B5 - Specification

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An internal skeleton is advantageous compared with an external skeleton:

  • framework of body
  • can grow with body
  • easy to attach muscles
  • flexibility

Cartilage and bone are living tissues and are susceptible to infection but can grow and repair themselves.

In humans, the skeleton starts off as cartilage but is ossified: cartilage is slowly replaced by the addition of calcium and phosphorus (ossification); whether a person is still growing can be determined by the amount of cartilage present.

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Skeletons 2

Structure of a long bone:

  • head with covering of cartilage
  • shaft containing bone marrow with blood vessels

Long bones that are hollow are advantageous because they weigh less and are stronger than solid bones.

Despite being very strong, bones can easily be broken by a sharp knock.

Elderly people are more prone to fractures because they have weaker bones. This is a condition called osteoporosis.

If someone is thought to have a bone fracture it can be dangerous to move them. Movement might make the fracture more serious - for example, it might turn a simple fracture into a compound fracture. Moving someone with a broken back may damage their spinal cord, leading to paralysis.

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Skeletons 3

Synovial Joints: synovial liquid (lubricates and cushions bones during movement), synovial membrane (secretes synovial fluid), cartilage (prevents friction between bones) and ligaments (join to other bones).

A ball and socket allows rotation.

A hinge joint bends only in one direction.

In the arm, the biceps and triceps are the main muscles. They are antagonistic muscles, when one contracts the other relaxes.

1. To bend the arm, the biceps contract and the tricep relaxes.

2. To straighten the arm, the opposite happens.

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Skeletons 4

The arm acts as a lever when it bends or straightens:

  • the elbow joint is the fulcrum or pivot

  • the hand moves through a larger distance than the muscles do

  • the muscles exert a greater force than the load on the hand

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Circulatory System

Animals need a blood circulatory system because diffusion alone is not enough for the efficient transfer of materials.

A single circulatory system is one circuit forom the heart. It has a heart with two chambers. Deoxygenated blood is pumped to the gills and oxygenated blood pumped to the body. (Fish)

A double circulatory system is two circuits from the heart. It has a heart with four chambers. Heart to lungs and back to the heart. Heart to body and back to the heart. (Mammals)

The blood is under a higher pressure in a double circulatory system compared with a single circulatory system. This allows materials to be transported more quickly around the body.

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Circulatory System 2

Galen -2nd Century - discovered the pulse and that the heart is a pump.

William Harvey - 17th century - heart pumped through blood vessels, arterties carried blood under high pressure away from heart and veins had valves to prevent backflow.

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Cardiac Cycle

During each heart beat:

1. The heart relaxes and blood enters both atria from veins. The atrio-ventricular valves open.

2. The atria contract to push blood through the ventricles.

3. The ventricles contract, pushing blood into the arteries. The semi-lunar valves open to allow this whilst the atrio-ventricular valves close.

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Circulatory System 3

The heart rate is linked to activity. During exercise, muscles demand more energy so the heart rate speeds up to supply oxygen and glucose to respiring muscles more efficiently.

The heart contractions are controlled by groups of cells called pacemakers which produce a small electrical current that stimulates muscle contraction.

Artificial pacemakers are now commonly used to control heart beat.

Techniques such as ECG and echocardiograms are used to investigate heart action. ECG (electrocardiogram) used to monitor electrical impulses from the heart. Echocardiograms use ultrasound to produce an image of the beating heart.

Heart rate can be increased by the hormone - adrenaline.

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Circulatory System 4

Pacemaker cells (SAN and AVN) coordinate heart muscle contraction:

  • impulses from the SAN cause the atria to contract and stimulate the AVN
  • impulses from the AVN cause the ventricles to contract.
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Hole in the Heart

Hole in the Heart:

  • blood can move directly form one side of the heart to the other side of the heart
  • less oxygen in the blood
  • can require correction by surgery

A hole in the heart can result in less oxygen in the blood because the deoxygenated blood can mix with the oxygenated blood so the efficiency of transporting oxygen to tissue is reduced.

Unborn babies have a hole in the heart (they do not require a double circulatory system) because they receive oxygen from the mother via the placenta. The hole closes soon after birth so they can have an efficient double circulatory system.

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Consequences of damaged or weak valves in the heart:

  • reduce effective blood circulation
  • can require replacement by artificial valves.

Consequences of a blocked coronary artery:

  • reduces blood flow to the heart muscle
  • can require treatment by by-pass surgery

There are heart assist devices as well as transplants.

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Repairs 2

Advantages of heart pacemaker or artificial heart valves:

  • less risk of rejection
  • involve much less traumatic operation
  • human donor not needed
  • shorter waiting time


  • they may need replacing
  • the patient much take anticoagulants for the rest of their life
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Repairs 3

Advantages of a Heart Transplant:

  • last a lifetime
  • feel better immediately and can lead a full life.


  • expensive, major operation
  • replacement must come from a dead donor
  • long waiting time
  • patient need to take immunosuppressants for the rest of their life
  • chance of rejection
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Repairs 4

Blood donation happens by a donor donating their blood for transfusions. Levels of haemoglobin are checked and then about 500cm3 of blood is removed. This is screened for diseases and if it is safe, it is stored.

