Physiological Reinforcing Concepts pt5 PDF

Flow ● Gravity ○ Blood flow is greater at the base and less at the apex because gravity pulls blood down to the base of the lungs ○ In addition, the base has less vascular resistance and greater transmural pressure (Pc - Palveoli) ○ Zone 1: Apex of lungs ---> Pressure in alveoli is the greatest (l...

Flow ● Gravity ○ Blood flow is greater at the base and less at the apex because gravity pulls blood down to the base of the lungs ○ In addition, the base has less vascular resistance and greater transmural pressure (Pc - Palveoli) ○ Zone 1: Apex of lungs ---> Pressure in alveoli is the greatest (low transmural pressure) and pressure in the pulmonary veins is lowest ■ Flow is more or less 0 here because pressure is alveoli is so great vessels are collapsed ○ Zone 2: Middle of lungs ---> pressure in pulmonary artery is greatest and pressure in pulmonary vein is lowest ■ This is a potentially collapsible state for the vessels where flow is equal to Pa - PA ○ Zone 3: Base of lungs ----> pressure is greatest in the pulmonary arteries and least in the alveoli ■ Flow is equal to Pa - Pv meaning that the pressure in the alveoli is too small to ever collapse the vessels and it is therefore non-collapsible ● Ventilation - Perfusion - Diffusion: An overview ○ Conducting zone = Vt = tidal volume x respiratory rate ■ PO2 = (Patm - 47)FIO2 ■ FIO2 is 0.21 or 21% ○ Respiratory zone = Va = (TV - ADS) x RR ■ ADS is the anatomical dead space = 1mL/lb ■ Average person = 150 mL ● ● Conducting zone = Trachea down to terminal bronchiole ○ No gas exchange ---> “dead space” Respiratory zone = Respiratory bronchioles to alveolar sacs ○ Gas exchange happens here ○ Acinus = region supplied by primary respiratory bronchiole (respiratory zone) ○ Terminal respiratory unit = 3 acini Spirometry ● ● ● ● ● Palveoli = Precoil + Pintrapleural End Expiration: ○ No flow condition bc Palveoli = Patm ○ Volume (RV) is determined by Ptl and lung compliance End Inspiration: ○ Also no flow condition ○ Pintrapleural is now more negative ○ And Recoil pressure is larger, equal and opposite to intrapleural pressure ○ As you increase volume, the recoil force will increase! Dynamic Inspiration: ○ Once the intrapleural pressure decreases the alveoli expand ○ The pressure in the alveoli decreases ○ As air enters, the pressure in the alveoli decreases less and less ○ Once pressure in the alveoli = Patm then inspiration has ended Q = Patm - Palv / Rairway ● Helium Dilution ○ Measures FRC and RV ○ Spirometer is loaded with helium (usually 10%) while valve is closed. At FRC valve is opened for 5 mins until the lungs equilibrate. Then the concentration of He is measured again. ○ VL x FL_start + Vsp x Fsp_start = (VL + Vsp) FL_end with FL_end = FL_start ■ FL_start = 0 ■ VL = 0 ■ Vsp = 3000 mL ■ Fsp_start = 10% ■ Fsp_end 5% ■ (0 x 0) + (.10 x 3000) = 0.05 (FRC + 3000) ● FRC = 3000 ■ From here we can calculate RV using the formula RV = FRC - ERV ● ERV is measured with the spirometry (is the Vp number in this case 3 L) Lung Forces ● ● Compliance of the lung is low until you reach enough pressure to open the alveoli against surface tension ---> then compliance increases with increasing volume until a certain max threshold is met C=V/P ○ Can be reduced by scarring, fibrosis, edema, or decreased surfactant ● ● FRC = point where forces are equal and opposite!! Inspiration: ○ Lung force increases ○ Chest force decreases ● ● Resistance is greatest in upper airways ○ Largest values in the bronchi due to size, and branching Resistance decreases with increasing volume Endocrine System ● ● ● ● ● ● Peptide = hydrophilic and can be stored, travel freely in blood ○ Synthesis is via Gs or Gq Steroid = transported via plasma proteins in blood ○ Synthesis from cholesterol ○ Can affect gene transcription Amines = derived from tyrosine, some are hydrophilic and some hydrophobic ○ Carried by thyroid binding globulin Binding globulins increase the half life and hormones Regulated by Feedback Mechanisms ○ Negative Feedback = directly or indirectly inhibits secretion of hormones ■ Ultra short inhibits its own secretion ■ Short = anterior pituitary inhibits the hypothalamus ■ Long loop = end hormone inhibits the whole hypothalamic - pituitary axis ○ Positive Feedback = stimulates further hormone release ■ Ex: estrogen and oxytocin both increase their own hormone release Pituitary ○ Anterior (adenohypophysis) = glandular, releases hormones ■ Regulates reproduction, growth, energy and stress ■ Somatotrophs ----> Growth hormone ■ Thyrotrophs ----> Thyroid stimulating hormone ■ Corticotrophs ----> Adrenocorticotropic hormone ■ Gonadotrophs ---> Follicle stimulating hormone ■ Gonadotrophs ----> Luteinizing hormone ■ Lactotrophs ----> prolactin ○ Posterior (neurohypophysis) = neural, releases neurotransmitters ■ Oxytocin ■ Antidiuretic hormone (aka: anti-vasopressin hormone) Endocrine System Cont. ● ● ● Steroid hormones come from the cortex ○ GFR = Glomerulosa, fasciculata, reticularis ○ “GFR ---> Salt, sugar, sex” ○ Steroids are synthesized from cholesterol ■ Cholesterol desmolase (CYP 11A1) is the RLS and requires the Star protein! Hypothalamic - Pituitary Axis ○ Hypothalamus releases GnRH which binds gonadotroph receptors on the ant. Pituitary ○ Ant. pituitary releases FSH and LH (glycoproteins) ■ LH is released more heavily in Males ----> testosterone ■ FSH ----> spermatogenesis ■ Inhibin inhibits FSH Hypothalamic - Ovarian Axis ○ Hypothalamus releases GnRH which binds gonadotrophs on the ant. Pituitary ○ Ant. Pituitary releases FSH and LH ■ LH ---> theca cells ■ FSH --> granulosa cells ■ Both help regulate menstrual cycle ● ● Vasopressin (ADH) ○ V2 receptors (Gs) regulate osmolarity by increasing H2O reabsorption ○ V1 receptors (Gq) constrict smooth muscle cells Oxytocin ○ Causes let down of milk from breasts ○ Uterine contractions during birth ○ Up regulated during childbirth ○ Can also be used to control postpartum bleeding Digestion ● ● ● Smell ○ ○ ○ ○ ○ Activates salivary glands which release bicarb, amylase and lipase Activates stomach acid, pancreas and gallbladder All controlled by CNS Bicarb neutralizes the acid Clinical Correlation: ■ Sjogren’s Syndrome = autoimmune destruction of salivary glands ---> dry mouth and eyes Pancreas ○ Release digestive enzymes (lipase) and bicarb ○ Insulin and glucagon ○ Cystic Fibrosis: decreased production of lipase ----> fat malabsorption Regulation ○ Somatostatin from the GI tract inhibits the release of all GI hormones and gastric acid secretion ○ Gastrin from G cells in the stomach ■ Increases H+ secretion ■ Stimulated by distention of the stomach, GRP, tryptophan ■ Inhibited by H+ and somatostatin ■ Zollinger Ellison: endocrine tumor that leads to excess gastrin production ---> excess H+ secretion ---> ulcers and many of them (PUD) ● ● CCK ○ From I cells ○ Contraction of the gallbladder ---> relaxes sphincter of Oddi --> bile secretion ○ Stimulates secretin ---> bicarb ○ Inhibits gastric emptying ○ Stimulated by small peptides and amino acids, fatty acids and monoglycerides GLP 1 ○ Stimulates insulin and decreases glucagon Digestion ● ● ● Salivary Glands ○ Secrete saliva ■ Water, bicarb, mucins, amylase, lysozyme, growth factors ○ Regulation ■ Parasympathetic ---> stimulates watery, abundant saliva production and secretion ■ Sympathetic ---> reduces saliva production and produces thick mucus saliva Achalasia ○ Inability to swallow both solids and liquids bc of denervation of the LES ○ This results in INCREASED tone ---> food can’t pass to stomach ○ Different from cancer which is progressive swallowing problem from liquids to solids ● Esophagitis is inflammation of the esophagus due to acid from stomach refluxing up as a result of little LES tone ○ Pill esophagitis ■ Older people have trouble swallowing large pills ---> they get stuck and cause inflammation ■ Common agents = Potassium tablets GERD ○ Incompetent lower esophageal sphincter ---> acid from stomach backflows into esophagus ○ Heartburn is the main symptom ○ Treat with proton pump inhibitor ---> reduces H+ content in the stomach Digestion ● ● ● Motility ○ Migrating Motor Complex ■ Constant sweeping of contractions that continually move through the stomach to prevent large amounts of indigestible materials from accumulating ■ Initiated by Motilin ● If you have a motility disorder then you are deficient in motilin ■ Gastric secretion, bile flow and pancreatic secretion increase ○ Patterns ■ Propulsive = peristalsis (ring like contractions) that move food forward ■ Mixing = segmentation that helps chop food up Slow Wave ○ Oscillating resting membrane potentials of GI smooth muscle ○ Rhythmic depolarizations initiated by pacemaker cells that move food from mouth to anus Dumping Syndrome ○ After bariatric surgery where the stomach is made smaller, the patient has to eat small frequent meals ○ If large meals are eaten, glucose is absorbed too fast leading to hyperglycemia ○ The hyperglycemia results in a secretion of insulin that leads to hypoglycemic symptoms ■ Weakness, dizziness, and sweating after meals