ALS 2304, Week 12: Respiratory Physiology
ALS 2304, Week 12: Respiratory Physiology ALS 2304
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This 8 page Class Notes was uploaded by Mara DePena on Sunday April 17, 2016. The Class Notes belongs to ALS 2304 at Virginia Polytechnic Institute and State University taught by Dr. Cline in Spring 2016. Since its upload, it has received 16 views. For similar materials see Animal Physiology and Anatomy in Agricultural & Resource Econ at Virginia Polytechnic Institute and State University.
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Date Created: 04/17/16
RESPIRATORY PHYSIOLOGY Example exam question: You’re driving your horse to a race, and there is a hole in the trailer near the exhaust pipe. By the time you get to the horse race, you open the door and what happens? (There will be a wreck and the horse will bleed out, this will involve the cardiovascular system) o The horse falls out dead. The major function of the respiratory system is the exchange of gases. o Two major gases we exchange are carbon dioxide and oxygen. o We are dependent upon the concentration of the gases in the air we breathe (the atmosphere.) If the concentration changes, that disrupts the respiratory system. Going up really high, there’s not much oxygen. We are dependent on a certain threshold amount of oxygen, and without it you go unconscious. You need oxygen in the electron transport chain to pull electrons off of the third complex. Without it you stop producing ATP, and your nervous system collapses. BRONCHIAL TREE Alveoli- Air sacs where gas exchange occurs. In all species. Continuous with the atmosphere. On the other side is a dense net worth of capillary beds. This brings the atmosphere in proximity of the cardiovascular system so gas exchange occurs. In most mammals, there are 23 branches of the bronchial until you reach the very bottom aspect of the lung. Gases move across membranes only through simple diffusion. We are completely dependent upon it for the exchange of gases. o Diffusion is driven by the concentration gradient. SINUSES Open cavities off the lateral aspects of the nasal passage. As the animal takes a breath, the air will come in and tumble through the sinuses before going down into the trachea. What is the advantage of having a turbulent air flow through the head before the lungs? o Warms up and somewhat filters the air. The major function, however, is to warm the air. o Freezing air can freeze the capillary beds in your lungs. When liquids freeze, they form spikes. The spikes will rip through the plasma membrane and kill the cell, causing the bed to rupture open. The animal could drown in its own blood. Sinuses also refine the vocalization of the animal. o Crude sound in the throat, up to sinuses, echo around, refined voice. Sinus infection- When a bacterial infection is up in the sinuses and becomes clogged with mucus. This causes irritation of the sinuses, and inflammation as nonspecific immunity kicks in. PHARYNX Three different parts: o Nasopharynx- Air passes through. o Oropharynx- Food passes through. o Laryngopharynx- Air and food pass through, towards the trachea and esophagus respectively. o Larynx- Voice box. Sound production- Vibration of the mucosa at the inner edge of each vocal chord produces sounds. Speech production- Final modification of voice occurs in mouth, nose, and throat, where tongue, palate, cheek, and lips are involved in articulation. Sides come together and vibrate to make a sound as air passes through. You can have different tensions on the vocal chords. If you change the tension, it changes the frequency at which it vibrates. Moving your tongue and lips around changes the sound characteristics. Sound also goes up into the nasal cavity and causes refinement. TRACHEA Major differences between the trachea and the esophagus: o One has cartilage, one has muscle. o Esophagus collapses upon itself, trachea is always held open. Why? So it won’t collapse upon itself when the animal inhales. On its walls, all the epithelial cells have cilia that go towards the lumen. These cilia move and beat in an upward direction. There is always mucus and phlegm in the bronchial tubes. These cilia propel the mucus up towards the oral cavity. This happens all the time. When you spit something up, you have an excess of the mucus. You subconsciously swallow this mucus all the time, and only spit it up when you are sick and have too much. Mucus has a slight negative charge. Its function is to trap anything you inhale that isn’t air. The negative charge of the mucus attracts any positively charged particles you may inhale. o The digestive system deals will all this stuff you inhale. o If you go down to the terminal air sacs, those compartments are sterile as the mucus sterilizes the air. o If bacteria gets all the way down into the air space and starts multiplying, that causes pneumonia. ELASTIC RECOIL The lung is primarily made of elastic tissue. If you leave elastic fibers alone, they collapse upon themselves. The lungs want to collapse, and that is the last thing they do when you die. Sticking a knife in the lung releases a vacuum between the lung and chest. The