what is one major function of arrector pili muscle contraction
Arrector pili muscle Contraction of the muscles has a number of different purposes. Its principal function in the majority of mammals is to provide insulation: air becomes trapped between the erect hairs, helping the animal retain heat. Erection of the porcupine's long, thick hairs causes the animal to become more intimidating, scaring predators. Pressure exerted by the muscle may cause sebum to be forced along the hair follicle towards the surface, protecting the hair.
Anatomical terms of muscle Another example is the dumbbell curl at the elbow. The "elbow flexor" group is the agonist, shortening during the lifting phase (elbow flexion). During the lowering phase the "elbow flexor" muscles lengthen, remaining the agonists because they are controlling the load and the movement (elbow extension). For both the lifting and lowering phase, the "elbow extensor" muscles are the antagonists (see below). They lengthen during the dumbbell lifting phase and shorten during the dumbbell lowering phase. Here it is important to understand that it is common practice to give a name to a muscle group (e.g. elbow flexors) based on the joint action they produce during a shortening (concentric) contraction. However, this naming convention does not mean they are only agonists during shortening. This term typically describes the function of skeletal muscles.[5]