HB2 Flashcards
(153 cards)
1
Q
What is biodiversity?
A
The number, variety and variability of living organisms on the planet.
2
Q
What is extinction?
A
The loss of a species.
3
Q
What is evolution?
A
The process by which new species are formed from pre-existing one over very long periods of time.
4
Q
What is adaptive radiation?
A
The emergence of several new species from a common ancestor introduced into an environment.
- Species colonises an area with several riches.
- Ancestor evolves into several new species each of which is adapted to feed on a different resource
5
Q
How does biodiversity vary?
A
Biodiversity is lowest around the poles (not many species) and is highest around the tropics. (at the equator it isn’t very diverse)
6
Q
What is a species?
A
A group of organisms that can interbreed to produce offspring.
7
Q
What are the reasons for endangered species?
A
- Loss of habitat
- Overhunting from humans
- Competition from introduced species
- Deforestation
- Pollution
- Drainage of wastelands
8
Q
What is a mass extinction followed by?
A
A rapid diversification. (such as the asteroid hitting the earth - dinosaurs extinct)
9
Q
Why should humans conserve?
A
- Humans depend on other species
- Food: wild species act as a gene pool, we could introduce these genes through cross breeding or genetic engineering to improve productivity.
- Aesthetic: we get pleasure from interacting with other species (pets, national parks etc.)
10
Q
What is the process of natural selection?
A
- More offspring are produced that can be sustained.
- Competition for resources (food, habitat)
- Individuals with a beneficial variation in the population survive and reproduce
- Next generation therefore have been passed on these favourable characteristics and this then repeats.
- May lead to 2 different groups, significantly different enough to prevent breeding and therefore 2 different species.
11
Q
What is classification?
A
Naming and organising of organisms into groups according to evolutionary relationships.
12
Q
What is taxonomy?
A
Study of the principles behind classification.
13
Q
Why do we classify?
A
- Make the study of organisms more manageable
- Support our ideas of evolution
- To allow scientists to communicate with each other.
14
Q
How do we classify?
A
The modern classification system is called a phylogenetic hierarchy using a phylogenetic tree.
15
Q
What is a hierarchy?
A
A large group of organisms split into smaller and smaller groups (downward)
16
Q
What does phylogenetic mean?
A
The way the organisms are grouped in the hierarchy reflects how the group of organisms are related.
17
Q
What is a taxon?
A
A group of organisms sharing basic features.
Each taxon is a level in the classification hierarchy.
18
Q
What is the order of the classification hierarchy going from the largest to smallest groups and give an example of the human order.
A
- Kingdom (Anamalia)
- Phylum (Chordata)
- Class (Mammalia)
- Order (Primates)
- Family (Homindae)
- Genus (Homo)
- Species (sapiens)
19
Q
How do taxonomists group organisms?
A
Similarities and differences.
Similar morphology or biochemical methods
20
Q
How is similar morphology carried out?
A
Homologous structures - body parts that are structurally similar even if used for different functions (suggests shared ancestry and divergent evolution)
21
Q
How are biological methods carried out?
A
Comparing certain molecules across different species to see how similar/dissimilar their structures are.
DNA comparison is often used.
Protein comparison is also used (similar amino acids in the cytochrome C)
22
Q
How is the binomial system used?
A
Each species is given a name which uses the genus and the name of its species. The genus uses capitals whilst the species doesn’t. Allows a particular organism to have its own name but we can also see similarities between two species.
e.g. Homo erectus and Homo sapiens
23
Q
Describe all 5 kingdoms.
A
Prokaryotae - Don’t have any internal cell membranes, ER, mitochondria, true nucleus or Golgi body. Has a cell wall made of murein. Bacteria and blue-green algae are examples.
Protoctista - eukaryotic organisms with membrane bound organelles and a true nucleus. Includes algae and slime moulds.
Fungi - body is made up of threads called hyphae which make a mycelium. Cell wall made of chitin. Feeding is heterotopic. Reproduce by spores that lack flagella. Includes yeast and mushrooms.
Plants - Feeding is phototrophic. Multicellular. Cell wall made of cellulose. Include flowers, mosses, ferns etc.
Animals - Heterotrophic feeding, no cell wall, show nervous coordination.
24
Q
What does chordate mean?
A
Typically has a vertebral column/backbone (vertebrates) whilst non-chordate don’t (invertebrates).
Animal kingdom divided into these 2 categories.
25
What is the development of human evolution?
- Homo habilis: found 1.5-2.5 million years ago. Hunted using stone tools. Cranial volume was 750-800cm cubed.
- Homo erectus: found 0.5-0.6 million years ago. Used fire and lived in big groups. Cranial volume was 850cm cubed.
(- Homo neanderthalensis: diverse descendants of H. erectus that had larger brains than humans. Found 130,000 to 35,000 years ago. Stockier, with less prominent jaw, used wide range of tools and lived in shelter and hunted for wild animals. Lived in communities)
- Homo sapiens: Found since 300,000 years ago. Hunter gatherers and bury their dead. Cranial volume is 1350cm cubed.
26
What the 2 main theories as to how H. sapiens evolved?
1. Multiregional theory (directly evolved from different parts of the world.
2 Monogenesis/'Out of Africa' (only African descendants of H. erectus gave rise to modern humans. Other regional descendants became extinct with out contributing to the gene pool. Humans spread from Africa less than 100,000 years ago.
27
Explain the reasons as to why the monogenesis/'Out of Africa' explanation for human evolution is the favoured explanation.
Most famous fossils of H. sapiens were found in caves in France around 35000 years ago. Fully modern fossils of H. sapiens were found in Africa from around 100,000 years ago. Neanderthal fossils were also found near, suggesting that the two species coexisted.
The two species didn't interbreed and couldn't be ancestors of the area.
Neanderthal DNA was very different to the modern human (can't be fully trusted however).
28
How do we work out common ancestry using genetic techniques?
