B1

High Blood pressure can lead to blood vessels bursting as well as strokes, brain damage and kidney damage.

Low blood pressure can lead to feeling dizzy and fainting.

The carbon monoxide from cigarettes combines with the hemoglobin in the red blood cells, which reduces the amount of oxygen they can carry.

Narrowed coronary arteries will make blood flow to the heart restricted and the heart muscles receive less oxygen. A thrombosis (blood clot) also restricts blood flow. If this happens an area of heart muscle will be cut off from oxygen completely, which can cause a heart attack.

Carbohydrates are made up of simple sugars.

They are stored in the liver as glycogen or converted to fats.

Fats are made up of fatty acids and glycerol. They can be stored under the skin and around organs as adipose tissue.

Proteins are made up of amino acids. They don’t get stored.

First Class proteins are ones that have all the essential amino acids you can get these by eating animals, animal proteins are called first class proteins.

Second class proteins are proteins that don’t contain all the essential amino acid such as plant proteins.

EAR for protein may vary from person to person because everyone is different and some people need more some people need less of things compared to others. Teenagers need to eat more proteins than adults because they are still growing.

A parasite is an organism that lives off another organism.

Mosquitoes are vectors, meaning they carry the disease without getting it themselves.

We know that mosquitoes carry malaria so we can target them to reduce the spread of the infection:

-       The area of water where mosquitoes lay their eggs can be drained or sprayed with insecticides.

-       Fish can be introduced into the water to eat mosquito larvae.

-       People can be protected from mosquitoes by using insecticides and mosquito nets.

Benign Tumours are when the tumour grows until there’s no more room. The cells stay where they are. This type isn’t normally dangerous.

Malignant Tumours are when the tumour grows and can spread to other sites in the body. Malignant tumours are dangerous and can be fatal.

Antibodies are produced specific to that pathogen- they won’t lock onto other pathogen’s. Every pathogen has unique molecules on the surface of its cells- therefore only a specific antibody can work for a specific pathogen.

Immunisation is when dead or inactive pathogens are injected into the body. These carry antigens, so even though they’re harmless they still trigger an immune response- your white blood cells produce antibodies to attack them. Some of these white blood cells will remain in the blood as memory cells so if live pathogens of the same type ever appear, the antibodies to kill them will be produced immediately.

The advantages of immunisation: is that it stops you from getting ill. If most people are immunized the disease won’t be able to spread as easily.

Disadvantages of Immunisation: There can be short term side effects such as redness or swelling at the site of the injection.

Antibiotic resistance- Some Bacteria are naturally resistant to certain antibiotics. Misuse of Antibiotics e.g doctors over prescribing them or patients not finishing a course, has increased the rate of development of resistant strains.

Clinical trials are blind- the patient in the study doesn’t know whether they’re getting the drug, or the placebo. Sometimes they’re double blind- neither the patient nor the scientist knows until the results have been gathered.

The lens is elastic, so the eye can focus light by changing the shape of the lens- this is known as accommodation.

To look at distant objects: The ciliary muscle relaxes, which allow the suspensory ligaments to pull tight. This pulls the Lens into a less rounded shape so light is refracted less.

To look at closer objects: The ciliary muscle contract, which slackens the suspensory ligament. The lens becomes a more rounded shape, so light is refracted more.

The cornea – Reflects light into the eye.

The iris- controls how much light enters the pupil.

The lens- refracts the light, focusing it onto the retina.

The retina- is the light sensitive part and it’s covered in receptors called rods and cones, which detect light.

Long-sighted people are unable to focus on near objects. You can use glasses or contact lenses with a convex lens to correct it. This occurs when the lens is the wrong shape and doesn’t bend the light enough or the eyeball is too short.

Shortsighted people are unable to focus on distant objects. You can use glasses or contacts with concave lens to correct it. This occurs when the lens is the wrong shape and bends the light too much or the eyeball is too long.

Neurons are adapted to their function because they have branched endings so they can connect with lots of other neurons. They have a sheath along the axon that acts as an electrical insulator, which stops the impulse getting lost. It also speeds up the electrical impulse. They’re long which speeds up the impulse (connecting with another neuron just slows it down so one long neuron is quicker than lots of short ones joined together.)

The connection between two neurones is called a synapse. It’s basically just a very tiny gap. The nerve signal is transferred by transmitter chemicals, which diffuse across the gap. These chemicals then set off a new electrical impulse in the next neuron.

The nervous systems use electrical impulses to allow very quick responses. Reflex actions are automatic so they’re even quicker.

Stimulant drugs increase the amount of transmitter chemical at some synapses, which increases the frequency of impulses at neuron 2.

Depressants increase the amount of a different transmitter chemical at some synapses, which decreases the frequency of impulses set off along neuron 2. This decreases brain activity.

 

Smoking damages the cilia on the epithelial tissue lining the trachea, bronchi and bronchioles, which encourage mucus to be produced. But excess mucus can’t be cleared because the cilia are damaged, so it sticks to air passages causing smoker’s cough.

