Bladder Function and Micturition (B2: W5) Flashcards Preview

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Flashcards in Bladder Function and Micturition (B2: W5) Deck (35)
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1
Q

What is the function of the renal pelvis?

A

Renal pelvis is like a funnel that collects urine from the kidney and sends it to the ureter

The renal pelvis is the location of several kinds of kidney cancer

2
Q

How is urine moved into and along the ureter?

A

Pyeloureteric peristalsis moves urine into the ureter

  • Initiated by pacemaker cells that drive rhythmic electrical and mechanical events from the renal pelvis to the ureter
  • Dominant pacemaker is at the pelvi-calyceal border
  • Force of contractions is influenced by the rate of urine flow
3
Q

What is a kidney stone?

A
  • Like a small rock that forms in the kidney
    • Forms when certain chemicals precipiate
    • Can remain in kidney or travel through urinary tract
4
Q

What are the main sites where kidney stones get stuck?

A
  • At the ureteric junction of renal pelvis
  • As the ureter passes over the iliac vessels
  • At the junction of the ureter and the bladder - vesicoureteric junction
5
Q

What is hydronephrosis and what are the negative effects?

A

Distension and dilation of the renal pelvis and calyces

  • Blocking urine flow increases pressure in the kidney, and can lead to hydronephrosis
  • Causes progressive atrophy of the kidney if left untreated
6
Q

What are the 4 main types of kidney stones?

A
  1. Calcium-oxalate: eating too much Ca or vitamin D, some medications, genetics, other kidney problems
    1. Most common
  2. Struvite: having kidny infections
    1. Women more than men
    2. More harmful to kidneys
  3. Uric acid: eating too much animal protein, genetics
  4. Cystine: Cystinuria - a genetic kidney disease
    1. Very rare
7
Q

Describe the excitation-contraction coupling of cells in the ureter that cause peristalsis

A

Pacemaker cells in the most proximal part of the renal pelvis:

  • Produce an electrical event - like a depolarization
    • Causes activation of calcium channels
  • Each event is coupled to a contractile event
8
Q

What is special about the bladder in regards to filling?

A
  • If you put a quart of water into the bladder, it expands to receive the volume
  • The c_ompliance increases_ as it fills with fluid
  • Through most of the filling of the bladder, there is no increase in pressure
    • When pressure does go up, signal to brain tells you to void
9
Q

What is released by the urothelium in response to bladder filling?

A

ATP

  • ATP finds receptors on sensory neurons within suburothelial tissue
    • ATP opens ion channels in these neurons
    • Action potentials in central neurons
  • Develops a signal that comes from efferent neurons and into the target organ
    • Release ACh and ATP to produce contraction and micturition
10
Q

Describe the neural process involved in the filling phase

A
  • Urine comes into bladder from ureter
  • Slight increase in pressure - relaxation caused by hypogastric nerve
  • Release NE in the sphincter causing it to contract
  • Pudendal nerve innervates skeletal mucle of external sphincter and keeps it contracted
  • Sensory neurons through pelvic nerve go to spinal cord gaglia and bring information about the state of things in the bladder
    • Send info to sympathetic side to cause relaxation
    • Send info to CNS
11
Q

Which nerve causes relaxation in the bladder in repsonse to an increase in pressure?

A

Hypogastric nerve

  • Inhibits detrusor
12
Q

Which nerve is responsible for skeletal muscle of external uretheral sphincter?

A

Pudendal nerve

  • Conscious control from CNS helps keep sphincter closed
13
Q

What causes contraction of the internal urethral sphincter, which is involuntary?

A

Norepinephrine

14
Q

Describe the neural process involved in micturition

A
  • Pelvic nerve senses that bladder is full
    • At some point, pressure beings to rise
    • Pelvic nerve goes to higher centers and initiates a signal down the spinal cord to the pudendal nerve to turn off
  • Excitatory signal through pelvic nerve causes contraction of the detrusor
  • NO increases and causes internal sphincter to relax
15
Q

What causes relaxation of the internal uretheral sphincter?

A

Nitric Oxide

16
Q

Which nerve senses that bladder is full?

