CSB346 Midterm Review Notes

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Cell and Systems Biology
John Peever

CSB346 Lecture 1 Functions of the respiratory system - Pulmonary ventilation (ventilating the lungs) - Gas exchange (passive diffusion) - Gas transport (hemoglobin) - Gas exchange (tissue) - Acid-base balance - Speaking and vocalization - Immune protection - Regulation of body temperature (panting in dogs) Functions of the respiratory system Blood-gas interface - Alveoli ismade up of epithelial cells (one cell thick) - Respiratory membrane (alveolar capillary membrane) is the alveolar epithelium and capillary endothelium separated by a small distance filled with interstitial fluid (two cell thick) o 0.2 – 0.5 µm Smoking - Destroys alveoli o Alveoli are unventilated, which is blocked by dead tissue - Destroys capillaries (reversible) o Alveoli are ventilated, but there is no blood flow Pleura - Membrane that lines the interior surface of the chest wall and the exterior surface of the lung Pleural sac - Visceral pleura (lung) is attached to parietal pleura (inside chest wall) is separated by intrapleural space (cohesive property) o Makes the lungs stuck to the chest wall - Each lung is surrounded by a separated pleural sac Pneumothorax (air in pleural space) - Traumatic (e.g., stab wound in the chest) o Hemothorax (blood in pleural space) - Spontaneous (e.g., emphysema or rupture of cyst in lung) o Secondary spontaneous pneumothorax caused by emphysema (disease of lung tissue) Motor nerves (motor neurons) - Spinal motor neurons (cervical, thoracic, lumbar) o MNs exit the spinal cord at the ventral root o MNs enter the spinal cord at the dorsal root - Cranial motor neurons Respiratory muscles - There are two general patterns of motor activity in respiratory muscles o Inspiration is active o Expiration is passive under resting conditions  Internal abdominal muscles are typically involved in expiration but  Respond more to increases in CO2 (hypercapnia)  When CO2 levels are low, low level of abdominal muscle activity o Expiration is passive  When CO2 levels are high, high level of abdominal muscle activity o Expiration is active o The activity of the diaphragm is used as the reference point - Major o Diaphragm  Main respiratory muscle  Inspiratory  Innervated by phrenic MNs (C3 – C5)  Contracts down  chest wall expands  chest cavity expands  lungs expand pressure gradient decreases  air moves down pressure gradient into lungs o Thoracic  External intercostals  Inspiratory  Innervated by MNs (T2 – T5)  Internal intercostals  Expiratory  Innervated by MNs (T2 – T5) o Abdominals  Expiratory  Limit inspiration  When it contracts, it makes it harder for the chest wall to expand  Innervated by MNs (T4 – L3) - Minor o Sternocleidomastoids (shoulders and neck)  Inspiratory  Innervated by MNs from upper cervical spinal cord  Only recruited during rigorous circumstances  Help lift the thoracic cavity to make it bigger o Upper airway  The majority of airway muscles are inspiratory  To help regulate the flow of air into and out of the lungs  To reduce airway resistance  Genioglossus (tongue)  Inspiratory  Innervated by XII MNs (hypoglossal MNs)  Laryngeal and pharyngeal  Inspiratory and expiratory  Innervated by vagal MNs and nucleus ambiguus MNs  When you are fat, pharyngeal muscles work harder to keep space open  Tensor palatini levator (soft palate)  Inspiratory and expiratory  Innervated by V MNs (trigeminal MNs)  Facial muscles (nose)  Inspiratory  Innervated by facial MNs CSB346 Lecture 2 Daily oxygen consumption (360 L/day) - Minute ventilation  how much air is moving in and out of the lungs o VE = VT * RR - Alveolar ventilation how much of the air is being accessed by the alveoli (gas exchange) o VA = (VT * RR) – (DSV * RR) o The conducting zone is anatomical dead space Respiratory membrane - Rate of transport depends on o Concentration gradient o Surface area of gas exchanger (alveoli or capillary) o Permeability of gas exchange membrane (alveoli and capillary) Gas exchange in the lungs - O2 and CO2 move down a concentration gradient o There is more O2 in the air than in the lungs o There is more CO2 in the lungs than in the air - Pulmonaryedema decreases the rate of diffusion of O2from lung into blood Three determinants of alveolar PO2 and PCO2 - PO2 and PCO2 of inspired air (e.g., less PO2 at higher altitude) - Minute alveolar ventilation(VA) - Rate at which the working