response and regulation

• whats the role of the central nervous system in the body

  • detects changes in the environment
  • controls bodys actions
  • coordinates responses by making decisions
• what sense organs 


  groups of special cells called receptor cells that detect changes in the internal or external environment - changes are known as stimuli
• what are stimuli 


  changes in the environment such as light, sound, chemicals, touch and temperature
• how does information from sense organs reach the CNS

  information travels through nerve cells, known as neurones, which are grouped together to form nerves
• what is the central nervous system 


  the brain and spinal cord, which receive and coordinate information from sense organs
• what makes up the nervous system 


  central nervous system and nerves that send out information to muscles to gain a response
• whats an impulse 


  electrical current carrying information along neurones
• what are motor neurones 


  neurones transmitting impulses from the brain to muscles and glands
• what are sensory neurones 


  neurones carrying information from the sense organs to the CNS
• what is reaction time


  duration between a stimulus and the resulting response
• whats a reflex 


  particular type of response to a stimulus
• what are the characteristics of a reflex

  • very rapid response
  • automatic
  • protective
• what are examples of reflexes

  • breathing
  • blinking
  • swallowing
  • sneezing
• whats a receptor 


  organ that detects stimulus
• whats a co ordinator 


  detects signal from a receptor and sends impulse to effector
• whats the effector 


  part of body that produces the response
• what are the stages of reflex

  1. stimulus is received by receptor
  2. an impulse is sent along sensory neurone to spinal cord
  3. impulse moves across the synapse to the relay neurone
  4. relay neurone transmits the signal to the motor neurone
  5. motor neurone stimulates the effector to respond
• why is impulse automatic 


  doesn't go through the brain which is the part of the CNS that makes the decisions
• what do plants respond to

  changes in the environment but responses are slower than animals as plants do not move and the changes involve growth
• what are the growth movements called

  tropisms
• what are the two types of tropisms

  • Phototropism - growth in response to light, positive phototropism is when plant shoots grow towards light, negative phototropism is when roots grow away from light
  • Gravitropism - growth towards or away from the pull of gravity, roots show positive gravitropism and stems show negative gravitropism
• what are tropisms controlled by

  auxins (type of hormone)
• what type of organ is the eye

  sense organ that detects light and sends information about patterns of light it receives to the brain this builds a picture from that information
• whats the retina and its function

  light sensitive inner layer - detects light and some detect coloured light
• whats the optic nerve and its function 


  at the very back of the eye - conveys nerve impulses from these cells to the brain
• whats the blind spot and its functions

  where optic nerve is attached to the eye and there is a gap in the retina, brain fills in gap so you don't have a gap in your vision
• what is sclera and its function

  tough white outer coat - protects the retina
• whats the cornea 


  transparent area of sclera - to let light in
• whats the lens and its functions 


  flexible and changes shape to focus on objects - focuses light onto retina
• whats the pupil and its functions

  gap in the iris which light passes through - adjusted by iris
• what is the iris and its functions 


  coloured part of the eye - can adjust muscles to widen or shrink pupil depending on the levels of light
• whats the choroid and its functions 


  black layer that reduces internal reflection
• what is homeostasis 


  collection of processes that keep certain conditions in the body at a certain level - maintains optimum conditions for chemical reactions in cells
• what are hormones 


  chemical messengers made in certain organs that travel around the im the bloodstream affecting various parts of the body
• what are hormones mainly used for

  medium ter and long term regulation
• what are the main conditions controlled by hormones

  • Temperature - must be kept stable at optimum level for enzymes to work
  • Water Content - to little water causes fluids to concentrate and damage body, to much water dilutes body fluids - concentration of bodily fluids maintained by hormones at safe levels
  • Glucose Concentration - if levels get to high damage can be done to body, essential for glucose levels to be maintained in a safe range
• how do you control blood glucose 


  levels can be reduced by insulin which is a hormone released by the pancreas, this converts soluble glucose inot insoluble glucose stored in the liver
• what is type 1 diabetes

  when body stops producing insulin, possibly due to an over reaction to a virus this leads to the immune system to destroy insulin producing cells resulting in blood glucose levels to rise, if blood sugar levels get to high person can die
• how is type 1 diabetes treated

  • Person has to inject themselves with insulin to replace natural insulin thats not being produced
  • Carefully manage diet to match injected insulin
  • patient has to test blood sugar levels daily to ensure levels aren't to high or low
• what is type 2 diabetes 


  body no longer responding to naturally made insulin - associated with being obese