Respiratory Physiology II ( Lectures 46 - 49) Flashcards
Gas exchange in lungs and tissues involves diffusion of ____ and _____ from regions of ______ to ___
CO2 and O2
higher partial pressure to lower partial pressure
The total pressure of gas is the sum of _______
pressures of individual gases that make up the mixture
What is the partial pressure of a gas
Proportion of pressure of the entire gas that is due to the presence of the individual gas
(T/F) pressure equilibrium is the same as concentration equilibrium
False
Pressure equilibrium is not the same as the concentration equilibrium. The ability of gas to dissolve in water depends on the solubility of the gas
Because oxygen has _____ solubility in water, the evolution of ______ developed
low
oxygen-carrying molecules in the blood
_____ is 20 times more soluble in water than is ____
Carbon dioxide
oxygen
Partial Pressure of O2 and CO2 travel. Explain
- O2 ( 100mm Hg) from the alveoli travels down the partial pressure gradient to the capillaries (40 mmHg)
- Diffusion goes to equilibrium, and the PO2 of the arterial blood leaving the lungs is 10 mmHg
- When arterial blood reaches the capillaries, the gradient is reversed,, the intracellular PO2 is < 40 mmHg and O2 travels down its partial pressure gradient ( plasma to cells)
- PCO2 of arterial blood is 40 mmHg which is lower than the 46 mmHG PCO2 in cells, therefore CO2 diffuses out of the capillaries into the plasma.
Each liter of systemic arterial blood normally contains _____ ml of O2
200
OUt of the ____ml of O2, _____dissolves in 1 Liter of blood and the other _____ is transported in _____, ____ combined with _____
200
3 mL
197 mL / erythrocytes
reversibly combined with Hb
Each _____ molecule is a protein made up of _____ bound together
Hb
4 subunits
Each subunit of Hb contains a ____ molecular group and a _____ attached to it. Each of the four _____ groups contains _____ .
heme
polypeptide
heme
one iron atom which the O2 binds to
The equation for the _____ reaction between O2 and Hb is ____
reversible
O2 + Hb = HbO2
The O2- Hb dissociation curve examines the relationship between _____
partial pressure of O2 and hemoglobin saturation
At normal alveolar pressure (____ mm Hg) , ___% of the Hb is bound to O2
100
98%
As blood passes through the lungs under normal conditions, Hb picks up nearly _______ of O2 that it can carry
maximal amount
(T/F) The more the partial pressure of O2 the more the hemoglobin saturation
False, it stops at around 98% saturation. Any pressure above 100mmHg would make only minor changes to Hb % saturation
When Alveolar Partial pressure is > ____ mm, >90% of Hb is saturated
60
After _____ , a small decrease in PO2 causes a ___ release of _____
60 large O2
The binding of O2 with Hb is an example of ____ . Explain
cooperativity
Each subunit in the Hb can combine with one molecule of O2, the reactions of the four subunits happen sequentially, helping the next one.
Deoxygenated Hb have a low affinity for O2, the binding of O2 to a heme molecule breaks down subunit bonds that leaves the other O2 binding sites to be more exposed
Therefore, the binding of one deoxyhemoglobin increases the affinity of the remaining sites on the same Hb molecule
A left shift of curve means ____ O2 affinity and ____ unloading of O2.
A right shift of curve means_______ O2 affinity and _____ unloading of O2
greater , less
less, more
What affects hemoglobin saturation and how does it affect
DPG concentration / Temperature / pH
– increased level of DPG, acidity, and temperature metabolizes activity which causes more unloading, a right shift to the curve, lower affinity
– a decrease in these factors causes the dissociation curve to shift left, therefore, Hg has a greater affinity for O2
Fetal HB has ____ affinity for O2 than adults becuase _____
higher
needs to oxygenate blood from exchange with maternal blood
_____ has higher affinity for O2 than ___ .
Myoglobin
Hb
Hb has ___ affinity for CO2 than O2
higher
What are the 3 ways that CO2 is transported in the blood. Percentages
- dissolved (7%)
- converted to bicarbonate (70%)
- binds to hemoglobin (23%)
While CO2 is more ______ in body fluids that O2, only about ____% of CO2 carried by the venous blood is ______ in the blood. The remaining _____ % diffuses into RBC.
soluble
7% / dissolved
97%
Explain the conversion of bicarbonate ion
Conversion to CO2 to bicarbonate ion depends on the presence of carbonic anhydrase (CA) found in RBCs
Diffused CO2 goes to the RBC and interacts with H2O with the presence of CA.
Carbonic Acid dissociates readily to form bicarbonate ions
Conversion to bicarbonate ion is a _____ reaction
reversible
it depends on substrate concentration and law of mass action
What are the 2 mechanisms that remove free H+ and HCO3- from RBC
1) An antiport protein exchanges HCO3 for Cl – this is called the chloride shift
2) Deoxyhemoglobin acts as a buffer and binds with the H+ in the reaction.
Binding of CO2 to Hb forms ____
carbaminohemoglobin
Put the whole transport process together
- CO2 diffuses out of the cells into the systemic capillaries
- About 7% of it is dissolved within the plasma
- 23% of it binds to Hb forming carbaminohemoglobin
- 70% of the CO2 is converted to bicarbonate and H+.
Some of the hemoglobin buffers H+ while some HCO3- enters the plasma in exchange for the Cl-
- At various stages, CO2 is transported into the lungs
5. At the lungs, dissolved CO2 diffuses out of the plasma
6. By the law of mass action, Co2 uninds from Hb and diffuses out of RBC
7. Carbonic acid reaction reverses pulling HCO3 back into the RBC and converting it back to CO2
- At various stages, CO2 is transported into the lungs
(T/F) oxyhemoglobin has a greater affinity for H+ than deoxyhemoglobin
False.
Deoxyhemoglobin has a higher affinity for H+ than oxyhemoglobin
Explain carbaminohemoglobin
About 23% of the CO2 leaves the venous blood and binds to Hb directly.
When O2 leaves the binding sites on the Hb molecules, CO2 binds with free Hb exposed amino groups forming carbaminohemoglobin
The diaphragm and intercostal muscles are ____ muscles
skeletal
Breathing depends entirely upon _____ excitation by the _____.
cyclical respiratory muscle
motor nerves
Inspiration is initiated by a______ in the _____ to inspiratory muscles.
When the ____ cease, the ______ relax and expiration occurs as the elastic lungs recoils
burst of action potential
spinal motor nerves
action potentials
inspiratory muscles
(T/F) During exercise, nerves still do not contract during expiration
False
During exercise, contraction of expiratory muscles facilitates expiration, nerves to these muscles will start to fire
What controls the activity of the inspiratory spinal motor neurons ? Location? Explain
The integrating center for the control of breathing is located in the medulla oblongata. This medullary respiratory system is located in the RF.
Within the medullary respiratory system, there is a small group of pacemaker cells called the pre-Botzinger complex located on each side of the medulla.
These neurons fire rhythmically and produce rhythmic discharges in the phrenic neurons
Inspiratory and expiratory neurons in the medulla show _____, which is …
reciprocal inhibition
motor neurons to the expiratory muscles are inhibited when those supplying to the inspiratory muscles are active
they alternate !
The ______ of the ____ fine-tunes the transition between inspiration and expiration.
Pontine respiratory group
Pons
The actions of the pons and medulla are modulated by the ____, which is (voluntary/ involuntary)
cortex which is voluntary
What are the pre-Botzinger complex
They include pacemaker cells which are located on either side of the medulla.
These neurons will fire rhythmically to produce rhythmic discharges in the phrenic neurons
