Biology B1.2

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What are receptors?
Receptors are groups of specialised cells that can detect changes in the environment called stimuli. Receptors are often located in the sense organs.
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What are the sense organs?
Eyes, ears, tongue, nose and skin.
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What is the CNS?
The CNS is the human central nervous system and it consists of the brain and spinal cord.
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What happens when a receptor is stimulated?
When a receptor is stimulated it sends a signal along the nerve cells, also called neurones, to the brain. The brain then coordinates the response.
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What are neurons?
Neurones are nerve cells that carry information as tiny electrical signals. There are three different types of neurones, each with a slightly different function.
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What are the three different types of neuron and their purposes?
Sensory neurones carry signals from receptors to the spinal cord and brain.Rrelay neurones carry messages from one part of the CNS to another. Motor neurones carry signals from the CNS to effectors.
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What are synapses and what happens at them?
Where two neurones meet there is a tiny gap called a synapse. Signals cross this gap using chemicals. One neurone releases the chemical into the gap. The chemical diffuses across the gap and makes the next neurone transmit an electrical signal.
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What are reflexes?
When a receptor is stimulated it sends a signal to the central nervous system, where the brain coordinates the response, but sometimes a very quick response is needed, one that does not involve the brain.
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What is the reflex arc?
A reflex arc is the nerve pathway which makes such a fast, automatic response possible. It does not matter how brainy you are - you will always pull your hand away from a flame without thinking about it.
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What is the sequence in a simple reflex action?
stimulus → receptor → sensory neurone → relay neurone → motor neurone → effector
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What is an effector?
An effector is any part of the body that produces the response. (e.g. a muscle contracting or a gland secreting a hormone or other chemicals)
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What happens at each stage of the reflex arc?
Receptor detects a stimulus - a change in the environment. Sensory neurone sends impulses to relay neurone. Motor neurone sends impulses to effector. Effector produces a response.
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What are hormones?
Hormones are chemical substances that regulate processes in the body, they are secreted by glands in the body. Different hormones affect different target organs.
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How are hormones transported?
Through the blood.
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What is the menstrual cycle?
The menstrual cycle in women is a recurring monthly process in which the lining of the uterus (the womb) is prepared for pregnancy. If pregnancy does not happen, the lining is shed at menstruation.
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What do hormones control in relation to the menstrual cycle?
Several hormones control this cycle, which includes controlling the release of an egg each month from an ovary, and changing the thickness of the uterus lining. These hormones are secreted by the ovaries and pituitary gland.
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What does the follicle stimulating hormone, FSH, do?
The hormone FSH is secreted by the pituitary gland. FSH makes two things happen: it causes an egg to mature in an ovary and it stimulates the ovaries to release the hormone oestrogen.
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What does oestrogen do?
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 and it stimulates the pituitary gland to release LH, which triggers ovulation.
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What does the contraceptive pill do?
greatly reduces the chances of mature eggs being produced. It contains oestrogen or progesterone (another hormone). These hormones inhibit the production of FSH, which in turn stops eggs maturing in the ovaries.
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What do fertility treatments do?
Fertility treatments increase a woman's chance of becoming pregnant, although the treatment may not always work. On the other hand, because the treatment boosts the production of mature eggs, multiple conceptions sometimes occur.
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What hormones do fertility drugs contain?
Fertility drugs contain FSH and LH, which stimulate eggs to mature in the ovary.
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What is in vitro fertilisation?
If a couple are having difficulty conceiving a child because the quantity or quality of the man’s sperm is poor then IVF can be used. This is where the egg is fertilised outside the woman’s body and then implanted back into her uterus.
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Card 2


What are the sense organs?


Eyes, ears, tongue, nose and skin.

Card 3


What is the CNS?


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Card 4


What happens when a receptor is stimulated?


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Card 5


What are neurons?


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