tissues consume O2 and produce CO2 (e.g., using more than you are delivering) Terms - Hyperpnea  increasing ventilation (VA) to match increase in metabolic demands - Dyspnea  difficulty breathing - Apnea  temporary cessation of breathing - Hyperventilation  ventilation (VA) exceeds metabolic demands - Hypoventilation  ventilation (VA) is insufficient to meet metabolic demands - Hypoxia  deficiency of O2 in tissues - Hypoxemia  deficiency of O2 in blood - Hypercapnia  excess of CO2 in blood - Hypocapnia  deficiency of CO2 in blood Oxygen transport - Every L of blood contains 200ml of O2 (concentration of O2 in blood is 200ml/L) o 3ml (1.5%) is dissolved in blood plasma o 197ml (98.5%) is bound to Hb - Hb has four subunits o Each subunit contains a globin fold and a heme group o O2 binds to heme groups in Hb o 4 O2 + Hb = oxyhemoglobin o 250 million Hb per RBC o Hb also binds CO2 - Hb binds O2 reversibly o High PO2 = Hb binds to O2 from alveolar air o Low PO2 = Hb releases O2 into working tissue - When all binding sites on Hb are bound with O2, Hb is 100% saturated o At 100% saturation, 1g Hb carries 1.34ml O2 o Concentration of Hb in blood is 150g/L o Oxygen-carrying capacity of Hb is 200ml/L - Anemiadecreases the oxygen-carrying capacity of blood o Defunct erythrocyte o Depletes the amount of Hb that is available to carry O2 - Blood lossdecreases the oxygen-carrying capacity of blood Carbon dioxide transport - 86-90% is in the form of bicarbonate (HCO3-) - 5-6% is dissolved in blood plasma - 5-8% is bound to Hb - CO2 + H2O CA H2CO3  H+ + HCO3- o CO2 + Hb o H+ + Hb CSB346 Lecture 3 Respiratory muscles and breathing - The contraction of the inspiratory muscles is increasing lung volume - The contraction of the expiratory muscles is regulating the timing of lung volume o They shorten the periods between inspirations Brainstem control of breathing - DRG (dorsal + medial) and VRG(ventral + lateral) in medulla o Columns of respiratory neurons (inspiratory or expiratory) generates breathing rhythm - PRG in pons o Clusters of respiratory neurons (inspiratory or expiratory) shapes breathing rhythm (e.g., pattern of breathing) o Experiment  Destroying the cells in the PRG disrupts the shape of breathing Chemical control of breathing - Peripheral chemoreceptors o Detect changes in PO2 and PCO2  Sensitive to low PO2 and PCO2  Large decrease in arterial PO2 increases ventilation  Small increase in arterial PCO2 increases ventilation o Carotid bodies located at the bifurcation of the internal and external carotid arteries o Sending information through glossopharyngeal nervesinto the brainstem - Chemical chemoreceptors o Detect changes in PCO2/pH  Detech changes in H+ ions in the cerebrospinal fluid o Located on the ventral surface of the medulla surrounded by blood vessels Mechanical control of breathing - Mechanoreceptors o Detect overall state of the lung and respiratory muscles o Located in the lungs and respiratory muscles (diaphragm, intercostals, upper airways)  Stretch receptors in lung (e.g., how much the lung is inflated)  Pressure receptors in upper airways (e.g., if something is blocking the airway) o To adapt and integrate breathing with reflexes (e.g., talking, choking, vomiting)  First breath triggered by pulmonary stretch receptors  Coughing and gagging are mediated by airway receptors (CGA)  Sneezing and yawning are mediated by pulmonary receptors (SYP) o Breuer-Hering reflex mediated by slowly adapting pulmonary stretch receptors (SAR)  Lung inflation SAR  vagus nerve  pump cells in NTS  VRG  E-Dec cellsexpiration prolonged inspiration terminated CSB346 Lecture 4 Rhythm generator - Network of interneurons that communicate with one another to produce a predictable and repetitive motor pattern (e.g., breathing, locomotion, chewing, swallowing, eye movements) o SLEC* - Activate a specific group of MNs in a certain sequence (e.g., inspiratory MNs must be activated before expiratory MNs) Respiratory rhythm generation (RRG) in brainstem - Transmitted in an orderly sequence to the respiratory muscles - Responds appropriately to inputs from other brain regions (e.g., limbic system) and peripheral afferents (e.g., pulmonary receptors) - Endogenously active (e.g., oscillates in the absence of conscious input) - Contains both inspiratory and expiratory cells o Augmenting (e.g., slow at beginning and fast at end; increase discharge freq
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