- DNA: base pairs compared, more alike means the more close the organisms are.
- Amino Acids: The more similar the amino acid sequence the more closely related the species.
- Protein: responding to different antigens on proteins (antibodies respond to corresponding antigens creating a precipitate) the greater the degree of precipitate the closer the evolutionary relationship.
29
What four main functions does the human gut do?
1: Ingestion: taking I of food into the body through the mouth
2: Digestion: breakdown of large food molecules into simple soluble molecules by enzymes. Mechanical digestion takes place with teeth, and then rhythmical contractions of the gut. Digestive enzymes secreted.
3: Absorption: Passage of digested food through the gut wall into the blood.
4: Egestion: elimination from the body of food that can't be digested (eg. cellulose)
30
How is food propelled through the gut?
Peristalsis - circular muscle of gut contracts behind the bolus and relaxes after wave of contraction has passed
31
What is the structure of the human gut?
- Outer serosa: consists of a layer of tough connective tissue that protects the wall of the gut and reduces friction from other organs.
- (Outer) longitudinal muscle and (inner) circular muscle which cause muscular contractions to produce peristalsis.
- Sub-mucosa: connective tissue (cont. blood and lymph vessels) to take away absorbed food products. Nerves coordinate peristalsis.
- Mucosa: Secretes mucus which lubricates and protects mucosa. Either secretes digestive juices or absorbs digested food.
- Lumen: cavity of gut, where bolus is.
32
What are the glands in the gut?
1. Glands outside of the gut which secrete through tubes or ducts into the lumen.
- Salivary glands (mouth)
- Liver (bile into duodenum)
- Pancreas (pancreatic juice into duodenum)
2. Glands in form of cells in sub-mucosa eg. secrete mucus in the duodenum.
3. Glands in from of cells in mucosa eg.
- Gastric glands in stomach wall, secretes gastric juice into stomach
- Glands in base of villus inn SI, secretes enzymes into small intestine.
33
What happens during digestion?
Large molecules are broken down into smaller products by enzymes.
- Carbohydrates broken down by amylase from a starch into a disaccharide and then maltase breaks this down into monosaccharaides.
- Proteins are broken down by endopeptidase which break the peptide bonds within the molecule and exopeptidase break the peptide bonds at the end of these shorter polypeptides. Creates amino acids.
- Lipids are broken down by lipase into fatty acids and glycerol.
34
What occurs in the first step of digestion?
1: MOUTH - Mechanical digestion occurs and food is broken down by teeth. The food is mixed with saliva which is secreted by salivary glands. This lubricates the bolus, maintains a pH of slightly alkaline in mouth and this is the optimum pH for the salivary enzyme amylase which breaks starch into maltose.
Bolus is swallowed (lubricated by mucus in saliva) and travels down the oesophagus.
35
What occurs in the second step of digestion?
2: STOMACH - food enters the stomach and is kept there by contraction of 2 muscle rings (one at entrance and one at duodenum exit). Contractions mix up food with gastric juices. This has a pH of 2 which kills most bacteria and is optimum pH for the enzymes. Also contains peptidase which hydrolyses the proteins to polypeptides.
The stomach wall contains gastric glands with peptic cells, oxyntic cells and goblet cells.
36
What do peptic, oxyntic and goblet cells do?
- Peptic cells (chief) secrete pepsin as pepsinogen which prevents enzyme from damaging the stomach tissues. Remains inactive until it reaches lumen of stomach where it is activated by HCl and then pepsin breaks down proteins. Doesn't damage stomach wall due to mucus.
- Oxyntic Cells secrete HCl which makes stomach acidic which kills bacteria and activates protein-digesting enzymes.
- Goblet Cells secrete mucus which forms a protective layer on stomach wall, preventing pepsin and HCl from breaking down the gastric mucosa. Helps movement.
37
What occurs in the third step of digestion?
3: DUODENUM - made up of two regions; the duodenum and the ileum. Relaxation at base of stomach lets food in little by little to the duodenum.
- Bile is produced in the liver and stored in the gall bladder and then passes into the duodenum via the bile duct. This emulsifies lipids so that they have a larger surface area. Also neutralises acidity in stomach.
- Pancreatic juice is secreted form exocrine glands in the pancreas and enter the duodenum via the pancreatic duct. Contains endopeptidase, amylase and lipase.
The walls of duodenum have Brunner's Glands which secrete alkaline juice and mucus. The alkaline juice keeps the optimum pH for enzymes and the mucus lubricates.
Enzymes are secreted by cells at the bottom of crypts of Lieberkuhn:
- Maltase breaks down maltose into 2 glucoses
- Sucrase breaks down sucrose into glucose and fructose
- Endopeptidase and exopeptidase breaks down polypeptides into amino acids.
- Dipeptidase breaks down dipeptides into amino acids.
Disaccharides and dipeptides are digested intracellularly into simple amino acids and monosaccharaides.
38
What happens in the process of absorption?
The ileum is well adapted for digestion as it as very long and has folds called villi which increase surface area, and on these are microvilli, also called a brush border, which further increases surface area for absorption.
ATP energy required so epithelial cells in ileum contain a lot of mitochondria.
- Glucose and amino acids are absorbed across epithelium of villi via diffusion and active transport. They pass into capillary network that is in each villus. Glucose diffuses into blood down a concentration gradient.
- Fatty acids and glycerol are passed into lacteal of villi from the epithelium.. This is a blindly ending lymph capillary in centre of the villus. They are then transported to lymphatic system which opens into the blood at the thoracic duct.
39
What occurs in the large intestine?
Divided into caecum, colon an the rectum. Water and mineral salts are absorbed by the colon. By the time it reaches the rectum, indigestible food is in semi-solid state (residues of cellulose, bacteria and sloughed cells) and is ejected as faeces. Called defecation.
40
What is the fate of digested products after absorption?
- Glucose is absorbed by cells from blood for energy release in respiration.
