Option H - Human Physiology

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Option H: Further Human Physiology

H.1.1 State that hormones are chemical messengers secreted by endocrine glands into the blood and transported by the blood to specific target cells.

	Hormones are substances secreted by the glandular cells of the endocrine glands to act on the specified target organs or tissues to stimulate or inhibit specific biological reactions.

H.1.2 State that hormones can be steroids, peptides, and tyrosine derivatives, and provide one example of each. Steroids- testosterone and estrogen Peptides- endorphins Tyrosine derivatives- ___

H.1.3 Distinguish between the mode of action of steroid hormones and peptide hormones Steroids enter cells and affect genes directly. Peptides bind to receptors in the membrane which causes the release of a secondary messenger inside the cell.

H.1.4 Draw a diagram of the hypothalamus and the pituitary gland

H.1.5 Explain the control of thyroxin secretion by negative feedback. A certain stimuli (cold or stress) go to the hypothalamus then goes down to the thyroid-stimulating hormone-releasing hormone to the anterior pituitary. Low-level thyroid hormone in blood stimulates the anterior pituitary which activates the thyroid-stimulating hormone, which stimulates the thyroid to the thyroid hormones. The thyroid hormones stimulate metabolism and produce growth. When the level in the blood increases above normal the thyroid hormones inhibit the anterior pituitary. Some inhibition goes to the hypothalamus.

H.1.6 Explain the control of ADH secretion by negative feedback

H.2 Digestion

H.2.1 State that digestive juices are secreted into the alimentary canal by glands including salivary, stomach wall, pancreas, and wall of small intestine. In the mouth, saliva is secreted into the oral cavity. In stomach walls the epithelium secrets gastric juices. Pancreatic juices rich in bicarbonate ions are secreted in the pancreas. The mucosa in the small intestines secretes mucin.

H.2.2 Draw the structural features of exocrine glands including secretory cells grouped into acini and ducts.

H.2.3 Explain the structural features of exocrine gland cells as seen in electron micrographs. A group of cells surround an empty space and the hormones from the cells move into the empty space and then to the duct. The hormones are then transported to the destination including the duodenum, and to other parts in the digestion process. The alignment of exocrine cells around an empty space increased the surface area for the hormone secretion.

H.2.4 State the contents of saliva, gastric juices and pancreatic juice Saliva- 98% water, but it contains many important substances, including electrolytes, mucus, antibacterial compounds and various enzymes Gastric juices-

Pancreatic juice- contains a variety of enzymes including trypsinogen, elastase, chymotrypsinogen, carboxypeptidase, pancreatic lipase, and amylase. Pancreatic juice is alkaline in nature due to the high concentration of bicarbonate ions. This is useful in neutralizing the acidic gastric acid, allowing for effective enzymic action. Pancreatic juice secretion is regulated by the hormone secretin, which is released by the duodenum upon detection of proteins and fats

H.2.5 Outline the control of digestive juice secretion by nerves and hormones.

• When stimulated by the presence of food, peristaltic movement begins in the esophagus. • Due to this movement of food, nerves in the esophagus are stimulated by a stretch reflex and send impulses that begin the release of gastrin from cells in the lower region of the stomach. • The gastrin circulates in the blood until it reaches the cells in the upper part of the stomach wall • When the gastrin comes in contact with these cells, it stimulates the secretions and movements of the stomach. When the contents of the stomach become too acidic, gastrin release is inhibited. This is an example of negative feedback. Neural reflexes • Salivation first stimulated by sight or smell of food (neural reflex). • Swallowing at back of mouth- tactile touch (neural reflex) • Gastrocolic Reflex- bowel movement • Intrinsic nervous system- ex. Salivation and swallowing Hormones and Digestive Functions • Secretin- Type of hormone. Causes pancreas to secrete digestive juices (solution rich in bicarbonate ions) • Mucosa- secretes cholecystokinin, stimulates gallbladder to release bile and pancreas to release digestive enzymes. • Stomach secretes the hormone Gastrin into the blood.

H.2.6 Outline the role of membrane-bound enzymes in the surface cells of the small intestine in completing digestion. Some enzymes are immobilized in the surface membrane of cells on the surface of the intestinal villi. These enzymes continue working even if the cell is rubbed off the villus and mixed into the intestinal contents.

H.2.7 Explain why cellulose remains undigested in the human alimentary canal

H.2.8 Explain why pepsin and trypsin are initially synthesized as inactive precursors, and how they are subsequently activated.

H.2.9 Outline the action of lipid digestion in a hydrophilic medium and the role of bile in overcoming this problem.

H.2.10 Role of bile Lipid digestion is a problem because it has to occur in a lipophobic medium. Bile solves this dilemma by emulsifying fat.