vacuum is the only thing that holds the lung in the expanded state. The lungs are independent so that if you lose one, you can still survive. INSPIRATION To take a shallow breath you contract your diaphragm. To take a deep breath you contract your diaphragm and the intercostal muscles on the ribs. External intercostal contraction: o Elevation of ribs and sternum o Increased anterior to posterior dimension of thoracic cavity. o Lowers air pressure in lungs. o Air rushes down its concentration gradient. Diaphragm contraction: o Moves downward o Increases vertical dimension of thoracic cavity o Causes lungs to expand, lowers air pressure in lungs o Air rushes in down its concentration gradient EXPIRATION Exhaling is a passive process. If you exhale really fast, it is no longer passive, as you contract the abdominal muscles. The air leaves at a faster velocity. Diaphragm, ribs, and sternum return to resting position. Thoracic cavity returns to preinspiratory volume. Air pressure in lungs increases, air is exhaled down its concentration gradient. If you are flying in a plane at 30,000 feet and a door flies off of the plane, a lot of the air will leave your lungs. This is because you’re completely dependent on atmospheric pressure. If you are in a hole, there is a high amount of atmospheric pressure because of gravity. The weight of the air above forces molecules closer together. AIR EXCHANGE Exchanging air in the lungs requires energy. o 3% of total ATP goes to contraction of diaphragm. Can increase 25-fold as animal exercises. One of the main reasons the animal starts to fatigue. o Emphysema (heaves in horses) Elastic properties of lungs start to break down. Animal has to work to exhale all the time. Exhaustion kills the animal. ALVEOLAR WALL Coated with a thin film of water. Molecules are more attracted to each other than to the air. Surface tension increases as water molecules come closer together, and could cause the alveoli to collapse. They are pulling on each other and trying to collapse the air space. Causes lung to recoil on itself. Alveoli produces surfactant. Surfactant works to break up the attraction between water molecules, allowing the animal to inflate the lungs. It reduces surface tension, and is produced by Type II alveolar cells. It lines the alveoli and smallest bronchioles, and stabilizes the alveoli. Surfactant develops relatively late in fetal development, which is a problem in premature babies. If a baby is premature, they squeeze soap down its lungs. THE ATMOSPHERE 78% nitrogen o Not used at all. o Legumes can use nitrogen. 21% oxygen 1 % carbon dioxide CIRCULATION One side of the heart pumps the blood to the lungs, the other to all other aspects of the body. Carbon dioxide and oxygen are delivered. Carbon dioxide can kill the animal even if there is a large amount of oxygen. Although carbon dioxide does not influence the movement of oxygen, the carbon dioxide lowers the pH of cells and unfolds the enzymes, ultimately killing the animal. VENTILATION-PERFUSION COUPLING Ventilation- How much air goes through an individual air sac. Perfusion- Amount of blood going through the capillary bed associated with the air sac. If an air sac doesn’t have much air going through, the capillary bed’s sphincter will be closed and its perfusion will go down. The amount of ventilation affects the perfusion. AVIAN RESPIRATORY SYSTEM Very different from a mammal. Compartments known as air sacs. All over the place. When it takes a breath, air comes in and goes back to the posterior air sac. The air then goes into the lungs, which exchange gases. Exhaust air that leaves the lungs goes into the anterior air sacs. From here this air is exhausted out of the bird’s beak. Constant flow of fresh air across the lung, in contrast to the mammal. Can deliver more oxygen to the lung, which allows it to extract more oxygen when flying at high altitudes. If you take a breath and exhaust that air back into the atmosphere, how can you get all the air out of your lungs? o You can’t! o Every time we breathe in fresh air, it mixes with old air. It’s impossible for us to get the exact amount of oxygen in atmosphere into the lung. O 2RANSPORT Most of the oxygen transported on the blood is transported on a molecule called hemoglobin. It binds to hemoglobin (98.5% of oxygen is bound to hemoglobin.) o Part that binds the oxygen is known as the heme group. Saturated- All 4 heme groups bound to oxygen. Partially saturated- 1-3 hemes bound. One hemoglobin can bind four oxygens. When hemoglobin goes back to the lungs, it carries 3 oxygens with it. It only unloads one oxygen at a time. o Safety mechanism. If something goes wrong and gaseous exchange is interrupted in the lungs, there are still 3 oxygens bound to the hemoglobin. You would use these when choking. These would only last seconds. As temperature increases, it is easier to unload oxygen. The opposite is true if temperature decreases. Where blood encounters higher body temperatures, it loads more oxygen into those tissues. If pH goes down, you unload more oxygen, and vice versa. You generate more CO fro2 the Kreb’s cycle if a cell is metabolically active. Bohr effect- A drop in pH that unloads