November Mock - Paper 2 Flashcards
homeostasis
an organism’s ability to regulate internal conditions even when external conditions change
why is homeostasis important
allows for crucial reactions (involving enzymes) to happen at optimum rates
cerebral cortex
conscious activity: problem solving, memory, speech
medulla
unconscious activity: heart and breathing rate, signals to the adrenal glands for adrenaline release
cerebellum
movement, balance, coordination
accommodation
ability to change shape of the lens in order to focus light on the retina from different distances
how to focus on far away objects
- ciliary muscles relax
- suspensory ligaments tighten
- lens becomes thinner
- less light is refracted
how to focus on nearby objects
- ciliary muscles tighten
- suspensory ligaments relax
- lens become thicker
- light is refracted more
effect of light intensity on pupils
- change size
- more light - pupils contract
- less light - pupils dilate
cornea
where light enters the eye
retina
where light is focussed
retinal cells
- rods and cones
rods
detect motion and light intensity
cones
detect red, green and blue wavelengths of light
what do the rods and cones do
send signals to the brain via the optic nerve
myopia
- short sightedness
- elongated eyeballs
- corrected with concave lens
- pushes the focal point back
hyperopia
- long sightedness
- corrected with convex lens
- brings the focal point forward
thermoregulation
brain detects blood temperature and sends out nervous and hormonal signals to effectors to maintain constant temperature
responses for high temperatures
- sweating
- vasodilation
responses for low temperatures
- shivering
- hairs standing up
- vasoconstriction
vasodilation
blood vessels dilate
vasoconstriction
blood vessels contract
sweating
sweat glands in skin produce water which evapourate taking away heat
hairs standing on end
trap air and act as a layer of insulation
what is the endocrine system
system of glands that secrete hormones to send signals to effectors, transported via the blood - slower than the nervous system
pituitary gland
master gland: sends signals to other glands - in centre of brain
pancreas’ role in the endocrine system
produces insulin to controls blood glucose level
role of the thyroid
controls growth and metabolism
adrenal gland
releases adrenaline
ovaries
release eggs and oestrogen
testes
produce sperm
what happens when the blood glucose levels are too high
- pancreas secretes insulin
- causes glucose to move from the bloodstream to respiration cells
- excess glucose converted into glycogen energy stores
what happens when the blood glucose levels are too low
- pancreas secretes glucagon
- causes liver and muscles to convert glycogen back into glucose
type 1 diabetes
when the pancreas cannot produce insulin
type 2 diabetes
when cells can no longer absorb glucose properly
routes of water loss
- exhalation
- urination
- sweating
how is water lost through urination
- water is removed from the blood by the kidneys to the bladder
- water is mixed with urea from excess amino acids from the breakdown of protein to amino acids
overhydration
can cause cells to burst
dehydration
can cause cells to become flaccid
function of the kidneys
antidiuretic hormone from pituitary gland causes tubules in kidneys to reabsorb more water into the bloodstream
what happens when water levels are too high
less ADH is produced so more water is sent to the bladder to leave the body as urine
how to overcome kidney failure
dialysis - blood filtered with a dialysis machine to stop the build up of poisonous ammonia/urea
disadvantages of dialysis
- most of life spent in hospital
- very expensive machinery is required
what causes eggs to mature
- FSH from the pituitary gland
- oestrogen and Lh from the ovaries
what does oestrogen do
inhibits FSH
what does LH do
causes the egg to be released and allows it to be fertilised by sperm
methods of contraception
- birth control pills
- progesterone injection/implant
- condoms/diaphragm
- IUD
- abstinence
- clamping of oviduct/vasectomy
fertility treatments
- FSH/LH injections
- IVF treatment
what does adrenaline do
increases blood flow and breathing rate
what does thyroxine do
controls metabolic rate
what happens when thyroxine levels are too low
- hypothalamus releases TRH
- pituitary gland releases TSH
- thyroid releases more thyroxine
plant hormones
- gibberellins
- ethene
- auxins
gibberellins
- induces germination
- promotes flowering
- increases fruit size
ethene
causes ripening
(released by bananas)
auxins
destroyed by sunlight
auxins in stems
phototropism
auxins in roots
geotropism
phototropism
- shaded side of plant contains more auxin and grows longer
- causes the stem to grow towards the light
geotropism
auxins gather at the bottom of roots where it inhibits growth and causes roots to grow downwards
practical uses of auxins
- weed killers
- rooting powders
- promoting growth in tissue cultures
