Unit 11 - Respiratory System

List the homeostatic functions of the conducting zone of the respiratory system.

1) Warming 2) Humidification 3) Filtration 4) Cleaning

Define: acidosis, alkalosis, respiratory acidosis, respiratory alkalosis, metabolic acidosis, metabolic alkalosis, buffers

Acidosis: blood pH < 7.35 Alkalosis: blood pH > 7.45 Respiratory acidosis: decrease in blood pH due to an increase in plasma concentration of CO2 and carbonic acid caused by a decrease in ventilation (hypoventilation). Respiratory alkalosis: increase in blood pH due to a decrease in plasma concentration of CO2 and carbonic acid caused by an increase in ventilation (hyperventilation). Metabolic acidosis: decrease in pH due to metabolic factors such as increased production of nonvolatile acids (i.e. ketone bodies) or a decrease in bicarbonate. Metabolic alkalosis: increase in pH due to metabolic factors such as low levels of nonvolatile acids or high levels of bicarbonate. Buffers: molecule, such as bicarbonate ion that binds to H+ in order to maintain blood pH

Describe the morphology of the alveolus and identify the type I and type II alveolar cells and indicate their function.

Alveoli make up the majority of the lung and are the reason for the spongy texture. They are clustered together in the shape of a polyhedral, similar to a honeycomb. To facilitate efficient diffusion of gas molecules, alveoli are thin walled and their basement membrane fuse with the endothelial cells of capillaries. Type I alveolar cells make up the majority of the surface area of the lungs and is the site for gas exchange. Type II alveolar cells secrete surfactant to reduce surface tension caused by hydrogen bonds between water molecules at the water/air interface; this prevents the collapse of alveolus.

Describe the homeostatic response to high altitude exposure

At high altitudes, the atmosphere has a lower PO2. To compensate for the lower oxygen content, the respiratory system will gradually become acclimatized through the following mechanisms: 1) Hyperventilation - increase total minute volume; causes alkalosis but kidneys attempt to compensate, allowing for further hyperventilation. Alkalosis also increases hemoglobin's affinity for oxygen in the lungs 2) 2,3 DPG production is increased, causing a decrease in hemoglobin's affinity for oxygen and more unloading of oxygen into tissues. 3) After a few days/week, kidneys will detect the decrease in tissue oxygen content and will secrete erythropoietin to stimulate production of red blood cells and hemoglobin to increase blood oxygen content.

Define: atmospheric pressure, intrapleural pressure, transpulmonary pressure and negative pressure.

Atmospheric pressure: pressure in the atmospheric air; remains constant Intrapleural pressure: pressure within the intrapleural space caused by contraction/recoil of diaphragm. During inspiration, pressure within the intrapleural space is lower (negative) than atmospheric. During expiration, pressure within the intrapleural space is higher than atmospheric. Transpulmonary pressure: pressure difference between intrapulmonary (pressure within the lungs) and intrapleural pressures (pressure within the intrapleural space); causes lungs to stick to thoracic cavity wall. Negative pressure: pressure that is less than atmospheric pressure

Describe the respiratory centers of the brainstem and cerebral cortex

Brain Stem receives sensory information from the body to regulate ventilation and has 3 respiratory centers. 1) Apneustic Center: located in pons (inspiration) 2) Pneumotaxic center: located in pons (pneumotaxic) 3) Rhythmicity center: located in medulla oblongata and controls automatic ventilation Cerebral Cortex: controls voluntary breathing and can override the medulla oblongata.

Reproduce the chemical reaction of bicarbonate formation by carbonic anhydrase

CO2 + H2O ----> H2CO3 ----> H+ + HCO3-

Discuss the role of carbonic anhydrase in the formation of bicarbonate

Carbonic anhydrase catalyzes the reaction of carbon dioxide and water to form carbonic acid within red blood cells. As carbonic acid concentrations rises following blood flow through systemic capillaries, there is the dissociation of carbonic acid into bicarbonate and hydrogen atom.

