IB Biology Option D
What are some risk factors that increase the risk of thrombosis and hypertension?
-Genetic predisposition -Old age causing less flexible blood vessels -A risk is in post-menopause females correlated with fall in estrogen -Males are at greater risk period because of less estrogen -Smoking raises blood pressure (nicotine causes vasoconstriction) -High salt diet -High levels of alcohol -Stress -Eating too much saturated fat and cholesterol promotes plaque formation -Height affects blood pressure -Sedentary lifestyle
What is anorexia and what are its consequences?
Anorexia is a condition in which an individual does not eat enough food to sustain the body, even though the food is available. As with starvation body tissues can be broken down, and with severe anorexia even the heart muscle is broken down.
Explain the regulation of blood pH.
Blood pH is regulated to stay within the range of 7.35-7.45. In kidney H⁺ ions can be secreted into urine bound buffers to raise pH. Bicarbonate ions can be secreted into the distal convoluted tubule of the kidney to raise pH.
Explain the effect of CO2 on ventilation rate.
During exercise, the rate of ventilation changes in response to the amount of CO₂ in the blood. Increased CO₂ from exercise is dissolved into water to form carbonic acid (H₂CO³) which further dissociates into H⁺ and HCO₃⁻, lowering pH. Chemoreceptors in the medulla, aorta and carotid artery detect this change in blood CO₂. High levels of blood CO₂ trigger an increase in ventilation rate in order to get rid of the CO₂ buildup. It diffuses into alveoli and is expelled from the body. This explains hyperventilation during exercise.
What do endocrine glands do?
Endocrine glands secrete hormones directly into the bloodstream.
State the liver's role as red blood cell recycler
Red blood cells in adults last about 120 days. Old and damaged red blood cells undergo changes making them susceptible to recognition by macrophages. At the end of life they are removed from circulation and broken down in the spleen and liver.
What controls the secretion of digestive juices?
Secretion of digestive juices is controlled using nerves and hormones.
What is starvation and what can it lead to?
Starvation is a prolonged shortage of food. Once glycogen and fat reserves are used up, starvation can lead to the breakdown of body tissue to be used in cellular respiration
What is the definition of systole?
Systole is the contraction of the heart's chambers.
What causes the sound of the heartbeat?
The "lub-dub" (yes that's the term the IB uses) sound is caused by the closing of valves. The "lub" is heard when the atrioventricular valves close. The "dub" sound is heard after the ventricles are emptied and the semilunar valves close.
What is the Bohr shift?
The Bohr shift explains the increased release of oxygen by hemoglobin in respiring tissue. Increased metabolism causes greater release of CO₂ into blood which lowers blood pH. This increased acidity shifts the oxygen dissociation curve to the right, causing a decreased affinity of hemoglobin for oxygen, causing a greater release of oxygen from hemoglobin at the same partial pressure of O₂. This shift ensures that respiring tissues have enough oxygen when their need is greatest.
Explain the role of Kupffer cells in the breakdown of red blood cells.
The breakdown of erythrocytes (red blood cells) starts with phagocytosis by Kupffer cells. When cells get old they are engulfed by Kupffer cells, macrophages lining the liver.
Explain how the liver processes nutrients.
The liver intercepts blood from the gut to regulate nutrient levels. The liver regulates glucose levels by storing glucose as glycogen or breaking glycogen into glucose. The body can't store proteins or amino acids so excess is broken down in the liver and the nitrogenous waste is processed by the liver.
Explain storage of nutrients in the liver.
When glucose levels are high insulin is released triggering the liver to store glucose as glycogen. When glucose levels are low glucagon is released and glycogen, glycerol, amino acids and fatty acids are broken down in the liver releasing glucose. Iron, vitamin A, vitamin D are stored in the liver when in excess and released into blood when there is a deficit.
Explain the specific control of volume and content of gastric secretions.
