Nerves and Hormones

Nerves and Hormones

1. The Nervous System

   • Sense Organs
     • Detect stimuli
     • Contain receptors
       • Groups of cells sensitive to a stimulus
         • Change stimulus energy in electrical impulses
     • Eyes
       • Stimuli=light
       • Sense=sight
     • Ears
       • Sense=hearing
       • Stimuli=sound
     • Nose
       • Sense=smell
       • Stimuli=Gas Chemical
     • Tounge
       • Sense=Taste
       • Stimuli=Chemical
     • Skin
       • Sense=Touch
       • Stimuli=Pressure, temperature
   • How it works
     • Sensory Neurone
       • Carry electrical impulses from receptors to central nervous system
     • Relay Neurone
       • Signals from sensory neurone to motor neurone
     • Motor Neurone
       • Signals from CNS to effector muscles or glands
     • Effectors
       • Muscles contract in response to nervous impulses
       • Glands secrete hormones
     • CNS
       • Made up of Brain and Spinal Chord

2. Synapses

   • Connection between two neurones
   • Nerve signal transferred by chemicals which diffuse across a gap
     • These chemicals set off new electrical signal in next neurone

3. Controlling Fertility

   • Contraceptive Pill
     • Prevents Pregnancy
     • Oestrogen stops body from producing FSH
     • Artificial hormone levels stop if you forget to use it
     • Pros
       • Made families smaller-prevents hunger issues
     • Cons
       • Destroys eggs
   • IVF
     • FSH Used
       • As many eggs as possible mature
     • Sperm mixed with eggs, fertilised eggs planted in tiny ball of cells
     • Happens in fallopian tube
     • Pros
       • Helps struggling families
     • Cons
       • Expensive
       • Many eggs are killed
     • Helps fertilisation happen

4. Plant Hormones

   • Auxins
     • Controls growth near tips of roots & shoots
     • Responds to light (phototropism) gravity (gravitropism) and moisture
     • Moves backwards to stimulate cell elongation
     • No tip, no auxin
     • Shoots grow towards light and away from gravity
     • Roots grow towards gravity and moisture
   • Uses
     • Selective Weedkillers
       • Only gets rid of unwanted plants
     • Fruit Ripening
       • Helps fruit stay riper for longer-long shelf life
     • Rooting Powder
       • Stimulates Growth
     • Seedless Fruits

5. Homeostasis

   • Keeping internal conditions stable
   • Ion Content
     • Lost in sweat
     • Absorbed into blood
     • Excess should be removed
       • Kidneys remove it
         • Ends up in urine
   • Water Content
     • Lost in sweat
     • Lost in breath
     • Lost in Urine
   • Sugar Content
     • Food puts glucose into the blood
       • Normal metabolism of cells removes it
       • Exercise removes too much
     • Insulin helps you to maintain correct glucose levels
   • Temperature
     • Enzymes work best at 37oC
       • Body tries to maintain this temp
     • Brain acts as a thermostat

6. Reflexes

   • Automatic responses to certain stimuli
   • Reduces chances of being injured
   • Stimulus
     • Receptor
       • Sensory neurone
         • Relay Neurone
           • Motor Neurone
             • Effector
               • Response

7. The Menstrual Cycle

   • Day 1:Bleeding Starts
     • Day 4-: Lining builds up
       • Day 14: Egg Released
         • Day 14-28: Wall Maintained
           • Day 28:Lining breaks down
   • Hormones Involved
     • FSH
       • Produced by pituitary gland
       • Causes egg to mature in ovary
       • Stimulates ovaries to produce oestrogen
     • Oestrogen
       • Produced in ovaries
       • Causes pituitary to produce LH
       • Inhibits further release of FSH
     • LH
       • Produced by pituitary gland
       • Stimulates release of egg around middle of cycle