section 6 - coordination and response

• Neurones types


  • Sensory
  • Relay
  • Motor
• Reflex arc


  1. Receptors send impulse through the sensory neurone to the relay which is in the central nervous system

  2. Neurotransmitters diffuse at the synapse from relay to motor and the impulse is sent through the motor

  3. The motor send the impulse to the effector
• The eye


  • Conjunctiva - Protects the eye
  • Cornea - Bends/refracts light
  • Sclera - Protects the eye
  • Iris - Controls diameter/size of the pupil
  • Pupil - Controls amount of light entering the eye
  • Lens - Becomes rounder/more curved/thicker
  • Optic nerve - Carries impulse from the receptor to the brain
  • Ciliary muscle - Contract
  • Suspensory ligaments - Relax
  • Retina - Contains light receptors and connects to the optic nerve
• The Iris reflex


  1. Bright light - Radial muscles relax, circular muscles contract, pupil small, amount of light entering the eye low

  2. Dark/dim light - Radial muscles contract, circular muscles relax, pupil big, amount of light entering the eye high
• Homeostasis


  The maintenance of a constant internal environment
• The skin


  • Too hot - Sweat gland produce sweat, heat loss by evaporation, blood vessels vasodilation and closer to the skin/surface heat loss by radiation, hair follicle flat so not insulating layer
  • Too cold - Less sweat, so less heat loss, blood vessels vasoconstriction and away from the skin/surface so less heat loss, hair follicle erect/stand up so an insulating layer of air, shivering so heat energy produced in respiration in muscles
• Hormones


  • Adrenaline - Produced in adrenal glands above the kidneys, Prepare for fight or flight, Increases heart rate and pupil dilation
  • Insulin - Produced in pancreas, Control blood glucose level, Stimulates liver to turn glucose into glycogen for storage
  • ADH - Produced in pituitary gland in the brain, Controls water content, Increases permeability of the kidney tubules to water
  • FSH - Produced in pituitary gland in the brain, Female sex hormone, Causes egg in ovary to mature, Stimulates ovaries to produce oestrogen
  • LH - Produced in pituitary gland in the brain, Female sex hormone, Stimulates egg release from ovary
• Differences between endocrine/hormonal and nervous system


  • Endocrine/hormonal system - Slow speed, Long lasting effect, Widespread target
  • Nervous system - Fast speed, Short lasting effect, Specific target
• Shoots


  • Phototrophic - Positively
  • Geotrophic - Negatively
• Roots


  • Phototrophic - Negatively
  • Geotrophic - Positively
• Auxin


  For phototrophic auxin moves to shaded side and cause cell elongation. Shoots grow towards light. For geotrophic auxin goes to lower side of roots. Roots grow towards water and minerals.
• Response to light


  • Animal - Short duration, Involves eyes, Nervous system
  • Plant - Long duration, Involves auxin, Hormonal/endocrine system