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Each arrector pili is composed of a bundle of smooth muscle fibres which attach to several follicles (a follicular unit). [4] Each is innervated by the sympathetic division of the autonomic nervous system. [4]
The neurotransmitters of postganglionic fibers differ: In the parasympathetic division, neurons are cholinergic. That is to say acetylcholine is the primary neurotransmitter responsible for the communication between neurons on the parasympathetic pathway.
There are two kinds of neurons involved in the transmission of any signal through the sympathetic system: pre-ganglionic and post-ganglionic. The shorter preganglionic neurons originate in the thoracolumbar division of the spinal cord specifically at T1 to L2~L3, and travel to a ganglion, often one of the paravertebral ganglia, where they synapse with a postganglionic neuron.
The reflex of producing goose bumps is known as piloerection or the pilomotor reflex, or, more traditionally, [6] horripilation. It occurs in many mammals ; a prominent example is porcupines , [ 7 ] which raise their quills when threatened, or sea otters when they encounter sharks or other predators.
Chromaffin cells contained in the adrenal medulla act as postganglionic nerve fibers that release this chemical response into the blood as a circulating messenger. The sympathoadrenal system can activate and discharge chemical messengers as a single unit to activate an organism's “fight or flight” response.
Group C fibers include postganglionic fibers in the autonomic nervous system (ANS), and nerve fibers at the dorsal roots (IV fiber). These fibers carry sensory information. Damage or injury to nerve fibers causes neuropathic pain. Capsaicin activates C fibre vanilloid receptors, giving chili peppers a hot sensation.
The development of the nervous system in humans, or neural development, or neurodevelopment involves the studies of embryology, developmental biology, and neuroscience.These describe the cellular and molecular mechanisms by which the complex nervous system forms in humans, develops during prenatal development, and continues to develop postnatally.
This receptor is found mediating slow EPSP at the ganglion in the postganglionic nerve, [6] is common in exocrine glands and in the CNS. [7] [8] It is predominantly found bound to G proteins of class G q [9] [10] that use upregulation of phospholipase C and, therefore, inositol trisphosphate and intracellular calcium as a signalling pathway.