The nervous system

• Homeostasis is the maintenance of a constant internal environment.
• What do our bodies need to regulate?

  • Water levels
  • temperature
  • glucose levels
  • salt concentration
  • oxygen and carbon dioxide levels
• What factors might affect homeostais?

  • Strenuous exercise
  • extreme climates
• Thermoregulation is the process of keeping the body at a constant temperature.
• Bird and mammals can:

  • control their own internal body temperature
  • enzymes work best at 37 degrees
  • lower temperatures = slower chemical reactions
  • higher temperatures = speed up reactions
• Purposes of the Nervous System:

  • Enables you to control your body
  • provide you with feedback about the world
• The components of the nervous system are the brain, spinal cord, and nerves.
• The brain and the spinal cord make up the central nervous system
• Nerve cells make up the peripheral nervous system
• Diagram of nerve cell

  Its adaptations include: long axons to carry information from one part of the body to another, branches/ dendrites which makes a lot of connections, an insulated axon is to speed up impulses

  
• Synapse are the places where neurons connect and communicate with each other
• Sense organs contain receptors that are sensitive to stimuli
• Receptors are found in the sense organs and detect a stimulus (a change in the environment)
• Receptors are often specialised cells
• Electrical impulses are sent along neurons (nerve cells) which connect with other neurons in the whole nervous system
• Stimulus (change) detected by receptors on the sense organ
• Receptors are there to help you detect and know a change in your environment. They then send that message to the nerve cells which then gets sent to your brain.
• Stimulus: a detectable change in the internal or external environment that trigger a response
• Impulse: the electrical signal transmitted along a nerve fibre
• Receptor: this is a cell that can detect change in the external and internal environment
• Sensory neurons transmit nerve impulses to the spinal cord and brain from all over the body (sense organs)
• Motor neurons carry impulses away from the brain and spinal cord to the muscles or glands
• Relay neurons carry messages from one part of the CNS to another
• Stimulus -> receptors -> sensory neurons -> CNS -> motor neurone -> effector -> response
• The nervous system consists of two main parts, the central nervous system (CNS) which includes the brain and spinal cord and the peripheral nervous system (PNS), which includes nerves.
• Reflex actions are automatic and rapid; they do not involve the conscious part of the brain
• Where two neurones meet there is a small gap, a synapse
• At the synapse elctrical impulses are translated into chemical messengers in order to cross the gap
• An electrical impulse travels along the first neuron. This triggers the nerve ending of a neurone to release chemical messengers, called neurotransmitters. These chemicals diffuse across the synapse (the gap)
• Conscious actions

  1. Receptors in your skin detect a stimulus
  2. The impulse is the carried by sensory neurones to the spinal chord
  3. Another sensory neurone carries the signal to the brain
  4. The brain decides to move away the hand
  5. This impulse is sent by motor neurones to the hand muscles (the effectors) via the spinal chord
  6. Which then moves the hand away
• Reflex actions

  1. Receptor
  2. Sensory neurone
  3. Relay neurone in the spinal chord
  4. Motor neurone
  5. Effector
• Neurone communication diagram

  
• What is the method for measuring a person's reaction time?

  • Person 1 sits on a stool with good posture.
  • Person 1 places their dominant arm across the table.
  • Person 2 holds a ruler vertically between Person 1's thumb and first finger.
  • Person 2 drops the ruler at a random time.
  • Person 1 catches the ruler as quickly as possible.
  • Measurement is recorded at the top of Person 1's thumb.
  • The test is repeated several times to calculate a mean.
• What is the role of Person 1 in the reaction time measurement?

  Person 1 measures their reaction time by catching the ruler
• What should the zero centimeter mark of the ruler be positioned between?

  Person one's thumb and first finger
• Why is it important for Person 1 to have a short rest between tests?

  To ensure accurate measurement of reaction time
• What is the independent variable in this reaction time experiment?

  The person having their reaction time tested
• What is the dependent variable in this reaction time experiment?

  The reaction time measured
• What are control variables in the reaction time experiment?

  • Distance between thumb and first finger should be constant.
  • Ruler measurement should always be at the top of the thumb.
  • Room conditions (lighting and background noise) should remain the same.
• What could happen if control variables are not maintained in the experiment?

  It could affect the dependent variable, which is the reaction time