Principles of organisation

communicable diseases

Spread from person to person. Spread by pathogens such as bacteria and viruses

Non communicable diseases

Can’t be spread from person to person

Other risk factors for diseases

Poor diet, high levels of stress

How do different diseases interact

Tuberculosis is a communicable lung disease. Most people’s immune system can fight it off, however someone with e.g. HIV has a weakened immune system. People with defective immune systems are most likely to suffer from diseases

Sometimes one disease can be the cause of another

HPV can cause cervical cancer. Usually caused by HPV infecting cells of the cervix

Sometimes diastases are triggered by immune system

Sometimes diseases can be triggered by the immune system, e.g allergies or asthma. Results from immune system fighting off pathogen but then the person is left with an allergy

Sometimes, a mental illness…

Is triggered by a physical one

Top and bottom of the leaf

Upper and lower epidermis. Thin cells. Protects surface of the leaf. It’s transparent, allowing light to pass through. Also covered with oily material called waxy cuticle. Reduces evaporation of water from surface of the leaf. Prevents it from drying it

stomata

Near the lower epidermis, tiny pores. Allow carbon dioxide to enter, oxygen to leave. Also helps control amount of water vapour passing out of leaf.

Guard cells

Either side of stomata

Palisade mesophyll

Palisade cells, full of chloroplasts

Spongy mesophyll

Under palisade mesophyll. Full of air spaces, allow carbon dioxide to diffuse from stomata, through spongy mesophyll to palisade mesophyll

Xylem

Water and mineral ions from roots to the stem and leaves. Some water used for photosynthesis

Phloem

Dissolved sugars from leaves to the rest of the plant. Some can be used immediately for glucose or stored as starch. TRANSLOCATION

Root hair cell adaptation

Covered in hairs for larger surface area of root to absorb mineral ions and water more effectively. No chloroplast because no light.

Xylem cells adaptations

Found in plant’s stem. Long tubes. Thick walls containing lignin, provides support for plant. However, because of this, xylem cells die. End walls of cellls are broken down. Cells from long tube. No internal structures. Easy flow of water and minerals

Phloem

2 different types of cells. Phloem vessel cell, no nucleus, limited cytoplasm. End walls of cells have sieve plate pores, allow dissolved sugar to move through. Because of limited cytoplasm, not a lot of mitochondria, so each phloem vessel cell has a companion cell, connected by pores. These contain lots of mitochondria, provide lots of energy

Transpiration

Water is constantly evaporating from surface of the leaf. Water passes from xylem into leaf or replace water that’s been lost. Water is drawn from root hair cells to be passed into the xylem. This whole process is the transpiration stream

Factors that affect transpiration

• Temperature

• Dry conditions

• Windy conditions

• Light intensity

Stomata

Surrounded by two guard cells. When light intensity is high, guard cells swell, change shape, open. Carbon dioxide diffuses into leaves to be used in photosynthesis.

Under hot conditions, it closes to reduce water loss. No photosynthesis

Coronary heart disease

Coronary arteries found surface if heart muscle. Provides oxygen for muscle cells. Layers of fatty material build up in the arteries. Causes the arteries to narrow. Recuses flow of blood= lack of oxygen. Can result in heart attack.

Treatments for coronary heart disease

Statins

Drugs, reduce amount of cholesterol in blood, slows down the rate of fatty materials building up in arteries.

Advantages= effective.

Side effects= liver problems

Stents

If total blockage of artery, stents are used, tubes inserted into coronary arteries to keep them open. Blood can flow normally through artery. Will not prevent other regions from narrowing. Not treating underlying causes

Valves

Sometimes they don’t fully open. Heart pumps extra hard. Causes heart to enlarge. Sometimes they’re leaky.

We can replace them from mechanical ones made of metal or from animal. Mechanical valves increase risk or blood clotting but can last life time. Patients have to take anti clotting drugs. Ones from animals need to be replaced.

Heart failure

Heart transplant.

Problems: not enough hearts available

Patient must take drugs to stop heart from being rejected by immune system. Temporary solution is artificial hearts, however increase risk of blood clotting