homeostasis and response - B5 Flashcards
what is the definition of homeostasis?
the regulation of the internal conditions of the body in order to maintain an stable, optimum internal environment in response to internal and external changes
in what order does the body respond to changes?
receptor
coordination center
effector
where is the coordination center?
brain and spinal chord
what are the two types of effectors and how do they work?
muscles - contract when stimulated
glands - secrete hormones when stimulated
what is negative feedback?
when your body produces and opposite action to something that has happened in order to get conditions back to normal.
explain each stage of the control system
-receptors = detect change and sends info to coordination center
-coordination center =receives and processes info and coordinates a response
-effector + produces a response
describe the structure of a neuron
long, thin and branches to connect to other neurons
what and how do synapses work?
-they are gap between nerve cells
-when an electrical signal reaches the end of 1 nerve cell it stimulates the release of chemicals
-these chemicals diffuse across the synapse
-when the reach the next neuron is stimulates another electrical signal to be generated
what makes up the nervous system
receptors ,sensory neurons, cns, motor neurons, effectors
what is the cns made up of
brain and spinal chord
what is a reflex arc made up of
receptor, sensory neuron , relay neuron, motor neuron, effector
what are reflexes
rapid automatic actions
what does a motor neuron do
pass a signal from cns to effector
why are reflexes important?
they protect us from harm
why doesn’t the reflex arc involve the brain?
because reflexes are quick subconscious, automatic actions
what does a sensory neuron do
passes a signal form the receptor to the cns
what makes up the brain
cerebral cortex, cerebellum, hypothalamus, medulla + brainstem
where is the cerebral cortex and what does it do?
-the wrinkly layer
-controls consciousness, intelligence, memory, senses ( sight and hearing), language
where is the cerebellum and what does it do?
-the back of the brain
-controls muscle coordination and balance
where is the hypothalamus and what does it do?
-the middle of the brain
-regulates body temperature and sends signals to pituitary gland
where is the medulla and what does it do?
-in the brain stem
-controls unconscious actions like breathing and heart beat
how can we study the brain?
by studying people who have brain damage, electrically stimulating certain areas of the brain and my scans ( CT, MRI PET)
how is studying the brain dangerous
-the brain is very complex so we don’t know all of it
- its easy for the brain to catch diseases from infection which are hard to treat
- the brain is hard to access as its encased by the skull
what are the structures that make up the eye
cornea, iris, pupils, lens retina, fovea, optic nerve
describe cornea
transparent part that allows light through and bends it
describe iris
the coloured part of the eye that changes in response to light intesity
describe pupil
the gap in the iris that allows light to pass through to lens
describe lens
the place where light bends to focus on the retina
describe the retina
the back of the eye that contains cone cells and rod cells
describe the fovea
the part of the retina that has the most cone cells so the lens aims to focus light there as it produces the best image
what is a cone cell
cells that are sensitive to colour
what is a rod cell
cells that are sensitive to light and therefore help us to see better in the dark, but only in black and white
what is the optic nerve
sends signals from receptors in eye to cns
what is the iris effect
how the iris constricts or dilates in order to let in the optimum amount of light
what are the two muscles in the iris
radial muscles and circular muscles
how does the iris change in a lot of light
it constricts
-the circular muscles contract and the radial muscles relax
-the pupil is smaller and less light can pass through
how does the iris change in low light
it dilates
-the circular muscles relax and the radial muscles contract
-the pupil is bigger
why is the iris effect important
because too much light can damage retina
what helps the lens to change shape
suspensory ligaments and ciliary muscle
how does light need to be refracted for near by objects
it needs to be refracted strongly because the light enters at a wide angle
how does the lens change so that we can see near objects
it becomes short and fat
how do the suspensory ligaments and ciliary muscles change to make the lens short and fat
the ciliary muscle contracts and the suspensory ligaments slacken
how does light need to be bent for objects that are farther away
the lens doesn’t need to refract as much because the light comes in at a smaller angle
how does the lens change when the light is farther away
it becomes wide and thin
how do the suspensory ligaments and the ciliary muscle change to make the lens wide and thin
the ciliary muscle relaxes and the suspenspry ligaments becocme taut
what is long sightedness
when a person struggles to see objects that are near
what does the lens to that cause long - sightedness
-the lens does not refract enough
-near objects need a stronger refraction
- so the light focuses behind the retina which means the image appears blurry
how can long- sightedness be treated
-with a convex lens
-this refracts the light more strongly so that it focuses on the fovea
what is the medical name for long sightedness
hyperopia
what is short sightnedness?
when a person stuggles to see objects that are far away
what does the lens do that causes short sightnedness
-it refracts light too much
-objects that are farther away don’t need to be refracted as much
-so the increased refraction of the lens means that the light is focused and an image is formed before the retina so the image is blurry
how can short sightedness be treated
with a concave lens
-they refract light outwards and so counteract the effect of the lens
what is the medical term for short sightedness?
myopia
what is thermoregulation
the controlling of body tempreture
where is the thermoregulatory centre
the hypothalamus in the brain
how do we make our bodies warmer?
1.vasoconstriction - blood vessels in skin capillaries narrow = less blood flows near surface of the skin = less heat lost
2.erector muscles contract = this causes the hairs on the skin to rise which creates a layer of insulating air
3. shivering - automatic muscle contraction/ relaxing = needs energy from respiration = heat energy produced a a waste product
how do we cool ourselves down ?
1.vasodilation - blood vessels dilate = more blood flows near the surface = more heat lost
2.erector muscles relaxing = hairs are flat and no layer of insulating air formed
3. sweating - water and salt that we secrete, when it evaporates it takes heat with it
how does the endocrine system work?
