In the examination center of junior high school biology on breathing and movement, some students were confused and repeatedly made mistakes. I summarize the graphic questions about breathing movements that are commonly tested in the middle school entrance examination here, hoping to help these students.
Where to start? Let's start with the concept of breathing exercise, as shown in the figure.
This refers to the movement of breathing during calm, and there are two groups of muscles involved in respiratory movements: the intercostal muscles and the diaphragm muscles. Why the emphasis on breathing exercises? Because, scientifically, most of the questions examined in the following examinations are related to breathing movements, as shown in the questions.
Students are confused by graphic transformations such as Circle 3 and Circle 4, with an emphasis on Circle 3. Circle 3 analysis is based on the difference between the pressure inside the lungs and the outside air pressure to judge the inhalation and exhalation, the external air pressure we use physical terms, is 1 standard atmospheric pressure, understand no.
Well, first look at the left figure of circle 3, this is to take the horizontal axis of the coordinate system as external air pressure, that is, 1 atmosphere pressure, the curve ABC indicates the change of air pressure in the lungs, AB is below the horizontal axis, what does it mean? It means that the air pressure in the lungs is less than the external air pressure, the air pressure in the lungs is less than the external air pressure, and the external gas enters the lungs through the respiratory tract, which is not inhale; in the same way, BC is above the horizontal axis, indicating that the air pressure in the lungs is greater than the external air pressure, the pressure in the lungs is greater than the external air pressure, and the gas in the lungs is discharged through the respiratory tract. Points A, B, and C are on the horizontal axis, indicating that the pressure in the lungs is equal to the pressure outside.
Look at the picture, variant one, to put it bluntly, this figure is not to take the horizontal axis of the coordinate system as external air pressure, but to move up a unit, the unit of the coordinate system as the external air pressure, and then analyze the change of the curve ABC, it is exactly the same as the left figure, change the soup without changing the medicine.
Look at the figure on the right, variant two, which is an improvement on the basis of the middle figure, which is the most tested graphic conversion question in recent years. Or move a unit upward in the coordinate system as external air pressure (1 atmosphere pressure), curve ab, de below the external air pressure, meaning that the pressure in the lungs is less than the outside air pressure, inhale; curve bcd is above the external air pressure, the lung pressure is greater than the external air pressure, exhale. Got it!
Circle 4 to judge the inhalation and exhalation according to the change in lung volume, this is quite simple, the increase in lung volume is inhale, and the decrease in lung volume is exhalation. The difficulty is that the variant of circle 4 is the same as the variant of circle 3, the difference is the text introduction on the left side of the coordinate system, one is the difference between the air pressure inside the lungs and the outside air pressure, and the other is the lung capacity. You should be able to understand that the variant abc of circle 4 indicates inspiration, why, the curve abc indicates an increase in lung volume; cde means exhalation, why?
There are also a few simpler knowledge points, which have been shared together, as shown in the figure.
I feel like it's almost over, so let's do the exercises.
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