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

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Flashcards in Test 1 (Physiology of Urinary Tract Micturition Lecture (Dr. McCormik)) Deck (21):
1

Urinary Tract has 3 Anatomical Divisions

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

2

Urinary Bladder and Sphincters- Summary

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

3

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

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

4

Reflex Arc for the Micturition Reflex- Sacral Micturition Center

1) From Urethra -----> Sacral Pudendal Nucleus (SACRAL MICTURITION CENTER) -----> To VOLUNTARY Sphincter


2) From Bladder ---> Sacral Detrusor Nucleus ----> To Bladder

5

Efferent Nervous Controls of the Bladder and Urethra

- 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

6

Central Control of Micturition

- 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

7

Peristalsis in Ureter

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

8

Autonomic Modification of Peristalsis

- 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!!!!

9

Stress- Relaxation of the Bladder

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!

10

Bladder Filling

- 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!!!!!!!!!!

11

Ladder Bladder Filling

- 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

12

After Urine enters Urethra

- 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!!

13

Bladder Empties Passively

- 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 (

14

Sequence of Voiding Events

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

15

Neuropathic Bladders

- Results from DAMAGE to Neural elements controlling Micturition

Four Basic Types:
1) Atonic Bladder

2) Denervated Bladder

3) Autonomic Bladder

4) Uninhibited Neurogenic Bladder

16

Autonic (Flaccid Neuropathic) Bladder

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

17

Denervated (Hypertrophic Areflexic) Bladder

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

18

Uninhibited Neurogenic Bladder (Autonomic Dysreflexia)

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

19

Automatic (Spastic Neuropathic) Bladder

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!!!

20

Urinary Tract Infection

- 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

21

Summary: Physiology of Urinary Tract

- 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