-The sight/smell of food stimulates brain to send nerve impulses to parietal cells -Parietal cells respond by secreting acid, known as a reflex action -Sodium and chloride ions also secreted, causing water to osmos into the stomach to form gastric juice -Food enters the stomach and chemoreceptors detect amino acids -Brain sends impulses via vagus nerve to endocrine cells to make them secret gastrin -Hormone gastrin stimulates further sectrion of acid and pepsinogen -Secretin and somatostatin inhibit gastrin sectrion if pH gets too low
Explain the role of acid conditions in the process of digestion.
Acid conditions in the stomach favour some hydrolysis reactions and help to control pathogens in ingested food. The acid secreted by the parietal cells disrupts the extracellular matrix that holds cells together and denatures proteins exposing their polypeptide chains.
Where is appetite controlled?
Appetite is controlled by a center in the hypothalamus. The small intestine, pancreas and adipose tissue secrete different hormones when nutrient levels are too high. If the hypothalamus receives these chemicals it reduces the desire to eat.
How does high altitude affect gas exchange?
At high altitude there is low pO₂ in the air, meaning hemoglobin may not become fully saturated, and thus the tissues may not be adequately supplied with oxygen. Adaptations to high altitude can happen, red blood cell production can increase, muscles produce more myoglobin, and evolution can lead to greater mean lung surface area and large vital capacities.
Explain the dual supply of blood to the liver.
Blood is brought to the liver by both the hepatic portal vein and the hepatic artery. The hepatic portal vein carries the most blood and brings blood from the stomach and intestines. The blood can be rich in nutrients if eating has just occurred but oxygen levels are low. The vein subdivides into sinusoids in the liver, like capillaries but wider and walls are not continuously lined with cells. This allows blood flowing through to come in contact with liver cells. The hepatic artery brings oxygen-rich blood from the aorta.
Explain blood pressure measurements.
Blood pressure comes in two numbers, a higher and lower one, and in units "mm Hg". The higher number refers to pressure in the artery caused by ventricular systole. The lower number refers to pressure in artery caused by ventricular diastole. Hypotension (low blood pressure): 90 or less over 60 or less Normal: Less than 120 over less than 80 Pre-hypertension: 120-139 over 80-89 Hypertension stage 1: 140-159 over 90-99 Hypertension stage 2: 160 or higher over 100 or higher Hypertension crisis: Higher than 180 over higher than 110
Explain carbon dioxide transport in the blood.
Carbon dioxide is carried ino solution and bound to hemoglobin in the blood Carbon dioxide is carried in three forms in blood plasma: -dissolved as CO₂ -reversibly converted to bicarbonate (hydrogencarbonate) ions (HCO₃⁻) that are dissolved in the plasma -bound to plasma proteins
Explain the conversion of carbon dioxide into hydrogen carbonate ions.
Carbon dioxide is transformed in red blood cells into hydrogen carbonate ions. That is because these ions are more soluble and less toxic than carbon dioxide. The reaction occurs in red blood and is catalyzed by carbonic anhydrase. CO₂+H₂O⇌H⁺+HCO₃⁻
Explain the use of a defibrillator to treat life-threatening cardiac conditions.
Cardiac arrest occurs when the blood supply to the heart is reduced and the heart runs out of oxygen. This can result in abnormalities in the cardiac cycle, such as ventricular fibrillation. This is the twitching of the ventricles due to chaotic contraction of individual muscle cells. A defibrillator gives off an electric discharge to restore a normal heart rhythm.
Explain the structure of cardiac muscle cells. What does their structure allow them to do?
Cardiac muscle cells are striated, like skeletal muscles. However cardiac muscle cells are shorter and wider than skeletal muscles, and normally only have one nucleus per cell. The cells are Y-shaped and all interconnected into a complex network. Where one cell connects to another there is a junction called an "intercalated disc". This junction consists of a double membrane with gap junctions allowing cells to connect cytoplasms. This overall structure allows them to be physically connected (Y-shapes) and have quick electrical/ion transport (connected cytoplasms) meaning that stimuli in one cell causes the entire network to contract as if it were one large cell.
Explain the relationship between chemoreceptors and blood pH.
Chemoreceptors are sensitive to changes in blood pH. This is evidenced by the chemoreceptors in the carotid artery and aorta that send a message to the medulla oblongata, which then sends signals faster or slower in order to regulate ventilation rate.
