Question

Given knowledge of local regulation of gas transport, the oxygen-hemoglobin saturation curve, and neural control of respiration, give at least five reasons why exercising muscles that use more oxygen and produce more carbon dioxide, lactic acid and heat would have more oxygen delivered to them.

Answer 1

Five reasons for the increase oxygen delivery to muscles during excersice are

a) increase in acidity

b) increase in intermediate metabolites such as 2,3DPG)

c) increase in the temp

d) increase in pCO2

e) INCREASE in heart rate and it's force of contraction

Explanation for factors a,b,c,d

FACTORS AFFECTING THE DISSOCIATION CURVE

The strength with which oxygen binds to hemoglobin is affected by several factors. These factors shift or reshape the oxyhemoglobin dissociation curve. A rightward shift indicates that the hemoglobin under study has a decreased affinity for oxygen. This makes it more difficult for hemoglobin to bind to oxygen (requiring a higher partial pressure of oxygen to achieve the same oxygen saturation), but it makes it easier for the hemoglobin to release oxygen bound to it. The effect of this rightward shift of the curve increases the partial pressure of oxygen in the tissues when it is most needed, such as during exercise, or hemorrhagic shock.

In contrast, the curve is shifted to the left by the opposite of these conditions. This leftward shift indicates that the hemoglobin under study has an increased affinity for oxygen so that hemoglobin binds oxygen more easily, but unloads it more reluctantly. Left shift of the curve is a sign of hemoglobin's increased affinity for oxygen (e.g. at the lungs).

Exercise causes an IMCREASE IN ACIDITY, TEMPERATURE AND INCREASE IN METABOLISM INTERMEDIATES (2,3DPG) and a decrease in oxygen in your muscle tissues. This causes an increased dissociation of oxygen from your blood flowing through your muscles, supplying them with much needed oxygen.

THUS, EXERCISE CAUSES OXYGEN-HAEMOGLOBIN DISSOCIATION CURVE TO SHIFT RIGHT DUE TO DECREASED AFFINITY OF HAEMOGLOBIN TO OXYGEN. THIS DECREASED AFFINITY TO OXYGEN PROMPTS RELEASE OF OXYGEN FROM HAEMOGLOBIN TO TISSUES MORE EFFICIENTLY.

(The Bohr effect describes how the affinity of hemoglobin for oxygen changes depending on the local biochemical conditions. An increase in acidity, temperature and the concentration of intermediate chemicals in the conversion of sugar to energy—specifically 2,3-diphosphoglycerate—decreases hemoglobin's affinity for oxygen, causing oxygen to diffuse into the tissues.)

Explanation of factor e

Excess carbon dioxide or excess hydrogen ions in the blood mainly act directly on the respiratory center itself, causing greatly increased strength of both the inspiratory and the expiratory motor signals to the respiratory muscles. Oxygen, in contrast, does not have a significant direct effect on the respiratory center of the brain in controlling respiration. Instead, it acts almost entirely on peripheral chemoreceptors located in the carotid and aortic bodies, and these in turn transmit appropriate nervous signals to the respiratory center for control of respiration.

three areas of the respiratory center: the dorsal respiratory group of neurons, the ventral respiratory group, and the pneumotaxic center. It is believed that none of these is affected directly by changes in blood carbon dioxide concentration or hydrogen ion concentration. Instead, an additional neuronal area, a chemosensitive area, is located bilaterally, lying only 0.2 millimeter beneath the ventral surface of the medulla. This area is highly sensitive to changes in either blood Pco2 or hydrogen ion concentration, and it in turn excites the other portions of the respiratory center.