- Amino acids are absorbed by protein synthesis, any not would be deaminated and converted to urea.
- Lipids are used for membranes and hormones, excess stored as fat.
41
Describe cancer of the digestive system?
Cancer can occur in various areas of digestive system such as stomach, liver, pancreas, bowel.
Symptoms depend of site and extent of growth as well as tissue of origin. May be bleeding, disruption of function of the organ, rapid weight loss or blood in faeces (bowel cancer).
Can be treated with chemotherapy, radiotherapy and surgical removal to remove tumours.
Risk of cancer can be reduced y eating a healthy, balanced diet that is high in fibre, fruit and vegetables and is low in meat and saturated fat. GO VEG.
42
Describe Coeliac Disease
Caused by a protein called gluten found in wheat, rye and barley. Upon exposure an enzyme modifies the protein and the immune system reacts with the bowel tissue causing an inflammatory reaction. Leads to flattening of villi and this interferes with digestion.
Symptoms can be mild with lethargy to severe such as acute illness and weight loss. Avoided when on a life-long gluten free diet.
43
Describe diverticulosis/diverticulitis
Diverticulosis is when a small pouch in the colon bulge outwards through weak spots. Symptoms include mild cramps, bloating and constipation.
Diverticulitis is when these pouches become infected or inflamed. Symptoms are more severe, such as abdominal pain, nausea, vomiting, chills, cramping and constipation. Can lead to blockage, tearing, bleeding etc.
Caused by low fibre diet and is treated with a diet high in fibre. Diverticulitis can e treated with a course of antibiotics.
44
Describe a peptic ulcer.
A peptic ulcer is the erosion of the lining of the stomach wall. There is an increase in production of aid OR mucus lining is damaged.
Two major causes are bacteria H. pylori or long term use of medicines such as anti-flam drugs or aspirin.
Common symptoms are stomach pains made worse by eating, weight loss, nausea and vomiting.
Treatment involves a combination of: medicine to clear body of H. pylori, drugs to reduce stomach acid and drugs to protect stomach lining.
45
Why antigens may red blood cells carry?
A, B and Rhesus antigens.
46
What is agglutination?
Agglutination (otherwise known as clumping) occurs when an antibody and an antigen match (eg. A antigen with anti-A antibody). This creates a clump of antibodies.
47
Describe Anaemia.
Red blood cells made in the stem cells or bone marrow mature and the cell gets rid of the nucleus in order to make more room for haemoglobin. This the haem group.
In order to have this, iron minerals and vitamin B are required. If haemoglobin isn't produced the body may be short of oxygen in tissues/organs.
Symptoms are: lethargy, shortness of breath, paleness and heart palpitations BUT they can progress to headaches, hair loss and ulcers.
People at high risk are menstruating women, pregnant of breastfeeding women, premature babies, vegetarians, people with cancer, athletes, people on fad diets and children going through puberty.
Common causes are: dietary deficiency (iron), failure of absorption, excessive bleeding (heavy periods, inner body injuries)
Can be diagnosed when a RBC count is significantly lower than 5.2mil cells in men or 4.8mil in women.
Treatment includes iron tablets, iron rich diet or a blood transfusion.
48
What is the 1st line of defence for immunity?
The physical barrier to the body to stop pathogens getting through.
- SKIN: the skin has a layer of healthy bacteria that fight any pathogens, as well as being tough to friction and many harms. If the skin is cut then a clot forms which dries to form a scab, preventing loss of blood and entry of pathogens. New cells grow underneath. (formed by fibrin fibres tangling to create a mesh.
- STOMACH: acid produced in stomach has a low enough pH to kill most bacteria that enters via food.
- MUCUS: any bacteria that enters the nose is caught in the mucus and is wafted down the oesophagus where it is swallowed into the stomach and killed or coughed out.
49
What is the 2nd line of defence for immunity?
The second line (Inflammation response/non-specific) is activated when the tissue is damaged (cut, graze, burn, scratch etc).
When the tissue is damaged the injury goes past the epidermis into the dermis. Pathogens enter the body.
Mast cells and basophils stimulate histamine release.
When histamine is released it dilates blood cells (increased blood flow), extra heat (slows down pathogen growth), capillaries more permeable for tissue fluid, blood capillaries more permeable to white blood cells, and attracts white blood cells to damaged tissue.
These white blood cells (neutrophils and macrophages) engulf pathogens through phagocytosis and once this has been completed eosinophil breaks down the histamine.
50
What are symptoms of histamine release?
- Pain
- Redness (increased blood flow)
- Itchy
- Swelling (dilated cells)
- Heat
51
What is the humoral immune response?
Immature B-Cells from the stem cells in the bone marrow divide via mitosis.
The B Cells mature and produce antibody receptors which embed in the cell membrane. There are many different B cells which respond to different antigens.
- Antigens in the cell membrane of the macrophage are recognised by B lymphocytes.
- B lymphocytes are triggered when specific binding sites on their surface membrane attach to antigens.
- Activated cells divide rapidly forming clones of plasma cells in lymph node. Most produce antibodies but some produce memory cells.
- These circulate and bind to the specific antigen and destroy it. Plasma cells are responsible for immediate defence against infection.
- Memory cells remember the antigen and are ready to go under immediate production to create antibodies.
52
What is the cell mediated response?
T Cells produced in the thymus gland mature since the child is being weaned. T lymphocytes leave the thymus when mature and circulate in blood and bodily fluids.
- macrophages engulf pathogens and present the antigens on their own membranes.
- binding sites on the surface of specific t lymphocytes recognise and fit the antigen
- t lymphocytes are triggered are multiply rapidly by mitosis.
- t killer cells destroy the antigen directly
- helper t cells activate B cells to initiate antibody response.
- t suppressor cells suppress other cells immune system
- memory cells remember the antigen and produce an even larger cone for rapid destruction of the antigen if it comes again.
