The urinary tract and the nervous system have a complex relationship. The nervous system has several divisions, but the normal activity of the bladder is related to the autonomic and central nervous systems.
Here are some ways in which the nervous system influences the bladder.
How the bladder works
The bladder is basically responsible for the storage and the emptying of urine.
Normal voiding is dependent on the bladder contracting and the urinary sphincter relaxing. The voiding reflex originates in the brain and can be suppressed voluntarily under normal conditions until a critical bladder capacity is reached. During a contraction, the bladder muscle, known as the detrusor, contracts and the sphincter opens, allowing urination to occur.
The role of the spinal cord
The bladder emptying, or the contraction of the bladder, occurs as a result of the parasympathetic nervous system, which originates in nerves that arise in the sacral portion of the spinal cord (segments S2-S4) and then stimulates portions of the nervous system near the bladder wall. The sympathetic fibers that arise from the thoracic and lumbar spinal cord (T11-L3) contribute to the closure of the opening of the bladder, allowing the bladder to fill.
Severe injuries to the spinal cord can result in a lack of function of the bladder and an inability to empty. This condition is known as a neurogenic bladder. Unfortunately, once this occurs, function does not return. Patients who have this condition will usually rely on intermittent catheterization, which involves the placement of a small soft tube (a catheter) into the bladder to empty it several times daily.
Other neurologic conditions also exist that can affect the lower urinary tract and cause dysfunction, such as frequency or incontinence. Patients who demonstrate evidence of lower urinary tract dysfunction will commonly undergo testing known as urodynamics, which assess the degree of function of the lower urinary tract.
When the nerves are damaged, there can also be neuropathy, which makes it hard to feel when the bladder is full or completely empty. Conditions such as diabetes can lead to bladder neuropathy.
The condition of the kidneys is one additional concern that exists in patients who experience dysfunction of the lower urinary tract. Many of the entities that affect the lower urinary tract can result in elevated pressures being transmitted to the kidneys. Ultrasonography of the kidney can detect these changes.