Explain dehydration due to cholera.
Cholera is a disease caused by infection from the bacterium Vibrio cholera. The bacterium releases a toxin that binds to receptors on intestinal cells. Once brought into the cell by endocytosis the toxin triggers a cascade response that leads to the discharge of Cl⁻ and HCO₃⁻ ions from the cell into the intestine. Water follows these ions through osmosis, leading to diarhea, and water is drawn in to replace the lost water from the blood stream, leading to dehydration.
What is coronary heart dieseae and what are the risk factors?
Coronary heart disease (CHD) is damage to the heart as a consequence of reduced blood supply to the tissues of the heart, often due to narrowing and heardening of coronary artery. Ethnic group differ in risk due to diets and lifestyles Gender, age, physical activity, genotype, medical history all have different effects on probabilyt of experiencing CHD
What is the definition of diastole?
Diastole is the relaxation of the heart's chambers
Explain the graph of the ECG Trace
ECG stands for electrocardiogram, it shows the electrical signals received by the cardiac muscles. P-wave: caused by atrial systole QRS wave: caused by ventricular systole T-wave: coincides with ventricular diastole Changes to the different waves are used to detect heart pathology
What are the treatments for emphysema?
Emphysema cannot be cured but there are treatments. Constant administration of oxygen-rich air, training in breathing techniques, quitting smoking, and sometimes surgery to reduce volume of lungs by removing lung tissue. Last case resort is lung transplant.
What is emphysema?
Emphysema is a lung condition where the walls between individual alveoli break down, leading to an increase in their size and thus a decrease of surface area for gas exchange, restricting oxygen uptake into the blood. Caused by long-term exposure to airborne irritants such as smoke, air pollution or coal and silica dust. Three factors cause the damage: -oxidation reactions produced by high concentration of free radicals in tobacco smoke -inflammation due to body responding to irritant particles in the smoke -free radicals and other components of tobacco smoke impair activity of enzyme alpha-1-antitrypisn which would normally block the activity of proteases that degrade the proteins that miantain the elasticity of the lung
What is epidemiology?
Epidemiology is the study of pattern, causes and ffects of idseases in groups of individuals or populations.
What are essential nutrients?
Essential nutreients are substances that the body needs but it cannot synthesize, and thus they must be in the diet
What are the two types of glands?
Exocrine and endocrine glands. Exocrine glands secret through a duct onto the surface of the body or into the lumen of the gut. Digestive-juice-excreting glands are exocrine. Endocrine glands are ductless and secrete hormones directly into blood.
What are the differences in oxygen affinity between fetal and adult hemoglobin?
Fetal hemoglobin is different from adult hemoglobin which allows the transfer of oxygen in the placenta onto the fetal hemoglobin. This is becausae fetal hemoglobin has a higher affinity for oxygen at all partial pressures
Why do some athletes take growth hormones and how do they work?
Growth hormone is produced by the anterior pituitary. It targets receptors in liver cells. It stimulates the release of insulin-like growth factor which circulates blood and stimulates bone and cartilage growth. It also causes increased muscle mass, but not necessarily increased strength. It may also allow tired muscles to recover more quickly.
What are some ways to detect and measure heart rate?
Heart rate can be detected by using fingers to feel the pulse of an artery in the wrist, or an artery in the neck. Additionally; hand grip heart monitors, ear clips, EKG sensors, wrist watches and even camera smartphones can measure heart rate and feed data into computers.
What is hypertension? What are the consequences?
Hypertension is the greater pressure on the walls of arteries, caused by a slowing in the flow of blood (often due to thrombosis). Consequences include: -Damage to cells that line arteries causing chain events that result in narrow and stiff arteries -Constant high blood pressure weaken an artery causing a section of the wall to form a bulge (known as aneurysm). This aneurysm could burst and cause internal bleeding -Constant high blood pressure can also cause stroke by weakening blood vessels in the brain, causing them to rupture. -Constant high blood pressure also can causae kiddney failure as it damages the arteries leading into the kidney and the capillaries in the glomerulus.
Explain the transport of iron to bone marrow.