" bile is secreted from the liver through the hepatic duct " fat is hydrophobic " enzymes that digest fat (lipases) are water soluble and must do their work in an aqueous medium " bile stabilizes tiny droplets of fat so they cannot gather into large globules " one end of bile molecule is soluble in fat (lipophillic/hydrophobic) " other end of bile molecule is soluble in water (hydrophillic/lipophobic) " bile molecules bury lipophillic ends in fat droplets, leaving lipophobic ends sticking out " they prevent fat droplets from sticking together " these very small fat particles are micelles " small size maximizes surface area exposed to lipase action Summary You've got fat, which globs together and doesn't mix with water. Bile comes in and separates the fat by grabbing on to some fat with one end, and repelling the rest of the fat with the other end. These micelles are little and individual, so that the digestive enzymes can surround them and make contact with more fat.

H.3 Absorption of Digested Foods

H.3.1 Draw a portion of the ileum (transverse section) as seen under a light microscope

H.3.2 Explain the structural features of an epithelium cell of a villus as seeni n electron micrographs including microvilli, mitochondria, pinocytotic vesicles and tight junctions

H.3.3 Explain the mechanisms used by the ileum to absorb and transport food, including facilitated diffusion, active transport and endocytosis.

H.3.4 List the materials that are not absorbed and are egested. Cellulose- cannot be digested because most animals cannot produce cellulases which hydrolyze cellulose Lignin- wood fiber cannot be digested because it is too strong Bile pigments- body gets rid of excess after needed materials are absorbed Bacteria- only founding large intestines and cannot by digested Intestinal cells- some are bulled off by material that is being egested

H.4 Functions of the Liver

H.4.1 Outline the circulation of blood through the liver tissue including the hepatic artery, hepatic portal vein, sinusoids, and hepatic vein.

This is the order in which the blood travels through the liver tissue: • Hepatic artery • Hepatic arteriole • Sinusoids: nutrients collected or given off • Central Vein • Hepatic veinuols • Portal vein • Hepatic vein The difference in structure of the sinusoids and the capillaries is: Capillaries are small tubes between termination of arteries and start of veins. Sinusoids are larger tubes that lead from the portal vein to the hepatic vein. Blood almost always travels from artery to capillary to vein. AN exception to this sequence occurs in the hepatic portal system, which delivers blood-rich in nutrients to the liver. Blood is conducted to the small intestine by the superior mesenteric artery. Then as it flows through capillaries within the wall of the intestines, blood picks up glucose, amino acids, and other nutrients. This blood passes into the mesenteric vein and then into the hepatic portal vein. Instead of going directly back to the heart (as most vein would), the hepatic portal vein delivers nutrients to the liver. The hepatic portal vein gives rise to an extensive network of tiny blood sinuses in the liver. As blood course through the hepatic sinuses, liver cells remove nutrients and store them. Eventually liver sinuses merge, forming hepatic veins, which deliver blood to the inferior vena cava. The hepatic portal vein contains blood that, although laden with food materials, has already given up some of its oxygen to the cells of the intestinal wall. Oxygen-rich blood is supplied to the liver by the hepatic artery.

H.4.2 Explain the need for the liver to regulate levels of nutrients in the blood. -directs traffic of nutrients used in energy metabolism -when nutrients abundant, liver stores as glycogen and fat -synthesizes plasma proteins from amino acids -nutrients decline, puts glycogen and fat back in blood -can convert monosaccharides to glycogen and fat or vice verse -pyruvate and lactate can be converted to glucose (gluconeogenisis_ -controls fat metabolism -insulin makes liver absorb excess glucose -liver turns glucose to energy, glycogen, and triglycerides -turns chlyomicrons (fat in blood) to triglycerides, then VLDL -turns amino acids to proteins to circulating proteins Summary Liver stores nutrients when abundant Releases when deficient Stores in different form than found in bloodstream Must change nutrient forms when they enter and exit

H.4.3 Outline the role of the liver in the storage of nutrients including carbohydrate, iron, the vitamins retinol and calciferol.

The liver cells store nutrients more than other cells because of their constant exposure to a high concentration of nutrients. They store carbohydrates as glycogen for energy reserve, iron from broken down hemoglobin, retinol for night vision (vitamin A), and calciferol so the body can use calcium (vitamin D). They do this because when these nutrients are digested, they are very useful to the body and so cannot be wasted through excretion. Thus, the liver cells store them as accessible substances when the body lacks them.

H.4.4 Describe the process of bile secretion. Bile is produced and secreted by the liver. It is an alkaline, mucous fluid containing bile pigments (which are excretory products formed from the breakdown of haemoglobin from worn-out red blood cells) biliverdine and bilirubin. Bile also contains bile salts that are sodium glycocholate and sodium taurocholate which are reclaimed by the liver from the blood. These salts are reused in lipid absorption. Bile pigments and salts are produced by the liver cells and then secreted into bile canaliculus (small spaces in the membranes of the hepatocytes). The canaliculi flow into the bile duct and into the gall bladder, where it is released by muscular contractions into the duodenum, under the control of hormones involved in digestion. When food enters the duedenum enters the duodenum, the sphincter oddi relaxes and allows bile to be secreted into the small intestine.