53
What is an antigen?
a substance that triggers the formation of antibodies or reacts with them
can be non-self (foreign) or self-antigens
normally large complex molecules
54
What is an antibody?
glycoproteins that are in a group called immunoglobulins
made up of 2 heavy chains and 2 light chains. has an antigen binding site which is specific, so there is a variable at the top of each antibody. has a hinge region in the middle
55
What is natural active immunity?
exposed to infection and the body manufactures its own antibodies in response to the antigens on the infectious agent.
if the same agent is encountered again it can be eliminated before disease
56
What is natural passive immunity?
transfer of antibodies from mother to foetus across placenta. only temporary as there are no memory cells formed.
57
What is artificial active immunity?
vaccination. vaccine is injected into a healthy individual. antibody production is stimulated and memory cells are also formed so that immunity is gained to that disease
58
What is artificial passive immunity?
injection of ready made antibodies, no memory cells, only temporary.
useful against diseases that are difficult to immune such as tetanus.
59
What does a vaccination process look like?
```
Phase A (no curve) - primary latent period where the antigen is detected by B lymphocytes. divides rapidly to form a clone of plasma cells (most memory cells)
Phase B (small curved peak) - primary response period where antibody conc increases before decreasing again
Phase C (large curved peak) - secondary response if the antigen is reintroduced or persists. lower level of antigen triggers the response (shorter latent phase) larger clone.
```
60
How does HIV occur?
transmitted through blood/semen and enters through cuts in skin or needles contaminated. may have no other symptoms other than swollen lymph glands.
can remain latent for years before being activated. reduces helper T cells which means it reduces body's ability to fight a disease.
symptoms include cancer (no killer T cells), weight loss, fever, diarrhoea and deteriorating brain function. pneumonia is often reason of death.
Stage 1: HIV positive with little/no symptoms
Stage 2: some symptoms, low helper T count (therefore killer T too)
Stage 3: clinical AIDS, symptoms appear
61
What is airborne transmission?
(droplet infection) mainly diseases of lungs and respiratory passages.
microorganisms are expelled in tin droplets of saliva/mucus through coughing, sneezing and breathing
whooping cough, TB, influenza and measles are spread this way.
62
What is transmission through food and water?
can be contaminated with bacteria if sanitation and hygiene are poor.
salmonella spread in undercooked meat or infected animals
cholera and typhoid spread through contamination of water by untreated faeces
63
What is a vector?
an aid that helps spread a disease, such as female mosquitos for Plasmodium which causes malaria.
64
What is the difference between an endemic and an epidemic?
```
endemic = low levels in one area
epidemic = significant increase in number of cases and spread
```
65
What is a carrier?
person who shows no symptoms when infected but can pass the disease on to another individual
66
What is the cause, symptoms, prevention and treatment of salmonella?
gram-negative, rod-shaped bacterium.
Cause - found in animal intestines and may be transferred to meat in slaughter, multiplies during storage. undercooking. pork, poultry, eggs and unpasteurised milk
Symptoms - diarrhoea and vomiting, nausea (affects gut lining)
Prevention - thorough cooking, seperation of cooked and undercooked meat, storage in cool conditions, no cross-contamination
Treatment - antibiotics only used if essential to prevent build up of resistance. vaccine not available as over 2000 types. runs its own course (lasts about a week)
67
What is the cause, symptoms, prevention and treatment of cholera?
Vibro cholerae gram-negative bacterium.
- Cause - contaminated water and food by faeces by individuals who have the disease. humans can act as a reservoir. spread as vibrios
- Symptoms - watery diarrhoea, leading to severe dehydration and maybe death. (affects gut lining)
- Prevention - hygienic disposal of faeces, safe drinking water, education about hygiene (washing hands etc) hygienic preparation of food. vaccination gives some protection bu tonly 40-80% and is lost after 3-6 months
- Treatment - re-hydration salts and non contaminated fluids (orally or in severe cases infused in vein). antibiotics can be used however they are expensive and may result in resistance
68
What is the cause, symptoms, prevention and treatment of Tuberculosis?
infectious bacterial disease
- Cause: droplet/airborne infection, close conditions, poverty (coughing)
- Symptoms: coughing up blood, weight loss, night sweats, fever, chest pain. attacks lungs and lymph nodes mainly
- Prevention: vaccination called BCG. before Heaf Test is done: 6 point needle injects protein extracted from bacterium. redness/swelling means infected/immune, no reaction means not immune. if reaction they are screened for matter in lungs to see if infected. if not then vaccine given to children under high risk.
- Treatment: DOTS (direct observed treatment short-course). makes sure patient finishes course of drugs so resistance avoided
69
What is the cause, symptoms, prevention and treatment of Influenza?
Virus made of single RNA strand coated in protein and surrounded by an outer lipoprotein coat.
- Cause: droplet infection (coughing/sneezing) more likely in crowd/poorly ventilated places.
- Symptoms: headache, sore throat, fever, rise of temp, shivering. infects lining of upper respiratory tract. death can be caused by bacteria infecting causing bronchitis/pneumonia
- Prevention: quarantine/good hygiene
- Treatment: antibiotics don't work for viruses. rest, aspirin and fluids good. vaccines available to protect vulnerable
70
What is the cause, life cycle and symptoms of Malaria?
- caused by plasmodium (protoctist) that infects liver and red blood cells. carried from one person to another by female mosquito (vector). life cycle of plasmodium takes place in human body. mosquito takes parasite and discharges saliva and takes up blood. once in body they multiply rapidly in liver cells, which then bursts to infect RBC. a mosquito then takes up infected blood and passes it
- toxins from cells causes fevers, chills and headaches. these appear one to two weeks after being bitten. fatality can happen within days of symptoms occurring
71
What are the ways of preventing malaria?
