Test 1 (Physiology of Urinary Tract Micturition Lecture (Dr. McCormik))

Question 1

Urinary Tract has 3 Anatomical Divisions

Answer 1

1) Upper Urinary Tract:
- Calyces, Pelvis, and Ureters

2) Bladder:
- Stores urine under Low Pressure, Expels it under High pressure

3) Urethra:
- A conduit for carrying urine from the body. Its Two Sphincters CONTROL VOIDING

Question 2

Urinary Bladder and Sphincters- Summary

Answer 2

Sphincters:

1) INTERNAL (Involuntary):
- SMOOTH MUSCLE

• It is the Wall of the bladder as it narrows toward the Urethra

2) EXTERNAL (Voluntary):
- SKELETAL MUSCLE which wraps around exterior of Urethra where it joins the Bladder

Question 3

Innervation of the Urinary Tract- Afferent Pathways for CONSCIOUS Bladder Sensations

Answer 3

1) SYMPATHETIC FIBERS:
A) Origin:
- Intermediolateral Spinal Gray Horn (T10- L2)

B) Passes Through:
- Hypogastric Plexus

C) Contracts:
- Sphincter Vesicae

D) Relaxes:
- Detrusor

2) PARASYMPATHETIC FIBERS:
A) Origin:
- Sacral Detrusor Nucleus (S2- S4)

B) Passes Through:
- Pelvic Splanchnic Nerve

C) Contracts:
- Detrusor

D) Relaxes:
- Sphincter Vesicle

3) SOMATIC FIBERS:
A) Origin:
- Sacral Pudendal Nucleus (S2 - S4)

B) Passes Through:
- Hypogastric Plexus and Pelvic Splanchnic Nerve

C) Contracts:
- Rhabdomyosphincters

D) Relaxes:
- None

Question 4

Reflex Arc for the Micturition Reflex- Sacral Micturition Center

Answer 4

1) From Urethra —–> Sacral Pudendal Nucleus (SACRAL MICTURITION CENTER) —–> To VOLUNTARY Sphincter
2) From Bladder —> Sacral Detrusor Nucleus —-> To Bladder

Question 5

Efferent Nervous Controls of the Bladder and Urethra

Answer 5

• Sensory fibers from Bladder Wall, Posterior Urethra are activated by STRETCH!!!

1) PARASYMPATHETIC FIBERS:
- Cholinergic- Acetylcholine
- From SACRAL MICTURITION CENTER S2- S4 (PELVIC Nerve) stimulate Detrusor Muscle
- Inhibits CONTRACTION of Internal Urethral Sphincter

2) SYMPATHETIC FIBERS:
- Adrenergic- NE
- HYPOGASTRIC Nerve
- Inhibits Detrusor Constriction, constructs Internal Urethral Sphincter

3) SOMATIC MOTOR NEURONS:
- Voluntary
- PUDENDAL Nerve
- Constrict External Urethral Sphincter

Question 6

Central Control of Micturition

Answer 6

• PONTINE MICTURITION CENTER (Barrington’s Center)
• Location: Locus CERULEUS of the Pons
• Descending Impulses control SACRAL MICTURITION CENTER and Thoracolumbar Sympathetic OUTFLOW
• Coordinates activity of BLADDER and URINARY SPHINCTERS

Question 7

Peristalsis in Ureter

Answer 7

• Urine is moved down from the Kidney into the Bladder by PERISTALSIS (Coordinated Muscle Contractions) which is INHIBITED by SYMPATHETIC and ACTIVATED by PARASYMPATHETIC!!!!!

Question 8

Autonomic Modification of Peristalsis

Answer 8

• Ureters are supplied with PARASYMPATHETIC and SYMPATHETIC Fibers
• Parasympathetic stimulation INCREASES FREQUENCY of Peristaltic Contractions in URETER, INCREASING Urine delivery to Bladder
• SYMPATHETIC STIMULATION does the OPPOSITE!!!!

Question 9

Stress- Relaxation of the Bladder

Answer 9

Stress- Relaxation of the Bladder MINIMIZES PRESSURE RISE as the Bladder Fills

• Once the Volume of the Bladder hits 400 mL there is a sharp SLOPE on the Increase in the Pressure Curve!

Question 10

Bladder Filling

Answer 10

• AS a radius INCREASES, Wall Tension INCREASES:

T = (P x r)/ 2

• Bladder STRETCH Receptors are Activated, Send Sensory Information to:
  a) SACRAL MICTURITION CENTER: Activated PARASYMPATHETIC

b) Higher centers in Brainstem, CEREBRAL CORTEX: SUPPRESS PARASYMPATHETIC IMPULSES!!!!!!!!!!

