Physiology Verbal Exam PDF

Osmotic pressure is the minimum pressure which needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane. Functions of blood plasma proteins Create oncotic pressure in the blood plasma, which ensures normal exchange of water and salts in the ca...

Osmotic pressure is the minimum pressure which needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane. Functions of blood plasma proteins Create oncotic pressure in the blood plasma, which ensures normal exchange of water and salts in the capillaries. (eg., mechanism of edema) Protective role- especially for globulins. Help to keep blood pH relatively constant. Plasma proteins transport various substances in the blood. The only protein reserve in the body! Blood plasma osmotic pressure It is determined by the osmolar concentration of dissolved salts and ions in the blood plasma. Provides a pH level Provides irritability Is relatively constant Equal in intracellular and extracellular environment. Determines the flow of solvent through the semipermeable membranes, keeping the water in the extracellular fluid. Maintained by the excretory organs - kidneys, sweat glands. Any changes are detected by osmoreceptors. Oncotic blood pressure... Is made up of proteins in the blood plasma. !!!Define: in capillaries - filtration and reabsorption (attracting H2O). pH level (acts as a buffer). transport (Fe, lipids, hormones, vitamins, etc.) protective function (immunity, coagulation factors, etc.) Blood colloid osmotic pressure... It is determined by blood plasma proteins (1/220) together with inorganic electrolytes. main function is to control blood plasma filtration and reabsorption processes in capillaries Capillaries are blood vessels in which metabolic processes take place 56. Ticket 111. Nephron – the basic structural and functional unit of the kidney. Blood circulation particularities in kidneys. Most of the functions of the kidneys occur in their tiny nephrons. Nephrons filter the blood and modify the filtered fluid as it passes through the renal tubules. This fluid then leaves the nephron and drains into the tubules of the collecting system (which are not considered part of the nephron), where it is further modified until it finally becomes urine. The kidneys contain two types of nephrons: 1. Cortical (80% of nephrons) located primarily in the renal cortex have very short nephron loops that either just dip into the superficial part of the renal medulla or never leave the cortex 2. Juxtamedullary located close to the boundary between the renal cortex and the renal medulla has a long nephron loop that burrows deeply into the renal medulla The nephron has two main divisions: the renal corpuscle the renal tubule Both structures are composed of multiple parts. Kidney blood supply The kidneys receive about 20% of the cardiac output. 90% of the arterial blood received goes to kidney cortex, 10% - to the medulla. The kidneys receive blood from the renal artery (a.renalis), which branches from the abdominal aorta. Peculiarities (a.renalis): large diameter, few branches, short pressure almost the same as in the aorta The first capillary network: forms glomerulus is called “magic network ”(rete mirabile). There is no gas exchange in glomerulus between blood and tissue, but from blood plasma through the capillary wall primary urine or ultrafiltrate is filtered, with a composition similar to that of plasma composition. The secondary capillary network is formed by peritubular capillaries surrounding glomerular tubule system ensuring reabsorption and secretion, as well as the exchange of gas between the blood and tissues 112. Intestinal juice. Its composition. The regulation of the secretion of intestinal juices. Differences between digestion and absorption processes in small intestine and large intestine. SMALL INTESTINE JUICE (pH 7.5) Main components: Proteases: proteins till amino acids Enterokinase - trypsinogen into active trypsin Aminopeptidases – splits amino group Dipeptidases - hydrolyze bound pairs of amino acids, called dipeptides Nucleases - cleave the phosphodiester bonds between the nucleotide subunits of nucleic acids Lipases: fats till glycerin and fatty acids Lipase – splits lipids (main) Amylases: carbohydrates till monosaccharides α-Amylase – starch hydrolyzing Maltase - hydrolyzes