SB7: animal coordination, control and homeostasis Flashcards
hormone
a chemical messenger that travels around the body through blood to make a change
what happens when a hormone has been used?
it is destroyed by the liver
endocrine vs nervous svstem
-electrical (n), chemical (e)
-neurones (n), bloodstream (e)
-muscle contraction (n), chemical change (e)
-very rapid response (n), slow response (e)
short till response nerve impulses stop (n), long response till hormone is broken down (e)
pituitary gland
-at the base of the brain
-target organ = kidney (ADH)
-controls the water content of the blood
how can the pituitary gland increase thyroxine?
- the pituitary gland detects low levels of thyroxine
- hypothalamus releases TRH
- this causes the pituitary gland to release TSH which gets the levels back to normal
what do normal thyroxine levels do?
-inhibit TRH release from the hypothalamus and the production of TSH by the pituitary
-normal blood levels are maintained
why is the pituitary gland called the master gland?
-produces many different hormones, some of these give instructions to the body & others make other glands release hormones
adrenal glands
-on top of both kidneys
-produce adrenaline
-prepare you for fight and flight
thyroid gland
-releases thyroxine
-regulates rate of metabolism
-important role in growth and development
underactive thyroid
-thyroid gland produces thyroxine which helps regulate metabolic rate
-low levels of thyroxine stimulate the production of TRH
-TSH is then released which leads to thyroxine being released
-an under active thyroid wouldn’t produce enough thyroxine
-metabolic rate would drop & less calories would be available for tasks
-more fat would be stored for energy, body mass increases
pancreas
-produces insulin
-controls blood glucose levels
male glands
-testes (testosterone - controls puberty & produces sperm)
female glands
-ovaries (oestrogen- influences puberty & the menstrual cycle)
-hold egg cells
homeostasis
the maintenance of constant internal conditions in an organism
negative feedback system
- conditions in the body change from set point
- change detected
- corrective mechanisms activated
- conditions returned to set point
- corrective mechanisms switched off
how does the hypothalamus control body temperature? (simple)
-if your body gets too hot, your body begins to sweat, which reduces body temperature
-if the body gets too cold, your body begins to shiver to raise body temperature
thyroxine
-produced from the thyroid gland, which stimulates the metabolic rate
-controls the speed at which oxygen and food products react to release energy for the body to use
how are thyroxine levels controlled? (negative feedback)
- low thyroxine levels in the bloodstream stimulate the hypothalamus to release TRH and this causes the pituitary to release TSH so the thyroid releases more thyroxine -> blood levels return to normal
- normal thyroxine levels in the bloodstream inhibit TRH release from the hypothalamus and the production of TSH by the pituitary, so normal blood levels are maintained
is adrenaline controlled by negative feedback?
no
when is adrenaline released?
in times of fear or stress
what are the effects of adrenaline in the bloodstream?
- increases breathing rate, heart rate (therefore blood flow) and blood pressure
- increased conversion of glycogen to glucose in liver cells, increasing blood glucose
this means the body has more energy being released by respiration & more glucose getting to the muscles
puberty
period of sexual maturation:
facial hair = men
breasts = women
regulating blood glucose
- glucose is absorbed from the small intestine after the digestion of food
- blood glucose concentration rises
- pancreas responds to high blood glucose by releasing insulin
- insulin causes cells in the liver to take in glucose
- insulin causes liver, muscle & other cells to take up glucose & change it to glycogen to storage
- blood glucose concentration falls to another level
diabetes
blood glucose levels can’t properly be controlled by the body
type 1 diabetes
-the pancreas doesn’t produce enough insulin
-characterised by high blood glucose levels
how can blood sugar levels be controlled in people with type 1 diabetes?
-being careful with their diet: eating foods that won’t cause large increases in blood sugar level
-exercising: which can lower blood glucose levels due to increased respiration in the muscles
-injecting insulin
type 2 diabetes (solutions)
-the person’s body cells no longer respond to insulin produced by the pancreas
-more common in older people
-controlled by a carbohydrate controlled diet and an exercise regime
-carbohydrate is digested into glucose, which raises the overall blood glucose level
what has a correlation to type 2 diabetes?
rising body mass levels in the population
BMI formula
weight (kg) / height^2 (m^2)
who has increased risk of type 2 diabetes?
