APII Notes Home Page
Function of the Respiratory System
I). Function
A). Pulmonary Ventilation
B). External Respiration
C). Transport
D). Internal Respiration
II). Properties of Gases
A). Gas pressure is represented by a P
B). Dalton Law of Partial Pressure
The total pressure (P) = (Px + Py)
The partial pressure is proportional to its percentage in
the total gas mixture.
P µ
% of gas in mixture
C). Henry’s Law
Gases will dissolve in the proportion to its partial
pressure
III). O2 Transport
Hemoglobin-Oxygen Binding
The loading and
unloading of 1 O2
molecule enhances the ability of the
Hb to
load or unload the other
3 O2
molecules.
Hb loosely binds with O2
so the O2 breaks free when the
blood has reached the tissues.
Hemoglobin is almost saturated at 70mmHg only 9% of
atmospheric pressure.
IV). Hb affinity:
Hb affinity to O2
is measured on a dissociation curve.
A shift to the right and Hb affinity decreases
(lets go of O2 easily)
é H+
é CO2
é Temperature
A shift to the left and Hb affinity increases (grabs
O2 stronger)
§ pregnancy
§ long term
high-altitudes
§ organisms that
live in deep water
V). CO2
Transport
A). CO2 is
carried
- CO2 Dissolved
in plasma
- CO2
Chemically bond to hemoglobin
- CO2 is
converted to bicarbonate ions
CO2
+ H2O
« H2CO3
« H+ + HCO3-
carbon dioxide+ water «
carbonic acid « hydrogen + bicarbonate
buffer system.
if: blood pH is low (acidic) Ý
H+
H + can be removed by: H+
+ HCO3-
Þ H2CO3
If: blood pH is high basic) ß
H+
H+ can be added by: H2CO3
Þ
H+ + HCO3-
|
MNEMONIC |
|
ROME
|
Respiratory= Opposite:
· pH is high, PCO2 is down (Alkalosis).
· pH is low, PCO2 is up (Acidosis).
Metabolic= Equal:
· pH is high, HCO3 is high (Alkalosis).
· pH is low, HCO3 is low (Acidosis). |
B). Bohr effect: Declining pH (increase
acid) results in the increase of O2
unloading.
CO2
loading of RBCs
H+
+ Bicarbonate
O2
unloading of RBCs
C). Haldane Effect
The lower the PO2
of
blood, the more room for PCO2
\
VI). Respiration
Respiration is the exchange or diffusion
of blood gasses down a partial
pressure gradient.
(from high pressure or
concentration to low pressure of concentration)
External respiration involves exchange to the external
environment
Internal respiration involves exchange that occurs only with
the internal environment
VII) External Respiration
External air in the alveoli
to the blood in the capillaries
Gas exchange of CO2
and O2
occur because of a
pressure gradient.
(area of high
pressure to an area of low pressure)
A). Inspiration
Alveoli is high in O2
and low in CO2
Pulmonary capillary entering the alveoli is low in O2
and high in CO2
Blood is constantly moving through the system
so O2 will
diffuse from high concentration to low and enter the capillary
& CO2 will
diffuse from high concentration to low and enter the alveoli
B). Expiration
Alveoli is now high in CO2
(é PCO2
)
and lower in O2
(ê PO2)than
in inspired air but still high
Capillary exiting is low in CO2
and high in O2
Efficiency of gas exchange depends on
VI). Internal Respiration
A). When blood enters the tissues:
1). Tissue
: is high in CO2
(é CO2
) and low in O2 (ê
O2)
because cellular respiration constantly
uses the O2 to break down glucose
& constantly releases CO2
2). Arterial blood in the capillaries is low ê
in CO2 and high é
in O2
B). Gas exchange
CO2 leaves
the tissues & enters the capillaries through diffusion
O2 leaves
the capillaries & enters the tissues through diffusion
C). Venous blood leaves the tissues and it is high in CO2
and lower in O2
VII). Ventilation
A). Movement of air is based on Boyle’s Law
Change in volume a change
pressure a flow of gases
B). Inspiration
1). The thoracic cavity vacuum
2). diaphragm moves inferiorly
3). intercostal muscles contract
4). increases the volume
5). stretches the lungs and increases their volume.
6). Intrapulmonary pressure decreases relative to
atmospheric pressure.
7). Air flows in.
C). Expiration
1). The diaphragm and intercostal muscles
relax.
2). Decreasing thoracic volume.
3). Elastic fibers allow the lungs to recoil.
4). Decreasing lung volume.
5). Air is forced out
D). Factors affecting ventilation
E). Volumes
1). Respiratory Volumes
i). Tidal Volume
ii). Inspiratory Reserve Volume
iii). Expiratory Reserve Volume
iv). Residual Volume
2). Respiratory Capacity
i). Inspiratory Capacity
ii). Functional Residual Capacity
iii). Vital Capacity
3). Dead Space
VIII). Controls of Ventilation
A). Brain
Respiratory Center
1). Medullary Rythmicity Area
i). Dorsal Respiratory Group
ii). Ventral Respiratory Group
2). Pneumotaxic Area of the Pons
3). Hypothalamus:
4). Higher Cortical Functions
B). Chemical Signals
1). PCO2
Chemoreceptors sensitive to changes in the PCO2
CO2 + H2O «
H2CO3 « H+ + HCO3-
carbon + water «
carbonic acid « hydrogen + bicarbonate
é CO2
a ê pH
a
Rate of breathing increases
2). PO2
drop in PO2 at the chemoreceptors in the
aortic bodies of the aortic arch and
the carotid bodies of the carotid sinus
increase ventilation
