Animal Control And Homeostasis Flashcards
What are hormones?
Chemical messages produced by endocrine glands that target organs in the body
What hormones does the pituitary gland secrete?
- TSH, thyroid stimulating hormone
- ADH, antidiuretic hormone
- FSH, follicle stimulating hormone
- LH, luteinising hormone
What hormones does the hypothalamus secrete?
- TRH, thyrotropin-releasing hormone
- CRH, corticotropin-releasing hormone
What hormone does the thyroid gland secrete?
Thyroxine
What hormones do the pancreas secrete?
- Insulin
- Glucagon
What hormone do the testis secrete?
Testosterone
What hormone does the adrenal glands secrete?
Adrenaline
What hormones do the ovaries secrete?
- Oestrogen
- Progesterone
What is the target organ for TRH and CRH?
The pituitary gland
What is the target organ for TSH?
The thyroid gland
What is the target organ for ADH?
The kidneys
What is the target organ for FSH and LH?
The ovaries
What are the target organs for insulin and glucagon?
- Liver
- Muscle
- Adipose tissue
What are the target organs for adrenaline?
Various organs (e.g. heart, liver, skin)
What is the target organ for progesterone?
The uterus
What are the target organs for oestrogen?
- Ovaries
- Uterus
- Pituitary gland
What are the target organs for testosterone?
Male reproductive organs
What is the difference between hormones and nerves?
- Hormones usually have a long lived effect, nerves have a short term effect
- Hormones take longer to work, nerve impulses work very quickly
How does adrenaline affect their body?
- Increases heart rate
- Constricts some blood vessels to make blood pressure higher
- Dilates other blood vessels to increase blood flow to muscles
- Causes the liver to convert glycogen to glucose which is released into the blood
How does increasing heart rate help the body in a ‘fight or flight’ situation?
- Heart beating faster means oxygen is being carried around the body faster
- This allows faster respiration in muscle cells
- Which means energy is released for cell contraction faster
What are the stages of the menstrual cycle?
- Menstruation, days 1-5, the breakdown of the uterus lining
- Uterus building, days 6-13, the lining of the uterus is gradually built up
- Ovulation, day 14, the release of an egg from an ovary
- Fertile window, days 14-16, when fertilisation is most likely to take place
- Uterus building, days 17-28, the lining of the uterus continues to build up
- If fertilisation occurs then the uterus lining is maintained and menstruation doesn’t happen
What are the different types of hormonal contraception?
- Hormone pills
- Hormone implants
- Hormone injections
How does hormonal contraception work?
- Release hormones to prevent ovulation
- Thickens mucus at the cervix which prevents sperm from passing
What are the different types of barrier contraception?
- Condoms
- Diaphragm
- Caps
- Sponges
What are the advantages and disadvantages of hormonal contraception?
Advantages
- More than 99% effective
- Can reduce the risk of certain cancers
Disadvantages
- Possible side effects such as changes in weight, mood and blood pressure
- Do not protect against STI’s
What are the advantages and disadvantages of condoms?
Advantages
- 98% effective is used properly
- Quick and easy to use
- Protect against STIs
Disadvantages
- Risk of tearing or ripping
- Not as effective as hormonal contraceptives
Why is it important to control body temperature?
Enzymes in the main organs are most active at this temperature
How does the structure of skin help thermoregulation?
- Releases sweat when warm to lose heat by evaporation
- Contract when cold to pull hair upright, this traps an insulating layer of air - Vasodilation/vasoconstriction changes blood flow through surface capillaries depending on temperature
How does the dermis of the skin help cool the body?
- Sweat glands in the dermis secrete sweat onto the the epidermis, this evaporates and cools the body down
- Muscles in the dermis relax which allows hair follicles to lie flat, this means there’s a thinner layer of insulating air trapped against the epidermis
What is the cause of type 1 diabetes?
- The immune system has damaged the persons insulin-secreting pancreatic cells
- This means they do not produce insulin
How do you control type 1 diabetes?