maltose to simple sugar glucose Lactase - hydrolysis of the disaccharide lactose into galactose and glucose Sucrase – catalyze the hydrolysis of sucrose to fructose and glucose The lining of the small intestine contains glands that produce intestinal juice (there are 10 000 glands in duodenum per 1cm3 ) The chemical processing of food ends with the intestinal juice. In more further parts of the small intestine, reduces the amount of enzymes and increases the production of mucus. humoral regulation of digestive juice Secretion Secretion of small intestine juice o Protein splitting products o Carbohydrate splitting products o Gastric juice In the large intestine mainly occurs: water and salt reabsorption. a) chemical processing of food with «imported» enzymes (at the beginning of the large intestine). The pH of the chyme is important to match the pH when enzymes act! b) biologic processing of food with the help of the large intestine microflora: - Fermentation processes of undigested and unabsorbed carbohydrates. - Putrefaction processes of undigested and unabsorbed proteins. Synthesis of vitamins (B6, K, biotin, folic acid - PP). 57. Ticket 113. By help of what and how is provided blood circulation in closed circuit? Characterize blood circulation levels. Right side of the heart → pulmonary circulation → left side of the heart → systemic circulation Blood, like all fluids, flows from the highest pressure to the lowest, (from the aorta to the capillaries and then to the venae cavae). Pressure is provided by the heart !!! In a healthy animal, the blood flow corresponds to the blood supply to the heart. Capillaries- supply blood to the tissues. By function, they are called metabolic blood vessels. Veins- regulate blood flow to the heart. By function, they are capacitance or volume blood vessels. 1. Small or pulmonary circuit: is a relatively low pressure circuit, in which gas is exchanged between capillaries ↔ lung alveoli. Contact with the external environment. 2. Large or systemic circuit: is a high pressure circuit Capillaries ↔ body’s cells (the exchange of nutrients and gases) Contact with the internal environment  The functional unity in the cardiovascular system forms three levels of blood circulation: Level 1 – systemic hemodynamics (connected in series) renal artery Level 2 – blood circulation in organs (connected in parallel) arcuate artery Level 3 – microcirculation (connected in parallel, part is closed) glomerular artery 2. Thyroid hormones. Calcitonin (thyrocalcitonin), it is antagonist to parathormone (PTH) and it regulates the level of calcium and phosphorus in blood. 114. The physiological roles of thyroid hormones. Calcitonin (thyrocalcitonin) ⎼ independent from adenohypophysis Regulates the level of calcium and phosphorus in the blood ○ Released from parafollicular cells (C cells) when blood calcium levels are high ○ Antagonist to parathormone (PTH) Inhibits osteoclasts activity and activates osteoblast activity ➜ Ca and P enter the bones Reduces Ca absorption in the intestines Signals the kidneys to reabsorb less calcium ➜ more calcium excreted in the urine ➜ Decreases blood Ca level Triiodothyronine (T3) and thyroxine (tetraiodothyronine, T4) ⎼ secretion is adenohypophysis dependent Their synthesis requires iodine (from food and water) = iodine containing hormones Roles/functions: Especially T3 increases the intensity of cell’s metabolism: both protein degradation and synthesis ○ Basal metabolism can double ○ Number and size of mitochondria increase ➜ increased ATP production T3 is 5 times more active than T4: both enter the target cells, but T4 is converted to T3 and only then used ➜ increasing the intensity of metabolism in it. When energy consumption must be restricted (sickness, starvation), the T4 to T3 conversion is inhibited and metabolism becomes slower. Lack of thyroid hormones = hypothyroidism: Reduces the basal metabolism (metabolic processes that provide only vital functions) Hypothermia Very low mental activity Thyroid hypertrophy Myxedema (severe hypothyroidism) Increased thyroid hormones = hyperthyroidism: The basal metabolism increases Hyperthermia (increased/unnecessary nutrient consumption ➜ increased heat producuction)  Tachycardia Weight loss CNS cells become agitated ➜ the animal becomes nervous In humans – high mental activity 