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• Homeostasis


  The regulation of conditions inside the body to maintain a stable internal environment in response to changes in both internal and external conditions
• Cells in the body need certain conditions to function properly, such as not being too hot or too cold, not being too acidic or too alkaline, and having a good supply of glucose and water
• The body regulates everything and makes sure that everything is kept around the right levels
• Temperature and glucose levels do fluctuate, but only within small bounds
• If changes are taking place outside of the body

  The body can still maintain its internal environment
• Automatic control systems


  • Receptors which detect a change
  • Coordination centres such as the brain or spinal cord which interpret the change and decide what needs to be done
  • Effectors which carry out the change, such as muscles or glands
• The nervous and endocrine systems are used to send signals between the different components of the automatic control systems
• Nervous system


  Sends fast and precise electrical impulses through nerves, allowing for quick responses
• Endocrine system


  Relies on hormones released into the bloodstream, which are slower, longer-lasting, and more generalized than the nervous system
• Negative feedback


  The mechanism by which the automatic control systems work, decreasing or increasing the level of something to return it to normal
• Negative feedback mechanism


  1. Receptors detect a change

  2. Coordination centres interpret the change and send signals to effectors

  3. Effectors carry out a response to return the level to normal

  4. If the level goes too far in the opposite direction, the process repeats in the other direction
• Homeostasis is the overall process of maintaining a stable internal environment for the body
• Nerve cell


  Also called a neuron
• Adaptations of a Nerve cell

  • Long
  • Thin
  • Lots of branch connections to either end
  • Adapted to carry electrical impulses from one point to another
• Synapse


  Connection between nerve cells where electrical impulses are converted to chemical signals to pass between cells
• Nerve cell communication


  1. Electrical impulse hits end of nerve

  2. Causes release of chemicals

  3. Chemicals diffuse across gap to next nerve cell

  4. Triggers another electrical impulse

  5. Electrical impulse continues along new neuron
• Central nervous system


  • Made up of brain and spinal cord
  • Where 'thinking' takes place
  • Takes in sensory information, decides what to do, sends out orders to the body
• Sensory neurons


  Carry information from receptors all over the body to the central nervous system
• Motor neurons


  Carry impulses from the central nervous system to effectors (muscles or glands)
• Reflex arc


  Nerve pathway that underlies unconscious reflexes
• Reflex arc


  1. Stimulus detected by receptor cells

  2. Sensory neuron carries impulse to spinal cord

  3. Relay neuron transfers impulse to motor neuron

  4. Motor neuron carries impulse to effector (muscle) to cause movement
• Brain


  Made up of billions of interconnected nerve cells, holds all of our thoughts and memories, responsible for all of our complex behaviors
• Brain


  • Made up of different regions
  • Each region performs different functions
• Central nervous system


  Brain and spinal cord
• Cerebral cortex/cerebrum


  Responsible for consciousness, intelligence, memory, language, vision, hearing
• Cerebral hemispheres


  Left hemisphere controls right side of body, right hemisphere controls left side of body
• Cerebellum


  Responsible for controlling balance and muscle coordination
• Hypothalamus


  Involved in regulating body temperature and sending signals to pituitary gland
• Brain stem


  Connects brain to spinal cord, contains medulla which controls unconscious activities like breathing and heartbeat
• How scientists study the brain

  1. Study people with brain damage

  2. Electrically stimulate different parts of the brain

  3. Use brain scanning techniques like CT, PET, MRI
• Brain scanning techniques like CT scans, PET scans, and MRI scans can measure brain activity and damage
• Difficulty in treating the brain


  • Wide range of things that can go wrong
  • Brain is encased in skull and surrounding tissue is fragile
  • Brain is complex and not fully understood
• Eye structure


  • Cross section of the eye
  • Light hits the cornea
  • Cornea is transparent with no blood vessels
  • Cornea refracts light
  • Iris controls pupil size
  • Pupil allows light to pass through to the lens
  • Lens refracts light and can change shape
  • Retina has cone cells for color vision and rod cells for low light black and white vision
  • Fovea is a spot on the retina with only cone cells for clearest vision
  • Optic nerve transmits impulses from receptor cells to the brain
• Iris reflex


  1. Pupil constricts in bright light

  2. Pupil dilates in low light

  3. Circular muscles in iris contract to constrict pupil

  4. Radial muscles in iris contract to dilate pupil
• Bright light conditions


  Pupil constricts to prevent retina damage
• Low light conditions


  Pupil dilates to allow more light in
• Constricted pupil is called pupil constriction
• Dilated pupil is called pupil dilation
• "Cornea"


  "The outer, transparent layer of the eye with no blood vessels. It refracts light as it enters the eye."
• "Iris"


  "The colored part of the eye that surrounds the pupil. It controls pupil size to regulate the amount of light entering the eye."