The Pilomotor Reflex

We forgot about another cluster of defensive aggression, also closely correlated with the composite profile of noradrenergic activity, and also demonstrating in its functional profile a JOINT INCREASE in the Ne, Qe, and Fe functions (and also with a simultaneous strong decrease in Ti).

This is the individual expression of the pilomotor reflex in humans.

Recall that the pilomotor reflex is when the hairs on the skin rise (and sometimes even the hair on the head quite literally stands on end). The human pilomotor reflex is a vestige of the ruffling of our ancestors’ fur, which occurred when an individual encountered an opponent superior to it in strength and size. Fleeing is impossible, fighting is pointless, what remains is - to frighten. To assume a threatening posture, bare the teeth, hiss, ruffle the fur, and arch the back upward (in order to appear visually larger in the opponent’s eyes – cats still use this entire behavioral complex in full to this day) – this is the origin of the modern pilomotor reflex in the form of hairs standing up from a sudden fright or another emotional influence.

However, it is also triggered by cold, causing the muscles of the skin hairs to contract. As a result, the volume of our ancestors’ fur coat became greater, thereby warming them against the cold wind. If this does not help, the next stage of warming the subcutaneous capillaries is shivering, which through its shaking forces the superficial striated muscles to work intensively, transferring heat to the surrounding tissues.

Recall here, just in case, that individuals with elevated noradrenergic activity are again more sensitive to cold, because under the action of noradrenaline their subcutaneous capillaries are constricted and carry little heat to the surface of the body.

But, nevertheless, the most original function of the pilomotor reflex is still to frighten an opponent by ruffling one’s fur (poor Homo sapiens: the reflex has been preserved, but not much fur remains to be ruffled).

Wikipedia also reports:

“Pilomotor reflex (the “goosebumps” effect) is characteristic not only of humans, but also of many other mammals. In response to cold, raised hairs help the layer of air warmed by the body remain at the surface of the skin. In response to danger, raised fur makes animals appear more massive and gives them an intimidating appearance. Such a response is often observed in chimpanzees, in frightened or irritated mice, cats, and dogs. The porcupine is known precisely for the manifestation of the pilomotor reflex, as a result of which the quills (modified hairs) on its back rise when danger arises.

In humans, the «goosebumps» effect can often be caused not only by cold or fear, but also by other strong emotions caused, for example, by beautiful music, or, conversely, by the scraping of chalk on a blackboard or metal on glass, by a feeling of satisfaction or pleasure from something, or by sexual arousal. Piloerection in humans is a vestigial reflex — because of the limited hair covering, it has lost its practical significance for humans.”

LIST OF QUESTIONS ON THE EXPRESSION OF THE PILOMOTOR REFLEX:

1. Sometimes (at least once a week) the hairs on my body tense up and stand “upright,” “on end.”
2. If my skin is touched lightly from the outside, especially on the neck, “goosebumps” immediately appear on it, and the hairs tense up and stand on end.
3. Quite often the skin on my body tenses and becomes bumpy, and the hairs on it stand on end.
4. Sometimes I feel the hair on my head lifting (standing “on end”).
5. It often happens to me that while listening to music, pleasant shivers run through my body (with slight “goosebumps,” when the skin hairs tense up, briefly rising as little bumps)
6. Sometimes I have felt the skin on my head tense and the hair on it seem to stand “on end.”

Comparison of the cluster of heightened pilomotor reflex (fur-ruffling reflex) with the mean profile of noradrenergic activity obtained by averaging over its other 22 marker clusters

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Another fact is curious. The very life of the hair follicle is maintained with the help of the small smooth muscles responsible for the “standing up” of a skin hair. Stem cells form at the place where the muscles attach to the hair bulb. They are necessary for renewal of the follicle itself and for hair growth. As soon as goosebumps begin to run over the body, nerves transmit an excitation signal to the muscles, and then an interesting thing happens to the stem cells — they turn into hair follicles and give rise to hair growth. Thus, the more goosebumps we experience, the better the quality of the hair germs beneath the skin, and the more often and more quickly new hairs sprout from it. Therefore, if you keep your head in the cold (as many dermatologists-trichologists advise), then balding will occur at least more slowly than in others. And if you keep your arms and legs in the cold, beautiful fluffy growth will appear on them as well. Incidentally, it makes no difference what causes frequent shivers with goosebumps. If they are caused by fear or by pleasant music, the hair will also grow faster. That’s how it is. And this is true! 😊

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And here is another very recent scientific study on the subject of “goosebumps”:

Harvard University, “Mail.RU News” reports, investigated the phenomenon of goosebumps. Experiments with rodents helped shed light on this question. It turned out that “goosebumps” are a side effect of the operation of a closed system aimed at regulating hair growth.

“It is known that nerve endings on the surface of the skin are part of the sympathetic nervous system, which controls the body’s responses to external stimuli. They are connected to fibers of smooth muscle tissue located beneath the skin, which are connected to the stem cells of hair follicles. In response to cold, sympathetic neurons send nerve signals to the subcutaneous muscles, which contract, causing goosebumps to appear on the skin and the hairs to stand on end.

At the same time, activation of the stem cells of the hair follicles occurs in parallel, which stimulates the growth of hair on the body. According to the scientists, “goosebumps” are evidence of a connection between sympathetic neurons and hair follicles through contracting muscle tissue.

Thus, if exposure to cold is brief, the stem cells receive a one-time command from the neurons, causing them to enter a state of readiness for regeneration. With a prolonged decrease in temperature, the stem cells initiate a program for increasing hair growth on the body.”

More details about this study:

1. news.harvard.edu/gazette/st…
2. www.cell.com/cell/pdf/S…

What is important in this study? That it has finally been convincingly shown that it is specifically noradrenergic innervation (sympathetic nerves of the autonomic nervous system, with noradrenaline released at the end of the axon) that initiates both the process of contraction of the hair muscles (the consequence of which is the hairs standing on end) and, at the same time, stimulates hair growth, turning undifferentiated stem cells into hair follicles.