responding to change

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Cells called receptors detect stimuli (changes in the environment). State some receptors and the stimuli they detect. ■ receptors in eyes - sensitive to light ■ receptors the ears - sensitive to sound and sensitive to changes in position ■ receptors on the tongue and in the nose - sensitive to chemicals ■ receptors in the skin - sensitive to touch,pressure, pain and temperature
Draw a labelled diagram of a light receptor cell 34003150-6a3a-48ab-b972-600c9602dbcf.PNG (image/PNG)
Describe a simple reflex action ■ impulses from a receptor pass along a sensory neurone to the CNS ■ chemicals released at synapse between sensory and relay neuron diffuse across gap ■ chemicals released at the synapse between a relay neurone and motor neurone , impulse goes to effector that brings about the response
what is an effector ? the effector is either a muscle or a gland, a muscle responds by contracting and a gland responds by releasing (secreting) chemical substances.
how is the amount of water in the body controlled? water leaves the body via the lungs when we breathe out and via the skin when we sweat to cool us down, and excess water is lost via the kidneys in the urine
How is ion content controlled ? Ions are lost via the skin when we sweat and excess ions are lost via the kidneys in the urine
Why is it important to control body temperature and how is it done? to maintain the temperature at which enzymes work best by: - sweating - shivering
Why must blood sugar be controlled and is it done to provide the cells with a constant supply of energy. - insulin
What are hormones and how are they transported around the body Hormones are chemical messengers secreted by glands and are usually transported to their target organs by the bloodstream.
Describe the function of the 3 main hormones in the menstrual cycle ■ (FSH) is secreted by the pituitary gland and causes eggs to mature in the ovaries and stimulates the ovaries to produce oestrogen ■ (LH) stimulates the release of eggs ■ oestrogen is secreted by the ovaries and inhibits the further production of FSH.
Describe how oral contraceptives can prevent pregnancy oral contraceptives that contain hormones such as oestrogen and progesterone inhibit FSH production so that no eggs mature
Describe the problems with early birth control pills and how they have been improved – the first birth-control pills contained large amounts of oestrogen. These resulted in significant side effects – birth-control pills now contain a much lower dose of oestrogen, or are progesterone only – progesterone-only pills lead to fewer side effects
describe how IVF works a mother is given FSH and LH to stimulate the maturation and release of several eggs. The eggs are collected from the mother and fertilised by sperm from the father. The fertilised eggs develop into embryos. One or two embryos are inserted into the mother’s uterus (womb).
How do hormones control phototropism and gravitropism Plants produce hormones coordinate and control growth. Auxin controls phototropism and gravitropism The responses of plant roots and shoots to light, gravity and moisture are the result of unequal distribution of hormones, causing unequal growth rates.
Why do roots grow down ? (gravitropism) Caused by unequal distribution of auxin 1.in the root more auxin acculturates on the lower side due to gravity 2. the root grows more on the side with least auxin, (inhibits growth of cells on lower side of root) making it bend and grow towards the force of gravity 3. when it has grown down the auxin becomes evenly spread again
why do shoots grow up ? Caused by unequal distribution of auxin 1.in the shoot more auxin acculturates on the lower side due to gravity 2. the shoot grows more on the side with most auxin making it bend and grow up away from the force of gravity 3. when it has grown up the auxin becomes evenly spread again
Explain why shoots grow towards the light ? Caused by unequal distribution of auxin 1. more auxin accumulates on the shaded side of the shoot 2. auxin causes shaded side to grows faster 3. therefore shoot bends towards the light
give 3 uses of plant hormones by farmers 1. weed killers (hormones) are used to kill unwanted plants (broad leaved ) 2. when cuttings are taken from plants hormones are used to encourage roots to grow before the cutting is planted 3. some hormones are used to encourage fruit to ripen
name 3 stimuli which affect humans light , sound , chemicals, touch , pain, temperature changes
what is a reflex and why are they important a rapid automatic response to a stimuli they protect us from damage
what are the differences in action between nerves and hormones nervous actions are - 1. quicker 2. affect last a shorter period 3. nervous action affects specific target 4. hormones travel in blood , nervous impulse involves neurones
describe issues with IVF pros: helps couples have babies cons 1. IVF is expensive 2. some people think it is unethical when older woman have babies by IVF 3. extra embryos may be destroyed
describe the issues with the contraceptive pill pros 1.have helped reduce family size which 2.can reduce poverty allows woman to plant their pregnancies cons 1.the contraceptive pill can cause side effects 2. some people object to its use for ethical or religious reasons
How long is the menstrual cycle and when approximately does ovulation occur takes 28 days , with ovulation about 14 days into the cycle
draw a picture of the reflex arc edab46d6-e471-4add-8fac-6049c85b6177.jpg (image/jpg)
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