Micturition reflex and bladder dysfunctions

1. Lower Urinary tract
Dr Ambika Jawalkar

2. Introduction
 Renal pelvis  Ureter
Ureter – muscular tube. Length - 30 cm
 2 ureters [i.e. one from each kidney] enter
urinary bladder on posterior side above
bladder neck.
Urinary bladder-
i. Upper – fundus;
ii. Lower – bladder neck.
 Functional valve of ureter – due to oblique
passage thro wall of urinary bladder

4. Filling of urinary bladder –
Peristaltic contractions of muscular wall of
ureters  push urine in spurts.
Gravity helps.
Applied –
 Prevention of reflux of urine –
due to functional valve.
 If absent leads to
Cystitis 
glomerulonephritis 
Chronic renal failure.

5.  Structure of urethra
 Male – Length - 15 -20 cm [extend
through penis]
 Female - Length – 4 cm
 2 orifices –
 Internal urethral orifice – formed
by detrusor muscle fibres in
bladder neck
 External urethral orifice – formed
by skeletal muscle fibres
 Trigone of urinary bladder
–
 Triangular portion between
openings of ureters & int urethral
orifice
 Microscopic –
 Transitional epithelium which has
ability to distend

6. Innervation of bladder
[sympathetic, parasympathetic & somatic]
Sympathetic –
 Lateral horn cells of L1, L2, L3 spinal cord
segments  sympathetic ganglion.
 Postganlionic thro Hypogastric nerve  body,
bladder neck & urethra
 Body - b adrenergic receptors.
 On stim  relaxation of detrusor muscle.
 Trigone + Int Ure Sphi - a adrenergic receptors.
 On stim  contraction of muscle.
 Sympathetic stim  storage of urine. [Relaxation of
body + contraction of Int US].

8. Parasympathetic innervation
 Carry both afferent [sensory] & efferent [motor]
 Origin – S1,S2,S3 spinal cord segments.
  pelvic nerves & relay in ganglia in bladder wall.
 Fundus of bladder – post ganglionic fibers
 Sensory –
 sense of fullness, pain to sacral segments
 afferent limb of spinal reflex of urination
 [note – input also to higher center]
Parasympathetic stim.  urination.
 [contraction of body + relaxation of IUS]

10. Somatic
Innervation
 Origin – S2,S3,S4 spinal
segments.
  Pudendal nerve 
 ext. urethral sphicter.
 Note –
 EUS is striated ,
 voluntary muscle.

11. MICTURITION Defn –
 it is a process of emptying urinary bladder.
 It is an automatic spinal reflex which can be modified by
higher centers in the brain stem & cerebral cortex i.e.
 can be initiated voluntarily &
 can be stopped voluntarily because of cerebral cortical control of
EUS.
1. Stimulation of stretch receptors in UB – due to filling of UB
2. Afferent – Parasympathetic sensory thro PELVIC NERVE
[S1,S2,S3]
3. Center - [S1,S2,S3] spinal segments.
4. Efferent - Parasympathetic motor thro PELVIC NERVE
[S1,S2,S3]
5. Effector – detrusor + IUS
6. Response – Detrusor – contraction; IUS - relaxation

12. Control of micturition by Higher centers
 Higher centers –
 at brain stem &
 cerebral cortex.
 Proprioceptive like feeling of fullness & desire to void urine thro
fasciculus Gracilis  cerebral cortex 
 efferent fibres thro pyramidal tract  spinal cord.
Spinal micturition reflex starts –
 5th week of IUL.
 Continued upto 3 yrs of age.
 Voluntary control attained slowly by training the child

13. I] Function of brainstem center [at unconscious
level]
i. Function of brainstem inhibitory center at mid brain [at
unconscious level]
a) 1st desire to void urine =
 at 150 -250 ml. IVV [intra vesical volume].
 Can be inhibited by brainstem inhibitory center.
b) Urge to void
 at 500 -600ml IVV
 associated with discomfort & pain.
ii. Function of brainstem fascilitatory center at pons [at unconscious
level].
 II]Function of CC [at conscious level].
 Due to voluntary control of EUS + perineal muscles.
a) Inhibit spinal centers when conditions are unfavorable
+

15. Continence – is urine retaining
power of UB for some time due to
tone of smooth muscle of IUS.
Incontinence – lack of voluntary
control over urination.
Normal in children below 2 yrs.
In adults – abnormal. Due to
a) Injury to spinal cord
b) Injury to spinal nerves innervating UB
c) States of unconsciousness.

16. Urinary retention is failure to void
urine – Due to
 Obstruction of urethra. e.g. enlarged
prostrate
 Lack of sensation to urinate

17. Abnormalities of bladder function
1. Atonic Bladder or Tabetic
Bladder
2. Autonomous Bladder
3. Automatic Bladder
4. Spastic Neurogenic Bladder
5. Nocturnal enuresis

18. Atonic Bladder or Tabetic
Bladder
 Damage to afferent limb of reflex arc –
i. e.g. tabes dorsalis [neurosyphilis],
ii. Injury to nerve
 Reflex contraction of UB absent.
 Urinary Bladder is –
a) Thin ,
b) Hypotonic &
c) Distended
 No periodic emptying of UB  full UB  overflow
incontinence

19. Autonomous Bladder
 Damage to both afferent & efferent
nerves e.g. tumours of cauda equina.
 Urinary Bladder is
i. Flaccid &
ii. Distended
  dribbling of urine with shrunken &
hypertrophied UB

20. Automatic Bladder
 In transection of spinal cord
 Urinary Bladder is
i. Hypotonic,
ii. Distended,
  Overflow incontinence
 Note –
 if catheterization is done during the stage of spinal
shock,
 micturition reflex reappears but no voluntary
control.

21. Spastic Neurogenic Bladder
 Lesion in Brainstem OR spinal
cord.
a) Inhibitory influence = Absent ;
b) Fascilitatory signals = Present.
 Urinary Bladder is
i. Hyperactive;
  Uncontrollable micturition

22. Nocturnal enuresis
Poorly developed nervous control of
bladder.
i. In children -
 may be normal.
ii. In Adults –
 diseases of sacral spinal segments.

23. Cystometry
 Detrusor is smooth muscle & has plasticity property i.e.
 urine gets filled without much increase in Intra vesical pressure
[IVP].
 Cystometry –
 study of relationship IVP to IVV.
 Procedure –
1. Double lumen catheter into UB & empty it.
2. Fill with 50ml of water increments &
measure IVP
3. Cystometrogram - Graph plotted with IVV in
X axis & IVP in Y axis.

24. Cystometrogram -
Graph plotted with
 IVV [in ml] at X axis &
 IVP [in cm of water] at Y
axis.

25. CYSTOMETROGRAM [ 3 phases]
 1st phase [Ia] - Slight  in
pressure [IVP]
 2nd phase[Ib] - Flat
segment
 due to manifestation of
Law of Laplace.
 i.e. In a hollow organ P=
2T/R.
 To maintain low pressure
[P], Tension [T] of wall of
UB reduces
 Due to smooth muscle
plasticity property by it’s
relaxation
 3rd phase[II] - Sharp rise
in IVP when IVV exceeds
400 ml