B1.2 Coordination and Control

Responding to Change
1. Your nervous system allows you to react to what is around you, carrying electrical signals from 1 to 120 metres per second
2. The nervous system
  1. stimuli is picked up by receptors
  2. Receptor cells are like animal cells
    1. Contain a nucleus, cytoplasm and cell membrane
    2. Clustered together in sense organs (eg. nose)
3. How the Nervous System works
  1. 1) Sensory receptor detects stimulus
  2. 2) impulses go along neurons which are found in bundles (nerves)
  3. 3) reaches the Central Nervous System (brain and spinal chord)
  4. Sensory Neurons - cells carrying signals from organs to CNS
  5. Motor Neurons - cells which carry impulse from CNS to body
  6. effector organs - respond (muscles to contract or glands to secrete chemicals)
  7. receptor, sensory, CNS, motor, effector
    1. Reflex arc
Reflex Actions
1. Reflexes
  1. to keep us from harm
  2. Sensory, relay and motor neuron
  3. The impulses bypass the concious brain area
  4. Short a distance as possible
2. Synapses
  1. junctions between nerves
  2. Impulses have to travel synapses in a chemical
  3. stimulus, receptor, coordinator, effector, response
3. You only know about the action after it is done
Hormones and The menstrual Cycle
1. Glands secrete hormones and your blood carries them to organs which they regulate
2. The Menstrual Cycle
  1. The pituitary gland and ovaries control it
  2. 28 days
  3. Day 1) Lining thickens to support baby, egg starts to mature.
  4. Day 14) egg matures and is released from ovary which is ovulation, lining stays thick
  5. If fertilised, pregnancy takes place, lining provides protection and food for embryo, if not, period occurs
  6. All changes come from hormones.
3. How the menstrual cycle works
  1. FSH stimulate ovaries to produce oestrogen (sex organ)
  2. Follicle Stimulating Hormone (FSH) is secreted by pituitary gland. It makes eggs mature and stimulates ovaries
  3. Oestrogen stimulates the womb to produce lining and limits FSH
  4. There are also Luteinising hormone (LH) and progesterone.
  5. When LH reaches a peak, the egg is released
The Artificial Control Of Fertility.
1. Contraceptive Chemicals
  1. Oral contraceptives contain oestrogen to prevent the eggs from being released
  2. They also prohibit FSH to ensure any eggs don't mature
  3. Too much oestrogen causes high blood pressure and headaches
  4. Some pills contain progesterone which causes less side effects
2. Fertility Treatments
  1. 1/6 of women are infertile
  2. Some need more FSH so get drugs
  3. IVF - conception usually takes place in a fallopian tube (between the ovary and the uterus) so if they are damaged the egg can not travel, IVF bypasses the tube by inserting the embryo into the womb. The woman gets FSH to mature the egg then LH to release mature ones. It is expensicve
Controlling Conditions
1. Homeostasis is the balancing act on your internal environment
2. Controlling water and ions
  1. water moves in and out of your body cells via osmosis. How much it moves depends on the number of mineral ions and the amount of water. Too much or too little water damages it.
  2. You take them in when you eat or drink and you lose it in your breath, sweat and urine (produced in kidneys)
  3. Kidneys change salt and water concentration in urine. Concentration of urine in your kidneys is controlled by nerves and hormones
3. Controlling Temperature
  1. Core must be 37°C as enzymes work best here. Only a few up or down causes you to die as enzymes denature
  2. Sweat to cool down and shiver to heat up. Nervous system controls it.
  3. Below 35°C causes hypothermia. Above 40-42°C hyperthermia.
4. Controlling Blood Sugar
  1. Digestion causes high glucose so your pancreas keeps it constant
  2. Pancreas provides constant energy levels to cells
Hormones and the control of plant growth
1. Sensitive to light, water and gravity
2. Plant Sensitivity
  1. When seeds germinate, roots have to grow downwards and shoots up to photosynthesise.
  2. Response to light is phototropism
  3. Response to gravity is gravitropism
  4. Auxins move in the plant to the side which needs to grow most, bending the shoot or the side which needs to grow least, bending the roots
  5. Auxins make shoots grow and inhibits root growth
3. Using Plant Hormones
  1. Used as rooting powder to stimulate growth
  2. High doses make weed killers
Using Hormones
1. Control fertility
2. Identical Plants
3. Weed Killer
4. hormones are effective and generally safe
5. Plant hormones can damage the environment

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B1.2 Coordination and Control

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