homeostasis Flashcards
what is homeostasis
regulation of internal conditions of a cell/organism to maintain optimum conditions in responses to internal and external changes
three examples of internal conditions in humans
keep:
blood glucose concentration
body temperature
water levels
constant
features of automatic control system
receptor cells
coordination centre
effector
what do receptor cells do
detect stimulus/changes in environment (internal and external)
passes information to coordination centre
what does coordination centre do
receives and processes info from receptor cells
sends instructions to effector
what does effector do
muscle or gland that restores optimum level by carrying out response
two parts of nervous system
cns - brain and spinal chord
other nerves running to and fro cns
describe how nervous system works
receptors detect stimulus
sends electrical impulses down neurones to cns (coordination centre)
cns sends electrical impulses down neurones to effector
effectors are usually..
contracting muscles or hormone-secreting glands
how does reflex arc work
• receptor detects stimulus
• sends electrical impulses along sensory neurone to cns
• end of sensory neurone: synapse which releases chemical that passes impulse to relay neurone
• end of relay neurone: synapse releases chemical that passes impulse to motor neurone
• end of motor neurone: effector
• effector carries response
how to investigate reaction time
• p1 sits upright on stool and rests arm on table, dominant hand overhanging
• p2 holds ruler vertically, with 0cm at thumb level
• p2 drops at random time, p1 catches quick as possible
• record measurement at top of thumb
• repeat 5x and calculate mean. convert to reaction times using online conversion table
independent variable of investigating reaction time
drink caffeine and repeat experiment
dominant hand & non dominant hand
what does the brain do
controls our complex behaviours
what is the outer brain called and what does it do
cerebral cortex
responsible for language, memory, consciousness, and intelligence
what is the bit at the back of the brain called and what does it do
cerebellum
controls muscle coordination e.g movements and balance
what is the bit in the middle of the brain and what does it do
medulla
controls unconscious activity e.g breathing and heart rate
why are brain problems difficult to study
skull makes access difficult
extremely complex structures
delicate and easy to damage
three methods to study brain
- study patients with brain damage. by knowing where damage is, they can try to link that area to its function
- electrically stimulate it. do this to different parts of brain and look at effects on behaviour
- mri scans. allows us to look at which parts of brain are most active during activities
what stimulates receptors in eye
changes in light intensity and colour
what does cornea do
transparent front of eye. it refracts light rays into eye
what does lens do
focuses light rays to the back of the eye
ciliary muscles and suspensory ligaments can change shape to lens to focus on near/distant objects
what does the retina do
back of the eye - contains receptor cells for light intensity & colour, then send electrical impulses
what does the optic nerve do
carries impulses from retina receptors to brain
what does the sclera do
white part - tough, protective layer
what does the pupil do
space in centre of iris - allows light rays to pass into eye
what does the iris do
coloured part - controls size of pupil
explain what happens in eye when you enter a dark room
REFLEX ACTION
- light intensity is lower
• receptors in retina detect this
• electrical impulses sent to brain
• brain sends electrical impulses to muscles in iris
• muscles contract, causing pupil to become larger
• more light can enter eye
order of where light goes in eye
CIPLRO
cornea
iris
pupil
lens
retina
optic nerve
how to remember eye order
ciplro
can
i
please
live
really
old
what is accommodation
changing the shape of the lens to focus on near or distant objects
structure of lens
suspensory ligaments connects lens to surrounding ciliary muscle
what happens to lens when looking at near object
• ciliary muscles contracts, causing suspensory ligaments to loosen
• lens is now thicker and more curved
• meaning it refracts light more strongly
what happens to lens when looking at something far
• ciliary muscles relax, causing suspensory ligaments to pull tight
• lens becomes thin and less curved
• refracts light by smaller amount
what is hyperopia and why does it happen
long sightedness
eyeball is too short or lens is too thin, so when focusing on near objects,light is focused at a point behind the retina
how to treat long sight and graph
glasses with convex lenses - partially focus light before it enters eye
what is myopia and why does it happen
short sightedness
eyeball is too long or lens is too thick, so when focusing on distant objects, light focuses in front of retina
how to treat short sightedness and graph
glasses with concave lenses - partially unfocusses light before it enters eye
three treatments for vision defects with one pro and one con
contact lenses - convenient for sport, risk of infection
laser eye surgery to change shape of cornea - precise, risk of infection
replacement lens surgery - risk of damage to retina
what is normal body temperature
37 °
impulses from which receptors go the part of the brain that controls temperature, and what is the part of the brain called?
receptors in the thermoregulatory centre (TC) detect blood temp.
