MICTURITION REFLEX

1. DR NILESH KATE
MBBS,MD
ASSOCIATE PROF
DEPT. OF PHYSIOLOGY
MICTURITION

2. OBJECTIVES
 Micturition
 Functional anatomy of bladder
 Innervation of bladder
 Physiology of Micturition
 Filling of bladder
 Cystometrogram
 Emptying of bladder
 Nervous reflex
 Higher centers of micturition
 Applied
 Atonic bladder; Automatic bladder
 Neurohenic bladder; Nocturinal eneuresis
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3. URINARY BLADDER AND
URETHRA
 Gross Anatomy
 External Features – hollow
muscular viscous for urine
 Pyramidal , having apex, base &
3 surfaces
 Neck – lowest part, continues
as urethra
 Interior Of Bladder –
mucosa shows irregular
folds, & smooth trigone.
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4. STRUCTURE OF THE
BLADDER.
 Wall – 3 layers, outer serous,
middle smooth muscle &
inner mucous membrane.
 Mucous membrane –
transitional epithelium.
 Stretches when distends
 Complete barrier for fluid &
electrolytes.
 Glycosaminoglycan barrier that
prevents bacterial adherence.
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5. BLADDER - ANATOMY
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6. MUSCULAR LAYER.
 Smooth muscle fibre
of Detrusor Muscle
 Arranged in
interlacing
longitudinal, circular,
spiral bundles
 Responsible for
emptying of Bladder.
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7. URETHRA & ITS
SPHINCTERS.
 Male urethra – 20 cm
 3 parts – prostatic,
membranous, penile
 Membranous surrounded
by external sphincters.
 Female urethra-3.8 cm
 Traverses external
sphincters
 Lies in front of vagina.
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8. SPHINCTERS OF THE
URETHRA
 Internal sphincters –
circular smooth muscle fiber
in area of neck.
 Prevents emptying up to
pressure of threshold level.
 External sphincters.
 at the level of Urogenital
Diaphargm encircled by ring
of voluntary muscles
 Provides voluntary control.
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9. INNERVATION OF THE URINARY
BLADDER. MOTOR INNERVATIONS.
 Parasympathetic Innervations.- S2,3,4
 Motor impulses to urinary bladder
 Contract bladder & inhibit internal sphincter
 Sympathetic Innervations.- T11-L2
 Opposite to Parasympathic
 Somatic Motor Innervations – somatic Pudendal
Nerve supplies external sphincters which is
voluntary.
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10. INNERVATION OF THE URINARY
BLADDER- SENSORY INNERVATIONS.
 Sensation of Bladder
Distension
 Afferent from Detrusor stretch
receptors to spinal cord via
pelvic Splanchnic nerves.
 From Trigone & Bladder neck
via hypogastric plexus to T11-
L2.
 Reach pontine & suprapontine
micturition cenetrs.
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11. INNERVATION OF THE URINARY
BLADDER- SENSORY INNERVATIONS.
 Sensation of bladder
Pain. – stimulates by
stone, distension, spasm,
inflammation or
malignant disease.
 Via lateral
Spinothalamic tract.
 Urethral sensations –
reach spinal cord via
Pudendal nerve.
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12. Innervations of bladder
12
Hypogastric Ganglia

13. MICTURITION
 Micturition is a process by which urinary bladder
empties when it becomes filled
 Begins in 5th
month of intrauterine life
 Remain as reflex up to 2-21/2 yrs of age.
1. Filling of Bladder - progressively till the tension of the
wall rise above threshold
2. Emptying of Bladder - Nervous reflex – micturition
reflex that emptied the bladder or atleast conscious
desire of urination
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14. BLADDER INNERVATION – Mode of Action
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15. INNERVATIONS OF BLADDER -
FUNCTION
Nerve
On
detrusor
muscle
On internal
sphincter
On external
sphincter
Function
Sympatheti
c nerve
Relaxation
Constrictio
n
Filling of
urinary
bladder
Parasympat
hetic nerve
Constrictio
n
Relaxation
Emptying of
urinary
bladder
Somatic
nerve
Constrictio
n
Voluntary
control of
micturition
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16. FILLING OF THE BLADDER
Urine collects in the renal
pelvis, the pressure in the
pelvis increases.
The walls of
ureters --
smooth
muscle
arranged in
spiral,
longitudinal
and circular
bundles.
Peristaltic waves occur
1-5 times/minute
spreading downward
along the ureter to
force urine toward the
bladder.
Initiates a peristaltic
contraction beginning in
the pelvis
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17. CAPACITY OF THE BLADDER.
 Physiological Capacity –
 Varies with age
 20-50 ml at birth
 200 ml – 1 yr
 600 ml – adult
 Twice that at which first desire to void is
felt
 Anatomical Capacity.
 Capacity beyond which it rupturs
 1L – never reached under physiological
conditions.
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18. PRESURE & VOLUME CHANGES IN
BLADDER DURING FILLING.
 When complete empty –
intra-vesical pressure =
intra-abdominal pressure.
 As it fills – causes
adaptation due to
inherent property of
plasticity.
 Law of Laplace – P α 1/R
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19. CYSTOMETROGRAM
 Cystometry
 It is the technique used to demonstrate the
relationship between the intravesical
pressure and the volume of urine in the
bladder.
 Cystometrogram It is the graphical recording of
pressure changes in urinary bladder in relation
to rise in the volume of urine.
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20. NORMAL CYSTOMETROGRAM
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21. METHOD OF RECORDING
CYSTOMETROGRAM
 Double lumen catheter
introduced in bladder.
 Fluid is introduced
through one
 Pressure is recorded
through other.
 Each time bladder is
filled with 50 ml of fluid
& change in pressure is
noted.
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22. BLADDER FILLING
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23. NORMAL CYSTOMETROGRAM
 3 PHASES.
 Phase Ia – upto 50 ml –
pressure changes to 0-
10
 Phase Ib – from 50 ml
-400 ml, pressure does
not change much,
remains 10 cm of H2O,
due to adaptation By
Relaxation.
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24. NORMAL CYSTOMETROGRAM
 Phase II – starts beyond
400 ml, pressure
changes markedly
triggering Micturition
Reflex
 Voiding contractions
raises pressure more by
20-40 cm of H2O
 After 600 ml , urge
becomes unbearable.
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25. 25
Excitation of stretch
receptors when
~300ml of urine
Relayed to
parasympathetic
NS
Contraction of
bladder
Bladder
outlet pulled
open,
increase in
pressure
Micturition
Pelvic
splanchinic
nerves
Pelvic nerv
Pudendal
impulses
nerve
inhibited

