Co-ordination and Response

• What does homeostasis involve?


  The balencing of body functions to maintain a 'constant internal enviroment'

  
  

  Conditions in your body need to be kept steady so that cells can function properly. This involves balencing inputs (stuff going into your body) with outputs (stuff leaving)
• Water content


  You need to keep a balance between the water you gain and the water you lose
• Body temperature


  You need to get rid of excess body heat when you're hot, but retain heat when the environment is cold
• Homeostasis is what ___

  Keeps these balenced
• What are some examples of what your body needs to regulate?


  - Body temp

  - Water content
• How do we loss water in the body?


  - The skin using sweat

  - Via the lungs in breaths

  - Via the kidneys as urine
• What does the balance between sweat and urine depend on?

  What you are doing or what the weather is like
• If it is a hot day how will your urine and sweat ratio be?


  - On a hot day or when you are exercising, you will sweat a lot

  - You will produce less urine, but this will be more concentrated (and could hence the deeper colour)

  - You will also lose more water through your breath when you exercise because you breath faster
• If it's a hot day how will your urine and sweat be?


  - On a cold day, or when you're not exercising, you don't sweat as much

  - You'll produce more urine, which will be pale (since the waste carried in the urine is more diluted)
• What is the main organ in regulating body temp?

  Your skin
• What is the average body temp?

  37°C (98.6°F)
• What happens if you are too hot?


  - Lots of sweat is produced (when it evaporates it transfers energy, from your skin to the environment, cooling you down)

  - Hairs lie flat

  - Blood vessels closer to the surface of your skin widen (this is called vasodilation, it allows more blood to flow near the surface, so it can transfer more energy into the surroundings, which cools you down)
• What happens if are too cold?


  - Very little sweat is produced

  - Blood vessels near the surface of the skin (constrict) vasoconstriction (this means less blood flows near the surface, so less energy is transferred to the surroundings

  - You shiver, which increases your rate of respiration which transfer more energy to warm the body, exercise does the same)

  - Hairs stand on end to trap an insulate layers of air which help keep you warm
• Vasoconstriction


  The constriction of blood vessels, which increases blood pressure.
• Vasodilation


  A widening of the diameter of a blood vessel
• What does our nervous system allow us to do?


  React quickly to change sin our environment and prevent harm
• What does CNS mean?

  Central Nervous System
• What does the CNS contain?


  - Brain

  - Spinal cord
• How is the CNS linked to cells?

  Using neurones
• How does the nervous system send messages?

  As electrical impulses
• What prevents you from getting injured?


  Reflex actions (reflex arcs) they are automatic
• What is a reflex action?


  - An automatic response is something you don't think about

  - An change in environment like hot or cold
• What detects heat?


  Receptors
• Neurone


  A specialised cell
• How are nerves joined?


  - Your nerves are not joined up directly to each other

  - There are gaps between them called synapses

  - The electrical impulse cannot jump across a synapse so a chemical called a neurotransmitter is released which diffuses across the synapses
• Synapse


  A junction between 2 neurones
• Receptors


  Specialised cells that detect stimuli
• Sensory neurone


  This carries the nerve impulse from the receptor to the central nervous system
• Motor neurone


  Carries the nerve impulse from the central nervous system to an effector
• Reflex


  An automatic response to a stimulus that doesn't involve a conscience thought
• Relay neurone


  Connects a motor and sensory neurone in the central nervous system and is involved int he reflex arc
• Stimulus


  Changes in the enviroment
• Effectors


  Carry out responses and are either muscles or glands
• Central nervous system


  The brain and spinal cord
• Nerve


  A bundle of neurones
• Nerve impulse


  Electrical message that passes along a neurone
• What are the part of an eye?


  - Aqueous humour

  - Blind spot

  - Ciliary muscle

  - Choroid

  - Fovea

  - Iris

  - Optic nerve

  - Lens

  - Retina

  - Sclera

  - Suspensory ligaments

  - Vitreous humour
• Aqueous humour


  Watery liquid filling the front of the eye
• Blind spot


  Point where the optic nerve attaches to the eye, no light sensitive cells here
• Ciliary muscles


  Changes the thickness of the lens when focusing