Identify the location of chemoreceptors in the mammalian body

Central chemoreceptors: ventrolateral surface of the medulla oblongata Peripheral chemoreceptors: located in small nodules known as aortic and carotid bodies associated with aorta and carotid arteries, respectively.

Discuss how hemoglobin transports oxygen in the blood

Hemoglobin is found in red blood cells. It is composed of four polypeptide chains, each with a heme group that contains an iron molecule that can bind and transport oxygen.

Describe hemoglobins affinity to oxygen with altering levels of PC02, pH and temperature

Higher pCO2 will result in less O2 affinity and MORE unloading (shift to the right) Higher pH will results in greater affinity for oxygen and LESS unloading (shift to the left) Higher temperature will result in less oxygen affinity and MORE unloading (shift to the right) Therefore high pCO2, high temperature, and low pH will result in more unloading

Discuss the actions of the diaphragm, intercostals, rib cage, intrathoracic pressures, intrapleural pressures and movement of air during inspiration

Inspiration: contraction of diaphragm and intercostal muscles raises the rib cage, increase in thoracic volume, decrease in intrapulmonary pressure (below atmospheric pressure) and movement of air into lungs.

Differentiate between internal and external respiration.

Internal respiration - exchange of gases between tissues and blood External respiration - refers to gas exchange between air and blood in the lungs

Describe the role of iron in oxygen transport

Iron (Fe2+) is found within in the centre of each heme group in a hemoglobin. Iron will share its electrons to bind with oxygen; thus, for each hemoglobin molecule there will be 4 heme groups, 4 iron atoms and 4 oxygen molecules.

Discuss loading and unloading reactions

Loading Reactions: takes place in the lungs; deoxyhemoglobin combines with oxygen to form oxyhemoglobin Unloading Reaction: takes places at the tissue level; oxygen dissociates from oxyhemoglobin to enter tissue cells to yield deoxyhemoglobin

Describe the anatomy of the lungs.

Lungs are located in the thoracic cavity, suspended in the pleural cavity. They are open to the external environment via the trachea. Lungs have a series of tubes that systematically branch out into smaller and smaller airways that carry air to millions of interconnected sacs called alveoli, where gas exchange occurs.

Identify methods of CO2 transport in the blood

Mostly as Bicarbonate (HCO3-) Some as dissolved CO2 in plasma or carbamino compounds

Discuss how Boyle's law impacts ventilation.

Movement of air into and out of the lungs is dependent on pressure differences between the atmosphere and lungs. The contraction and relaxation of the diaphragm during ventilation causes a change in lung volume, which ultimately changes transpulmonary pressure. Inspiration: contraction of diaphragm, ↑ lung volume, ↓ transpulmonary pressure, which is < atmospheric pressure, air moves into lungs Expiration: relaxation of diaphragm, ↓ lung volume, ↑ transpulmonary pressure, which is > atmospheric pressure, air moves out of lungs

Identify the major atmospheric gases and indicate the proportions relative to atmospheric pressure

O2 = 21% (159 mmHG) N2 = 78% (593 mmHG)

Define: oxyhemoglobin, deoxyhemoglobin, methemoglobin, carboxyhemoglobin, percent oxyhemoglobin saturation

Oxyhemoglobin: a molecule of hemoglobin that has oxygen bound Deoxyhemoglobin: a molecule of hemoglobin with no bound oxygen Methemoglobin: hemoglobin molecule with an oxidized iron atom (Fe3+); methemoglobin is not able to bind oxygen since it does not have a free electron to share. Carboxyhemoglobin: hemoglobin molecule that is bound to carbon monoxide (CO); the CO has a very tight bond with hemoglobin and is therefore difficult for an oxygen molecule to displace the carbon monoxide molecule. Percent oxyhemoglobin saturation: the percent of total hemoglobin that is bound to oxygen.

