Tuguegarao Archdiocesan Schools System

Saint Joseph’s College of Baggao, Inc.

MODULE 8B
THE NERVOUS SYSTEM
I. Overview
The nervous system is divided into two parts: the central nervous system (CNS) and the
peripheral nervous system (PNS). The brain is the main organ of the nervous system. It is the control
center of the body. It receives messages from inside and outside of the body, interpreting and sending
back messages to the body organs or tissues that will execute the action. There are three parts of the
brain: the cerebrum, cerebellum, and the brain stem.
II. Intended Learning Outcomes
a. identify the parts and functions of the nervous system;
b. name common ailments/disorders of the nervous system.
III. Learning References:
1. T.R.E.K. 6 Technology. Research. Experiment. Knowledge
By: Emely J. Lagdamen
IV. Content/ Lecture: (2 hours)
Hello kids! Good day.
For today’s lesson, you will learn about the nervous system.
The Nervous System
Two Parts of the Nervous System
 Central nervous system is composed of the brain and the spiral cord. It receives, interprets and
sorts out information coming from the environment and within the body and gives specific
responses.
 Peripheral nervous system consists of all the nerves that are found throughout the body. These
nerve cells serve as the carries if information between the central nervous system and the body
tissues or organs.
The Brain
The brain is the main organ of the nervous system. It is the control center of the body. It receives
messages from inside and outside of the body, interpreting and sending back messages to the body
organs or tissues that will execute the action. It controls both the voluntary and involuntary activities
of the body. It enables you to learn, to understand, to reason, and to feel different emotions. The brain
is about 1.25 kilograms and it appears whitish-pink with a wrinkled surface.
It is encased in the skull and protected by three layers of tissues called meninges. They protect
the brain from excessive movement. The middle layer supplies the brain with oxygen and nutrients an
cushion it from shock. The inner layer serves as a wall that prevents bacteria from reaching the brain.
Both the brain and the spinal cord are surrounded by cerebrospinal fluid that protects the brain and
spinal cord from shock when the body performs different movements.
Three parts of the Brain
  Cerebrum is the largest part of the brain. It is mainly made up of billions of highly organized
neurons. The neurons are supported by glial cells. These cells also provide them with oxygen
and nutrients. He cerebrum controls a person’s speech, emotions, sensations, memory,
intelligence, reasoning, and thinking skills. It has two hemispheres:
1. Right hemisphere controls the left side of the body.
2. Left hemisphere controls the right side of the body.
 Cerebellum is the second part of the brain which is located at the back of the brain stem. It is
responsible for maintaining posture, balance, and coordination of body movements. It controls
the contraction and relaxation of the muscles. A person may be paralyzed if his cerebellum is
damaged or injured.
 Brain stem is composed of three parts:
1. Medulla oblongata controls the involuntary activities such as breathing heartbeat, and
digestion of food. It is responsible for reflex actions like blinking of the eye, coughing,
and jerking of the knees.
2. Pons connects the major motor and sensory nerves from the spinal cord, medulla
oblongata and cerebellum with the midbrain and cerebrum.
3. Midbrain controls eye movements, size of pupils as well as coordination of the head’s
movement in relation to sight and sound.
The Spinal Cord
The spinal cord is the second part of the central nervous system. It starts at the back of the
neck and extends throughout the backbone or vertebral column. It is usually 45 centimeters long. The
backbones or vertebral column protect the spinal cord from damage or injury.
It is composed of gray matter at the center and surrounded by white matter. The gray matter contains
bodies of nerve cells while the white matter contains the nerve fibers. There are 31 pairs of spinal nerves arising
from the spinal cord. Like the brain, it is also surrounded by meninges.

The spinal cord is the pathway of nerve impulses to and from the brain. That’s why, it is referred to as
the “neural highway”. It connects the central nervous system to the peripheral nervous system. Nerve impulses
coming from the eyes, ears, nose, tongue and skin pass upward through the spinal cord to the brain.

Another function of the spinal cord is to handle certain messages coming from the senses and give
motor responses that do not come from the brain. This immediate response is called reflex action. For example,
you accidentally touch a sharp object. Your hand will react immediately without thought. Before the message
reaches the brain, the action is already executed. A reflex action allows the body to act automatically to protect
itself from further harm.

When the spinal cord is damaged, a person could be paralyzed. He will los his sensation and will no
longer control his voluntary movements.

The Nerves or Neurons

The nerve cells or neurons are the basic units of the nervous system. They receive and transport
messages throughout the body. These messages are sent to the brain for interpretation and sent back to the
organ or gland for proper action or reaction. There are billions or neurons found in the body.

Three Types of Neurons

 Sensory neurons connect the sense organs to the brain and spinal cord. The messages that the
sense organs acquire from the environment reaches the brain through the sensory neurons.
 Motor Neurons carry the messages from the brain through the spinal cord then to the muscle
or gland.
 Interneurons or Associative Neurons carry messages between the sensory neuron and motor
neuron.
A neuron or nerve cell has three part: the cell body, the dendrites, and the axon.
The cell body is a tube-like structure with slender fibers called dendrites. Dendrites receive
messages and carry them to the cell body. The axon or nerve fiber is an extension of the cell body
which carries messages away from the cell body. The axon has tiny branches at its end and each
branch contains a knob which keeps and releases messages from one neuron to another or to a muscle
or gland or tissue. The ends of the axon do not touch the dendrites of another neuron. There is a tiny
space or gap between them called synapse. The message or impulse is passed on the next neuron or
nerve cell through the release of a chemical called neurotransmitters. The nerve impulses are small
electrical charges carried by the nervous system.
How Does the Nervous System Work?
Before the nervous system can respond to a particular situation, it should receive information
first. Where does this information come? How does this information reach the brain?
The sense organs: eyes, ears, nose, tongue and skin are the body’s windows to the
environment. They possess special cells called sensory receptors which receive information from the
environment. The information received by the sensory receptors can be in the form of light, sound,
heat, cold, pressure, pain, and chemical. These forms of information are called stimuli for they require
responses from the body.
Information received by the sensory receptors are transmitted to the sensory neuron, passing
from one neuron to another neuron until they reach the brain. The brain will interpret the message
and tell what the person sees, hears, smells, tastes or feels. In the brain, the interneurons gather and
interpret the information received from one or more sensory neurons. Then, the interneurons pass the
correct response message to the motor neuron that will carry out the action.
For example, you see a big, red rose in the garden, the light reflected by the red roe stimulates
the sensory receptor in your eyes. The nerve impulse travels from one sensory neuron to another
neuron until it reaches the brain. The area of the brain responsible for sight interprets the message as
a big, red rose, then sends the message back to the eyes through the motor neuron. You will then
recognize what you saw.
Common Ailments and Disorders of the Nervous System
For the ailments and disorders of the Nervous System, refer on your Science book, page 115.
How to Care of Nervous System
On how to take care of your Nervous system, read and study on page 116.
V. Learning Activity/Supplementary Activity
On your book, answer page 118-119 letter A-B.
VI. Generalization
For the summary of the lesson, look on page 120 (Chapter Summary).
VII. Assessment
Identify what is being described in the statement.
__________ 1. They carry the messages from the brain through the spinal cord then to the muscle or
gland.
__________ 2. It is the second part of the central nervous system
__________ 3. It receives, interprets and sorts out information coming from the environment and
within the body and gives specific responses.
__________ 4. It is the inflammation of the meninges that covers the brain.
__________ 5. An abnormal growth of brain tissues.
VIII. Application
On your book, answer page 121-122 (Chapter Tests).