Cold stimulates a few responses of which hair erection is one. This is considered by most to be a legacy response from when body hair was thicker and thus a better insulator when the hairs stand up. When the environment is warm a person might still be stimulated by fear, shock, or surprise. Anything that gives you goosebumps is stimulating each affected hair's erector pili muscle to contract.
erector pilae
If you are referencing to goosebumps those are actually little muscles that attach to your hair follicle that make it stand up. This process is in response to fear or coldness. In animals their hair stands up to thwart away predators. In humans, it doesn't do that but its the same muscle that pulls the follicle up.
There is not a single muscle that rotates the upper arm. The name of the muscle that contributes in rotation of the upper arm is deltoid muscle.
A strain, or pulled muscle, is an injury in which a muscle or its attaching tendons are torn due to overstretching. It is often associated with fatigue, muscle overuse and improper movement.
Makes the hair follicle stand upright
i assumed you are referring to the arrector pili muscle. usually when you are cold or scared, this muscle contracts, pulling the hair follicle in a upright position. the dents created are called goosebumps. it provides insulation and protects the hair
It causes erection of hair when stimulated by the sympathetic nervous system.
a muscle
The erector spinae
erector pili
erector spinae
Erector Spinae
This is a Muscle in our dermis which i know nothing else about so dont ask me
Erector Spinae
Erector Spinae
erector pili