Physiology Verbal Exam PDF

62. Ticket............................................................................................................................................... 26 123. What forms the brainstem? The functions of the brainstem parts? How are expressed their dysfunctions?....................

62. Ticket............................................................................................................................................... 26 123. What forms the brainstem? The functions of the brainstem parts? How are expressed their dysfunctions?.................................................................................................................................. 27 124. How are solutions classified based on osmolarity? How will each of them affect a live cell?.. 27 63. Ticket............................................................................................................................................... 27 125. Name and describe the phases of gastric juice secretion and its control................................ 27 126. Humoral regulation of renal functions, which hormones are involved? Describe the renin-angiotensin-aldosterone system?........................................................................................... 27 64. Ticket............................................................................................................................................... 27 127. Describe the placental transfer of respiratory gases................................................................27 128. What are the functions of phospholipids?...............................................................................27 65. Ticket............................................................................................................................................... 27 129. The role of pCO2, pO2 and pH in regulation of ventilation?................................................. 27 130. What is the difference between the observation method and experiment (main features, examples)?...................................................................................................................................... 27 66. Ticket............................................................................................................................................... 27 131. What is thermoregulation? Neurohumoral regulation of body temperature........................... 28 132. How happens the filtration and reabsorption process in capillaries?......................................28 67. Ticket............................................................................................................................................... 28 133. What is lung total capacity? What parameters make it? Explain each of them...................... 28 134.The hormones produced in ovaries and placenta? Their meaning?......................................... 28 68. Ticket............................................................................................................................................... 28 135. Differences between autonomic and somatic reflex arc (name all structures, neurotransmitters)........................................................................................................................... 28 136. How happens milk ejection? What hormones play a role in milk ejection and how?............ 28 69. Ticket............................................................................................................................................... 28 137. Types of receptors based on on what type of irritation they perceive and location, examples. Agonists, antagonists...................................................................................................................... 28 138. What are the centres of respirations, what are their functions?.............................................. 28 70. Ticket............................................................................................................................................... 28 139. Types of chemical signaling between cells. Division of hormones according to their place of synthesis.......................................................................................................................................... 29 140. The composition of bile, its meaning, neurohumoral regulation of its secretion?..................29 This highlight = from consultation This highlight = not sure about the answer, must be reviewed This highlight = question unfinished or wrong 1. Ticket 1. What is the composition of blood plasma? The physiological meaning of each component. Blood plasma makes up about 60% of the whole blood.  