AQA BIOLOGY - PAPER 2 EXAM | VERIFIED ANSWERS 100% |2025
what is homeostatsis - ✔✔the maintenance of a constant internal environment at
optimal conditions in the body
what are the 3 parts of ay homeostatic mechanism - ✔✔receptors, coordination centres,
effector
what is a receptor - ✔✔cells which detect stimuli/change in the environment
what is an effector - ✔✔a muscle/gland that will bring about a response
what do internal conditions of the body include - ✔✔body temperature
the water content of the body
blood glucose concentration
what are neurons found between the receptor and coordination centre called -
✔✔sensory neurons (eyes, ears, skin)
what are neurons found between the effector and coordination centre called - ✔✔motor
neurons (brain/spinal cord)
reflex arc - ✔✔stimulus -> receptors -> relay neuron (in vertebrae) -> motor neuron ->
gland(hormone)/muscle(contraction)
nervous reflexes - ✔✔blinking, breathing, sneezing
how do synapses (gap between neurones) work - ✔✔nerve impulse travels to the ed on
one neurone
chemical transmitter molecules diffuse across the gap (synapse)
once they reach the receptors another electrical impulse will be generated
required practical for reaction time (catching ruler) variables - ✔✔Dependant variable:
distance the ruler falls before being caught / reaction time
Independent variable: age
affect of caffeine
affect of a distraction
Control variables:
drop height
mass/type of rule
arm/finger position
, use of dominant hand
time following caffeine intake
other ways to test reaction time - ✔✔computer simulated reaction time test
what is a negative feedback loop - ✔✔a homeostatic mechanism that occurs when the
body detects a change and makes an adjustment to return itself to normal
what happens if thyroxine levels increase - ✔✔brain send s signals and pituitary gland
releasees less thyroxine stimulating hormone (TSH) and less thyroxine is released from
the thyroid
what does less thyroxine mean - ✔✔lower metabolism
lower levels of protein synthesis
(and vice verse)
why is a adrenalin released - ✔✔stress/scary situation
effect of adrenalin on the body - ✔✔pupils dilate (let more light in to take in more visual
information)
heart rate increases ( to pump blood faster to deliver more oxygen to cells)
breathing rate increases (more 02 to the blood)
glycogen reserves in muscle cells break down (to release glucose for increased
respiration)
blood from digestive systems redirected to skeletal muscles
"fight or flight"
negative feedback loop for thyroxine level - ✔✔1.receptors in the brain detect an
increase
2.less TSH released from the pituitary gland
3.receptors in the brain detect a decrease
4.more TSH released from the pituitary gland
graph for adrenaline production - ✔✔1. adrenal glands release adrenalin
(scary/stressful event)
2.fight/flight response
3.adrenalin levels fall
why are negative feedback loops need - ✔✔to maintain a normal level
features of hormones - ✔✔originate in glands, travel in blood, long lasting, slow action,
chemical signal
features of the nervous system - ✔✔originate at the receptor, travel in neurons, short
lasting, rapid action, electrical signals
what is homeostatsis - ✔✔the maintenance of a constant internal environment at
optimal conditions in the body
what are the 3 parts of ay homeostatic mechanism - ✔✔receptors, coordination centres,
effector
what is a receptor - ✔✔cells which detect stimuli/change in the environment
what is an effector - ✔✔a muscle/gland that will bring about a response
what do internal conditions of the body include - ✔✔body temperature
the water content of the body
blood glucose concentration
what are neurons found between the receptor and coordination centre called -
✔✔sensory neurons (eyes, ears, skin)
what are neurons found between the effector and coordination centre called - ✔✔motor
neurons (brain/spinal cord)
reflex arc - ✔✔stimulus -> receptors -> relay neuron (in vertebrae) -> motor neuron ->
gland(hormone)/muscle(contraction)
nervous reflexes - ✔✔blinking, breathing, sneezing
how do synapses (gap between neurones) work - ✔✔nerve impulse travels to the ed on
one neurone
chemical transmitter molecules diffuse across the gap (synapse)
once they reach the receptors another electrical impulse will be generated
required practical for reaction time (catching ruler) variables - ✔✔Dependant variable:
distance the ruler falls before being caught / reaction time
Independent variable: age
affect of caffeine
affect of a distraction
Control variables:
drop height
mass/type of rule
arm/finger position
, use of dominant hand
time following caffeine intake
other ways to test reaction time - ✔✔computer simulated reaction time test
what is a negative feedback loop - ✔✔a homeostatic mechanism that occurs when the
body detects a change and makes an adjustment to return itself to normal
what happens if thyroxine levels increase - ✔✔brain send s signals and pituitary gland
releasees less thyroxine stimulating hormone (TSH) and less thyroxine is released from
the thyroid
what does less thyroxine mean - ✔✔lower metabolism
lower levels of protein synthesis
(and vice verse)
why is a adrenalin released - ✔✔stress/scary situation
effect of adrenalin on the body - ✔✔pupils dilate (let more light in to take in more visual
information)
heart rate increases ( to pump blood faster to deliver more oxygen to cells)
breathing rate increases (more 02 to the blood)
glycogen reserves in muscle cells break down (to release glucose for increased
respiration)
blood from digestive systems redirected to skeletal muscles
"fight or flight"
negative feedback loop for thyroxine level - ✔✔1.receptors in the brain detect an
increase
2.less TSH released from the pituitary gland
3.receptors in the brain detect a decrease
4.more TSH released from the pituitary gland
graph for adrenaline production - ✔✔1. adrenal glands release adrenalin
(scary/stressful event)
2.fight/flight response
3.adrenalin levels fall
why are negative feedback loops need - ✔✔to maintain a normal level
features of hormones - ✔✔originate in glands, travel in blood, long lasting, slow action,
chemical signal
features of the nervous system - ✔✔originate at the receptor, travel in neurons, short
lasting, rapid action, electrical signals
