Neurones in the Brain (DP IB Biology)

Perception of Pain

• Pain receptors (nociceptors) are sensory receptors

• These receptors have free nerve endings which are unencapsulated nerve endings

• The exposed dendrites on these nerves have transient receptor potential (TRP) channels which open in response to stimuli which indicate a risk of damaged tissue

• Stimuli might include:

  • High temperature

  • Acid

  • Chemicals e.g. capsaicin in chilli peppers

• Entry of positively charged ions causes the threshold potential to be reached

• An action potential is generated, it moves along the axon of the sensory neurone to the central nervous system

• Nerve impulses then pass through the neurones to the cerebral cortex in the brain, where pain is perceived and a protective response results

• The sensitivity of an organism to these stimuli provides a survival and reproductive advantage

Pain Receptors Diagram

Pain receptors in the skin can respond to a number of different stimuli as the nerve endings are exposed

Interaction of Neurones in the Brain

The cerebrum

• The cerebrum is the largest part of the brain in humans (accounts for about 80% of the total mass of the brain)

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

  • Vision

  • Hearing

  • Speech

  • Thinking

  • Memory

• The cerebrum is divided into two hemispheres, each of which have 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

    • These behaviours that result from a combination of complex pathways, are called emergent properties 

  • It is in this part of the brain where interactions between neurones lead to consciousness

  • This idea of consciousness incorporates qualitative perception of feelings associated with colour, temperature, sound as well as communication which results in a complex awareness of the environment

• The structure and function of the brain as an organ is covered in more detail here