Homeostasis Flashcards
what is homeostasis
the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes
what does homeostasis help maintain
optimal conditions for enzyme action and all cell functions
what does homeostasis control in the human body
blood glucose concentration
body temperature
water levels
what can the automatic control systems be
nervous or chemical responses
what do all control systems have
receptors
coordination centres
effectors
what are receptors
cells that detect stimuli (changes in the environment)
what do coordination centres do
process the information received from the receptors e.g brain, spinal cord and pancreas
what do effectors do
bring about responses to bring the conditions in the body back to optimum levels , eg muscles or glands
what does the nervous system allow us to do
react to our surroundings and coordinate actions in response to stimuli
how does the nervous system work (4 steps)
- receptor cells convert a stimulus into an electrical impulse
- this electrical impulse travels along cells called sensory neurons to the central nervous system (CNS)
- here the information is processed and the appropriate response is coordinated resulting in a electrical impulse being sent along motor neurones to effectors
- the effectors carry out the response (muscles contracting or glands secreting hormones)
what are reflexes
automatic responses which take place before you have time to think
why are reflexes important
prevent the individual from getting hurt
where does the information travel for a reflex
down a pathway called a reflex arc
how does the reflex arc help reflexes
allows vital responses to take place quickly
why is the reflex arc an unusual response to stimuli
the impulse does not pass through the conscious areas of your brain
how does a reflex happen (5 steps)
- a stimulus is detected by receptors
- impulses are sent along a sensory neuron
- in the cns the impulse passes to a relay neuron
- impulses are sent along a motor neuron
- the impulse reaches an effector resulting in the appropriate response
examples of reflex arcs
pupils getting smaller to avoid damage from bright lights
moving your hand from a hot surface to prevent damage
what are synapses
the gaps between two neurons
how does a response work with synapses (3 )
1.when the impulse reaches the end of the first neuron a chemical is released into the synapse
2. the chemical diffuses across the synapse
3. when the chemical reaches the second neuron, it triggers the impulse to begin again in the next neuron
what is reaction time
how long it takes you to respond to a stimulus.
how can reaction time be measured
ruler drop test
what is the brain made up of
many connected neurons
what does the brain control
complex behaviour
what is the brain a part of
the central nervous system along with the spinal cord
what are the the components of the brain
cerebral cortex
cerebellum
medulla
what does the cerebral cortex do
controls consciousness, intelligence, memory and language
it is the outer part of the brain
what is the cerebellum
controls fine movements of the muscles; rounded structure towards the bottom/back of brain
what is the medulla
controls unconscious actions such as breathing and heart rate ;’ found in the brain stem in front of the cerebellum
why is investigating brain function and treating brain damage and disease difficult
it is complex and delicate
it is easily damaged
drugs given to treat diseases can’t always reach the brain because of its surrounding membranes
it is not fully understood which part of the brain does what
how can neuroscientist twists map out regions of the brain (3 methods)
studying patients with brain damage
electrically stimulating different parts of the brain
using mri scanning
how does studying patients with brain damage help map out regions of the brain
observing the changes in an individua following damage on a certain area of the brain can provide information on the role this area has
how does electrically stimulating different parts of the brain be done and help map out regions of the brain
pushing an electrode into the brain
the stimulation may result in a mental or physical change in the individual providing information on the role this area of the brain has
how does using mri scanning techniques help map out the regions of the brain
a magnetic resonance imaging scanner can be used to create an image of the brain
this can be used to show which part of the brain is affected by a tumour, or which part is active during a specific task
what is the eye
a sense organ containing receptors sensitive to light intensity and colour
how are eye structures adapted
allow the eye to change its shape to focus on near or distant objects (accommodation) and to dim light
what is the retina
layer of light sensitive cells found at the back of the eye
what happens in the retina
when light hits it, the cells are stimulated ,
impulses are sent to the brain which interprets the information to create an image
what is the optic nerve
a nerve that leaves the eye and leads to the brain
what does the optic nerve do
carries the impulses from the retina to the brain to create an image
what is the sclera
white outer layer which supports the structures inside the eye
what is important about the sclera
it is strong to prevent some damage to the eye
