homeostasis and response

Question 1

what happens to amino acids that cannot be stored in the body?

Answer 1

• amino acids are broken down to form urea in the liver
• the kidneys filters the blood which removes all urea from the blood
• the urea is stored in the bladder and excreted in urine

Question 2

describe how the water content of the blood is controlled

Answer 2

• the hypothalamus detects if the water content in the blood is to low and sends signals to the pituitary gland to release more ADH into the blood
• this increases the permeability of the kidneys, causing the kidney to reabsorb more water back into the blood so a smaller volume of more concentrated urine is produced
• if water content is too high then less ADH is released from the pituitary gland into the blood which decreases the permeability of the kidneys, so less water is reabsorbed by the kidneys into the blood
• so a larger volume of more dilute urine is produced
• this is controlled by negative feedback

Question 3

why are there excess amino acids in the body and how can they be excreted

Answer 3

• the digestion of protein from the food we eat results in excess amino acids
• the amino acids are deaminated in the liver to form ammonia
• ammonia is toxic so is immediately converted to urea for safe excretion
• urea is filtered out of blood by kidneys and stored in bladder

Question 4

why is there a higher concentration of urea and ions ona hot day than on a cold day?

Answer 4

• on a hot day more water is reabsorbed as more water is lost in sweat, so there is a lower volume/less water in the urine

Question 5

how do the hormones insulin and glucagon control a person’s blood glucose after a meal

Answer 5

• blood glucose increases after a meal which is detected by receptors on pancreas, so the pancreas secretes insulin
• insulin causes glucose to move into cells (so there is less glucose in the blood)
• insulin causes glucose to be converted to glycogen which is stored in muscles and liver
• so therefore the blood glucose decreases causing glucagon secretion from pancreas
• glucagon causes glycogen to be converted to glucose and released into the blood (so there is more glucose in the blood)

Question 6

what is type 1 diabetes and how is it treated?

Answer 6

• type 1 diabetes is a disorder where the pancreas produces no/not enough insulin which causes the person to have uncontrolled high blood glucose levels
• treatment = insulin injections

Question 7

what is type 2 diabetes and how is it treated?

Answer 7

• type 2 diabetes is where cells do not respond to insulin produced by the pancreas and obesity is a risk factor
• treatment = carbohydrate controlled diet (less carbohydrates and sugars) and more exercise

Question 8

how do hormones control the menstrual cycle?

Answer 8

• FSH is released from the pituitary gland and stimulates the maturation of egg and stimulates the ovaries to produce oestrogen
• oestrogen is released from the ovary and inhibits FSH production and stimulates LH production
• LH is released from the pituitary gland and stimulates ovulation (release of egg from ovary)
• progesterone is released from ovary and inhibits FSH and LH production
• oestrogen and progesterone maintain the uterus lining

Question 9

how does oestrogen act as a method of contraception?

Answer 9

• when taken daily oestrogen prevents the release of an egg and the levels of oestrogen are permanently high so inhibits FSH and after a while egg development and production stays stopped

Question 10

how does progesterone act as a method of contraception?

Answer 10

• reduces fertility by stimulating the production of thick mucus which prevents the sperm reaching and fertilising an egg

Question 11

how does oral contraceptives act as a method of contraception?

Answer 11

• contains the hormones oestrogen and progesterone to inhibit FSH production so that no eggs mature

Question 12

how does the implant and IUD and patch act as a method of contraception?

Answer 12

• slowly releases a continuous amount of progesterone to inhibit the maturation and release of eggs for a number of months or years
• IUD releases progesterone
• patch contains oestrogen and progesterone and lasts 1 week

Question 13

what hormones are given to women in a fertility drug and why

Answer 13

• the hormones FSH and LH are given to women in a fertility drug to stimulate egg maturation and release so she can become pregnant in the normal way

Question 14

describe IVF treatment-

Answer 14

• give a mother FSH and LH to stimulate the maturation of several eggs
• the eggs are collected from the mother and fertilised by sperm from the father in the laboratory
• the fertilised eggs develop into embryos
• at the stage when the embryos are tiny balls of cells, one or two embryos are inserted into the mother womb

Question 15

what are the disadvantages of IVF?

Answer 15

• emotionally and physically stressful
• success rates are low which is why multiple embryos are implanted at the same time
• can lead to multiple births which are a higher risk to both the babies and the mother than just one baby, as multiple embryos are implanted
• its expensive for women and NHS if process needs to be repeated (only allowed to try a few times if NHS are paying)

Question 16

how does adrenaline affect the body?

Answer 16

• increases heart rate
• increases delivery of oxygen and glucose to cells and tissue (increases blood flow and causes liver to convert glycogen into glucose)

Question 17

what would happen in the body of a person with hyperthyroidism?

Answer 17

• too much thyroxine is released into the blood
• which raises BMR
• causing an increase in formation of glycogen, lipids, and proteins