THE BLADDER; INNERVATION Flashcards
- a bag of smooth muscle that stores urine and contracts to expel urine under voluntary control
- a low-pressure system that expands to accommodate increasing volumes of urine without an appreciable rise in pressure
- function appears to be mediated primarily by the sympathetic nervous system
Bladder
- there is an accompanying increase in outlet resistance
- bladder muscle (the detrusor) remains inactive during bladder filling, without involuntary contraction
BLADDER FILLING
when the bladder has filled to a certain volume, fullness is registered by tension-stretch receptors, which signal the brain to initiate a
micturition reflex
controlled by cortical control mechanisms, depending on the social circumstances and the state of the patient’s nervous system
MICTURITION REFLEX
- accomplished by voluntary relaxation of the pelvic floor and urethra,
- accompanied by sustained contraction of the detrusor muscle, leading to complete bladder emptying
NORMAL VOIDING
three innervation of lower urinary tract
- sympathetic
- parasympathetic divisions of ANS
- neurons of the somatic nervous system
plays only a peripheral role in neurologic control of the lower urinary tract through its innervation of the pelvic floor and external urethral sphincter
neurons of the somatic nervous system (external urethral sphincter
where does the sympathetic nervous system originates?
thoracolumbar spinal cord, principally T11 through L2 or L3
postganglionic neurotransmitter
norepinephrine
two types of receptors
- a receptors
- b receptors
where does alpha receptors located?
located principally in the urethra and bladder neck
where does beta receptors located?
located principally in the bladder body
Stimulation of α-receptors increases
- urethral tone
thus promotes closure
Stimulation of β-receptors
- decreases tone in the bladder body
controls bladder motor function—bladder contraction and bladder emptying
parasympathetic nervous system
origin of sacral spinal cord
s2-s4
as the somatic innervation of the pelvic floor, urethra, and external anal sphincter
- Sensation in the perineum is controlled by sensory fibers that connect with the spinal cord at this level
is the main neurotransmitter used in bladder muscle contraction,
acetylcholine
Controls the bladder storage
Sympathetic
Controls bladder emptying
Parasympathetic
Plays ONLY a PERIPHERAL ROLE in neurologic control of the lower urinary tract through its innervation of the pelvic floor and external urethral sphincter
Neurons of the SOMATIC NERVOUS SYSTEM
Controls bladder motor function—>bladder contractions and bladder emptying
Parasympathetic nervous system
Main neurotransmitter used in bladder muscle contraction
Acethylcholine
promotes the bladder to relax (inhibition)
sympa or parasympa
sympathetic system
promotes the outlet to contract (stimulation)
sympa or parasympa
parasympathetic system
