Homeostasis and Response Flashcards
Is the nervous system or the endocrine system faster at acting?
nervous
Name the two types of effectors and state what they do.
The two types of effectors are muscles and glands.
Muscles contract when stimulated, whilst glands release hormones.
What are the 3 main componenets of automatic control systems?
Receptors, Coordination centres and effectors
what do coordination centres do?
interpret a detected change and decide what needs to be done
what do effectors do?
carry out the process to reverse the change
What do receptors do?
detect a change
What is homeostasis?
the regulation of conditions inside the body to maintaining a stable internal environment
What is negative feedback?
the process which does the opposite of the change
Where are the coordination centres located in the body?
brain and spinal cord
What do neurons do?
carry electrical impulses from once place to another
What is a synapse?
the connection between nerve cells
what is needed to connect nerve cells
synapse
How do synapses work?
when an electrical signal reaches the end of a nerve cell, it releases chemicals which diffuse across to the other cell and trigger another electrical signal.
What are sensory neurons?
they are neurons that carry sensory information from receptors to the Central nervous system
What are the 2 parts of the central nervous system?
Brain and spinal chord
What do motor neurons do?
they take electrical signals to effectors to tell them what to do.
What is a reflex arc?
the nerve partway that underlies our unconscious reflexes
What is the benefit of reflex arcs?
they are rapid and automatic
What is a stimuli?
the change detected by the recepetors
What is the full process of the reflex arc?
the receptor cells detect a stimuli which causes the sensory neurons to send electrical signals to the CNS. A relay neuron then sends the electrical signal to a motor neuron which takes it to an effector, which carries out the opposite change.
What is released across a synapse?
chemicals
What is the role of a relay neurone?
To transfer a signal from a sensory neurone to a motor neurone
What is thermoregulation?
the control of our internal body temperature
What temp. does our body have to be kept at?
37 Celsius
why does our body temp have to be optimum?
because if it was lower our enzymes would slow down and if it was higher our enzymes would denature.
Where can you find the thermoregulatory centre?
within the brain.
where are most thermal receptors found in the body?
skin and blood vessels
What does the body do in order to warm us up?
vasoconstriction, make hair stand on end, shivering
what is vasoconstriction and what effect does it have?
the constriction of blood vessels near the skin to prevent heat loss
What effect does our hair standing on end have?
it traps a layer of insulating air to prevent heat loss.
What does the body do to cool down?
vasodilation, sweat
What is vasodilation and what effect does it have?
Vasodilation is when our blood vessels near our skin expand to allow more heat loss
What does sweating do?
when the sweat evaporates off our skin it takes some of the heat energy with it leaving us cooler
Explain how shivering warms the body.
Shivering involves muscles contracting and relaxing automatically. This requires a lot of energy from respiration, which in the process releases a lot of heat energy as waste.
What does the endocrine system allow our body to do?
it allows different parts of our body to communicate with each other
What does the endocrine system consist of?
glands that secrete hormones
what is the pituitary gland also called?
the master gland
What does the pituitary gland do?
it releases lots of different hormones to tell the body what to do or to tell other glands to release their hormones
What hormone does the thyroid gland produce?
thyroxine
Where can you find the thyroid gland?
in your neck
What does the hormone thyroxine do?
regulates the rate of metabolism and also plays an important role in growth and development
What does TSH stand for?
thyroid stimulating hormone
Which gland releases TSH?
the pituitary gland
When will the pituitary gland release TSH?
when it detects low levels of thyroxine
What do the adrenal glands produce?
adrenaline
Where can you find the adrenal gland?
just above the kidneys
What does adrenaline do?
it causes our heart to beat faster in preparation for fight or flight
What hormones does the pancreas produce?
insulin and glycogen
What does insulin do?
regulates blood glucose concentrations
What are the roles of the testes?
to produce testosterone and sperm
What is the main roles of the ovaries?
to produce oestrogen and hold the egg cells
What are the differences in the endocrine system and the nervous system?
endocrine system relies on hormones released into the bloodstream, whereas nervous system relies on electrical impulses through nerve cells. Endocrine system is slower, more general and its effects last longer.