58. Ticket 115. What is the meaning of mineralocorticoids? Where are they produced? How is regulated their secretion? Aldosterone and deoxycorticosterone. The most active is aldosterone: Regulates the reabsorption of electrolytes from the nephron tubules (mainly Na+ and K+) ➜ this lead them to also regulate & maintain blood pressure and pH Stimulates Na+ reabsorption ➜ indirect stimulation of water reabsorption (Na+ attracts water) Reduces K+ reabsorption ➜ K+ removed in urine From AI because no mention in materials: deoxycorticosterone mainly works as a precursor for aldosterone and has similar functions These corticosteroids are prodused in the zona glomerulosa of the adrenal gland cortex Secretion is not primarily adenohypophysis dependent (like e.g. glucocorticoids) but mainly increased by: 1. Renin–angiotensin system 2. Increased plasma concentration of potassium 3. Decreased plasma concentration of sodium (closely connected with renin-angiotensin system) 4. Lastly also the ACTH (adenocorticotrophic hormone) stimulation ACTH is secreted from the anterior pituitary gland in response to corticotropin- releasing hormone (CRH) from the hypothalamus 116. Describe the direct and indirect regulation of carbohydrate metabolism? The meaning of carbohydrates: Energy source, Cell component (glycoproteins), During muscle contractions and relaxation (provide energy), Are needed for action of myocardium, Are needed for the action of the nervous system (there are almost no glucose reserves). For normal lipid and protein oxidation processes Carbohydrate metabolism in the body In GI carbohydrates are split by amylases till monosaccharides (glucose) → are absorbed into blood → to all body and liver:  the most part – for energetic processes the rest – in liver and muscles as glycogen or are used for fat synthesis Glycogen in liver can be synthesized from: Glucose Glycerin Fatty acids Amino acids Volatile fatty acids ◦ It proves the mutual connection between protein, lipid and carbohydrate metabolism. ◦ Cellular metabolism of carbohydrates in non-herbivores is the metabolism of glucose! ◦ Glucose is the basic metabolic fuel for monogastric animals ◦ Important to keep glucose levels stable in the body ◦ Usually, glucose is the only type of fuel used by the CNS ◦ In herbivores, cellulose takes up most of the carbohydrate intake! ◦ Ruminants - most carbohydrates converted to volatile fatty acids (VFAs) by microbial enzymes in forestomachs Monogastric herbivores – conversion of carbohydrates to VFAs in the large intestine ◦ The liver processes most of the glucose (received via the portal vein) ◦ Some is converted to lipids → stored in adipose tissue ◦ Even though a lot of glucose is absorbed → glucose levels are never very high 59. Ticket 117. Adrenal glands, their synthesized hormones, meaning? Corticosteroids: So these are mineralocorticoids (zona glomerulosa), glucocorticoids (zona fasciculata) and sex steroids (zona reticularis). Corticosteroid-producing cells contain many mitochondria in which cholesterol is mobilized from low density lipoproteins and used for steroid synthesis. It is complicated multi step process. The regulation of synthesis of all corticosteroids is by adenohypophysis. Zona glomerulosa: Production of mineralocorticoids (aldosterone, deoxycorticosterone) – absolutely necessary for lifesupport! The most active of these is aldosterone, regulate the reabsorption of electrolytes (mainly Na+ , K+ ) from nephron tubules: - By stimulating Na+ and K+ levels The release of aldosterone is regulated by blood levels of Na. For example, ↓ blood Na levels, aldosterone levels ↑ and vice versa.  The synthesis of aldosterone happens due to renin angiotensin system. Zona fasciculata: Produces glucocorticoids. The most active are cortisol (main) and corticosterone. Their main impacts: Stimulate the release of glucose from the liver into the blood and also gluconeogenesis (glucose production) by increasing the breakdown of proteins and fats Suppress allergic reactions in the body (prednisolone, dexamethasone etc.) Suppress inflammatory reactions, especially in connective tissues Reduce the number of eosinophils Increase the body’s resistance to harmful effects (infections, large tissue damage), adaptation processes Increase gastric hydrochloric acid secretion In cows reduce ketones