what is the cornea
the see through layer at the front of the eye
what does the cornea do
it allows light through and the curved surface bends and focuses light onto the retina
what is the iris
muscles that surround the pupil
how do irises alter the size of the pupil
contract or relax
what happens to the iris in bright light
the circular muscles contract and radial muscles relax to make the pupil smaller - avoiding damage to the retina
what happens to the iris in dim light
the circular muscles relax and the radial muscles contract to make the pupil larger - so more light can enter to create a better image
what do ciliary muscles and suspensory ligaments do
hold the lens in place and control its shape
how do the eyes focus on a near object
the ciliary muscles contract
the suspensory ligaments loosen
the lens is then thicker and more curved - this refracts the light more
how do the eyes focus on a distant object
the ciliary muscles relax
the suspensory ligaments tighten
the lens then becomes thinner - light is refracted less
when do eye defects occur
when light cannot focus on the retina
what is myopia
short sightedness
why does myopia occur
the lens is too curved so distant objects appear blurry
what is hyperopia
long sightedness
when does hyperopia occur
when the lens is too flat so it cannot refract light enough
how are myopia/hyperopia treated (4)
spectacle lenses
contact lenses
laser eye surgery
replacement lens
how are spectacle lenses used to treat eye defects
concave lenses to spread out the light to treat myopia
convex lenses bring the rays together to treat hyperopia
how do contact lenses treat eye defects
work in same way as glasses
allow activities such as sport or the carried out
hard or soft contact lenses last for different lengths of time
how does laser eye surgery treat eye defects
lasers used to either reduce thickness of the cornea so it refracts light less or change its curvature to refract light more strongly
how does a replacement lens treat eye defects
hyperopia treated by replacing lens with an artificial one made of clear plastic
what are the risks of replacement lens
damage to retina
cataracts developing
what does the thermoregulatory centre do
monitors and controls body temperature
where is the thermoregulatory centre found
the brain
what does the thermoregulatory centre contain
receptors that monitor the temperature of the blood
receptors in the skin that send impulses to the thermoregulatory centre
what happens if human body temp is too high
sweat
vasodilation
how does sweat cool you down
evaporates from skin surface resulting in increased energy transfer away from the body
how does vasodilation cool you down
more blood flows closer to the surface of the skin resulting in increased energy transfer from the body
what happens if body temperature decrease too much
sweating stops
skeletal muscles contract rapidly (shivering)
hairs stand on end
vasoconstriction
how does shivering warm you up
generates heat from respiration
how does hairs standing on end warm you up
creates an insulating layer which traps warm air
how does vasoconstriction warm you up
blood does not flow so close to the surface resulting in less heat lost
what does the endocrine system do
sends hormones around the body and produces a response when they reach a target tissue
what is the endocrine system made up of
glands which secrete hormones directly into the bloodstream
what is the pituitary gland
master gland
what does the pituitary gland do
secretes hormones into the blood to either have an effect on the body or act on other glands to stimulate them to produce different hormones
what does the pancreas do
secretes insulin
controls blood glucose levels
what does the thyroid do
secretes thyroxine
controls metabolic rate, heart rate and temperature
what does the adrenal gland do
secretes adrenaline
involved in the fight or flight response
what does the ovary do
secretes oestrogen
what is oestrogen involved in
the menstrual cycle and the development of female secondary characteristics
what do the testes do
secrete testosterone
what does testosterone do
is involved in the production of sperm and the development of male secondary sexual characteristics
how are hormones transported
in the blood to a target organ or tissue where it has an effect
what is the speed of the hormonal system compared to nervous system
much slower but acts for longer
why does glucose concentration in blood need to be kept in a limit
glucose is needed by cells for respiration
what controls the concentration of glucose in blood
pancreas
what can increase glucose levels in the blood
eating foods that contain carbohydrates
what happens when glucose levels are too high
pancreas produces the hormone insulin
how does insulin act in the body
binds to cell in target organs (muscle and liver)
what does insulin cause to happen
glucose moves from the blood into the muscle cells for respiration
excess glucose converted into glycogen which is stored in the liver
blood glucose concentration is reduced
what results in less glucose in the blood and why
rigorous activity eg exercise uses glucose for respiration
when is glucagon produced
if glucose levels decrease
which organ produced glucagon
pancreas
how does glucagon work
binds to liver cells causing glycogen to be broken down into glucose
