Option D: Human Physiology

Question 1

What are the three types of nutrients

Answer 1

• essential
  
  • must be obtained through diet
  • body can’t synthesize it
• non-essential
  
  • can be synthesized in the body
  • can be substituted with another nutrient
• conditionally essential
  
  • essential in one stage of life but non-essential in another
  • due to infancy or a disorder

Question 2

Define a balanced diet

Answer 2

A balanced diet is a diet with the accepted and defined proportions of carbohydrates, fats, proteins, vitamins, minerals, and water necessary for maintaining good health.

Question 3

What are the causes of malnutrition

Answer 3

1. Deficiency of nutrients
2. Imbalance of nutrients
3. Excess of nutrients

Question 4

Define a nutrient

Answer 4

A nutrient is a chemical substance that can be used by the human body.

Question 5

What are the essential nutrient groups and examples

Answer 5

1. Minerals (calcium, magnesium, iron)
   
   1. chemical elements
   2. often in ionic form
   3. needed in trace amounts (i.e. minute quantities)
   4. milligrams or micrograms/day
   5. iodine
      
      1. 150 mcg per day
      2. 1 tsp iodized salt has 400 mcg
      3. used to make thyroxin hormone for thyroid gland
      4. required for metabolism
      5. deficiency of thyroxin — weight gain
      6. excess of thyroxin — weight loss
      7. affects fetal brain development
2. Vitamins (vitamin A, vitamin D, vitamin C)
   
   1. organic compounds
   2. needed in small amounts
   3. function as cofactors — help with enzyme function
   4. may or may not contain an amino group
   5. structure of the vitamin will determine properties
   6. fat soluble — excess can be stored in body
   7. water soluble — excess can be excreted in the urine
3. Amino acids (histidine, tryptophan, etc.)
4. Fatty acids (omega-3, omega-6, etc.)

Question 6

What are fatty acids

Answer 6

• fatty acids can’t be synthesized in the body and thus are essential nutrients
• have many health benefits to cellular and overall health
• alcohol, tobacco, and some other drugs prevent the use of fatty acids for health benefits

Question 7

What happens when there’s an excess of omega-6

Answer 7

Benefits of omega -3 are hindered

Question 8

What is omega-3 fatty acids

Answer 8

• Omega-3 fatty acid helps control blood clotting and building cell membranes in the brain
  
  • Omega-3 is chemically known as alpha-linolenic acid
  • in fatty fish (i.e. salmon), some vegetable oils, brussels sprouts, kale, spinach, walnuts

Question 9

What is Omega-6

Answer 9

• Omega-6 fatty acids lower LDL cholesterol (bad cholesterol), reduce inflammation, and are protective against heart disease
  
  • Omega-6 is chemically known as linoleic acid
  • in safflower, corn, cottonseed, soybean oils

Question 10

What are the nine essential amino acids

Answer 10

• phenylanine
• valine
• threonine
• tryptophan
• methionine
• leucine
• isoleucine
• lysine
• histidine

Question 11

What are the conditionally essential amino acids

Answer 11

• Tyrosine can be synthesised when phenylalanine is in the diet
• Arginine can’t be synthesised by infants, so they need it in their diet

Question 12

What are symptoms of protein deficiency

Answer 12

• protein deficiency is a form of malnutrition, it’s symptoms are fluid retention in the tissues (oedema) and it’s usually visible in the abdominal area (swollen belly)

Question 13

What is arsenic

Answer 13

arsenic is a necessary ultra-trace element for humans. it may possibly inhibit growth.

Question 14

What is iodine

Answer 14

iodine is an important trace element needed for the synthesis of thyroid hormones, which can increase basal metabolic rate, affect protein synthesis, and help regulate long bone growth (in combination with growth hormone) and maturation of neurones. iodine deficiency can result in goitre and severe retardation in children.

Question 15

What are sodium and potassium

Answer 15

sodium and potassium are involved in the propagation of the nerve impulse

Question 16

What are the two types of vitamins

Answer 16

Water-soluble and fat-soluble

Question 17

What are vitamins

Answer 17

vitamins are chemically diverse carbon compounds that can’t be synthesized by the body

Question 18

What happens to excess vitamins

Answer 18

excess water-soluble vitamins will be excreted in the urine. Fat-soluble vitamins can be stored in the body, but can cause problems when taken in excess

Question 19

What are the three main causes of malnutrition

Answer 19

• deficiency (diet lacking in 1+ nutrients)
• imbalance (diet with inadequate intake of a nutrient)
• excess (diet with disproportionate intake of ex.: carbohydrates, fats, or proteins)

Question 20

How is appetite controlled

Answer 20

• appetite is controlled by the appetite control centre in the hypothalamus (ACC)
• control centre regulates desire to eat
• when stomach is empty, ghrelin is released, stimulating appetite
• when food is ingested, the release of peptide PYY 3-36 from the small intestine, insulin from the pancreas, and leptin from the adipose tissue inhibit appetite

Question 21

What are common consequences of an unbalanced diet

Answer 21

type 2 diabetes, coronary heart disease (CHD) which includes hypertension (high blood pressure)

Question 22

What is type 2 diabetes

Answer 22

• type 2 diabetes AKA late-onset diabetes or non-insulin dependent diabetes mellitus (NIDDM) is the most common form of diabetes. the beta cells in the pancreas still produce insulin, but the patients develop insulin resistance, meaning the insulin receptors on the cells are no longer stimulated by insulin. it can increase your chances of developing chd. probable causes:
  
  • high levels of fatty acids in the blood as a result of diets high in fat but low in fibre
  • overweight or obese, associated with a lack of exercise
  • genetic makeup influencing fat metabolism
• symptoms of NIDDM:
  
  • increased glucose levels in the blood and urine
  • frequent need to urinate
  • tiredness and fatigue
  • loss of weight

Question 23

What is hypertension

Answer 23

Hypertension is higher blood pressure than normal. CHD is a disease where plaque builds up in the coronary arteries. These arteries supply blood with oxygen to the heart muscle. correlation between between diets and CHD. higher incidences of CHD and high intake of saturated fatty acids have a correlation. Saturated fatty acids can be deposited inside arteries. If the deposits combine with cholesterol, they can lead to atherosclerosis which leads to hypertension or can cause angina and heart attacks. Hypertension can also cause damage to blood vessels, increasing the risk of developing more atherosclerotic plaques.