in the blood (used to treat of acetonemia). Zona reticularis: androgens (male), estrogens (female) and progesterone (female), which are similar to sex hormones of gonads. They are important for animals (and humans) till sexual maturity i.e. while gonads do not function. Adrenal cortex sex hormones are “weaker” (have less impact) so when animals are castrated these hormones are unable to counteract the effect of castration. In childhood, the hyperfunction of Zona retuculata promotes the onset of sexual maturity. In adult female individuals, hyperfunction contributes body hair growth, voice changes – it becomes more masculine Regulation: SO HYPOTHALAMO - PITUITARY - ADRENAL AXIS → HPA AXIS Regulation of glucocorticoid secretion happens by principle of adenohypophysis dependent endocrine gland regulation Corticoliberins or corticostatins are produced in hypothalamus. They affect production of corticotropic hormone (↓↑) in adenohypophysis It stimulates production of hormones in adrenal cortex zona fasciculata (note: if there is lack of corticotropic hormone – does not stimulate) ↑ secretion of glucocorticoids happens during stress situations 118. Absorption in the gastrointestinal tract. Absorption of protein, carbohydrates, lipids, water and minerals. Absorption = transfer of substances from GI to the blood or lymph through the epithelial cells. Absorbed: nutrients, mainly in the form of monomers, water, inorganic salts, hormones and drugs. Absorption depends on: 1.The splitting degree of nutrients 2. Absorption surface area  The following factors are important in the absorption process: 1. physical processes – filtration, osmosis, diffusion; 2. active cellular processes involved in the function of epithelial cells. Proteins are absorbed as amino acids. They are phosphorylated by intestinal enzymes (using energy). Animal proteins are better absorbed. In ruminants, amino acids are already absorbed in the forestomachs. Carbohydrates are absorbed as monosaccharides – in the form of glucose, galactose. In ruminants, glucose is absorbed in small amounts in the intestines, as glucose in the forestomachs participates in further fermentation processes and forms volatile fatty acids, which are absorbed into blood from forestomachs. Fats are absorbed mainly as glycerol and fatty acids. Only very well emulsified fats can be absorbed whole. Glycerol is very well absorbed because it is easily soluble in water. Fatty acids – only in complex with bile acid, because in this way a compound is formed that is soluble in water. Absorption of water and minerals is most intense in the large intestine. Absorption depends on the osmotic pressure of the food.. In ruminants, intense absorption takes place in the forestomachs. ○ In the mouth hormonal preparations, alcohol, nitroglycerin. Nutrient absorption does not occur because food is not broken down into monomers and remains in the mouth for a short time. ○ In stomach water, alcohol, NaCl. In forestomachs very intensive absorption processes. Volatile fatty acids, ammonia, CO2, methane, urea, amino acids. ○ In duodenum absorption processes are weak. Carbohydrates begin to absorb slightly. ○ In small intestine absorption processes are the most intensive. ○ In large intestine water, salts, volatile fatty acids for herbivores, monosaccharides, vitamins, as well as protein breakdown products are intensively absorbed 60. Ticket 119. The physiological meaning of proteins? The biological value of proteins? The regulation of protein exchange in the body? Proteins are needed for: 1. Plastic processes - animal growth, development, restoring of body’s tissues and cells 2. Defense reactions – immune substances, antibodies against microorganisms, toxins 3. All enzymes and part of hormones are proteins 4. Proteins transport other chemical substances, for example, in blood protein globin transports hemoglobin, transport CO2, O2 5. energy source for example, by splitting 1g of proteins it releases 4,1kcal of heat  Cows receive about 25% of their daily protein requirement from ruminal microorganisms – protozoa and bacteria With protozoa and bacteria cows get very high quality proteins. All irreplaceable amino acids can be synthesized by ruminal microorganisms by using: Other amino acids, Urea nitrogen, Ammonia nitrogen, Simple non-protein nitrogen compounds (for example, carbamides, ammonia salts) The value of proteins is determined by: the presence of all irreplaceable AmAc: Proteins that contain all essential amino acids are called complete or whole proteins. Proteins that do not contain all essential amino acids are called incomplete proteins. the mutual ratio of irreplaceable AmAc: High biologic value – proteins that contain all essential amino acids AND in the correct ratio (animal origin). Medium high biologic value – proteins that contain all essential amino acids but in the wrong ratio (soy, legumes). Low biologic value have – proteins that do not contain all essential amino acids (plant origin). Liver is of main importance in protein exchange. If there are impaired liver functions, there is also impaired protein exchange. Growing animals as well as animals during lactation are in greater need of well balanced food because of the increased protein formation in their bodies. Amino acids which are not used for synthesis of its own body proteins are deaminated. Deamination (splitting amino group NH2) happens mainly in liver. Amino acids are used for energetic processes or synthesis of fats or carbohydrates but this way of using proteins is irrational and is not economically beneficial. In process of deamination of amino acids is formed ammonia which is a toxic substance. In liver ammonia is transformed to urea which is eliminated from body mainly with urine. 120. Describe the cough and sneezing reflex Sneezing by substances that irritate the mucosa of the nasal cavity. Expiration occurs mainly through the nose. Coughing is similar to the sneezing reflex, only in this case there is irritation of irritant receptors in the respiratory tract in deeper parts – larynx, trachea or bronchi, and when you cough, you exhale through your mouth. Temporary cessation of breathing followed by expiration belongs to respiratory defense reflexes. Reflective bronchoconstriction prevents irritable substances and particles to penetrate deeper into the lungs. The cough reflex 1) the peripheral arm which initiates the reflex following sensory nerve activation, 2) a central component where the reflex is processed in the brainstem and, 3) the efferent arm that causes the cough response after activation of motor nerves. 4) The cough reflex initiates when endogenous or exogenous irritants activate receptors present on sensory nerves in the airways. If this activation reaches a certain threshold, → action potential is produced, → vagus nerve → nucleus tractus solitarius in the brainstem. → motor neurons to the diaphragm, respiratory muscles and larynx → cough response COUGH PHASES: Inspiratory phase – Irritation of cough receptors → vocal cords open more widely → more air enters the lungs – Contraction of external muscles and diaphragm → ↑thoracic cage volume – ↑intrathoracic pressure Compressive phase – Epiglottis and vocal cords close, trapping air within the lungs → more ↑intrathoracic pressure Expiratory phase – Internal intercostal and abdominal muscles contract → ↓thoracic cage volume – Vocal cords relax, epiglottis opens → releases pressure from lungs → foreign material expelled Sneezing reflex: Occurs when irritant receptors in the upper respiratory tract are stimulated (esp. nasal cavity) Little is known about the exact mechanism Consists of two phases: Nasal/sensitive phase: Stimulation of irritant receptors in the nasal mucosa by chemical or physical irritants Sensory information conducted by the trigeminus nerve to the sneezing center in the medulla oblongata Efferent/respiratory phase:  Begins once a critical number of inspiratory and expiratory neurons have been recruited Eyes are closed Deep inspiration, epiglottis closed → ↑intrapulmonary pressure Epiglottis opens and dilates, tongue moves upwards → explosive exit of air through the mouth and nose 61. Ticket 121. What are the functions of the spinal cord? How are expressed its dysfunctions? The lower part of the CNS. Very important for maintaining the homeostasis. Ex., all sensory nerve fibers (afferent) go into spinal cord through posterior roots. In central part grey matter (centers), in outer part - white matter (made of neuron axons) White matter - axon bundles with myelin - made of proteins and lipids Gray matter - unmyelinated neurons The spinal cord extends from the