[Biology Class Notes] on Interplay of Respiration, Circulation and Metabolism Pdf for EXAM

The interplay of respiration, circulation, including the metabolism, is a key to the respiratory system functioning as a whole. The cells set demand for the oxygen uptake and carbon dioxide (CO2) discharge, which means gas exchange in the lungs. The blood circulation will link the sites of the utilization of oxygen and uptake. The exact functioning of the respiratory system is based on both the ability of the system to make functional adjustments to differential needs and the design features of the structure sequence involved, which set the respiration limit.

Importance of Respiration

The major purpose of respiration is given as to provide oxygen to the cells at an adequate rate to satisfy their metabolic needs. This involves the oxygen transport from the lungs to the tissues by means of blood circulation. In the medieval and antiquity period, the heart was regarded as a furnace, in which the “fire of life” kept the blood boiling. Also, modern cell biology has already unveiled the truth, which is behind the metaphor. Every cell will maintain the mitochondria, which is given as a set of furnaces, through the foodstuff oxidation such as glucose, where the cell’s energetic needs are supplied. Therefore, the precise object of respiration is the oxygen supply to the mitochondria.

About Cell Metabolism

Cell metabolism depends upon the energy, which is derived from the high-energy phosphates like adenosine triphosphate (ATP), whose third phosphate bond may release an energy quantum to fuel several cell processes, such as the synthesis of protein molecules or the contraction of muscle fibre proteins. In this process, the ATP is degraded to the adenosine diphosphate (ADP), which is a molecule that contains only two phosphate bonds. To recharge this molecule by adding the third phosphate group needs energy derived from the breakdown of substrates or foodstuffs.

There are two pathways available as given below:

1. Anaerobic glycolysis, or the fermentation that operates in the absence of oxygen; and

2. Aerobic metabolism needs oxygen and involves the mitochondria.

The anaerobic pathway creates acid waste products and is resource-intensive: It means that when one glucose molecule is broken down, only two ATP molecules are generated. In contrast, the aerobic metabolism contains a higher yield (36 molecules of ATP per one molecule of glucose) and results in the “clean wastes,” which are water and carbon dioxide (CO2), which can be easily eliminated from the body and are recycled by the plants in the photosynthesis process.

The aerobic metabolic pathway is therefore preferred for any prolonged high-level cell activity. Since the oxidative phosphorylation takes place only in the mitochondria, and since every cell must produce its own ATP (where it cannot be imported), the number of mitochondria present in a cell reflects its capacity for aerobic metabolism or its required oxygen.

Adaptations

High Altitudes

The ascent from sea level to high altitude contains well-known effects upon respiration. The progressive fall in the barometric pressure is accompanied by a fall in the oxygen’s partial pressure, both in the alveolar spaces and ambient air of the lung, and it is the fall that poses the main respiratory challenge to humans at high altitude.

Humans, as well as a few other mammalian species such as cattle, adapt to the drop in oxygen pressure by the reversible acclimatisation process, which begins, whether intentionally or not, with time spent at high altitudes. Llamas, for example, are wild mountain animals with a heritable and genetically dependent adaptation.

Respiratory Acclimatization in the Humans 

Humans may achieve respiratory acclimatisation through activating pathways that raise oxygen partial pressure at all stages in the respiratory process, from the alveolar spaces in the lungs to the mitochondria in cells, where oxygen is needed for the ultimate biochemical expression of respiration. In the ambient partial pressure of oxygen, the decline is offset to a few extents by the greater ventilation that takes the deeper breathing form rather than a faster rate at rest.

What is the Role of Oxygen During Respiration?

The diffusion of oxygen through the alveolar walls into the blood is encouraged, and the alveolar walls are provided as thinner at altitude relative to sea level in a few laboratory animal experiments. The scarcity of oxygen at the high altitudes stimulates an increased production of red blood cells and haemoglobin, which increases the oxygen amount transported to the tissues. And, the extra oxygen is released by the increased levels of inorganic phosphates in the red blood cells, like 2,3-diphosphoglycerate (2,3-DPG).

With a prolonged altitude stay, the tissues develop several blood vessels, and, as the capillary density is increased, the diffusion path length along which gases must pass is decreased. It is a factor augmenting gas exchange. In addition, the muscle fibre size decreases, which also shortens the oxygen’s diffusion path.

Initial Respiration Response

The respiration’s initial response to the fall of oxygen partial pressure in the blood on the ascent to the high altitude takes place in two small nodules and the carotid bodies, which are attached to the division of the carotid arteries on any side of the neck. The carotid bodies expand as oxygen loss continues, but they become less vulnerable to the lack of oxygen. The thickening of small blood vessels in the pulmonary alveolar walls is related to low oxygen partial pressure in the lungs, as is a minor rise in pulmonary blood pressure, which is believed to boost oxygen perfusion of the lung apices.