Pontine micturition center
Encyclopedia
The Pontine micturition center (PMC, also known as Barrington's Nucleus) is a collection of cell bodies located in the rostral pons
in the brainstem that is involved in the supraspinal regulation of micturition (urination). The PMC makes connections with other brain centers to control micturition, including the hypothalamus
, the cerebral cortex
and periaqueductal gray
(PAG). The PAG in particular acts a relay station for ascending and descending bladder information from the spinal cord.
and to the parasympathetic nucleus in the spinal cord
while receiving ascending input from the level of the sacral and lumbar cord. During bladder filling, neurons within the PMC are turned off, but at a critical level of bladder distention, the afferent activity arising from mechanoreceptors in the bladder wall switches the PMC on and enhances its activity. This activation results in relaxation of the urethra
and contraction of the bladder
due to concomitant stimulation of parasympathetic and inhibition of sympathetic outflow to the bladder, as well as removal of somatic activation of the external urethral sphincter. This pattern of activity can also be elicited through the conscious desire to void.
Pons
The pons is a structure located on the brain stem, named after the Latin word for "bridge" or the 16th-century Italian anatomist and surgeon Costanzo Varolio . It is superior to the medulla oblongata, inferior to the midbrain, and ventral to the cerebellum. In humans and other bipeds this means it...
in the brainstem that is involved in the supraspinal regulation of micturition (urination). The PMC makes connections with other brain centers to control micturition, including the hypothalamus
Hypothalamus
The Hypothalamus is a portion of the brain that contains a number of small nuclei with a variety of functions...
, the cerebral cortex
Cerebral cortex
The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It is constituted of up to six horizontal layers, each of which has a different...
and periaqueductal gray
Periaqueductal gray
Periaqueductal gray is the gray matter located around the cerebral aqueduct within the tegmentum of the midbrain. It plays a role in the descending modulation of pain and in defensive behaviour...
(PAG). The PAG in particular acts a relay station for ascending and descending bladder information from the spinal cord.
Regulation
In humans, neurons in the PMC send descending projections to Onuf's nucleusOnuf's nucleus
Onuf’s nucleus is a distinct group of neurons located in the ventral part 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 contraction during orgasm. It contains motor neurons, and is the...
and to the parasympathetic nucleus in the spinal cord
Spinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...
while receiving ascending input from the level of the sacral and lumbar cord. During bladder filling, neurons within the PMC are turned off, but at a critical level of bladder distention, the afferent activity arising from mechanoreceptors in the bladder wall switches the PMC on and enhances its activity. This activation results in relaxation of the urethra
Urethra
In anatomy, the urethra is a tube that connects the urinary bladder to the genitals for the removal of fluids out of the body. In males, the urethra travels through the penis, and carries semen as well as urine...
and contraction of the bladder
Bladder
Bladder usually refers to an anatomical hollow organBladder may also refer to:-Biology:* Urinary bladder in humans** Urinary bladder ** Bladder control; see Urinary incontinence** Artificial urinary bladder, in humans...
due to concomitant stimulation of parasympathetic and inhibition of sympathetic outflow to the bladder, as well as removal of somatic activation of the external urethral sphincter. This pattern of activity can also be elicited through the conscious desire to void.