Parts of nervous system
- The nervous system consist of the brain, spinal cord, spinal nerves and receptors.
- Its allows organisms to react to their surroundings and to coordinate their behavior.
Types of neurones
- Motor neurone: Impulse travels away from cell body.
- Sensory neurone: Impulse travels towards cell body.
- Relay neurone: Impulse travels firts towards and then away from cell body.
Neurons are elongated to make connections between parts of the body.
Connections between neurons
Neurons do not touch each other; there is a gap between them called a synapse.
Types of receptor
Receptors detect stimuli.
- Light- receptors in the eyes.
- Sound- receptors in the ears.
- Change in position- receptors in the ears.
- Taste- receptor in the tonge.
- Smell- receptors in the nose.
- Touch, pressure, pain and temperature- receptors in the skin.
- Reflex action speeds up theresponse time by missing out the brain completly.
- The spinal cord acts as the coordinator and passes impulses directly from a sensory neurone to a motor neurone via a relay neurone.
- Reflex actions are automatic and quick.
Humans need to keep their internal environment relatively constant.
- Temperature: Increased by shivering and narrowing skin capillaries; Decreased by sweating and expanding skin capillaries.
- Water content: Gained by drinking; Lost by breathing via the lungs and sweating; Any excess is lost via the kidneys in urine.
- Ion content: Gained by eating and drinking; Lost by eating and drinking; Lost via sweating; Excess is lostvia the kidneys in urine.
- Blood sugar (glucose) levels: Glucose provides the cells with a constant supply of energy; Gained by eating and drinking.
How conditions are controlled?
- Many processes within the body are coordinated by hormones.
- Hormones are chemical substances.
- Hormones are produced by glands.
- Hormones are transported by the bloodstream.
Hormones and fertility
- Hormones regulate the functions of many organs and cells.
- A woman naturally produces hormones that cause the release of an egg from her ovaries.
- These hormones are produces by the pituitary gland and the ovaries.
Natural control of fertility
- Follicle stimulating hormone (FSH): Produced in the pituitary gland; Causes the ovaries to produce oestrogen and an egg to mature.
- Oestrogen: Produces in the ovaries; Inhibits the production of FSH and causes the production of luteinising hormone (LH).
- LH: From th epituitary gland; Stimulates the release of an egg in the middel of the menstrual cycle.
Artificial control of fertility
FSH and oestrogen can be given to women in order to achieve opposing results.
- Increasing fertility: FSH is given as a fertility drug to women who don't produce enought naturally, to stimulate eggs.
- Reducing fertility: Oestrogen is given as an oral contraceptive to inhibit FSH production. This means that eggs don't mature in the ovary.