Micturition Neurology

CNN X (vagus n.)

Where do preganglionic cell bodies originate?

Vagus n.

Which nerve carries preganglionic fibers to the thoracic and abdominal viscera?

Pelvic n.

Carries sacral preganglionic fibers

Caudal mesenteric ganglion, bladder wall and sphincter

Sympathetic innervation of urinary bladder:

Preganglionic from the spinal cord → synapses in the ___ (collateral ganglion)

Postganglionic to the ___

Contract sphincter (alpha1), relax detrusor (beta3) (storage)

S1-3, pelvic n., pelvic plexus, bladder wall

Parasympathetic innervation of urinary bladder:

1. Preganglionic from ___ (dog and cat) → emerges as the ___ → synapse in the ___

2. Postganglionic to the ___

3. Contract detrusor (M3) (micturition)

Stretch receptors

As the bladder fills, ___ in the wall detect a change. When distended, these [same term] fire.

Pelvic n., micturition center

1. Sensory information from the bladder is sent via the ___ to the spinal cord.

2. Sensory information travels through the spinal cord to the ___ in the brainstem (pontine reticular formation).

Parasympathetic neurons, S1-S3, pelvic n., pelvic plexus, detrusor m.

During micturition:

1. Signal sent back down the spinal cord to the preganglionic ___

2. PS preganglionic cell bodies in ___

3. They send efferent signals via the ___ and synapse on the postganglionic PS neuron in the ___

4. Postganglionic PS neurons synapse on ___ = contraction (M3) = detrusor reflex

Spinothalamic tract, aware

1. Bladder signals also project to the thalamus via the ___

2. Signals reach the cortex = animal ___ of bladder distension

Conscious control of micturition

1. Territorial marking (activation)

2. House training (inhibition)

3. = cerebral cortex (cerebrum)-related functions

L1-L4/5, caudal mesenteric ganglion, hypogastric n., detrusor m., sphincter m.

1. Storage

   1. Sympathetic preganglionic fibers originate in ___

   2. Synapse on ___

   3. Postganglionic sympathetic fibers in the ___ and synapse with:

      1. ___ = relaxation of smooth muscle (beta3)

      2. ___ = contraction of smooth muscle (alpha1)

         1. Urine accumulates in the bladder

Urethral sphincter mm., pudendal n., contraction

1. Maintaining storage of urine (somatic)

   1. If urine leaks from the bladder to the urethra, stretch receptors in the ___

   2. Signal ascends in the ___

   3. Activation of motor neurons in the sacral region

   4. Motor info sent back to the muscle via the [same term as previous blank]

   5. ___ around the neck of the urethra (=urethral [same term as previous blank] during leaking)

   6. Signal to the brainstem and cortex = awareness and conscious contraction of the urethral muscle

Mechanoreceptors, visceral afferent, brainstem, parasympathetic

1. Micturition/urination mechanisms

   1. Bladder passively fills

   2. As detrusor m. begins to stretch, ___ (stretch receptors) in wall detect change in bladder pressure as bladder fills

   3. ___ neurons in the pelvic n. relay this information to the spinal cord (sacral cord) and either:

      1. Ascend to the ___ for central coordination of bladder function, or

      2. Synapse in the spinal cord on ___ preganglionic cell bodies and turn on [same term as previous blank]

Detrusor contraction, sympathetic fibers, external sphincter, detrusor m.

1. Parasympathetic component

   1. When the bladder reaches a threshold of distension, descending fibers from the brain:

      1. Activation of parasympathetic fibers causes ___ (M3)

      2. Descending fibers also inhibit ___ and inhibit somatic input to the ___

      3. Effects: Constrict the ___ to allow micturition to occur

Upper lumbar segments, detrusor relaxation, internal sphincter contraction

1. Sympathetic component

   1. Descending fibers from the brain:

      1. Synapse on sympathetic preganglionic neurons in the ___ of the spinal cord

   2. Sympathetic postganglionic fibers:

      1. Cause beta-mediated ___ (B3) and

      2. Alpha-mediated ___ (A1)

      3. Effects: decreased pressure on the bladder wall; urine is retained in the bladder

Urinary incontinence

Leaking of urine and inability to urinate

Includes signs of inappropriate urination and failure to urinate

Sacral spinal cord, pudendal n., pelvic n.

LMN bladder:

1. Lesion to the ___, ___, and/or ___

Parasympathetic, external sphincter

LMN bladder:

1. Loss of neurons to the bladder

   1. Loss of ___ function (detrusor muscle contraction), reduced bladder wall tone

   2. Loss of ___ tone (in general, LMN contracts the sphincter m.)

Overdistension of the bladder

LMN bladder:

The bladder is full, and there is overflow incontinence, but urination is not sustained as detrusor m. contraction is lost

Lumbar spinal cord, urethral sphincter, parasympathetic

1. UMN bladder

   1. Damage to the cranial ___

      1. Loss of inhibition of the somatic outflow (in general, UMN inhibits LMN function)

         1. The ___ (striated m.) is in sustained contraction (LMN contracts the muscle that is located in the neck of the urethra)

      2. The ___ innervation to the detrusor m. is intact (the damage of UMN does not affect the [same term as previous blank] n. function)

         1. The animal will have a full, turgid bladder

Unaware, sympathetic, contraction

1. UMN bladder:

1. Difficulty of expression

   1. A lesion may block input to the brain, leaving the animal ___ of bladder distension

   2. Sustained ___ outflow facilitates ___ of the smooth muscle in the bladder neck and compounds urine retention

      1. In general, the bladder distension signal goes to the brain, which stops the sympathetic function and activates parasympathetic function.