State specifically the partial pressure of oxygen in the atmosphere (PatmosphereO2), alveoli (PAO2), pulmonary arterial blood (PaO2) and pulmonary venous blood (PvO2)

P-atmO2 : 159mmHg P-alveoliO2 : 105mmHg P-arterialO2 : 100mmHg P-venousO2 : 40mmHg

Identify molecules recognized by chemoreceptors

PCO2, H+, PO2 (only detected by carotid bodies)

Differentiate between central and peripheral chemoreceptors

Peripheral chemoreceptors: - in aorta and carotid arteries - detect H+ - immediate response to increase ventilation when increase in arterial CO2 is noticed Central chemoreceptors: - medulla oblongata - detects CO2 and carbonic acid in CSF and interstitial tissues - slower response; maintain increased ventilation if there is sustained elevated levels of arterial CO2

State Laplace's Law

Pressure is proportional to surface tension and inversely proportional to the radius of alveoli. P = 2T/r P= pressure; T= surface tension; r= radius

State Boyle's Law.

Pressure of any given gas is inversely proportional to its volume.

Define pressure, partial pressure, atmospheric pressure

Pressure: the amount of force within a given area exerted against a surface Partial pressure: the amount of pressure that a specific gas within a mixture exerts on its own. It is equal to the product of the total pressure relative to its percentage within of the mixture (x% of total pressure) Atmospheric pressure: sum of all partial pressures of gases in atmospheric air. It is consistent at sea level; however as altitude increases, the partial pressures of gases and atmospheric pressure decrease.

Describe the relationship between lung alveoli and pulmonary capillaries.

Pulmonary capillaries and lung alveoli are closely associated with a large number of capillaries enveloping the entire alveolus. In addition, capillaries and alveoli are only separated by a very small distance (0.3mm). Both features allow for rapid gas exchange between air in the alveoli and blood in the pulmonary capillary. High O2 concentration in the alveoli diffuses into the pulmonary capillaries

Describe the role of the rhythmicity center, apneustic center, pneumotaxic center in the regulation of breathing

Rhythmicity center: controls automatic ventilation; may be influenced by apneustic and pneumotaxic centers Apneustic Center: promote inspiration by stimulating I neurons Pneumotaxic center: inhibit inspiration by antagonizing the apneustic center

Describe the role of surfactant in maintaining normal alveolar function

Surfactant will decrease surface tension by disruption the hydrogen bonds between water molecules. If surface tension becomes too high, it would collapse the alveoli.

Describe the chloride shift and reverse chloride shift

The Chloride shift: is the trapping of H+ within RBCs (when bicarbonate diffuses out of the cell). This net positive charge attracts Cl- The Reverse Chloride: (pulmonary capillaries) hydrogen atom dissociates from deoxyhemoglobin; H+ attracts bicarbonate ions from plasma in exchange for chloride ions (Cl- moves out of red blood cell into plasma) --> allows H+ to bind to bicarbonate to form carbonic acid. Carbonic acid is then converted into carbon dioxide gas and water.

Describe the Hering-Breuer reflex

The Hering-Breuer reflex is a mechanism stimulated by pulmonary stretch receptors that inhibits over distention of the lungs.

Discuss the effects of exercise on ventilation

The increase in ventilation has been suggested to be triggered by two mechanisms: 1) neurogenic which stimulates respiratory muscles through sensory nerve activity from exercising limbs 2) humoral, where the cerebral cortex stimulates brain stem respiratory centres At the end of exercise, there is a gradual decrease in ventilation once the balance between oxygen and carbon dioxide is restored.

Discuss how Henry's Law predicts movement of O2 during alveolar gas exchange

The maximum amount of gas dissolved in air or blood is dependent on: 1) the solubility of gas in liquid 2) the temperature of fluid and 3) the partial pressure of the gas. Solubility and temperature are constants, so the movement of oxygen during gas exchange is driven by differences in partial pressure between air and blood.

Describe the oxyhemoglobin dissociation curve

The oxyhemoglobin dissociation curve is a graphic representation of the percent oxyhemoglobin saturation at different oxygen partial pressures (P02); it demonstrates the% unloading reactions based on oxygen content. Under normal conditions, the dissociation curve is a sigmoidal or S-shaped curve. At high P02 (arterial blood), hemoglobin is 97% saturated with oxygen. As blood passes through tissues which have a lower P02, oxygen will dissociate (unloading reaction) from hemoglobin (75% saturated). During exercise, a low P02 levels in returning venous blood correspond to higher level of dissociation (unloading) at tissues.