1. preventing mosquito from biting human: hanging nets with insecticide on around bed, wearing protective clothing, using insect repellents
2. eliminating the vector (mosquito): draining swamps where mosquito lays eggs and larvae develop -very expensive and impossible to drain all, spraying breeding grounds with diesel oil, spraying insecticides on pond surfaces to kill larvae, using fish/bacteria/sterilisation to biologically control
3. attacking the parasite: difficult as parasite is usually inside body cells. limited effect. drugs reduces chance of infection, vaccines difficult to develop due to parasite mutation
72
What is a broad spectrum antibiotic?
antibiotics that are effective against wide range of pathogenic bacteria. prevent against widespread microbial processes such as protein synthesis.
eg. tetracycline
73
What is a narrow spectrum antibiotic?
antibiotics that effective against a limited range of pathogens. affect more specific processes such as cell wall formation
eg. penicillin
74
What is the Gram stain test?
distinguishes between 2 different groups of bacteria (G positive/G negative) due to differences in cell wall.
- Gram positive: lack lipopolysaccharide in wall meaning they retain crystal violet. harmed more by antibiotics than G negative. penicillin works well by inhibiting enzyme for cross linking, takes up more water and bursts, killing bacteria.
- Gram negative: have chemically complex walls where inner layer of murein is surrounded by lipopolysaccharide and don't retain dyes like crystal violet (red). resistant to penicillin. acted upon by broad spectrum antibiotics that inhibit protein synthesis of bacteria.
75
What is antibiotic resistance?
many bacteria that used to be susceptible have now become resistant. due to mutations which are rare but due to rapid replication they occur often, which after passed on.
76
What is a head louse and how has it adapted to stay alive?
Ectoparasite that feeds on blood and can live for short periods away from the body.
Can't be passed to or caught from animals.
Small and wingless with a short life cycle but reproduces rapidly with numbers to nits which are laid glued to base of hairs.
Has pincers/claws that allow it to grasp onto fine hairs and walks from head to head.
Symptoms are itching of scalp.
Insecticides available as lotions and creams are effective.
77
What is a blood fluke and how has it adapted to stay alive?
specialised parasitic flatworms that live in blood vessels supplying intestine/bladder.
cause disease schistosomiasis/bilharzia, a widespread disease.
disease has low mortality rate but sufferers become weakened by enlargement of spleen and liver and intestinal damage and bleeding.
one symptom is anaemia
the parasite is transferred in freshwater where a snail host releases infective larval forms of the parasite which penetrate the skin when washing or fishing.
these larvae enter the vein and pass through body moving to lungs and liver through the blood stream. they then leave liver and pass through to the intestine/bladder where they feed on blood cells and produce a lot of eggs. these eggs are passed out of body and infect snail.
drugs are an effective treatment.
78
What is a roundworm and how has it adapted to stay alive?
most common human worm infection (common in tropical and sub-tropical areas where sanitation is poor).
lives in small intestine and can grow up to 40cm long
symptoms aren't noticeable if infection is light but children can have slower growth/weight gain. heavy infection can cause abdominal pain and may cause blockage of intestine
can lay 200,000 eggs per day which are passed out of the body. people can become infected by touching mouth with hands are being contaminated. eggs are ingested and hatch in intestine where they can penetrate lining and travel to the the lungs where they can be coughed up and swallowed.
drugs are effective treatment.
79
What is a pork tapeworm and what is its life cycle?
can be up to 10M long and lives in the small intestine
has a head of suckers and hooks and body of segments
has 2 hosts: primary is the human and the secondary is the pig. pig becomes infected if it feeds in drainage channels contaminated with human faeces. human becomes infected if eaten undercooked infected pork as infected cysts grow in the muscle
80
What are the problems of gut conditions and adaptions a pork tapeworm has to overcome these?
- lives in digestive juices/mucus which has extreme conditions of pH. has a thick cuticle and inhibitory substances to prevent digestion
- food is in constant motion due to peristaltic movement and churning. suckers and hooks allow it to attach to gut wall
- immune system of host. body covering protects from this.
- death of the host results in death of parasite.
- has simple excretory and nervous system as well as simple digestive system to digest food.
- no organs of movement as it doesn't need to move
- large surface area
81
How is a maximum rate of diffusion reached in a respiratory surface?
- sufficiently large surface relative to the volume or the organism
- be thin so that diffusion paths are short
- be permeable to allow respiratory gases through
- be moist to allow a medium in which gases can dissolve
82
What is the problem associated with an increase of size of organism?
In large organisms which are multi cellular, the smaller the surface area is to the volume and diffusion is too slow due to the surface being insufficient.
83
What does the human respiratory system consist of?
Lungs consist of network of tubes called bronchioles coming from 2 bronchi. Alveoli on the end of these.
Lungs enclosed in airtight thorax, at which at the bottom there is a diaphragm (a muscle).
Supported by the rib cage which is moved by intercostal muscles.
84
How are the alveoli suited for gas exchange?
Provides large surface area as there are many in the body.
Have thin walls so there is a short diffusion path.
Each alveolus covered with network of capillaries to maintain diffusion gradients.
85
How does gas exchange occur in alveoli?
Oxygen diffuses out of alveoli into the blood in the capillary.
Carbon dioxide diffuses out of the capillary into the air in the alveoli.
86
Which cells help with gas exchange?
Epithelial cells - remove particles from the air before it reaches the lungs.
2 types - goblet and ciliated
- cilia are tiny extensions of cytoplasm that found on free surface
- goblet cells secrete mucus
87
How do the cells remove particles in gas exchange?
when particles in air such as dust, bacteria an pollen are breathed in they are trapped in mucus from the goblet cells.
cilia sweeps the mucus upwards to back of throat where mucus can be swallowed and particles don't reach lungs.
88
What are the steps inhalation?
1. External intercostal muscles contract
2. Ribs are pulled upwards and outwards
3. Diaphragm muscles contract, flattening
4. 2+3 increase volume of thorax
5. Increase of volume reduces pressure in lungs
6. Atmospheric pressure greater than lungs so air is forced into the lungs.
Exhalation would be the opposite
89
How do mammals ventilate their lungs?
