B1 - Understanding Organisms

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Blood Pressure

Blood pressure is measured in mmHg (milligrams of mercury).

You can meassure blood pressure in two different ways:

Systolic pressure - maximus pressure

DIastolic pressure- the pressure between heart beats

Blood pressure is...

increased by stress, high alcohol intake, smoking and being overweight

decreased by regular excersise and a balanced diet

High blood pressure can cause blood vessels to burst this can cause damage to the brain (stroke). It can also damage the kidneys.

Low blood pressure can cause dizziness and fainting because the blood supply to the brain is reduced, and poor circulation to the areas like fingers and toes

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Fitness and Health

Fitness - the abity to do physical activity 

Health - free from disease 

Fitness is measured using cardiovascular efficency

Or strength. flexibility. stamina. agility. speed

(Ways of measuring fitness should be evaluated to check effectiveness in particular situtations)

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Smoking increases blood pressure.

CO (Carbon Monoxide)  reduces the oxygen-carrying capacity of the blood. It combines with haemoglobin in red blood cells, preventing oxygen combining with the haemoglobin. This causes an increase in heart rate to compensate for the reduced amount of oxygen carried in the blood.

Nicotine itself increases the heart rate 

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Diet and Heart Disease

Heart Disease is cause by restricted blood flow to the heart muscle.

The risk of getting heart disease increased by:

-High level of saturated fat in a diet, which leads to a build up of cholesterol (a plaque) on the wall of the arteries. 

-High levels of salt , which can increase blood pressure since it makes the liver's osmosis of fluids less efficient.

Plaques cause narrowing of the arteries. This makes thrombosis (blood clots) more likely to happen, which could block the artery 

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A Balanced Diet & Protein

Glucose units -> complex carbohydrate

amino acids ->  protien

glyrol + fatty acids -> fat

If you eat too much fat or carbs:

-Carbohydrates are stored in the liver as glycogen or converted into fats.

-Fats are stored under the skinand around organs as Adipose tissue.

Protein (EAR) Estimated Daily Requirement 

EAR in g = 0.6 x body mass in kg      EAR is only estimated and based on averages.

First Class Protein contains all the amino acids necessary for the human body (meat & fish)

Second Class Protein doesn not contain all essential amino acids (plant protien)

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BMI = mass in kg ÷ (height in m)2

30+ = obese

25-30 = overwieght

20-25 = normal

less than 20 = underwieght

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Malaria & Cancers

Malaria is caused by a protozoan called Plasmodium, which feeds on human red blood cells.

Mosquitos are the Vectors. Plasmodium is a parasite. Humans are hosts.

Mosquitos breed in swarms then lay their eggs in stagnant water. By spawn camping we kill them.

Cancers are malignant tumours : the cells display uncontrolled growth and may spread.

Warts are an example of benign tumours : the cells divide slowly and are harmless.

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Pathogens produce the symptoms of diseases by damaging the body's cells or creating toxins.

The body responds by creating antibodies that lock into the antigens on the pathogen.

Each Pathogen has different antigens.

Active Immunity - when the human white blood cells create antibodies. Takes time but long-term.

Passive Immunity - when we just inject in antibodies from other humans. Quick but short-term

Vaccination is a process by which we inject in a dead/harmless/inactive pathogen (with antigens) and the antigens trigger the white blood cells' immune response, producing the correct antibodies. Memeory Cells (T cells /Lymphocytes) will remain in the body, providing long-lasting immunity.

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Treatment and Trials

     Antibiotics Vs Bacteria/Fungi                       Antiviral Vs Viruses

An antibiotics destroys a pathogen ; An antiviral slows down the pathogen's development. The use of antibiotics has meant that some resitant forms of bacteria have become more common than the non-resistant forms.

We test new medicines on animals/human tissues/computer models before human trials.      

Blind trial - patient doesn't know if they are taking the drug or a placebo

Double-blind trail - neither the doctor or the patient know.

This avoid the 'feel-good factor' and a biased opinion.

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The Eye

The pupil allows light rays to enter the eye. The outer cornea refracts light waves. The coloured iris controls the amount of light entering the eye. The ciliary muscles control suspensory ligaments. The lens in convex and refracts light rays and focuses light onto the retina. A focused inamge forms on the retina, which is positioned at the back of the eye and is sensitive to light.

