homeostasis and response Flashcards
what is homeostasis
the maintenance of keeping a stable eternal environment
what is an automatic control system
recognises when there is a change from optimal conditions and sends a signal to reverse the change
what different components are there in automatic control systems and what do they do
receptors - detect change such as a rise in temp
coordination centre - brain or spinal cord - interoperate change and decide what needs to be done
effectors - things that carry out the change - muscles (contract) or glands (release hormones)
how do the different components in the automatic control system send signals between them
- the nervous system
- endocrine system
what is the difference between the nervous system and the endocrine system
nervous - very fast and precise, electrical impulses, through nerves, responding quickly
endocrine - hormones through the bloodstream, throughout the entire body, slower and longer lasting
what is negative feedback
when the level of something gets to high, negative feedback will increase it again. a continuous cycle
what is an example of negative feedback - use a scenario
if you walk into a cold room, the low temp will be detected by receptors in our skin, and nervous system will send impulses to control centres like our brain which then sends a signal to effects such as muscle to shiver therefore increasing our body temp
what happens if negative feedback goes too far and contradicts its original job - such as shivering too much that it raises our body temp too much
another set of receptors would send a new signal and the process continues to repeat over and over
what is the function of a neuron
carry electrical impulses from one point to another
what are some characteristics of neurons
long, thing, branched connections which enable messages to be passed on from other nerve cells.
how do nerve cells communicate with each other
- electrical impulses arrive at the end of a nerve
- impulse triggers release of neurotransmitter
- the neurotransmitter is released into the synaptic cleft (the gap between two synapses)
- the neurotransmitter diffuses across the cleft
- it attaches to receptors on the postsynaptic neuron which then triggers the electrical impulse in the second nerve
what is the central nervous system made up of
brain and spinal cord
what does the central nervous system do
receives sensory information and sends orders to the rest o of the body to respond to those orders
what do sensory neurons do and what is an example of what they pick up on
send information from receptors to the central nervous system - changes in temperature or the amount of co2 in blood
what do motor neurons do
once the central nervous system has decided what to do to solve the promblem it sends the informaton through impulses back out to the body’s effectors using motor neurons
what is an effector
the cell, tissue or organ that responds to the signals from the control system
what is a receptor
the detector of the changing environment
what is a reflex arc
the nerve pathway which follows a reflex action
what are the benefits of a reflex arc
they are rapid and automatic and therefore we respond quickly and avoid getting hurt
how do reflex arcs work
- the heat from an object ( the stimuli) would be detected by receptors which will stimulate a sensory neuron carrying an impulse from your finger to your spinal cord
- in the spinal cord it the impulse will transfer the impulse to a relay neuron which passes the impulse to a motor neuron
- this will then travel back to the body to a receptor such as bicep which will contract
what is the endocrine system
consists of a series of glands that secrete hormones into the blood and spread through the body
what are hormones
small chemical molecules
what do some tissues have that allow hormones to attach to them
some have receptors that are specific to the hormones that allow hormone molecules to trigger certain changes in the cell
what are the main three glands in the
system
pituitary gland, thyroid gland, adrenal gland
what is the pituitary gland
produces different hormones some of which tell the body directly what do do while others tell other glands to release hormones
what is the thyroid gland
produces thyroxine which regulates the rate of metabolism, as well as helping growth and development
what happens if the pituitary gland detects low levels of thyroxine and what is this process called
it will produce an amount of tsh ( thyroid stimulating hormone) which stimulates the thyroid to produce more thyroxine - negative feedback
what is the adrenal gland
produce adrenaline which is normal released during a fight or flight response by increasing heart rate or increasing blood pumping rate
what are two other glands which are important
testes and ovaries
what do the gland testes do
found in males
produce the hormone testosterone for puberty
and produce the male gametes - sperm - for reproduction
what do the ovaries do
only in female
produce oestrogen
puberty and menstrual cycle
female gametes - egg cells
what is the difference between the nervous system and the endocrine system
nervous - relies on hormones which are transported in the blood, spread more slowly and effects last longer, spread through entire body
endocrine - relies on electrical impulses which are transferred along nerve cells, very fast and short lasting effect, sent to one specific area
in the brain what is the cerebral cortex responsible for
consciousness, intelligence, memory, language, vision, hearing, senses
in the brain, what is the cerebellum responsible for
balance, muscle coordination
in the brain what is the hypothalamus responsible for
regulating body temp and sending signal to pituitary gland