receptors in skin detect skin temp and send impulses to TC
what happens when body temp gets too high e.g during excersize
• receptors detect that its too high
• TC acts as coordination centre. it receives info from receptors and triggers effectors
• effectors e.g sweat glands respond
three things when body is too hot
• hairs are flat
• sweat glands -> sweat -> evaporates, energy taken from body -> body cools
• vasolidation
what is vasolidation
blood vessels that supply capillaries at surface dilate so more blood flows. heat transfers out of blood, body temp decreased
three things when body temp is too low
• hairs stand up - insulating air layer
• muscles contract, shivering. requires respiration, which transfers energy therefore warming body
• vasoconstriction
what is vasoconstriction
blood vessels supplying capillaries at surface constrict. less blood flows, less heat lost
what id the endocrine system
a system of glands, which secrete hormones directly into bloodstream, where it is carried all around body to their specific target organs to produce an effect
compare the endocrine system and nervous system
- NS has extremely fast action, ES has a much slower action
- NS effects are short lived, ES effectd act for long time
- NS uses electrical impulses which travel down neurones, whereas ES uses hormones (chemicals) travel through bloodstream
how can you identify if a response is nervous or hormonal
response is quick: nervous
response lasts long tome: hormonal
where is the pancreas and what role does it have in ES
found: upper abdomen
produces: insulin
use: regulate blood glucose level
where are the ovaries found and what is their use in the ES
found: pelvis
produces: oestrogen
use: menstrual cycle
where are the testes found and what is their use in the ES
found: behind penis
produce: testosterone
use: controls puberty and sperm production
where is the thyroid gland found and what is its tole in the ES (need)
found: front of neck
produces: thyroxine
use: regulating basal metabolic rate, heart rate, and temperature
where are the adrenal glands found and what role do they have in the ES
found: on top of kidneys
produce: adrenaline
use: when in fear or stress, “fight or flight” response
where is pituitary gland/master gland found and what role does it have in the ES
found: brain
produces: many hormones, depending on body conditions
use: range of effects. it acts on other glands, causing them to release other hormones to bring about an effect
what happens to glucose levels when you eat carbohydrates, and what does the body do?
- conc of blood glucose rises
- pancreas senses rise and produces insulin
- insulin travels across body via blood
- insulin triggers body cells to take up glucose from blood, and liver and muscle cells to store excess as glycogen
- blood glucose returns to normal
what happens to conc or blood glucose between meals and what does the body do?
blood glucose falls
- pacreas senses fall
- pancreas releases glucagon, travels across body via blood
- glucagon triggers liver cells to covert glycogen back to glucose, which is released into blood
- blood glucose returns to normal
simple cycle of blood glucose levels throught day
after meal - glucose rises - insulin released - glucose taken in and converted
between meals - glucose falls - glucagon released - glycogen converted
what is type one diabetes
pancreas does not produce enough sufficient insulin, meaning blood glucose can become dangerously high
treatment for type one diabetes
monitor blood glucose conc and use insulin injections throughout the day, most likely after meals
also: limiting food rich in simple carbs, and regular exercise
what is type two diabetes
when body cells stop responding to the bodys insulin, meaning blood glucose can become dangerously high
type two diabetes treatment
diet, including controlling carbs
excercise
pattern of water in body
constant balance
three ways the body loses water
via lungs when exhaling. uncontrollable
via skin when sweating, which also contains sodium ion and urea. uncontrollable
via kidneys when urinating
controllable
how do kidneys regulate excess water, ions, and urea?
- blood containing urea enters kidney via artery
- kidney removes urea, plus excess ions and water
- these leave kidney as urine, stored in bladder
- blood containing no urea leaves kidney via vein
how do kidney adjust levels of molecules in blood
- blood passes through capillaries, small molecules (urea, ions, water, glucose) are filtered out of blood. this is called filtration.
- useful molecules (glucose, some ions, some water) reabsorbed back into blood. this is called selective reabsorption
-waste is released as urine
what does concentration of glucose, ions, and urea look like after passing through kidneys
glucose: same (filtered, reabsorbed)
ions: decreases (filtered, reabsorbed)
urea: virtually zero (filtered)
how do we digest amino acids
- when we digest protein, amino acids pass into blood.
- liver breaks down excess amino acids and produces the chemical
ammonia. this is called deamination - ammonia is very toxic, so liver immediately converts it to urea
- kidneys safely excrete urea
what does the body do when it loses too much water
water falls = blood too concentrated.
