B5 revision notes

Skeleton function

Support Protection Framework for muscle attachment to allow movement

Types of skeleton

Internal External

External

- e.g. spiders, insects, crabs

External skeleton made of chitin, is protective supportive and allows for muscle attachment. External skeleton does not grow, so animal has to shed it as it grows and form a new one.

Internal

Found in fish, birds, reptiles, amphibians, mammals.

Some fish e.g. sharks, dogfish, there skeleton is made entirely out of cartilage and not bone.

Bones and cartilage

Both of these are living tissue with blood vessels and nerves. Bones are moves when the muscles that are attached to them contract and relax.

Bone growth (H)

Embryos have skeletons made of cartilage (this is mainly protein). From 6 weeks growing in the womb, minerals (mainly calcium phosphate) are

deposited into the cartilage, and the bone hardens (ossification). Children have more cartilage at the ends of their bones than adults as they are still

growing (forensic scientists use the amount of cartilage still present to tell the age of a dead person).

Bones and cartilage can be infected by pathogens.

Structure of the long bone

Ends of the bones are covered in smooth cartilage to reduce friction when bones move

The bone is hollow to it is light, but the hard outer layer is hard so the bone is still strong.

In the centre of the bone is marrow and blood vessel. Fat is stored and new blood cells are made here.

Bones fractures (breaks)

Green stick- bone is bent. Often occurs in children with rickets (soft bones due to lack of vitamin D and calcium in their diet)

Simple fracture- bone is broken but does not stick out through the skin Compound fracture- this is an open fracture where the broken bone sticks through

the skin.

Old people with osteoporosis (soft bones) are at greater risk of fractures.

Muscles and joints

Bones cannot move without the muscles attached to them contracting or relaxing. Tendons attach muscles to bone Ligaments attached bone to bone

Moving the arm

Bending the arm- the bicep contracts pulling the radius bone upwards and the triceps relaxes

Straightening the arm- the triceps contracts pulling the ulna downwards and the biceps relaxes

Levers (H)

The hinge joint is like a lever

Elbow is the pivot (fulcrum) Muscles have to exert a greater force than the load for the bone to move The hand moves a greater distance than the muscles

Joints

Bones in skeleton could not move without joint

Types of joint

Fixed- in the skull which are fused together (babies have a cartilage patch on top so skull can be squeezed to fit through birth canal.

Hinge- at elbows and knees, and movement only in one plane (back or forwards)- is a synovial joint

Ball and socket- hips and shoulders, can rotate bones in many directions- is a synovial joint

(H) Synovial joints

Freely moving joints are also called synovial joints

Features

Moving ends covered in cartilage (stops friction) Joint is enclosed in a capsule Capsule lined with a membrane that secretes synovial fluid (lubricates the joint)

The circulatory system

Organisms such a single –celled amoeba do not need a circulatory system as they have a large SA/volume ratio, so substances can easy diffuse into it.

As organisms become multicellular their SA/vol ratio decreases (their volume is larger as is filled with many cells), and they need a circulatory system to transport substances to the cells.

Types of circulatory system

Open- found in insects. Blood does not travel in blood vessels but bathes the cells.

Closed – vertebrates. Blood travels in blood vessels (arteries, veins and capillaries).

Closed can be single or a double closed circulatory system

Single- e.g. fish. Two chambered heart and blood only goes through once. It goes from the Heart gills body.

Double- e.g. humans. Four chambered heart and blood goes through it twice as there are two circuits (circuit from heart to lungs and back, and circuit from heart to body and back).

(H) History of the circulatory system

• In 2nd Century, Galen, a Roman physician (doctor) of Greek origin dissected monkeys and pigs and found blood in the veins was a darker colour compared to the arteries.

He thought the liver made the blood and pumped it through the veins to the organs- he was wrong of course! His ideas influenced medicine for 1000 years.

16th Century, Leonardo da Vinci studied anatomy and made drawings of how blood passed through the chambers, and how the heart valves worked.

