LIWA

Nervous System

ICSE Class 7 · Biology · Chapter 6

What this chapter covers

Key definitions

Coordination is the working together of different organs and body parts in a proper order so that the body acts as one smooth whole.

The nervous system is the organ system that receives information from inside and outside the body, decides how to respond, and sends instructions to the body parts that must act.

The brain is the main control centre of the body, lying inside the skull, which receives messages from all parts of the body and sends out instructions to them.

The spinal cord is a long, soft, rope-like cord of nervous tissue that runs down from the brain through the backbone.

Nerves are thin, white, thread-like cords that connect the brain and the spinal cord to every part of the body.

The cranium is the part of the skull that encloses and protects the brain.

The cerebrum is the largest part of the brain, filling most of the skull at the top, front, sides and back above the cerebellum, and it controls thinking, memory, intelligence, speech, the senses and all the movements we make by choice.

Voluntary actions are actions that we perform by our own will, after deciding to do them, such as writing, walking, kicking a football or raising a hand in class.

The cerebellum is the small part of the brain that lies below the back portion of the cerebrum, and it keeps the body balanced and makes our movements smooth, steady and well coordinated.

Posture is the position in which a person holds the body while standing, sitting or moving.

The medulla oblongata is the lowest part of the brain, lying at the base of the skull just below the cerebellum, where the brain joins the spinal cord.

Involuntary actions are actions that take place in the body on their own, without our will or conscious control, such as the beating of the heart and breathing.

Key points

Questions answered

Name the three main parts of the human nervous system.
The brain, the spinal cord and the nerves.
What is coordination, and why does the body need it?
Coordination is the working together of different organs and body parts in a proper order. The body needs it so that all parts act as one smooth whole, for example so that the eyes, arms and legs act together to catch a ball.
Where is the brain located, and what protects it?
The brain lies in the head, inside the skull. The cranium, the part of the skull around the brain, protects it, along with protective layers and a cushioning fluid.
Which part of the brain controls thinking, memory and speech?
The cerebrum.
A person with an injured cerebellum can think clearly but walks unsteadily. Explain why.
Thinking and deciding to move are done by the cerebrum, which is unharmed. The cerebellum controls balance and smooth, coordinated movement, so damage to it makes walking unsteady.
Why is the medulla oblongata called essential for life?
It controls the heartbeat and breathing, which keep a person alive. Serious damage to it can stop these vital activities.
Classify these as voluntary or involuntary actions: writing a letter, heartbeat, kicking a ball, sneezing.
Writing a letter and kicking a ball are voluntary actions. Heartbeat and sneezing are involuntary actions.
Where is the spinal cord located, and how is it protected?
It runs from the base of the brain down the middle of the back. It is protected by the backbone, or vertebral column, whose ring-shaped vertebrae enclose it.