Biology Unit 1a & 1b




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  • Created on: 07-06-12 14:21
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Biology 1a ­ Human Biology
The Nervous System
A stimulus is a change in your environment which you may need to react to.
Eyes ­ light receptors
Ears ­ sound and `balance' receptors
Nose ­ smell receptors
Tongue ­ taste receptors
Skin ­ sensitive to touch, pressure and temperature change
Sensory neurones ­ nerve cells that carry signals as electrical impulses from the
receptors in the sense organs to the central nervous system.
Motor neurones ­ nerve cells that carry signals to the effector muscles or glands.
Effectors ­ muscles and glands (they respond in different ways) : muscles = contracts,
whereas, glands = secrete hormones
Central nervous system (CNS) ­ where all the information from the sense organs is sent,
and where reflexes and actions are coordinated. It consists of the brain and spinal cord
Neurones ­ transmit the information very quickly to and from the CNS.
`Instruction' from the CNS is sent to the effectors which respond accordingly.
Reflexes are automatic responses to certain stimuli ­ can reduce the chances of being
Neurones in reflex arcs go through the spinal cord or through the unconscious part of the
E.g. of a bee stinging a finger
o Cheeky bee stings finger
o Stimulation of the pain receptor
o Message travels along the sensory neurone
o Message is passed along a relay neurone
o Message travels along a motor neurone
o When the message reaches the muscle, it contracts
Connection between 2 neurones is called a synapse
Nerve signal is transferred by chemicals which diffuse across the gap
These chemicals then set off a new electrical signal in the next neurone
Hormones are chemicals released directly into the blood.
Carried in the blood plasma to other parts of the body, but only affect particular cells
called target cells
Produced in various glands:
o Pituitary gland ­ produces many important hormones including LH, FSH and ADH
o Pancreas ­ produces insulin for the control of blood sugar
o Ovaries ­ produces oestrogen, which controls the menstrual cycle & promotes all
female secondary sexual characteristics during puberty
o Testes ­ produces testosterone, which promotes all male secondary sexual
characteristics at puberty
o very fast message

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o Slower message
o Act for a long time
o Act in a more general way
The Menstrual Cycle
o Produced by the pituitary gland
o Causes an egg to mature
o Stimulates the ovaries to produce oestrogen
o Produced in the ovaries
o Causes pituitary gland to produce LH
o Stops further release of FSH
o Produced in the pituitary gland
o Stimulated the release of egg
Controlling Fertility
Oestrogen can be used to prevent the release of an egg…read more

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Hot day or exercising ­ sweat a lot, so produce less urine which will be
more concentrated. Also lose more water through breath.
o Sugar content ­ foods containing carbohydrate puts glucose into the blood from
o Temperature ­ enzymes within the human body work best at about 37°C
Diet & Exercise
To balance, you need:
1. Carbohydrates & fats ­ to keep warm & provide energy
2. Protein ­ for growth, cell repair & cell replacement
3.…read more

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Thalidomide ­ was a sleeping pill (tested for that), but later was found to be effective in
relieving morning sickness in pregnant women (unfortunately wasn't tested for this) ­
caused stunted growth of foetus's arm & legs. Now used to treat leprosy, AIDS & certain
Alcohol & Tobacco
o Contains carbon monoxide ­ combines irreversibly with haemoglobin in the blood
cells, which means the blood can carry less oxygen.…read more

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Looked at whether cannabis causes brain damage & mental health problems
or leads to further drug taking.
Results are open to different interpretations
Fighting Disease
2 main types of pathogen
o Bacteria:
Very small living cells, which can reproduce rapidly inside your body.
Make you feel ill by:
Damaging your cells
Producing toxins (poisons)
Useful if they are in your digestive system.…read more

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If antibiotics deal with an infection & some of the bacteria are killed, those which survive
may be resistant to the antibiotics & go on to flourish. ­ Which leaves you with an
antibioticresistant strain of bacteria.
E.g. MRSA (methicillinresistant Staphylococcus Aureus) ­ it's resistant to the antibiotic
methicillin.…read more

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Competition ­ organisms compete with other species for the same resources. ­
can affect the location, size & distribution of populations in the wild.
a) Plants compete with each other for light, water & nutrients from the soil
b) Animals ­ compete with each other for space, food, water & mates.
2. Disease ­ infectious diseases caused by bacteria & viruses can kill off many
members of a population ­ but organisms which are the best & fit = survive.
3.…read more

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Egg & sperm fuses together to form a cell with the full number of chromosomes.
Plants can be cloned by 1 of the following:
o Cutting ­ gardeners can take cuttings from good plants & plant them to produce
identical copies of the parent plant. ­ can be produced quickly & cheaply.
o Tissue culture ­ where a few plant cells are put in a growth medium with hormones,
& they then grow into new plants ­ clones of the parent plant.…read more

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Theory of evolution = life on Earth began as simple organisms from which all the more
complex organisms evolved.
Species become extinct for 3 main reasons:
1. Environment changes too quickly ­ e.g. destruction of habitat
2. A new predator or disease kills them all ­ e.g. humans hunting them
3. They can't compete with another new species for food.
Mutations = DNA of an organism changes
o Happens within a gene & it's passed on to the next generation it can cause new
characteristics.…read more

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Several different gases in the atmosphere which help keep the heat in, called greenhouse
gases. Main ones are:
o Carbon dioxide ­ humans release this all the time as part of our everyday lives ­
car exhausts, industrial processes, as we burn fossil fuels, deforestation etc.…read more


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