Alcohol is poisonous. Enzymes in the liver break down alcohol and some of the products are toxic. If you drink too much Alcohol over a long period of time these toxic products can cause the death of liver cells, forming scar tissues that stop blood reaching the liver- this is cirrhosis.

Homeostasis is Maintaining a constant internal environment. Conditions in the body need to be kept steady so that cells can function properly. This involves balancing inputs with outputs.

-       Levels of CO2: Respiration constantly produces C02, which you need to get rid of.

-       Water content: You need to keep a balance between the water you gain and the water you loose.

-       Body temperature: You need to get rid of excess body heat when you’re hot, but retain the heat when the environment is cold.

Negative feedback: Changes in the environment trigger a response that counteracts the changes – e.g a rise in body temperature causes a response that lowers body temperature. This means that the internal environment tends to stay around a norm, the levels at which the cells work best. This only works within certain limits- if the environment changes too much then it might not be possible to counteract it.

Negative Feedback works automatically.

Vasodilation is when Blood vessels close to the surface of the skin widen. This allows more blood to flow near the surface, so it can radiate more heat into the surroundings. This happens when you’re too hot.

Vasoconstriction is when Blood vessels near the surface constrict so that less heat can be transferred to the surrounding. This happens when you’re too cold.

 

Body temperature is controlled by the brain. All enzymes  have an optimum temperature they work best at. For enzymes in the human body its around 37 degrees. There’s a thermoregulatory Centre in the brain, which acts as your own personal thermostat. It contains receptors that are sensitive to the blood temperature in the brain. It also receives impulses from the skin that provides information about skin temperature. The brain can respond to this information and bring out changes in the body’s temperature using the nervous and hormonal system to initiate temperature control mechanisms such as Vasoconstriction and vasodilatation.

 

Insulin controls blood sugar levels. The level of glucose in the blood must be kept steady.

Hormones travel in the blood so it can take quite a while for them to get to where they’re needed in the body. Electrical impulses sent along the nerves travel much faster. This means it takes the body longer to respond to a hormone such as insulin that to a nervous impulse.

Type 1 Diabetes is where the pancreas produces little or no insulin. The result is that a person’s blood glucose level can rise to a level that can kill them.

People with type 1 diabetes can partly control the condition by having a carefully controlled diet, but they also need to inject insulin into the blood at meal times. This will make the liver remove the glucose as soon as it enters the blood from the gut, when the food is being digested. This stops the level of glucose in the blood from getting to high and is a very effective treatment.

The amount of insulin that needs to be injected depends on the person’s diet and how active they are.

 

Most cells in your body have a nucleus. The nucleus contains your genetic material in the form of chromosomes.

 

Chromosomes always come in pairs – one from each parent.

 

Chromosomes carry genes. Different genes control the development of different characteristics. E.g. Eye colour.

 

A gene is a short length of the chromosome, which is quite a long length of DNA.

 

The different versions of the same gene are called alleles.

 

Most of the time you have two of each gene (two alleles) – one from each parent. If the alleles are different you have instructions for two different characteristics (e.g. blue eyes or brown eyes), but you only show one version of the two (e.g brown eyes). The version of the characteristics that appears is caused by the dominant allele. The other allele is said to be recessive. The recessive allele is only expressed if there’s no dominant allele present.

 

 

Dominant alleles are always shown with a capital letter and recessive alleles with a small letter.

 

If your Homozygous for a trait you have two alleles the same for that particular gene. E.g. CC or cc.

 

If your heterozygous for a trait you have two different alleles for that particular gene. E.g. Cc.

 

Your genetic makeup (i.e. the alleles you have for a particular gene) is known as your genotype.

 

The characteristics that these alleles produce (e.g. brown eyes) is known as your phenotype.

 

When you breed two organisms together to look at a characteristic that’s controlled by one gene, it’s called a Monohybrid cross.

 

There’s an equal chance of having a boy or a girl and there’s a genetic diagram to prove it. Even though we’re talking about inheriting chromosomes here and not single genes, the genetic diagram still works the same way.

When you plug all the letters into the diagram, it shows that there are two ** results and two XY results, so there’s the same probability of getting a boy or a girl.

This 50:50 ratio is only a probability. If you had four children they could all be boys.

 

The allele which causes cystic fibrosis is a recessive allele, ‘f’, carried by about 1 person in 25. Because it’s recessive, people with only one copy of the allele won’t have the disorder- they’re known as carriers. For a child to have a chance of inheriting the disorder, both parents must be either carriers or sufferers. The diagram shows there’s a 1in 4 chnace of a child having the disorder if both parents are carriers.

 

Knowing about genetic disorders can arise difficult issues:

-       Should all family members be tested to see if they’re carriers? Some people might prefer not to know, but is this fair on any partners or future children they might have?

-       Is it right for someone who’s at risk of passing on a genetic disorder to have children? Is it fair to put them under pressure not to, if they decide they want children?