Question 24

What happens to the body during starvation

Answer 24

• Most extreme form of malnutrition is starvation, caused by severe reduction in caloric energy intake
• prolonged starvation causes permanent organ damage and death if caloric energy intake isn’t restored in time
• initially, glycogen stores in liver are mobilised, but once depleted, the body has to resort to other sources of energy
• loss of muscle and adipose tissue mass is caused by need for caloric intake to protect vital systems like the nervous system and the heart muscle. body breaks down muscles and lipids to make energy and amino acids. this is known as catabolysis.
• vitamin deficiency is a common result of starvation and can lead to anaemia (B12 deficiency), beriberi (B1 deficiency), pellagra (b3 deficiency) and scurvy (vitamin C deficiency)

Question 25

What is anorexia

Answer 25

Lack of appetite

Question 26

What is anorexia nervosa

Answer 26

eating disorder characterized by food restriction and irrational fear of weight gain. many patients suffering don’t lose their appetites but have a very limited intake of food. often accompanied by unrealistic body self-perception. can lead to excessive weight loss. leads to electrolyte imbalance, skeletal and heart muscle reduction, reduced blood pressure, and a slower heart rate. body might become covered in fine growth of thin hair. can lead to reduced or absent menstrual cycles. can lead to death if extreme.

Question 27

What is vitamin C

Answer 27

• Vitamin C AKA L-ascorbic acid can’t be synthesized by humans and some animals. it’s needed for the production of collagen, a protein found in skin, connective tissues, tendons, and blood vessels. can’t be synthesized by some animals cuz they have a mutation in the GLO gene that codes for an enzyme needed for the last step in the synthesis of L-Ascorbic acid
• vitamin C is:
  
  • vitamin soluble
  • found in many fruits, sour taste
  • used for collagen (skin, blood vessels, muscles, etc.)
  • supports many immune functions

Question 28

What happens with a vitamin C deficiency

Answer 28

• vitamin C deficiency causes scurvy, disease common amongst sailors in past centuries because of a lack of citrus fruits in their diets. citrus fruits are a good source of vitamin C.
• all primates and some smaller monkeys need vitamin C in their diet or get scurvy.
• main symptoms of scurvy:
  
  • bleeding gyms, gingivitis, or loose teeth. vitamin c is necessary for synthesis of collagen which builds and maintains tissue
  • lack of energy. loss of weight and extreme fatigue
  • mood swings or depression
  • chronic joint pain caused by bleeding in the joints
  • suppressed immune system causing frequent diseases
  • slow wound healing and easy bruising.

Question 29

How was the required amount of vitamin C for humans calculated

Answer 29

• guinea pigs (can’t make vitamin C) were fed diets with different levels of vitamin C, while all other conditions were controlled
  
  • Group 0 doesn’t get any foods with vitamin C
  • groups 1-10 get increasing levels of a daily supplement of vitamin C in their diet
  • group 0 starts developing symptoms of scurvy
  • groups 1-2 might also show some symptoms
  • data collected can be used to calculate amount of vitamin C required by a human

Question 30

Why can humans not synthesize vitamin C

Answer 30

• the metabolic pathway to synthesize vitamin C requires GLO (L-gulonolactone oxidaze) enzyme. this is required for the last step of vitamin C synthesis
• many mutations have occured preventing the enzyme from being produced
• loss of the ability to synthesize vitamin C, meaning it’s required in diet
• many mammals can make vitamin C, most primates can not

Question 31

What is phenylketonuria

Answer 31

• PKU
• genetic disease
• gene coding for phenylalanine hydroxylase, which is the enzyme that catalyses the hydroxylation of phenylalanine to tyrosine, is mutated, resulting in inability to convert phenylalanine into tyrosine
• PKU is inherited as an autosomal recessive trait
• enzyme can no longer catalyse the last and rate limiting step, so phenylalanine accumulates in the body

Question 32

What are consequences of PKU

Answer 32

• consequences:
  
  • intellectual disability
  • reduced growth of the head
  • lack of skin and hair pigmentation
  • seizures

Question 33

How is PKU diagnosed and treated

Answer 33

• needs to be detected and diagnosed within 24 hours of birth
• Guthrie test is used to detect PKU
• until 24 hours, the phenylalanine and tyrosine levels in the baby are normal as a result of the normal metabolism of the mother
• PKU patients need a diet low in phenylalanine

Question 34

What are the roles of Vitamin D

Answer 34

Vitamin D (Calciferol) is needed for absorption of calcium in the digestive system

most important roles of vitamin D: maintaining skeletal calcium balance by promoting calcium absorption in the intestines, maintaining calcium and phosphate levels for bone formation

Question 35

What happens if there’s a deficiency in Vitamin D

Answer 35

• calcium is needed to build healthy bones, so a deficiency of calciferol can lead to softening or malformation of the bones
• in adults, this is called osteomalacia (milder). in children it’s called rickets (serious)
• in breastfeeding mothers with low vitamin D intake, there can be problems with the bone mineralisation of their infants

Question 36

Why does Vitamin D not fit the definition of a vitamin

Answer 36

• exposing skin to UV light with wavelength between 290-310 nm triggers synthesis of vitamin D in the skin
• Vitamin D can be made in the body, so doesn’t really fit the definition of a vitamin
• if skin is exposed for a short time in the open air it is enough to get a daily dose of vitamin D

Question 37

How can we store vitamin D when unable to synthesize it

Answer 37

a certain amount of vitamin D, which is fat soluble, can be stored in the liver for when we are unable to synthesize it

Question 38

Where is vitamin D found

Answer 38

Vitamin D is found in foods such as oily fish, particularly salmon, herring and tuna; egg yolk; liver; and dairy products including milk, cheese and butter.

Question 39

What is cholesterol

Answer 39

• Cholesterol is the precursor of bile acids, vitamin D, and steroid hormones like progesterone and oestrogen
• cholesterol protects the membrane integrity of animal cells, and enables the cell to change shape and move about
• total cholesterol is the sum of the very low density lipoprotein, low density lipoprotein, and high density lipoprotein

Question 40

What does blood cholesterol levels indicate

Answer 40

Cholesterol in the blood is an indicator of the risk of coronary heart disease. Only cholesterol in LDL is associated with an increased risk of developing CHD.

