Coordination

• Tropism


  Movement, in the form of growth, in response to a stimulus.
• Positive phototropism


  Growth towards light
• Negative phototropism


  Growth away from light
• Positive geotropism


  Growth towards gravity
• Negative geotropism


  Growth away from gravity
• Auxin


  Promotes growth in the shoots, inhibits growth in the roots.
• Nervous communication


  Uses neurones, transmitted by electrical impulses through the axon of nerves, fast transmission, short term effect, localised response.
• Hormonal / endocrine communication

  Uses secretary cells, transmitted by hormones through the blood plasma, slow transmission, long term effect, wide spread response.
• What is the benefit of a reflex?

  Results in a quicker response that helps limit harm / damage caused to the body
• Sight

  Organ - eyes

  Receptor - Light receptors (cones and rods)

  Stimulus - Light
• Hearing/balance

  Organ - ears

  Receptor - sound and balance receptors

  Stimulus - Sound (vibrations in air) Movement / position of head
• Smell

  Organ - Nose

  Receptor - smell receptors

  Stimulus - Chemicals in the air
• Taste

  Organ - tongue

  Receptor - taste receptors

  Stimulus - Chemical in food and drink – bitter,

  salt, sweet, sour, savoury
• Touch

  Organ - skin

  Receptor - touch receptors

  Stimulus - Pain, pressure, hot / cold temperatures.
• Coordinated response:

  Sense receptors detect a stimulus. The receptor then changes this ‘stimulus energy’ (light, sound etc) into an electrical impulses. This electrical impulse is then sent to the CNS (coordinator) via the sensory neurone. The CNS processes the electrical impulse. An electrical impulse is sent from the CNS along the motor neurone. The motor neurone transmits the electrical impulse to an effector. The effector (muscle/gland) carries out a response.
• Function of the synapse


  Upon the arrival of an electrical impulse in the first neurone, a neurotransmitter is released.

  The neurotransmitter diffuses across the synaptic cleft/gap and binds to receptors on the second neurone.

  This causes a new electrical impulse to be initiated in the second neurone.
• Conjunctiva


  Lubricates and protects the surface of the eye
• Cornea


  Refracts (bends) light into the eye. Is transparent.
• Pupil


  The hole in the middle of the iris that allows light to pass into the eye
• Iris


  Controls the amount of light entering the eye by controlling the diameter of the pupil
• Lens


  Focuses the light onto the retina
• Retina


  Light sensitive part of the eye consisting of light sense receptors

  called cones (sensitive to colours) and rods (sensitive in dim light).
• Optic nerve


  Carries electrical impulses from the light sense receptors of the

  retina to the brain.
• Focusing on distant objects

  Ciliary muscles relax

  Suspensory ligaments pulled tight

  Lens pulled long and thin

  Lens becomes less convex/curved
• Focusing on near objects

  Ciliary muscles contract

  Suspensory ligaments loosen

  Lens becomes short and fat

  Lens become more convex/curved
• Bright Light

  Circular muscles contract

  Radial muscle relax

  Pupils constrict
• Dim Light

  Radial muscles contract

  Circular muscles relax

  Pupils dilate
• Rise in core body temperature

  Hairs lie flat

  Increased sweating

  Decreased shivering

  Vasodilation (of blood vessels supplying

  capillaries at surface of skin)
• Drop in core body temperature

  Hairs pulled erect

  No sweat

  Increased shivering

  Vasoconstriction (of blood vessels

  supplying capillaries at surface of skin)