Gaseous Exchange Flashcards
Why do organism need to breathe
All organisms, from simple, unicellular to more advanced multicellular organisms need oxygen (O,) to sustain cellular functions. Oxygen is used to release energy from carbohydrates found in cells. Plants and animals need energy for survival.
What is breathing
mechanical process of inhalation and exhalation through which air moves in and out of the respiratory organs enabling the uptake of oxygen and the removal of carbon dioxide
What is cellular respiration
the breakdown of organic compounds in the mitochondria of cells into organic products with the release of atp either aerobic or anaerobic
What is gaseous exchange
-exchange of 02 and CO2 at a respiratory surface occurring between the air and blood and blood and cells
Why does gaseous exchange need to take place
cells in the body continuously use oxygen during cellular respiration that results in the release of energy. At the same time, carbon dioxide is released. An accumulation of carbon dioxide will increase the acidity of the contents of the cell and eventually prove toxic. A living cell therefore requires a regular supply xygen and the constant removal of carbon dioxide.The cardio-vascular system transports these gases between the lungs and cells of the body.
What is the difference between cellular respiration, beating and gaseous exchange
CR- • Occurs in living plant and animal cells
B- • Involves inhalation and exhalation.
GE- • Occurs at two sites in the body, the lungs and in body tissues.
CR-• It is a chemical process.
B- • It is a mechanical process.
GE- • It is a physical process involving diffusion.
CR- • Glucose is broken down to release energy (ATP) and carbon dioxide
B- • Inhalation is when air is taken into the lungs.
• Exhalation involves the removal of air from the lungs
GE- • In lungs, O, diffuses from the air sacs into the blood, while CO, diffuses from the blood into the air sacs
• At the tissue level, O, diffuses from the blood capillaries into the bôdy Calls, while CO, diffuses from the
body cells into the blood capillaries.
What are the requirements for gaseous exchange
( structure / function )
The gas exchange surface area must be large enough to allow for the maximum intake of 0, and sufficient release of COz.
A large number of alveoli provide the large area for the exchange of gases. & their shape
The exchange surface must be kept moist for the gases to dissolve before diffusing and to prevent the drying out of the alveolar cells.
The secretions of certain cells lining the alveoli keep the surface moist
The exchange surface must be thin to facilitate diffusion.
The squamous epithelium of the alveolus is only one cell layer thick
An efficient transport system must be in close proximity to the exchange surface for the transport of gases.
Alveoli are richly supplied with blood capillaries cardio vascular
An efficient ventilating mechanism must be present to ensure a constant intake of 0, and removal of CO2.
The diaphragm and intercostal muscles between ribs provide an efficient mechanism for ventilation
There must be adequate protection for the delicate lung-tissue exchange surface.
The thoracic cage, consisting of the ribs, sternum and vertebral column protects the lungs.
How does inhalation work
Inhalation
• The diaphragm contracts and flattens, increasing the volume of the thorax from top to bottom.
• The external intercostal muscles contract, causing the ribs to be lifted upwards and outwards. The volume of the thoracic cavity increases sideways.
• Interpleural pressure (pressure between pleura)
decreases, causing a decrease in the pressure in the lungs.
• Since atmospheric pressure is now higher than pressure within the lungs, air rushes into the lungs via the nostrils.
How does exhalations work
Exhalation
• The diaphragm relaxes and is raised, decreasing the volume of the thorax from top to bottom.
• The external intercostal muscles relax, causing the rib cage to be lowered and become smaller. The volume of the thoracic cavity decreases sideways.
•• Interpleural pressure (pressure between pleura)
increases, causing an increase in the pressure in the lungs.
• Since pressure within the lungs is now higher than
atmospheric pressure, air is forced out of the lungs via the nostrils.
What is inhalation
Inhalation is the process of taking air into the lungs. It is the active phase of ventilation because it is the result of muscle contraction. During inspiration, the diaphragm contracts and the thoracic cavity increases in volume. This decreases the pressure so that air flows into the lungs.
What is homeostatic control of breathing
It is the body’s ability to maintain a constant internal environment in response to stimuli despite changes in external environment
Why does homeostatic control of breathing have to take place
Strenuous physical activity increases the body’s need for energy. This in turn, demands a greater intake o oxygen, whilst producing more carbon dioxide. When CO, levels in blood rise, the medulla oblongata responds by increasing the heart rate and the breathing rate. Hence more blood flows to the lungs, more 0 is taken up and more CO, is expired from the body.
Explain how homeostatic control of breathing works
• When the heart rate increases, blood flow also increases.
•Rapid transport of gases to and from the cells occurs.
• When carbon dioxide levels rise, the cells in the respiratory centre of the medulla oblongata of the brain are stimulated.
• Increased rate and depth of breathing causes the intercostal muscles and the diaphragm to contract and relax.
• More oxygen is inhaled, and more carbon dioxide is exhaled.
• The levels of carbon dioxide in the blood determine the rate and depth of breathing.
The ability of the body to return the levels the normal is known as homeostasis
Explain the steps of the negative feedback mechanism for homeostatic control of breathing:
- Carbon dioxide (COz) levels in the blood increase above normal levels
Receptor cells in the carotid artery in the neck are stimulated
Cells send impulses to the medulla oblongata in the brain
- Medulla oblongata stimulates breathing muscles (intercostal muscles and diaphragm) and heart
- Breathing muscles contract more actively - increases the rate and depth of breathing; the heart beats faster
More COs is taken to and exhaled from the lungs
The COz levels in the blood return to normal
Explain how gaseous exchange takes place in the lungs
Gaseous exchange in the lungs
The capillaries surrounding an alveolus have a high concentration of CO, and a low concentration of oxygen. Air in the alveolus has a high concentration of oxygen and a low concentration of CO,. This concentration gradient causes diffusion to occur. Oxygen dissolves in the moisture lining the alveolus and diffuses into the blood stream; CO, diffuses out of the blood stream into the alveolus. The oxygen forms a loose combination with haemoglobin of the erythrocytes (red blood corpuscles) to form oxyhemoglobin. A minimal amount of oxygen may dissolve in the blood plasma, where it is transported in solution form.