Question 41

How can blood cholesterol levels be lowered

Answer 41

drugs like statin are more effective in lowering blood cholesterol levels than diet control. statins are drugs that inhibit the enzyme HMG-CoA reductase, which catalyses the second step in the pathway from Acetyl CoA to cholesterol

Question 42

How can energy content of food be measured

Answer 42

• energy content in food can be measured by burning a known mass of the food to test
• burning food is placed under the test tube with water
• heat liberated by the burning food is absorbed by a volume of water
• rise in temperature is recorded
• energy value is calculated as temperature rise * mass of water * specific heat capacity of water

Question 43

how do food particles get digested into soluble molecules

Answer 43

to digest food particles into soluble molecules that can pass through membranes, the exocrine glands of the digestive system secrete enzymes that hydrolyse large molecules into smaller molecules

Question 44

What does the presence or smell of food do to the body

Answer 44

the presence or smell of food stimulates the digestive system, and thinking about it makes your body secrete saliva and gastric juice to prepare for future intake of food

Question 45

What are the parts of nervous control of digestive juices

Answer 45

• nervous control is mainly provided by the autonomic nervous system which is divided into the sympathetic and parasympathetic systems
  
  • sympathetic system controls processes involved in responses to danger. slows down the speed of digestion when there’s no food available.
  • parasympathetic system controls homeostasis and processes related to rest and digestion. it speeds up digestion when food is ingested

Question 46

What does food force the secretion of throughout the digestive tract?

Answer 46

having food in the mouth induces the secretion of saliva and the presence of food in the gut will induce the secretion of gastric juice (especially after eating proteins), intestinal juice, pancreatic juice, bile (especially if you have eaten fats)

Question 47

What are the hormones involved in chemical control of digestion

Answer 47

• gastrin
  
  • produced by special cells (G cells) in the stomach, duodenum, and pancreas, in response to physical stimulation due to the presence of food, as well as chemical stimulation by protein
  • when released, it stimulates the production of gastric juice by the parietal cells in the gastric glands
  • gastric juice has a mixture of water, hydrochloric acid, and other inorganic ions, enzymes (pepsin, rennin), mucus, various, polypeptides, and intrinsic factor
  • intrinsic factor is necessary for absorbing vitamin B12
  • gastric juice changes the pH of the food content from 6.7 to 2, providing acidic conditions that will enhance digestion
  • when there’s sufficient gastric juice present (around 1 to 1.5 litres), the production of gastrin will stop and subsequently so will the secretion of gastric juice
• secretin
  
  • made by special cells in the small intestine in response to the presence of acidic fluid
  • presence of gastric acid activates prosecretin into secretin. when released, it stimulates the production of alkali by the pancreas, neutralising intestinal components
  • when pH of intestine reaches 8, the production of pancreatic juice is stopped by negative feedback
  • secretin plays a role in osmoregulation since it regulates water homeostasis throughout the body by acting on the kidney, hypothalamus, and pituitary gland
• cholecystokinin (CCK)
  
  • produced by the small intestine when food is present in there
  • controls release of pancreatic juice from the pancreas and bile from the gall bladder (bile is made in the liver and stored in the gall bladder)
  • acts as a hunger suppressor

Question 48

What is somatostatin

Answer 48

Somatostatin is an inhibitory hormone that suppresses digestion. it’s secreted by special cells in the stomach, duodenum and pancreas. it travels through blood to directly inhibit acid producing cells. also acts indirectly by preventing the release of gastrin, CCK, and secretin, thus slowing down the digestive process

Question 49

What is acid secretion regulated by and why

Answer 49

acid secretion is regulated by the nervous system, which causes direct stimulation of parietal cells to secrete acid, and indirect stimulation by decreasing somatostatin secretion

Question 50

What is the regulatory feedback mechanism

Answer 50

a regulatory feedback mechanism exists whereby the presence of acid in the lumen of the stomach stimulates somatostatin secretion, which in turn slows down acid secretion

Question 51

How do secretory products get where they need to be

Answer 51

exocrine glands have ducts that carry their secretory product to the surface of the body or the lumen of the gut. these include the sweat, sebaceous, and mammary glands and the glands that secrete digestive enzymes

Question 52

How does digestion in the stomach work

Answer 52

• first studies into digestion in the stomach were performed in 1822
• Alexis st. martin (18 yr old Canadian) was accidentally wounded by discharge of a musket
• wound was serious and left a hole in his body but he survived
• his doctor William Beaumont was able to extract gastric juice by introducing an elastic tube into the stomach through the wound. then he observed which foods were digested and under which conditions
• acid in the stomach is produced by combination of hydrogen (H+) and chloride (Cl-) ions produced by the epithelial cells (known as parietal cells) of the stomach lining
• release of hydrogen ions through protein carriers is coupled to the intake of potassium ions (K+) from the lumen of the stomach. this process requires energy in the form of ATP

Question 53

What is the structure of gastric juice

Answer 53

• gastric juice has hydrochloric acid and pepsin
  
  • pepsin is a protease that hydrolyses proteins to peptides
  • pepsin is found in the stomach in an inactive form as the pro-enzyme pepsinogen
  • pepsinogen is released by the chief cells in the lining of the stomach and is activated into pepsin by the presence of acid
  • hydrochloric acid released by the parietal cells of the stomach removes 44 amino acids from pepsinogen, transforming it into pepsin

Question 54

What is the optimum pH for pepsin and why’s it important.

Answer 54

acid conditions in the stomach favour the hydrolysis reactions by pepsin. the optimum pH for this enzyme is 2. acidic conditions help control pathogens in ingested food. the bacteria present in food can’t survive such acid conditions. the mucus cover of the stomach avoids self-damage

Question 55

How is a gasstric ulcer developed and what is it

Answer 55

• in come cases (either because the patient has eaten spicy foods, excess proteins, or is very stressed) the stomach will produce an excess gastric acid. this can damage the mucus layer, producing gastric problems which might develop into a gastric ulcer
  
  • gastric ulcer — lining of the stomach are disrupted. main symptoms are stomach pain, heartburn, nausea, and in some cases presence of blood in the stools
• • another case of gastric ulcers is the presence of the bacterium Helicobacter pylori in the stomach. H. pylori produces toxins that cause continuous gastric inflammation. the inflammatory response by the immune system damages the stomach lining
• ulcers due to H. pylori are treated with a combination of medications:
  
  • amoxicillin — antibiotic that directly inhibits the synthesis of bacterial cell walls
  • clarithromycin — antibiotic that prevents bacteria from growing by inhibiting the translation of peptides in the ribosome, thus inhibiting their protein
  • proton pump inhibitor (PPI) — inhibits acidification of stomach
    
    • block the proton pump (hydrogen-potassium-ATPase pump), responsible for secretion of hydrogen ions (H+) in the stomach
    • the decrease of H+ into the lumen of the stomach reduces the amount of hydrochloric acid (HCl) produced, which makes the stomach less acidic and a suitable treatment of gastric ulcers

Question 56

What happens to food when its digested

Answer 56

If absorption in the small intestine:

• once digested, food products are absorbed by the digestive system into the blood or lymphatic system and carried to different organs, where they are metabolised into other molecules

Polysaccharides: Digested to monosaccharides. Absorbed by small intestine. Go to Villus through hepatic portal vein to liver

Proteins: Digested to amino acids. Can be absorbed by stomach or small intestine. If absorbed by stomach, they go to the cells of the stomach lining. If absorbed by small intestine, they go to the villus through the hepatic portal vein to the liver.