what connects the brain to the spinal cord and what is responsible for
the brain stem and medulla which control unconscious activity like breathing and heart beating
how can scientists study the brain
- study people with brain damage
- electrically stimulate some parts of the brain
- scanning the brain - CT/PET/MRI
Why is treating the brain difficult
- many different things can go wrong with your brain; tumours, mental health, trauma
- encased in skull and therefore hard to reach
- so complex - struggle to fix things with chemicals
what is thermoregulation
the control of our internal body temperature
why is the average temperature of our bodies 37 degrees
the perfect temp for our enzymes to function
how does our body know our body temperature
receptors and the thermoregulatory centre in the brain
what will the thermoregulatory centre do if we are too hot or too cold
send signals to our body to complete functions to regulate back out body temperature
what mechanisms do our bodies use to warm up the body temperature if it drops too low as well as the opposite
conserve heat
- constrict blood vessels which lie near the surface of our skin so less heat energy is lost to the surroundings
- contract elector muscles making hair stand on ends - trap a small layer of insulating air
generate
- shiver - muscles contract automatically - require energy from respiration resulting i heat energy released as waste to warm up
to cool down we do the opposite of above as well as producing sweat which takes away the heat from our bodies
where in the eye is the cornea and what does it do and some features
the first structure, is transparent to let light pass through, no blood vessels so oxygen i diffused through
causes light to refract
where in the eye is the iris and what does it do and some features
the coloured part - control how big or small pupil is
what is the pupil
a small gap in the middle of the iris allowing light to pass through to the lens
where in the eye is the lens and what does it do and some features
behind the pupil refract light, change shape allow to control how strongly to refract light - always focus light on retina
where in the eye is the retina and what does it do and some features
at the back of the eye, made of two receptor cells (different type)
what are the two types of receptor cells that make up the retina and what do they both do
cone cells - allows us to see in colour but cant work well in low light
rod cells - more sensitive to light but only see in black and white
what is the fovea
a structure in the retina made entirely of cone cells - where we try to focus light on
where in the eye is the optic nerves and what does it do and some features
at the bottom back of the eye - takes impulses generated by receptors and takes them to the brain
what is the iris reflex
controls the size of your pupils as bright light can cause damage to the retina.
because of the iris reflex what happens to the pupil in different conditions
in bright light - pupils get smaller to let less light in
low light - get more light in to help see in dark
what is it called when your pupil is smaller and bigger due to the iris reflex
smaller - constricted
larger - dilated
how does the iris reflex work
iris is made up of two muscles
- stretch around pupil (circular muscles)
- around the outside (radial muscles)
to make smaller - the circular muscles contract and the radial muscles are relaxed
to make bigger - circular muscles react and radial muscles contract
what does accommodation mean in terms of the eye
a reflex that changes the refractive power of the lens so you can see both near and distant objects
when an object is close and far what shape must the lens be and why
needs to be short and fat to be more curved and therefore will refract more strongly
doesn’t need to do much as the cornea already refracted light. lens stretches out so it is less curved
why are people longsighted and how can this be helped
lens cant refract enough - unable to focus on near by objects. the light is still not focused by the time it hits the retina
- use glasses with a convex lens which holds extra refraction
why are people short-sighted
refracts too much - light from distant objects that don’t need refracted too much are over refracted and form before the retina
- use glasses that contain concave lenses refracting light outwards
what is blood glucose concentration
the amount of sugar in our bloodstream
what organ detects high sugar levels
pancreas
what will the pancreas do in response to a spike in blood sugars
release the hormone insulin into bloodstream
what does insulin do
travels round the body and binds to certain cells telling them to take in some glucose from body. these cells will then take in glucoses turning it into glycogen (long term storage form of glucose )
how does the body respond to low glucose levels
glucagon ( a hormone) is released from the pancreas and does the opposite of insulin - travel around body to cells which take glycogen and break down into glucose molecules again
what is the main job of kidneys
filter blood and remove all of unwanted waste product and regulating the levels of useful things in the body
what is the most common waste product of the kidneys
urea - made during diamination where excess amino acids and converted to fats and carbs for storage
how do we loose water
sweat, lungs when we breathe and urine
why is water regulation so important
cells will loose or gain water through osmosis
- if too much cells would intake too much and swell and burst
- if too little cells would not intake enough and shrink
what is filtration and selective reabsorption in the kidneys
in the kidneys there are small structures called tubules which absorb any small products such as water, glucose, amino acids and urea