What 2 hormones control our blood glucose levels?
glucagon and insulin
What does insulin do?
decreases our blood sugar levels
how does insulin decrease our blood glucose levels?
It binds to receptors on cells and tells them to take in more glucose. It mostly binds to muscle and liver cells.
Which 2 types of cells take in the most glucose due to insulin?
liver and muscle
How is a lot of glucose stored in a cell?
as glycogen
What is glycogen?
a long term storage form of glucose
Where is glucagon released from?
the pancreas
What does glucagon do?
increase blood glucose levels
How does glucagon increase blood glucose levels?
It binds to lots of cells but mainly liver calls, which take their glycogen and break it down into glucose molecules. They would then release the glucose back into the bloodstream.
What kind of loop do insulin and glucagon make?
A negative feedback loop
Which organ detects changes in blood glucose concentration?
pancreas
What is wrong in the body when someone has diabetes?
cant regulate blood glucose levels properly as the insulin level is all messed up
What is type 1 diabetes and when is it usually discovered?
It is usually discovered in childhood or in teenage years. it is when the pancreas stops producing or produces very little insulin
What is a treatment of type 1 diabetes?
injecting the person with insulin after a meal, usually in the abdomen or thigh
What does the amount of insulin injected depend on?
About of carbs eaten and amount of exercise done
What is type 2 diabetes and when is it usually discovered?
Usually happens to older people with a bad diet over a long time. Their body becomes resistant to insulin (doesn’t respond to it) so their cells wont take in glucose from the bloodstream.
What is the main treatment for type 2 diabetes?
a healthy low sugar diet and consistent exercise
Where is insulin released from?
pancreas
Is type 1 diabetes a temporary, or lifelong condition?
lifelong
What are the main jobs of the kidneys?
to filter the blood and remove waste products
to regulate water and ion levels
What is the main waste product filtered out by kidneys and where is it made?
urea made in the liver during deamination
What is deamination?
excess amino acids being converted to ammonia, which is then converted to urea for safe excretion
What is a nephron?
one of a million such structures in the kidney within which filtration and selective reabsorption take place
What happens within a nephron?
everything small in the blood (e.g. water, glucose, amino acids, urea) diffuses out of the blood and into the tubule
then the things we want (e.g. all of the glucose and some of the water) get reabsorbed into the blood stream (selective reabsorption)
What is filtration?
the process in which all the small molecules in the blood diffuse into the tubule
What is selective reabsorption?
the process in which certain amounts of substances get reabsorbed into our bloodstream from the tubule
How are water levels regulated in the body?
if we have too little water, we produce ADH which makes the blood reabsorb more water from the tubules. If we have too much water we produce less ADH.
What detects conc. of water in our bloodstream and what does it do if its too low or too high?
hypothalamus signals to the pituitary gland to release ADH if too low and if too high, then it stops sending signals so less ADH is decreased.
Where is the hypothalamus found?
in the brain
What are 2 ways ions can be removed from the body?
By sweating
By the kidneys
If we have too much water in the body, what could happen to our cells?
They could gain water and burst
What affect does increased ADH have on urine?
less urine is made
What blood vessels does the blood pass in and out of the kidney?
renal arteries = in
renal veins = out
What is the path of the urine from the kidneys?
kidney
ureter
bladder
urethra
What are the consequences of kidney failure?
waste substances build up in the blood stream
unable to regulate water and ion levels
What are the 2 treatments for kidney failure?
dialysis or kidney transplant
What is a dialysis machine?
an artificial kidney which filters the patient’s blood for them
How does a dialysis machine work?
the patients blood supply is connected to the machine. Dialysis fluid is put across a partially permeable membrane to the blood, letting all the waste products diffuse out of the blood as well as excess water, ions and amino acids.
What does the dialysis fluid contain?
same conc. of water, glucose, ions and amino acids as healthy blood
What happens to the dialysis fluid after a while if not replaced?
reaches equilibrium
Why does the dialysis fluid have to continuously replaced?
to maintain the concentration gradient
What are problems with dialysis?
time consuming
unpleasant experience
expensive
What is the main risk of kidney transplant?
the replacement organ might be rejected
In a dialysis machine, why is it important that the membrane between the blood and dialysis fluid is partially permeable?