Negative pressure breathing - forcing air down into their lungs.
90
How is surfactant used in lungs?
Pleural fluid comes from pleural membranes which is a cavity that surrounds each lung.
This acts as a lubricant which allows for friction-free movement against inner wall of the thorax. However this can cause alveoli to collapse.
TO PREVENT THIS an anti-ticking chemical called a surfactant covers the alveoli and reduces surface tension from the fluid.
91
Why is artificial surfactant used?
Premature babies undergo respiratory distress syndrome where the immature lungs don't produce surfactant. This reduces the amount of time the infant will spend in a ventilator.
92
How is a spirometer used to measure lung capacity?
Has a air-filled chamber of 6dm capacity suspended over water. The lid/float is arranged so it can fall and rise as th subject breathes.
Pen connected to lid moves against rotating chart to show rises and falls. KYMOGRAPH
Soda lime is used to absorb the carbon dioxide before it goes back into the chamber.
93
How is the spirometer made sure it is safe?
Nose clip and mouthpiece sanitised between uses.
| Soda lime used to make sure oxygen being inhaled.
94
What is tidal volume?
The volume of air that is being exchanged at rest (usually around 0.5dm)
95
What is vital capacity?
Total volume of air that can be expired after a maximum inspiration (usually goes up to 5dm)
96
What is residual volume?
The volume of air that remains in the lungs (usually around 1.5dm)
97
How can ventilation rate be calculated?
tidal volume x number of breaths per minute
98
What happens in asthma?
Spasms in smooth muscles of walls in bronchioles which cause the passageways to close partially.
Means more effort is needed to deliver sufficient air to the lungs.
Usually mucus membranes that line respiratory passageways become irritated and secrete excessive amounts which may clog bronchi/oles.
99
Who is prone to asthma and what may cause it?
Common in children and affects 1 in 20 of the population.
| Common causes may be air pollution and allergens including dust mites, animal fur and feathers, pollen.
100
What treats asthma?
Drugs in aerosol form (inhaler) prescribed as inhalant. Rapid relief as they cause smooth muscle to relax and widens the airways.
Steroids can reduce inflammation of bronchioles.
101
What happens in emphysema?
Alveoli lose their elasticity and remain filled with air during expiration.
Walls of alveoli break down over time and may merge to form larger sacs with reduced volume.
Lungs may become permanently inflated and little gas exchange can occur due to damage.
102
What are the symptoms of emphysema and what may cause it?
Symptoms: breathlessness/shortage of oxygen. can worsen so that patient is disabled.
Air pollution, industrial dust and cigarette smoke are the most common irritants for long term irritation.
Cigarette smoke also prevents repair as well as damaging the protein for preventing emphysema.
103
What treats emphysema?
Can't be treated or reversed.
| Can be minimised by not smoking or giving up.
104
What is COPD and what does it come from?
Chronic Obstructive Pulmonary Disorder.
condition where airflow of lungs becomes more obstructed.
This happens to everybody gradually but becomes worse when smoking.
Most people that die from it smoke.
105
What does tar from cigarettes do in the lungs?
Goblet cells in epithelium of air passages are stimulated to over produce mucus.
Ciliated cells are destroyed and don't work.
Means a build up of mucus in bronchial passages which can't be wafted away and means a breeding ground for bacteria and viruses.
Chronic bronchitis.
106
How is lung cancer caused from smoking?
Tar collects in lungs as tobacco smoke cools.
Contains mix of toxic chemicals, some carcinogens. They affect cell division resulting in mass of unorganised tissue known as a tumour. When this grows it displaces other tissues and blocks airways/other parts of lungs. May break away and form tumours in other parts of body.
107
What does nicotine from cigarettes do to the body?
Substance that makes tobacco addictive.
Nicotine stimulates release of adrenaline into blood stream, which is used for fight or flight response (raises blood pressure/heart rate)
Long term smokers develop raised blood pressure which can lead to problems like atherosclerosis, strokes and coronary heart disease.
108
What does carbon monoxide fro cigarettes do to the body?
Haemoglobin combines more readily with CO than oxygen.
Reduces amount of oxygen in blood and therefore heart has to work harder to supply blood with oxygen.
Short term= unable to take part effectively in physical activity
Long term = leads to hardening of the arteries, especially coronary artery.
109
What are the features and function of red blood cells?
Erythrocytes.
Contains haemoglobin which helps transport oxygen from lungs to respiring tissue.
Biconcave in shape which increases surface area enabling oxygen to diffuse quicker.
No nucleus meaning there is more room for haemoglobin, maximising oxygen carried.
110
What are the features and function of white blood cells.
Leucocytes.
Larger and contain nucleus. Can be spherical or irregular in shape.
Two main groups: granulocytes and agranulocytes.
111
What are granulocytes and what do they do?
Also called macrophages/phagocytes.
Have granular cytoplasm and lobed nuclei.
Neutrophil and eisonophil engulf different species whilst basophil releases histamine.
112
What are agranulocytes and what do they do?
Also called lymphocytes/monocytes.
Monocytes become macrophages to engulf bacteria.
Lymphocytes can either be B or T and aid in the 2 specific immunities.
113
What is in the plasma of the blood and what does it help with?
Made up of 90% water.
Helps transport food soluble molecules, waste products, plasma proteins, mineral ions, vitamins, CO2, antibodies etc. so therefore has these in as well in the SERUM.
Distributes heat.
Fibrinogen in plasma is involved in blood clotting.
114
What do platelets do?
Help with blood clotting which prevent over bleeding.
115
What happens when a body rejects blood?
It has antigens in which it recognises as non-self and clumps in agglutination of cells which can block blood vessels and can be fatal.
116
Sum up blood grouping.
4 groups: A, B, AB and O.
A = has A antigens and anti-B antibodies.
B = has B antigens and anti-A antibodies.