In 17th Century, Dr William Harvey published a book on how blood circulates in the body i.e. a double circulatory system. He linked the pulse in the arteries to contraction of the left ventricle. He discovered that veins had valves to prevent blood back flow. He predicted that there were capillaries but as he did not have a microscope he did not see them.

The cardiac cycle

LORD- left oxygenated, right deoxygenated

• The heart is made of powerful cardiac muscle which receives a continuous supply of glucose, fatty acids, and oxygen from the coronary arteries, which allows the cardiac muscles cells to respire aerobically, generating energy for contraction.

• Blood goes into the atria, the atria contract and forces blood into the ventricles. The ventricles contract and forces blood into arteries that take blood around the body.

• When ventricles contract, blood goes away from the heart in arteries under high pressure.

• Arteries divide into more arterioles, and these arterioles into even more capillaries (high total cross-sectional area).

• This means that the circulatory system is becoming ever more branching and so the time it gets into the many capillaries, blood pressure is low.

A=aorta

Art= arteries

C=capillaries

V= venuoles

Ven= veins

• The rate of blood flow is very low in the capillaries to allow exchange of substances between the blood and the cells.

• Veins have wide lumens (holes running through them), and so blood pressure is low. Due to this low blood pressure and as blood is sometimes returning to the heart against gravity, veins have valves which shut when the heart relaxes, and keeps the blood moving in one direction.

• Key Fact- left ventricle wall is made of thicker muscle than the right ventricle wall. The left ventricle wall is thick as the muscle has to contact hard enough to force blood out of it and around the whole body, while the right side has to contract and push blood only as far as the lungs.

• Key fact -The pulse is a measure of heart rate. When the ventricles contact and push blood into the arteries, the arteries which have elastic walls, expand and recoil (open wider and the narrow again). This can be felt where vessels are near the skin.

The cardiac cycle

• Diastole- the heart relaxes and the atria fill with blood.

• Atrial systole- the atria contract and force blood into the ventricles

• Ventricular systole- ventricles contract and force blood into the arteries

Control of the cardiac cycle

• The pacemaker- Sinoatrial node (SAN) is a patch of specialised tissue that produces electrical impulses, which spreads across the walls of the atria causing them to contract (atrial systole).

• This contraction causes increased pressure inside the atria forces blood through opened atrioventricular valves into the ventricles.

• When the electrical impulses have spread across the atria, a patch of muscle fibres called the atrioventricular node (AVN), conducts these impulses along Purkyne fibres to the tip of the ventricles, causing them to contract (ventricular systole).

• This contraction increases pressure inside the ventricles, which forces the atrioventricular valves shut (this stops back flow of blood into the atria).

• Blood forces open semi-lunar valves in the arteries.

• The heart relaxes (diastole) and the atria fill with blood, and the cardiac cycle starts again. Each cycle is one heart beat

• Electrical activity of the heart can be recorded and a trace recorded called an electrocardiogram (ECG)

Artificial pacemakers and heart repairs

Artificial pacemakers- Our natural pacemakers can detect when a person is more active and send out more electrical signals to make the heart beat faster.

If people have an irregular heartbeat, they can have a pacemaker which is implanted just under the skin with a wire passed from it into a vein and into the right atrium. These artificial pacemakers need replacing every 10 years.

Hole in the heart- Fetuses have a small hole between the right and left atrium and blood does not need to go to the lungs. At birth, this hole closes so that blood from the right side of the heart has to go to the lungs for oxygenation. In some people this hole does not close properly which means that less oxygenated blood gets to the body tissue, leaving a person tired and breathless. This hole can sometimes be repaired with surgery.

Damaged heart valves- as people age, their heart valves may become stiff, not close properly and allow the backflow of blood. These faulty valves can be replaced with

valves from pugs or cows, or with artificial ones (no chance of rejection and no blood supply to valves).

Blocked coronary vessels- Coronary vessels provide a blood supply for the heart muscle, but they can become blocked (eating too much saturated fat and smoking). If these narrowed arteries get blocked heart attack (or angina- pain in chest which goes down the arms). Bypass surgery can correct this where are vein is used to bypass the blockage.

Heart transplant- heart replaced with a healthy donor heart. Big operation, where people have to take anti-rejection drugs for life.