glucose is released into the blood increasing blood glucose concentration
how is blood glucose concentration kept constant
insulin and glucagon
how do insulin and glucagon work together
in a negative feedback loop
how does a negative feedback loop work
when blood glucose levels change a hormone is secreted to oppose the change
the action of this hormone cannot occur continually because when the blood arrives at a certain glucose concentration the other hormone is produced, resulting in the opposite effect
what is diabetes
inability to control blood glucose level
what is type one diabetes
the pancreas cannot produce enough insulin
what happened to blood glucose levels in type 1 diabetes
blood glucose levels can rise to a fatal amount
how is glucose excreted in type1 diabetes
glucose is extracted with urine and lots of urine is produced leaving the individual thirsty
how is type 1 diabetes treated
insulin injections at meal times
limit intake of simple carbohydrates
pancreas and pancreatic cell transplants
engineering pancreatic cells from mice to make insulin
how do insulin injections help improve type 1 diabetes
results in glucose being taken up into the bloodstream
what is type 2 diabetes
the body cells no longer respond to insulin
what happens to blood glucose levels in type 2 diabetes
can rise to a fatal amoutn
what is a risk factor of type 2 diabetes
obesity
what are the treatments of type 2 diabetes
reducing number of simple carbs in diet
losing weight
increasing exercise
what can different drugs do to help type 2 diabetes
make insulin more effective on cells
help pancreas make more insulin
reduce amount of glucose absorbed from the gut
what is osmosis
the process by which water molecules move from a place of high concentration to a place of low concentration
what happens if water concentration in the blood increases
cells in the body take up water
why do body cells take up water when water concentration in the blood increases
concentration of water in bloodstream is higher than conc of water in cells so water moves into the cells by osmosis
what happens when cells take up water
cells expand and may burst
what happens if the concentration of water in the bloodstream decreases
cells in the body lose water
why do cells in the body lose water when water conc in the blood decreases
conc of water in bloodstream is lower than conc of water in cells so water moves out of cells by osmosis
what happens as cells lose water
shrink
what happens if cells lose or gain too much water
do not function properly
why are the kidneys important
they maintain the balance of water and other substances in the body
how is urine made as blood moves through the body
filtering out waste products
selectively re absorbing useful substances such as glucose, ions and water
what are waste products processed at the kidney
water
ions
urea
how is water lost from the body
leaves at the lungs from exhalation
leaves skin in sweat
depending on conc of water in blood can be lost as urine
how are ions taken into the body
via food
what happens if the ion concentration is incorrect
too little or too much water may enter body cells because water potential of the blood is altered
where are ions lost
sweat
what happens to ions in the kidneys
certain amounts are reabsorbed into the blood after it has been filtered to ensure blood conc is maintained
what happens to amino acids in the liver
delaminated to form ammonia
how is urea made
ammonia is toxic so is converted to urea
how is urea lost in the body
lost in sweat
filtered out of blood in the kidneys
what is anti diuretic hormones
a hormone involved in the control of the loss of water as urine
where is adh released to
the pancreas by the pituitary gland.
when is adh released
when a receptor in the brain detects that the blood is too concentrated
where does adh travel
in the bloodstream to the kidney tubules
what does an increased amount of adh reaching tubules do
increases their permeability to water
so more moves out of tubule and back into bloodstream
what is the result of increased ADH
smaller volume of more concentrated (yellow) urine
blood becoming less concentrated
because more water
what is ADH production an example of
negative feedback loop
how is ADH release a negative feedback loop
if the concentration of the blood increases/decreases, more/less ADH is secreted to reverse this change
what is kidney failure
when your kidneys stop working
what does kidney failure result in
waste products build up which can be harmful to the body and eventually result in death
what are the two ways to treat kidney failure
dialysis
kidney transplants
what is dialysis
the function of the kidneys being carried out using an artificial membrane
where does the blood move during dialysis
between partially permeable membranes surrounded by dialysis fluid
what is lost from the blood during dialysis
useful ions and glucose NOT
but urea , excess ions and water diffuse out of membrane
how many times is dialysis done in a week
3 times
how long does dialysis take
3-4 hours
what are the problems of dialysis
possibility of blood clots forming
amount of time it takes
strict diet
unpleasant experience
build up of waste products between sessions leaves patient ill
what do kidney transplants do
provide the individual with a healthy kidney
