Homeostasis Flashcards
what is homeostasis?
Keeping internal and external conditions at optimum
what are control systems that maintain your body temperature?
blood glucose levels and water content
what are the three main components of an automatic control system?
receptors, coordination centres (brain, spinal cord, pancreas) and effectors
How does out automatic control system keep internal environments stable?
negative feedback
What happens if something is too high or low in our body?
-receptors detect a stimulus-
-coordination centre receives and processes
effector produces response to counteract change and restore optimum levels
what are sensory neurones?
carry information as electrical impulses from the receptors to the CNS
what are the motor neurones?
carry electrical impulses from the CNS To the effectors?
what are effectors?
muscles and glands which respond to nervous impulses.
whats the connection between two neurones?
synapse
how is the nerve signal transferred?
chemicals that diffuse across the gap that set off a new electrical signal
what are reflexes?
rapid and automatic responses to stimuli that dont involve conscious part of the brain
what does the neurones in the reflex arcs go
through the spinal cord or through an unconscious part of the brain.
how can you measure caffeine in comparison to someones reaction?
-sit with arm resting on edge of table
-hold ruler vertically
-make sure 0 is level with thumb and finger
-let go without warning
-try to catch ruler as fast as possible
-measure number on ruler
-repeat to calc mean
-then have caffeinated drink
what are the control variables of measuring reaction time practical?
use the same person
use the same hand
dropped from the same height
How can reaction time be measured on a computer?
click a mouse as soon as a stimulus is seen on screen
you remove issue of human error
more accurate measurements
remove person being able to predict when to respond
what is the brain made up of?
billions of interconnected neurones
where is the cerebral cortex and what is its function?
its at the front
responsible for consciousness, intelligence, memory and language
where is the medulla located and whats its function?
its at the bottom
controls unconscious activities like breathing and heartbeat
where is the cerebellum and what does its function?
its at the back responsible for muscle coordination
what can docters use the to find whats happened if the small part of the brain is damaged?
they can monitor your actions
How can scientists study the brain with electrical stimulation?
push tiny electrodes into the tissue giving small zaps of electricity.
Stimulate different parts and see what it does
How scientists study the brain with MRI scans?
produces a detailed picture of brain structure so scientists can see areas of the brain that are active when people are doing certain things
What is the sclera?
tough, supporting wall of the eye
whats the cornea?
transparent outer layer found at front of eye, refracts light
whats the iris?
contains mucus to control diameter of pupil, hole is middle, how much light enters the eye.
what does the lens do?
focuses light onto the retina
What controls the shape of the lens?
ciliary muscles and suspensory ligaments
what happens when light receptors detect a very bright light?
Reflex makes the pupil smaller, circular muscles in iris contract and the radial muscles relax, reducing amount of light entering the eye.
What happens when light receptors detect a dim light?
Radial muscles contract and the circular muscles relax making the pupil wider
what is accomidation?
eye focuses light on the retina by changing shape of the lens
What does the eye do to focus on near objects?
1.) ciliary muscles contract, slackens suspensory ligament
2.) lens becomes fat
3.) increases amount of light refracted
What does the eye do to look at distant objects?
1.) ciliary muscles relax, suspensory ligaments pull tight
2.) lens goes thin
3.) refracts light by a smaller amount
what can people with long-sightedness not do? (hyperopia)
focus on near objects
Why cant people with long-sightedness view near objects?
the lens is the wrong shape and doesnt refract the light enough
or eye ball is too short
imagine near objects are brought into focus behind the retina
How can you correct long-sighted people?
wear glasses with a convex lens
what are short-sighted people unable to do?
unable to focus on distant objects
why does short-sightedness occur?
lens is the wrong shape and refracts light too much, eye ball is too long
imagine of distant object is brought into focus in front of retina
what can fix short-sightedness? (myopia)
using glasses with a concave lens
What are 3 treatments for vision defects?
contact lenses: thin lenses that sit on surface of eye to compensate for fault of focusing
laser eye surgery: change shape of cornea
replacement lens surgery: replace lens of eye
what happens when your body is too hot?
sweat is produced by sweat glands and evaporates from skin
blood vessels dilate so more blood flows close to the surface of skin (vasodilation)
both transfer energy to the environment
what happens when your body is too cold?
hairs stand up to trap insulating layer of air
no sweat produced
blood vessels constrict to close off skins blood supply (vasoconstriction)
shiver so respiration transfers energy to warm the body
whats the difference between hormones and nerves?
hormones are slower action, lasting longer, acts more in a general way
nerves are very fast, act for a short time, act on precise areas.
what does the pituitary gland (master gland) do?
produces many hormones to regulate body conditions
what do the ovaries produce?
produce oestrogen, involved in menstrual cycle
what do the testes produce?
testosterone, which controls puberty and sperm production
what does the thyroid produce?