A

Pelvic nerve

17
Q

What causes contraction of the detrusor muscle of the bladder?

A

Excitatory signal through pelvic nerve

18
Q

What happens when latent pacemakers are excited by noxious or irritant stimuli?

A

Can produce an antiperistaltic wave of contraction producing urine reflux toward the kidney

19
Q

Where does the pudendal nerve come from?

A

Somatic nerve (skeletal muscle motor neuron)

From Sacral segments S2-S4

20
Q

Where does the hypogastric nerve come from?

A

Sympathetic

From T10-L2 inferior mesenteric ganglion

21
Q

Where does the pelvic nerve come from?

A

Parasympathetic

S2-S4 through pelvic ganglion

22
Q

What efferent pathways are involved in urine storage?

A
  • External sphincter contraction (pudendal)
  • Internal sphincter contraction (hypogastric nerve) - NE
  • Detrusor inhibition (hypogastric nerve)
23
Q

What efferent pathways are involved in micturition?

A
  • Inhibiton of external sphincter activity (pudendal nerve, CNS control)
  • Inihibition of sympathetic outflow (inhibiting hypogastric)
  • Activation of parasympathetic outflow (pelvic nerve)
    • To bladder
    • To urethera
24
Q

What happens when urothelium is exposed to noxious side effects (chemical irritants, pH, mechanical trauma, thermal)?

A
  • Substances other than ATP are released from the urothelium
    • NO
    • Prostaglandins
    • Nerve growth factor (can cause remodeling)
    • Acetyl choline
    • Substance P
  • These things activate other receptors present on sensory neurons
    • TRPV1 and trkA
    • Can cause hypoalgesia - receptor changes phenotype and becomes more active
  • A lot of receptors present in urothelium produce other effects
    • Change the amount of things being released
    • Can affect sensation - A∆ and C fibers → noxious sensations
25
Q

What are the neurotransmitters and receptors involved in filling and micturition?

A
26
Q

What is the mechanism for contraction of the detrusor muscle when stimulated by pelvic nerve?

A
  1. Entry of calcium
  2. Release of Ca from cellular stores
  3. Sensitization of contractile apparatus by inhibiting myosin light chain phosphatase (MLCP)
27
Q

What initiates bladder contraction?

A

The bladder does not begin to contract until a certain intravesical pressure is reached to initiate urination (neurogenic)

  • Up to about 500 mL, there is no increase in pressure
  • When it rises above, it is at the sensory threshold
28
Q

What is urinary incontinence?

A

Unplanned release of urine, often leakage between urinary contractions

29
Q

What is stress urinary incontinence (SUI)?

A

Leaks occur during laughing, coughing, sneezing… increased abdominal pressure

  • Most common bladder control problem in younger women
30
Q

What is urge incontinence (HSIHP)

A

Frequent feelings of desperate need to urinate

  • Could be enhancement in motor activity, causing premature contractions
  • Spasms of the detrusor muscle occur as a result of nerve or muscle damage
31
Q

What is overactive bladder (OAB)?

A

Similar to urge incontinence, but many people do not have leakage problems, just interruption of activities

32
Q

What is neurogenic bladder?

A

A problem in whcih a person lacks bladder control due to a brain, spinal cord, or nerve condition

  • Due to sensory or efferent problems
  • Different combinations of neurological disorders can promote this
  • Related to either overactive bladder or underactive bladder
33
Q

What happens in the case of decreased bladder compliance?

A
  • As volume increases, pressure increases
    • Walls don’t become more compliant
  • IF the sensory urge to empty bladder comes early, there is frequency of an urge to void
  • Examples
    • Prostate problems
    • Interstitial cystitis - chronic inflammation of the urothelium
    • Radiation
34
Q

What happens in the case of uninhibited (overactive) bladder?

A

Nonvoiding contractions occur during filling

  • Detrusor overactivity
35
Q

Compare cystometrograms showing normal and abnormal micturition cycle in non obstructed bladder

A

Voiding contractions (top) correspond to urine volume (bottom)

A) Normal

B) Abnormal

Increase in frequency of voiding contractions

Tone can be elevated during filling - start to get leakage