To only allow some substances to diffuse across
If a patient has a kidney transplant, what type of drugs are they required to take for the rest of their lives?
Immunosuppressants
What are the main reproductive hormones in men and women?
testosterone in men
oestrogen in women
What does testosterone do and where is it made?
made in the testes, causes sperm production
where is oestrogen produced?
ovaries
What is the average length of the menstrual cycle?
28 days
What are the 4 stages of the menstrual cycle?
stage 1: menstruation
stage 2: build up of lining
stage 3: ovulation
stage 4: maintaining the lining of the uterus
What happens in menstruation and how long does it last?
breaking down of the uterus lining (bleeding) lasts around 4 days
What happens in stage 2 and how long does it last?
lining starts to build up and lasts 10 days
What happens in ovulation and how long does it last?
egg released from the ovaries and lasts 1 day
What happens in stage 4 and how long does it last?
maintaining the lining of the uterus, lasts until the end of the cycle (day 28). if egg is embedded, the menstrual cycle stops and the lining thickens
What are the 4 hormones in the menstrual cycle?
oestrogen, progesterone, LH, FSH
What happens to oestrogen levels through the cycle and why?
levels increase in stage 2 and decrease after stage 3. oestrogen stimulates uterus lining to thicken
What happens to progesterone levels through the cycle and why?
increase in stage 4 and drop at the end of the cycle. Maintains lining of uterus (if levels drop, lining breaks down)
Where are LH and FSH released from?
pituitary gland
Where are oestrogen and progesterone produced?
produced in the ovaries
What does LH do?
stimulate the release of the matured egg
What does FSH do?
stimulate one of the eggs to mature
How do menstrual hormones interact with each other?
FSH stimulates ovaries to produce oestrogen.
oestrogen inhibits FSH
When oestrogen levels get high, they stimulate LH to be produced causing ovulation
progesterone inhibits LH and FSH
Which hormone stimulates the uterus lining to develop?
oestrogen
What is contraception?
any artificial method people use to prevent pregnancy
What 2 hormones do most hormonal contraception pills contain?
oestrogen and progesterone
What are some side effects of contraceptive pills?
headaches and nausea
What does a contraceptive patch do?
releases oestrogen and progesterone slowly for a week
What are 3 hormonal contraceptive methods?
contraceptive patch
pills
IUD
Contraceptive injection
Contraceptive implant
Contraceptive patch
What do most non-hormonal methods of contraception do?
physically prevent sperm from meeting egg
What is an additional benefit of condoms?
protect against STDs
What are 3 non-hormonal methos of contraception?
condom, spermicide, diaphragm, sterilisation,
How can oestrogen act as a contraceptive?
Inhibit FSH production, so that eggs can’t mature
How can progesterone act as a contraceptive?
inhibits FSH and LH
If a women undergoes sterilisation, which structure is cut and tied?
Fallopian tubes
If a man undergoes sterilisation, which structure is cut and tied?
Sperm duct
What methods can be used to get pregnant if a woman is infertile?
use FSH pill to make up for lack of FSH so egg can mature, then take LH pill 14 days later to stimulate egg to be released
Use IVF
What does IVF stand for?
in vitro fertilisation
What are the 4 stages of IVF?
1) woman is given FSH and LH to stimulate eggs to mature
2) eggs collected from woman’s ovaries and fertilised by sperm from father in a lab
3) place fertilised egg in an incubator to allow them to grow into embryo
4) insert embryo into mother’s womb and grow and be born naturally
What are some pros and cons of IVF?
allow infertile parents to have kids
doesn’t always work, often leads to multiple births (higher risk of complications), ethical issues
Why are embryos kept in an incubator whilst in the laboratory?
To provide the optimum temperature for enzymes and thus cell growth
Why do some people think IVF is unethical?
Some embryos (which had the potential for human life) are destroyed
It could lead to ‘designer babies’ if parents can select embryos with certain traits
Where is adrenaline produced?
adrenal glands
Where are the adrenal glands found?
just above you kidneys
When is adrenaline produced?
Adrenaline is produced during the ‘fight or flight’ response, when you get scared, stressed, or need to exercise. It prepares the body for activity.
What effects does adrenaline have on the body?
