B2 - Organisation

• Are in thorax - the top part of your body - separated from abdomen by diaphragm.
• Lungs surrounded by the pleural membranes.
• Air breathed in goes through trachea - splits into two tubes - bronchi (each one is a bronchus). Split into smaller tubes - bronchioles. End at alveoli, where gas exchange occurs.
• Lungs contains millions of alveoli surrounded by network of blood capillaries. Blood passing next to alveoli has just returned to lungs from rest of body, so contains lots of CO2 and little O2. Oxygen diffuses out of alveolus - high concentration - into blood. CO2 diffuses out of blood into alveolus - low concentration - to be breathed out. When blood reaches body cells O2 is released from red blood cells and diffuses into body cells - low concentration. CO2 diffueses out of body cells - high concentration - into blood. Then carried back to lungs.
• Breathing Rate in Breaths Per Minute = number of breaths / number of minutes

• Circulatory system made up of heart, muscles & blood. Humans have double circulatory system - two circuits joined together:Right ventricle - pumps deoxygenated blood to lungs to take in oxygen. Blood then returns to heart. Left ventricle - pumps oxygenated blood around other organs of body. Blood gives up oxygen at body cells and deoxygenated blood returns to heart to be pumped out to lungs again.
• Heart - pumping organ that keeps blood flowing around body. Walls of heart mostly made of muscle tissue. Heart has valves to ensure blood flows in right direction - not backwards.
• How heart uses its 4 chambers - right atrium, right ventricle, left atrium and left ventricle - to pump blood: Blood flows into the atria from vena cana & pulmonary vein. Atria contract, pushing blood into ventricles. Ventricles contract, forcing blood into pulmonary artery & aorta & out of heart. Blood then flows to organs through arteries, and returns through veins. Atria fill again & cycle starts over.
• Heart needs own supply of oxygenated blood - coronary arteries branch off aorta & surround heart giving it oxygenated blood.
• Resting heart rate controlled by croup of cells in right atrium wall - act as a pacemaker. Cells produce small electric impulse which spreads to surrounding muscle cells, causing them to contract. Artificial pacemaker used to control heartbeat if natural pacemaker cells don't work properly - little device implanted under skin and has wire going to heart. Produces an electric current to keep heart beating regularly.

1. Arteries - carry blood away from heart. Heart pumps blood out at high pressure so artery walls are stong & elastic. Walls are thick compared to size of hole down middle - the 'lumen'. Arteries contain thick muscle layers for strength, & elastic fibres to allow them to stretch & spring back.

2. Capillaries - involved in exchange of materials at tissues. Arteries branch into them. Are really tiny. Carry blood really close to cells in body to exchange substances with them. Have permeable walls so substances can diffuse in & out. They supply food & oxygen, & take away waste. Walls usually one cell thick - increases rate of diffusion by decrerasing distance over which it occurs.

3. Veins - carry blood to heart. Capillaries eventually join up to form veins. Blood is at low pressure in veins so wall not as thick as artery walls. Have bigger lumen than arteries to help blood flow. Have valves to keep blood flowing in right direction.

• Rate of Blood Flow = volume of blood / number of minutes

• Specialised cells --> tissues --> organs --> organ systems.
• Large multicellular organisms have different systems in them for exchanging & transporting materials.
• Tissue = group of similar cells working together to conduct particular function. Can include more than 1 type of cell. Mammals:
  • Muscular tissue - contracts to move what it's attached to
  • Glandular tissue - makes & secretes chemicals - enzymes, hormones, etc.
  • Epithelial tissue - covers some parts of body - inside of gut, etc.
• Organ - group of different tissues working together to perform certain function - stomach, etc. Made up of:
  • Muscular tissue - moves stomach wall to churn food
  • Glandular tissue - makes digestive juices to digest food
  • Epithelial tissue - covers outside & inside of stomach
• Organ system - group of organs working together to perform function - digestive system - breaks down & absorbs food. Made up of organs - glands, stomach, liver & small & large intestines.
• Organ systems work together to make entire organisms.

