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Have you ever felt goosebumps on your skin, and you felt really cold? My grandma used tells me some untrue story while growing up. She would tell me that when I get goosenbumps, there were ghosts around where I was. I never believed her as a child because when I was unhappy, and felt betrayed by my mum, I usually get goosebumps and it wasn't as a result of seeing a ghost or having a ghost around. In this post, I will be sharing with you, what causes goosebumps which is completely different from what my grandmother told me.

When you skin raises up, bringing protrusions is what is refered to as Goosebumps. Some call it goose pimples, goose flesh, and other call it goose bumples but it has the word goose, and I could say that it got its name from its look which resembles the skin of a featherless goose. This could be the reason behind the name Goosebumps. Goosebumps occur in the skin, and the skin is made up of three layers, which are the Epidermis, the Dermis, and the Hypodermis. The epidermis is the paper thin top of the skin, while the thicker part of the skin is the dermis, the hypodermis is the subcutanous tissue below the dermis. The Epidermis and the Dermis are really important in Goosebump creation. Goosebumps are associated with the hair follicles in the skin. The hair follicle starts in the dermis of the skin, where hair grow out from, protruding upwards to the epidermis of the skin.

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**The Epidermis** The Epidermis, tiny but made up of several layers, with the top part being the Stratum Corneum which is uppermost part of the skin, which serves as a barrier between the outer world and the skin cells. Other layers of the epidermis are Stratum lucidum, Stratum granulosum, Stratum spinosum, Stratum basale. The Epidermis is made up of several cells (Keratinocytes, Melanocytes, Langerhans’ cells, and Merkel’s cell), somatic sensory nerves (which are responsible for pain, temperature, touch, and pressure)


**The Dermis**
This is the next layer after the epidermis, it is characterized by loose, ribbon like cells. It is made up of the upper layer which is loosely connected known as the papillary layer, and the thicker layer which is made up of collagen fibers known as the reticular layer. It houses the hair follicles, sensory neurons, blood vessles, muscles, sweat gland, and hairs.

**The Arrector Pili Muscle** With the hair follicle in the dermis of the skin, the arrector pili muscles are smooth muscles, and are tiny muscle that is attached to the base of the hair follicles at one end, at the dermal tiddue of the skin at another end. When the arrector pili muscle contracts, it pulls the base of the hair follicles, causing the hair to stand up straight, and when relaxed, allowing the hair to back to its bend state. In order to generate heat in the skin, the arrector pili muscle contracts, causing the hair to stand up straight.


When the hairs stand straight, they create goosebumps, and this is not controlled as it is controlled by a smooth muscle which acts involuntarily. This is activated by a physiological stress such as exposure to cold, or emotional stress such as fear, or anger. The involuntary activity is controlled by the brain.

The brain has a very large part to play in the movement of the Arrector pili muscles which control the hair follicles. The part of the brain responsible for this is the hypothalamus. The hypothalamus is found in the deep brain, involved in homeostasis (keeping the body stable by inducing hormones), and regulating the autonomic nerveous system known as the Sympathetic nervous system which is known as the flight or fight system. It is responsible for releasing noradrenaline or norepinephrine to the body.

The hypothalamus recieves chemical messages from the nerve cells, and create a sympathetic response which goes to the spinal cord, which then sends the information to different nerves and target in the body in which the skin is part of. When the norepinephrine or reaches the receptors of the Arrector Pili muscle, causing it to activate and the hair stand up. When the hair stands up right, it helps the skin to repels cold, producing heat for the skin. So many animals also experience somthing as similar to goosebumps, animals such as dogs, and porcupines. Also when mammals are angry or when there is fear, the hair rises up. This is more visible in animals with more fur making them look bigger. It is very visible when humans have strong emotions triggering the hypothalamus.

#### <center>Conclusion</center>
Compared to what my grandma used to say, it is visible that the hypothalamus of the brain is responsible for triggering the Arrector pili muscle, which is at the base of the hair follicles, making the skin hair to stand up right to prevent heat from leaving the body, which causes Goosebumps.


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**<center>Reference</center>**
* [National Institutes of Health - What goosebumps are for](https://www.nih.gov/news-events/nih-research-matters/what-goosebumps-are)
* [Healthline - Why Do We Get Goosebumps?](https://www.healthline.com/health/goosebumps-on-skin#how-they-develop)
* [Clevelandl Cinic  - Why Do You Get Goosebumps?](https://health.clevelandclinic.org/why-do-you-get-goosebumps/)
* [Harvard Health Publishing - Wondering about goosebumps? Of course you are](https://www.health.harvard.edu/blog/wondering-about-goosebumps-of-course-you-are-2020080320688)
* [Scientific American - Why do humans get "goosebumps" when they are cold, or under other circumstances?](https://www.scientificamerican.com/article/why-do-humans-get-goosebu/)
* [National Library of Medicine - Anatomy, Skin (Integument), Epidermis](https://www.ncbi.nlm.nih.gov/books/NBK470464/)
* [The Johns Hopkins University - Skin Anatomy](https://www.hopkinsmedicine.org/neurology_neurosurgery/centers_clinics/cutaneous_nerve_lab/patients/skin_anatomy.html)