Discuss how the respiratory system can maintain acid base balance

The respiratory system maintains acid base balance by regulating the concentration of carbon dioxide in the blood.

State Dalton's Law

The total pressure of a gas mixture is equal to the sum of the pressures that each gas in the mixture would exert independently. (all the partial pressures combined)

Define tidal volume

Tidal Volume: volume of air expired in each breath

Define: ventilation, gas exchange, oxygen utilization, inspiration, expiration, compliance.

Ventilation: process of moving air in and out of the lungs (i.e. breathing) Gas exchange: process where gases are transferred across a surface in the opposite direction (based on diffusion gradient). This takes place between air and blood in the lungs and between blood and tissues. Oxygen utilization: use of oxygen by tissue through cellular respiration. Inspiration: movement of air into lungs through contraction of diaphragm Expiration: movement of air out of lungs through relaxation of diaphragm Compliance: ability to distend/expand when stretched

Predict changes in PC02, pH and oxygen content detected by chemoreceptors will have on ventilation

↑ PC02 causes ↑ ventilation ↓ pH causes ↑ ventilation ↓ P02 causes ↑ ventilation

Predict changes to blood pH based on changes in ventilation

↑ ventilation : ↑ pH ↓ ventilation : ↓ pH

Discuss the actions of the diaphragm, intercostals, rib cage, intrathoracic pressures, intrapleural pressures and movement of air during expiration

Expiration: relaxation of diaphragm and intercostal muscles lowers the rib cage (recoil of lungs), decrease in thoracic volume, increase in intrapulmonary pressure (above atmospheric pressure) and movement of air out of the lungs.

Describe the feedback regulation of chemoreceptor control of breathing

Chemoreceptors found in brain and arterial system will detect increases in PC02 through changes in plasma carbon dioxide content and blood pH, respectively. The respiratory centres will increase ventilation accordingly through the activation of respiratory muscles. As ventilation increases, there will be a negative feedback loop caused by the clearance of CO2 leading to a decrease in arterial PC02 and subsequent increase in pH to normal levels.

List the physical properties of the lung and how they influence ventilation

Compliance: ability of lungs to distend under pressure; allows for changes in lung volume Elasticity: ability of lung to return to its normal size after being distended; allows for distension during inspiration and recoil during expiration. Surface Tension: partially collapses alveoli during expiration, causing an increase in transpulmonary pressure.

Identify: mouth, nose, pharynx, larynx, trachea, primary bronchus, terminal bronchioles, respiratory bronchioles, and alveolus in the conducting zone and respiratory zone.

Conducting Zone: brings air to the respiratory zone; includes the mouth/nose, pharynx, larynx, trachea, bronchi and bronchioles (including terminal bronchioles). Respiratory Zone: site of gas exchange; includes respiratory bronchioles and alveolar sacs.

Describe the diaphragm, mediastinum, thoracic cavity, pleural membranes, intrapleural space, lung lobes.

Diaphragm: separates the abdominal and thoracic cavity; it is a dome-shaped striated muscle that is used during inspiration/expiration. Mediastinum: group of structures located in the middle of the thoracic cavity (between the lungs). Thoracic cavity: region above the diaphragm that contains the heart and associated large vessels, the respiratory system (including the lungs, trachea) as well as the esophagus and thymus. Pleural membranes: wet epithelial membranes that line the mediastinum; the parietal pleura line the inside wall of the thoracic cavity and the visceral pleura covers the surface of the lung. Intrapleural space: very small space between the parietal and visceral membrane that contains a thin layer of fluid that lubricates lungs during ventilation. Under normal circumstances, the visceral pleura is pushed against the parietal pleura with both membranes essentially stuck together, eliminating this space. If lungs collapse, the intrapleural space would become a real space. Lung lobes: the lung is divided into lobular regions. The right lung has 3 lobes, whereas the left lung has 2 lobes.