Pathophysiology of Micturition

Question 1

What are the 3 classes of neural lesions that lead to bladder dysfunction?

Answer 1

1. Combined afferent and efferent lesions.
2. Afferent lesions.
3. Spinal cord lesions.

Question 2

What happens when you sever both the afferent and efferent nerves of the bladder?

Answer 2

The bladder becomes distended and flaccid (hangs loosely).

Question 3

What does a decentralized bladder refer to?

Answer 3

A bladder that does not have afferent nor efferent innervation.

Question 4

What happens to decentralized bladders over time? Why is this bad?

Answer 4

1. Many small contractions (spastic) causes hypertrophy of the bladder.
2. This causes uncoordinated micturition (urination) events.

Question 5

What is the relationship between urine volume and a hypertrophied bladder?

Answer 5

There is a residual volume left over in the bladder after urination.

Question 6

What is the name of the nerve involved in a neural lesion that only affects the afferent fiber in bladder dysfunction?

Answer 6

Sacral dorsal root nerve fibers

Question 7

What happens when innervation from the sacral dorsal root nerve is lost in bladder dysfunction?

Answer 7

Reflex contractions, in response to activated stretch receptors, are lost.

Question 8

What are 3 anatomical characteristics of a lesion that only loses innervation of the sacral dorsal root nerve fibers?

Answer 8

1. Bladder becomes distended (bloated).
2. The bladder wall thins.
3. Bladder tone decreases.

Question 9

If you only cut the sacral dorsal root nerve fibers, will you still be able to get contractions of the bladder? How?

Answer 9

1. Yes

2. The intrinsic contractile response of smooth muscle in response to stretch.

Question 10

How is urination affected if you only cut the sacral dorsal root nerve fibers?

Answer 10

A residual urine volume remains after urination.

Question 11

What are the initial effects of a spinal cord transection?

Answer 11

1. Bladder becomes overfilled.

2. Sporadic voiding

Question 12

Define “sporadic voiding”.

Answer 12

Overflow incontinence (involuntary release of urine from a full bladder)

Question 13

What happens after the initial effects of spinal shock occur in bladder dysfunction? (4)

Answer 13

1. The voiding reflex is re-established
2. No voluntary control
3. Bladder capacity is reduced
4. Reflex hyperactivity that leads to a spastic neurogenic bladder (incomplete emptying of the bladder with residual volume)

Question 14

What is a consequence of residual urine in the bladder after urination?

Answer 14

Urinary tract infections, because the urine serves as an incubator for bacteria to grow.

Question 15

When are catheters usually placed in patient bladders? (2)

Answer 15

1. During periods of overflow incontinence

2. Before the voiding reflex is re-established

Question 16

What is a consequence of catherization?

Answer 16

Urinary tract infections