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OCR Science B2

OCR 21st Century Science B2

Symptons of an infectious disease are caused by damage done to [] by [] or the [] they produce cells--microorganisms--toxins--
In suitable conditions such as those inside a human body, microorganisms can [] rapidly to produce very large numbers reproduce--.
Bacteria reproduce by each [] into [] n[] ones splitting--two new--.
White blood cells are part of the body's [] system immune-- and can destroy [] by e[]ing and d[]ing them or by producing [] microorganisms--engulfing--digesting--antibodies--.
Antibodies recognise microorganisms by the [] that the carry on their [] antigens--surface--.
As different []s have different antigens microorganisms--, a different [] is needed to recognise each different type of microorganism antibody--.
Once the body has made the antibody to recognise a particular microorganism, [] cells can make that antibody again very quickly memory--, therefore protecting against that particular microorganism in the [] (i.e. creating []) future--immunity--.
Vaccinations provide protection from microorganisms by establishing [] cells that produce [] quickly on reinfection memory--antibodies--.
A [] usually contains a safe (i.e. dead or weakened) form of the disease-causing microorganism vaccine--.
To prevent epidemics of infectious diseases, it is necessary to vaccinate a [] percentage of a population high--: this [] the number of people able to [] the disease and [] it on reduces--catch--pass--; unvaccinated people are un[] to catch the disease unlikely--.
Vaccines and drugs can not be completely r[]-free because people have varying levels of [] effect to them risk--side--.
Due to [] differences, people react in varying ways to medicine genetic--.
Chemicals called [] can be used to kill, or inhibit, bacteria, fungi and viruses antimicrobials--.
Antibiotics are a type of an[] antimicrobial, and are effective against [] but not [] bacteria-viruses--.
Over a period of time, bacteria and fungi may become []t to antimicrobials resistant--.
Changes (which are []) in the g[] of microorganisms sometimes leads to type which are less affected by []s random--genes--antimicrobials--. Thus, Over a period of time, bacteria and fungi may become []t to antimicrobials resistant--.
|Development of Resistance| 1)[] changes ([]s) occur in the []s of individual bacterial cells random--mutations--genes-- 2)Some mutations [] the bacterial cell from the effects of the [] protect--antibiotic-- 3)Bacteria without the mutation [] or cannot [] with the [] present die--reproduce--antibiotic-- 4)The resistant bacteria are able to [] with less competition from [] bacterial strains reproduce--normal--.
In order to stop bacteria surviving antibiotics and creating resistant types (and generally stop resistance), we should only use antibiotics when ne[] necessary-- and always c[] the course complete--.
Understand that new drugs and vaccines are first [] for s[] and e[] tested--safety--effectiveness--using [] and [] cells grown in the [] animal--human--laboratory--.
After tests using cells grown in the laboratory: h[] trials may then be carried out human--: a) on h[] volunteers to test for s[] healthy--safety-- b)on people with the [] to test for [] and [] illness--safety--effectiveness--.
There are three main types of clinical trial: '[]', '[]-[]' and '[]-[]' 'blind', 'double-blind' and 'open-label'. In 'blind' and 'double-blind' trials, one group of volunteers (the test group) receives the new drug, while another (the control group) receives the [] drug for that illness existing--; if no treatment currently exists, the control group is given a placebo: the researchers look for differences between the experimetal group and the control group.
The volunteers do not know, which group they are in, but the researchers do, in which type of trial? Blind trial.
Which type of trial: the volunteers don't know which group they're in, and neither do the researcher, until the [] of the trial double-blind--end--. This removes the chance of b[] and makes results more r[] bias--reliable--; however, they are more c[] to set up complex--.
Both the doctor and the patient know what drug is being given in which type of trial? Open-label trial. This type of trial tends to occur when there's no other treatment, and the patients are so [] that doctors believe that they will not [...] ill--recover from their illness.
Long-term human trials are important to make sure that dosing the patients (over a long period of time) won't cause [] in the [] problems in the future: the problems could be due to the drug's side-effect(s) developing su[]ly subtly.
There are ethical issues to do with placebos. Many doctors have an aversion to giving placebos and feel that doing so is unfair to the patient because they feel that the patient will not benefit (i.e. will not get better). They may feel guilty for being d[]ful deceitful--.
Blood that enters the heart from the [] side is deoxygenated right--, it is hence sent to the [] to be [] lungs--oxyginated--; after that, it is sent to the [] side of the heart where it's [] throughout the body before returning to the [] side left--pumped--right--; the two pumps are joint to form one organ, hence the heart is called a [] pump double--.
The heart requires a constant supply of blood for itself in order to keep beating.
The []s carry blood from the heart arteries--. Their structure is related to their function. Blood in the arteries is under high p[] generated by the [] pressure--heart--: arteries have t[] outer walls and thick layers of m[] and [] f[]s thick--muscle--elastic fibres--.
The [] carry blood to the heart veins--. Their structure is related to their function. The blood in veins is under lower []re than the blood in arteries. The veins have a [] wall and t[] layers of m[] and [] f[] pressure--thin--muscle--elastic fibres--. Unlike arteries, veins have one-way []s in them to keep the blood moving in the correct direction valves--.
