Brain: Structure & Function (Edexcel A Level Biology (A) SNAB): Revision Note

Brain: Structure & Function

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

• The brain is made of billions of interconnected neurones 

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

Different regions of the brain carry out different functions

• You need to know the functions of the following brain regions

The cerebrum

• The cerebrum is the largest part of the brain in humans, accounting for about 80% of the total mass of the brain

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

  • Vision

  • Hearing

  • Speech

  • Thinking

  • Memory

• The cerebrum is 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

• The cerebrum 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 neurone connections 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

The cerebrum consists of two hemispheres joined by the corpus callosum

The hypothalamus

• The hypothalamus monitors the blood as it flows through the brain and, in response, releases hormones or stimulates the neighbouring pituitary gland to release hormones

  • The hypothalamus plays an important role in some homeostatic mechanisms

• Hypothalamus functions include

  • Regulating body temperature

    • The hypothalamus monitors blood temperature and initiates a homeostatic response if this temperature gets too high or too low

  • Osmoregulation

    • Cells in the hypothalamus monitor the water balance of the blood and releases the hormone ADH if the blood becomes too concentrated

      • ADH increases absorption of water in the kidneys

  • Regulating digestive activity

    • The hypothalamus regulates the hormones that control appetite as well as the secretion of digestive enzymes

  • Controlling endocrine functions

    • The hypothalamus causes the pituitary gland to release hormones that control a variety of processes e.g. metabolism, growth and development, puberty, sexual functions, sleep, and mood

The cerebellum

• The cerebellum coordinates movement

  • This includes balance; a highly complex function that requires coordination between multiple parts, including the eyes, semicircular canals in the ears, and many muscles

The medulla oblongata

• Also known as the medulla

• The medulla contains co-ordination centres that control different functions e.g.

  • The cardiac centre controls heart rate

  • The respiratory centre controls breathing rate