Iron is carried to the bone marrow to produce hemoglobin in new red blood cells. Red blood cells are created in bone marrow, and hemoglobin is synthesized in red blood cells. Iron is added to the heme group here.
What do peptide hormones do?
Peptide hormones bind to receptors in the plasma membrane of the target cell. They do this because they are water soluble and cannot pass through the membrane directly, so they must bind to surface receptors that then causes a cascade reaction controlled by chemicals called second messengers.
What is Phenylketonuria ?
Phenylketonuria (PKU) is when the level of phenylalanine (an essential amino acid) becomes too high in the bloodstream. It is caused by an insufficiency or lack of phenylalanine hydroxylase, which turns phenylalanine into tyrosine. The insufficiency or lack of this enzyme is due to a mutation of the gene that codes for it.
How is phenylketonuria treated?
Phenylketonuria symptoms are not present in fetuses because the mother's body regulates phenylalanine concentrations. Phenylketonuria is now tested for at birth so that a diet can be implemented to prevent most/all harmful consequences
What do pituitary hormones do?
Pituitary hormones are secreted by the pituitary and control; growth, developmental changes, reproduction, and homestasis.
What are pneumocytes?
Pneumocytes are the cells that compose the wall of the alveolus. There are type 1 and type 2 pneumocytes. Type 1: cover 90% of alveolus surface. Extremely thin. Primary purpose of gas exchange Type 2: covered in microvilli, thicker, funtion to secrete surfactant, a substance that reduces surface tension to prevent alveolus from collapsing
What does RDA stand for when relating to the nutritional content of foods?
Recommended Daily Amount Can be in either percentage or mass units
What is the function of the atrioventricular node?
Signals from the sinoatrial node causing contraction in the atria cannot pass directly from the atria to the ventricles, the signal instead passes through the atrioventricular node. The function of the atrioventricular node is to create a delay between the arrival and passing of the stimulus. This delay is about 0.12 seconds between arrival and initiation of impulse. The delay is caused by a few structural things in the AV node: -AV node cells have a smaller diameter and do not conduct as quickly -There are fewer gap junctions in the AV node -There is more non-conductive tissue in the AV compared to the SA node
What is the purpose of steroid hormones?
Steroid hormones are fat soluble and can cross directly through the plasma and nuclear membrane to bind to receptors. This forms a receptor-hormone complex which serves as a transcription factor, promoting or inhibity the transcription of a certain gene.
Explain how bacterial infections cause ulcers.
Stomach ulcers are caused by the bacterium Heliobacter pylori. It causes part of the stomach lining to be digested by pepsin and HCl leading to open sores.
Explain the conversion of cholesterol to bile salts.
Surplus cholesterol is converted into bile salts. Cholesterol is both absorbed through food and synthesized by liver cells. The liver also regulates cholesterol levels, synthesizing or breaking down cholesterol as necessary.
What do second messengers do?
The cascade of reactions caused by a peptide hormone binding to a receptor on the nuclear membrane is mediated by second messengers. Second messengers are small water-soluble molecules that quickly spread through the cytoplasm relaying signals through the cell. The two most common second messengers are Calcium ion and cyclic AMP (cAMP) Many proteins are sensitive to the concentration of these molecules.
What is the purpose of the 0.12s delay between the arrival and passing on of the stimulus in the AV node?
The delay ensures that the atria contract and empty the blood they contain into the ventricles first before the ventricles contract.
What is the role of the hypothalamus in hormone secretion?
The hypothalamus controls hormone secretion by the anterior and posterior lobes of the pituitary gland. It links the nervous system to the endocrine system via the pituitary gland. The role of the hypothalamus is to secrete releasing factors that stimulate the secretion of the anterior pituitary gland's hormones. The releasing factors are transported from the hypothalamus to the pituitary gland by way of the partal vein.
How does the liver act as a detoxifier?
The liver removes toxins from the blood and detoxifies them. It does this using a range of chemical conversions. Examples: alcohol converted into less toxic substance by ethanol dehydrogenase Ammonia into urea One general method the liver uses is to convert hydrophobic comounds into hydrophillic compounds for easier excretion
Explain the regulation of milk secretion.
