Chapter 18 Flashcards
VO2
The ability to INTAKE,
TRANSPORT and
UTILIZE oxygen
VO2
The ability to INTAKE,
TRANSPORT and
UTILIZE oxygen
Oxygen is transported in the blood in two ways:
Bound to hemoglobin on RBCs. (Majority)
Dissolved in plasma.
At rest
Hemoglobin and plasma
Fully saturated Hemoglobin can carry ~20 mL O2/L blood
Plasma can maximally dissolve ~0.3 mL O2/L blood
Ficks Equation
VO2 = Q x A-V O2 difference
Q = HRxSV
Q = Cardiac output: total O2 content of Arterial and Venous
Total O2 content in Red Blood cells
PER 100ML OF BLOOD
Amount of Hemoglobin X Amount of O2 Bound to hemoglobin X % Saturation at a given PO2
Amount of Hemoglobin = 15/100
Oxyhemoglobin
HbO2
Found in Heme group
Has iron in the centre
1g of Hb transports 1.34ml of O2
Saturation of A and V blood
Saturation of Arterial blood is 100%
Saturation of Venous blood is closer to 75%
Partial Pressure of O2
Alveoli, Arterial blood, cells, Venous blood
Alveoli - 100 mmHg
Arterial blood - 100 mmHg
cells - ≤40 mmHg
Venous blood - ≤ 40 mmHg
Partial Pressures of CO2
Alveoli, Arterial blood, cells, Venous blood
Alveoli - 40 mmHg
Arterial blood - 40 mmHg
cells - ≥46 mmHg
Venous blood - ≥46 mmHg
Higher altitude and O2
Decreases pressure of O2
Higher altitude and O2
Decreases pressure of O2
Hypoxia
too little oxygen
Hypercapnia
increased concentrations of carbon dioxide
PH of Blood
7.37
Effect Gas exchange
Surface area (Emphysema
Diffusion barrier permeability
Diffusion Distance
98%
oxygen binding to Hb
Effects on O2 binding to Hb
pH. (goes down during exercise)
Temperature.
CO2. (More)
2,3-Diphosphoglycerate (2,3-DPG). (more glycolosis)
CO2 Transport (3)
Dissolved in plasma. (7%)
Combined with bicarbonate (HCO3-) ions
Bound to Hb. (23%)
CO2 role in Ventilation
Primary stimulus for ventilation changes
O2 and H+ play less of a role
Respiratory neurons in the medulla
control inspiratory and expiratory muscles
Rhythmic pattern
spontaneously discharging neurons
Ventilation is subject to
continuous modulation by chemoreceptor- and mechanoreceptor-linked reflexes and higher brain centers
Ventilation is subject to
chemoreceptor- and mechanoreceptor-and higher brain centers
How to stimulate peripheral chemoreceptors
PO2 must fall below 60 mmHg
How do central Chemoreceptors work in the body?
Central chemoreceptors monitor CO2 in cerebrospinal fluid
- (the sensors are built into the fluid)
- We are trading off H+ and CO2 in this process (this is buffering)
- The central receptors do not directly interact with CO2 (it is a secondary messenger system)