Blood plasma is straw-colored liquid consisting of organic and inorganic substances (electrolytes, nutrients, proteins, hormones, etc.) with an addition of dissolved blood gases. Colloidal components are proteins and their compounds. Salts and proteins buffer the blood; they effectively keep the blood pH near 7.4 and they maintain the blood osmotic pressure which pulls tissue fluid into capillaries. Plasma is the fluid portion of blood. That part of the osmotic pressure that is created by proteins mainly albumin (organic substances) is called colloid osmotic or oncotic (due to their ability to draw Н2О). The main organic substances are 6: 1. Blood plasma proteins (7%) Albumins (~59%) are the body’s main protein reserve. Main component that creates colloid osmotic (oncotic) pressure. By attracting water, they take part in regulation of water exchange. Are carrier proteins for bilirubin, bile acids, fatty acids, thyroxine, aldosterone etc. (albumins, fibrinogen produced in the liver) Globulins (~30%) are a diverse group of proteins divided into three groups: α, β are carrier proteins: α + lipids, β + iron, + lipids, +polysaccharide, but γ mainly as antibodies (IgG, IgA, IgM etc.), which assist the body’s immune system in defense against infections and illness. (globulins are produced in the bone marrow, spleen, lymph nodes, and cells of the mononuclear phagocytic system.) Immune substances, antibodies: – Lysine (dissolve foreign proteins) – Agglutinins (agglutinate) – Antitoxins (neutralize toxins) – Precipitins (precipitate) – Lactoglobulins (Aquired, passive, natural immunity) Fibrinogen (3 g/L (~0.2-0.4%)) - plasma protein which takes part in blood clotting. 2. Nutrients (amino acids, lipids, glucose). It is the main energy source. 3. Cholesterol (essential for production of steroids, including sex hormones) 4. Vitamins, microelements (trace elements) (Fe, Co, I). Catalyzes reactions, is part of many substances. 5. Metabolic end products (urea in ruminants, lactic acid, creatinine, bilirubin, CO2 etc.) The main inorganic substances Make up to 1% of plasma volume. inorganic salts – mainly NaCl inorganic electrolytes: ○ K+, Ca+, Mg+, HCO3-, HPO42-, SO42- (bicarbonate, hydrogen phosphate, sulphates) ○ Determine the largest part of osmotic blood pressure 2. Which elements of myofibrils take part in the mechanism of muscle contractions? What happens during this process, and how is this process called? Muscle cells are called muscle fibers. Each muscle fiber is made up of: 1. Sarcolemma – this is a muscle fiber cell membrane 2. Sarcoplasm – this is the muscle fiber cytoplasm It contains glycosomes (granules of glycogen) and the oxygen-binding protein called myoglobin It is almost completely filled with contractile filaments called myofilaments 3. Sarcoplasmic Reticulum – this is the smooth endoplasmic reticulum (SER) in the muscle fiber. It is a network of tubes surrounding myofibrils It reabsorbs calcium ions during relaxation It releases calcium ions to cause contraction 4. Transverse Tubules – formed by invaginations of the sarcolemma and flanked by the sarcoplasmic reticulum They carry action potentials deep into the muscle fiber. The T tubules and sarcoplasmic reticulum provide tightly linked signals for muscle contraction. There are T tubules at each junction of A band & I band and they are continuous with the sarcolemma. They conduct electrical impulses throughout cell (every sarcomere); the electrical impulse signals for the release of Ca2+ from adjacent terminal cisternae (triad: 2 cisterns + T tubule) 5. Myofibril – is a bundle of thread-like contractile elements consisting of myofilaments. Depending on the diameter of the muscle fiber, there might be several hundred to several thousand myofibrils within one muscle fiber. - Each myofibril has striations and banding - Make up 80% of the muscle volume - Contain the contractile elements of skeletal muscle cells Myofilaments are extremely fine thread like proteins There are 4 types of myofilaments: 1. Thick filaments (16nm) called myosin a. During muscle contraction, the myosin heads link the thick and thin filaments together, forming cross bridges b. Each myosin molecule (two interwoven polypeptide chains) has a rodlike tail and two globular heads 2. Thin filaments (8nm) called actin a. Actin provides active sites where myosin heads attach during contraction. b. Tropomyosin and Troponin are regulatory subunits bound to actin. 