-overweight (BMI = 25-30) and obese
people (BMI =30+)
-people with more weight around their waist are at more likely to develop certain illnesses than people who have more weight around their hips
(waist:hip ratio of over 0.85 in women & over 1 in men indicates obesity)
waist:hip ratio
waist measurement / hip measurement
how to increase blood glucose levels (negative feedback)
-if the blood glucose level is too low, the pancreas releases the hormone glucagon
-this travels to the liver through the blood and causes the break-down of glycogen into glucose
-the glucose enters the blood stream and glucose levels increase back to normal
menstrual cycle
the lining of the uterus is prepared for pregnancy, if implantation of the fertilised egg into the uterus lining does not happen, the lining is then shed (28 days)
how hormones work together in the menstrual cycle
- FSH is secreted from the pituitary gland and causes the follicle to mature
- as the follicle matures, it secretes oestrogen, which inhibits FSH & starts to thicken the uterus lining
- a high concentration of oestrogen causes a surge in LH which causes ovulation (egg is released from follicle
- ruptured follicle becomes corpus luteum & secretes progesterone & some oestrogen
- the lining thickens more
- progesterone inhibits FSH & LH
- if the egg isn’t fertilised, the corpus luteum breaks down
- progesterone & estrogen fall, menstruation begins
- FSH can be produced again
oral contraception (the pill)
-contains estrogen or progesterone or a combination of both hormones
-these hormones inhibit the production of FSH and eggs cannot mature
benefits & risks of oral contraception
benefits:
-more than 99% effective if taken correctly
-can reduce the risk of certain cancer
risks:
-changes in weight, mood and blood pressure due to high levels of ostrogen
physical barrier contraceptions: descriptions their risks
condoms
-prevent sperm from reaching the egg
-easy & quick to use but can rip
diaphragm
-prevent sperm from reaching the egg
-diaphragms need to be put in just before sex and left in several hours afterwards
IUD (coil) & risks
-prevent the implantation of an embryo or release of a hormone
-need to be fitted by a health professional
-IUD can remain in position for up to 10 years, however there is a small risk of causing an ectopic pregnancy
ectopic pregnancy
a pregnancy outside of the womb
spermicidal agents & risks
-kill or disable sperm
-some people can have allergic reactions to these
vasectomy & risks
-the sperm ducts are cut and tied
-non reversible
ART (assistive reproductive technology)
-the use of hormones and procedures, as fertility treatments, to help to achieve pregnancy
how do fertility drugs work?
-contain FSH and LH, which stimulate eggs to mature in the ovary
fertility treatments
-increase a woman’s chance of becoming pregnant, although the treatment may not always work
-because the treatment boosts the production of mature eggs, it increases the chance of twins or triplets
-multiple pregnancies carry a risk of complications -> premature or underweight babies
IVF
1) a mother is given FSH and LH, to stimulate the maturation of several eggs in the ovary
2) the eggs are collected from the mother and fertilised by sperm from the father in a dish in the laboratory
3) the fertilised eggs develop into embryos & are inserted into the mother’s uterus
clomifene
fertility drug; stimulates ovulation in women who can’t ovulate by blocking oestrogen’s negative feedback on LH
what temp does the body stay at & why?
37 degrees as the body works best then, if higher enzymes will denature
thermoregulatory centre
area of the hypothalamus that monitors core body temperature and acts as the body’s thermostat
three layers of skin
epidermis, dermis, fatty tissue
what happens when we get too hot?
sweat glands in the dermis release more sweat onto the surface of the epidermis, the sweat evaporates, transferring heat energy from the skin to the environment
what happens when we get too cold?
-skeletal muscles contract rapidly and we shiver, these contractions need energy from respiration, and some of this is released as heat
-nerve impulses are sent to the hair erector muscles in the dermis, which contract
-this raises the skin hairs and traps a layer of insulating air next to the skin
how is the amount of blood flowing through the skin capillaries altered?
vasoconstriction & vasolidation
what is vasoconstriction?
narrowing of blood vessels when it’s too cold, to decrease blood flow and decrease heat loss from skin
what is vasodilation?
widening of blood vessels when it’s too hot, to increase blood flow and increase heat loss from skin
osmoregulation
the control of water levels and mineral ions in the blood
why is osmoregulation important?
-water levels and mineral ions in the blood are controlled to keep the concentrations the same inside the cells as around them
-this protects cells by stopping too much water from entering or leaving them by osmosis
-if body cells lose or gain too much water, they do not function efficiently
how is water lost from the body?
-sweat
-water vapour from exhaling
-urine
what happens when proteins are digested?
-there are excess amino acids that have to be excreted safely
-in the liver deamination happens to form ammonia, ammonia is toxic cannot be allowed to accumulate in the body, so it’s converted into urea for safe excretion, released into the bloodstream & transported to the kidneys where blood is filtered & urea comes out in the urine
how are proteins broken down?
proteases in the stomach & small intestine
maintaining water balance in the body (kidney)
-the kidneys produce urine and this helps keep water balance
-urine is taken from the kidneys to the bladder by the ureters
-the bladder stores the urine until it is convenient to expel it from the body
kidneys function
-to filter blood and remove waste products
-to regulate the levels of useful substances
how does blood enter the kidney & what happens?
renal artery:
-blood taken to the kidney through the renal artery
-the blood is filtered at high pressure and the kidney reabsorbs any useful materials
how does blood leave the kidney & what happens?
