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partial pressure of oxygen in the alveoli (calculation )
P_CO2 (40mm Hg always) P_H2O (47mm Hg always) P_O2 is obtained by (sum of partial pressures of O2 and H2O in conducting airways) - (sum of the two above) = 197-87= 100mmHg
disease states where you get increased thickness
1. pulmonary fibrosis 2. pneumonia(buildup of INFLAMMATORY fluid in and around alveolar space eg. empyema ) 3. pulmonary edema(buildup of fluids in the interstitium due to lung damage or left heart failure)
SaO2 is measured by what instrument?
a pulse oximeter, shining lights through finger or pinna, from light attenuation,can determine SaO2 (principles: Hg with O2 absorbs more light )
definite Bohr shift and the factors that enhance Bohr shift to the right.
Bohr shift: shifting of the oxygen -Hg disassociation curve, towards right means decreased affinity of Hg for O2 factors: higher temp, PCO2, 2,3-DPG, [H+] shifts curve to the right These factors exist when we are exercising; physiological importance of the Bohr effect is decreased Hb affinity for O2 while we exercise, so Hb can unload O2 to our tissues more easily.
define the Haldane effect
Deoxygenation of the blood increases its ability to carry CO2; conversely oxygenated blood has a reduced capacity for CO2 Molecular explanation: CO2 + H2O → H2CO3 → H+ + HCO3- this is carbonic anhydrase\'s action. According to Le Chatelier\'s Principle, if we remove H+, reaction will shift to the right. DEOXYGENATED Hb can remove the H+ a lot more efficiently than oxygenated Hb. Thus, in an environment without oxygen, deoxygenated Hb binds H+, shifting reaction to the right to make more HCO3-, which can bind more CO2.
respiratory centers and their function
1)DRG: for inspiration (only receives input from peripheral sensors) 2)VRG: for forced expiration mnemonic: DiVe 3)pontine nuclei a) pneumotaxic center(PTC): inhibits respiration b) apneustic: promotes inspiration and inhibits PTC
which 5 inputs to the medulla controls breathing rhythm
1. Hering-Breuer reflex (stretch receptor in lungs) 2. central and peripheral chemoreceptors 3. voluntary control 4. emotional states from limbic system 5. somatic senses
Hering-Breuer Reflex
-the stretch receptors regulate distention of the lungs, prevent overexpansion -reflex is regulation by VAGUS IT DOESNT determine breathing rate and depth in normal humans, only newborns or if tidal volume >1L
partial pressure of oxygen in conducting airways (calculation )
P_H2O (47mmHg always) P_O2 is obtained by (760-47)*0.21=150mmHg
relationship of partial pressure and the gas \'s solubility
higher solubility, higher partial pressure (eg. CO2 has 20x solubility of oxygen )
fick\'s law of diffusion
flow of gas is proportional to: A(Diffusivity)(delta _P) / T
diffusivity is proportional to
solubility / √MW
disease state where you get decreased surface area
emphysema
regarding pulmonary transit times in healthy and sick patients
in healthy or pulmonary fibrosis patients, pulmonary transit time will be fixed at 0.75s at rest and 0.5s in exercise for healthy people, only 0.25s is required. But in pulmonary fibrosis, more than 0.5s is needed, so for them, 0.75 at rest is adequate, but when it comes to exercise, it is not enough. - healthy,elite atheletes: <0.25 secs given, incomplete gas exchange
discrepancy: CO2 has delta P=6, O2 has Delta P=60, why do they have the same diffusion rate in blood and alveoli?
explanation: CO2 has 20x solubility of O2 *solubility in plasma, interstitial fluid, pulmonary surfactant
what is SaO2?
saturation of Hg by oxygen
significance of the plateau region of the O-Hg dissociation curve
the plateau region is wide (60-100), this provides a safety measure, or a buffer zone: even when PO2 drops slightly (as in high altitude) , the SaHb still wont fall dramatically *the plateau region is due to most Hg already having a (4/4) configuration
significance of steep region in the oxyhemoglobin dissociation curve.
the wide steep region (40-10) has a corollary, this corollary is helpful physiologically: a slight drop in PO2 in tissues (eg. during exercise ) will cause SaHb to drop dramatically. the decreased affinity makes it easy for oxygen to unbind and enter tissues
in anemia, what remains normal?