H.4.5 Describe the process of erythrocyte and haemoglobin breakdown in the liver including phagocytosis, digestion of globin, and bile pigment formation.

Erythrocytes (red blood cells), after about 4 months, are destroyed by Kupffer's cells (phagocytic) in the liver. Hemoglobin is converted to a yellow pigment (bilirubin), the iron is stored and proteins (globin) are broken down into amino acids. Bilirubin is transferred to the bile duct, released into the intestines and converted by bacteria to a yellow pigment that gives the characteristic color of feces.

H.4.6 State that the liver synthesizes plasma proteins and cholesterol.

The liver synthesizes large quantities of cholesterol and phospholipids. These proteins are blood-clotting agents prothrombin and fibrin, and plasma albumin and globulin, which includes the antibodies. The liver cells break down amino acids and other nutrients which then constitute the blood proteins. Some of this is packaged with lipoproteins and made available to the rest of the body. The remainder is excreted in bile as cholesterol or after conversion to bile acids. Hepatocytes are responsible for the synthesis of most of the plasma proteins. The liver synthesizes albumin, the main plasma protein, almost exclusively.

H.5 The Transport System

H.5.1 Explain events of cardiac cycle o Atrial Systole (contraction) o C. cycle begins with the contraction of atrium wall, this happens when ventricle is 70% full. Blood is pumped from the atrium through the atrio-ventricular valves into the ventricle. o Ventricular Systole (contraction) o The ventricle has to be filled to capacity for the ventricular systole to begin. o Contraction of wall causes a rapid increase in the ventricle pressure, which causes the atrio-ventricle valves to close. Once ventricular pressure is higher than that of the aorta, the semi-lunar valves are forced to open, pumping blood from the ventricle to the aorta. o While the ventricle is contracting, the atrium is relaxing, allowing blood flow from the pulmonary veins. o Ventricular Diastole (relaxation) o Relaxation of the ventricle causes the pressure to fall below that of the aorta, which allows the semi-lunar valves to close. (Resulting in vibrations which are the cause of the second heartbeat) o Once pressure of ventricle falls below that of the atrium, the atrio-ventricle valve opens, refilling the ventricle. o With both the atrium and ventricle relaxed, blood continues to flow from the pulmonary veins into that of the atrium and then the ventricle.

H.5.2 Analyze pressure of Left; Atrium, Ventricle, and the Aorta. o The change in volume of the atrium is due to the blood flow in from the pulmonary veins which bring blood to the heart form the lungs (which are a ‘short’ distance away). o The walls of the Left Ventricle are thicker because it is required to pump blood received from the lungs (oxygen rich blood) to the rest of the body. The change in pressure of the Left Ventricle is due to the contraction of the walls to pump the blood received to farther away regions than the lungs (like the R ventricle).

H.5.3 Outline the Control of the heartbeat in terms of the pacemaker (SA node) Outline mechanisms that control the heartbeat o The pacemaker of the heart is called the Sinoatrial (SA) node, which initiates each impulse. Located in the right atrium. The impulses spread out in all directions of the heart but are prevented from spreading directly into the walls of the ventricles be a layer of fibrous tissue. o Impulses from the SA node travel to the atrioventricular (AV) node (located in the wall of the right atrium). o Impulses are sent from the AV node along two bundles of connecting fibers the base of the heart. Narrower bundles (Purkinje) carry the impulses to all parts of the walls of the ventricles.. o Sinoartirial Node (SA node) – pacemaker of the heart, sends out impulses. o Atrioventricular Node (NA node) – receive impulse from the SA node. o Connecting Fiber Bundles – act as messengers of impulses between NA node and Perkinje. o Perkinje – narrower connecting fiber bundles which spread the impulse through out the heart, resulting in ventricle contraction.

H.5.4 Arteriosclerosis o The most common cause: atherosclerosis  Build up of plaque inside arteries o Plaque consists of:  Cholesterol  Calcium  Fatty acids  Fibrin

H.5.5. Heart Disease Factors & Coronary Disease o Contributing Factors o Smoking o Increase blood pressure o Increases cholesterol o Sedentary lifestyle o Obesity o Stress o Blood clotting factors o Sex hormones o Estrogen is protective o Female risk after 65 o Birth Control Pills – high dose (50 mgs o Increases chances o Being a smoker greatly increases the risk

H.5.6 Formation of Tissue Fluid and Lymph in body tissues o Tissue fluid is formed from the blood plasma in blood capillaries, and can be found in the spaces between cells. o Most of it is reabsorbed into the capillaries, what is not drains into ‘blind-ended’ tubes called lymph capillaries. o The fluid is then called lymph and drains through to the lymphatic system entering the blood system in the veins near the heart.

