Micturition Flashcards
Upper urinary tract
-components?
Calyces, pelvis, ureters
Bladder
-Function?
- Stores urine under low pressure
- Expels urine under high pressure
Urethra
- What is it?
- Function?
- A conduit for carrying urine from the body
- Its two sphincters control voiding
Urinary bladder and sphincters
-2 sphincters?
- Internal
- External
Urinary bladder
- Internal sphincter
- Type of control?
- Type of muscle?
- Where is it?
- Involuntary control
- Smooth muscle
- It is the wall of the bladder as it narrows toward the urethra
Urinary bladder
- External sphincter
- Type of control?
- Type of muscle?
- Where is it?
- Voluntary control
- Skeletal muscle
- Wraps around exterior of urethra where it joins bladder
Urinary bladder
-External sphincter-associated nerve?
Pudendal nerve
Urinary bladder
-Internal sphincter-associated nerve?
Pelvic nerve
Hypogastric nerve-slide 6?
?
Local Nervous Control
- Innervation of the urinary tract-afferent pathways for conscious bladder sensations
- Through which nerve or plexus?
- Through pelvic splanchnic nerve or hypogastric plexus
- S2-S4
Local Nervous Control
- Innervation of the urinary tract-afferent pathways for conscious bladder sensations
- Posterior columns?
Bladder fullness
Local Nervous Control
- Innervation of the urinary tract-afferent pathways for conscious bladder sensations
- Anterolateral columns?
Bladder pain
Reflex arc for the micturition reflex-sacral micturition center
-From bladder?
Bladder–>sacral detrusor nucleus–>Bladder?
Reflex arc for the micturition reflex-sacral micturition center
-From urethra?
Urethra–>sacral micturition center–>voluntary sphincter
Efferent nervous controls of the bladder and urethra
- Sensory fibers
- From?
- Activated by?
- From bladder wall, posterior urethra
- Activated by stretch
Parasympathetic fibers
- Neurotransmitter?
- Nerve?
- Functions?
- Cholinergic-acetylcholine
- From sacral micturition center S2-S4 (pelvic nerve)
- Stimulate detrusor muscle
- Inhibit contraction of internal urethral sphincter
Sympathetic fibers
- Neurotransmitter?
- Nerve?
- Functions?
- Neurotransmitter-adrenergic-NE
- Hypogastric nerve
- Inhibits detrusor constriction
- Constricts internal urethral sphincter
Somatic motor neurons
- Type of control?
- Nerve?
- Function?
- Voluntary control
- Pudendal nerve
- Constrict external urethral sphincter
Overview of bladder and urethra?
Slide 12
Central control of micturition-The micturition reflex
- Where is it located?
- What is it called?
- Pontine micturition center (Barrington’s center)
- Locus ceruleus of the pons
Central control of micturition
- Descending impulses control?
- Coordinates?
- Descending impulses control sacral micturition center and thoracolumbar sympathetic outflow
- Coordinates activity of bladder and urinary sphincters
Autonomic modification of ureter peristalsis
-Ureters are supplied with?
-Ureters are supplied with parasympathetic and sympathetic fibers
Autonomic modification of peristalsis
- Ureters are supplied with parasympathetic and sympathetic fibers
- Parasympathetic stimulation function?
- Sympathetic stimulation function?
- Parasympathetic stimulation increases frequency of peristaltic contractions in ureter, increasing urine delivery to bladder
- Sympathetic stimulation does the opposite
Stress-relaxation of the bladder minimizes pressure rise as the bladder fills
-graph on slide 18
Changes in intravesical pressure as the bladder fills with urine
The micturition reflex
- Early bladder filling-As radius increases, wall tension increases
- Equation?
T = (P x r)/2
The micturition reflex
- Early bladder filling
- Which receptors are activated? What do they do?
- Bladder stretch receptors are activated, send sensory information to:
- Sacral micturition center
- Higher centers in brainstem, cerebral cortex
The micturition reflex
- Early bladder filling
- Bladder stretch receptors are activated, send sensory information to: Sacral micturition center-function?
Activates parasympathetics
The micturition reflex
- Early bladder filling
- Bladder stretch receptors are activated, send sensory information to: Higher centers in brainstem, cerebral cortex-function?
Suppress parasympathetic impulses
The micturition reflex
- Later bladder filling
- Increasing?
- Inhibition of?
- Increasing wall tension, more frequent sensory impulses from stretch receptors
- Inhibition of sacral micturition center by higher centers in brain in overridden
The micturition reflex
- Later bladder filling
- Parasympathetic impulses from?
- Function?
- Parasympathetic impulses from?
Parasympathetic impulses from sacral cord:
- Stimulate bladder contraction
- Inhibit contraction of internal urethral sphincter
The micturition reflex
- Later bladder filling
- Urine enters?
Posterior urethra
After urine enters urethra?
- Sensory impulses from urethra to sacral cord inhibit somatic nerves that constrict external sphincter
- Bladder continues to fill, contractions intensify
- Sensory impulses from bladder and urethra become more powerful
- When the time is right, external sphincter relaxes, urine is voided
Bladder empties passively
-What happens to tension of bladder wall?
- Tension of bladder wall declines as urine is voided (T = (P x r)/2
- Decreased radius maintains intravesical pressure despite increased tension
- Enables bladder to empty its residual volume
Slide 24-summary of micturition
….
Abnormalities of micturition (neuropathic bladders)
- Results from damage to neural elements controlling micturition
- Four basic types
- Atonic bladder
- Denervated bladder
- Automatic bladder
- Uninhibited neurogenic bladder
Atonic (flaccid neuropathic) bladder
-Cause?
Destruction of sensory inputs from bladder to sacral cord (diabetes, crush injury, syphilis, MS)
Atonic (flaccid neuropathic) bladder
-Pathology?
- Stretch information no longer transmitted
- Bladder contractions are no longer initiated
- Bladder becomes flaccid and filled to capacity-“Overflow incontinence”;eventually distended, thin-walled
Denervated (hypertrophic areflexic) bladder
-cause?
Destruction of both afferent and efferent fibers between bladder and cord
Denervated (hypertrophic areflexic) bladder
-Initial pathology?
- Detrusor contractions cease
- Bladder becomes flaccid, distended
Denervated (hypertrophic areflexic) bladder
-Later pathology?
- Detrusor regains spontaneous activity
- Bladder shrinks
- Muscle wall hypertrophies
Automatic (spastic neuropathic) bladder
-Cause?
-Injury or severing of spinal cord above sacral region: cuts off communication with brain
Automatic (spastic neuropathic) bladder
- Acute phase?
- Long term?
- ‘spinal shock’ temporarily suppresses micturition reflex–>flaccid neuropathic bladder
- Long term-micturition reflex can gradually recover and become exaggerated resulting in spasticity-control by brain is lost
Uninhibited neurogenic bladder (autonomic dysreflexia)
-Cause?
-Destruction of tracts carrying inhibitory impulses from brain
Uninhibited neurogenic bladder (autonomic dysreflexia)
-Pathology?
- Facilitatory inputs remain intact
- Micturition center is continually stimulated
- Micturition is activated by small amounts of urine
- Detrusor hypertrophies, bladder capacity reduced
Urinary tract infections
-How are they related to the bladder and urethra?
- Bladder and urethral irritation from the infection
- Uninhibited contraction of detrusor muscle with facilitation of the micturition reflex
- Leads to urinary frequency and leakage
3 anatomical divisions of the urinary tract?
- Upper urinary tract
- Bladder
- Urethra