3. Elastic filaments: titin (connectin) attaches myosin to the Z discs  4. Non elastic filaments: nebulin – an actin-binding protein, determines the length of thin filaments’ Sarcomere – is the smallest contractile unit of a muscle fiber, a compartment of myofibrils Z line - a line that separates one sarcomere from another M line - central line of the sarcomere where myosin filaments are anchored. Myosin is connected to this line by myomesin and skelemin. H zone - the area where only myosin filaments are present I band - the area where only actin filaments are present A band - includes overlapping myosin and actin filaments (said this was optional to know) Myosin molecule consists of: 1. Two heavy chains with head region (two globular heads) and rodlike tail. 2. Four light chains (2 pairs of chains basic (essential) and regulatory chain). What is the Sliding Filament Theory of muscular contraction? It is the explanation for how muscles contract to produce force The actin and myosin filaments within the sarcomeres of muscle fibers bind to create cross-bridges and slide past one another, creating a contraction The sliding filament theory explains how these cross-bridges are formed and the subsequent contraction of muscle. 2. Ticket 3. What is homeostasis? Describe the three types of homeostatic regulation in the body's internal environment? The relative constancy of an organism's structure, genetics, and internal environment and the mechanisms that maintain it is called homeostasis.  This constancy is understood by structural, genetic and constant internal environment. Structural homeostasis is aimed at preserving the body's anatomical integrity and functional abilities. It is mostly provided by sensory systems. Genetic homeostasis is aimed at preserving the genetic individuality of the organism. It is provided by the immune system and immune tissues. Homeostasis of the internal environment is ensured by all organs and tissues, maintaining the necessary amount of nutrients and substances, gases (CO2, O2) necessary for plastic processes and reducing the concentration of the end products of metabolism. ○ All autonomic structures (those that do not obey the will) of the body participate in the maintenance of homeostasis of the internal environment. ○ Each of these variables (e.g., CO2, O2, body temperature, the pH, or the Na+, Ca2+ and glucose concentrations) is controlled by a separate “homeostat” (or regulator), which, together, maintain life. Homeostats are energy consuming physiological mechanisms. ○ Fluctuations in the external environment cause fluctuations in the internal environment, but they are regulated by homeostasis mechanisms. Homeostasis types - Generally, there are three types of homeostatic regulation in the body, which are: 1. Thermoregulation. a. Thermoregulation is the process occurring inside the body that is responsible for maintaining the core temperature of the body. Thermoregulation works by the negative feedback loop where once the body temperature is either increased or decreased beyond its normal temperature, it is brought back to normal. b. Different homeostatic processes like sweating, dilation of blood vessels counteract the increased body temperature, whereas processes like contraction of blood vessels, and breakdown of adipose tissue to produce heat prevent the decreased body temperature. c. The process of thermoregulation is maintained by organs like skin and adipose tissue of the integumentary system and the hypothalamus of the brain. 2. Chemical regulation. a. Chemical regulation is the process of balancing the concentration of chemicals like glucose, calcium, acid-base balance, carbon dioxide, etc. in the body by producing hormones. b. During this process, the concentration of hormones like insulin increases when the blood sugar level increases in order to bring the level back to normal. c. A similar process is observed in the respiratory system, where the rate of breathing increases as the concentration of carbon dioxide increases. 3. Osmoregulation. a. Osmoregulation is the process of maintaining a constant osmotic pressure inside the body by balancing the concentration of fluids and salts. b. During this process, excess water or ions or other molecules like urea are removed from the body to maintain the osmotic balance. c. One classic example of this process is the removal of excess water and ions out of the blood in the form of urine to maintain the osmotic pressure of the blood. d. The renin-angiotensin system and other hormones like antidiuretic hormones act as a messenger for the electrolytic regulation system of the body.  4. Describe the role of the urinary system in maintaining homeostasis? The regulation of homeostasis by the urinary system takes place in the kidneys. The kidneys perform the following functions: 1. The kidneys filter the blood by removing metabolic wastes within urine (urea, uric acid, creatinine, drugs, feed additives, pesticides). 2. The kidneys regulate blood solute concentration (osmolarity), by conserving or eliminating water and electrolytes (e.g. sodium, potassium, and calcium ions). 