H.5.7 Transport Functions of the lymphatic system o The lymphatic system is responsible for the transportation of lipids such as triglycerides and cholesterol. o Lymph capillaries in the villi of the small intestine absorb droplets of lipids that were taken in from the digested food in the small intestine.

H.6 Gas Exchange H.6.1 Define o Partial Pressure- (Air is 20.9%) the pressures exerted by each of the gases in a mixture of gases. o Sea level: atmospheric pressure= 760 mm/Hg o Barometric pressure is 760 mm/ Hg o Higher elevation = lower barometric pressure

H.6.2 Oxygen dissociation curves of adults and fetal hemoglobin o The pressure saturation of hemoglobin with oxygen is shown on an oxygen dissociation curve. o Myoglobin has a higher affinity for oxygen than hemoglobin • At moderate partial pressures of oxygen, adult hemoglobin releases oxygen and myoglobin binds it. o The release of oxygen from myoglobin delays the onset of anaerobic respiration in muscles during vigorous exercise. o Hemoglobin is an S-shaped curve • Hemoglobin has four heme groups –each attached to different globins that interact with each other. o As oxygen molecules dissociate from hemoglobin, conformational changes occur which make it easier for other oxygen molecules to dissociate.

H.6.3 How is carbon dioxide carried by blood o Carried as dissolved CO2 in the plasma o Combines with hemoglobin o Rest combines with water to form carbonic acid

        *This occurs in the RBC’s because they contain carbonic anhydrase

o Why doesn’t H+ cause cell to become more acidic?  The H+ adds onto the hemoglobin which buffers them. Plasma proteins also act as buffers.  “Chloride Shift”- when HCO3- diffuses out, a carrier protein (antiport) moves a CL- in. (keeping the charges balanced)

        * Hemoglobin picks up CO2 & H+ when cells release CO2.

H.6.4 Role of Bohr shift in the supply of oxygen to respiring tissues o Result of pH function of hemoglobin o As blood picks up acidic metabolites (lactic acid, fatty acids and CO2) its pH decreases. o Oxygen dissociation curve shifts to the right.

H.6.5 Explain how/ why ventilation rate varies with exercise o Rate of aerobic respiration in muscles rises so there is an increase in the amount of CO2 entering the blood (concentration rises) o Chemosensors are cells that monitor blood pH and concentrations of oxygen and carbon dioxide in the blood.  Send nerve impulses to the part of the medulla of the brain that contols the ventilation rate (Breathing centres). o If the concentration of carbon dioxide is the blood rises and the blood pH falls below their normal lvels, the breathing centre increases the rate of inspiration and expiration. (nerve impulses are sent to diaphragm and intercostal muscles telling the to increase relaxation rate) o Increase in ventilation rate helps to remove CO2 from the body; helps increase the rate of oxygen uptake. o After exercise, the level of CO2 in the blood falls, the pH of blood rises and the breathing centres cause the ventilation rate to decrease.

H.6.6 Outline the possible causes of lung cancer and asthma and their effects on gas exchange o Lung Cancer  Inhaling carcinogens can cause lung cancer.  Most from cigarette smoke  Atmospheric pollution can also cause lung cancer.  Miners and metal refiners suffer an increased risk, because metal ores contain radioactive substances  Lung cancer is treated by removing prt of the entire affected lung, which effects the gas exchange. o Asthma  During asthma attacks, the muscles in the wall of the bronchi contract excessively, narrowing the bronchi.  Ventilation becomes a struggle and the gas exchange is reduced.  Is a allergic reaction, and can be caused by • Dust mites • Pollen • Pets • Some fungi • Exercise • Cigarette smoke • Exposure to cold air or sudden temperature change • Excitement or stress • Respiratory infections  Living in very clean homes increase the risk • Without enough pathogens to fight, the immune system starts to react against harmless substances, causing allergies to develop.  Is a reversible obstructive lung disease  Can be life threatening

H.6.7 Explain the problem of gas exchange at high altitudes and the way the body acclimates o The partial pressure of oxygen at higher altitude is lower that at sea level o Hemoglobin may not become fully saturated (with oxygen) when passing through the lungs, so tisues of the body may not be adequately supplied with oxygen o Mountain sickness can develop o Muscular weakness, rapid pulse, nausea and headaches o During acclimatization the ventilation rate increases o Extra red blood cells are produced, increasing the hemoglobin content of the blood (hemoglobin is located in red blood cells). o People who are native to high altitudes show other adaptations, including a high lung capacity with a larger surface area for gas exchange