homeostasis and response Flashcards
what is homeostasis?
homeostasis is the regulation of the internal conditions of a cell or organism in response to internal external changes.
why is homeostasis important?
homeostasis keeps conditions constant for enzyme action and cell functions
homeostasis is in control of:
- blood glucose concentration
- body temperature
- water and ion levels
control systems of homeostasis involve:
- responses using nerves
- chemical responses using hormones
control systems include:
- cells called receptors
- coordination centres
- effectors
what do receptors do?
they detect stimuli
stimuli
changes in the environment
coordination centres examples
brain, spinal cord, pancreas
what do coordination centres do?
receive and process information from receptors
effectors examples:
muscles, glands
what do effectors do?
bring about responses that restore optimum levels
negative feedback is a
type of control mechanism
in negative feedback:
- receptor detect a change in stimulus
- coordination centre compares stimulus to a set point
- effector then produces a response to correct any difference from the set point
what does the nervous system do?
the nervous system enables humans to react to their surroundings and co-ordinate their behaviour
what does the central nervous system do:
-co-ordinates the response of effectors
muscles contracting
CNS:
brain and spinal cord
reflex actions:
1) pain=stimulus-detected by surroundings
2) impulses from receptors pass along sensory neurone to CNS
3) impulse passes through a relay neurone
4) a motor neurone carries on impulse to the effector
5) the effector responds
neurones are not..
directly connected to each other
neurones communicate via..
synapses (gaps)
glands:
produce hormones in the body
main glands:
pituitary gland thyroid gland pancreas adrenal gland testis ovary
pituitary gland is in the
brain
thyroid gland is in the
throat
pancreas is in the
stomach
the endocrine system:
made up of glands that secrete hormones directly into the bloodstream
hormones are..
chemical messengers that are carried in blood to a target organ where they produce and effect.
how is blood glucose controlled?
monitored and controlled by the pancreas
if blood glucose levels are too high:
- pancreases releases more insulin
- insulin causes glucose move from blood into the cells
- in liver and muscle cells, excess glucose is convected to glycogen for storage
adrenaline is produced:
by the adrenal glands in times of fear and stress
what does adrenaline do?
- increases heart rate, boosting the delivery of oxygen and glucose to the brain and muscles
- prepares body to flight/fight
thyroxine is produced in the…
thyroid gland
what does thyroxine do?
- increases metabolic rate
- controls growth and development in young animals
- controlled by negative feedback
type 1 diabetes is caused…
by pancreas failing to produce sufficient insulin
type 1 diabetes results in..
uncontrolled high blood glucose levels
type 2 diabetes is caused…
by body cells no longer responding to insulin
type 2 diabetes risk factor:
obesity
type 2 diabetes is treated..
with carbohydrate controlled diet and regular exercise
sex hormones:
- oestrogen (female)
- testosterone (male)
oestrogen
-at puberty, eggs begin to mature and be released
ovulation
4 hormones which control menstrual cycle:
FSH, LH, oestrogen, progesterone
where is FSH and LH produced
pituitary gland
where is oestrogen and progesterone produced
ovaries
what does FSH do
stimulates the maturation of eggs in the ovary
-> produce oestrogen a
what does LH do
stimulates the release of the egg
ovulation
what does oestrogen do
thickens uterus lining
inhibits FSH release
stimulates LH release
what does progesterone do
maintains lining of uterus
inhibits both FSH and LH release
how can you reduce fertility
variety of methods of contraception
hormonal contraception
- oral contraceptives (pill)
- injection
oral contraceptives (pill)
contains oestrogen and progesterone
injection
slows release of progesterone to stop realise of eggs
months or years
non hormonal contraceptives
- barrier methods
- sterilisation
- spermicidal creams
- intrauterine devices (within uterus)
increase fertility
FSH + LH
stimulate eggs to mature
IVF:
- women get FSH +LH to stimulate growth of eggs
- collect the eggs
- fertilise eggs with sperm in laboratory
- insert embryos into woman’s uterus
