B1

Natural clones are individuals with identical genes, so any differences between individuals must be due to enviromental factors.

Some organisms reporduce asexually to produce clones 

Identical twins are formed when cells of an embryo seperate.

Artifical clones can be produced when a nucleus froma body cells is transferred to an unfertilised egg.

Embryonic stem cells can develop into any type of specialised cell. Adult stem cells can develop into fewer cell types.

Being unspecialised, stem cells have potential in the treatment of disease.

Organisms that cause infectious dieases include bacteria and viruses.

Damages to cells during  an infection is because of toxins produced by the mircoorganism.

Microorgamisms reproduce very rapidly in the human body, to produce very large numbers.

The immune systemhas types of white blood cell that;

• destroy microorganisms by engulfing and digesting them 
• produce antibodies against antigens on their surface 

Every antigen has a corresponding antibody that recognises it.

After an infection, memory cells remain in the body so that antibodies can be produced very quickly. The person now has immunity to the mircoorganism.

Vaccines

• contain a safe form of a disease-causing microorganism
• produce immunity (because memory cells remain after the vaccination)
• are very safe, but not risk-free (possible side effects; reactions vary because of genetic differences)

To prevent epidemics, a high percentage of the population must be vaccinated

Drug and vaccine trials ensure safety and effectiveness. The trials first involve animals and human cells. Later human trials involve healthy volunteers and people with the illness. Control groups use an existing drug or a placebo. The use of placebos raises ethical issues.

Trials can be;

•  open-label (new drug is known by researchers and patient)
• 'blind' (the patients do not know who is recieving the new drug)
• 'double-blind' (neither patients nor researcher knows who is being given the new drug).

Antimicrobials 

• kill or inhibit the growth of bacteria, fungi and viruses 
• include antibiotics, which are used to kill bacteria (only)

Over tim, bacteria and fungi can develop resistance to antimicrobials 

To reduce this, only use antibiotics when necessary and complete the course.

The heart is part of hte circulatory system. It is a double pump (left side to body, right side to lungs) and has it own blood supply.

The structure of the arteries, capillaries and veins is related to their functions.

Heart attacks are caused by fatty deposits blocking the blood supply to the heart. 

Heart disease is caused by lifestyle factors (poor diet, stress, smoking, misuse of drugs) and/ or genetic factors.

These factors are identified by large scale epidemiological and genetic studies.

Heart rate can recorded by measuring the pulse rate.

Blood pressure is a measure of the pressure of the blood on an artery wall. It is measured as two numbers: the higher number is when the heart is contracting, the lower number when it is relaxed.

Values of 'normal' heart rate and blood pressure are given as a range, as they vary in individuals.

High blood pressure increases the risk of heart disease.

Nervous and hormonal systems maintain a constant internal enviroment in the body (homeostasis).  These control systems:

• are 'automatic'
• have receptors, processing centres and effectors 

Negative feedback is used to reverse any changes in the body's state.

Hormonal control of urine concentration is by ADH.

Alcohol reduces ADH secretion

Ecstasy (MDMA) increases ADH secretion

A balanced body water level maintains cell water concentration. This vital for cell function.

Input of water is form drinks, food and respiration; losses are through sweating, breathing. faeces and urine.

The kidneys respond to water concentration in the plasma by producing dilute or concentrated  urine

Nervous and hormonal systems maintain a constant internal enviroment in the body (homeostasis).  These control systems:

• are 'automatic'
• have receptors, processing centres and effectors 

Negative feedback is used to reverse any changes in the body's state.

Hormonal control of urine concentration is by ADH.

Alcohol reduces ADH secretion

Ecstasy (MDMA) increases ADH secretion

A balanced body water level maintains cell water concentration. This vital for cell function.

Input of water is form drinks, food and respiration; losses are through sweating, breathing. faeces and urine.

The kidneys respond to water concentration in the plasma by producing dilute or concentrated  urine

Nervous and hormonal systems maintain a constant internal enviroment in the body (homeostasis).  These control systems:

• are 'automatic'
• have receptors, processing centres and effectors 

Negative feedback is used to reverse any changes in the body's state.

Hormonal control of urine concentration is by ADH.

Alcohol reduces ADH secretion

Ecstasy (MDMA) increases ADH secretion

A balanced body water level maintains cell water concentration. This vital for cell function.

Input of water is form drinks, food and respiration; losses are through sweating, breathing. faeces and urine.

The kidneys respond to water concentration in the plasma by producing dilute or concentrated  urine