Biology - nerves, hormones and homeostasis Flashcards
what are hormones
chemical messengers released from endocrine glands that travel in blood plasma
hormones will only have an effect on specific cells, which we call target cells
how are nerves and hormones different
hormones are slower
act for a longer period of time
more general effects
hormones limited by speed of blood passing around the body
thyroxine
- important for regulating basal metabolic rate
- thyroid stimulating hormone (TSH) controls release of thyroxine through negative feedback
- level in blood monitored by hypothalamus
what happens when thyroxine is too high
- TSH released by pituitary gland is inhibited
- less thyroxine is released from thyroid gland
- level falls back to normal
what happens when thyroxine is too low
- TSH is released by pituitary gland
- more thyroxine is released from thyroid gland
- level increases back to normal
what is adrenaline
- released by adrenal glands
- responsible for fight or flight response
what does adrenaline do
- increases heart rate
- stimulate liver to break down glycogen to use glucose for energy
- increases breathing rate
- causes dilation of vessels to direct blood to muscles
- causes pupils to dilate
oestrogen
main female reproductive hormones and produced in the ovaries
testosterone
main male reproductive hormones and is produced in the testes
follicle stimulating hormone (FSH) function
- produced by pituitary gland
- acts in ovary
- stimulates ovaries to develop follicle containing an egg and produce oestrogen
oestrogen function
- produced by ovaries
- stimulates uterus lining to thicken
- inhibits FSH and LH
luteinising hormone (LH) function
- produced by pituitary gland
- acts on ovaries
- stimulates mature follicle to release egg around day 14 (ovulation)
progesterone function
- secreted by empty follicle in ovary (corpus luteum)
- maintains the lining of the uterus so that the fertilised egg can implant
- inhibits LH
- decrease levels cause the lining to break down (menstruation)
hormonal contraception
- oral pill
- skin patch
- implant
- injection
- intrauterine devices
oral pills (combined or progesterone only)
- not 100% effective
- side effects, e.g. nausea, headaches
- does not protect against STDs
- need to take every day
skin patch
- same hormones as combined pill
- patch changed every week
implant
- lasts up to 3 years
- continuous amount of progesterone
injection
lasts up to 3 months
intrauterine devices
- T-shaped device inserted into the uterus
- stops implantation and plastic IUDs release progesterone
non-hormonal methods
- barrier methods
- natural methods
- intrauterine devices
- surgical methods