• Usually make reaction faster by raising temp. - however would speed up unwanted reactions too. Also a limit to how far you can raise temp. inside living creature before cells start getting damaged. Living things produce enzymes - biological catalysts - reduce need for high temps. & we only have enzymes for useful chemical reactions. Catalyst = substance that increases speed of reaction without being changed or used up in reaction.
• Enzymes - large proteins made of chains of amino acids, folded into unique shapes. Chemical reactions usually involve things being split or joined. Every enzyme has unique active site that fits onto substance involved in reaction. Only catalyse 1 specific reaction as substate has to fit in active site.
• Increasing temp. increases rate of reaction at first - too hot - some of bonds holding enzyme together break - changes shape of active site so substrate won't fit - enzyme denatured. All enzymes have optimum temperature.
• pH - too high or low, pH interferes with bonds holdning enzyme together. Changes shape of active site & denatures enzyme. Enzymes have optimum pH - usually pH 7.

• Starch, proteins, fats - big molecules. Can't pass through walls of digestive system so digestive enzymes break them into smaller ones. Smaller, soluble molecules can pass easily through walls of digestive system, allowing them to be absorbed into bloodstream.
• Carbohydrases convert carbohydrates into simple sugars. Amylase - type of carbohydrase - breaks down starch into maltose & other sugars. Amylase is made in the salivary glands, pancreas & small intestine.
• Proteases convert proteins into amino acids. Made in the stomach (called pepsin there), pancreas and small intestine.
• Lipases convert lipids into glycerol & fatty acids. Made in pancreas & small intestine.
• Products of digestion can be used to make new carbohydrates, proteins & lipids. Some of glucose used in respiration.
• Bile - produced in liver & stored in gall bladder before release into small intestine. HCl in stomach makes pH too acidic for enzymes in small intestines to work properly. Bile - alkaline - neutralises acid & makes conditions alkaine, which enzymes work best in. Also emulsifies fat - gives bigger SA of fat for lipase to work on, making digestion faster.

• Enzymes used in digestive system are produced by specialised cells in glands & in gut lining.
• Digestive System:
  • Salivary glands - produce amylase in saliva.
  • Gullet/Oesophagus
  • Stomach - pummels food with muscular walls. Produces pepsin. Produces HCl to kill bacteria & to give right pH for pepsin to work - pH 2 - acidic.
  • Liver - bile produced here.
  • Gall bladder - where bile is stored.
  • Pancreas - produces protease, amylase & lipase & releases them into small intestine.
  • Small intestine - produces all 3 digestive enzymes to complete digestion. Where food is absorbed out of digestive system into blood.
  • Large intestine - where excess water is absorbed from food.
  • Rectum - where faeces are stored before leaving body through anus.

• Red blood cells - carry O2 from lungs to all cells in body. Biconcave disc shape - large SA for absorbing O2. No nucleus - more room to carry O2. Contain red pigment - haemoglobin. In lungs haemoglobin binds to O2 - oxyhaemoglobin. Body tissues - reverse - oxyhaemoglobin splits up into haemoglobin & O2 to release O2 to cells.
• White blood cells - defend against infection. Some change shape to gobble up unwelcome microorganisms - phagocytosis. Others produce antibodies to fight microorganisms + antitoxins to neutralise toxins produced by microorganisms. Have nucleus.
• Platelets - small fragments of cells. No nucleus. Help blood clot wound to stop blood pouring out & to stop microorganisms entering. Lack of them leads to excessive bleeding & bruising.
• Plasma - liquid that carries everything in blood: red & white blood cells, platelets, nutrients - glucose, amino acids, etc., CO2 from organs to lungs, urea from liver to kidneys, hormones, proteins, antibodies & antitoxins.