renal vein:
-after purified, the blood returns to the circulatory system through the renal vein
ureter
tube that carries urine from the kidney to the bladder
urethra
duct through which urine is discharged
urine contains…
water, urea, mineral ions
nephrons
-clean the blood by removing waste
-made of tubules
-over one million in each kidney
glomerulus
tiny ball of capillaries in the kidney
filtration in the kidney
-blood passes into capillaries in the kidney
-the blood is under high pressure at the start of the nephron & helps the filtration of the blood
-small molecules (urea, water, glucose) are squeezed out and pass into the nephron tubule but, large molecules, are too big to fit through the capillary wall and remain in the blood
selective reabsorption in the kidney
-the kidneys must reabsorb the molecules which are needed
-kidneys allow unneeded molecules to pass out to form urine
the reabsorbed molecules include:
-glucose
-as much water as the body needs to maintain a constant water level in the blood
-as many ions as the body needs to maintain a constant balance of mineral ions in the blood
the formation of urine in the kidney
-the molecules that aren’t reabsorbed continue along the nephron tubule as urine, this passes down to the bladder
how is water concentration controlled by the pituitary gland?
-more ADH is released by the pituitary gland when the blood is too concentrated, kidney tubules become more permeable -> more water is reabsorbed into the blood during selective reabsorption
-if too much water is detected in the blood
-less ADH will be released
-less water will be reabsorbed and a dilute and larger volume of urine will be produced
what is negative feedback?
a type of regulation that responds to a change in conditions by initiating responses that will counteract the change, maintains a steady state
what is positive feedback?
a type of regulation that responds to a change in conditions by initiating responses that will amplify the change, takes organism away from a steady state
kidney damage/disease
damage from accidents or disease can lead to a build-up of poisonous wastes in the body
total kidney failure & treatments
-when both kidneys stop working due to disease or damage
-humans can survive with one kidney, but for people who suffer from total kidney failure this would be fatal if not treated
-treatment can be by organ transplant or by kidney dialysis
kidney dialysis
-patients are connected to a dialysis machine which is an artificial kidney & removes most of the urea & restores/ maintains the water and ion balance of the blood
-patients with kidney failure can be kept alive by using kidney dialysis until a transplant becomes available
how does kidney dialysis work?
-unfiltered blood that’s high in urea is taken from a blood vessel in the arm, mixed with blood thinners to prevent clotting & pumped into the dialysis machine
-in the machine, the blood & dialysis fluid are separated by a partially permeable membrane
-the dialysis fluid has no urea, so there is a large concentration gradient, urea moves across the partially permeable membrane, from the blood to the dialysis fluid, by diffusion, urea is removed from the patients’ blood
-the dialysis fluid has a glucose conc equal to a normal blood sugar level, the patients’ retain glucose (for respiration) as there is no gradient
-as the dialysis fluid contains a mineral ion conc similar to the ideal blood plasma concentration, movement of ions across the membrane only happens where there is an imbalance
-if the patient’s blood is too low in ions, they will diffuse from the dialysis fluid into the blood, restoring the ideal level in the blood +vice versa
what does dialysis fluid contain?
-a glucose concentration similar to a normal level in the blood
-a concentration of mineral ions similar to that found in normal blood plasma
-no urea
dialysis advantages and disadvantages
advantages:
-greatly reduced levels of urea
-no overall change in blood glucose levels
-the correct water and ion balance maintained or restored
-available to all kidney patients
disadvantages:
-expensive machinery
-time consuming and restrictive, as this mainly happens in hospital (patient must be connected to this machinery 2-3x a week for between 4-6 hours at a time)
-filtration only works when they are connected, kidney patients must monitor their diet carefully in between dialysis sessions -> avoid eating foods with a high protein content
-dialysis will only work for a limited amount of time before a transplant is needed, and sadly many patients will die before a suitable one is found
kidney transplants
-implanting a kidney from an organ donor into the patient’s body to replace the damaged kidney
-the donor kidney cells will have protein antigens on their surface
-bc of these different in the antigens of the donor, the immune system would quickly form antibodies against the kidney cell antigens, and would destroy the kidney
-this is known as organ rejection & is potentially very harmful for the patient
precautions against rejection
tissue typing:
-a kidney is given to patients who have antigens that are very similar to the antigens of the donor kidney
-this can lead to long waits for transplants while compatible donors become available
-during which time patients must undergo dialysis, and in some cases they will die before a match is found
immuno-suppressant drugs:
-these drugs must be taken by transplant patients for the rest of their lives
-they suppress the immune system, greatly reducing the immune response against the donor kidney, but they also suppress the immune response against pathogens which enter the body, increasing the risk of infections
transplant advantages and disadvantages
advantages:
-patients can lead a more normal life without having to watch what they eat and drink
-cheaper for NHS
disadvantages:
-must take immune-suppressant drugs which increase the risk of infection
-shortage of organ donors
-kidney only lasts 8-9 years on average
-any operation carries risks