-we reabsorb the things we want to keep such as glucose and some water
how are water levels regulated in the body
a structure in the brain called hypothalamus detects if water levels are too low and send a signal to the pituitary gland which releases a hormone called ADH which travels around the body to the kidneys where it tells the kidneys to absorb more water - we then produce less urine
what process is triggered by reproductive hormones
puberty
what are the main reproductive hormones in men and women and where are they produces
testosterone in men - testis
oestrogen in women - ovaries
what four hormones are linked to the menstrual cycle and where are they produced
oestrogen (o) - ovaries
progesterone (p) - ovaries
luteinising (LH) - pituitary gland
follicle stimulating hormone (FSH)M- pituitary gland
how is oestrogen and progesterone linked to the menstrual cycle
oestrogen - stimulate uterus lining to grow
progesterone - maintain lining of uterus
how is luteinising hormone and follicle stimulating hormone linked to menstrual cycle
LH - stimulates the release of egg on day 14 (ovulation)
FSH - stimulate an egg to mature in ovaries
what is stage one and two, three and four of the menstrual cycle
menstruation - bleeding - the breakdown of the uterus lining - four days
where lining begins to build up again - ten days - prepare uterus lining for fertilised egg
ovulation - one day - egg released from ovaries
maintain lining- all the way to day 28
how do the hormones in the menstrual cycle interact with each other
FSH stimulates ovaries to produce O, which will then inhibits FSH (negative feedback)
when O levels get high it stimulates the release of LH causing a spike resulting in ovulation
P inhibits both LH and FSH
what is contraception
artificial methods used to prevent the fertilisation of an egg and therefore pregnancy
what are the two categories of methods of contraception
hormone and non hormone
what do hormonal methods rely on
the release of oestrogen or progesterone
- if O is released daily it inhibits the production of FSH - no egg can therefore develop
- if P is released it will create a build up of thick mucus in cervix therefore preventing sperm
what is the most common hormonal method of contraception, effectivity and side effects
the combined oral pill - 99% affective
headaches, nausea
what is a other hormone method of contraception not the pill
the patch - slow release of O and P hormones (one week)
injection - P (two-three months)
implant - P (three years)
IUD - inside uterus - release P (three years)
what do non hormonal methods of contraception have in common
all work by preventing sperm meeting the egg
what are some examples of non hormonal methods of contraception
condom/female condom - also protects against std
diaphragm - shallow plastic cup going over the cervix blocking sperm ( not reliable)
spermicides - not reliable
sterilisation - cutting or tying the fallopian tubes - permanent also for men
how can we use hormones to increase a women’s fertility
low levels of FSH and therefore egg unable to mature. give FSH in form of a pill and give LH to stimulate egg release (ovulation)
what is IVF
fertilising outside of the body
what are the five steps for IVF
women given FSH and LH to stimulate egg to mature
collected from overlies and fertilised from sperm from father - done in a lab
placed in incubator to grow into embryo
one or more embryo will be implanted into women’s uterus
what are the pros and cons of IVF
pros - allows infertile couples to have a baby
cons - low success rate, emotionally upsetting, stressful and physically unpleasant. because multiple embryos are inserted many people have more than one baby - lead to more complications
why are some people completely against IVF
they believe that some embryos go to waste and therefore destroyed even though they had the potential for human life
in advancement in tech - we are able to find out characteristics and diseases embryos may have - lead to designer babies
what are auxin hormones and what do they do in the roots and shoots
- control growth and ends of shoots and roots
- when they are produced they dissolve and diffuse backwards to shoot and roots
- in roots they inhibit growth in shoots they stimulate growth
why do auxins accumulate on the shaded side and the lower side of the shoots and what is the difference in the roots
they are positively phototrophic (grow toward light) and therefore the cells on the shaded side grow faster causing the shoot to curve around toward light
negatively geotropic (grow away from ground) and therefore cells on the lower side will grow faster causing the shoot to grow upwards
in roots - they are opposite neg photogenetic etc and therfore if exposed to light they will accumulate to lower shaded side and because in roots they inhibit growth it will grow more on the upper side, curving downwards
what are the three main hormones in plants
auxin (A)
ethene (E)
gibberellin (G)
how are auxin (A) hormones used in plants
- stimulate growth in plants
- use to kill weeds - adding to much
- use to grow plant clones
- help cuttings regrow after being put in soil with rooting powder (contain auxin)
how are ethene (E) hormones used in plants and how do they work
- stimulate the ripening of fruit
- picking fruit before it is ripe to ensure getting shipped in best conditions - once arrives it gets exposed to ethene hormone to stimulate the ripening process to sell
- stimulate an enzyme
how are gibberellin (G) hormones used in plants
- controlling dormancy - induce germination even if external conditions are correct
- inducing flowering - induce on demand and not need certain conditions
- producing larger fruit