The production and secretion of milk is under control of the hormones. During pregnancy, high levels of estrogen increase prolactin production in the anterior pituitary, but the estrogen also inhibits the effect of prolactin on mammary glands. The abrupt decrease of estrogen and progesterone after birth removes this inhibition and milk production begins. Release of milk is controlled by the hormone oxytocin. An infant nursing stimulates the continued creation of prolactin and starts oxytocin release. Oxytocin stimulates the contraction of cells that surround the milk, leading to the ejection of the milk.
Explain the role of dietary fibre in digestion
The rate of transit of materials through the large intestine is positively correlated with the fibre content. Fibre is non-readily digestible material, and increases the mass of material passing through the intestines. This helps prevent constipation because it draws water into the intestine, which speeds movement of fecal matter. Fibre may also reduce bowel cancer, haemorrhoids and appendicitis, and reduce appetite to prevent obesity, absorption of sugars can be slowed preventing type II diabetes.
Explain the regulation of the ventilation rate.
The rate of ventilation is controlled by the respiratory control centre in the medulla oblongata in the brainstem. Two sets of nerves travel to the lungs from here. The intercostal nerves stimulate the intercostal muscles of the thorax and the phrenic nerves stimulate the diaphragm. When the lungs expand after stimulation by these nerves, stretch receptors in the walls of the chest and lungs send signals to the respiratory centre which triggers a cessation of the signals leading to inspiration until the animal exhales. A new signal is then sent.
Give an example of a receptor-hormone complex.
The receptor-hormone complex promotes the transcription of specific genes. An example of this is the steroid hormone calciferol. Calciferol crosses the intestinal cell membrane and binds to a receptor in the nucleus of the cell. The complex effects expression of the calcium transport protein calbindin, allowing for the absorption of calcium from the intestine.
Explain how the contraction of the ventricle is coordinated after passing through the AV node.
The signal needs to be conducted rapidly after passing through the AV bundle, in order to ensure the coordinated contraction of the ventricle. The AV bundle receives the impulse from the AV node and conducts the signal rapidly to a fork that splits into the right and left bundle branches. The branches connect to Purkinje fibres at the base of the heart, these fibres conduct the signal even more rapidly to the ventricles.
What is the function of the sinoatrial node?
The sinoatrial node (often referred to as the pacemaker) is a collection of specially structured cardiac cells that spontaneously initiate action potentials without stimulation from other cells. Thanks to gap junctions the action potential quickly spreads across the entire atrium causing the atria to undergo systole (contraction).
Describe the adaptations of the villus epithelium cells.
The structure of cells in the epithelium of the villi is adapted to the absorption of food. -Epithelial cells on covering the villus adhere to each other ensuring that most materials pass through epithelial cells on the way to the blood stream -Surface membrane of lumen has many microvilli, created a brush border, increasing surface area for absorption -Many mitochondria in epithelial cells to power active transport -Many pinocytic vesicles due to absorption of some food by endocytosis -In epithelial cells, the side facing the lumen (apical surface) has different types of proteins to help with transport from the side facing the blood vessels (basal surface)
Explain the relation between cholesterol and heart disease.
There has been research showing a correlation between high levels of cholesterol in blood plasma and an increased risk of coronary heart disease(CHD). -Only low-density lipoprotein is implicated in CHD -Reducing cholesterol consumption has very little effect on blood cholesterol levels -The liver can synthesize cholesterol, so dietary cholesterol is not the only source -Genetic factors are more important than dietary intake -Positive correlation between intake of saturated fats and of cholesterol, so maybe its the sat fats, not the cholesterol, that caues risk of CHD
What are some features of Purkinje fibres that allow them to conduct signals at such a high speed?
They have relatively fewer myofibrils They have a bigger diameter They have higher densities of voltage-gated sodium channels They have high numbers of mitochondria and high glycogen stores
What is thrombosis? What are the consequences?
Thrombosis is the buildup of plaque, caused by excess levels of lipids and cholesterol in the blood, that becomes serious enough where a clot is formed and blood flow through an artery is blocked. If this occurs on the surface of the heart the consequence can be a heart attack as the heart is deprived of sufficient oxygen. Another consequence is hypertensino
What are some variables that affect heart rate?