Question 11

Ladder Bladder Filling

Answer 11

• Increasing Wall Tension causes more frequent SENSORY IMPULSES from STRETCH Receptors
• Inhibition of SACRAL MICTURITION CENTER by Higher Centers in brain is OVERRIDDEN!!!
• PARASYMPATHETIC Impulses from Sacral Cord:
  a) Stimulate Bladder CONTRACTION

b) Inhibit CONTRACTION of Internal Urethral Sphincter
- Urine enters POSTERIOR URETHRA

Question 12

After Urine enters Urethra

Answer 12

• Sensory impulses from URETHRA to SACRAL CORD INHIBIT Somatic Nerves that constrict External Sphincter
• Bladder continues to FILL; its Contractions INTENSIFY
• Sensory Impulses from Bladder and Urethra become MORE POWERFUL! When the time is right:
  a) EXTERNAL SPHINCTER Relaxes, Urine is VOIDED!!

Question 13

Bladder Empties Passively

Answer 13

• Tension of Bladder wall DECLINES as Urine is Voided:

T = (P x r)/ 2

• DECREASED RADIUS maintains INTREAVESICAL PRESSURE despite DECREASED TENSION

P= 2T/ r

….. Enabling Bladder to EMPTY to its Residual Volume (

Question 14

Sequence of Voiding Events

Answer 14

1) Bladder begins filling
2) Stretch activates Sensory Inputs
3) Parasympathetics: Bladder Contracts, Internal Sphincter Relaxes
4) Brainstem SUPPRESSES PNS
5) Somatic Motor constricts EXTERNAL SPHINCTER (Pudendal Nerve)
6) Bladder continues filling
7) Urine enters Urethra, activates Stretch Receptors
8) Sensory Impulses Intensify
9) External Sphincter Relaxes
10) VOIDING

Question 15

Neuropathic Bladders

Answer 15

• Results from DAMAGE to Neural elements controlling Micturition

Four Basic Types:
1) Atonic Bladder

2) Denervated Bladder
3) Autonomic Bladder
4) Uninhibited Neurogenic Bladder

Question 16

Autonic (Flaccid Neuropathic) Bladder

Answer 16

1) CAUSE:
- Destruction of sensory inputs from Bladder to Sacral Cord (Diabetes, Crush Injury, Syphilis, MS)

2) STRETCH Information no longer transmitter
- Bladder CONTRACTION are NO LONGER INITIATED

3) Bladder becomes FLACCID
- Filled to Capacity “Overflow Incontinence”

• Eventually distended, thin- walled

Question 17

Denervated (Hypertrophic Areflexic) Bladder

Answer 17

1) CAUSE:
- Destruction of BOTH AFFERENT and EFFERENT Fibers between Bladder and Cord

2) INITIALLY:
- Detroser CONTRACTIONS cease

• Bladder becomes FLACCID, DISTENDED

3) LATER:
- Detrusor REGAINS SPONTANEOUS ACTIVITY

• Bladder Shrinks
• Muscle wall HYPERTROPHIES

Question 18

Uninhibited Neurogenic Bladder (Autonomic Dysreflexia)

Answer 18

1) CAUSES:
- Destruction of tracts carrying INHIBITORY IMPULSES from Brain

2) Facilitatory Inputs REMAIN INTACT
- Micturition center is continually STIMULATED

3) Micturition is activated by Small amounts of URINE

4) Detroser Hypertrophies
- Bladder CAPACITY REDUCED

Question 19

Automatic (Spastic Neuropathic) Bladder

Answer 19

1) CAUSE:
- Injury or severing of Spinal Cord above Sacral Region

• This CUTS OFF Communication with the Brain

2) ACUTE PHASE:
- “SPINAL SHOCK”

• Temporarily Suppresses Micturition Reflex —-> FLACID Neuropathic Bladder
  3) Micturition Reflex can gradually Recover and become Exaggerated resulting in SPASTICITY - Control by Brain is LOST!!!

Question 20

Urinary Tract Infection

Answer 20

• Bladder and Urethral Irritation from the Infection
• Uninhibited CONTRACTION of Detrusor Muscle with facilitation of the Micturition Reflex
• Leads to URINARY FREQUENCY and LEAKAGE

***Major pathogen: E. coli

***Major pathogen in 19 - 24 y/o Sexually Active Females: Staphylococcus

Question 21

Summary: Physiology of Urinary Tract

Answer 21

• Ureters carry urine to Bladder by PERISTALSIS
• Bladder can store lots of urine under LOW PRESSURE
  a) Bladder Wall Tension INCREASES during filling to initiate Micturition

b) Bladder pressure is maintained during voiding by LAW of LaPlace
- Micturition Reflex: Initiated by Sensory Fibers, orchestrated by PARASYMPATHETIC Motor Fibers
- Damage to Neural Elements causes Micturition Abnormalities