The function of capillaries is to allow f[] and o[] to diffuse to c[] food--oxygen--cells--, while [] is d[] from them waste--diffused--. Their structure suits their function as they have [] walls - one [] thick - that enable them to acheive their function. thin--one--.
The heart rate can be measured by means of recording the p[] rate pulse--.
Blood pressure measurements record the pressure of the [] on the []s of the [] blood--walls--arteries--.
A blood pressure is given as two numbers (e.g. 85/75), the first number for when the heart is [], and the second for when the heart is [] contracting--relaxed--.
Usually, measurements for factors such as heart rate and blood pressure are given within a [] range, because individuals [] vary.
Blood vessels called the [] arteries supply blood to the heart muscles coronary--; [] deposits can build up in such arteries fatty-- - if they become blocked a [] [] can happen heart attack--.
Heart disease is usually caused by [] factors and/or [] factors lifestyle--genetic--. Lifestyle factors that contribute to the risk of heart disease include poor d[], s[]s, c[] s[]ing, m[]use of d[]s poor diet, stress, cigarette smoking, misuse of drugs.
Regular and moderate e[] reduces the risk of developing heart disease exercise--.
Epedemiology is the study of [] affecting the health and illness of populations factors--. In a typical cohort study, researchers examine [] groups of people two--: those with the [], and those without illness--. They can carry out examinations by following the group's [] over several []s or []s, looking at their [] records progress--months--years--medical--.
Having high blood pressure [] the risk of heart disease increases--.
Misuse of drugs (e.g. Ecstasy, cannabis, nicotine and alcohol) can have a negative effect on h[], including heart r[] and blood [] health--rate--pressure--, increasing the risk of a [] a[] heart attack--.
Our bodies have [] control systems to maintain a steady rate. First, we need []s to detect when things (e.g. temperature) change automatic--receptors--, then, we need a [] centre to receive this information and coordinate our re[] automatically processing--reponse--; the n[] and h[] systems are involved nervous--hormonal-- (i.e. they help in maintaining a constant internal environment [homeostatis]). Finally, we need []s to produce a [] that ensures that the factor in question stays the same effetors--response--.
Automatic control systems throughout the [] maintain a range of factors at [] levels that are required for []s to function properly body--steady--cells--.
The process of maintaining internal conditions is known as homeostasis.
Negative feedback ensures that, in any control system, changes are re[] and returned back to the set [] reversed--level--. For example, negative feedback keeps our body temperature constant: if we get too hot, blood vessels in our skin become [] and we [] heat larger--lose--, but if we get too cold, blood vessels in our skin become [], we [] less heat and the body warms up smaller--lose--. Other factors also controlled in the body by negative feedback are blood oxygen levels and salt levels.
Between the [] and the [] of a control system, the negative feedback system reverses any changes to the system's s[] s[]e effector--receptor--steady--state--.
A balanced water level is important for maintaining the c[] of cell c[]s at the correct level for cell [] concentration--contents--activity--.
Water levels are controlled by b[]cing gains from drinks, food and re[] with losses through ex[] (e.g. sweating, breathing, urination, faeces) balancing--respiration--excretion--.
Kidneys maintain our [] balance by producing [] of different []tions water--urine--concentrations--. The kidney is controlled by the []-[]ic []e released by the []ary []d anti-diaretic hormone--pituary gland--.
Kidneys blance water levels by producing urine with dilution in response to the concentration of blood [] plasma--apart from water, the concentration is affected by external [], ex[] level, and intage of []ds and s[] temperature--exercise--fluids--salt--.
Kidneys play a vital role in balancing levels of water, w[] and other c[] in the [] waste--chemicals--blood--.
The concentration of urine is controlled, via the kidney, by a h[] called [] hormone--ADH--, which is released into the b[] by the [] [] bloodstream--pituitary gland--.
When there is too little water in the body, the blood plasma is more [], thus [] ADH is released into the [] by the pituary gland concentrated--more--|blood|--. When the ADH reaches the []s, it causes them to [] more water kidneys--absorb-- thus [] water is used in urine and the urine is more [] less--concentrated--. When the plasma is more dilute (more water) and [] ADH is released into the bloodstream, more water is allowed to [] via [], producing more [] urine less--leave--urine--dilute--. This method of control is an example of [] [] negative feedback.
Alchol result in the production of a greater volume of [] urine, due ADH []ion dilute--decreased--, which can lead to d[] and adverse effects on h[] dehydration--health--.
The drug Ecstasy results in a s[]er volume of [] concentrated urine, due to [] ADH production smaller--more--increased--.
|Ethical Issues of Using Placebos| Critics of such trials argue that if a proven e[]e t[]y exists, a placebo should not be used effective therapy--. . But proponents argue that placebo trials are still crucial to prove the effi[]cy and s[]y of many treatments. efficacy--safety--
N[]ous and h[]al co[]tion systems are involved in maintaining a constant internal environment (homeostatis) nervous--hormonal--.
The more ADH produced, the more [] the urine concentrated; the less ADH produced, the more [] the urine dilute--.
Viruses can only reproduce inside host [] cells.
Virus reproduction: the virus gets inside a [] and once there [] [] cell--takes over--, it then makes hundreds of []s of [] of itself thousands--copies--. Eventually the copies [] the whole host cell and [] it open fill--burst--. The viruses are then passed out in the []m, the a[]s or by other routes. bloodstream--airways--.
Created by: Toluo
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