tissue called the corpus
callosum.
• The cerebellum is the second largest region of the
brain. It is responsible for coordinating and
balancing the body’s movements
• The brain stem is below the cerebellum. It
connects the brain to the spinal cord. It consists
of the pons and the medulla oblongata. It
regulates the flow of information from the brain
to the rest of the body. Blood pressure, heart
rate, and breathing are controlled by the brain
stem.
• The thalamus & hypothalamus are found between
the brain stem and the spinal cord. They receive
messages from the body and recognize hunger,
thirst, anger, fatigue, and body temperature.
The Spinal Cord
• The spinal cord is like a telephone
wire – it is the main
communication link between the
brain and the body.
• it transmits nerve impulses from
brain to body
• The spinal nerves branch out,
connecting to the rest of the
body. This is where the chicken
pox virus, varicella-zoster, likes to
hide out and be dormant after an
infection. If you had the chicken
pox as a child, you might get
shingles as an adult.
• some reflexes are processed in
the spinal cord
The Peripheral Nervous System
• Consists of all of the nerves that
are not part of the brain and
spinal cord
• The sensory division transmits
nerve impulses from sense
organs to the CNS
• The motor division transmits
impulses from CNS to muscles or
glands
• The motor division is further
divided into the somatic and
autonomic nervous systems.
• The somatic nervous system
regulates voluntary movements
• The autonomic nervous system
regulates involuntary
movements
Neurons
• Neurons are the
specialized cells of the
nervous system
• Most neurons have an
axon, cell body, and
dendrites
• Neurons transmit
information via
electrical impulses
Neurons (continued)
• The cell body is the largest
part of the neuron. This is
where the nucleus and most
of the cytoplasm is.
• The dendrites are short
branches that carry impulses
from the environment or from
other neurons toward the cell
body
• The axon is a long fiber that
carries impulses away from
the cell body. It is covered in
a fatty myelin sheath that
insulates and protects it.
Types of Neurons
• Motor neurons carry
impulses from the brain and
spinal cord to the muscles
and glands
• Sensory neurons carry
impulses from the sense
organs to the spinal cord
and brain
• Interneurons connect
sensory and motor neurons
and transmit impulses
between them.
Nerve Impulses
During the video, answer the questions in your notes.
The Synapse
• At the end of a neuron,
there is an axon terminal.
Usually, the neuron makes
contact with another cell
here. This is where impulses
are transmitted from one
neuron to the next.
• The synapse is the place
where a neuron can transmit
its impulse to another cell
• The terminals contain tiny
sacs of neurotransmitters,
chemicals that are used to
transmit an impulse across a
synapse to another cell