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Biology · The Nervous System

The Brain

The brain controls almost everything that you do. This lesson is for separate Biology. It covers the structure and functions of the main regions of the brain, and for Higher tier students the difficulties of investigating brain function and of treating damage to the nervous system.

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  • 8 key terms
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Learning Objectives

  1. 1Describe the structure and function of the cerebrum, cerebellum, medulla, hypothalamus and pituitary gland.
  2. 2(Higher tier) Explain some of the difficulties of investigating brain function, including ethical issues.
  3. 3(Higher tier) Explain some of the limitations in treating damage and disease in the brain and other parts of the nervous system.

Retrieval practice

  1. 1

    What is the central nervous system?

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    The brain and the spinal cord.

  2. 2

    What is a hormone?

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    A chemical messenger carried in the blood.

  3. 3

    What controls the heart rate and the breathing rate?

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    The brain.

  4. 4

    What is a neurone?

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    A nerve cell that carries electrical impulses.

The control centre

The brain is about 1.4 kg of soft tissue made of billions of neurones, protected by the skull. It receives impulses from receptors, makes decisions, stores memories, controls movement and keeps the body's internal conditions steady. Different regions have different jobs, and damage to a region can cause a loss of the matching function.

Regions of the brain

The brain has several main regions, and each one controls different functions.

  • Cerebrum

    The large, wrinkled upper part, divided into two halves. It controls conscious thought, memory, language, intelligence and the voluntary movements, and it receives information from the senses.

  • Cerebellum

    At the back, below the cerebrum. It coordinates movement and keeps balance and posture.

  • Medulla

    At the base of the brain, joined to the spinal cord. It controls automatic actions that keep you alive, such as the heart rate and breathing.

  • Hypothalamus

    Below the middle of the brain. It monitors and controls body temperature and water balance.

  • Pituitary gland

    A small gland attached to the hypothalamus. It releases hormones that control other glands in the body, so it is called the master gland.

What each region controls

Thinking and movement

  • Cerebrum: conscious thought, memory, language, voluntary movement
  • Cerebellum: coordination of movement and balance

Keeping the body going

  • Medulla: heart rate and breathing
  • Hypothalamus: body temperature and water balance
  • Pituitary gland: releases hormones

The pituitary gland and the hypothalamus

These two regions link the nervous system to the endocrine system.

  • Hypothalamus

    Contains receptors that monitor the blood, and sends signals to the pituitary gland.

  • Pituitary gland

    Releases hormones into the blood in response, which control other glands such as the thyroid gland and the ovaries.

  • Why it matters

    This connects the quick control of the nervous system with the slower control of the hormones.

Investigating the brain (Higher tier)

The brain is hard to study, and what we know has been built up from several different kinds of evidence.

  • Case studies

    Studying people with brain damage from injury or stroke shows which functions are lost, but every injury is different and it is hard to be sure which region is responsible.

  • Scans

    MRI and similar scans show which regions are active during a task. They are safe, but they show activity, not exactly what each cell is doing.

  • Stimulation

    Electrical stimulation of parts of the brain during surgery shows what they control, but it can only be done on patients having surgery.

  • Difficulties

    The brain is complex, protected inside the skull, and has billions of connected neurones. It is difficult to reach, and experiments on healthy people or on animals raise ethical issues.

Treating damage to the nervous system (Higher tier)

Damage to the brain and the rest of the nervous system is hard to treat.

  • Limited repair

    Neurones in the brain and spinal cord have a very limited ability to repair themselves, so damage is often permanent.

  • Irreversible damage

    A stroke or a head injury can destroy neurones, or damage the tissue around them, and the lost functions may not return.

  • Difficult access

    Parts of the brain are deep inside the skull, so operating is risky and can cause more damage to surrounding tissue.

  • Spinal injuries

    If the spinal cord is cut, impulses cannot cross the injury, and the person can lose movement and feeling below it.

Case study

Phineas Gage

In 1848 an iron rod passed through the front of the head of a railway worker called Phineas Gage. He survived, but people who knew him said his personality was changed. The case was one of the first pieces of evidence that the front of the brain has a role in personality. It also shows the problems with evidence from a single case: nobody could measure exactly what was damaged, or how Gage was before.

1848 When the accident happened
One person A case study cannot prove a general rule

The big idea

The brain is divided into regions with different functions, and its complexity, the ethical limits on studying it and the very limited repair of nerve tissue make brain research and treatment difficult.

The brain

The brain

  • Cerebrum

    • thought
    • memory
    • language
    • voluntary movement

  • Cerebellum

    • coordination and balance

  • Medulla

    • heart rate and breathing

  • Hypothalamus

    • temperature and water balance

  • Pituitary

    • master gland
    • releases hormones

Summary and exam focus

  • The cerebrum controls conscious thought, memory, language and voluntary movement.
  • The cerebellum coordinates movement and balance.
  • The medulla controls the heart rate and breathing.
  • The hypothalamus controls body temperature and water balance, and the pituitary gland releases hormones.
  • (Higher tier) The brain is hard to investigate because it is complex, difficult to reach and ethical issues limit experiments.
  • (Higher tier) Damage to nerve tissue is hard to treat because neurones repair poorly and the damage is often irreversible.

Exam focus

Describe the functions of the cerebellum, the medulla and the hypothalamus. (3 marks) (3 marks)

Give one clear function for each region: the cerebellum coordinates movement and balance, the medulla controls heart rate and breathing, and the hypothalamus controls body temperature and water balance.

Key terms

The words this lesson expects you to use. Each one is linked from the first place it appears above.

Cerebrum
The largest part of the brain, which controls thought, memory, language and voluntary movement.
Cerebellum
The part of the brain that coordinates movement and balance.
Medulla
The part of the brain that controls the heart rate and breathing.
Hypothalamus
The part of the brain that controls body temperature and water balance.
Pituitary gland
The gland attached to the hypothalamus that releases hormones.
Case study
A detailed study of one person or a small group.
MRI scan
A scan that shows which regions of the brain are active.
Spinal cord
The column of nervous tissue that joins the brain to the body.

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