Micturition Flashcards Preview

JR - Renal > Micturition > Flashcards

Flashcards in Micturition Deck (24)
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1
Q

What is micturition?

A

The process by which the urinary bladder empties when it becomes filled.

2
Q

What transports urine from the kidneys to the bladder and how long is this?

A

The ureters.

25-35 cm long

3
Q

Where does the ureter enter into the bladder wall?

A

It enters through the bladder wall through the detrusor muscle at the trigone.

4
Q

What pushes the urine through the ureters? When enhances this action?

A

Smooth muscle contractions propel urine to the bladder.

Enhanced by parasympathetics and inhibited by sympathetic stimulation.

5
Q

Where are the possible constrictions where kidney stones or other things can clog the ureters?

A

1) Ureteropelvic junction at ureter and bladder.
2) Behind testicular or ovarian a or v.
3) Pelvic brim (over external iliac a and v)
4) Where the ureter traverses the bladder wall

6
Q

What is the vesicoureteral reflux?

What does it increase the risk of?

A

Urine goes back into ureter during micturition.

Pyelonephritis

7
Q

What does the detrusor muscle do?

A

Smooth muscle of the bladder > contracts in micturition

8
Q

What does the trigone do?

A

Mucosa on posterior wall of bladder above the bladder neck. Where ureters enter bladder and where the bladder neck opens into the posterior urethra.

9
Q

What does the internal sphincter do?

A

Smooth muscle located in bladder neck > holds in urine when contracted (involuntary)

10
Q

What does the external sphincter do?

A

Skeletal muscle located in urogenital diaphragm > holds in urine when contracted (voluntary)

11
Q

What part of the spinal cord innervates the bladder?

A

S2-S4

12
Q

What type of fibers detect bladder FULLNESS?

A

A(delta) fibers (myelinated) > wall tension (fullness)

13
Q

What type of fibers detect bladder PAIN?

A

C fibers (unmyelinated) are “silent” and respond to noxious stimuli (chemical irritation and cooling)

14
Q

What system is responsible for bladder emptying? Via what nerve? Via what neurotransmitter and receptor?

A

The parasympathetics.
Pelvic splanchnic nerve
ACh
Muscarinic (M3)

15
Q

What systems work to stop micturition?

A

Sympathetics and somatic muscle innervation

16
Q

What does the pontine micturition center (PMC) do?

A

Controls and coordinates activity of sacral micturition center
Activates external urethral relaxation and sacral parasympathetic outflow > micturition

17
Q

What does the Periaqueductal gray (PAG) do?

A

Receives afferent bladder signals and passes on to higher brain centers > conscious sensation.
Primary excitatory input to the PMC

18
Q

What can overturn the PAG?

A

The higher brain center (cortex)

Prevent incontinence

19
Q

What happens if afferent or efferent fibers between bladder and cord are destroyed?

A

No detrusor contractions.

Urinary retention > overflow incontinence

20
Q

If there is spinal cord damage above the sacrum what happens?

A

Destrusor does not work, urinary retention occurs.
Eventually micturition reflexes return, detrusor is overactive and sphincter dyssynergia presents.
Periodic incomplete urination.

21
Q

What if there is damage above the pons? (from stroke, tumor, or brain trauma)

A

Interrupts all inhibitory signals from the brain > continuous stimulation of micturition center > overactive detrusor
Result: frequent, unpredictable urination (complete)

22
Q

Describe urination in an infant.

A

There is involuntary start/stop.

Though detrusor and sphincter still work in coordination.

23
Q

Describe urination in an adult.

A

Voluntary start/stop

Detrusor and sphincter work in coordination.

24
Q

Describe urination in a paraplegic patient (spinal cord damage above sacrum).

A

Void occurs at lower bladder volumes.
Involuntary start/stop
Detrusor and sphincter are uncoordinated (dyssynergia)