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4.2. Respiratory activity

Respiratory activity

The control of pulmonary ventilation is carried out by the nervous system (medulla oblongata) according to the oxygen needs of the organism.

If physical exercise is carried out, the concentration of CO2 in the blood increases, which is detected by the brainstem that causes the respiratory and heart rate to increase so that enough nutrients and oxygen reach the cells.

Respiratory movements

The pulmonary ventilation is the movement of the air from the outside of the body to the lungs through the airway.

In pulmonary ventilation, the lungs have a passive role, since it is the atmospheric pressure that causes the air to move.

The thoracic cage is hermetically closed, and air can only enter through the larynx. On inspiration, the rib cage increases in size causing less pressure than on the outside, and air enters the larynx. On expiration , the rib cage reduces in size, expelling air.

The rib cage is hermetically closed. If this box were to get bigger (its volume increased), a vacuum would be produced inside and the air would try to enter, but it is hermetically closed and there is only one place through which it can enter: through the larynx, And it does so, but the larynx It communicates with the lungs, which in this way swell like balloons. When the rib cage becomes small again, the air inside is expelled.

In this way, increasing and decreasing the size of the rib cage produces the movements of pulmonary ventilation.

Inspiración   Espiración

Es un movimiento activo, de contracción.

El diafragma desciende, y los músculos intercostales levantan las costillas.

Aumenta el volumen de la cavidad torácica.

El aire entra en los pulmones cargado de oxígeno.

Movimientos respiratorios de inspiración y espiraciónImagen-animada-Pulmones-04.gif (Imagen GIF, 176 × 200 píxeles) - Escalado (0 %). (s. f.). Recuperado a partir de

Es un movimiento pasivo, de relajación, aunque se considera activo porque intervienen algunos músculos.

Disminuye el volumen de la cavidad torácica.

El aire sale de los pulmones con más dióxido de carbono.




Activity: Breathing movements.

Test and video: The respiratory system.

TED-Ed: How do the lungs work?.

Answer in your notebook

4.8.- Is pulmonary ventilation the same as cellular respiration? Reason for the answer.

Breathing frequency

The respiratory rate is the number of breaths per minute, which is usually 12 to 16 strokes per minute in an adult at rest. The respiratory rate in children is higher, and in newborns it can reach up to 50 movements per minute.


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Biology and Geology teaching materials for Compulsory Secondary Education (ESO) and Baccalaureate students.