- pituitary gland releases ADH into bloodstream
- ADH travels to kidneys, causing tubules to become more permeable to water - more water reabsorbed to blood
- meaning less urine produced, water levels return to normal, pituitary gland stops releasing ADH
what does the body do when blood is too dilute
water concentration rises
- pituitary gland stops releasing ADH
- kidneys reabsob less water into blood
- more urine produced, water levels return
what is kidney dialysis
when kidneys fail and water, ion, and urea levels are adjusted using a machine
how does kidney dialysis work
blood has higher conc of water, ions and urea
- patients blood passes over a semi permeable membrane
- urea, ions, and water allowed through, but not larger molecules e.g protein, blood cells
- on other side of membrane there is dialysis fluid, containing normal concs of water and ions, NOT urea
- there is now a conc gradient for urea
- urea diffuses blood -> fluid
- fluid constantly refreshed - constant large gradient
- excess water and ions also diffuse
compare advantages and disadvantages of kidney dialysis and transplant
- SHORTAGE. no shortage of dialysis machines, shortage of donors
- LIFE. dialysis - several weekly treatments and controlled diet, donors lead normal life, however take anti rejection drugs forever
- ## PRICE. dialysis is long term expensive, donors are initially expensive
what is ovulation
the release of an egg from the ovary every 28 days
what happens during menstrual cycle
- ovulation occurs
- uterus lining thickens in prepation
- sperm present, egg fertilised and implants in uterine wall to develop
- not present, egg and uterine lining break down and release, a period
what are the four menstruation hormones
fsh (follicle stimulating)
oestrogen
lh (luteinising)
progesterone
first stage of hormones
- pituitary gland releases FSH
- travels to ovaries, causes egg to mature
- stimulates oestrogen
second stage of menstruation hormones
- ovaries produce oestrogen
- causes uterus lining to thicken
- stimulates LH, inhibits FSH
third stage if menstrual hormone
- produced by ptuitry gl
- stimulates release of egg
fourth stage of menstrual hormones
progesterone
- - produced by ovaries after ovulation
- inhibits fsh and lh -prevent more eggs
- keeps lining thick in case egg fertilises
- otherwise, progesterone falls, lining breaks down, period occurs
how to remember order of hormones in menstrual cycle
F Ound
O Pen
L Obster
P incer
how does the pill work
contains hormones (oestrogen and progesterone) which prevents production of fsh, preventing eggs from maturing
produces mucus to block sperm
advantage disadvantage of oral contraceptives
99% effecicacy
lighter & less painful periods
no sti protection
requires memory to take it daily
advantages and efficacies of patch, injection, and implant
lighter and less painful periods
convenient (not daily)
injection 97%
patch 91%
implant 99%
which contraceptive methods are hormonal and what disadvantages do they have
pill, injection, implant, patch, iud
no protection from stis
advantage and disadvantage of barrier methods (condom or diaphragm) and efficacy
85%
sti protection
hormone free
spermicide gel
can slip off (m) requires skill (f)
what is an iud, its efficacy, and its advantages and disadvantages
prevents implantation, release hormon
99%
lasts 10 years
no sti protection
painful
what is sterilisation and disadvantages
surgical contraception
women: prevents egg reaching uterus
men: prevents sperm leaving
very difficult to reverse
no sti protection
what is abstaining and what are advantages and disadvantages
avoiding intercourse after ovulation
not “unethical” (no barrier methods)
hard to tell
no sti protection
what is the most effective way of contraception
abstinence (no sex)
what can be used if a woman las low levels of fsh and lh
fertility drug containing said hormones
how does ivf work
- fsh and lh given to stimulate eggs
- eggs collected from mother
- fertilised by sperm from father in lab
- fertilised eggs develop to embryos
- once tiny balls of cells, embryos inserted into uterus
- embryos develop
five disadvantages of ivf
- low success rate
- emotionally and physically stressful
- multiple births - risks
- many embryos destroyed - unethical
- expensive
what does the adrenal gland do
produces the hormone adrenaline to blood when in fear or stress.
heart rate increases -> more oxygen and glucose delivered to brain and muscles, preparing body to “fight or flight”
what does thyroxine do
released by tsh from pituitary gland.
stimulates (speeds) bmr
growth and development
what is negative feedback cycle
if level of a hormone falls, events triggered to cause it to increase. if level is too high, events triggered to decrease it
negative feedback cycle for thyroxine
level falls: pituitary gland releases tsh -> thyroxine released
level now risen: brain detects -> prevents ptuitry gland releasing tsh, thyroxine returns
what is phototropism
when plants grow towards light
what is auxin
plant hormone in the tips of shoots and in the roots that responds to light (phototropism) and gravity (gravitropism)
how is auxin used to grow towards light
auxin triggers cell growth
light causes auxin to concentrate and spread down the darker side of the shoot
this means cells on darker side grow faster, shoot grows towards light
what is gravitropism (or geotropism)
plants growth in response to gravity
how is auxin used to grow towards force of gravity
gravity causes auxin to concentrate on lower side.
in roots, auxin inhibits cell growth.
lower side grows slower, meaning roots grow toward force of gravity
what are two chemicals used by plants to regulate behaviour and what do they do
giberellin: germination of seeds
ethene: cell division and ripening of fruit
how do you investigate plant response to light
- put 10 cress seeds in three different petri dishes with moist cotton
- label a b and c
- shine light: above, each direction
- leave for one week in warm area and water daily
- observe and draw graph
why do seeds in the dark grow faster
seeds usually grow underground and grow rapidly to reach light
how can you investigate plant response to gravity
place a dish of seedlings vertically in the dark
three uses for auxins in agriculture
- weedkillers
2 rooting powders - growing cells in tissue culture, which is used to clone plants
uses of gibberellin in agriculture
- ending seed dormancy
- encourage plants to flower
- make fruit grow larger
used of ethene in agriculture
trigger foods to ripen before being sold e.g bananas