3. The kidneys assist in the long-term regulation of blood pH by conserving or eliminating hydrogen (H+) and bicarbonate (HCO3-) ions. 4. The kidneys directly influence systemic blood pressure through their control of blood volume. a. Renin-angiotensin-aldosterone system (RAAS) Urinary system 5. Maintains fluid homeostasis in the body – the kidneys control fluid volume and blood pressure by excreting more or less salt and water in urine 6. Plays role in maintaining normal blood pressure by secreting renin 7. Controls red blood cell production by secreting the hormone erythropoietin 8. Regulation of blood levels of ions such as sodium, potassium, chloride, sulphate, phosphate and calcium (electrolyte homeostasis) 9. Maintenance of proper pH of the blood – when pH is too low (blood is too acidic), for example, the kidneys excrete less bicarbonate (which is alkaline) in urine. When pH is too high (blood is too alkaline), the opposite occurs, and more bicarbonate is excreted in urine (acid-base homeostasis) 10. Retention of important nutrients such as glucose and amino acids and other organic substances (e.g., lactic acid, water-soluble vitamins) in the blood 11. Elimination of cellular waste products such as urea a by-product of protein catabolism and uric acid, a by-product of nucleic acid catabolism. 3. Ticket 5. What are the places of contact between 1. a nerve and a nerve and 2. a nerve and a muscle called? Name the different types of these places of contact depending on their structure and the way impulses are conducted. Synapse is a junction between a nerve and a muscle or two nerves where impulses are transmitted by help of a neurotransmitter. The neuromuscular synapses are the largest. The neurotransmitter is released at the nerve endings at the point of contact. Each synapse has 3 main structural elements: Presynaptic membrane is localized at the end of the expanded nerve. Synaptic gap (cleft), place of impulse transmission Postsynaptic membrane can be a nerve or other tissue specific membrane with receptors. The electrical synapses Electrical synapses transmit impulses through channels in the presynaptic and postsynaptic membrane. Electrical synapses use sodium ions to transmit an electrical signal Transdermal proteins (connexins) in each membrane form connections (connexons), when they rotate the electrical synapse channel (gap) opens/closes. The speed of transmission impulses in electrical synapses is faster than in chemical ones (but electrical synapses are rare). These synapses are in the smooth, cardiac muscles, brain and in neuroglia cells The chemical synapse There are ~10 billion neurons in human brain, each neuron has ~10 thousand synapses with other neurons. The spinal cord has ~1 billion neurons and ~5 billion synapses, where 1% are connected with afferent nerve fibers, 10% with nerve fibers in brain, 89% with interneurons in the spinal cord. neurotransmitters used in a chemical synapse. Types of chemical synapses: a. Axodendritic, b. Axosomatic, c. Axoaxonic, d. Dendrodendritic, e. Dendrosomatic. 6. Name the main proteins of blood plasma and their functions. What is oncotic pressure? Similar w/ question 1 Blood plasma proteins (7%) Albumins (~59%) are the body’s main protein reserve. Main component that creates colloid osmotic (oncotic) pressure. By attracting water, they take part in regulation of water exchange. Are carrier proteins for bilirubin, bile acids, fatty acids, thyroxine, aldosterone etc. (albumins, fibrinogen produced in the liver) Globulins (~30%) are a diverse group of proteins divided into three groups: α, β are carrier proteins: α + lipids, β + iron, + lipids, +polysaccharide, but γ mainly as antibodies (IgG, IgA, IgM etc.), which assist the body’s immune system in defense against infections and illness. (globulins are produced in the bone marrow, spleen, lymph nodes, cells of the mononuclear phagocytic system.) Immune substances, antibodies: – Lysine (dissolve foreign proteins) – Agglutinins (agglutinate) – antitoxins (neutralize toxins) – precipitins4 (precipitate) – Lactoglobulins (Aquired, passive, natural immunity) Fibrinogen (3 g/L (~0.2-0.4%)) - plasma protein which takes part in blood clotting. Functions of blood plasma proteins The only protein reserve in the body! Supply of nutrients for the body's plastic and energetic processes (They transport many substances (bilirubin, fats acids, exogenous substances, including drugs — antibiotics and others). They transport substances which are poorly soluble in water (transport of hormones) Create colloid osmotic (oncotic pressure) in the blood plasma, that is 0.5% of the total osmotic pressure. It ensures the normal exchange of water and salts in the capillaries. (e.g., mechanism of edema) Protective role – especially for globulins. Help to maintain relatively