Lipids: Digested to short chain fatty acids, absorbed by small intestine, then go to villus through hepatic portal vein to liver. Can also be digested to longer chain fatty acids, absorbed by small intestine, then reach the lacteal to symphatic system.

Question 57

Where does most absorption occur

Answer 57

In the small intestine

Question 58

What are the main adaptations of the structure of cells in the epithelium of the villus

Answer 58

• increased surface area due to presence of villi and microvilli
• many mitochondria to provide energy for active transport
• presence of capillaries in villi for absorption of digested foods presence of lacteal for absorption of absorbed lipids
• presence of pinocytotic vesicles aid the uptake of fluids
• presence of tight junctions to ensure molecules don’t escape through the membrane, and to maintain a concentration gradient
• enzymes (peptidases and disaccharidases) being bound to epithelial membranes to complete hydrolysis/digestion

Question 59

What are the layers of the wall of the small intestine

Answer 59

• mucosa — has epithelium formed by enterocytes, goblet cells, and endocrine cells. enterocytes are cells that have microvilli. they digest and absorb substances. goblet cells make mucus and endocrine cells secrete hormones
• submucosa — contains blood vessels and connective tissue
• circular muscle layer — smooth muscle arranged in a circular manner
• longitudinal muscle layer — smooth muscle arranged in a longitudinal manner
• serosa — single layer of epithelial cells with connective tissue

Question 60

How are polysaccharides digested

Answer 60

polysaccharides are mainly hydrolysed to glucose and absorbed by epithelial cells of the small intestine. glucose is co-transported with sodium (Na+) by facilitated diffusion. for this to happen sodium must first be transported out of the cell by active transport (along the basal membrane). this powers the co-transport of glucose and sodium into the epithelial cells through the apical membrane. the glucose is then carried along the epithelial cell to a sugar transporter protein that allows its transport into the capillaries, which will carry it to the hepatic portal vein

Question 61

How are proteins digested

Answer 61

proteins are digested by proteases into amino acids, which are transported by co-transport with sodium into epithelial cells. amino acid carrier proteins then carry them by facilitated diffusion into the capillaries

Question 62

How are fats/liquids digested

Answer 62

fats/lipids are emulsified in the intestines by bile. this transforms them into smaller droplets, allowing lipases to digest them into fatty acids and glycerol. the glycerol will be absorbed and used in carbohydrate metabolism and the fatty acids will diffuse into the small intestine epithelial cells. long chain fatty acids will combine with proteins to form chylomicrons. the chylomicrons travel to the border of the cell in the smooth endoplasmic reticulum and are expelled by exocytosis to later enter the lacteal, thus entering the lymphatic system

Question 63

Why are villi epithelial cells rich in mitochondria

Answer 63

exocytosis is a form of active transport. active transport requires energy, therefore villi epithelial cells are rich in mitochondria, as a lot of ATP is required

Question 64

What is the role of the large intestine

Answer 64

large intestine is in charge of absorption of water and minerals and vitamin K

Question 65

Why is fibre important

Answer 65

• insoluble fibre is not digested so it has no nutritional value. but fibre is still important since it increases faecal mass, stimulating peristaltic movements
• dietary fibre aka insoluble fibre — non-digestible carbohydrates, especially cellulose and lignin, that are intrinsic and intact in plants

Question 66

Which materials arent absorbed in the digestive system

Answer 66

materials that aren’t absorbed are cellulose and lignin from plant matter, bile pigments, the remains of intestinal epithelial cells, and bacteria

Question 67

What is the relation between transit of materials through large intestine and their fibre content?

Answer 67

Positive correlation

Question 68

Define constipation

Answer 68

constipation is unsatisfactory defecation, characterised by infrequent bowel movement, difficult stool passage, or both

Question 69

What happens during an infection of the intestines and why

Answer 69

an infection of the intestines due to a virus, bacterium, or parasite, will cause inflammation of the epithelial cells lining the intestine. this reduces the absorption of water, causing the feces to be loose or liquid (diarrhoea). if the infection stays for several days it can cause dehydration.

Question 70

Define cholera and its symptoms

Answer 70

• cholera is a disease caused by ingestion of food or water contaminated with the bacterium Vibrio cholerae. when cholera toxin is released from the bacteria in the infected intestine, it binds to the intestinal epithelial cells (enterocytes), and triggers endocytosis of the toxin. the toxin becomes an active enzyme which activates ions and water to leave the infected enterocytes, leading to watery diarrhea
• there are 4 million patients with cholera every year internationally.
• symptoms of cholera:
  
  • vomiting
  • muscle cramps
  • profuse diarrhea

Question 71

What are the signs and symptoms of dehydration and threatment

Answer 71

• sings and symptoms of dehydration:
  
  • increased thirst
  • dry mouth
  • swelling of brain
  • weakness
  • dizziness
  • palpitations
  • seizures
  • drop in blood pressure
  • fainting
  • decreased urine output
  • kidney failure
  • coma
  • death
• treatment of dehydration includes use of antibiotics to kill the bacteria and oral or intravenous rehydration

Question 72

Where is the liver located

Answer 72

found under the diaphragm in the upper right part of the abdomen

Question 73

List the functions of the liver

Answer 73

• Production of bile, enzymes, hormones, cholesterol, triglycerides
• Removal of toxins from blood, drugs
• Maintenance of blood temperature and pressure
• Breakdown of red blood cells
• Regulation of blood clotting
• Conversion of ammonia to urea
• Storage of glycogen, vitamin A B12 D and K, minerals such as iron and copper
• Synthesis of amino acids and proteins

