Ask Mr Brain...all will be explained

What is the brain made of and what is its function? RICHARD Yuen Long Merchants Association Secondary School The brain is part of the central nervous system inside a human skull and found in virtually all animals. Brain tissue is composed of nerve cells and their supporting cells, the glia.

Inside the brain, each nerve cell is connected to many others, up to 60,000 in the case of humans, and has links to and from the rest of the nervous system.

The human brain has a very complex structure and can be divided into three main parts: the hindbrain, midbrain and the forebrain. The hindbrain is responsible for the unconscious muscular control of balance. The midbrain is an area through which nerves enter and leave the brain. It connects the brain to the top of the spinal cord. The forebrain is the largest portion of the human brain and consists of a left and a right hemisphere. Each hemisphere includes 'grey matter', where the nerve cells are situated, and 'white matter', where the nerve fibres are.

The outer cortex of grey matter has a role in higher intellectual functions, sensory perception, and voluntary movement. The dominant hemisphere, usually the left, controls most aspects of language.

How many different kinds of spiders are there in the world? ALEX LAM Yuen Long Merchants Association Secondary School Spiders belong to a group of animals called the arachnids. Many people think they are insects, but they are not, although they share similar characteristics such as segmented bodies protected by an external skeleton.

Most spiders live on land. Their bodies are divided into two main segments, the head (or cephalothorax) and the abdomen.

The head has 12 appendages, including a pair of pedipals for grasping prey and a pair of fanglike chelicerae for tearing food. They also have eight legs.