constant blood pH. Plasma proteins transport various substances in the blood. Take part in blood coagulation – fibrinogen Colloid osmotic (oncotic) blood pressure: Is created by proteins in the blood plasma About 80% results from the albumin fraction 20% from the globulin Only a tiny amount from the fibrinogen. Oncotic blood pressure affects: In capillaries – filtration and reabsorption (attracting H2O). pH level (acts as a buffer), transport (Fe, lipids, hormones, vitamins, etc.) and protective function (immunity, blood clotting factors, etc.) In plasma, the oncotic pressure is only about 0.5% of the total osmotic pressure. This may be a small percent but because colloids cannot cross the capillary membrane easily, oncotic pressure is extremely important in transcapillary fluid dynamics. Blood plasma osmotic pressure It is determined mainly by the osmolar concentration of salts and ions dissolved in the blood plasma. Provides the pH level Provides excitability Is relatively constant Determines the flow of solvent through the biological membrane, keeping water in the extracellular fluid. Maintained by the excretory organs - kidneys, sweat glands. Any changes are detected by osmoreceptors.  4. Ticket 7. How does the pH of food change in the digestive system? Why? What is the mechanism of maintaining pH in the forestomachs? In stomach ⎼ acidic (pH 1.5⎼3.5) why? Because of HCl - Meaning: 1. Activates pepsinogen by converting it to the active enzyme pepsin 2. Acts on proteins so that pepsin can work better 3. Creates an optimal pH for the activity of gastric enzymes 4. Disinfectant, bactericidal function 5. Regulates the further evacuation of gastric contents to the duodenum 6. HCl in the duodenum promotes the secretion of the hormone secretin, which promotes the secretion of pancreatic juice & bile 7. HCl causes the stomach to produce an internal antianemic factor, a specific glycoprotein that, together with vitamin B12 (an external antianemic factor), promotes erythropoiesis. If there is a lack of it, anemia occurs. 8. HCl deficiency in gastric juice is called anacidity, decrease – hypoacidity, increase - hyperacidity. In forestomaches ⎼ alkaline, why? (why do RU need it to be alkaline)? The rumen and reticulum create an ideal environment (humidity, pH, anaerobic, and temperature) for bacteria to function Therefore, there is a huge amount of bacteria and protozoa. Extra question from sintija can be about the saliva: "saliva has sodium bicarbonate ions that help maintain the alkaline environment by neutralizing volatile fatty acids (VFAs) ➜ needed for protozoa to function" The normal pH (6.5-7.4) in forestomachs contents remains constant because: VFAs are intensively absorbed through forestomachs walls (mostly rumen and omasum) The contents of the forestomachs is continuously neutralized by saliva ○ VFAs constantly irritate the baro- & chemoreceptors in the forestomachs walls ➜ impulses to medulla oblongata's salivary center ➜ impulses to parotid salivary glands ➜ constant saliva secretion ➜ neutralize the VFAs Sintija "loves to talk about volatile fatty acids" so don't forget the meaning of them ➜ Acetic, propionic, and butyric acids ○ Products from the microbial fermentation processes in the forestomachs (mainly in the rumen): Bacterial enzyme cellulase breaks down cellulose into disaccharides (cellobiose) ➜ monosaccharide glucose (2 glucose molecules) ➜ pyruvic acid ➜ lactic acid ➜ volatile fatty acids.  This is why RU have the lowest blood glucose levels, 2x lower than other animals, because glucose gets turned into VFAs (less than 10% of glucose gets absorbed) ○ The optimal ratio of VFAs is: 65% acetic acid ⎼ used in fat synthesis, mainly in mammary glands 20% propionic acid ⎼ provides energy for conversion of glucose to glycogen in the liver, used in lactose synthesis, some metabolized to lactic acid 15% butyric acid ⎼ metabolized and oxidized to ketones, provides energy to rumen wall Acetic acid is formed more from fiber (cellulose), propionic acid from starch, butyric acid from protein ○ So in RU energy is mainly provided by VFAs. ○ The fermentation and absorbtion of VFAs also produce CO2 + In horses these bacteria etc. and volatile fatty acids are in the cecum ⎼ neutralized by alkaline mucus In intestines? (acidic ➜ alkaline) why? Because the food is affected by: 1. Pancreatic juice (pH 7.8 - 8.4) 2. Bile (pH 6.8 - 7.5) 3. Intestinal juice (pH 7.5) ➜ these change the pH to alkaline Saliva In saliva pH is alkaline. In horses pH 7.6-7.8 In pigs pH 7.2-7.5 In dogs 7.5-7.8 ( 6,5) In ruminants pH 8-10, saliva is strongly alkaline, which ensures the biological digestion of food in the forestomachs, maintaining an optimal living environment for microorganisms. Gastric juice - (colorless, clear, dogs, pigs, humans - pH 1.0-2.5, in ruminants pH 2.2-2.8, in calves more acidic – 1.6) Pancreatic juice (pH 7.8 - 8.4) Bile (pH 6.8 - 7.5) Small intestine juice (pH 7.5) The normal pH (6.5-7.4) in forestomachs contents remains constant because: YOU kick MY dog Volatile fatty acids are intensively absorbed through the walls of the forestomachs The contents of the forestomachs is continuously neutralized by saliva Cows excrete about 100 L of saliva per day, with which 300-350g of sodium bicarbonate enters the forestomach. In ruminants – saliva, first of all, plays a very important role in the rumination process. Saliva maintains a moist environment with a certain pH in the forestomachs. ○ Parotid salivary glands secrete continuously in ruminants. In the walls of the forestomachs, baroreceptors and chemoreceptors are irritated.  ○ They are constantly irritated by the volatile fatty acids produced during the fermentation processes in the forestomachs. ○ From the receptors, the impulses go to the salivary center in the medulla oblongata and from there through the efferent nerves to the parotid salivary gland. ○ The secreted saliva neutralizes volatile fatty acids in the forestomachs. In ruminants, the submandibular and sublingual salivary glands secrete only during food intake and rumination. ○ The parotid salivary gland secretes poorly in newborn calves. Saliva is secreted mainly by the mucous sublingual and mixed submandibular salivary glands. ○ As the forestomachs develop and the calves begin to eat roughage, the parotid salivary gland begins to develop faster and secrete more strongly, and the saliva becomes more alkaline. Consequently, the amount of saliva increases. From ChatGPT (below this): pH Changes in the Digestive System 1. Mouth: ○ pH Range: Slightly acidic to neutral (pH 6.5 - 7.5). ○ Reason: Saliva, which contains enzymes like amylase, is slightly acidic to neutral. The pH helps initiate the breakdown of carbohydrates. 2. Stomach: ○ pH Range: Very acidic (pH 1.5 - 3.5). ○ Reason: The stomach secretes hydrochloric acid (HCl), which creates an acidic environment. This acidity helps denature proteins, activate pepsinogen to pepsin, and kill pathogens. 3. Small Intestine: ○ pH Range: Slightly acidic to slightly alkaline (pH 6 - 7.4). ○ Reason: As the acidic chyme from the stomach enters the small intestine, it is neutralized by bicarbonate ions secreted by the pancreas. This neutralization is crucial for the proper functioning of digestive enzymes in the small intestine. 4. Large Intestine: ○ pH Range: Slightly acidic (pH 5.5 - 7). ○ Reason: Fermentation of undigested carbohydrates by gut microbiota produces short-chain fatty acids (SCFAs), which slightly lower the pH. Mechanism of pH Maintenance in the Forestomachs of Ruminants Ruminants, such as cows, sheep, and goats, have a specialized stomach structure comprising four compartments: the rumen, reticulum, omasum, and abomasum. The forestomachs (rumen, reticulum, and omasum) have specific mechanisms to maintain an optimal pH for microbial fermentation. 1. Rumen: ○ Optimal pH Range: 6.2 to 7.2. ○ pH Maintenance Mechanism: Buffering Agents: Ruminants produce large amounts of saliva, which contains bicarbonate and phosphate buffers. These buffers neutralize the acids produced during fermentation.  VFA Absorption: Volatile fatty acids (VFAs) produced by microbial fermentation are absorbed through the rumen wall, reducing their concentration in the rumen and helping to maintain pH. Rumen Motility: Regular contractions of the rumen mix the contents, ensuring even distribution of buffers and preventing localized acid build-up. 2. Reticulum and Omasum: ○ pH Maintenance: Similar buffering and mixing mechanisms help maintain a stable pH, but these compartments primarily serve to further mix and filter the digesta. 3. Abomasum: ○ pH Range: Acidic (pH 2 to 4). ○ Reason: The abomasum functions similarly to the monogastric stomach, secreting hydrochloric acid to facilitate protein digestion. Importance of pH Regulation in Ruminants Maintaining an optimal pH in the forestomachs is crucial for several reasons: Microbial Health: The symbiotic microorganisms in the rumen are sensitive to pH changes. Optimal pH supports the growth and activity of beneficial microbes that aid in the digestion of fibrous plant material. Digestion Efficiency: Proper pH levels ensure the efficient breakdown of feed, maximizing nutrient absorption and overall health of the animal. Prevention of Disorders: Imbalanced pH levels can lead to disorders such as acidosis or alkalosis, which can severely impact the animal's health and productivity. In summary, the pH of food changes significantly throughout the digestive system of animals to optimize the function of digestive enzymes and microbial activity. In ruminants, the forestomachs maintain a stable pH through buffering agents in saliva, absorption of VFAs, and regular motility, ensuring effective microbial fermentation and nutrient absorption. 