Blood transfusion is when the donated blood is warmed and put into a person in an operation or emergecy. Unsuccessful blood transfusions cause agglutination (blood clumping).

Haemophilia is an inherited condition in which the blood cannot easily clot.

Drugs such as warfarin, heparin and aspirin are used to control clotting.

Process of blood cloting:

  • platelets in contact with damaged blood vessels, causing a series of chemical reactions leading to the formation of a mesh of fibrin fibres (clot).
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Repairs 5

The presense of agglutinins in red blood cells and blood serum determines how blood groups react and therefore whether a blood transfusion is successful. A person with blood group A has A-agglutinins. A person with blood group B has B-agglutinins. If they come in contact with the coressponding antigen.


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Respiratory Systems

Methods of gaseous exchange of amphibians and fish restrict them to their habitats:

  • amphibians need moist habitats
  • fish gills only work in water


  • the permeable skin of amphibians makes them susceptible to excessive water loss
  • fish gills work by forcing water through filaments.
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Gas Exchange

During breathing (ventilation), the volume and pressure of the chest cavity are changed by:

  • the intercostals
  • the diaphragm

Tidal air - the volume of air breathed in or out in a normal breath.

Vital Capactiy air - the maximum volume of air that can be used for gas exchange in the lungs - a maximum breath in followed by a maximum breath out.

Residual air - the volume of air that stays in the lungs when we breath out.

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Gas Exchange 2

Gas exchange in an aveoli:

  • Carbon dioxide diffuses from the blood into the aveoli
  • oxygen diffuses from the aveoli into the blood

The aveoli are well adapted to gas exchange:

  • a massive surface area
  • a moist, thin (one cell thick), permeable surface
  • an excellent blood supply
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The respiratory systems protects itself from disease by mucis and ciliated cells in the trachea and bronchi:

  • produce muscus to trap dust and microorganisms
  • lined with millions of cilia which move the mucus from the lungs into the throat

Lung Diseases:

  • with industrial causes - asbestosis - inflammation and scarring limiting gas exchange
  • with genetic causes - cystic fibrosis - too much mucus in the bronchioles
  • caused by lifestyle - lung cancer - cells grow rapidly reducing surface area in the lungs.

The repiratory system is prone to diseases because the lungs are at a dead end.

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Symptoms - difficulty breathing, wheezing and tight chest.

Treatment - inhalers

What happens duing an asthma attack:

  • lining of airways become inflamed
  • fluid builds up in airways
  • muscles around bronchioles contract constricting airways
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Importance of physical digestion:

  • to pass more easily through the digestive system
  • to provide a larger surface area
  • Carbohydrase breaks down starch into sugar
  • Protease breaks down protein into amino acids
  • Lipase breaks down fat into fatty acids and glycerol.

Stomach acid aids protease function.

Bile from the gal bladder helps with fat digestion becauseit emulsifies fat droplets. This means it breaks down large fat droplets into smaller ones with a larger surface area. This enables lipase to work alot faster.

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Digestion 2

The pH of the stomach is maintained at acidic levels, whereas teh pH in the mouth and small intestine is alkaline or neutal. This is because this is the optimum pH for the protease to work in the stomach. Other enzymes in the mouth or small intestine have higher optimum pHs.

The breakdown of starch is a two stage process:

Starch (large polymer)   to   Maltose (double sugar)    to     glucose (simple sugar)

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Digestion 3

Small digested food molecules are absorbed into the blood plasma or lymph in the smal intestine by diffusion. There is a high concentration of food molecules in the small intestine but a lower concentration in the blood. (high to low concentration)

The small intestine is adapted for the efficient absorbtion of food:

  • it has long thin lining
  • it has a large surface area provided by villi and microvilli (finger like projections)
  • it has a permeable surface and rich blood supply.
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Waste Disposal

It is important to maintain a constant concentration of water molecules in the blood plasma because if there is not enough then the body can become dehydrated and the blood is too thick to pump. If theres too much water your blood pressure could go dangerously high.

Renal artery - Dirty blood coming into kidneyRenal vein - clean blood away from kidneyUreter - to bladderMedula - inner region of the kidney - contains the nephronsCortex - outer layer of the kidney

Kidneys work by:

  • filtering the blood at high pressure
  • re-absorbing water and useful substances
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Kidneys Continued

Urea (produced in the liver from excess amino acids) is removed from the blood by the kidneys.

The amount and concentration of urine is affected by:

  • heat - the higher the temperature, the more we sweat. This means that more water is lost so more water is reabsorbed.
  • water intake - more diluted urine because less water is reabsorbed
  • exercise - more sweating and increased water loss. there is less urine and it is more concentrated.
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Kidneys 3

Nephrons are related to the filtration of the blood and formation of urine:

  • a filter unit of glomerulus and capsule - ultrafiltration
  • a region for selective reabsorption - useful substances like glucose are reabsorbed into the blood.
  • a region for salt and water regulation - hairpin of the loop of Henle. Water is reabsorbed into the blood .

