Term
| Nerves and Hormones - The Nervous System |
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Definition
The human central nervous system (CNS) consists of the brain and spinal cord.
When a receptor is stimulated it sends a signal along the nerve cells, also called neurones, to the brain. The brain then coordinates the response except in the case of reflex actions which bypass the brain for speed. |
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Term
Nerves and Hormones - The Nervous System
Receptors |
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Definition
Receptors are specialised cells that detect changes in the environment (stimuli)
Found: - Sensitive to:
Eyes - light
Ears - sound and position of the head
Tongue - chemicals in food
Nose - chemicals in the air
Skin - touch, pressure, pain and temperature |
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Term
Nerves and Hormones - The Nervous System
Neurons |
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Definition
Sensory neurones - from receptors to the spinal cord and brain
Relay neurones - from one part of the CNS to another
Motor neurones - from the CNS to effectors. |
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Term
Nerves and Hormones - The Nervous System
Neurons |
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Definition
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Term
Nerves and Hormones - The Nervous System
Synapses |
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Definition
| When two neurones meet there is a gap called a synapse. Signals cross this gap using chemicals. One neurone releases the chemical into the gap; the chemical diffuses across the gap and makes the next neurone transmit an electrical signal. |
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Term
Nerves and Hormones - The Nervous System
Reflex Actions |
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Definition
stimulus→receptor→sensory neurone→relay neurone→motor neurone→effector
Receptor detects stimulus
Sensory neurone sends impulses to relay neurone, through to motor neurone
Motor neurone sends impulses to effector which produces a response. |
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Term
Nerves and Hormones - The Nervous System
Reflex Actions |
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Definition
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Term
Nerves and Hormones - Control in the Human Body
Homeostasis |
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Definition
| The internal environment of the body is controlled by the nervous system and hormones. The maintenance of a constant internal environment is called homeostasis. |
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Term
Nerves and Hormones - Control in the Human Body
Water Loss |
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Definition
Hypothalamus detects too little water in the blood
Pituitary gland releases ADH
Kidneys detect ADH; making urine more concentrated
Blood water level returns to normal |
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Term
Nerves and Hormones - Control in the Human Body
Other Maintained levels: |
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Definition
Ion (salts) content of the body, regulated by skin (sweating) and urine
Body temperature to maintain body at temperature enzymes work best at
regulated by sweating, shivering and blood flow to the skin (vasodilation)
Blood sugar levels
controlled by storage and release of glucose controlled by insulin |
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Term
Nerves and Hormones - Control in the Human Body
Hormones |
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Definition
Hormones regulate the functions of many cells and organs and transported around the body in the bloodstream.
Thyroid gland produces thyroxine (metabolic rate)
Adrenal glands produce adrenaline (prepares body for rapid activity)
Pancreas produces insulin (blood sugar)
Testes produce testosterone (puberty and sperm production)
Ovaries produce oestrogen (puberty and partial control of the menstrual cycle) |
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Term
Nerves and Hormones - Control in the Human Body
Menstrual Cycle |
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Definition
FSH (follicle stimulating hormone) secreted by the pituitary gland. Makes:
An egg mature in an ovary
Stimulates ovaries to release oestrogen, which :
Stops FSH being produced so only one egg matures in a cycle
Stimulates pituitary gland to release luteinizing hormone (LH) which triggers ovulation (the release of the egg) |
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Term
Nerves and Hormones - Control in the Human Body
Menstrual Cycle |
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Definition
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Term
Nerves and Hormones - Control in the Human Body
Oral Contraceptives |
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Definition
| The pill reduces chances of mature eggs being produced. It contains oestrogen or progesterone. These inhibit the production of FSH(which causes eggs to mature). |
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Term
Nerves and Hormones - Control in the Human Body
Fertility Drugs |
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Definition
| Difficulty with conception can occur because shortage of FSH doesn't allow eggs to mature. Fertility drugs contain FSH and LH, causing more eggs to mature often leading to multiple eggs being fertilised resulting in twins or triplets which can cause complications in birth |
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Term
Nerves and Hormones - Control in the Human Body
In Vitro Fertilisation (IVF) |
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Definition
| The egg is fertilised outside the woman’s body and then implanted back into her uterus. FSH is used as part of IVF to increase the number of mature eggs available for fertilisation. |
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Term
Nerves and Hormones - Control in Plants
Tropisms |
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Definition
A tropism is a growth in response to a stimulus
Positive tropism – the plant grows towards the stimulus
Negative tropism – the plant grows away from the stimulus
The roots and shoots of a plant respond differently to the same stimuli. |
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Term
Nerves and Hormones - Control in Plants
Auxins |
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Definition
Produced in the plant tip and roots.
Control direction of growth by changing the rate of elongation in cells: if the cells on one side of the plant grow longer the plant bends the opposite way
Cells in shoots grow more when the concentration of auxins are high
Cells in roots grow less when the concentration of auxins are high |
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Term
Nerves and Hormones - Control in Plants
How auxins facilitate tropisms |
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Definition
| Auxin in greater concentration on shaded side (breaks down in light), causing cells to grow longer than cells on lit side. |
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Term
Nerves and Hormones - Control in Plants
Geotropisms |
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Definition
In a root placed horizontally, bottom side contains more auxin. Bottom side grows less, causing root to bend downwards.
In a shoot placed horizontally, bottom side contains more auxin. Bottom side grows more than top side, causing shoot to bend and grow upwards |
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Term
Nerves and Hormones - Control in Plants
Using plant hormones |
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Definition
Selective weed killers contain growth hormone that cause the weeds to grow too quickly and then die. The weed killer is absorbed in larger quantities by the weeds than beneficial plants which remain healthy.
Rooting powder contains growth hormones to make stem cuttings quickly develop roots |
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