Responding to changes and controlling conditions
- Hormones are secreted by glands, they are chemicals which help control and co-ordinate processes in your body.
- The nervous system uses eletrical impulses to enable you to react to your surroundings and co-ordinate your movements.
- Receptor cells detect stimuli(changes in the enviroment).
- Impulses from receptors pass along sensory neurons to the CNS.
- Impulses are sent from the CNS to the effector organs along motor neurones.
- The CNS/Central Nervous System is the brain and the spinal cord.
- Humans need to maintain a constant internal enviroment, controlling levels of water, ions, blood sugar and temprature.
- Homeostasis is the result of the co-ordination of your nervous system, your hormones and your body organs.
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Reflex Reactions and Synapses
- Reflexes are when a reaction happens without you having time to think about it.
- Such as if you touch something hot and you move your hand away quickly so you don't get burnt.
- Reflex reactions involve 3 types of neutrons: sensory, motor and relay.
- The electrical impulse travels from the sensory receptor along the sensory neurone to the nearest CNS, it then goes along the relay neurone and then back on the motor neurone to the effector.
- The effector is either a gland or a muscle.
- They are the gaps in between the neurones.
- The electrical impulses cannot pass over them.
- Chemicals are released from one neurone which cross the synapse and arrive at receptor sites on the next neurone.
- This starts the next electrical impulse.
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The Menstral Cycle and Artifical fertilaty
- Hormones control the release of an egg from the ovary and the build up of the liningof the womb in the menstrual cycle.
- The main hormones involved are FSH and LH from the pituitary gland and oestrogen both from the ovary.
- Hormones can be used to control fertility.
- Oral contreceptives contain hormones which stop FSH from production so no eggs mature.
- FSH can be used as a fertilaty drug for women, to stimulate her eggs to mature in their ovaries.
- These eggs may be used in IVF treatment.
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