B11 Flashcards
Thermoregulatory centre
In brain
Contains receptors sensitive to temperature of blood in brain
Receives information from skin cells about skin temperature
When body too hot
Sweat produced from sweat glands and evaporates from skin, transferring energy to environment
Blood vessels supplying skin dilate so blood flows closer to surface - vasodilation
When body too cold
Hairs stand up to trap insulating layer of air
No sweat
Blood vessels supplying skin constrict to close of skins blood supply - vasoconstriction
Shiver, which needs respiration which transfers some energy to warm body
Pituitary gland
In brain
Produces many hormones
Called master gland as hormones it produces stimulates other glands
Ovaries
Produce oestrogen
Testes
Produce testosterone which controls puberty and sperm production
Thyroid
Produces thyroxine which
Regulates rate of metabolism, heart rate and temperature
Adrenal gland
Produces adrenaline
Pancreas
Produces insulin used to regulate blood sugar levels
When blood glucose level too high
Insulin secreted by pancreas
Glucose moved from blood into liver and muscle cells to be stored as glycogen
Blood glucose level too low
Glucagon secreted by pancreas
Liver turns glycogen into glucose and releases into blood
Type 1 diabetes
Pancreas produces little or no insulin
Need insulin therapy, injections of insulin throughout day
Limiting intake of food with simple carbohydrates
Type 2 diabetes
People become resistant to own insulin
Overweight increase chances of this happening
Regular exercise
Menstrual cycle
Stage 1 - Day 0-4 uterus lining breaks down
Stage 2 - Day 4-14 uterus lining builds up again into a thick layer full of blood vessels
Stage 3 - Day 14 ovulation
Stage 4 Day14-28 wall maintained
FSH
Follicle stimulating hormone
Produced in pituitary gland
Causes egg to mature in one of ovaries in a structure called a follicle
Stimulates ovaries to produce oestrogen
Oestrogen
Produced in ovaries
Causes lining of uterus to grow
Stimulates release of LH
Inhibits release of FSH
LH
Luteinising hormone
Produced by pituitary gland
Stimulates ovulation
Progesterone
Produced in ovaries by remains of follicle after ovulation
Maintains lining of uterus
Inhibits release of FSH and LH
When progesterone levels fall lining breaks down
Hormonal Control for Fertility
If oestrogen is taken every day it inhibits production of FSH and after a while egg development stops
Progesterone reduces fertility - production of thick mucus which prevents sperm getting through
Pill - contains oestrogen and progesterone, over 99% effective, headaches and nausea
Contraceptive patch - oestrogen and progesterone
Contraceptive implant - progesterone stops ovaries releasing eggs
IntaUterineDevice - t-shaped device, kills sperm
Barrier methods
Diaphragm - shallow plastic cup fits over cervix to form barrier
Spermicide - only 70-80%
Sterilisation
Cutting and tying fallopian tubes in female
Sperm duct in male
IVF
In vitro fertilisation
FSH and LH are given to stimulate several eggs to mature so multiple collected
Collecting eggs from ovaries and fertilising in lab
Can involve Intra-Cytoplasm Sperm Injection where sperm is injected directly into egg
Fertilised eggs grown into embryos in a incubator
Once tiny balls of cells 2 transferred to uterus
Cons of IVF
Multiple births are common, higher risk of miscarriage, stillbirth
Success rate low, 26%
Unused embryos may be destroyed
Thyroxine
Thyroid stimulating hormone released from pituitary gland
Stimulates thyroid gland which release thyroxine
Regulates basic metabolic rate and stimulates protein synthesis for growth and development
Auxin
Plant growth hormone
Controls growth near tips of shoots and roots
Shoots grow in response to light (phototropism)
Root response to gravity (gravitropism + geotropism)
Shoots grow towards light
Shoot tip exposed to light
More auxin accumulates on side in shade
Makes cells elongate on shaded side so bends towards light
Shoot grow away from gravity
Roots towards gravity
When shoot growing sideways more auxin on lower side
Lower side grows faster bending upwards
Root growing sideways also has more auxin on lower side
In roots the auxin inhibits growth so cells on top elongate faster, root bends downwards
Auxin commercial uses
Killing weeds - weedkillers have been developed that only affect broad leaves to leave crops untouched
Rooting Powder - add rooting powder to cuttings to grow clones
Growing cells in tissue culture - tissue culture can be used
Gibberellin commercial use
Stimulates seed germination, stem growth, flowering
Controlling dormancy - Makes them germinate at certain times of year
Inducing flowering - grow bigger flowers, flower any time they want
Growing larger fruit
Ethene
Gas produced by ageing parts of plant
Influences growth by controlling cell division
Stimulates enzymes that cause fruit to ripen
Fruit can be picked unripe and made ripe when transported
Adrenaline
Released by adrenal glands just above kidneys
Increases supply of oxygen and glucose to cells in brain and muscles
