BCMB 230 1st Edition Lecture 20 Outline of Last Lecture I Relation of Lungs to Chest Wall II Ventilation and Lung Mechanics III Partial Pressure of Gases Outline of Current Lecture I Respiration Control II Plasma Glucose Levels and Regulation III Hormones IV Increasing Plasma Glucose Levels V Decreasing Plasma Glucose Levels VI Other Factors Current Lecture I Respiration Control Peripheral chemoreceptors responds to changes in arterial blood PO2 and H concentration carotid bodies chemoreceptor near main branching of carotid artery sensitive to blood O2 and CO2 content and H concentration aortic bodies chemoreceptor located near aortic arch sensitive to arterial blood O 2 content and H concentration Central chemoreceptors located in the medulla and also prove excitatory synaptic input to the medullary inspiratory neurons stimulated by an increase in the H concentration of the brain s extracellular fluid Plasma is critical used as a transient state When looking at oxygen hemoglobin dissociation curve see decrease in plasma PO 2 from 100 to 80 not much difference in hemoglobin saturation 40 to 20 hemoglobin saturation drops Oxygen is important in regulating breathing rates used as a secondary or tertiary signal A lot more CO2 is carried in plasma plasma PCO2 is a better indicator than O2 CO2 H2O H2CO3 H HCO3pH of plasma is the best indicator of breathing rate Brain protected by blood brain barrier permeability of capillaries is much tighter in the brain These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute things in blood can t get into interstitial fluid of the brain keep metabolic byproducts and toxins from moving from some other part of body into the brain ex lactic acid can t get into brain Central chemosensors in brain that detect pH strongest stimulus signal earliest warning best pH control Oxygen carbon dioxide and pH levels are important Information from thoracic cavity is important Oxygen levels in thoracic cavity do change breathing rate late warning system only in extreme cases II Plasma Glucose Levels and Regulation a lot of glucose in plasma makes it easy to supply muscles and brain with energy cells can use it to make ATP too much plasma glucose causes osmotic problems pulls more fluid in with osmotic pressure bulk flow does not go out into tissues need high enough level of glucose for ready supply of energy but need a low enough level so that it doesn t throw of pressure in capillaries III Hormones Hormones influence plasma glucose regulation hormones are produced and put into the blood by the endocrine gland blood takes it all over the body circulatory system is the connection between the gland and the target cells allows them to not have to be close to each other certain target cells in different places will respond to hormone need receptor for that hormone not all cells have receptors so they will not respond removal of hormones is by kidney or liver IV Increasing Plasma Glucose Levels To increase plasma glucose eat something sugary and carbohydrates glucose goes to pancreas and produce insulin receptors for insulin are on most body cells respond by increasing amount of glucose that moves from blood into the cell glucosetransporters move glucose into cell decrease plasma glucose to normal level cells can store glucose as glycogen or use it to make ATP not all cells have enzymes to make glycogen only liver or skeletal muscle can use the process of glycogenesis to produce glycogen maintains glucose gradient so we can keep moving glucose out of blood glyconeogenesis break down glycogen in skeletal muscle and liver gluconeogenesis break down glucose happens primarily in the liver some in the kidneys these processes are inhibited by insulin do not decrease plasma glucose levels in blood but keeps it from increasing maintains plasma glucose levels insulin acts to promote fat storage take fatty acid and put into fat cells forces cells to use glucose for energy and not fatty acids have plenty of glucose so we want this to happen insulin decreases plasma amino acids force ATP production to rely on glucose move amino acids into the cells increase protein synthesis decrease protein breakdown can t do this to all proteins can also use insulin to regulate amino acid levels along with glucose in the blood use feed forward response to anticipate a change happens after a meal parasympathetic stimulation causes secretion of insulin V Decreasing Plasma Glucose Levels plasma glucose level sends signal to different cells in pancreas releases a different hormone called glucagon glucagon opposes insulin in its action inhibits glycogenesis promotes glyconeogenesis and promotes gluconeogensis does not influence transport of glucose into cells through promotion of glyconeogenesis and gluconeogenesis increase glucose levels keeps it from going further down glucagon also acts on fat and protein synthesis promote utilization of fats decrease protein synthesis in liver hold off making new proteins to keep plasma amino acids use amino acids to make ATP gluconeogenesis Insulin inhibits release of glucagon and glucagon inhibits release of insulin stops a lot of fluctuation after a meal return to normal levels of plasma glucose quicker Third hormone somatostatin secreted by the pancreas inhibits GI tract glucose absorption decreases plasma glucose also reduces fluctuation of plasma glucose levels after a meal High plasma glucose somatastatin and insulin is released Renal threshold if blood glucose levels reach above this level glucose is excreted in urine high plasma glucose levels is associated with diabetes overindulgence kidney disease VI Other Factors Other factors hormones situations influence plasma glucose levels Some things demand more energy exercise stress growth In this situation do things to potentially increase glucose levels don t see levels go up because we are using that glucose Exercise stimulate adrenal medulla releases epinephrine increase plasma glucose levels by promoting glycogenolysis release glucose from stores release fatty acids mobilizing energy sources Stress stimulate adrenal cortex and adrenal medulla release cortisol and epinephrine drives plasma glucose levels up Growth hormone and thyroid hormones can also bring about increases in plasma glucose