Considerations- There is a shortage of donor hearts and replacements of faulty parts such as valves is less traumatic and no risk of rejection.

Donor cards- opt in is where you sign up to say you would be willing to donate, and opt out is where it is assumed you will donate unless you sign up to say otherwise (religious reasons e.g. Jehovah’s Witnesses).

Blood donation

History-

1818.Blundell- first successful blood transfusion 1840- first blood transfusion in a haemophiliac 1901- discovery of blood groups which meant safer transfusions

Anti-coagulants- we naturally have in blood in case we have a cut. We need vitamin K (from green veg) for clotting (K for Klotting). Put into blood bags to stop blood clotting.

Abnormal clotting- haemophilia is inherited and blood does not clot well. Drugs such as warfarin, aspirin and heparin are given to stroke and heart attack patients to break down clots.

Blood groups-

Red blood cells have proteins on their surface called agglutinins. Blood has antibodies that will react against agglutinins (but obviously not your own).

Group O- universal donors as have no agglutinins for other groups antibodies to react against.

Group AB- universal recipients as have no antibodies against any agglutinins.

Group A and B cannot receive each others blood as they have antibodies that will react against their agglutinins.

Rhesus factor- people not only have different group of blood but either have a rhesus factor (a D protein) or not e.g. group O rhesus positive, or group O rhesus negative. People with rhesus negative blood cannot receive rhesus positive blood as they make antibodies against the D protein.

Gas exchange

First forms of life on Earth (3.5 billion years ago) were bacteria which obtained there energy by chemical reactions. Some bacteria developed the ability to photosynthesis and release oxygen, which killed some anaerobic bacteria. Those that survived have resulted in life forms evolving to respire aerobically.

Single celled organisms- their gas exchange can be by diffusion as they have a large surface area to volume ratio.

Multicellular organisms- as an organism has more cells (more volume) its surface area to volume ratio decreases and so organisms cannot rely on diffusion for gas exchange. However earthworms are long and thin so have a large surface area, and together with a permeable skin, so gas exchange can occur by diffusion.

Amphibians- gas exchange across the skin, via simple lungs, and from the floor of their mouth. Water loss prevent in frogs by them secreting mucus.

Fish- have a single circulatory system and gas exchange occurs in gills

Blood flows from heart to the gill filaments (large surface area), which have a good blood supply. The fish gulps in water, raises the floor of its mouth, which forces water containing oxygen over the gills, where gas exchange occurs. Oxygenated blood then flows from the gills to the body.

Oxygen consumption of active fish greater than resting fish as more respiration occurring in cells to provide energy. As temperature is warming, less gas is dissolved in the water (fish have a need for a higher volume of water over their gills). Extrapolated lines show that around 50 degrees Celsius the oxygen consumption of the fish would exceed the ability of water at that temperature to supply sufficient oxygen.

The human respiratory system

Ventilation= breathing in and out of air

Lungs= gas exchange surface

Inspiration (breathing in) Expiration (breathing out)• Intercostal muscles contract and

pull the ribs up and out• Diaphragm flattens• Volume inside chest and lungs

increases• Air pressure decreases inside the

lungs, air is at a higher pressure outside the body and so moves into the lungs

• Intercostal muscles relax and the rib cage moves down and in

• Volume inside the chest decreases• Air pressure inside the lungs

increases, the alveoli which are elastic recoil to normal size, and these both forces air to the outside.

• Some air stays in the lungs to stop the alveoli closing. This air is called residual air

Spirometer

Measures lung function

Tidal volume= volume breathed in and out at rest

Vital capacity= max you can breathe in + tidal volume+ max you can breathe out

Residual air= volume air left in lungs when you breathe out fully

Lung capacity= vital capacity + residual volume

Safety= sterile mouth piece each time, stop is patient feels unwell

This diagram shows a surface view of the left lung, nd a section through the right lung showing the airways and air sacs inside.

The alveoli

Oxygen diffuses through alveolar walls into blood, and carbon diffuses from blood into alveoli. Oxygen dissolves in a film of water that lines the alveoli and then moves through the alveolar walls.

