Coordination

• Nervous system


  Faster, electrical impulses moving through neurones, rapid and short duration of action, localised action, involuntary action: receptors in sense organs, voluntary: brain
• Hormonal system / endocrine


  Slower, chemical messenger traveling in blood, slow and has long duration of action, wide spread action, endocrine gland
• Why we need an endocrine system?
• Why we need to have a reflex action?
• Composition of the nervous system

  CNS (brain and spinal cord), PNS (nerves branching from CNS including sensory and motor neurones)
• Sense organ


  Group of receptor cells that detect a specific stimulus to allow a response to this specific stimuli
• Sensitivity


  Ability of a living organism to detect a stimulus (internal or external) and show a response
• Nerve cell (neurone)


  • Cell body (nucleus, cytoplasm), dendrites (pick up electrical signals from nearby neurones), axon (carry impulses away from cell body), myelin sheath (made from fats and proteins acting as electrical insulator to speed up electrical impulse transmission), motor end plates/nerve terminal
• How the structure of the neuron is related to its function

  Transmit nerve impulses over a long distance, 2. Dendrites pick up electrical signals from nearby nerve cells, 3. Axon carry impulses away from neurone, 4. Mitochondria site of aerobic respiration to release energy for transmission of electrical impulses, 5. Myelin sheath acting as electrical insulator, 6. Vesicles release neurotransmitters across synapse
• Reflex action


  Stimulus involving change in environment, 2. Receptors in sense organs, 3. Receive stimulus and change to electrical/nerve impulse, 4. Sent across sensory neurone to relay neurone in CNS, 5. Across synapse by diffusion of neurotransmitters, 6. Motor neurone carry impulse away from CNS, 7. To effector (muscle or gland) to carry a response
• Types of neurones


  • Sensory, Relay, Motor
• Relay neurone


  No myelin sheath to slow down nerve impulse transmission to allow modification of message
• Stimulant drug


  Increases neurotransmitters, blocks enzyme
• Depressant drug


  Decreases stimulation with neurotransmitters, blocks the receptors
• How electrical impulses move across a synapse

  Electrical impulse reaches end of presynaptic neurone, 2. Vesicles containing neurotransmitters move to end and fuse with presynaptic membrane, 3. Release neurotransmitters, 4. Neurotransmitters diffuse across synapse, 5. Bind to receptors on postsynaptic neurone, 6. Trigger nerve impulse in postsynaptic neurone
• Why synapse acts as a one-way valve

  1. Neurotransmitters produced on one side, 2. Receptors found on surface of second neurone
• Function of synapse


  • Slow down nerve impulse transmission to allow modification of message, 2. Ensures impulses move in one direction, 3. Junction between two neurones to allow transmission of nerve impulses
• Voluntary action


  No automatic action, involves conscious decision by brain, slower, starts in brain, ends in effector (muscle/gland), same stimulus shows different response
• Involuntary action


  Automatic action, doesn't involve conscious brain decision, faster, initiated by stimulating receptors in sense organs, ends at effector (muscle or gland), same stimulus leads to same response
• Parts of the eye

  • Cornea, Pupil, Lens, Suspensory ligaments, Ciliary muscle, Sclera, Choroid, Retina, Optic nerve, Fovea, Blind spot

  
• Cornea


  • Transparent to allow passage of light, most light is refracted
• Aqueous humor


  Watery fluid to support the cornea
• Iris/Pupil


  • Iris is a muscle, the colored part of the eye, controls/changes size of pupil to regulate amount of light reaching retina
• Lens/Suspensory ligaments and ciliary muscles

  • Lens refracts light (fine focus), suspensory ligaments and ciliary muscle together change convexity (curvature) of lens to allow accommodation (adjusting near and far objects)
• Sclera


  • Tough outer layer to protect eye against damage
• Vitreous humor


  Fluid jelly-like structure keeping the eyeball in shape
• Choroid


  • Dark layer that causes pupil to appear dark (no light reflection) to allow light to be detected by photoreceptors, contains blood vessels that nourish retina cells
• Retina


  • Contains photoreceptors (rods and cones) that convert light into electrical impulses sent to brain through optic nerve, fovea contains highest concentration of cones offering sharpest image, blind spot has no light sensitive cells so light falling on it is not detected

  
• Pupil reflex


  In bright light: circular muscle contracts, radial muscle relaxes, pupil constricts to allow less light to reach retina. In dim light: circular muscle relaxes, radial muscle contracts, pupil dilates to allow more light to reach retina.
• How pupil reflex works

  Light rays fall on retina detected by photoreceptors, 2. Send impulses across sensory neurone in optic nerve, 3. To relay neurone in brain, 4. To motor neurone, 5. Which send impulses to effector (iris muscle) to carry a response

  
• Read action


  Endocrine gland
• Why we need an endocrine system


  • Last longer time
  • Travel around the body (wide spread action)
  • Less energy because hormones are carried in blood
• Why we need to have a reflex action


  • Fast, involuntary action, automatic, doesn't need a conscious decision by brain
  • Protects the body against mechanical injury
• Composition of the nervous system

  • CNS (brain and spinal cord)
  • PNS (nerves branching from CNS including sensory and motor neurones)
• Sensitivity


  Ability of a living organism to detect a stimulus and show a response
• Structure of a nerve cell

  • Cell body
  • Dendrites
  • Axon
  • Myelin sheath
  • Motor end plates
• How the structure of the neuron is related to its function

  • Transmit the nerve impulses over a long distance
  • Dendrites pick up the electrical signals from the near by nerve cells
  • Axon that carry the impulses away from the neurone
  • Mitochondria site of aerobic respiration to release energy for transmission electrical impulses
  • Myelin sheath acting as an electrical insulator
  • Vesicles that release neurotransmitters across synapse
• Reflex action


  1. Stimulus

  2. Receptors in sense organs

  3. Receive stimulus and change it into electrical impulse/nerve impulse

  4. Sent across sensory neurone to relay neurone in CNS

  5. Across synapse by diffusion of neurotransmitters

  6. Motor neurone carry impulse away from CNS to effector
• Comparison between types of neurones

  • Sensory
  • Relay
  • Motor
• Why relay neurone has no myelin sheath

  • To slow down nerve impulses
  • Myelin sheath acts as an electrical insulator
  • To prevent leakage of ions/loss of impulses