Variables that affect heart rate that are good to investigate are: type of excersize, intensity of exercise, recovery from exercise, relaxation, body position, breathing and breath holding, exposure to a cold stiumuls and facial immersion in water.
What is vitamin C deficiency and why does it happen?
Vitamin C, also known as ascorbic acid, is needed to synthesize collagen fibres in body tissues such as skin and blood vessel walls. Humans cannot synthesize ascorbic acid so it must be ingested. Without it humans get scurvy. Scurvy only happens in us and few other mammals because most mammals have the enzyme needed for abscorbic acid synthesis.
What are the causes of jaundice?
When the liver breaks down red blood cells, a pigment is produced called bilirubin. Buildup of bilirubin causes jaundice. In adults, liver problems that contribute to jaundice can be caused by alcoholism, liver diseases and blood diseases.
Explain the use of artificial pacemakers to regulate heartbeat.
When the sinoatrial node malfunctions, patients are fitted with a pacemaker. It essentially maintains the rhythmic beating of the heart by mimicking the sinoatrial node's ability to send out a stimulus. Pacemakers can either provide a regular impulse or disarge only when a heartbeat is missed so that it beats normally.
Explain vitamin D deficiency in humans
Without sufficient vitamin D the body cannot absorb enough calcium from food in the gut. The consequence is osteomalacia. Osteomalacia is inadequate bone mineralization due to calcium salts not being deposited or being reabsorbed, so bones soften. In children, osteomalacia is called rickets.
How do you measure the energy content of food?
You burn the food then use this formula: Energy content of food ( J g⁻¹) = temp rise (C) x water volume (ml) x 4.2J ------------------------------- mass of food (g)
What is malnutrition?
Malnutrition is a deficiency, imbalance, or excess of specific nutrients in the diet.
Explain how protein pumps can be inhibited by drugs.
Many diseases are worsened by the release of stomach acid. Acidity in the stomach is produced by a proton pump called the "H⁺, K⁺-ATPase". The pump uses 1 ATP to exchange 2 protons from the cytoplasm for two potassium ions in the lumen. Treating stomach acid diseases is done by proton pump inhibitors (PPIs). Each PPI permanently bonds to one pump, reducing its activity. They're not permanently effective because proton pumps are eventually replaced.
What happens to ingested materials that are not absorbed?
Materials that have been ingested but then not absorbed are egested (pooped out). An example of a material like this is dietary fibre.
What are the four chemical groups of essential nutreints?
Minerals - specific elements such as calcium or iron Vitamins - chemically diverse carbon compounds needed in small amounts, such as ascorbic acid and calciferol Amino acids - some of the 20 are not able to be synthesized by humans but obviously necessary for protein creation Fatty acids - essential for the same reason, example: omega-3 fatty acids
Explain the differences between the dissociation curves for hemoglobin and myoglobin.
Myoglobin is a specialized oxygen transport protein found in muscles. It has a much higher affinity for oxygen and only releases oxygen when the pO₂ is quite low, for example during heavy exercise. This is because hemoglobin has four chains with four heme groups but myoglobin has only one. Release of each O₂ from hemoglobin makes the hemoglobin release subsequent O₂ more rapidly.
What is nutrition?
Nutrition is defined as the supply of nutrients
What health issues does obesity make more likely?
Obese persons are more likely to experience hypertension (high blood pressure) and type II diabetes
What is obesity?
Obesity is the excessive storage of fat in adipose tissue, due to the prolonged intake of more energy in the diet than is used in cell respiration.
Explain the oxygen dissociation curves.
Oxygen dissociation curves show the affinity of hemoglobin for oxygen. Hemoglobin is an oxygen transport protein found in blood. The degree to which oxygen binds to hemoglobin is determined by the partial pressure of oxygen (pO₂) in blood.
What are the consequences of jaundice?
People with jaundice experience discoloration in the skin and eyes due to the deposition of excess bilirubin (pigment) in the skin tissues. Jaundice is actually a symptom, not really a disease.