who are kidney transplants from
people who have died suddenly or people who are still alive
what is a positive of kidney transplants
the person has less regular hospital visits that dialysis
cheaper than overall cost of dialysis
disadvantages of kidney transplant
could be rejected- antigens on donor organ foreign to immune system
immunosuppressant drugs leave person vulnerable to other diseases
transplanted kidneys do not last forever
when are reproductive hormones released
during puberty
what does reproductive hormones being released cause
secondary sexual characteristics to develop in men and women
eggs mature in women
what is the main male reproductive hormone
testosterone
where is testosterone produced
by the testes
what does testosterone do
stimulates sperm production
what is the main female reproductive hormones
oestrogen
where is oestrogen produced
the ovary
what does oestrogen do
produces physical changes
involved in the menstrual cycle
what is the menstrual cycle
the process the body undergoes each month to prepare for a potential pregnancy
what happens in the first 5/6 days of menstrual cycle
lining of the uterus breaks down and the woman has her period
what happens between day 6-14 of menstrual cycle
the layer of lining in uterus builds up again
what happens on the 14th day of the menstrual cycle
ovulation
an egg is released from the ovary and moves to the uterus via the fallopian tube
what happens between ovulation and day 28 of menstrual cycle
if a fertilised egg has not been embedded in the lining by 28 days it breaks down and the cycle continues
which four hormones control the menstrual cycle
follicle stimulating hormone (FSH)
oestrogen
luteinising hormone (LH)
progesterone
what does FSH do in menstrual cycle
causes the maturation of an egg in the ovary in a follicle
where is FSH produced
pituitary gland
what does FSH stimulate in the menstrual cycle
the ovaries to produce oestrogen
what does oestrogen cause
lining of the uterus to grow again
where is oestrogen produced
the ovaries
when is oestrogen secreted
as a result of FSH
what does oestrogen stimulate in menstrual cycle
the production of LH and inhibits the secretion of more FSH
where is LH produced
pituitary gland
why is lh produced
as a result of oestrogen
what does the release of LH result in
ovulation
where is progesterone produced
the ovaries and secreted from egg follicle
what does progesterone do in menstrual cycle
maintains the lining of the uterus and supports a pregnancy is the egg is fertilised
what does progesterone inhibit
the release of FSH and LH
what are examples of hormonal methods of contraception
the contraceptive pill
the contraceptive patch
the contraceptive implant
the contraceptive injection
IUD
what are examples of non hormonal methods of contraception
spermicides
condoms
diaphragms
copper intrauterine device
male and female sterilisation
abstaining from intercourse
what is the rule of the contraceptive pill
must be taken regularly or the bodies own hormones will be released , leading to an egg maturing
what does the mixed pill contain
oestrogen and progesterone
what does the oestrogen levels being high from the mixed pill result in
inhibits FSH so no eggs mature
what does the mixed pill do to uterus lining
lining stops developing
what does the mixed pill do to mucus in the cervix
becomes thick so sperm cannot move through
what are side effects of the mixed pill
changes in mood
mood swings
depression
breast pain
breast enlargement
increased blood pressure
what is the difference between the progesterone only pill and the mixed pill
this has less side effects in comparison to the mixed pill
what does the contraceptive pill contain
oestrogen and progesterone
how is the contraceptive patch applied
small and stuck on skin
how long does the contraceptive patch last
one week
what does the contraceptive implant do
releases a continuous amount of progesterone
what does the implants release of progesterone result in
prevents the ovaries from releasing the egg
thicken the mucus in cervix
stops fertilised eggs embedding in the uterus
how long does the contraceptive implant last
2 to 3 months
what does the IUD do
releases progesterone
what is the effect of the iUD
same as the implant
how ius the IUD used
T shaped, inserted into the uterus
what do non hormonal methods of contraception do
stop sperm fertilising the egg
what do spermicides do
kill or disable sperm
how effective are spermicides
70-80%
what is a chemical method of n hormonal contraception
spermicide
what are n hormonal barrier methods
condoms and diaphragms
how are condoms worn
over the penis or inside the vagina
what do condomsalso do
prevent the individual contracting sexually transmitted diseases
what is a problem with condoms
it can tear and therefore let sperm through
what is a diaphragm
a plastic cup
where is a diaphragm used
positioned over the cervix
what is a diaphragm used with
a spermicide
what does the copper intrauterine device do
kills sperm in the uterus by stopping any fertilised embryos from implanting in the uterus lining
what are the methods of male and female sterilisation
cutting and tying the fallopian tubes or sperm duct
what does abstaining from intercourse ensure
an egg is not fertilised
what are fertility drugs used for
increasing the chance of pregnancy