8. What are inhibition processes in the nervous system? Their role/meaning? How are they realized depending on their type? Inhibitions are reversible changes in the excitability of the nerve cell and decrease in their functional activity. Inhibition in the CNS is realized by special inhibitory structures: inhibitory neurons, inhibitory synapses, inhibitory neurotransmitters. Significance of inhibition: ○ Limits the path of excitation, forcing it to go through a strictly defined reflex arc. ○ Determines the expressiveness of the reflector’s response reaction. ○ Determines the time after which the response appears. ○ Determines whether there is a response at all. Types of inhibition: By localization – presynaptic (indirect) and postsynaptic (direct); By the nature of the process – mainly hyperpolarization (also a strong depolarization) Presynaptic or indirect inhibition This occurs when the inhibitory synaptic knob is located directly on the termination of the presynaptic excitatory fiber  The inhibitory synaptic knob releases a neurotransmitter that inhibits the release of the excitatory neurotransmitter from the presynaptic fiber, e.g., GABA (pain modulation). Inhibition occurs at the presynaptic terminals before the signal ever reaches the synapse Axon-axon synapse (presynaptic synapse) between A and B Neuron B has no direct effect on neuron C, but has a presynaptic effect on A’s ability to affect C (reduces the amount of neurotransmitter release from A) Postsynaptic or direct inhibition This type of synaptic inhibition occurs due to the release of an inhibitory neurotransmitter from presynaptic terminal. Inhibitory neurotransmitters are gamma-aminobutyric acid (GABA), dopamine and glycine. This inhibitory neurotransmitter connects with postsynaptic receptor and causes hyperpolarization which is known as inhibitory postsynaptic potential (IPSP) For example, an excessive muscle stretching activates tendon receptors, They activate Aβ fibers, that excite interneurons that release the inhibitory neurotransmitter - Glycine→ permeability of CI- and K+ increases, but Na+ decreases→ hyperpolarization occurs The hyperpolarization will make it more difficult for the cell membrane potential to reach threshold, thereby making it less likely that an action Hyperpolarizing the α-motor neuron in this way can stop the contraction. Inhibition without participation of any inhibitory structures Inhibition in the CNS can also be realized without the participation of inhibitory structures. It happens if: Excessive (too strong) stimulus has occurred (e.g., from fear losing ability to move) The so-called post-excitation inhibition is observed. If after a strong hyperpolarization of the membrane, a neuron receives too weak excitation that fails to cause a new response. Neuron is in a relative refractory phase or absolute refractory phase. Inhibition is important in regulation of various opposing processes, e.g., coordinating the action of flexors and extensors. If inhibitory processes are disrupted in the CNS, the balance between excitation and inhibition is lost, resulting in disturbances in nervous system (neurosis, depression, etc.). 5. Ticket 9. What are the stages of gas exchange in the body? What anatomical and histological structures of the body are involved in the realization of each stage? Three stages are distinguished in the respiration process: - I External respiration or lung ventilation - II Gas exchange and transport - III Internal or tissue respiration Respiration is the process of gas exchange between the air and an organism's cells.  Internal respiration involves gas exchange between the blood and body cells. Cellular respiration involves the conversion of food to energy. Aerobic respiration is a cellular respiration that requires oxygen while anaerobic respiration does not. Cellular respiration – intracellular processes in which organic molecules are oxidized to produce CO2, water and ATP I External respiration The process of breathing (inhalation and exhalation), also called ventilation. In animals, the process of external respiration is performed in several ways. ○ Animals that lack specialized organs for respiration rely on diffusion across external tissue surfaces to obtain oxygen. ○ Others either have organs specialized for gas exchange or have a complete respiratory system. Related to rhythmical action of respiratory muscles. Occurs in the respiratory organs. ○ Nose (nasal cavity) ○ Pharynx ○ Larynx ○ Trachea ○ Bronchi → bronchioles → terminal bronchioles ○ The walls of these structures do not deflate! ○ Bronchioles (diameter