- it has glands that secrete hormones that flow through the bloodstream
- the bind to receptors on specific cells that cause the cells to bring about change
where and what does the pituitary gland do?
connected to brain
secrete lots of hormones, some that stimulate other glands to secrete hormones e.g TSH - stimulate thyroid gland to secrete thyroxine
where and what does the thyroid gland do?
in neck
secret thyroxine
- controls rate of metabolism and helps with growth and development
where and what does the adrenal gland do?
on top of kidneys
secretes adrenaline
- stimulates flight of fight response e.g increased heart rate and increased blood pumping around the body
what does the pancreas so
secretes insulin
-controls blood glucose levels
what do the testes do
secrete testosterone
and produces sperm
what do the ovaries do
secretes oestrogen
produces eggs
which system is faster, endocrine or nervous
nervous system because of the electrical impulses
which system has longer lasting effects
the endocrine system
what does each system target?
nervous - precise areas
endocrine - more general areas
what happens when glucose levels fall too low?
tissue can’t respire properly
what happens when glucose levels get too high?
-the pancreas detects it and secretes insulin
-this binds to cells mainly in the liver and muscles and makes them absorb glucose and store it as glycogen
what happens when blood glucose levels fall too low
-the pancreas detects it and secretes glucagon
- this goes to cells mainly in liver and makes them break down their glycogen into glucose and release it into the blood
what happens to people with diabetes?
they cannot control their blood glucose levels
what is type 1 diabetes
when the pancreas cannot produce any or enough insulin
who usually gets type 1 diabetes
children and teenagers because its genetic
how is type 1 diabetes regulated?
by injecting insulin after every meal, monitoring diets and exercising regularly
what is type 2 diabetes
when the tissue cells becomes resistant to insulin because of poor diets and lock of exercise
who usually gets type 2 diabetes
older people
how is type 2 diabetes treated?
by having a healthy diet and exercising regularly
what is glucose
a carbohydrate
what do the kidneys do?
excrete urea from the body and regulate the levels of water and ions
what is urea and is it formed
a waste product
- it comes from deamination, where the converts excess amino acids into fats and carbohydrates for storage
-this produces ammonia which is toxic
why do ion levels need to be regulated
-too high/ low ion levels can damage our cells
-if the levels are wrong, it can disrupt the balance between water levels and ion level and cells may absorb too little/much water
-we also lose ions from sweating
why do water levels need to be regulated
-so that cells absorb the right amount of water my osmosis
-too much water= cells absorb more water swell and burst
-too little = cells do not absorb enough water and shrink
- we also lose water from breathing out and sweating
how does the kidney regulate levels and excrete urea
- there are tiny structures called nephrons in the kidneys
-they have tubules and capillaries
-the tubules absorb small molecules from the blood in he capillaries like glucose water, ions, amino acids and urea but NOT large proteins and red blood cells = FILTRATION
-the capillaries reabsorb any small molecules they need not all and not any urea and almost all glucose and amino acids = SELECTIVE REABSORPTION
-what is left is waster and produces urine
what happens if water levels in the blood are too low
the hypothalamus sends a signal to the pituitary gland
-this stimulates it too secrete ADH
-this hormone goes around the body to the nephrons and stimulates the capillaries to reabsorb more water
how does blood enter and exit the kidneys
enters via renal arteries
exits via renal veins
what transports urine from kidneys to bladder
ureters
what transport urine from bladder out of body
urethras
what is at the start of a nephron
the glomerulus ( blood capillaries) and the bowman’s capsule(tubule) this is where things are filtered out
what are the consequences of kidney failure
build up of waste in the blood and cannot regulate water and ion levels
how does dialysis work
the blood goes though the machine and meets the dialysis fluid
-they are separated by a partially permeable membranes
-the dialysis fluid contains the same amount concentrations as healthy blood
- so the right amount of water and ions and all urea diffuse into the dialysis fluid
- the blood then goes back into the body
why does dialysis fluid regularly have to be changed
to maintain a concentration gradient
what are the disadvantages of dialysis
time- consuming
expensive
unpleasant and risk of infection
what is the advantage of a kidney transplant
its cheaper
what are the disadvantages of kidney transplants
the body can reject the kidney
the person will have to take immunosupressants for the rest of their life
their is not enough kidneys for all the transplants
what is puberty
the development of secondary sexual characteristics in a person
give examples of secondary sexual characteristics
breast development, deepened voice, pubic hair, increased height
what is stage 1 of the menstrual cycle
menstruation
-bleeding as uterus lining breaks down
what is stage 2 of the menstrual cycle
the uterus lining begins to build up again
what is stage 3 of the menstrual cycle
ovulation
-day 14
an egg is released from the ovaries after it matures and
what is stage 4 of the menstrual cycle
the uterus lining is maintained
is the egg is not fertilised it breaks down and the cycle begins again
what does fsh do
stimulate the maturing of an egg in the ovaries
stimulates release of oestrogen
secreted by pituitary gland
what does oestrogen do
inhibits release of fsh
builds uterus lining
stimulates release of lh
what does LH do
stimulate the release of an egg from ovaries
what does progesterone do
maintains uterus lining
inhibit release of lh and fsh
what is contraception
preventing sperm from meeting egg
what are hormonal methods of contraception
the pill
a patch
an injection
an implant
a plastic intrauterine device
these all release progesterone, oestrogen or both
what are physical methods of contraception
condoms
diaphragms
sterilisation
spermicide
what are the stages of ivf
1.the woman is given lh and fsh
2. the eggs are collected from the ovaries
3. sperm is taken from the male and if fertilised with egg in lab
3. they are left to grow into embryos in the lab
4. when they are ready they are injected back into the uterus
