Edexcel A (SNAB) A Level Biology:复习笔记8.2.1 Brain: Structure & Function

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

 

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