foramen magnum where it is continuous with the medulla to the level of the first or second lumbar vertebrae. It is a vital link between the brain and the body. White matter's job is to conduct, process, and send nerve signals up and down the spinal cord. Damage to the white matter of your brain or spinal cord can affect your ability to move, use your sensory faculties, or react appropriately to external stimuli. Some people with damaged white matter suffer deficits in reflexive reactions. Function of White Matter Long thought to be passive tissue, white matter actively affects how the brain learns and functions. While grey matter is primarily associated with processing and cognition, white matter modulates the distribution of action potentials, acting as a relay and coordinating communication between different brain regions. Young bain can reroute the damaged white matter Spinal shock: Disappear reflexes that are regulated through the brain receiving information from the spinal cord. Below the damaged area occurs atony (lack of tone) The sensations disappear, because the sensations are transferred through the spinal cord. Spinal cord reflexes are lost at the site of the lesion The more developed the animal the more devastating the spinal shock Functions of the spinal cord (1): 1. Reflector function Associated with nerve centers localized in the gray matter of the spinal cord. Many reflexes are realized though it: Somatic reflexes – most prominent: Tendon reflex – used by neurologists to test reflex arc integrity  Muscle reflective tone- skeletal muscles are always in a state of tone because of the gravity. This reflex is realized through the spinal cord. Vegetative reflexes – are realized through the spinal cord. Lower centers of the sympathetic nervous system are located in thoracic and lumbar segments. Lower centers of the parasympathetic nervous system are located in sacral segments. Regulate, for example, sweating, urine output, defecation, erection, ejaculation. 2. Conduction function Provides communication between different parts of the CNS Conduction paths of excitation are localized in the white matter of the spinal cord: Ascending (transfer information to the brain) Descending (transfer information to the periphery) In case of any disturbances in impulse conduction the paralysis occurs. 122. What are the differences between oxygen dissociation curves for adult hemoglobin, fetal hemoglobin and myoglobin? The oxygen – hemoglobin dissociation curve = oxyhemoglobin - bw O2 concentration and percentage saturation of Hb This curve is an important tool for understanding how our blood carries and releases oxygen. Hemoglobin: – Shows a sigmoidal (S-shaped) curve (due to its cooperative binding of oxygen molecules) – Low saturation at low pressures (pO2); high saturation at high pressures (pO2) Fetal hemoglobin: – Hemoglobin molecules have slightly different shape (molecular structure) than adult hemoglobin, making them have a HIGHER AFFINITY for oxygen (they bind it more readily/easy) – Sigmoid shape dissociation curve but shifted LEFT (it has a higher oxygen affinity) – Higher affinity for oxygen ensures that oxygen moves from adult (mother’s) hemoglobin to fetal hemoglobin in the capillaries of the uterus Myoglobin: – Higher affinity for oxygen than hemoglobin (saturated at extremely low O2 concentrations, so able to store oxygen in muscle cells no matter what concentrations are in body) – NOT an Sshaped curve, like in hemoglobin. Only binds ONE O2 molecule at a time (only one heme group per myoglobin) – Releases oxygen to muscle cells when levels of O2 in blood are extremely low, allowing aerobic respiration to continue/delaying anaerobic respiration! 62. Ticket 123. What forms the brainstem? The functions of the brainstem parts? How are expressed their dysfunctions? 