AB = has A and B antigens and no anti-X antibodies
O = has no antigens and both anti-A and anti-B antibodies
117
What types of blood do the blood groups accept or reject?
```
A = can receive A and O. Rejects B and AB
B = can receive B and O. Rejects A and AB
AB = can receive A, B, AB and O.
O = can receive O. Rejects A, B and AB
```
AB is universal recipient (take from anyone)
O is universal donor (give to anyone)
118
What is the Rhesus factor?
Another antigen that can be present on cell membrane. Called Rhesus, and people with it are Rhesus + (or antigen D positive)
Rh+ can receive Rh- blood.
The rhesus antigen stabilises the membrane.
119
What is sensitisation in terms of the Rhesus factor?
If Rh+ given to Rh- person then they can develop antibodies against Rhesus antigens.
An Rh- mum can carry an Rh+ baby and they don't mix until the placenta breaks down where the babies blood pass into the mothers blood and mother starts to develop antibodies.
If the mother has a second baby which is Rh+ then antibodies pass into the foetal circulation which destroys RBC of baby and it may develop haemolytic disease.
Mothers can be given anti rhesus globulin to prevent this.
120
What type of circulatory system does a mammal have?
Double circulatory system which means blood passes twice through the body for each complete circuit.
Made of pulmonary circuit - right side where heart pumps deoxygenated blood to the lungs, and the systemic circuit - left side where oxygenated blood is carried to the tissues
121
What are arteries and veins made up from?
Innermost layer = endothelium which is one cell thick and reduces friction
Middle = tunica media made of elastic fibres and smooth muscle. thicker in arteries to accommodate pressure change.
Outer = tunica externa. made of collagen fibres which are resistant to over stretching.
Lumen in the middle.
122
What do arteries do and what is their structure like?
Carries blood away from the heart.
Have thick muscular walls to withstand high pressure of blood received from the heart.
Contractions help maintain pressure as it is further away from the heart.
Gets smaller into arterioles and then capillaries which penetrates all tissues and organs of the body to supply blood.
123
What do veins do and what is their structure like?
Carries blood to the heart.
Have semi-lunar valves to prevent back flow.
The capillaries in tissues and organs collect deoxygenated blood and turns into venules which widen into veins.
124
What do capillaries do and what is their structure like?
Thin walled consisting of only endothelium and are therefore permeable to water and dissolved substances.
Exchange of materials takes place here.
Have small diameter so friction of walls slows the blood. May capillaries meaning a large cross sectional area.
125
What does myogenic mean?
Relaxes and contracts of its own accord throughout a person's life due to cardiac muscle - heart is myogenic.
126
What is the cycle of blood through the circulatory system.
Comes up through major/inferior vena cava and into right atrium. Goes though atrio-ventricular vein into right ventricle. Pumped out of pulmonary artery through a semi-lunar valve to the lungs.
Oxygenated blood comes back to heart through pulmonary veins into the left atrium, and goes through atrio-ventricular vein into the left ventricle. Pumped out of the aorta through a semi lunar valve to the rest of body.
127
What happens in the cardiac cycle?
Atrial systole - right and left ventricles relax, atrioventricular valves open as atria contract and blood flows into ventricles.
Ventricular systole - atria relax and ventricles contract forcing blood out of hearts into aorta and pulmonary arteries. Semi-lunar valves open and atrioventricular valves close.
Diastole - ventricles relax and pressure in ventricles fall. Causes semilunar valves to shut preventing back flow into ventricles. Blood enters into atria to begin again.
128
What are the pressure changed of the heart?
Left ventricle - contracts so pressure increases largely (large curve) Ventricles begin to relax so pressure decreases. Small pressure increase where blood flows into ventricle.
Aorta - pressure never drops low and constantly containing blood and pumping it out. Rise when the semi-lunar valves open and falls when they close.
Right ventricle - smaller contraction so less pressure and much lower curve but follows same pattern and left.
Atrial - drops quickly due to relaxing and Av valves close. blood flowing in means a slow increase of pressure and when the AV valves open the pressure drops again.
129
How does the heart beat?
Electrical stimulation occurs and the sinoatrial node (specialised cardiac fibres) which spreads over the 2 atria causing them to contract at the same time. This is prevented from spreading to ventricles by connective tissue.
Reaches atrioventricular node which is in the middle of the 2 atria and passes a wave of excitation to the specialised tissues in the ventricles.
Excitation passes down the Bundle of His in the septum to the apex of the heart. Bundle branches into purkinje fibres which carry the excitation wave up the ventricle muscle.This causes ventricle to contract from apex upwards pushing blood upward.
130
How does one measure pulse rate?
Ventricular systole causes wave of blood through arteries meaning it creates a bulge in the walls of arteries and the recoil can be felt as a pulse.
Can be felt when it passes over a bone such as the underside of the wrist or the neck. One pulse = one heartbeat.
Normal is from 60-100, around 70 for healthy young adult.
Fitter people have lower as the same amount of blood can be pumped in fewer pumps from the heart.
131
How is blood pressure measured?
Two pressures taken - highest in left ventricle (systolic) and lowest in aorta (diastolic).
Measured using a sphygmomanometer.
Healthy is around 120/75.
If higher the person if suffering from hypertension or high blood pressure. Increased risk of strokes and heart attacks.
Factors such as diet, stress and smoking increases resistance of blood flow and increases blood pressure.
132
What is an atheroma?
A fat deposit built up form cholesterol in blood causes lumen to become narrower and lessens elasticity of the artery wall. Increases resistance to blood flow.
Condition called atherosclerosis and can happen in coronary artery which can cause angina (pain)
133
What can atherosclerosis induce?
risk of blood clots in artery. if in coronary artery this can cause coronary thrombosis and can stop blood from flowing to the heart an may cause it to stop beating - heart attack.
Can be prevented from healthy diet, exercise, avoiding stress and not smoking.
134
How is an electrocardiogram taken?
