structure and function of the nervous system 5.2.1

• eyes sense light
• ears sense sound and pressure
• the nose senses chemicals
• the tongue senses chemicals, pain and temperature
• the skin can sense touch, pressure, pain and tempersture
• features of a light receptor cell include:

  • cell membrane
  • mitochondria
  • nucleus
  • cytoplasm
• a stimulus us a change in the environment
• a sensory neurone sends electrical impulses from the receptors in the sense organs, to the brain (central nervous system)
• the coordinator is the brain and spinal column, also known as the central nervous system (CNS), this processes the information from sensory neurones
• the motor neurone sends electrical impulses from the brain to the muscles and glands (effectors)
• the effector is usually a muscle or gland and responds when it receives a message from the brain
• a receptor is a type of cell that detects changes in the environment
• the central nervous system consists of the brain and the spinal chord only, in mammals, the CNS is connected to the body by sensory neurones and motor neurones
• the path of a nerve impulse:

  1. the stimulus is detected by a receptor
  2. a nerve impulse is passed along the sensory neurone
  3. there is a synapse between neurones
  4. the central nervous system processes the information
  5. the nerve impulse passes along the motor neurone
  6. the impulse reaches the effector (muscle or gland) causing the response
• a neurone is the nerve cells responsible for carrying electrical impulses around the body
• a nerve impulse is when a receptor is stimulated (detects a change) an electrical impulse is generated to record this change and generate a response
• a synapse is the junction between two neurones
• how a synapse works

  1. the electrical nerve impulses cannot cross the synapse
  2. chemicals called neurotransmitters are released, which diffuse across the synapse
  3. the neurotransmitters bind to receptors on the membrane of the next neurone causing a new nerve impulse
• drugs can block the neurotransmitters from binding to the receptor and stopping the impulse in the next nerve and also by binding to the receptor and causing a new impulse =, even when theres no transmitter
• the nervous system enables humans to react to their surroundings and coordinate their behavious