oxygen. TRANSPORT AND EXCHANGE OF CO AT A TISS2E In a metabolically active tissue pH is relatively lower, temperature is relatively higher. More CO on2the tissue side thanks to the Kreb’s cycle. Part of it dissolves into the plasma, while another fraction is transported over into the plasma and associates with water. In the plasma is carbonic acid, which accelerates the conversion of CO 2 in water into the bicarbonate ion. It then rides back to the lung in this form. Bicarbonate is important in buffering the pH of the blood. Not where most of the CO is 2ransported: most is transported inside the red blood cell. Inside the red blood cell, CO 2nd water form carbonic acid. Same as in buffer, but has carbonic anhydrase to speed everything up. To keep a neutral charge on the blood cell, the bicarbonate is transported out and chlorine is transported in. This is known as the chloride shift. Carbon dioxide comes in and binds onto hemoglobin as well, and then rides back to the lung on it. There’s much more oxygen inside the blood than in the metabolically active cell. Blood leaves the cell by going down its concentration gradient; one of the oxygens on hemoglobin falls down its concentration gradient and goes into the metabolically active cell. TRANSPORT AND EXCHANGE OF CO AT A TISSUE 2 Same as CO ex2hange at a tissue, except in reverse. Carbonic anhydrase changes the direction according to the concentration gradient. HALDANE EFFECT Amount of CO ca2ried by hemoglobin interferes with its ability to carry oxygen gas. The more CO in t2e blood, it interferes with the carrying of oxygen gas. o Ignore this for the exam. CONTROL OF RESPIRATION: MEDULLARY RESPIRATORY CENTERS Nervous control of respiratory rate. Intercostal muscles in addition to the diaphragm and abdominal muscles. The region of the brain that sets respiratory/heart rate is the brain stem (pons and medulla oblongata.) It control the respiratory rate, digestive system, renal, and cardiovascular system. Brain dead- Animal is not conscious but is still alive. Cerebral cortex doesn’t function, but brain stem is intact. Dorsal respiratory group (DRG) (inspiratory center, in medulla) o Primarily regulates normal inhalation. When the animal takes a breath, neurons in this group fire and send action potentials down to the intercostal muscles and diaphragm. These muscles contract and increase lung volume, decreasing pressure and allow air to rush in. o Located near the root of nerve IX. o Appears to be the pacesetting respiratory center. o Excites the inspiratory muscles and sets eupnea. 12-15 breaths/minute o Becomes dormant during expiration. Ventral respiratory group (VRG) (in medulla) o When you take a really deep breath. Neurons fire and cause the intercostals to contract even more. Greater action potential. Once these groups start, they on their own don’t have the ability to stop the action potentials. Pontine respiratory group (in pons) o Stops the dorsal and ventral respiratory group. o Stops inhalation by sending a signal to the medulla oblongata. o Essentially the center that causes you to exhale. o EXAM QUESTION: If you lower an electrode into the PRG in a cat, and destroy the PRG, what happens? The cat would never stop inhaling, and wouldn’t be able to exhale until it dies. When the animal inhales, it is not just wiring to the diaphragm and intercostal muscles. Ex: If you have a really deep inhale, there is circuitry that causes the mouth to open and nostrils to flare to take in more oxygen. Also affects the larynx, pharynx. Regulating the medulla groups: o There is input that goes into the medulla oblongata that determines if the ventral group is recruited and sets the frequency at which these two medulla groups fire. o Coughing and sneezing are triggered by the medulla oblongata. o There are stretch receptors in lungs, which tell you when to stop contracting by running into the PRG. o There are also irritant receptors. o Chemoreceptors- Where you start to have a union between the respiratory system and cardiovascular system. In the aortic arch, tell you the composition of the blood that goes everywhere else in the body. In the carotid arteries, tells you the composition of the blood going to the brain. The most important organ to keep you alive is the brain, so blood flow there is precisely regulated. If flow is interrupted, the body will blow out other body systems in order to get blood flowing to the brain. What triggers would increase respiratory rate? Low oxygen High CO 2 Why do you breathe more when you start to exercise? There’s less oxygen as you burn more There’s more CO as2your cells are metabolically active If we see we are not dumping enough CO into the 2 atmosphere, we will increase respiratory rate and increase ventilation, which will increase perfusion. This will increase gaseous exchange. Also have them in the periphery and the skeletal muscles themselves. Why in the skeletal muscles? o If in a fight/flight situation and need to get away, there would be a buildup of CO in the 2 skeletal muscle, and respiratory rate would increase sooner because we anticipate a drop in blood pH momentarily. o
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