SaHb remains normal. In anemia, the # of Hb is reduced, so total amount of O2 carried will be reduced. However, the hemoglobin molecules are normal, so their saturation will remain normal. (the oxyhemoglobin dissociation curve in anemia will be shrunk down, but the shape will be the same.
NERVES that innervate respiratory muscles
-C345 innervates the diaphragm -thoracic t7-t12, l1 nerves innervate the intercostal and abdominal muscle -cranial nerves innervate upper airway dilator muscles
where are the central chemoreceptors found and what they mainly regulate.
they are found in the brain ECF, somewhere below medulla, and mainly regulate arterial blood PCO2 (by detecting a drop in pH, in other words, it doesn\'t really directly measure PCO2); its range of monitor is between 35-45mmHg normal range drop in pH is a corollary of an increase In plasma PCO2 mnemonic: Central receptor regulate PCo2
Where are the peripheral chemoreceptors and what they regulate?
-One at carotid sinus (by CnIX), one at aortic arch (by CnX) (referred to as bodies) -mainly sense super-emergency situations (PO2 < 60mmHg) 1.they mainly detect and regulate PO2 -central chemoreceptors has little to do with PO2 regulation 2. they also regulate plasma pH and PCO2
when we say the peripheral chemoreceptors and mechanoreceptors feedback input into the medulla, which structure do these receptors feedback into?
DRG
consequences of ablating PTC; of apneustic center
PTC is an off -switch for inspiration; if you ablate it, inspiration will be deeper and will hold longer apneustic center delays PTC\'s off switch and promotes inhalation; ablation will cause inspiration and a long long delay before expiration
difference between central and peripheral chemoreceptors, aside from their location
1. central senses PCO2 via detecting pH changes; peripheral actualy senses both PO2 and pH 2. central is slow(have to wait for ca to convert CO2 to bicarbonate and H+; peripheral is fast (everything is a direct measurements )
are peripheral chemoreceptors often useful in detecting PO2 drops? when are they actually employed?
it only triggers inspiration if arterial blood PO2 <60mmHg. Which means at sea level, peripheal chemoreceptors rarely trigger inspiration due to a drop in PO2 (it rarely drops below 60) . -it becomes very useful in emergency arterial hypoxia (eg. at high altitudes)
what\'s so danger about hyperventilation then diving?
hyperventilation causes the blood to contain lots of O2 and little CO2. after diving for a while, PO2 is not low enough to trigger a breathing signal, and PCO2 is not high enogh to trigger a breathing signal either. but actually at this point, oxygen levels are already too low for brain (still OK for muscles though ), so you get cerebral hypoxia --> brain death
natural causes for acid (NON-CO2 in origin ) in blood
1. lactic acid fermentation from muscles 2. diabetic ketoacidosis *these acid can stimulate peripheral chemoreceptors and ths trigger ventilation too. * These acids will not cross the Blood brainbarrier and thus will not stimulate central chemoreceptors.
describe in what forms O2 and CO2 are carried in blood
oxygen: 2% dissolved 98% bound to Hemoglobin Carbon dioxide: 7% dissolved 70% dissolved as bicarbonate ion 23% combined with Hb to form carbaminohemoglobin
the shape of the oxyhemoglobin dissassociation curve (SaHb VS PO2 ) is
sigmoidal
when position of the oxyhemoglobin dissociation curve shifts to the right, Hb affinity for oxygen
decreases. mnemonic: dR. Li decreases right. left increases
in carbon monoxide poisoning, the oxyhemoglobin dissociation curve is shrunk down and shifted to the left, why the shift to the left?
because carbon monoxide make it hard for oxygen to unload. --> it seems like Hb affinity for O2 has increased.
what is the chloride shift
Refers to the exchange of HCO3- and Cl- across a red blood cell channel. The passage of Cl- is to balance charges.
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