Brain structure and function

The brain is the main control centre of the nervous system, coordinating the body's actions by receiving, processing and sending nerve impulses. Its main regions each have distinct functions.

Because nerve tissue is soft and easily damaged, the brain is protected by the cranium, by three membranes called the meninges, and by a layer of cerebrospinal fluid that cushions it against shock. Exam questions on this topic usually ask you to match a named region to its function and to explain how a feature of the region suits that function.

Parts and functions

How structure suits function

Each region of the brain has a feature that fits its job, and an examiner awards the mark for the link between the feature and the function, not for naming the feature alone.

• Highly folded cerebrum surface, the folds increase the surface area so far more neurons fit inside the skull, supporting complex functions such as memory, reasoning and interpreting the senses.
• Position of the medulla oblongata at the base of the brain, it connects directly to the spinal cord, so impulses controlling vital involuntary functions are relayed rapidly without conscious control.
• Dense, folded cerebellum, it packs many neurons to process signals from the muscles and balance organs, giving smooth, coordinated movement.
• Protective layers, the cranium, meninges and cerebrospinal fluid together shield the delicate nerve tissue from physical shock.
• Hypothalamus linking two systems, it connects the nervous system to the endocrine system, so the brain can trigger both fast nerve responses and slower hormonal responses.

Related processes

The brain is central to coordination. A stimulus detected by a receptor sends impulses along sensory neurons to the brain, which processes them and sends impulses along motor neurons to an effector such as a muscle or gland.

For voluntary actions the cerebrum decides the response, while the cerebellum refines the movement so it is smooth and accurate.

Through the hypothalamus and pituitary gland the brain also drives homeostasis, helping to regulate body temperature and the water content of the blood and linking nerve control to hormonal control. In a reflex action, however, the response is coordinated by the spinal cord or the medulla oblongata rather than the cerebrum, which is why a reflex is fast and automatic.

Common exam errors

Worked question

Question (in the style of Paper 2 Section A): The diagram shows a section through the human brain with regions P, Q and R. (a) P is the largest region.

Name P and state one of its functions. [2 marks] (b) A gymnast lands smoothly and keeps her balance after a jump. Name the region that coordinates this. [1 mark] (c) Explain how region R, the medulla oblongata, is suited to controlling heartbeat and breathing. [3 marks]

Model answer: (a) P is the cerebrum; it controls voluntary actions (accept thinking, memory or interpreting the senses). (b) The cerebellum.

(c) The medulla oblongata controls involuntary actions; it lies at the base of the brain and connects to the spinal cord, so impulses controlling heartbeat and breathing rate are relayed rapidly and automatically without conscious control.

Marking note: in (a) one mark is for naming the cerebrum and one for a correct function. In (c) award one mark each for involuntary control, for the position or connection to the spinal cord, and for the rapid, automatic relay.

Source:SRC-DSKP-EN

Frequently asked questions