Biology 2.5

• What does the central nervous system consist of?

  brain and spinal cord
• What is the nervous system made up from

  Brain

  spinal cord

  nerves (neurones)
• Why are some parts of the nervous system specialised

  For receiving a stimuli
• what is a stimulus?

  a change in the environment
• Give examples of a stimuli

  Chemicals

  temperatures

  light

  sound

  waves
• What is meant by the term sense organs?

  Sense organs are groups of receptor cells that detect a stimuli
• Examples of sense organs?

  Eyes, ears, nose, tongue, skin
• In what Form does information along neurones

  Electrical impulse
• What are neurones?

  •Nerve cells adapted to quicky transmit nerve impulses 

  They are the functional units of the nervous system
• what is a nerve

  Group of neurones that transfer information as electrical impulses in the nervous system
• What is the function of the nervous system

  Allows an organism to rapidly react to environmental and internal changes
• What is the function of the sensory neurones

  Carry impulses from sense organs to the central nervous system
• What is the function of the motor neurons

  •Carry impulses from the central nervous system to the effectors
• The scence , sense organ and stimuli

  Smell nose Chemicals

  taste tounge chemicals

  touch Skin temp/pressure

  sight Eyes light

  hearing Ears sound waves
• What are the properties of the reflex actions

  Fast

  automatic

  protective
• 3 examples of a reflex actions

  Withdrawal refelx (hot object)

  pupil reflex (pupil going smaller)

  blink reflex
• What does a reflex arc involve

  Stimulus

  receptor

  coordination

  effector

  response
• In what order is the reflex arc

  1.Stimulus

  2.receptor

  3.sensory neurone

  4.relay neurone

  5.synapse

  6.spinal cord

  7.Motor neurone

  8.effector
• Describe pathway in reflex action

  receptor
• Why is a reflex action automatic

  Impulses do not travel through the neurone sin the brain
• Why is a reflex action fast

  Finish
• Why is a reflex action protective

  Finish
• What is the blind spot?

  Where the optic nerve connects to the retina.

  There are no light sensitive cells here.
• What is the cornea

  Tough, clear and allows light to enter and refracts light
• What is the pupil

  Hole in the center of the iris that allows light to enter
• What is the sclera

  protective, tough white outer coat of the eyeball
• What is the iris?

  Muscle that controls how much light enters the eye
• What is the choroid?

  composed layers of blood vessels that nourish the back of the eye
• What is the retina

  Light sensitive layer at the back of the eye which detects images focused by the cornea and the lens
• What is the lens

  Clear, flexible structure makes an image on the eyes retina. It can change shape to focus on objects
• What is the optic nerve?

  the bundle of nerve fibres that carry impulses from the retina to the brain
• What is homestatis

  The maintenance of a constant internal environment
• Why does the body need to be kept at a constant level

  To make sure that chemical reactions are taking place efficiently
• What type of chemicals help to ensure that optimum conditions within the body

  Hormones
• What are hormones

  Chemical messengers found in the blood
• why is homeostasis used

  To ensure that chemical reactions are taking place efficiently
• what levels in the body need to be kept constant

  Temperature

  ph

  water levels

  glucose levels
• Why must body temperature be controlled?

  finish
• What is the optimum temperature for enzymes in the body

  37•
• High blood pressure

  blood level rises