3 components of the brain stem are: 1) Medulla oblongata (important centers of life support, defense reflexes, centers regulating digestive juices and motor regulation centers), 2) Pons (regulation of reflector movements, regulation center of muscle tone), 3) Midbrain (vision and hearing center, precise motion center, muscle tone center) + reticular formation  Reticular formation (activating system of the brain) a diffuse region of gray matter throughout the brain stem. It is responsible for nonspecific functions of the CNS. Medulla oblongata Performs two basic functions: 1.Conduction function is associated with nerve fibers: Afferent (ascending) nerve fibers → spinal cord → medulla oblongata → cerebral cortex → Cerebral cortex → medulla oblongata → spinal cord → Efferent (descending) nerve fibers effector 2. Reflector function. Unconditioned reflexes!!!! Nerve centers in medulla oblongata: 1. Centers important for life support: cardiac, respiratory center 2. Defense reflexes: inborn defense reflexes 3. Gastrointestinal centers – 1) food intake (motor); 2) gastric juice secretion centres (secretory); 4. Centers which regulate skeletal muscle tone. (e.g., static and statokinetic reflexes (body pose); reflexes related to the scalp and scalp muscles (facial expressions)) Midbrain Functions (1): 1) Primary vision center, which provides visual orienting reflexes – turning the head in the direction of bright light, eyeball movements, eye accomodation and pupillary reactions. The intregration center of this reflex is superior colliculus 2) Primary auditory center which provides auditory orienting reflex - ear, head turing in direction of a loud sound. The principal nucleus of the auditory pathway is inferior colliculus 3) The centers in red nucleus regulate and coordinate flexor and extensor tone. If there is an injury between the red nucleus and medulla oblongata decerebrate rigidity occurs (for example., animal cannot bend legs – they are stretched). 4) In midbrain substantia nigra are localized centers that participate in the regulation of very precise, complex movements E.g., chewing, swallowing, finger movements in humans and primates. Pons Functions: Conduction pathway between higher and lower brain centers Relays signals from forebrain to cerebellum Helps coordinating respiration, swallowing, bladder control, hearing, equilibrium, eye movement, posture etc. 124. How are solutions classified based on osmolarity? How will each of them affect a live cell? 63. Ticket 125. Name and describe the phases of gastric juice secretion and its control. Control of gastric juice secretion: The nervous system and endocrine system collaborate to increase gastric secretion and motility when food is eaten and to suppress them as the stomach empties. Gastric activity associated with eating is divided into three stages, called the cephalic phase, gastric phase, and intestinal phase, depending on whether the stomach is being controlled by the brain, by itself, or by the small intestine. These phases overlap and all three can occur simultaneously. 1. Cephalic/brain phase (before eating) ⎼ the stomach responds to sight, taste or thought of food. About 30% of total acid secretion occurs before food enters the stomach. Starts with conditioned irritants by afferent nerves to the medulla oblongata before the food enters the stomach. The efferent are n.vagus fibers, the neurotransmitter acetylcholine, which affects parietal cells directly and indirectly (gastrin and histamine). a. If food arrival is delayed, unused HCl activates D cells, which secrete somatostatin and inhibit the formation of HCl. 2. Gastric phase /during eating) ⎼ 50-60% of total gastric acid secretion occurs during this phase. Provided by direct contact of the food with the stomach wall (wall stretch and protein in the food). Controlled by n.vagus, which stimulates the release of gastrin and histamine in glandular cells. 3. Intestinal phase (after eating). 5-10% of gastric secretion occurs during this phase. Signals from the small intestine about the stretchiness of the intestines, low pH (acidic), osmotic concentration activate neuroendocrine cells in the intestinal wall, which at the first slightly increase, then inhibit gastric function and secretion of juice 126. Humoral regulation of renal functions, which hormones are involved? Describe the renin-angiotensin-aldosterone system? Humoral way regulates reabsorption processes: Involved substances are renin (enzyme) and angiotensin (hormone) ADH (antidiuretic hormone) regulates water reabsorption Aldosterone regulates sodium excretion Parathormone & calcitonin regulate blood Ca level !!! The juxtaglomerular complex contains special cells that receive information about: Decreased arterial blood pressure in the nephron Increased levels of Na in the filtrate, which flows through nephron tubules The Renin-Angiotensin-Aldosterone System (RAAS): Primary function: maintaining systemic blood pressure Secondary function: glomerular filtration rate (GFR) Also significantly impacts tubular reabsorption in the nephron and collecting system in order to influence electrolyte balance and blood volume, in addition to causing changes within the body as a whole. 