Adaptations of alveoli for diffusion-

Thin walls Permeable Good blood supply Large surface area

Diseases of the respiratory system

To prevent dirt and microbes causes lung infections

Hairs up nose Ciliated cells and mucus producing cells lining trachea and bronchi, to trap dust and

microbes and sweep to back of throat for swallowing (acid in stomach kills microbes).

White blood cells called macrophages patrols lung tissue and ingests (eats) anything foreign.

If pathogens not removed from lungs- could get lung infection

Disease cause symptomsbronchitis Virus, bacteria, breathing in

smokeCough, sore throat, wheezing

asbestosis Occupational disease- breathing in asbestos fibres

Inflammation and scarring of alveoli. Difficulty breathing, could lead to cancer

Cystic fibrosis Inherited disease Mucus that is too thick is produced, so cilia cannot waft microbes to throat chest infections lungs eventually damaged

Lung cancer Tar from cigarettes Cells lining bronchioles keep dividing and form a tumour prolonged cough , with blood

Asthma Triggered by allergens e.g. Wheezing, tight chest due

pollen, exercise to muscles in bronchioles contracting build-up of fluid

Digestion

We need to digest large insoluble substances into small, soluble ones that can travel around the body in the blood

Physical digestion- breaking food up with teeth, and muscular churning of stomach

Chemical digestion- breaking food up with enzymes

Food Type of enzyme Part of gut where works

Products of digestion

Carbohydrates carbohydrases Mouth and small intestine

Starchmaltoseglucose

Fats (lipids) lipases Small intestine Fatty acids and glycerolProteins proteases Stomach and

small intestineAmino acids

Enzymes work best at a particular pH. Protease in stomach is adapted to low pH, and acid needed in stomach to kills microbes.

Bile- made by liver, stored in gall bladder, and enters small intestine via bile duct. Emulsifies fats into small droplets for easier digestion (larger surface area).

Villi in the stomach-

Finger-like projections that line the small intestine and it is through these digested food is absorbed from the small intestine into the blood.

Adaptations

Large surface area Thin walls Good blood supply

Large intestine- water and minerals are absorbed back into blood supply here. What is left is faeces and is passed out of the body- egestion

Excretion

Main organs-

Skin Lungs Liver Kidneys

Skin-

Makes sweat that cools body down. Also gets rid of excess salts and water

Lungs- gets rid of excess carbon dioxide which would make blood too acidic and denature enzymes. Increased carbon dioxide levels are detected by brain and it stimulates the increase in breathing rate to get rid of the excess.

Liver – breaks down old red blood cells (makes bile and also passes out in faeces). Liver breaks down hormones, medicines, ad alcohol. If you eat too much protein, the liver breaks down excess amino acids into ammonia (harmful), and ammonia is reacted with carbon dioxide to produce urea which is taken to kidneys for excretion.

Kidneys –

Kidneys filter out salts, water, urea, and glucose from blood. Glucose, some salts and water are reabsorbed.

Nephron-

Kidneys consist of millions of filtering units called nephrons. Blood enters kidneys from the afferent arteriole, and this becomes a knot of capillaries (the glomerulus). Blood goes through the glomerulus under high pressure, and small substances are filtered through into the Bowman’s capsule. In the first part of the nephron, all the useful substances such as glucose, hormones, vitamins etc. are reabsorbed (called selective reabsorption).

The Loop of Henle is where water and salts are regulated. ADH (anti-diuretic hormone) is released from the pituitary gland in the brain, into

the blood and travels to the kidney where is brings about the reabsorption of water from the Loop of Henle back into the blood.

When the blood is dilute, less ADH is released and so less water is absorbed resulting in lots of dilute urine. When there is less water in the blood, more ADH is released, more water is absorbed back into blood, and less urine is produced and it is concentrated.

The female reproductive system and its functions

Renal dialysis- for people who kidneys are not working properly and their blood is filtered by a machine.