thyroxine, regulates rate of metabolism, heart rate and temperature
what does the adrenal gland produce?
adrenaline, prepares body for fight or flight.
what does the pancreas do?
produces insulin, regulates blood glucose levels
where can excess glucose be stored?
in the liver as glycogen and in the muscles
what happens when blood glucose levels are too high?
insulin is secreted by pancreas
glucose moves from blood into liver and muscle cells
insulin makes liver turn glucose into glycogen
what happens when the blood glucose level is too low?
glucagon secreted by pancreas
glucose released into bloody by liver
glucagon makes liver turn glycogen into glucose
what is type 1 diabetes and how can it be controlled?
pancreas produces little to no insulin
insulin injections can help
limit carb intake and regularly exercise
what is type 2 diabetes and how can it be controlled?
person becomes resistant to their own insulin
obesity increases risk
eat carb controlled diet and regularly exercise
how do the kidneys produce urine?
taking waste products out of the blood and passes through kidneys (filtration)
whats selective reabsorption?
useful substances like glucose, ions and right amount of water are reabsorbed into the blood after filtration.
what is urea?
proteins (amino acids)
cant be stored in body so excess are converted into fats and carbs,
ammonia is produced as a waste of this
ammonia is toxic so converted into urea in liver
why are the ions removed during urination?
if not removed too much or too little water could be brought into cells by osmosis
sweat loses ions
why is water removed by urination?
body needs a constant in and out flow of water
lose water from skin in sweat, lungs (breathing)
what controls the concentration of urine?
anti-diuretic hormone (ADH)
pituitary gland releases into bloodstream
how can people with kidney failure be kept alive?
dialysis, kidney transplant
what are the disadvantages to dialysis?
long term expensive
has to be done regularly
takes a long time
can cause bloody clots or infection
how does dialysis work?
persons blood flows between a partially permeable membrane surrounded by dialysis fluid
what is the dialysis liquid made up of?
same concentration of dissolved ions and glucose as healthy bloody so useful dissolved ions and glucose wont be lost, only waste products like urea
what are the risks/disadvantages of kidney transplants?
can be rejected
poses small danger if patient donating is alive
long waiting list
what happens in stage 1 of the menstruation cycle?
uterus lining breaks down for 4 days
what happens in stage 2 of the menstruation cycle?
uterus lining builds up, day 4 -14 layer full of blood vessels read to recieve fertalised egg
what happens in stage 3 of the menstruation cycle?
egg develops and is released from ovary at day 14 (ovulation)
what happens in stage 4 of the menstruation cycle?
wall is maintained for about 14 days, if no fertalised egg lands on uterus wall by day 28 the lining breaks down.
what does oestrogen do?
produced in ovaries, causes lining of uterus to grow
stimulates LH release, inhibits FSH release
what does progesterone do?
produced in ovaries, maintains uterus lining, when progesterone level falls lining breaks down, inhibits release of LH and FSH
what does FSH do?
produced in pituitary glands, causes egg to mature, stimulates ovaries to produce oestrogen
what does LH do?
produced in pituitary gland, stimulates egg release at day 14 (ovulation)
what can be used to reduce fertility hormonally?
taking oestrogen daily to keep levels constantly high inhibiting FSH production
taking progesterone to create thick mucus
taking the pill
contraceptive patch
contraceptive implant
contraceptive injection
IUD
what are non-hormonal forms of contraception?
condoms
diaphragm
spermicide
what is a perm way of avoiding pregnancy and a natural one?
sterilisation
abstinence
ryhthem method
what causes a woman to be infertile?
doesn’t produce high enough levels of FSH so no eggs are released due to them not maturing
what are the pros and cons of giving a woman FSH and LH hormones to get pregnant?
pros- helps alot of women to start families
cons- doesnt always work, expensive, mentally + physically draining, multiple pregnancies, unethical
how is IVF carried out?
inject sperm into egg in lab, fertalised eggs grown into embryos in lab, 1 or 2 is transferred to womans uterus, FSH and LH given before egg collection to stimulate several eggs to mature
what is auxin and what does it control?
controls growth near the tips of shoots and roots
controls growth in plants in response to light
what does extra auxin do?
promotes growth in shoot but inhibits growth in the root
how do you measure for plant growth responses?
10 seeds in 3 different petri-dishes
shine light onto 1 of the dishes and put 2 in differnt directions
leave seeds alone for a week
what can auxin be used for?
killing weeds
growing from cuttings with rooting powder
growing cells in tissue culture
what do gibberellins stimulate?
seed germination, stem growth and flowering
what do gibberellins stimulate?
controlling dormancy
inducing flowering
growing large fruit
how does ethene stimulate the ripening of fruit?
controls cell division and stimulates enzymes that cause fruit to ripen