Question 74

What is the flow of blood through the liver

Answer 74

• liver is supplied with oxygenated blood from the heart through the hepatic artery
• hepatic artery is a branch of the aorta
• blood then leaves the liver through the hepatic vein, which carries deoxygenated blood. the vein joins the vena cava, which returns the blood to the heart
• liver also receives deoxygenated blood coming from the spleen, stomach, pancreas, gall bladder, and intestines through the hepatic portal vein. this vein carries foods absorbed mainly in the small intestine. it’s rich in amino acids, glucose, vitamins, minerals, and other foods. blood supplied by this vessel represents majority of the blood received by the liver (75%)
• as the liver receives oxygenated blood from hepatic artery and deoxygenated blood from the hepatic portal vein, we say that the liver has a dual blood supply
• Because the blood from these two sources is mixed before entering the liver, its cells never receive fully oxygenated blood.
• In the liver, blood from the hepatic artery and the hepatic portal vein supply the sinusoids that bathe the hepatocytes and Kupffer cells. As blood passes through the liver, the hepatocytes monitor the contents of the blood and remove many toxic substances such as alcohol and drugs before they can reach the rest of the body. Enzymes metabolise these toxins to render them harmless

Question 75

How does the liver help in homeostasis

Answer 75

Many metabolic reactions take place in the liver. These reactions liberate heat, therefore when blood passes through the liver it is warmed up. This helps to maintain the body temperature in warm-blooded organisms.

Question 76

What is the structure of the liver

Answer 76

The liver is a triangular shaped organ of approximately 1,500 to 2,000 g consisting of four lobes. The internal structure of each lobe has around 100,000 lobules, each consisting of a central venule coming from the hepatic vein surrounded by sixvenules coming from the hepatic portal vein and sixarterioles from the hepatic artery. These blood vessels are connected by sinusoids

Question 77

What are the differences between capillaries and sinusoids

Answer 77

Pores: Capillaries have very small pores called intracellular clefts. Sinusoids are fenestrated with pores of approximately 175 nm diameter
Membrane: Capillaries have a continuous basement membrane. Sinusoids have a discontinuous basement membrane
Shape: Capillaries have a cylindrical shape. Sinusoids have no definite shape
Size: Capillaries have smaller size. Sinusoids have a larger size.
Intracellular space: Capillaries have little intracellular space, sinusoids have large intracellular space
Passage: In capillaries only small molecules can pass. Sinusoids are leaky.

Question 78

What are the two types of lobular cells

Answer 78

The lobules have mainly two types of cells, hepatocytes and Kupffer cells (as shown inFigure 1).Hepatocytesperform most of the liver functions, especially storage and metabolism. These cells are large (around 25 μm) and constitute around 80% of the total liver cells. Their nucleus is round and found in the centre of the cell. These cells are capable of regenerating when exposed to toxic substances. Liver regeneration involves the replication of hepatocytes followed by the replication of other liver cells. Once cell proliferation is completed, the newly divided cells undergo restructuring and reformation of the extracellular matrix to complete the process. During regeneration, liver function is only partially affected. Because human liver cells regenerate it has become possible to use partial livers from living donors for transplantation, thereby increasing the number of organs that are available for transplantation.

Hepatocytes are involved in many metabolic processes, therefore they are rich in mitochondria, Golgi complexes, rER, ribosomes, glycogen granules and lipid droplets.

Question 79

What do hepatocytes synthesize and how does this affect their structure

Answer 79

Plasma proteinsare synthesised in hepatocytes mainly in the rough endoplasmic reticulum (rER) and processed in Golgi complexes. As we have mentioned before, hepatocytes are also involved in the degradation of toxins, such as detoxification of alcohol. Many of the detoxification reactions occur in the smooth endoplasmic reticulum (sER). Hepatocytes also have an exocrine function in the secretion of bile.

Hepatocytes can have up to 1000 mitochondria and 50 Golgi complexes per cell.

Question 80

What are kupffer cells

Answer 80

Kupffercellsare white blood cells (macrophages) that break down red blood cells.Therefore they are involved in the recycling of erythrocytes, as you will see later in this subtopic.In the lobules there are also canals (bilecanaliculi) that carry bile to thebile ductthat leads to the gall bladder where bile is stored until it is used in the small intestine.

Question 81

How can liver cells be seen under the microscope

Answer 81

Temporary mounts of liver cells can be prepared from fresh liver tissue and observed under light microscope. This can be done by mashing pieces of liver tissue in a mortar together with 10 ml salt solution. Cells can be stained with a drop of methylene blue before placing the coverslip on the slide. Part of the liver of a mouse under the light microscope is shown inFigure 3(a)at a magnification of×100andFigure 3(b)at×400.

Question 82

What is a main function of the liver

Answer 82

The liver is in charge of the processing and storage of many nutrients. As you have seen in the previous section, blood enters the liver through the hepatic portal vein. This vein carries most of the food digested and absorbed in the digestive tract.

Question 83

How do hepatocytes store energy for the body

Answer 83

Hepatocytes in the liver absorb most of the glucose and store it asglycogen. When the body requires energy, this glycogen is broken down into glucose

Question 84

What happens to fatty acids passing through the liver

Answer 84

Fatty acids in the blood passing through the liver are absorbed by hepatocytes and metabolised to produce energy in the form of ATP. Hepatocytes also synthesise lipids such as triglycerides,cholesteroland phospholipids. These lipids can be bound to proteins forming lipoproteins, which are now soluble in blood plasma and can therefore be transported in blood to all the body. Much of the cholesterol produced by hepatocytes gets excreted from the body as a component of bile.

