B5

• The human nervous system allows the body to respond to stimuli from the environment and coordinate responses
• The human nervous system consists of receptors, effectors, the central nervous system, and different types of neurones
• Electrical impulses are passed between neurones across the synapse as chemical neurotransmitter
• When a rapid response is required, impulses travel along the reflex arc
• Reacting to Stimuli
• Receptors detect stimuli from the external environment
• Sensory neurones carry electrical impulses from the receptors to the central nervous system (CNS)
• Central nervous system (CNS) consists of the brain and spinal cord
• Motor neurones carry electrical impulses from the CNS to effectors
• Effectors receive electrical impulses from the CNS and respond to the stimuli by contracting a muscle or secreting a hormone
• Synapses
• Synapses are where two neurones join together and use chemicals to transfer the electrical nerve impulses across the gap between them
• An electrical impulse travels along the first neurone to the end
• Neurotransmitter diffuses across the gap and binds to receptors on the second neurone
• This sets off a new electrical impulse that travels along the second neurone
• Reflex Arc
• The body reacts quickly to prevent or limit damage through the reflex arc
• Impulse is sent to a relay neurone in the central nervous system (CNS) instead of all the way to the brain
• Impulse is sent from receptors, down a sensory neurone to CNS, then to a motor neurone to an effector
• The effector produces a quick response to prevent or limit damage, and this response is involuntary
• The Structure of Neurones
• Neurones are specialised to carry electrical nerve impulses around the body
• They have a long axon to carry the impulse over long distances
• Branched at both ends to easily pass signals between them
• Axon is insulated in a fatty sheath to help the impulse travel quickly
• Sensory, motor, and relay neurones all vary slightly due to their different functions
• Investigating human reaction times
• Reaction time is the time taken to respond to a stimulus and can be affected by factors such as age, stress, drugs, and background noise
• Perform experiments to determine how these factors affect reaction time
• Example: Caffeine intake speeds up a person's reaction time
• The brain is a vital part of the central nervous system, responsible for controlling complex behaviours
• The brain is made up of billions of interconnected neurones and has different sections that carry out specific functions within the body
• Brain Structure:

  • The central nervous system is made up of the brain and spinal cord
  • The brain is responsible for all complex behaviour such as consciousness, speech, memory, movement, and breathing
  • Different sections of the brain include:
  • Cerebral cortex: controls intelligence, memory, consciousness, language, and personality
  • Cerebellum: responsible for coordinating movement, balance, and muscle activity
  • Medulla: controls unconscious activities like breathing and keeping the heart beating
• • Pituitary gland: releases essential hormones and controls other glands around the body
  • Hypothalamus: regulates temperature and water in the body
• Scientists study the brain to gain a better understanding of how it works and create new treatments for patients with brain damage and diseases
• Scientists struggle to study the brain due to its delicacy and intricacy, as well as the risk of potential treatments causing more damage
• Methods used by scientists to investigate brain function:

  • Learn from patients with brain damage
  • Use tiny electrodes to electrically stimulate different parts of the brain
  • Use MRI scanners to produce detailed pictures of the active areas of the brain
• Scientists learn from patients with brain damage by looking at the patterns between the specific areas that are damaged and the effect it has on the patient to understand the function of each brain section
• Tiny electrodes can be used to electrically stimulate different parts of the brain, causing different effects in the individual depending on the section stimulated
• MRI scanners are used to produce detailed pictures of the active areas of the brain, helping scientists identify patterns between brain activity and specific tasks or thoughts