Electrodes attached to persons chest and electrical activity is displayed as an electrocardiograph.
P wave corresponds to atrial contraction, QRS wave comes immediately before contraction of vesicles and T wave represents relaxation of ventricles.
135
How can electrical impulses be summarised on electrocardiographs?
SAN impulse - atrial wall contracts - P wave
AVN impulse - delay
Purkinje fibres - ventricle contracts from base - QRS wave
................. - ventricles relax - T wave
136
What are the 3 forms of arrhythmia?
- Ventricular fibrillation - ECG shows no pattern , contractions are irregular, can lead to heart attack
- Heart block - much longer time interval between P and R as ventricles are beating independently. could be due to damaged Purkinje fibres. pacemaker may be required.
- Atrial fibrillation - atria beat rapidly and in irregular way. may have no symptoms but may have palpitations, fainting and chest pain. disorganised electrical pulses originating in the roots of pulmonary veins. rate control may be achieved by meds
137
How can heart attacks be prevented?
reducing body weight and taking regular exercise. may be helped by changing their diet.
high risk patients take aspirin as it reduces clotting of blood.
138
What is given straight after a heart attack?
Clot bursting drug such as streptokinase is given within the first hour after the attack.
if its severe then surgery might need to be carried out.
139
What is an angioplasty and how is it carried out?
patient given general anaesthetic and a small balloon is threaded into the partially blocked coronary artery through a tube. it is then inflated and the balloon presses against the atheroma, creating tears in it and allowing the lumen to get to usually size. a stent can be used to keep it this size.
140
What is an open heart surgery?
coronary bypass surgery common when coronary arteries are blocked so badly that they insufficient blood can pass through.
piece of aorta artery or vein is taken, usually from the leg and the introduced blood vessel is stitched to the aorta at one end and to a coronary artery at the other.
a heart lung machine is needed to pump blood around the body in the surgery as it can't be done when the heart is beating.
141
What can haemoglobin do in gas exchange?
change its affinity for oxygen in the presence of Co2 by changing its shape, altered shape bind more loosely with oxygen and releases it.
142
What does an oxygen dissociation curve look like?
When haemoglobin is exposed to a gradual increase in oxygen tension it absorbs oxygen rapidly at first but more slowly as the tension continues to rise.
- the more the curve is displaced to the left, the more readily it picks up oxygen, and less readily releases it
- the more the curve is displaced to the right, the less readily it picks up oxygen, and more readily releases it
143
Why does the oxygen dissociation curve look the way it does?
at low conc it is difficult for haemoglobin to absorb oxygen but associates readily.
at high partial pressures of oxygen the percentage saturation of oxygen is very high
RBC load oxygen in the lungs where the partial pressure is high and the haemoglobin becomes saturated with oxygen.
the cells carry the oxygen as oxyhaemoglobin to the respiring tissues eg, muscle, where the partial pressure is low an then it dissociates.
144
What is the Bohr effect?
at higher partial pressure of CO2 the oxygen dissociation curve shifts to the right.
when oxygen reaches respiring tissues the high partial pressure of CO2 enables haemoglobin to unload its oxygen more readily.
145
What is dissociation like in foetal haemoglobin?
blood of the foetus and mother flow closely together in the placenta but rarely mix. to help the foetal haemoglobin absorb oxygen from the maternal haemoglobin in the placenta the foetus has a haemoglobin that differs from adult haemoglobin.
this makes the curve of foetal haemoglobin shift to the left of an adults and it combines with oxygen more readily than maternal - greater affinity.
146
What is myoglobin like in gas exchange?
normally respiring muscle gains oxygen from haemoglobin but if oxygen partial pressure is very low (such as exercising) then oxymyoglobin unloads its oxygen. held as a reserve usually.
myoglobin is more stable and won't release until partial pressure is very low, curve is much more left than haemoglobin.
147
What is the transport of CO2?
transported in 3 ways:
- in plasma solution (5%)
- as hydrogen carbonate (85%)
- with haemoglobin to form carbamino-haemoglobin (10%)
148
What are the steps of the chloride shift?
1. CO2 diffuses into red blood cell and combines with water to form carbonic acid. catalysed by carbonic anhydrase.
2. carbonic acids dissociates into H+ and HCO3- ions. HCO3- diffuse out of RBC into the plasma where they combine with NA+ ions to form sodium hydrogen carbonate
3. H+ ions provide the conditions for oxyhaemoglobin to dissociate into oxygen and haemoglobin.
4. H+ ions buffered by their combination with haemoglobin and the formation of haemoglobonic acid (HHb)
5. oxygen diffuses out of the RBC into tissues
6. to balance ions, Cl- ions diffuse in
149
How are capillaries adapted to allow exchange of materials between blood and cells?
- thin, permeable walls
- provide large surface area
- blood flows slowly allowing time for exchange of materials
150
What is tissue fluid?
fluid that escapes from plasma through capillary walls.
it bathes the cells supplying them with glucose, amino acids, fatty acids, salts and oxygen. also removes waste material from cells.
151
How is tissue fluid obtained?
blood reaches arterial end of capillary and is under pressure from pumping of heart. this hydrostatic pressure forces fluid part of blood out of capillary walls into interstitial space.
hydrostatic pressure greater than osmotic pressure from fluid because the diffusion gradient for solutes favours movement from capillaries to tissue fluid.
152
How does fluid move back into the capillary?
at venous end of the capillary the blood pressure is much lower and water passes back in because osmotic pressure. tissue fluid picks up CO2 and other waste substances. some passes back into capillary, some into lymphatic system where it returned eventually to the venous system and emptied into a vein near the heart.
153
What is Kwashiorkor?
low blood proteins affect capillary filtration and may result in fluid retention in tissues.
diet of many native Africans is cornstarch which doesn't provide enough amino acids.
symptoms are oedema, weakness and retarded growth.
tissue fluid formed faster than being taken up.
seen as protruding stomach.