• Coronary heard disease - when coronary arteries get blocked by layers of fatty material building up. Causes arteries to become narrow - blood flow restricted & there's lack of O2 to heart - results in heart attack.
• Stents - tubes that are inserted in arteries. Keeps them open, ensuring blood can pass.- keeps pearson's heart beating. Lowers risk of heart attack in people with CHD. Effective for long time & surgery recovery time is quick. However, there's risk of complications during surgery - heart attack, etc., and infection risk from surgery. Also risk of patients developing blood clot near stent - thrombosis.
• Too much LDL cholesterol can cause fatty depostits to form inside arteries - leads to CHD.
• Statins - drugs that reduce amount of LDL cholesterol in blood. Slows rate of fatty deposits forming.
• Advantages: Reduces risk of strokes, CHD & heart attacks. Increases amount of beneficial HDL cholesteral in blood - can remove LDL from blood. Studies also suggest they may help prevent other diseases. Disavantages: Long-term drug that must be taken regularly - can forget. Can cause negative side effects - headaches, etc. Some can be serious - kidney failure, liver damage, etc. Effect of statins are't instant.

• Artificial hearts - used if donor organ not available or if not best option. They are mechanical devices that pump blood. Usually temporary fix. Less likely to be rejected by body's immune system than a donor heart - made from metals or plastics - body doesn't recognise them as foreign & attack them like it does with living tissue. Surgery to fit heart can lead to bleeding & infection. They don't work as well as natural ones - parts of heart could wear out or electric motor could fail. Blood doesn't flow through as smoothly - blood clots and leads to strokes. Patient has to take drugs to thin blood, which can cause bleeding problems in accident.
• Valves in heart can be damaged/weakened by heart attacks, infection or old age. May cause valve tissues to stiffen - won't open properly. Valve may become leaky - blood flows in both directions - poor blood circulation. Can replace valves - from humans or other mammals - biological valves. Man-made - mechanical valves. Less drastic than heart transplant but still is major surgery & blood clots can be problem.
• Artificial blood - blood substitute used to replace lost volume of blood in accident. Safe if no air bubbles get in & can keep people alive even if 2/3 of blood is lost. May give patient time to produce new blood cells. If not - blood transfusion.

• Health - State of physical & mental wellbeing.
• Communicable diseases - spread between people & animals. Caused by bacteria, viruses, parasites, fungi, etc.
• Non-communicable diseases - cannot spread. Generally last long and slowly get worse. E.g. Asthma, cancer, CHD...
• Diseases - interact & cause other physical & mental health issues: People with immue system problems have increased chance of suffering from communicable diseases - body less likely to be able to defend itself against pathogen. Some types of cancer can be triggered by infection by viruses - infection with some types of hepatitis virus can cause long-term liver infections - leads to increased chance of developing liver cancer. Also HPV infection can cause cervical cancer in women. Immune system reactions in body caused by infection by pathogen can trigger allergic reactions - skin rashes, or worse asthma symtoms. Mental health issues - depression - can be triggered when someone is suffering from severe physical health problems.
• Other factors affect health: whether you have good balanced diet. Stress you are under. Your life situation - access to medicines, access to things to prevent you getting ill.

• Risk factors often aspects of one's lifestyle, or presence of certain substances in environment, or substances in body.
• Many non-communicable diseases caused by different risk factors interacting.
• Lifestyle factors - different impacts locally, nationally & globally - developed countries - non-communicable diseases more common - people - higher income - buy high-fat food. Individual choices affect local incidence of disease.
• Some risk factors directly cause disease: Smoking - cardiovascular disease, lung disease/cancer. Damages walls of arteries & cells in lung lining. Obesity - type 2 diabetes - body less sensitive of resistant to insulin - struggles to control glucose concentration in blood. Excess alcohol - liver disease, affects brain function - damages nerve cells - brain loses volume. Smoking & alcohol whilst pregnant - health problems for unborn baby. Cancer caused by exposure to certain substances or radiation. Things that cause cancer - carcinogens - e.g. ionising radiation.
• Non-communicable diseases - costly - millions die anually. People with diseases - lower life quality or shorter lifespan. Expensive for health services/organisations to research & treat. Families may have to move or adapt home to help family member - costly. If family member has to give up work or dies, family income reduced and economy is affected.