Dialysis machine:

Used for patients with kidney failure to remove urea and maintain levels of sodium, water and glucose in the blood. Blood taken from vein and run into machine. Comes into close contact with partially permeable membrane which seprates the blood from the dialysis fluid. The waste diffuses from the blood into the dialysis fluid. The sodium and glucose are replaced in the blood.

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Kidneys 4

ADH increases the permeability of kidney tubules so more water is reabsorbed back into the blood.

ADH production is controlled by negative feedback mechanism.

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Carbon Dioxide Levels

Carbon dioxide must be removed from the body because it is toxic at high levels.

The body responds to increased carbon dioxide levels in the blood by:

  • detecting it by the brain
  • increased breathing rate to remove the excess carbon dioxide
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Role of hormones in the Menstrual Cycle:

  • oestrogen causes the repair of the uterus wall
  • progesterone maintains the uterus wall
  • FSH - follicle stimulating hormone stimulates egg to develop
  • LH - luteinising hormone controls ovulation

FSH and LH are released by the pituitary gland in the brain.

Negative feedback mechanisms affect hormone production in the menstrual cycle. FSH stimulates the ovaries to secrete oestrogen. The oestrogen has a negative feedback effect, reducing FSH release.

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Infertility Treatments

Artificial insemination - sperm placed directly into uterus

Use of FSH - stimulates eggs to ripen and be released

"In viro" fertilisation (IVF) - sperm and eggs are mixed outside of the body. The embryos that grow are transplanted into the uterus.

Egg donation - if doesnt produce eggs, donated by another women and then IVF is used. (can happen with sperm)

Surrogacy - embryo produced by IVF then transplanted into a surrogate mother.

Ovary Transplants - gives women supply of eggs if her own ovaries do not function.

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Infertility Treatments 2

Risks (or disadvantage) and benefits of infertility treatment:

Disadvantage of Egg Donation - carries genes from only one parent.

Risk of Surrogacy - the surrogate mother can get too attached to the baby and may find it hard to give it back to its biological parents.

IVF is expensive and doesnt have a high sucess rate. Twins or triplets are more likely to be produced as more than one embryo is transplanted.

Advantage - if sucessful an infertile couple will ne able to have a healthy baby

Disadvantage - issue with what to do with left over embryos. Many people dont agree with disposing of them. Some may donate them to other couples but others donate them to research with raises more ethical and moral questions.


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Infertility Treatments 3

Foetal Screening can be used to check foetal development and to identify conditions such as Down's syndrome using amniocensis and chromosomal analysis.

This raises ethical issues because some people think that foetal screening offers the unacceptable option of ending an unborn babies life, and that termination is unethical.

Fertility in humans can be controlled by the artificial use of sex hormones: contraceptive pill and fertility drugs.

Fertility can be reduced by the use of femal hormones (contraception) which prevents ovulation by mimicking pregnancy. This inhibits FSH release.

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Extremes of height are usually caused by genes or hormone imbalance.

Diet and exercise can influence growth:

  • Diet - a healthy diet contains protein needed for muscle growth, and calcium and vitamin D for bone growth.
  • Exercise - needed to encourage muscle growth and to make bones dense and hard (strong).

Different parts of a foetus and a baby grow at different rates:

  • The brain and head develop quickly to coordinate the complex human structure and chemical activity

A baby's length, mass and head size are regularly monitored during their first months to provide early warning of any growth problems.

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Growth 2

The human growth hormone is produced by the pituitary gland and it stimulates general growth especially in long bones.

Possible causes of longer life expectancy:

  • less industrial disease
  • healthier diet and life style
  • modern treatments
  • cures for disease
  • better housing
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Growth 3

Consequences of people living longer:

  • elderly people can suffer from degenerative diseases such as artritis and cancer
  • elderly people may find it difficult to live independantly in their own homes
  • trend for small families means pepole will have no-one to look after them
  • low income so difficult to have healthy lifestyle if elderly

These problems reflect on society:

  • hostpitals and care homes must cater for the short term health needs of the elderly, but they also need to consider the residential needs of the increasing population of elderly patients
  • people of the working age will have to work longer and pay higher taxes in order to pay the pensions of older people.
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Organ Donation

Problems with supply of donor organs:

  • shortage of donors
  • tissue match
  • size and age

Problems of mechanical replacements:

  • size
  • power supply
  • materials used
  • body reactions
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Organ Donation 2

Ethical Issues with Organ donation:

  • worry about signing up, could affect family or their body
  • religious believes - dont want to receive or donate

Problems with transplants:

  • rejection
  • immuno-suppressive drug treatment - reduces ability to fight other infections.

Donors can be living if they can live without that specific organ (kidney). Donated organs must be healthy, the right size and age and a good tissue mathc.

Donors can be dead if they can't regain conciousness and can't breathe unaided.

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Organ Donation 3

Advantages and Disadvantages of a Register of Donors:

A - people have more of a choice if they want their organs donated because they have to register themselves.

D - Many people dont register as donors so there is a short supply of donations and the waiting list is long.

The relatives of a person on the Register of Donors don't agree to allow organ donation due to religious beliefs or cultural reasons.

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