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Endocrine system
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- 2. • Messages canbe sent using the nervous system – electrical impulses • Or the Endocrine system – using chemicals • Chemicals called hormones – a chemical substance produced by a gland, carried by the blood, which alters the activity of one or more target organs and is then destroyed by the liver
- 3. Important Endocrine Glands They havea good blood supply, capillaries running through them. Hormones released directly into blood. *other glands don't do this....eg. Saliva glands don't secrete saliva into blood. Instead saliva is secreted into saliva ducts. *Endocrine glands don't have ducts....ductless glands.
- 4. Endoncrine glands release hormone directly intoblood Hormone is carried around all parts of the body (dissolved in plasma) Blood is carrying many hormones Only affects target organs Target Organs: "an organ that is affected by a hormone"
- 5. Adrenaline • Produced byAdrenal Glands (x2) • When we are excited/frightened our brain sends impulses along nerves to adrenal gland. • This makes adrenal gland secrete adrenaline into blood • Affects organs (fight or flight) - heart beats faster - increases breathing - more oxygen supplied to brain and muscles More energy for fighting or running away
- 6. Other effects ofAdrenaline • Blood vessels in skin and digestive system contract (pale and ' butterflies in stomach' ) • Reason: to provide as much blood as possible for the brain • Pupils in the eye widen. To allow more light in. Why? • Liver releases glucose into the blood. To release more energy from it (respiration)
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- 8. • Plants oftenrespond to stimuli by growing towards or away from the stimulus. • Changing their direction of growth • Away = negative response / Towards = positive response • Tropism = growth response by a plant • Gravitropism = a response in which plants grow towards or away from gravity • Phototropism = a response in which plants grow towards or away from the direction of the light
- 9. • Shoots usuallygrow towards the light. • Roots usually don't respond to light (some grow away) • Shoots usually grow away from the pull of gravity • Roots usually grow towards it • Reasons: shoots need light so must grow towards it – more light, better photosynthesis • Roots need to grow into the soil to anchor the plant and absorb water/minerals
- 10. Plant Hormones • Plantsdon't have complex sense organs (like mammals) • Receptor is in tip of shoot. See Experiment
- 11. Auxin • A planthormone that causes plant cells to elongate • Produced in the tip of the shoot. Cells on the shady side grow faster than cells on the bright side. Causes bending towards light. • Even light causes shoot to grow straight upwards.
- 12. Auxin affected byGravity • Potted plant on its side in a dark cupboard • Shoot bends to grow upwards. • Auxin tends to gather on the under side of the plant causing it to grow upwards Auxin gathers here
- 13. Auxin has oppositeeffect in roots
- 14. Etiolation • Plants growin darkness. • Auxin spread evenly around tip...causes plant to grow rapidly upwards • Results in very tall thin plant. • However: chloroplasts don't develop properly in darkness. • So, plant is yellow and weak. With leaves spaced apart. • If plant then receives light, will begin to develop chloroplast and grow normally. • If continued darkness, plant will die because it cannot photosynthesise.
- 15. Weedkillers • Often madefrom synthetic Auxin • Selective weedkillers. Meaning it causes weeds to grow very fast and die, but doesn't affect grass