Biological Curiosities

Why do we hiccup?

The hiccup is the result of an involuntary contraction of the diaphragm, a thin muscle that separates the thorax from the abdomen and which, together with the external intercostal muscles, is responsible for breathing control. Their contraction and relaxation movements allow us to breathe in and out and are controlled by the phrenic nerve just above the stomach.

Hiccup discomfort arises from a phrenic nerve irritation, the causes of which may be diverse (gastric distension by drinking carbonated beverages, swallowing air, or eating large volumes; sudden changes in the temperature of ingested foods; changes in body temperature , such as a sauna followed by a cold shower, drinking alcohol, or even laughing). When he is or sensitized, he sends a message to the diaphragm to contract, which triggers the hiccup.

The characteristic "hic, hic" noise occurs when there is sudden closure of the glottis (upper opening of the larynx, where the vocal cords are located), producing vibration in the vocal cords.

Can scare cure the hiccup? Why?

Yes you can. When we are startled, we cause a strong inhalation, leading to an increase in the volume of air in the lungs. The lungs put pressure on the diaphragm, causing it to stretch and function normally. But there are less drastic ways that also work: have a glass of water with a plugged nose or breathe in and hold the air for a moment.

How does the cough reflex happen?

The bronchi and trachea are so sensitive to light touch that minimal amounts of foreign material or irritating substances initiate the cough reflex. Afferent nerve impulses pass from the airway (mainly the vagus nerve) to the bulb (oblong medulla), where an automatic sequence of events is triggered by local neuronal circuits, causing the following effects:

- inspiration up to 2.5 liters of air;

- closure of the epiglottis and vocal cords to trap air within the lungs;

- strong contraction of the abdominal muscles and internal intercostal muscles, pushing the diaphragm and causing rapid pressure increase in the lungs (100 mmHg or more);

- sudden opening of the vocal cords and epiglottis and release of air from the lungs under high pressure.

In this way, air that is explosively expelled from the lungs outward moves so rapidly that it carries with it any foreign material present in the bronchi and trachea.

How does the sneeze reflex happen?

The sneeze reflex is very similar to the cough reflex, except that it applies to the nasal passages rather than the lower airways: the stimulus that initiates the sneeze reflex is irritation of the nasal passages. Afferent impulses pass from the fifth cranial nerve pair to the bulb, where the reflex is triggered. A series of reactions similar to those of the cough reflex happens, large amounts of air pass quickly through the nose, thus helping to clear the nasal passages.

Did you know that:

- Does the air coming out of the nostrils during the sneeze average 150 km / hour?

- as we sneeze, we spread about 40,000 drops of saliva?

Yeah, that's why sneezing is an excellent source of respiratory disease transmission.

Why is it impossible to sneeze with your eyes open?

Clarifying the myth: It's not because the eyes can come out of orbit that we close them by sneezing!

When a foreign particle enters the body via the nasal passages, it stimulates local receptors that, through the trigeminal nerve (which coordinates the movements of the face), warn the brain stem that it is time to take action.

Upon receiving the message, the brainstem reacts immediately to the invasion, generating a series of motor impulses that contract the abdomen, chest and diaphragm until it reaches the facial nerve.

Reflexes that reach the facial nerve also trigger movements to expel the foreign particle. These contractions reach various muscles of the face, including the orbicularis muscle, which controls the opening and closing of the eyes. As a result of all this effort, we close our eyes.