26. REPONSE.
 Once reflex originated –more contraction – more
pressure – more stretch – more contraction.
 After some time reflex fatigue remains inhibited
 Once becomes strong enough – stimulate pudendal
nerves & inhibit ext sphincter
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27. HIGHER CENTRE INFLUENCE ON
MICTURITION
This is completely autonomic spinal reflex
Inhibitory Centers for Micturition
 In midbrain and cerebral cortex inhibit the
micturition by suppressing spinal
micturition centers.
Facilitatory Centers for Micturition
 In pons and posterior hypothalamus
facilitate micturition via spinal centers.
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28. VOLUNTARY CONTROL OF
MICTURITION.
 Micturition reflex is fundamentally Spinal Reflex
 Fascilited & inhibited by supra-spinal center.
 Higher centers keep it inhibited all time.
 Even when micturition reflex can prevent it by
continuous contraction of ext urethral sphincter.
 When convenient time higher center facilitate
Sacral Micturition Center – initiate micturition
reflex & inhibit ext sphincter.
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29. Wednesday, May 18, 2016

30. APPLIED PHYSIOLOGY
The abnormalities of micturition
Atonic bladder
Automatic bladder
The uninhibited neurogenic bladder
Urinary incontinence
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31. ATONIC BLADDER
 Due to the destruction of sensory
nerve fibers from urinary
bladder - Syphilis, tabes dorsalis
 Due to the absence of sensory
impulses, the detrusor muscle
loses the tone and becomes
flaccid. No contraction of muscle
 It is also called overflow
dribbling / overflow
incontinences / Tabetic bladder
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32. AUTOMATIC BLADDER
 After complete Transection of spinal
cord above sacral segments
 The urinary bladder loses the tone
and fails to give response to the
micturition reflex.
 The voluntary control of micturition is
lost. Whenever, the bladder is filled
with some amount of urine, there is
automatic evacuation of bladder.
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33.  Duo to lesion in brainstem, there is
continuous excitation of spinal
micturition centers
 The Frequency of Micturition is Increased
with a small quantity of urine collected in
bladder will elicit the micturition reflex.
THE UNINHIBITED NEUROGENIC
BLADDER
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34. NOCTURNAL MICTURITION
 Enuresis or bed wetting.
 Common in infants and children below
3 years.
 It is because of the underdevelopment
of voluntary control of micturition
which is due to Incomplete
myelination of motor nerve fibers of
the bladder.
 When myelination is complete,
voluntary control of micturition
develops and enuresis stops in these
children.
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35. OTHER APPLIED
 Ureterorenal reflexUreterorenal reflex
 Ureter is blocked eg. by a ureteral stone, there will be intense reflex
constriction which is associated with very severe pain.
 These pain impulses cause a sympathetic reflex back to the kidney
to constrict the renal arterioles, thereby decreasing urinary output
from that kidney. a
 Urinary incontinence:Urinary incontinence:
 Urinary incontinence (UI) is any Involuntary leakage of Urine.
 Urinary retentionUrinary retention
 Urinary retention, also known as ischuria, is a lack of ability to
Urinate.
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36. RECENT ADVANCE - MALE URINARY INCONTINENCE
Artificial Urinary Sphincter
(AUS)

37. SUMMARY Micturition
 Functional anatomy of bladder
 Innervation of bladder
 Physiology of Micturition
 Filling of bladder
 Cystometrogram
 Emptying of bladder
 Nervous reflex
 Higher centers of micturition
 Applied
 Atonic bladder; Automatic bladder
 Neurohenic bladder; Nocturinal eneuresis 37

38. Wednesday, May 18, 2016

39. Thank
You