Question 85

What happens to amino acids passing through the liver

Answer 85

Amino acidsentering the liver are transformed into other amino acids or are used in the synthesis of new proteins. Endoplasmic reticulum and Golgi apparatus in hepatocytes produceplasma proteins. These plasma proteins include fibrinogen used in blood clotting, and albumin that transports hormones and maintains the blood pH

When amino acids are no longer necessary,hepatocytes remove the amine group from the acid group (deamination). The acid group of the amino acid is used to produce energy or new glucose molecules while the amine group is converted into ammonia. As ammonia is toxic, it is transformed intourea, which is then eliminated by the kidneys in urine

Question 86

How does the liver do detoxification

Answer 86

A very important function of the liver isdetoxification. The liver gets rid of drugs, hormones and other toxins. In some cases it breaks down the substances into harmless compounds. If it cannot break them down, it attaches these substances to other organic groups (such a glycine), which allows the kidneys to recognise them as unwanted waste material and are therefore excreted

Question 87

What does the liver metabolize

Answer 87

The liver is in charge of metabolisingalcohol. InFigure 2, itshows the chemical reactions involved in this process. Ethanol is oxidised intoacetaldehyde, a toxic substance, by the hepatic enzyme alcohol dehydrogenase. Acetylaldehyde is converted into a less toxic substance,acetate, by aldehyde dehydrogenase. Acetate is then broken down to acetyl-CoA that can enter fatty acid metabolism or be used in the Krebs cycle. If acetaldehyde is not broken down immediately, it can combine with proteins that induce liver injury. Excess of alcohol can damage the liver, causingcirrhosis

Question 88

How do erythrocytes optimize their capacity

Answer 88

Red blood cells orerythrocytesare cells modified to increase their capacity in the transport of oxygen. In order to do this, they have a biconcave shape and have lost their nucleus and organelles. These cells are rich in haemoglobin, a protein that binds oxygen (as HL students will see in sectionhaemoglobin and myoglobin). The biconcave shape increases their surface area:volume ratio, thus increasing the absorption of oxygen. The lack of nucleus increases the amount of hemoglobin in each cell. But at the same time this means that they cannot reproduce, therefore they must be produced in the bone marrow from undifferentiated cells

Question 89

What is the life cycle of an erythrocytes

Answer 89

Erythrocytes are produced in the bone marrow and are liberated into the bloodstream.They die after approximately 120 days circulating in blood. Dead erythrocytes are engulfed by macrophages in the liver, spleen or bone marrow by phagocytosis. In the liver, these macrophages areKupffer cells

Question 90

What happens to hemoglobin in Kupffer cells

Answer 90

In the Kupffer cells, the hemoglobin is split into globin chains and heme groups.Globinis re-used in protein synthesis. Theheme groupis transformed into iron and bilirubin.Ironis carried back to the bone marrow where it is used to produce new red blood cells.Bilirubinis secreted into bile that will be used in the emulsification of fats.Figure 1shows the function of the liver in the recycling of erythrocytes

Question 91

What is the role of cholesterol in nutrition

Answer 91

Cholesterolis one of the most well-known fats. You ingest cholesterol in your diet, but it is not essential, as most cholesterol molecules are synthesised in the liver. As most animal cells require cholesterol for membrane synthesis, a small portion is added to the membranes of hepatocytes, and the rest is exported as lipoproteins or bile salts. Cholesterol is also a precursor for other importantmolecules: the bile salts, steroid hormones (such as oestrogen and progesterone), and vitamin D. Cholesterol synthesis is regulated according to its concentration in cells. This depends on the amount ingested in diet, and the regulation is performed by the hormones glucagon (inactivating its synthesis) and insulin (activating its synthesis)

Question 92

Draw a processes diagram of the liver

Answer 92

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Question 93

Draw a molecule of cholesterol

Answer 93

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Question 94

How are cholesterol carried in blood

Answer 94

Cholesterol molecules, like triglycerides and phospholipids are insoluble in water. Therefore, to be carried in blood to other tissues, they need to be carried as plasma lipoproteins. Different combinations of lipids and proteins produce particles of different densities. High-density lipoproteins (HDL) contain more protein, while low-density lipoproteins (LDL) contain more lipids.LDLs and HDLs are both produced in the plasma; however a small amount is synthesised in the liver. The function of LDLs is to transport cholesterol from the liver to other organs. The function of HDLs is to transport cholesterol from tissues to the liver.

Question 95

What causes a plaque and what are the consequences

Answer 95

Fats can deposit in arteries causing an atheroma orplaque. This is mainly caused by white blood cells (foam cells) and LDL. Molecules of LDL deposit in the blood vessels and can become oxidised. This will causeatherosclerosisof the walls of the arteries (Figure 2)

Question 96

What is the difference between atherosclerosis

Answer 96

Do not confuse atherosclerosis (narrowing of arteries due to plaque) with arteriosclerosis (hardening of arteries)

Question 97

What happens if there’s an atheroma in the heart or brain

Answer 97

After some time this can cause cardiovascular disease and stroke. If the artery leading to the heart (coronary artery) is clogged, the cells of the heart will not receive enough oxygen and can therefore die. These cells are replaced by fibres causingcoronary heart disease(CHD). If the artery leading to the head (carotid artery) is affected, this can lead to a brainstroke.

Question 98

What is good cholesterol and bad cholesterol

Answer 98

HDL is considered “good” cholesterol as it removes LDL from blood by transporting it to the liver and helps to maintain the endothelium of the blood vessels, thus avoiding coronary heart problems.

Question 99

What are bile salts

Answer 99

Bile saltshave a crucial role in digestion as theyemulsifyfats. This means they break fats down into smaller droplets to increase their surface area. This allows enzymes (for example pancreatic lipase) to work better.

Bile salts are synthesised by the liver from surplus cholesterol, and may be modified by bacteria in the intestines. Bile salts are reabsorbed from the intestines into the liver, but lots are lost in faeces. Approximately 600mg of bile salts are synthesised daily to replace bile acids lost in egestion. Bile salts aid in the digestion and absorption of dietary lipids and fat-soluble vitamins.

The liver produces about onelitre of bile per day. This fluid is carried by the bile canaliculi to the bile duct, which carries it to the gall bladder to be stored. The composition of bile is mainly water (97%), bile salts, cholesterol and fatty acids, bilirubin (from the breakdown of erythrocytes) and inorganic salts.

Question 100

What is jaundice

Answer 100

Jaundiceis a condition where the skin and white of the eyes turn yellow. It is caused by the presence ofbilirubinin extracellular fluid. As you have seen before, bilirubin is produced from haemoglobin breakdown in erythrocyte recycling in the liver. The metabolism of haemoglobin accounts for 65% to 80% of the total bilirubin production. Bilirubin in blood binds reversibly to albumin (a plasma protein), forming conjugated bilirubin that travels to the liver, which removes it from the plasma. When the liver is not able to remove the bilirubin from blood, its level may rise (especially in the unconjugated form) and the skin and eyes may begin to appear jaundiced.

Jaundice appears under several circumstances

• Increased destruction of red blood cells.
• Immaturity in the conjugation of bilirubin (greater in premature babies).
• Genetic diseases (e.g.Gilbert syndrome).
• Defects in the secretion of conjugated bilirubin from hepatocytes (in liver damage).
• Defects in transit of bilirubin to intestines (e.g.with bile duct obstruction).

