The Human Brain (OCR A Level Biology): Revision Note

Exam code: H420

Last updated

The Human Brain

  • The brain, alongside the spinal cord, is part of our central nervous system (CNS)

  • The brain is made of billions of interconnected neurones and is responsible for controlling complex behaviours

  • Within the brain are different regions that carry out different functions

  • These regions include:

    • The cerebrum

    • The hypothalamus

    • The pituitary gland

    • The cerebellum

    • The medulla oblongata

The-Brain-Structure, downloadable AS & A Level Biology revision notes

The regions of the human brain

The cerebrum

  • Largest part of the brain in humans (accounts for about 80% of the total mass of the brain)

  • Carries out a large variety of functions involved with conscious activities, including:

    • Vision

    • Hearing

    • Speech

    • Thinking

    • Memory

  • Consists of five lobes

  • Divided into two halves, known as the cerebral hemispheres

    • The hemispheres are joined together by a band of nerve fibres, known as the corpus callosum

    • The right hemisphere controls the left side of the body and the left one controls the right side

  • Has a thin outer layer known as the cerebral cortex or 'grey matter'

    • The cerebral cortex consists of the cell bodies of neurones

    • It is highly folded, which increases its surface area and allows it to contain a greater number of neurones

    • With more neurones in the brain, more connections between neurones can be made

    • This is important, as the more connections between neurones in the brain, the greater the ability of the brain to carry out more complex behaviours

  • Beneath the cerebral cortex or grey matter layer is the 'white matter'

    • The white matter consists of the myelinated axons of neurones

Brain cross-section, downloadable AS & A Level Biology revision notes

A cross-section of the brain showing regions found within the cerebrum.

The hypothalamus

  • Area in the middle of the lower part of the brain

  • It is found just above the pituitary gland (which it is connected to)

  • Monitors the blood as it is flowing through it and in response, releases hormones (involved in homeostasis) itself or stimulates the pituitary gland to release certain hormones

  • Main functions include:

    • Regulating body temperature - by monitoring blood temperature and initiating a homeostatic response if this temperature gets too high or too low

    • Osmoregulation - by monitoring how concentrated the blood is and if it gets too concentrated, stimulating the posterior pituitary gland to release anti-diuretic hormone (ADH), which causes increased water retention in the kidneys. The hypothalamus also generates a feeling of thirst, causing us to increase our water intake

    • Regulating digestive activity - controls the secretion of enzymes in the gut and peristalsis. The hypothalamus also generates a feeling of hunger, causing us to increase our food intake if blood nutrient concentrations get too low

    • Controlling endocrine functions - the hypothalamus releases chemicals that cause the pituitary gland to release certain hormones that control a variety of processes (e.g. metabolism, growth and development, puberty sexual functions, sleep, mood)

The pituitary gland

  • At the bottom of the brain, below the hypothalamus

  • Produces a range of hormones

    • Some of these directly influence and regulate processes in the body but some stimulate the release of further hormones from specific, remote locations in the body (e.g. from other glands)

  • Divided into two sections: the anterior pituitary and posterior pituitary

    • Anterior pituitary - produces and releases certain hormones

    • Posterior pituitary - stores and releases hormones produced by the hypothalamus (e.g. ADH and oxytocin)

The cerebellum

  • Lies below the cerebrum

  • Controls motor coordination

    • This includes balance

    • Balance is a highly complex function that requires coordination between multiple parts, including the eyes, semicircular canals in the ears, and many muscles

  • Functions only subconsciously (i.e. all of the actions it controls are involuntary)

The medulla oblongata

  • Also known as the medulla

  • Found at the very base of the brain, where it joins the spinal cord

  • Contains three 'centres' that control different functions:

    • The cardiac centre - controls heart rate

    • The vasomotor centre - controls blood pressure by controlling the contraction of smooth muscles in arteriole walls

    • The respiratory centre - controls breathing rate (contains an inspiratory centre and an expiratory centre)

👀 You've read 1 of your 5 free revision notes this week
An illustration of students holding their exam resultsUnlock more revision notes. It’s free!

By signing up you agree to our Terms and Privacy Policy.

Already have an account? Log in

Did this page help you?

Download notes on The Human Brain