Bladder Control DLA

Question 1

What are the levels. Of bladder control?

Answer 1

Levels of Bladder Control

Bladder function is controlled by the central nervous system at the supratentorial level, posterior fossa and the spinal cord.

The sympathetic efferents relax the detrusor muscle and constrict the internal sphincter muscle while the bladder fills. The parasympathetic efferents empty the bladder by constricting the detrusor muscle and relaxing the internal sphincter. Somatic efferents (lower motor neurons) control the striated external sphincter. Of the autonomic inputs to the bladder, the parasympathetic innervation is more clinically significant.

Question 2

What are the requirements of bladder filling?

Answer 2

Adrenergic receptors
→ Internal sphincter
contraction (α1)

→ Detrusor muscle
relaxation (β2)

Question 3

What are the somatic receptors of the bladder?

Answer 3

Nicotinic receptors
→ External sphincter
contraction

Question 4

What are the what are the parasympathetic receptors of the bladder?

Answer 4

Muscarinic receptors
→ Internal sphincter
relaxation (NO)

→ Detrusor muscle
contraction (M3)

Question 5

Explain filling and emptying 9f the urinary bladder

Answer 5

Pressure receptors innervate the bladder wall. Their cell bodies are located in the dorsal root ganglia, and their afferent fibers synapse on parasympathetic pre-ganglionic neurons. Postganglionic parasympathetic efferents then innervate the detrusor muscle and the internal sphincter muscle (both smooth muscle) of the bladder.

During the filling of the urinary bladder, the detrusor muscle remains relaxed and the internal sphincter muscle constricted under tonic sympathetic innervation.
Once the bladder is full, however, the sensory fibers innervating the bladder wall activate the parasympathetic preganglionic fibers, which initiate the micturition reflex. Sensory signals also ascend through the spinal cord to the pontine micturition center for facilitation of urinary discharge through activation of the parasympathetic and inhibition of the sympathetic innervation, with additional information reaching higher centers, contributing to urinary urges.

Discharge ultimately depends on parasympathetic system-mediated constriction of the detrusor muscle coupled with relaxation of the internal sphincter. The urinary system is also subject to complex higher circuitry, which permits voluntary control of urinary function through the somatic innervation of the external sphincter muscle (striated muscle innervated by alpha-motor neurons).

Question 6

What is an automatic bladder?

Answer 6

Automatic Bladder

If there is a lesion above the s2-s4 (say for example at T8) the patient will have a spastic bladder (automatic bladder). The patient will have reflexive emptying of the bladder once it fills and once there is threshold volume. There is no role for volition here

Question 7

What is an atomic bladder?

Answer 7

Atonic Bladder

With a lesion at S2-S4 (conus medullaris, which houses the origin of the parasympathetic fibers responsible for emptying the bladder), the spinal cord cannot process the incoming filling signals of the urinary bladder and would not be able to direct a reflex voiding response via the parasympathetic fibers.

So, here the bladder will just fill to the brim and the urine will overflow. This is atonic bladder also referred to as neuropathic bladder. So, in atonic bladder even the reflexive control is gone besides the voluntary control.