Binocular Vision is neat because we can focus on stuff that is near or far away. Fucusing like that is called Accomdation

To fucus on distant objects, the ciliary muscles relax, and the suspensory ligaments tighten, so the lens has a less round shape.

To focus on closer objects, the ciliary muscles tense, and the suspensory ligaments slaken, so the lean regais a more rounded shape due to the elasticity. 

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Eye Faults

Red-green colour blindness is caused by a lack of specialised cells in the retina. 

In long-sightedness, the eyeball is too short or the lens is too thin, so the image is focused behind the retina.

In short-sightedness, the eyeball is too long or the lens is too thick, so the image was focused infront of the retina.

Coreneal surgery or glasses can be used to correct sight problems.

A convex lens is used to correct long sight, a concave lens to correct short sight.

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Nerve Cells

nerve cells = neuron

These are the actions of a reflex arch:

stimulus-->receptor-->sensory neuron-->central nervous system-->motor neurone-->effector--> response 

The pathway of a spinal reflex:

receptor-->sensory neurone-->relay neurone-->motor neurone-->effector

Neurones are adapted by being long, having branched ends and insulator sheath.

The gap between neurones is called a synapse. The arrival of an electrical signal causes a release of neurotransmitters, which diffuse across the synapse. Then that transmitter binds to the receptor molecules in the mebrane of the next neuron cauing the impluse to continue.

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Drugs & Smoking & Alcohol

performace enhancers eg. anabolic steroids

Depressants block the transmission of nerve impluses by binding with the recptors in the memebrane of the reciving neurons. Simulants cause a increase in the amount of neurotransmitters that pass between synapses.

Smoker's Cough is caused by chemicals in cigarettes stopping cilia movement meaning that the cilia are irritated by the smoke's particulates and can't serve their purpose and move the trachea and bronchile's mucus.

Alcohol is a toxin and it causes the cirrosis of the liver as the liver is damaged whilst breaking the chemical down.

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Homeostasis - keeping a constant internal environment. 

Our body's homeostasis is controlled by automatic systems that keep lots of factors like the body's temperature stable.The body tempreture of 37 degrees is the optimum temperature for certain enzymes to function.

Blood temperature is monitored by the hypothalamus glad in the brain. Reaction to extreme temperature is controlled using vasoconstriction and vasodilation. 

Vasoconstriction is the constriction of small blood vessels in the skin, this causes less blood flow and therofre heat loss. Vasodilation is the dilation of blood vessels in the skin meaning more heat loss as the blood is cooled by the outside temperatures. More heat transfer.

Insulin controls blood sugar levels by turning glucose into glycogen.

Hormones are slower than nervous reactions because hormones travel in the blood. Type 1 diabetes is caused by the pancreas not producing any insulin; treated by insulin injections. Type 2 diabetes, blood produces too little insulin or body not reacting to it; treated by diet & exercise.

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Plant Hormones

Phototropism - a plant's response to light. Positively Phototropic = grows towards light

Geotropism - a plant's response to gravity. Negatively Geotropics = grows away from the pull of gravity

Auxins are plant hormones, they are made in the root and shoot tips. 

Plants grow in particular directions because auxins are de-activated by light meaning that there are more auxins in the side of the plant that is in shadow. The auxins work by stretching the plant cells, thus a plant will grow in the direction of light because the cells on the shadowed side are stretched.

Plant hormones are used in industry:

-as selective weedkillers

-rooting powder (to increase root growth of cuttings)

-to decelerate or accelerate fruit ripeningto meet market demands

-to control dormancy in seeds

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Variation & Inheritance

Alleles are different versions of the same gene. Dominant and recessive trates are dependant on dominant or recessive Alleles.

Humans have 64 chromosomes or 32 chromosomal pairs. A human sex cell has 32 chomosomes.

XxMalesxX   XyFemalesXy   A sperm either carries an X or a Y chromosome. 50/50

Genetic variation is caused by:

- Mutation

-Rearrangement of genes during formation of gametes (meosis)


A monohybrid cross involves a pair of chromosomes being controlled by a single gene, one being dominant. Homozygous = same alleles. Hetrozygous = different alleles. A Person's genotype is their genetic makeup, their phenotype is which alleles are expressed.

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