Urination

(redirected from micturition reflex)
Also found in: Dictionary, Thesaurus, Medical, Wikipedia.

urination

[‚yu̇r·ə′nā·shən]
(physiology)
The discharge of urine from the bladder. Also known as micturition.

Urination

 

(also called micturition), the reflex act of excreting urine from the body.

Uropoiesis—the production of urine—is a constant process, but urination occurs only intermittently, as the urinary bladder fills. Humans urinate four to six times daily. Urine is prevented from escaping from the bladder by two ring-shaped layers of muscle fibers: an internal sphincter, which consists of smooth muscle fibers, and an external one, which consists of striated fibers. When the pressure within the bladder reaches 2–2.66 kN/m2 (kilonewtons per square meter), or 15–20 mm Hg (millimeters of mercury), stimulation of the mechanoreceptors (the nerve endings of sensory neurons) in the wall of the bladder elicits the urge to urinate. In man, this critical pressure is achieved when 300–350 ml of urine accumulate in the bladder. During urination, the external sphincter relaxes reflexively as the muscles of the bladder wall contract.

Urination is regulated by the nerve centers in the spinal cord and brain; these centers are controlled, in turn, by the cerebral cortex. The filling of the urinary bladder arouses the cerebral cortex to elicit the urge to urinate. Certain neurological diseases, as well as injuries to the muscles of the urinary bladder, impair urination.

M. IA. RATNER

What does it mean when you dream about urination?

Urination in a dream has several interpretations that range from inhibited sexual desires to the outpouring of emotional feelings that have been repressed.

Urination

(dreams)
Releasing bodily wastes in a dream suggests a need to release repressed emotions and/or anxiety. At times, urination may have sexual connotations. Many people dream about the need to urinate, which wakes them up, and then they realize that they need to use the bathroom. At times, the dream triggers the physical sensation and other times the physical sensation may become a part of the dream.
References in periodicals archive ?
Autonomic dysfunction and plasticity in micturition reflexes in human a-synuclein mice.
As a result, bladder capacity and compliance are increased, and the initiation of the micturition reflex is delayed (Dray, 1988).
Drug effects on urinary bladder tone during spinal morphine-induced inhibition of the micturition reflex in unanesthetized animals.
Afferent pudendal nerve stimulation has been shown to inhibit the micturition reflex, abolish uninhibited detrusor contractions, and increase bladder capacity; said Dr.
The cause of the perception disturbance cannot be located in the periphery since the subjects experience the first desire to void and have an involuntary micturition reflex at a normal or even subnormal volume.
The beneficial effects of modulation of these pathways are: inhibition of spontaneous activity, increased bladder compliance (decreased bladder tone during filling), greater distension needed to activate the micturition reflex (increased bladder capacity), and decreased afferent activity, with no effect on voiding contraction (no risk for urinary retention).
Dopaminergic receptors in the brainstem are associated with stimulation of the micturition reflex under the influence of modulatory centers in the brain, and a genetic defect involving them may predispose the individual to detrusor overactivity and overactive bladder dysfunction (Eiberg, Shaumburg, von Gontard, & Rittig, 2001).
Neurogenic OAB seems to arise from either increased afferent input from the bladder, abnormal central processing of afferent input leading to reduced suprapontine inhibition or physical damage to the axonal paths integral to micturition reflex organized in spinal cord.