Question 101

What happens if there’s a high level of bilirubin, and why is it normal in babies

Answer 101

A high level of bilirubin in the blood is a sign of liver malfunction. Depending on the level of exposure, the effects range from clinically unnoticeable to severe brain damage and even death. Jaundice is usually a symptom of hepatitis or liver cancer. It can also be caused by the use of drugs, genetic factors, malaria or anemia

It is common for a baby’s bilirubin level to be a bit high after birth as it might take some time for the liver to function properly. Some of the causes are a mismatch between the blood type of the mother and the child, lack of certain enzymes, or excess or abnormal blood cells.Special blue lights are used on infants whose bilirubin levels are very high

Question 102

What is cirrhosis

Answer 102

Cirrhosisis a disease where the damaged liver tissue is replaced by scar tissue. Not only does this affect the functioning of liver cells, but also interferes with the blood supply to these cells. The symptoms are weakness, fatigue, jaundice and bruising. A liver biopsy will confirm the presence of scars. There is no cure for this disease. A liver transplant can be the solution in extreme cases.

Question 103

What are the effects of excessive alcohol or drug consumption

Answer 103

Excessive alcohol or drug consumption may cause liver cirrhosis. Other causes of cirrhosis include chronic viral hepatitis B or C, chronic bile duct obstruction, fatty liver disease, excess of iron, cystic fibrosis and Wilson’s disease

The amount of alcohol consumed affects the possibility of liver cirrhosis in a direct manner:the greater the consumption, the greater the chances of dying of liver cirrhosis. The probability of dying of cirrhosis is greater in women than men at lower alcohol consumption, but higher for men at greater alcohol consumption, as shown inFigure 4.

Question 104

Why should or shouldn’t alcoholics receive a transplant

Answer 104

Why should alcoholics be entitled to receive a liver transplant?
- Everybody has the right to live.
- Theycan change their lifestyle and stop drinking.
- Theymight be the only support for a family.
- Many people care for them.

Why should they not receive a liver transplant?
- They caused the liver damage by their own choice of drinking.
- They must put up with the consequence of their own reckless attitude.
- Other people deserve the transplant more.
- Theycan relapse back into drinking and damage the new liver.

Question 105

Define cardiac muscle

Answer 105

Type of striated muscle found in the wall of the heart

Question 106

What is the function of cardiac muscle cells

Answer 106

Allow propagation of stimuli through the heart wall

Question 107

What is the structure of cardiac muscle cells

Answer 107

• Has thick and thin muscle fibres with myofibrils containing myofilaments similar to those found in skeletal muscle
• Nucleus is in the centre of the cell
• Rich in mitochondria and glycogen granules that are found adjacent to the myofibrils
• Numerous short, cylindrical cells arranged end-to-end, resulting in long branched fibres, giving a y-shape
• “all or none” effect: once a cell is activated, it produces maximum contraction

Question 108

What are intercalated discs

Answer 108

The attachment site between cardiac muscle cells(not present in skeletal cells). Appears as a linear structure transverse to the muscle fibre. Contain adhering junctions between cells that hold cells together and gap junctions, allowing communication between cells. Allow electrical impulses to pass rapidly from cell to cell, so linked cells contract almost simultaneously.

Question 109

What are gap junctions

Answer 109

Arrays of densely packed protein channels that permit intercellular passage of ions and small molecules. Electrical activation of the heart requires cell-cell transfer of current via gap junctions.

Question 110

What is the refractory period for cardiac muscle cells

Answer 110

Period during which cells cannot contract for a second time, to ensure systole of the heart is separated by a diastole.

Question 111

What are the steps to a heartbeat

Answer 111

1. Initiated in the sinoatrial node
   
   1. Signals from the sinoatrial node that cause contraction cannot pass directly from the atria into the ventricles
2. Impulse spreads along the atria to the atrioventricular node
3. Impulse spreads to the ventricle
   
   1. Note: There’s a delay between the arrival and passing on of a stimulus at the atrioventricular node. This allows time for atrial systole before the atrioventricular (tricuspid and bicuspid) valves close
4. Blood leaves the atria to the ventricles when the atrial systole occurs, and atrioventricular valves close
5. In the interventricular walls, there is the Bundle of His which leads to the Purkinje fibres that carry the impulse at a very high speed
6. Conducting fibres ensure coordinated contraction of the entire ventricle wall. The ventricular contraction is called the systole
7. Blood flows out of the heart as the semilunar (pulmonary and aortic) valves open and give access to the aorta and pulmonary artery
8. The heart relaxes

Question 112

What is the sinoatrial node

Answer 112

Group of specialised cardiac muscle cells found where the superior vena cava joins the right atrium.

Question 113

What is the Bundle of His

Answer 113

Specialised fibres grouped to form a bundle in the interventricular walls. Splits into to branches that go to the left and right ventricles, leading to the Purkinje fibres

Question 114

What is a purkinje fibres

Answer 114

Specialised cells that carry impulse at a very high speed.

Question 115

What are the heart sounds

Answer 115

Sounds generated by the beating of the heart and the closing of the heart valves. Lub-dub in a healthy person. Caused by the closing of the atrioventricular valves at the beginning of the ventricular systole (lub) and the closing of the semilunar valves after the ventricular systole and beginning of the diastole (dub).

Question 116

Define a stethoscope

Answer 116

used to listen to the heart sounds. Acoustic device that has a resonator that is placed on the patient’s chest and two tubes connected to the earpieces.

Question 117

What are the factors that increase/decrease heart rate

Answer 117

Factors that increase heart rate:

• Gender: Women have slightly higher because they need more energy for metabolism
• Physical activity: More blood is required in muscles for oxygen supply
• Body size: larger people have higher heart rates since blood needs to cover a larger area
• Temperature: Vasodilation occurs when it is hot, increasing heartbeat. If running a fever, pulse is accelerated
• Altitude: Body requires a greater amount of oxygen, therefore cardiac output must increase
• Posture: When standing, the heart rate is higher than when lying down. Related the the effect of gravity, since when standing, blood needs to be pumped against it.
• Stress: Body produces epinephrine, which will accelerate the rate
• Eating: More blood needs to be pumped to the stomach and intestines after eating
• Sodium and calcium ions in blood: Blood retains more water to dilute the ions, so it needs to pump more. Patients suffering from dehydration will have a higher rate due to increase in concentration of ions in blood.
• Drugs: Caffeine and nicotine are both stimulants of the nervous system and of the cardiac centres, causing an increased heart rate.