- Inject insulin into the fat just below the skin
- They must work out the right amount of insulin to inject so the blood glucose concentration stays within safe limits
What is the cause of type 2 diabetes?
- The person does produce insulin but their liver and muscle cells have become resistant to it
How do you control type 2 diabetes?
- Most people can control their blood glucose concentration by eating lower sugar foods exercise
- Medication is sometimes needed
How do you work out BMI?
BMI = weight (kg) / height ² (m)
How does negative feedback control thyroxine levels?
- Low concentration of a thyroxine in blood stimulate corrective mechanism
- Hypothalamus releases TRH which causes the pituitary gland to release TSH
- This causes the thyroid gland to release more thyroxine so blood levels return to normal
- Normal thyroxine levels inhibit TRH and TSH so less thyroxine is produced and normal blood levels are maintained
How do FSH LH oestrogen and progesterone interact to control the menstrual cycle?
- FSH causes a follicle to mature in the ovary
- As the egg matures, the follicle produces oestrogen
- Oestrogen grows the lining of the uterus wall
- Oestrogen inhibits FSH
- When oestrogen rises enough it causes a surge in LH
- LH causes ovulation from the follicle
- The ruptured follicle becomes the corpus luteum
- This produces oestrogen and progesterone
- Progesterone inhibits FSH and LH
- Progesterone maintains the uterus lining
- If the egg has not been fertilised corpus luteum dies and progesterone levels drop, this causes menstruation
- FSH is no longer inhibited so can be secreted from a pituitary gland again
When is IVF used?
- Issue with the quality of the man’s sperm
- Woman has blocked oviducts
How does IVF work?
- FSH and LH are given to the mother to stimulate the maturation of several eggs in the ovary
- The eggs are collected from the mother and fertilised in a dish
- The fertilised eggs developed into embryos
- When the embryos are tiny balls of cells, one or two are inserted into the mother’s uterus
When is clomifene used?
When a woman can’t ovulate
How does clomifene work?
- Stimulates ovulation
- Blocks the action of oestrogen as negative feedback on LH, so more LH is released in a surge
What temperature is the human body kept at and why?
37° C because it is the temperature that enzymes work best in
How does thermoregulation work if the body temperature rises?
- The hypothalamus detects the rise and causes a response
- More blood flows near skin surface
- Sweat glands release more sweat onto skin surface to evaporate
- Sebaceous glands produce oil that helps sweat spread out over skin
- These increase the transfer of energy to surroundings to decrease body temperature
How does thermoregulation work body temperature falls?
- Hypothalamus detectable and causes a body response
- Less blood flows near skin surface
- Sweat glands stop producing sweat
- Body hair raised by erector muscles in the dermis which trap a layer of insulating air (causing goosebumps)
- Skeletal muscles contract rapidly, these need energy from respiration which is then released as heat
- Reduces transfer of energy to surroundings
What is vasoconstriction?
- Cold environment
- Arteriole (surface capillary) becomes constricted and gets narrower
- Shunt vessel (deep skin blood vessel) dilates
- Warm blood is kept deeper in the skin so less heat is transferred to air
What is vasodilation?
- Warm environment
- Arteriole (surface capillary) becomes dilated
- Shunt vessel (deep skin blood vessel) narrows
- Increases flow of warm blood near skin so heat can transfer easily to air
Why is osmoregulation important?
- To keep the concentrations the same inside the cells as around them
- Protects cells by stopping too much water from entering or leaving them by osmosis
What is a hypotonic cell?
When there is a more dilute solution outside the cell, it causes them to swell then burst
What is a hypertonic cell?
When there is a more concentration solution outside the cell, it causes them to shrivel
How does the body digest proteins?
They are broken down by protease enzymes into amino acids in the stomach and small intestine
How is urea produced?
The process of breaking down excess amino acids produces ammonia which is immediately converted to urea
How is urea excreted from the body?
- Urea is released from the liver cells into the bloodstream
- It is transported to the kidneys where the blood is filtered
- The urea is then passed out the body in urine
How does the body respond to a rise in blood glucose concentration?