• Cancer caused by uncontrolled cell growth & division - result of cell mutation. Causes tumour:
  • Benign: Tumour grows until there's no room. Doesn't invade other tissues in body and stays usually within a membrane. Isn't normally dangererous, & tumour isn't cancerous.
  • Malignant:Tumour grows & spreads to healthy tissues. Cells can break off & spread to other body parts via bloodstream. Malignant cells invade healthy tissues & form secondary tumour. Are dangerous & fatal - they're cancers.
• Survival rates increased - improved treatment, being able to diagnose it earlier & increased screening for it.
• Risk factors increase risk of developing cancer: Smoking - lung cancer. Can cause other types - mouth, bowel, stomach & cervical. Obesity - bowel, liver, kidney, etc. Second biggest preventable cancer cause after smoking. UV exposure - skin cancer. Living in sunny climates, spending lots of time outside & frequently using sun beds increase risk. Viralinfection - infection with hepatitis B and C - liver cancer. Sometimes depends on lifestyle for viral infections - unprotected sex, sharing needles.
• Can inherit faulty genes making you more susecptible to cancer - mutations in BRCA genes - increased likelihood of developing breast & ovarian cancer.

• Plants made of organs - stems, roots, leaves, etc. Made of tissues. Examples: Epidermal tissue - covers whole plant. Palisade mesophyll tissue - part of leaf where most photosynthesis occurs. Spongy mesophyll tissue - in leaf. Contains big air spaces - gases can diffuse in & out of cells. Xylem & Phloem - transport water, mineral ions, food, etc. around plant. Meristem tissue - found at growing tips of shoots & roots & able to differentiate.
• Epidermal tissues - covered with waxy cuticle - helps reduce water loss by evaporation.
• Upper epidermis - transparent - light can pass through to palisade layer.
• Palisade layer - lots of chloroplasts - near top of leaf - more light.
• Xylem & Phloem form network of vascular bundles, delivering water & other nutrients to leaf & takes glucose from photosynthesis. Also help support structure.
• Lower epidermis - full of stomata - lets CO2 diffuse directly into leaf. Opening & closing of stomata controlled by guard cells.
• Air spaces in spongy mesophyll increase rate of gas diffusion.

• Phloem Tubes - made of columns of elongated cells with small pores in end walls to allow cell sap through. Transports food substances made in leaves to rest of plant for immediate use. Transport in both directions. Process is translocation.
• Xylem Tubes - made of dead cells joined end to end with no end walls between and a hole down middle. Strengthened with lignin. Carry water & mineral ions from roots to stem & leaves. Process is transpiration stream.
• Transpiration - loss of water from plant. Caused by the evaporation & diffusion of water from plant's surface. Most happens at leaves. Evaporation creates slight shortage of water in leaf - more drawn up from rest of plant through xylem vessels. Means more water is drawn up from roots - constant transpiration stream through plant. Transpiration side-effect of way leaves are adapted for photosynthesis. Leaves need stomata and as there's more water in plant than in air outside, water escapes from leaves through stomata by diffusion.

• Transpiration rate affected by 4 main things:
  • Light intensity - brighter - greater transpiration rate. Stomata begin to close as it gets dark. Photosynthesis can't happen in dark, so don't need to be open. When stomata closed, little water can escape.
  • Temp. - warmer - faster transpiration. Water particles - more energy to evaporate & diffuse out of stomata.
  • Air flow - better - greater transpiration rate. If air flow around leaf is poor - water vapour just surrounds leaf & doesn't move away - higher concentration of water particles outside lead as well as inside - diffusion doesn't happen as quickly. Good air flow - water vapour swept away - low concentration of water in air outside leaf. Diffusion happens quickly.
  • Humidity - drier the air around leaf - faster transpiration. Humid - lots of water in air - little difference between inside & outside of leaf - slower diffusion.
• Guard cells adapted to open & close stomata. Have kidney shape which opens & closes stomata. When plant has lots of water, guard cells fill & go plump & turgid - makes stomata open - gases exchanged for photosynthesis. Short of water - guard cells lose water & become flaccid, making stomata close. Helps stop too much water vapour escaping. Thin outer walls & thickened inner walls make opening & closing work. Are also sensitive to light & close at night to save water. Most found on undersides of leaves - lower surface shaded & cooler - less water lost.