Nervous Control (SQA National 5 Biology): Revision Note

The nervous system

• The nervous control system coordinates the body’s responses to internal and external changes by transmitting electrical impulses through specialised nerve cells, ensuring that the body reacts quickly and appropriately to different stimuli

  • The response to a stimulus can be rapid, e.g. action from a muscle, or slow, e.g. the response from a gland

• The human nervous system consists of:

  • Central nervous system (CNS) – the brain and spinal cord

  • All other nerves in the body that extend to and from the CNS

• Information is sent through the nervous system as electrical impulses – electrical signals that pass along nerve cells known as neurons

• A bundle of neurons is known as a nerve

The brain

• The brain, alongside the spinal cor,d is part of our central nervous system

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

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

Regions of the brain

• Scientists have discovered that different regions of the brain seem to be responsible for controlling different functions. These regions include:

  • The cerebrum: this is the largest part of the brain, which is divided into two hemispheres. It’s highly folded and is responsible for higher-order processes such as intelligence, memory, consciousness and personality

  • The cerebellum: this is underneath the cerebral cortex and is responsible for balance, muscle coordination and movement

  • The medulla: this controls unconscious activities such as heart rate and breathing

Neurons

• There are three main types of neurons: sensory, inter and motor neurons

  • Sensory neurons carry impulses from sense organs to the CNS

  • Inter neurons (also known as relay neurons) are found inside the CNS and connect sensory and motor neurons; they process the information from the sensory neurons

  • Motor neurons carry impulses from the CNS to effectors (muscles or glands), where a response can occur