B3.2 - The Endocrine System Flashcards
Hormones
= chemical messengers made in endocrine glands & secreted into blood
- transported around blood in plasma of blood
- cause response in specific cells found in target organs
What do hormones control:
Body processes that need constant adjustment (body temp) to keep conditions in body constant (homeostasis)
Name endocrine glands & hormones they produce
- thyroid gland = thyroxine
- adrenal gland = adrenaline
- pancreas = insulin
- ovaries = oestrogen & progesterone
- testes = testosterone
- hypothalamus & pituitary gland = hormones that regulate production of other hormones
How do hormones produce responses:
Hormones travel all over body in bloodstream
Only target organs respond
Diffuse out of blood & bind to specific receptors found in membrane/cytoplasm of target cells in target organ
Hormones stimulate target cells to produce response
Endocrine system
= all endocrine glands & hormones they produce
- controls & coordinates body processes with nervous system
Speed of communication for nerves & hormones
N: very fast
H: slower
Method of transport for nerves & hormones
N: electrical impulse along axon of neurone
H: in blood
Duration of response for nerves & hormones
N: short acting
H: longer acting
Area targeted for nerves & hormones
N: very precise area
H: larger area
Thyroxine function & production
- regulates metabolic rate
- controls amount of energy available to cells
- thyroid gland converts iodine into thyroxine by combining it with tyrosine
Adrenaline function & production
- immediately prepares body for intensive action, ‘fight or flight’ response
- adrenal glands(near kidneys) secrete adrenaline in times of stress
Negative feedback
System used in homeostasis to return conditions to the desired level if a change is detected
Negative feedback stages:
- conditions in body change from set point
- change detected by a sensory receptor
- corrective mechanisms activated by an effector
- conditions returned to set point
- corrective mechanisms switched off
…
How are thyroxine levels controlled
- when body requires more energy
- hypothalamus causes pituitary gland to release TSH (thyroid stimulating hormone)
- TSH stimulates thyroid gland to release thyroxine, increases metabolic rate, cells transfer additional energy
- when cells have required amount of energy, hypothalamus inhibits productions of TSH
- thyroid gland stops releasing thyroxine
How are adrenaline levels controlled
When you feel scared/threatened, brain signals adrenal glands to secrete adrenaline, causes body to:
- respire more quickly
- increase rate of breathing to cope with extra demand for oxygen
- increase heart rate
- divert blood away from areas eg.digestive system to muscles
When stress removed, stops
Parts of female reproductive system
- ovary (where eggs mature)
- uterus (where foetus develops)
- cervix (entrance to uterus)
- vagina (receives sperm during sexual intercourse)
- Fallopian tube/oviduct (where egg fertilised before travelling along tube to uterus)
Describe the steps of the menstrual cycle up to ovulation
- uterus starts to thicken ready to receive fertilised egg
- as egg starts to mature in one of ovaries
- 14 days later, egg released from ovary = ovulation
What happens if the egg is fertilised
- may implant in uterus lining
- protected & receives nutrients & oxygen from mother (pregnancy)
What happens if egg isn’t fertilised
- uterus lining & egg removed from body (period/menstruation)
Follicle-stimulating hormone (FSH)
- Secreted by pituitary gland
- Travels to ovaries, causes egg to mature
- stimulates ovaries to produce oestrogen
Oestrogen
- made & secreted by ovaries
- causes lining of uterus to build up
- as levels rise, inhibits production of FSH = prevents more than 1 egg maturing & stimulates pituitary gland to release LH
Luteinising hormone (LH)
- when LH levels peak in middle of cycle, ovulation triggered
Progesterone
- maintains uterus lining
- levels remain high throughout pregnancy
- inhibits LH
2 groups of contraception
- Non-hormonal = barrier methods, prevent sperm contacting egg / physical device, release chemical compounds
- hormonal = use hormones to disrupt normal female reproductive cycle