1. Systemic blood pressure decreases, causing a decrease in the GFR. 2. Decreased blood flow through the afferent arteriole triggers the JG cells to release the enzyme renin into the bloodstream. 3. Renin circulates until it encounters an inactive protein produced by the liver called angiotensinogen. Renin catalyzes the conversion of angiotensinogen to a product with minimal activity, angiotensin-I (A-I). 4. A-I circulates through the blood until it encounters an enzyme called angiotensin-converting enzyme (ACE), which is made by cells such as the endothelial cells in the lungs. ACE converts A-I to its active form, angiotensin-II If the blood pressure decreases, increases the production of renin in the kidneys, by its impact from blood plasma angiotensinogen is formed active angiotensin II which is very powerful constrictor of the peripheral blood vessels (arteries), thereby the blood pressure increases. This is the reaction to the low blood pressure. If the amount of Na ions in the filtrate increases then acts the whole renin-angiotensinaldosterone system. Angiotensin stimulates the production of aldosterone in adrenal glands. Aldosterone goes to the nephron tubules where promotes the reabsorption of the Na ions, thereby Na ions are withhold in the body and decreases their amount in the urine. 64. Ticket 127. Describe the placental transfer of respiratory gases. The main function of placenta is to transport material and heat between the blood of the fetus and the mother. This transport occurs due to diffusion (O2, CO2, inorganic ions, glucose) and active transport of amino acids.  However, placenta is not a perfect exchanger of substances. This does not cause problems regarding nutrients or waste products, because the rates at which substances need to be exchanged are low. Transfer of O2 is more problematic in the placenta than in the lungs. Whereas alveolar pO2 is nearly constant, transfer of O2 from maternal blood to fetal blood is associated with a reduction in the pO2 along the maternal blood vessels from which O2 is delivered to fetal capillaries. This reduction in maternal pO2 limits O2 uptake by the fetus. There are several mechanisms by which the fetus is adapted to an environment with a relatively low pO2: ○ The RBCs of the fetus contain hemoglobin with higher affinity for O2 than that of adult hemoglobin ○ Fetal blood in some species has more hemoglobin than adult blood per unit volume; this applies particularly to humans, but also to lambs and calves. ○ Relative to body mass, cardiac output is much higher in a fetus than in adults 128. What are the functions of phospholipids? Structure: glycerol + 2 fatty acids + phosphate group Have a bigger physiological meaning than neutral fats Functions: Structural components of cell membranes Bring water and fat together and are called emulsifiers Take part in lipid absorption Synthesize lipoproteins and transport lipids in blood Prevent fatty liver Form surfactant in lungs Play important role in blood coagulation 65. Ticket 129. The role of pCO2, pO2 and pH in regulation of ventilation? ROLE OF pCO2 (CO2 partial pressure): The most important factor regulating ventilation! Increased pCO2 ➜ deeper, more rapid breathing ➜ pCO2 normalised ○ Increades pCO2 ➜ increased nerve impulse frequency to inspiratory neurons ○ Increased pCO2 ➜ increased H+ concentration; but H+ does not cross blood-brain barrier Both peripheral and central chemoreceptors highly sensitive to pCO2 (change in pH) ○ Peripheral chemoreceptors – about 40% effect of pCO2 on ventilation ○ Central chemosensor – does not sense the pCO2 itself but changes in pH in the surrounding fluid  Only 2-3 mmHg increase doubles pulmonary ventilation ROLE OF pO2 (O2 partial pressure): pO2 is monitored by peripheral chemoreceptors, but in normal circumstances, it is NOT important in the regulation of ventilation ○ A paradox, considering how important O2 is to the body… Arterial pO2 must fall