The Pontine micturition center (PMC, also known as Barrington's nucleus) is a collection of neuronal cell bodies located in the

rostral Rostral may refer to: Anatomy * Rostral (anatomical term), situated toward the oral or nasal region * Rostral bone, in ceratopsian dinosaurs * Rostral organ, of certain fish * Rostral scale, in snakes and scaled reptiles Other uses * Rostral colu ...

pons in the

brainstem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is cont ...

involved in the supraspinal regulation of

micturition Urination, also known as micturition, is the release of urine from the urinary bladder through the urethra to the outside of the body. It is the urinary system's form of excretion. It is also known medically as micturition, voiding, uresis, ...

. When activated, the PMC relaxes the urethral sphincter allowing for micturition to occur. The PMC coordinates with other brain centers, including the medial

frontal cortex The frontal lobe is the largest of the four major lobes of the brain in mammals, and is located at the front of each cerebral hemisphere (in front of the parietal lobe and the temporal lobe). It is parted from the parietal lobe by a groove betwe ...

, insular cortex,

hypothalamus The hypothalamus () is a part of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrine system via the pituitary gland. The hypothalamu ...

and periaqueductal gray (PAG). The PAG acts as a relay station for ascending bladder information from the spinal cord and incoming signals from higher brain areas.

Regulation

In humans and other mammals, neurons in the PMC send descending excitatory projections to spinally located

parasympathetic The parasympathetic nervous system (PSNS) is one of the three divisions of the autonomic nervous system, the others being the sympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of t ...

neurons controlling the detrusor muscle of the bladder and inhibitory interneurons regulating

Onuf's nucleus Onuf's nucleus is a distinct group of neurons located in the ventral part ( laminae IX) of the anterior horn of the sacral region of the human spinal cord involved in the maintenance of micturition and defecatory continence, as well as muscular c ...

. Additionally, the PMC receives ascending input from the level of the lumbosacral spinal cord. During bladder filling, neurons within the PMC are turned off. However, at a critical level of bladder distention the afferent information arising from

mechanoreceptors A mechanoreceptor, also called mechanoceptor, is a sensory receptor that responds to mechanical pressure or distortion. Mechanoreceptors are innervated by sensory neurons that convert mechanical pressure into electrical signals that, in animals, a ...

in the detrusor switches the PMC on and enhances its activity. This activation results in relaxation of the

male Male (symbol: ♂) is the sex of an organism that produces the gamete (sex cell) known as sperm, which fuses with the larger female gamete, or ovum, in the process of fertilization. A male organism cannot reproduce sexually without access to ...

or female external urethral sphincter and contraction of the

bladder The urinary bladder, or simply bladder, is a hollow organ in humans and other vertebrates that stores urine from the kidneys before disposal by urination. In humans the bladder is a distensible organ that sits on the pelvic floor. Urine enters ...

. While operating as a spino bulbospinal reflex arc, this pattern of activity is also elicited through the conscious desire to urinate.

References

*Fowler CJ, Griffiths D, de Groat WC. (June 9, 2008) "The neural control of micturition." ''Nature Reviews Neuroscience'' (6):453-66 *Kuipers R, Mouton LJ, Holstege G. (January 1, 2006) "Afferent projections to the pontine micturition center in the cat." ''The Journal of Comparative Neurology'' 494(1):36-53 *Sasaki M. (December 5, 2005) "Role of Barrington's nucleus in micturition". ''The Journal of Comparative Neurology'' 5;493(1):21-6 Pons Reflexes {{neuroanatomy-stub