B11

• Thyroxine controls basal metabolic rate, how much oxygen is used by tissues, how brain of growing child develops
• In adults level of thyroxine is stable due to negative feedback
• if there are falling levels of thyroxine sensors in brain detect this and causes increase in amount of TSH released by pituitary gland
• if there are rising levels of thyroxine, sensors in brain detect this and level of TSH falls
• Giberillins are used to end seed dormancy, increase size of fruit and promote flowering throughout year
• Ethene is used to ripen fruit so easier to transport
• If a woman is infertile, artificial FSH can be used as fertility drug as it stimulates eggs in ovary to mature and triggers oestrogen production. Then artificial LH can be used to trigger ovulation
• IVF STEP 1: giving mother FSH to stimulate maturation of several eggs, followed by LH to stimulate ovaries to point of ovulation
• IVF STEP 2: Eggs collected from mother and fertilised by sperm in lab
• IVF STEP 3: Fertilised eggs develop into embryos in special solutions
• IVF STEP 4: When there are tiny balls of cells, embryos are inspected with microscope and healthy ones are selected and then 1 or 2 are inserted into mother's uterus
• Pituitary gland acts as master gland.
• Endocrine glands secrete hormones to provide chemical coordinate and control for body
• Endocrine system is made up of glands that secrete hormones directly into bloodstream, the blood carries hormone to effector or target organ. There are receptors on cell membranes of effector organ which pick up hormone molecule triggering response in cell
• Some hormones are slow acting and have long term effects such as growth hormones and sex hormones
• Some hormones can act very rapidly like insulin and adrenaline
• FSH (follicle stimulating hormone) is secreted by pituitary gland and makes egg mature in their follicles in ovaries and stimulates ovaries to produce hormones like oestrogen
• LH (lutenising hormone) is secreted by pituitary gland and stmulates release of mature egg from ovary then it's levels fall once ovulation has occured
• Plants are sensitive to light and gravity.
• Plant responses are called tropisms
• Phototropism is the response of plant shoots growing towards light
• Gravitropism is the response of roots growing down towards gravity
• Auxin is the hormone that controls phototropism and gravitropism
• Unequal distribution of auxin causes unequal growth resulting in bending of root and shoot
• If light falls on 1 side of shoot, there is more auxin on unlit side and it causes cells on unlit side to increase in length so shoot bends towards light
• If there is too much glucose in blood pancreases produce insulin which causes glucose to move from blood into cells
• In liver and muscles, excess glucose is converted to glycogen for storage and when these stores are full, glucose is stored as lipids eventually leading to obesity
• If blood glucose levels gets too low, receptors in pancreases detect low level and pancreas releases glucagon. Glucagon causes glycogen in liver to change into glucose
• Type 1 diabetes is treated with human produced genetically engineered bacteria which has to be inject into person before meals
• Type 2 diabetes develops when body doesn't respond to its own insulin and obesity is significant factor in development
• Type 2 diabetes can often be controlled by eating balanced diet (reducing amount of carbs in diet), exercise and dieting if you are overweight
• To help type 2 diabetes, doctors can prescribe drugs to treat type 2 diabetes which help insulin work better, help pancreas make more insulin or help reduce amount of glucose you absorb from your gut
• Adrenaline is produced by adrenal glands above kidneys.
• Adrenaline is 'fight or flight' hormone because it is released when you're stressed, frightened or angry
• Ovulation is release of mature egg every 28 days
• If egg isn't fertilised, lining of uterus and egg is shed around 14 days after ovulation
• Each month, eggs begin to mature in ovary and uterus produces a thickened lining ready for pregnancy
• As oestrogen levels rise, production of FSH is inhibited and production of LH is stimulated
• When LH reaches a peak in middle of cycle, ovulation occurs
• FSH and LH are inhibited by high levels of oestrogen and progesterone ready for pregnancy