- The pancreas detects a rise
- It increases the secretion of insulin and decreases secretion of glucagon
- Insulin causes muscle and liver cells to remove glucose from the body and store it is glycogen for storage
- This causes the blood glucose concentration to fall
How does the body respond to a fall in blood glucose concentration?
- The pancreas detects a fall
- It decreases secretion of insulin and increases secretion of glucagon
- Glucagon causes liver cells to convert glycogen to glucose and release it into the blood
- Blood glucose concentration rises
How do you work out waist:hip ratio?
Waste measurement/
Hip measurement
Should be:
Under 0.85 for women
Under 1 for men
What is the role of the renal vein?
Carries deoxygenated/cleaned blood away from the kidneys, back to the circulatory system
What is the role of the renal arteries?
Carries oxygenated blood from the body to the kidneys
What is the role of ureters?
Carry urine from the kidneys to the bladder
What is the role of the urethra?
The tube that carries urine out of the body
What are nephrons?
Microscopic tubules responsible for cleaning the blood
 Each kidney contains over a million
What is the first stage in the kidney?
Filtration:
- Blood passes through the glomerulus (small knot of many capillaries)
- The blood is under high pressure at the start which helps the ultrafiltration
- Small molecules, including water ions, are passed into the Bowman’s capsule then the nephron tubule
- Large molecules, such as blood proteins, cannot filter so stay in the blood
What is the second stage in the kidneys?
Selective reabsorption:
- The kidneys must reabsorbed the molecules which are needed
What is stage three in the kidneys?
The formation of urine:
- The molecules that are not selectively reabsorbed continue along the nephron tubule as urine
Which molecules are absorbed in selective reabsorption?
- Glucose
- As much water as the body needs to maintain constant water level in blood plasma
- As many ions of the body needs to maintain a constant balance of mineral ions in blood plasma
Where does selective reabsorption take place?
- The first convoluted tubule
- The loop of Henle (where most of the water is reabsorbed)
- The second convoluted tubule
How does the body respond to low concentration of water in blood plasma?
- The pituitary gland secretes more ADH
- More ADH makes the collecting ducts more permeable
- So more water is reabsorbed from the kidney tubule back into the blood
- A small volume of concentrated urine is produced
How does the body respond to high concentrations of water in the blood plasma?
- The pituitary gland secretes less ADH
- Less ADH makes the collecting ducts less permeable
- So less water is reabsorbed from the tubule back into the blood
- A large volume of dilute urine is produced
What does dialysis fluid contain?
- A glucose concentration similar to a normal level in blood
- A mineral ions concentration similar to a normal level in blood
How does dialysis work?
- Unfiltered blood that is high in urea is taken from the arm
- It is mixed with blood thinners to prevent clotting and then pumped into the dialysis machine
- The blood and dialysis fluid are separated by partially permeable membrane
- There is a large concentration gradient so the urea diffuses out of the blood into the fluid
Why does the dialysis fluid contain a similar concentration of useful substances as the blood?
So the dialysis fluid and blood of the same concentration and no glucose or mineral ions are lost
What are the advantages of dialysis?
- Greatly reduces the levels of urea
- No overall change in blood glucose levels
- The correct water and ion balance are maintained or restored
What are the disadvantages of dialysis?
- Requires highly specialised and extensive machinery
- The patient must be connected to the machine often and for long periods at a time
What is the problem with kidney transplants?
- The antigens on the transplanted kidney cells are different from the antigens on cells in the patient’s body
- This causes the immune system to quickly form antibodies against the kidney (organ rejection)
What are the two ways to prevent rejection?
Tissue typing:
- A kidney with antigens that are very similar to the patient is used
Immuno-suppressant drugs:
- These must be taken for the rest of their lives, they reduce the immune response against the donor kidney
What is the disadvantage of tissue typing?
- Possible long waits for transplants
- Patients must undergo dialysis until then and could die before a match is found
What is the disadvantage of immuno-suppressant drugs?
They also suppress the immune response against pathogens which increases the risk of infection
