Biology B1.2.1 and B1.2.2 The Nervous System and Control in the Body

A brief overview of all the information you need, taken directly from the specification.

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Receptors and stimuli

  • Eyes - colour, light, shape, motion etc.
  • Ears - Pitch, vibration, amplitude, sound, pressure (balance)
  • Nose - Smell
  • Skin - Pain, temperature, pressure, texture
  • Tongue - taste
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Reflex arc

The stimulus is detected by the receptor, which sends an impulse down the sensory neurone. the impulse passes across the synapse to the inter neurone, then down this across the next synapse. The impulse travels along the motor neurone to the effector, a muscle or a gland, which stimulates the response.

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The impulse hits the synaptic vesicles, and changes into a chemical called a neurotransmitter. This diffuses across the gap and the receptors of the next neurone change it back into an electrical impulse.

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Controlling internal conditions

Temperature - Maintain at 37C so enzymes work properly. Cool down by sweating and warm up by shivering.

Blood Sugar - Controlled by pancreas. Cells provided with constant supply of energy.

Ion Content - Lost when sweating and in urine.

Water Content - Lost in exhalation, sweating and from kidneys.

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The menstrual cycle

Follicle Stimulating Hormone (FSH) - Produced in pituitary gland. Causes ovaries to mature eggs and starts production of oestrogen.

Oestrogen - Produced in ovaries. Causes ovaries to prepare for release of eggs, thickens uterus lining, stops production of FSH and starts production of LH

Luteinising Hormone (LH) - Produced in pituitary gland. Causes ovaries to release eggs and stops production of oestrogen.

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Oral Contraceptives

Contain hormones such as oestrogen and progesterone to prevent eggs maturing. Only small amounts of oestrogen are used, and sometimes none, to prevent side effects.

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In Vitro Fertilisation

FSH is injected into the woman, to make her produce lots of eggs. These are then harvested and fertilised in a lab by washed sperm. When the eggs develop into embryos, they are placed in the woman's uterus. If the IVF is successful, the woman continues to inject fertility drugs to support the pregnancy.

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