Growth and development

Primary sexual characteristics- external genitals which determine whether you are a girl or a boy

Sex hormones cause secondary sexual characteristics

male female Voice deepens Hair grows on face and body Body becomes more muscular Genitals develop Testes start making sperm

Breasts develop Pubic hair and under arm hair grows Hips widen Periods start

Menstrual cycle

Several hormones coordinate menstrual cycle

Hormone What it doesFSH Produced by pituitary gland in brain, and causes an egg in ovaries to

mature. Also stimulates the ovaries to make oestrogenLH Triggers the release of an egg (ovulation)Oestrogen Stimulates the pituitary gland to produce LH. Inhibits further

production of FSH and repairs uterus lining (endometrium)Progesterone Maintains the lining of the uterus and inhibits LH

Fertility and fetal screening

Hormones can be used to reduce and decrease fertility

Reducing fertility- if women take a contraceptive pill containing the hormones oestrogen and progesterone, ovulation is prevented as they mimic pregnancy. At high levels these hormones inhibit FSH and LH from the pituitary gland and so eggs cannot develop and are not released.

First contraceptive pill had high levels of oestrogen which prevented ovulation but had high levels of side effects.

Increasing fertility-

Infertility could be due to blocked fallopian tubes, testes not producing enough sperm, eggs not developing or not being released from the ovaries.

Fertility treatment- IVF (in-vitro fertilisation)

Women inject with FSH to produce eggs Eggs collected and mixed in petri dish with sperm (or sperm are injected into eggs) Fertilised eggs develop into embryos and two and inserted into uterus.

Treatment Description and reason for treatmentArtificial insemination Where male sperm count low, or lesbian couple want a child,

donor sperm in inserted into a vaginaEgg donation Eggs are donated to another woman who cannot make own eggsSurrogacy Embryo produced by IVF is implanted into the uterus of another

woman (surrogate mother). When the baby is born, the baby is given to the biological mother

Ovary transplants Ovary transplanted is from identical twin to her sister. May need an ovary transplant due to early menopause or ovaries having been removed due to cancer treatment.

Checking fetal development

Ultrasounds – check fetal development but cannot detect all abnormalities.

Amniocentesis- small amount of amniotic fluid is removed from around the baby and contains fetal cells and the baby can be checked for Down’s syndrome etc.

Growth

At birth and during first 6 months- growth is monitored by measuring head circumference, body length, and mass. If baby grows too slowly the pituitary gland may not be producing enough growth hormone, and child may be treated with injections with growth hormone.

Stages of human growth

Infancy First 2 years and is when the highest rate of growth occursChildhood 2-11 years

Growth is slower than infancyAdolescence 11-15 years

Puberty beginsGrowth spurts (girls 10-12 years), boys (12-15 years)

Maturity Males continue to grow up to 18-20 yearsFemales reach adult height 16 years

Old age 60-65 yearsPhysical abilities deteriorate

Final height is determined by genes, diet, amount of exercise, hormones, health and disease.

Life expectancy has increased in developed countries due to less industrial disease, healthier diets, better housing, vaccination, better treatments for cancer and heart disease. More old people means that more medical treatment needed, will be less jobs for younger people, pension age will need to be changed as people living too long after retiring.

New parts for old

External replacements (replace organ function outside the body- heart-lung machines (used in heart surgery), kidney dialysis machines (clean blood of people with kidney failure), mechanical ventilators (cause gas exchange).

Internal mechanical devices- heart pacemakers, artificial knee and hip joints, artificial hearts, eye lenses.

Internal mechanical devices need to be designed so that they are small enough to fit in, last a while before a battery needs replacing, body does not react with the materials it is made from, and it is strong (e.g. titanium in joints).

Organ transplants

Blood transfusions Blood is removed from live donors and stored in blood banks until it is needed

Cornea transplants Removed from the eye of a dead person and transplanted into another person’s eye. No risk of rejection as no blood vessel

Heart transplant Donors are dead unless someone receives a heart and lung transplant at the same time, and their own healthy heart can be donated to someone else.

Lung transplants From dead donor to e.g. someone with cystic fibrosisKidney transplants Donor can be dead or alive as close relative can donate one

kidneyBone marrow transplant Used to treat leukaemia. Donors can donate their matched

bone marrow to someone who has leukaemia