what are the main hormones used in fertility drugs
FSH and LH to stimulate maturation and release of the egg
what hormones does the mother receive in IVF
FSH and Lh to encourage maturation of eggs
what happens to the eggs in IVF
extracted from the mother and fertilised in the lab using sperm
what happens to the fertilised eggs in IVF
develop into embryos and one or two inserted in the uterus
what are the benefits of IVF
provides a way for an infertile couple to have a child
what are the cons of IVF
physically stressful due to hormones - can feel sick
emotionally stressful as may not work - 26% success rate
can lead to multiple births unexpectedly - risk to mother and babies
can be expensive if needs to be repeated
what is negative feedback
when the body responds to an increase or decrease in a factor by returning it to its original level
what does thyroxine do
regulates metabolic rate
what is thyroxine important in
growth and development
what is thyroxine released by
the thyroid gland
what stimulates the release of thyroxine
the thyroid stimulating hormone
how are levels of thyroxine controlled
negative feedback
what happens when thyroxine levels increase
detected by receptors in the brain
inhibits release of TSH
inhibits release of thyroxine so levels fall
when is adrenaline produced
times of stress to stimulate fight or flight response
where is adrenaline released from
adrenal glands
what is the release of adrenaline stimulated by
fear or stress , detected in the brain
effects of adrenaline
increased heart rate and breathing rate
glycogen converted to glucose
pupils dilate
blood flow to muscles increased
blood flow to digestive system decreased
why does heart rate and breathing rate increase from adrenaline
to deliver more oxygen and glucose to the brain and muscles for respiration
why is glycogen in liver converted to glucose when adrenaline is released
for respiration
why do pupils dilate from adrenaline
to let in more light
what do plants need hormones for
to coordinate and control growth and tropisms
examples of tropisms
phototropism
gravitropism
what is phototropism
the response to light
what is gravitropism
response to gravity
why do hormones move in plants
move to where they are needed to produce the appropriate response
what tropism do most plants show
positive phototropism because they grow towards the light source
what is the process of positive phototropism
plant exposed to light on one side
auxin moves to shaded side of shoot
auxin stimulated cells to grow more here
so shoot bends towards the light
so plant receives more light - photosynthesis occurs faster
what tropism do most shoots show
negative gravitropism as they grow away from gravity
positive gravitropism process if a root is horizontal
auxin moves to lower side
cells of root grow on side with less auxin, so it stimulates cells to grow on the upper side
this makes the root bend and grow downwards
why is positive gravitropism in roots beneficial
more likely to be increased levels on water and nutrients
provides stability for plant
what happens when the auxin distribution is equal on both sides
it grows straight in that direction
what are two other plant hormones called
gibberellins
ethene
what are gibberellins important for
stimulating seed germination
what is ethene involved in
cell division and ripening of fruits
what do humans use plant hormomes for
to alter plant growth
where do humans use plant hormones
agriculture and horticulture
what are the benefits of humans using plant hormomes
increase yield
obtain desirable features
lower costs
what is auxin used as
weed killers
rooting powders
promote growth in tissue culture
what are many weeds
broad leaved
how have weed killers with auxin been synthesised
to only affect broad leaved plants
how does auxin kill weeds
increased auxin causes the cells to grow too rapidly
how does auxin work as a rooting powder
rooting powder applied to a cutting of a plant and it is placed in the ground
roots grow and new plants grow quickly
how does auxin promote growth in tissue culture
cells from plant are placed in a growth medium
auxin added
cells begin to form roots and shoots
where is ethene used and why
food industry as it controls ripening
what is ethene involved in in the food industry
controlling cell division and stimulates enzymes that result in fruit ripening
what are the benefits of using ethene in food
reduces wastage
as more fruit is suitable to be sold and doesn’t ripen too early
when is fruit picked
when it is not ripe
what happens when fruit is transported and why
it is firm so it gets less damaged and bruised
what happens to fruit when it is needed to be sold
it is exposed to ethene and warmer temperatures
what are gibberellins used for
ending seed dormancy
promoting flowering
increasing fruit size
how do gibberellins end seed dormancy
in the brewing industry
the germination rate of barley seeds os increased to make malt
how do gibberellins promote flowering
allows flowering in any conditions and with bigger flowers
what conditions are normally needed for flowering
longer days and low temperatures
what do the seeds in fruit produce
gibberellins to increase size
why is seedless fruit generally smaller
no seeds that produce gibberellins
how can seedless fruit sometimes be big
can be sprayed with gibberellins to increase their size