Decrease:
- Age: heart muscles can’t be pumped as efficiently
- Potassium ions: decrease action potentials

Question 118

What are the terms for irregular heart beats

Answer 118

Bradycardia: Heart beating too slowly

Tachycardia: Heart beating too quickly

Arrhythmia: Heart beating irregularly

Question 119

What is an artificial pacemaker and how is it installed

Answer 119

Artificial pacemaker: Battery-powered generator that sends out electrical impulses and wires with electrodes to connect to the heart muscle to maintain the heart rate pace. If it senses the heartbeat is too high, it will stop sending signals to the heart. Pacemaker senses when heartbeat is too slow as well, and automatically turn back on and start pacing the heart again.

Installation: Small cut is made on the left side of the chest or abdomen, and the generator is placed under the skin. The pacemaker can have one lead leading to the right atrium or two leads, one to the right atrium and one to the right ventricular walls. Another type also includes a lead to the left ventricle.

Question 120

What is an ECG (Electrocardiogram) and how is it read

Answer 120

Function: Checks electrical activity of the heart. Electrodes that detect electrical changes on the skin are placed on the patient’s body. These changes are made from the muscle electrical activity due to cardiac conduction in the heart.

Reading: Signals obtained in ECG are amplified in the ECG machine and displayed on the screen of an oscilloscope or recorded on a moving paper, giving a graph of voltage variations in time. The R-R interval between successive beats allows the calculation of the heart rate. P-wave represents the SA node electrical activity and contraction of the atria. QRS complex corresponds to the excitation of the ventricles. T-wave is the relaxation of ventricles following contraction. An abnormal ECG pattern is most likely a sign of heart failure.

Question 121

Draw and label an ECG reading

Answer 121

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Question 122

Define blood pressure

Answer 122

Definition: Pressure of blood on the walls of an artery during systole and diastole. During systole, blood flows out of the heart at a high pressure through arteries, which support the pressure because their walls are elastic and strong. During diastole, the pressure of the blood on the arteries is at its lowest.

Question 123

Define a sphygmomanometer

Answer 123

Tool to measure blood pressure. Has an inflatable cuff and a measuring device, which can be mechanical or digital. Mechanical measures pressure in millimetres of mercury, while digital makes oscillometric measurements

Question 124

What is the method for an oscillometer

Answer 124

1. Cuff pressure is used to detect small oscillations in blood flow caused by the pulse
2. Oscillations increase in amplitude as cuff pressure falls between systolic and mean arterial pressure
3. Systolic blood pressure corresponds to a specific heartbeat: the beat at which the pressure becomes higher than the deflating cuff pressure and the blood is capable of flowing in the brachial artery
4. Oscillations decrease in amplitude as cuff pressure falls below mean arterial pressure
5. Corresponding mean oscillation is calculated to estimate blood pressure

Question 125

How is blood pressure measured using a sphygmomanometer

Answer 125

1. Sphygmomanometer cuff is placed on the antecubital fossa of the arm of the patient (elbow pit; triangular area on the front view of the elbow of a human)
2. Cuff is inflated to stop the flow of blood through the artery
3. Air is slowly released until the pressure in the artery is equal to the pressure exerted by the cuff. A hissing sound is heart at this moment if one places a stethoscope under the cuff close to the artery
4. A pounding sound can be heart as the cuff deflates, denoting the systolic pressure
5. Sound stops when the pressure of the cuff is smaller than that of the artery. When the pounding can’t be heard anymore, the diastolic pressure is recording.

Question 126

What are the causes and consequences of hypertension

Answer 126

Causes:

• Gender
• Obesity
• Lack of physical activities
• Age
• Genetics
• Stress/anxiety
• Sodium
• Alcohol
• Smoking
• Caffeine

Possible Consequences:

• Stroke due to a reduced or interrupted supply of blood to the brain, which causes brain cells to die
• Blindness due to the ruptured capillaries in the retina or optic nerve or damage to the area of the brain responsible for processing images
• Arteriosclerosis: The hardening of arteries, restricting the flow of oxygen and nutrients to tissues. Atherosclerosis is a special kind of arteriosclerosis caused by the damage of arteries and subsequent formation of scar tissue. A plaque is formed when cholesterol and other lipids build up on the scar tissue. The plaque then makes platelets release factors that cause the formation of a clot over the plaque, forming a thrombus, which blocks the flow of blood to the tissues, causing thrombosis. if a thrombus occurs in the coronary artery, the supply of blood and oxygen to the areas of the heart muscle is blocked, causing irregular heartbeats and can lead to CHD.
• Heart attack/failure
• Kidney failure

Question 127

What is epidemiology

Answer 127

Study of all the factors and effects that determine the presence or absence of diseases and disorders in a population.

Question 128

What is CHD

Answer 128

Decreased blood flow and oxygen to the heart muscle caused by narrowed heart arteries. Also called cardiac ischemia or ischemic heart disease.

Question 129

What are the causes of CHD

Answer 129

• Viral or bacterial infections and nutritional deficiencies (developing countries)
• Hypertension, high-fat diets, cigarette smoking, sedentary lifestyles (developed countries)
• Genetic predisposition in some ethnic groups can be explained by insulin resistance syndrome and associated chances of diabetes, or elevated triglyceride and HDL cholesterol concentrations

Question 130

Define ventricular fibrillation

Answer 130

The interruption of the electrical impulses that control the heartbeat. Can be caused by the loss of blood flow to the heart or a heart attack. Often begins with ventricular tachycardia (rapid heart beating) and leads to low blood pressure because the ventricles can’t pump hard enough

Question 131

What are the symptoms of ventricular fibrillation

Answer 131

Symptoms:

• Chest pain
• Dizziness
• nausea
• heaertburn
• fluttering heartbeat
• fainting
• coma
• nerve function loss
• changes in mental function
• death

Question 132

What is a defibrillator for

Answer 132

During ventricular fibrillation, delivering cardiopulmonary resuscitation (CPR) or electric shock to the heart can be vital to survival.

Question 133

Define CPR

Answer 133

CPR: lifesaving technique useful in a heart attack in which the heartbeat has stopped. Can keep oxygenated blood flowing to the brain and other vital organs until more definitive medical treatment can restore a normal heart rhythm. Compress the chest to restore blood circulation, clear the airway, breathe into the patient’s mouth.