B1.2 GCSE
- Created by: maddiebayliss
- Created on: 15-05-16 19:21
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- B1.2
- Responding to change
- The nervous system has receptors to detect stimuli.
- The receptors are found in sense organs, the eye, nose, mouth, ear and skin.
- The brain and spinal cord form the central nervous system (CNS)
- Nerves contain neurons. Sensory neurons carry impulses from receptors to the CNS.
- Motor neurons carry impulses from the CNS to effector organs which may be muscles or glands.
- The muscles respond by contracting.
- The glands respond by secreting chemicals.
- The muscles respond by contracting.
- The nervous system has receptors to detect stimuli.
- Reflex actions
- 1) A receptor detects a stimulus.
- 2) A sensory neuron transmits the impulse to the CNS.
- 3) A relay neuron passes the impulse on.
- 4) A motor neuron is stimulated.
- 5) The impulse passes to an effector (muscle or gland).
- 6) Action is taken (the response).
- Controlling Conditions
- The body carefully controls its internal environment.
- Water content
- Ion content
- Temperature
- Blood sugar level
- The body carefully controls its internal environment.
- Hormones and Menstrual Cycle
- FSH is made by the pituitary gland and causes the egg to mature and oestrogen to be produced.
- Oestrogen is produced by the ovaries and inhibits the further production of FSH.
- It stimulates the production of LH and also stimulates the womb lining to develop to receive the fertilised egg.
- LH is made by the pituitary gland and stimulates the mature egg to be released from the ovary.
- Artificial control of fertility
- The contraception pill may contain oestrogen and progesterone.
- The pill prevents the production of FSH so no eggs mature.
- Advantages
- Contraceptive pills have helped to reduce family size which helps reduce poverty.
- It allows women to plan their pregnancy.
- Fertility drugs can help couples who are having IVF
- Disadvantage
- Side effects
- Ethical or religious reasons
- Older women having babies
- Extra embryos being destroyed or stored
- IVF is an expensive process.
- The contraception pill may contain oestrogen and progesterone.
- Control of Plant Growth
- Plant shoots grow towards light. This response is phototropism.
- Roots grow down towards gravity. This response is gravitropism.
- Roots also grow towards water.
- Auxin is the hormone that controls phototropism and gravitropism
- Responding to change
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