Chapter 2

Chapter 2

Your nervous system carries fast electrical impulses. Changes in the environment are picked up by your receptors and impulses travel along your CNS to your neurons.

In a reflex arc the electrical impulse bypasses the conscious areas of your brain. The time between the stimulus and the response is as short as possible. Only sensory neurons, relay neurons and motor neurons are involved.

During the menstrual cycle, a mature egg is released from the ovary about every 28 days. The cycle is controlled by several hormones including oestrogen and FSH.

FSH:-causes egg to mature-stimulates ovary to produce oestrogenOestrogen:-causes lining of womb to develop-inhibits FSH production-stimulates release of egg.

Oral contraception: contraceptive pills, widely used in controlling fertility.Fallopian tube: the tube in which eggs travel from the ovary to the uterus.Fertility drug:  they increase the levels of FSH and oestrogen in a women, which mature and release one or more eggs each month. IVF: where eggs are removed from the ovaries and fertilised with sperm in the laboratory. The fertilised egg (embryo) is later placed in the woman's womb.

Conditions in the internal environment of your body must be kept constant. This is called homeostasis. The control is given by both your hormones and your nervous system.

Plants are sensitive to light, which is called phototropism. They respond to gravity which is gravitropism. Plants are also sensitive to moisture. These responses are coordinated by the plant hormone called auxin. 

Allowing an older woman to use hormones such as FSH to help her have a baby:

Pros: -giving the opportunity to people who really want children, but haven't had the circumstances available to do so sooner-if can be just as successful with older women as in young ones, they have to use artificial hormones to get he womb ready and use donor eggs, but once the women are pregnant, their hormones take over-some women can have babies naturally in their 50s 

Cons: -interfering with nature-mother might die before child becomes an adult

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