Search for notes by fellow students, in your own course and all over the country.
Browse our notes for titles which look like what you need, you can preview any of the notes via a sample of the contents. After you're happy these are the notes you're after simply pop them into your shopping cart.
Document Preview
Extracts from the notes are below, to see the PDF you'll receive please use the links above
Micturition
8
...
8
...
1 Bladder
The bladder is a hollow muscular sac that sits on the pelvic floor and varies in
size according to the volume of urine it contains (k Fig
...
8)
...
The bladder wall contains three involuntary smooth muscles:
• trigone – a triangular area on the floor of the bladder which is very
sensitive to stretch; when the bladder is full, nerve endings detect the
stretch and transmit the information to the spinal cord
• detrusor muscle contracts and expels urine
• internal urethral sphincter must relax in order to allow urine to be
expelled
...
One is
voluntary, the other involuntary, and both function as sphincters (rings of
muscle tissue)
...
It is
composed of skeletal muscle and therefore under voluntary control, and
must relax to allow voiding of urine
...
URINARY
BLADDER
rugae
detrusor muscle
left ureter
ureteral openings
trigone
bladder neck
internal urethral sphincter
pelvic floor muscle
external urethral sphincter
urethra
Fig
...
8 Section through the bladder of a female
...
4
...
8)
...
8
...
3 Voluntary control of voiding
The urge to empty the bladder is perceived as an uncomfortable sensation that
is correlated with the level of filling of the bladder
...
Impulses from spinal neurons stimulate the contraction of the
detrusor muscle until the pressure of urine is high enough to empty the
bladder
...
8
...
Box 8
...
Box 8
...
Box 8
...
Symptoms include an urgent
feeling to urinate or urinating
frequently
...
However, if the bladder has become too full, or if a person is very frightened,
then sphincters can relax involuntarily, allowing urine to be voided
...
4
...
14)
...
g
...
This is usually due to weakening
of the muscles used to prevent urination such as the pelvic floor muscles
and urethral sphincter
...
15)
• urge incontinence is a sudden, intense urge to pass urine
...
It
is possible to have a mixture of both stress and urge incontinence (k Box
8
...
g
...
EMPTYING
THE BLADDER
URINE
STORAGE
control centre
recognition of appropriate
time and place
(from the age of 2–3 years)
inhibition
of voiding
cerebral cortex (brain)
integrating centre
coordination
of the voiding
response
coordination
of the storage
response
brainstem (pons)
somatic parasympathetic
neurons
neurons
inhibited
stimulate
+
–
spinal
centres
sympathetic
neurons
motor
neurons
sensory neurons
send impulses
about fullness of
the bladder
contraction of
detrusor muscle
R
internal
sphincter
pelvic floor
muscle
external
sphincter
relaxes to
allow flow
relaxation of
detrusor muscle
which lines the
bladder
external sphincter
sensory (afferent) neurons
interneurons
motor (efferent) neurons
external
sphincter
contracts and
stops flow
Fig
...
9 The urinary bladder stores urine, allowing it to be emptied at infrequent intervals