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Topic 11.1 ­ How do humans' bodies respond to
changes inside them and to their environment?
­ Describe how a nervous response is brought about by stimuli, including the roles of receptors,
sensory neurones, the coordinator and motor neurones.
· Stimulus (Light bulb) -> Receptor (Eye) -> impulse travels along the sensory neurone to ->
Coordinator (Brain) -> impulse travels along the motor neurone to -> Effector (Eye muscle) ->
Response
­ Neurone = A single nerve
­ Describe a reflex action and the role of the relay neurone in this action.
· Receptor (Finger) -> impulse travels along sensory neurone -> comes to synapse -> goes onto
the relay neurone -> to synapse -> along the motor neurone -> Effector (Arm muscle)
­ Synapse = gaps between the end of a neurone and the start of another or an effector.
­ Axon = the end of a neurone.…read more

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Topic 11.1 ­ How do humans' bodies respond to
changes inside them and to their environment?
Explain that four internal conditions controlled by the body include; water content, ion content, body
temperature and blood sugar. Describe, in very broad outline, how they are controlled.
· Ion content leaves body 1) in sweat 2) excess lost via kidneys in urine.
· The water content of body leaves body 1) in breath 2) as sweat 3) excess is lost via kidneys in urine.
· Temperature -> maintain temperature at which enzymes work best.
· Blood sugar levels -> to provide the cells with a constant supply of energy.
Describe hormones as chemicals which coordinate reactions in the body and that are secreted by glands and
reach their target organs via the blood stream.
· Pituitary glands -> FSH and LH.
· Ovaries -> oestrogen and progesterone.
· FSH (Follicle stimulating hormone) ­ egg mature + oestrogen to be released.
· Oestrogen ­ thickens uterus lining + inhibits FSH
· LH (Luteinizing hormone) ­ egg is released from ovary + stimulates progesterone.…read more

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Topic 11.1 ­ How do humans' bodies respond to
changes inside them and to their environment?
-Describe how hormones control both the monthly release of an egg and the varying
thickness of the lining.
FSH
The hormone FSH is secreted by the
pituitary gland. FSH makes two things
happen:
it causes an egg to mature in an ovary,
it stimulates the ovaries to release the
hormone oestrogen
Oestrogen
The hormone oestrogen is secreted by
the ovaries. Oestrogen makes two things
happen:
it stops FSH being produced - so that only
one egg matures in a cycle, it stimulates
the pituitary gland to release the hormone LH
LH
The hormone LH causes the mature egg to
be released from the ovary. This image shows
how the level of oestrogen changes during
the menstrual cycle. Progesterone is another
hormone secreted by ovaries: it maintains
the lining of the uterus and stays high during
pregnancy.…read more

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