edexcel biology unit 7

what are the endrocine glands?

pituitary gland, thyroxine gland, pancreas gland, adrenal gland, ovaries and testes

where are hormones produced?

pituitary gland

what hormones does the pituitary gland produce?

FSH, LH, TSH and ADH

how are hormones transported from endocrine glands to target organs?

hormones are secreted directly into the bloodstream and transported in the blood to target organs/tissues

thyroid gland

produces thyroxine; hormone secreted into the bloodstream and transported in the blood to target cells throughout the body

pancreas gland

produces insulin and glucagon; hormones secreted into the bloodstream and transported in the blood to target organs, mainly liver, muscle, and adipose tissue

adrenal gland

produce adrenaline; hormone secreted into the bloodstream and transported 
in the blood to target organs including heart, blood vessels, liver, lungs, muscles

ovaries

produce oestrogen and progesterone; hormones secreted into the bloodstream and transported in the blood to target organs including uterus, pituitary gland and other reproductive tissues

testes

produce testosterone; hormone secreted into the bloodstream and transported in the blood to target organs including male reproductive organs, muscles and bones

How is adrenalin produced and why?

adrenalin is produced by the adrenal glands to prepare the body for fight or flight via increased heart rate, blood pressure, blood flow to the muscles and raised blood sugar levels by stimulating the liver to change glycogen into glucose

Explain how thyroxine controls metabolic rate as an example of negative feedback (1)

hypothalamus detects thyroxine levels are low and sends TRH signal, pituary gland then releases TSH into blood and causes thyroid gland to pump thyroxine causing metabolism to go up

Explain how thyroxine controls metabolic rate as an example of negative feedback (2)

once body is back to normal, TSH AND TRH are no longer produced to prevent overheating

Describe the stages of the menstrual cycle: days 1-4

Menstruation (uterus lining breaks down and sheds)

Describe the stages of the menstrual cycle: days 5-13

Uterus lining rebuilds (proliferative phase)

Describe the stages of the menstrual cycle: day 14

Day ~14: ovulation (egg released from ovary)

Describe the stages of the menstrual cycle: day 15-28

progesterone keeps the uterus lining thick for pregnancy, or it breaks down if no baby is made

Explain the interactions of oestrogen, progesterone, FSH and LH in the control of the menstrual cycle

FSH matures the eggs and stimulates oestrogen which thicken the uterus lining, stopping FSH and stimulating LH to cause ovulation, progresterone maintains lining and inhibits FSH and LH

Explain how hormonal contraception influences the menstrual cycle and prevents pregnancy

oestrogen/progesterone to stop FSH/LH (no egg release) and thicken mucus (blocks sperm).

Evaluate hormonal methods of contraception: postives

very effective as they regulate cycle and reduce cramps

Evaluate hormonal methods of contraception: negatives

require prescription, side effects (mood changes, weight gain, blood clots risk) and no STI protection

Evaluate barrier methods of contraception: positives

barriers protect against STIs/HIV, no hormones/side effects, cheaper/over-counter,

evaluate barrier methods of contraception: negatives

lower effectiveness, can break/slip, interrupt spontaneity

hormonal methods of contraception examples

vaginal ring, contraceptive implant, contraceptive pill

barrier methods of contraception examples

condoms and diaphragms

what are the uses of assisted reproductive therapy

IVF and clomifene therapy

IVF

FSH/LH injections stimulate multiple follicle maturation/egg production; eggs collected, fertilised in lab, embryos implanted; progesterone supports lining;

Clomifene therapy

drug blocks oestrogen receptors in pituitary to increase FSH/LH,  stimulates ovulation in women with low fertility and used for ART to increase egg release/chances of pregnancy

Explain the importance of maintaining a constant internal environment in response to internal and external change

homeostasis maintains optimal conditions for enzyme activity, cell function, growth; prevents damage from extremes like high temp denatures enzymes or osomis imbalance bursts/shrinks cells

Why is homeostasis important?

thermoregulation and osmoregulation keep core temperature for enzyme efficiency, maintaining blood water and solute balance to prevent cell swelling or shrinking

aspects of thermoregulation

dermis, epidermis, hypothalamus, shivering, vasoconstriction, vasodilation

dermis

contains sweat glands to produce sweat for evaporation to cool blood cells, vasodilation/vasoconstriction and hair muscles to trap air for insulation

role of the epidermis

sweat evaporates from surface causing thin/non-living cells to provide barrier but allow heat loss via convection when vasodilation occurs

Explain how thermoregulation takes place: role of the hypothalamus

acts as thermoregulatory centre as it has receptors detecting blood temperature; coordinates responses via nervous/hormonal signals

Explain how thermoregulation takes place, with reference to shivering

hypothalamus signals skeletal muscles to rapidly contract so respiration increases heat production which helps raise body temperature

Explain how thermoregulation takes place, with reference to vasoconstriction

hypothalamus signals arterioles in dermis to constrict so there isnless blood near skin surface, reduced heat loss by radiation/convection which conserves body heat

Explain how thermoregulation takes place, with reference to vasodilation

hypothalamus signals arterioles to dilate; more blood near skin surface and increased heat loss by radiation/convection which cools body

Explain how the hormone insulin controls blood glucose concentration

After eating pancreas releases insulin; due to high blood glucose and binds to receptors on liver/muscle cells causing glucose taken up for respiration or converted to glycogen which lowers blood glucose

Explain how blood glucose concentration is regulated by glucagon

If low blood glucose, pancreas releases glucagon; glucagon binds to liver cells,  glycogen broken down to glucose,  released into blood; raises blood glucose

Explain the cause of type 1 diabetes

autoimmune destruction of insulin-producing beta cells in pancreas,  no/little insulin produced causing high blood glucose

how is type 1 diabetes controlled?

controlled by insulin injections/pump, balanced diet, monitoring blood glucose

explain the cause of type 2 diabetes

body cells resistant to insulin and/or pancreas producing less insulin leading to high blood glucose, it is also linked to obesity, poor diet, inactivity

how is type 2 diabetes controlled?

controlled by lifestyle changes (diet/exercise/weight loss), sometimes tablets or insulin

Evaluate the correlation between BMI and type 2 diabetes

BMI (obesity, BMI >30) strongly correlates with increased type 2 risk as excess fat causes insulin resistance

Evaluate the correlation between waist:hip and type 2 diabetes

Higher waist:hip ratio correlates with higher type 2 risk as visceral fat causes more insulin resistance/inflammation

Describe the structure of the urinary system

Kidneys (filter blood), ureters (tubes carry urine to bladder), bladder (stores urine), urethra (tube exits body); renal artery/vein supply/remove blood

how is the structure of nephron related to its function?

filtering blood and forming urine, selective reabsorption of glucose and reabsorption of water

Explain the effect of ADH on regulating water content in blood: dehydration

when dehydrated, there is a low water content as the ADH level is high, the collecting duct permability is increases so more water is reabsorbed and a small volume of concentrated urine is produced

Explain the effect of ADH on regulating water content in blood: hydration

hydrated, there is a high water content as the ADH level is low, the collecting duct permability is decreases so less water is reabsorbed and a large volume of dilute urine is produced

Describe the treatments for kidney failure: kidney dialysis

Machine filters blood externally as semi-permeable membrane removes urea/excess ions/water and patient is connected via vein - manages symptoms but not cure

How is urea produced?

produced from the breakdown of excess amino acids in the liver which removes ammonia and converts to ureal for safer excretion