export_resp 34 Flashcards
what causes ventilation/perfusion (V/Q) inequality?
gravity
V/Q is ___ in higher lung than in lover
lower
PO2 is ___ in higher lung
higher
why isn’t PCO2 affected by V/Q inequality?
CO2 has a greater solubility
when do pulmonary capillaries reach pO2 of 100?
~25% of length
which part of the lungs does most blood flow through?
bottom
during exercise it takes ___ time to reach equilibrated PO2 (why?)
more, increased blood flow rate
hyperventilation
dec PCO2, inc PO2
normal P02 and PCO2
O2- 105mmHg
CO2- 40mmHg
hyporventilation
dec PO2, inc PCO2
CO2 ___ bronchiols
relaxes
pulmonary edema and affects on O2/CO2
fluid in lungs, inc diffusion distance, PO2 dec, PCO2 same (when ventilate to compensate or in sever cases, inc CO2)
pulmonary embolism
clots blocking arteries, dec flow to regions, dec PO2, more severe more inc PCO2
emphysema
walls of alveoli and caps broken down, inc resistance, dec surface area, PO2 dec, PCO2 inc with severity
pulmonary fibrosis
thickening of alveolar walls, inc diffusion distance, dec ventilation bc can’t expand lung, dec PO2, dec PCO2 with severity
asthma
narrowed airways, high mucus production, dec ventilation, dec surface area, dec PO2, inc PCO2 with severity
fick’s law
V= D*A*(P1-P2)/T -A= surface area
-T= thickness
D= solubility coeff
how is O2 carried in blood?
hemoglobin (4 binding sites/1)
resting oxygen consumption
250 ml/min
we hold 1L
hemoglobin structure
2 alpha
2 beta
1 heme in each
what is PO2 measuring?
O2 disovled in plasma
what happens to PO2 in blood?
when PO2 alveoli > PO2 blood, diffuses into plasma, binds to Hb, released when PO2 blood > PO2 tissues
what % of O2 is released to tissues?
25
what effects Hb saturation curve?
dec pH/inc H+ (right) inc temp (right)
inc PCO2 (right)
inc 2,3DPG (right)
what are DPGs?
- produced by RBCs during anaerobic glycolysis
- produced in response to hypoxia
how does CO2 exist in blood?
1) dissolved in plasma (10%)
2) globin-bound (30%)
3) bicarbonate (HCO3-) (60%)
CO2/HCO3 equation
CO2+H2O H2CO3 HCO3- + H+
enzyme used in carbonic acid eq?
carbonic anhydrase
pH is ___ in venous blood than arterial
lower
3 peripheral chemoreceptors
1) aortic
2) carotid
3) axons to medulla oblongata
what stimulates chemoreceptors?
dec PO2, dec pH, inc PCO2
central chemoreceptors
in brain, measure PCO2 change in inerstitial fluid, go to medulla oblongata
how does brain pH change?
blood PCO2 > brain ECF PCO2, CO2 into brain and dec brain pH
are central receptors sensitive to PO2 or H+?
NO
when does ventilation change start (PO2)? what is responsible for this change?
60 mmHG
peripheral receptors
what is responsible for ventilation change (PCO2 and H+)
central and peripheral chemoreceptors
what drives ventilation inc during exercise?
pH (lactic acid)
where do the peripheral chemoreceptors signal to?
medullary inspiratory center
pH of blood is ___ in arterial blood vs venous
higher
what is the CO2 buffer in cells?
proteins (globin)
what is respiratory acidosis? alkalosis?
inc PCO2, inc H+, dec pH
dec PCO2, dec H+, inc pH
how does respiration compensate for metabolic acidosis? alkalosis?
hypoventilation (inc CO2, H+)
hyperventilation (dec CO2, H+)
venous PO2
PCO2
pH
100mmHg
40mmHG
7.4
arterial PO2
PCO2
pH
40mmHg
45mmHg
7.36
Pre-Botzinger
pacemaker cells of respiratory center (in medulla oblongata)
how does the respiratory center control inhale/exhale?
pre-botzinger –> VRG/DRG –> motor neurons –>diaphragm/intercostals –> contractions
pneumotaxic/apneustic center
in pons, send signals to pacemakers
types of inputs to pre-botz?
sensory (PO2, pH, PCO2, stretch, irritants), pons, cortex (voluntary)
action potentials cause?
inspiration
what causes expiration?
stopping of APs (passive)
what changes depth of breaths?
frequency of APs in burst
how does gas exchange occur?
diffusion down the pressure gradient
gas exchange direction at alveoli
- CO2 into alveoli
- O2 into blood
gas exchange at cells
- CO2 into blood
- O2 into cells
what does partial pressure measure?
gas concentration in blood
what is the pressure of CO2 in the air?
neglegible
what determines gas concentration?
solubility and partial pressure
what is more soluble, O2 or CO2?
CO2 - 24x
what do central chemoreceptors sense?
CO2 in brain