Increases heart rate
Increases blood pressure
Increases blood flow to muscles
Increases blood sugar (glucose) levels by stimulating the liver to break glycogen down into glucose
Adrenaline causes the conversion of which substances?
Glycogen ➔ glucose
What is thyroxine produced by?
thyroid gland
Where is the thyroid gland found?
in the neck
What does thyroxine do?
increase your metabolic rate
How is the production of thyroxine regulated?
The pituitary gland produces Thyroid Stimulating Hormone (TSH), which stimulates the thyroid gland to produce thyroxine.
Thyroxine then inhibits the production of TSH from the pituitary gland.
Which organ is TSH released from?
Pituitary gland
What plant hormone controls growth in the tips of the shoots and roots?
auxins
What affect do auxins have on shoot and roots?
in shoots they stimulate growth and in roots they inhibit growth
What do photo and geo - tropism mean?
phototropism - response to light
geotropism - response to gravity
Where will auxins accumulate?
the shaded side and the lower side
How do auxins cause shoots to bend towards light?
the light makes the auxins gather at the shaded side causing that side to grow more. Since the far side is growing faster, the shoot will bend towards the light.
shoots are _____ phototropic and _____ geotropic
positively, negatively
Roots are _____ phototropic and _____ geotropic
negatively, positively
True or false? Plant hormones only act locally.
true
what are 3 plant hormones?
auxins, gibberellins, ethene
What are some commercial uses of auxins?
rooting powder (contains auxins) used to grow cuttings
use them to kill weeds
What are some commercial uses of gibberellins?
controlling dormancy (induce germination)
inducing flowering
Growing larger fruit
What does ethene do?
stimulate the ripening of fruit
What is a commercial use of ethene?
ripening fruits after they have been shipped unripened
How can auxins be used as weedkillers?
If large amount of auxins are added to plants, it can disrupt their growth process by overstimulating them. This can kill the plant.
what is the difference between glucose, glycogen, glucagon?
glucose is a carbohydrate
glycogen is the way lots of glucose is stored
glucagon is the hormone that causes glycogen to break down into glucose
What are the 5 main parts of the brain?
cerebral cortex
cerebellum
hypothalamus
brain stem (medulla)
pituitary gland
`What does the cerebral cortex do?
controls consciousness, intelligence, memory, language
What in the brain is the cerebral cortex located?
its the wrinkly tissue around the brain
What does the cerebellum do?
controls balance and muscle coordination.
Where in the brain is the cerebellum located?
small tissue in the lower back of the brain
What does the hypothalamus do?
regulate body temperature and water conc. in blood. Sends signals to pituitary gland
Where are the hypothalamus and the pituitary gland located in the brain?
right in the middle below the cerebral cortex
What does the medulla do?
unconscious activities such as breathing and heart rate.
Where is the medulla located?
at the top of the brain stem
What are the ways scientists study the brain?
study people with brain damage
electrically stimulate different parts in the brain
scanning the brain
Why is treating the brain so hard?
wide range of things that can go wrong
It is encased within the skull, so is hard to access
It is very complicated, so hard to target with medications
What are the characteristics of the cornea?
transparent
no blood vessels
gets all the oxygen it needs from the air through diffusion
What is the function of the cornea?
to refract light rays
What are the characteristics of the iris?
coloured
controls the size of the pupil
What is the function of the lens?
to change shape and thickness in order to refract light different amounts so that its always focused on the retina
What type of cells is the retina made of and what is different about them?
cone cells: colour of the light, doesn’t work well in low light conditions
rod cells: more sensitive, can only see black and white
What is the function of the fovea?
contains only cone cells, which we try to focus light on to see most clearly.
What is the function of the optic nerve?
takes all impulses produced by receptor cells and sends them to the brain
What is the iris reflex?
the increasing in iris size when low light intensity to increase light being received (dilated).
the decreasing in iris size when high light intensity to prevent damage (constricted).
What do the muscles in the eyes do when constricting and dilating?
the contraction of circular muscles and relaxation of radial muscles to constrict pupil.
the relaxation of circular muscles and contraction of radial muscles to dilate the pupil.
What is the pupil?
The gap through which light passes to reach the lens
