Bladder & Micturition Flashcards
What begins the lower urinary tract?
Bladder
What are the 3 layers of the bladder?
Outer peritoneum
Layer of smooth muscle and connective tissue (detrusor muscle)
Inner mucosal layer
What’s the difference between the bladder neck (intrinsic sphincter) muscle fibers between men and women?
Women have bundles that slant downwards into the urethra that are instrumental for maintaining continence.
Men have muscles that form a complete ring around the neck. Together with smooth muscle fibers of the prostate, they form the urethral sphincter.
Does the bladder have smooth or skeletal muscle?
Smooth
What does the rhabdosphincter muscle do?
Skeletal muscle that can close the urethra if you want to stop peeing.
What is micturition?
Voiding/urinating
Is the control of micturition autonomic or CNS?
Both. It involves both autonomic and CNS systems
What is the most important innervation of the lower urinary tract?
Parasympathetic nerve fibers that innervate the detrusor muscle. Activation results in detrusor muscle contraction and micturition.
If you don’t have this, you can’t urinate.
What does sympathetic innervation do for the lower urinary tract?
Sympathetic activation inhibits the detrusor muscle contraction and increases tension in the smooth muscle of the bladder neck and proxima urethra, preventing micturition until parasympathetic stimulation occurs.
Explain the motor (somatic) innervation of the lower urinary tract
S2-S4 controls the bladder, pelvic floor, and urethral sphincter. Sensations of bladder fullness or stretch are conveyed through long neurons from the spinal cord to the pons.
“S2, 3, 4 keeps the penis off the floor”
Explain this diagram *know this*
The S2-4 gives rise to pelvic nerves and pudendal nerves. The pudendal nerves are the somatic innervation that control the external urethral sphincter and muscles of the pelvic floor. The pelvic nerves are the parasympathetic innervation for the bladder.
T10-L2 gives rise to hypogastric nerves which give sympathetic innervation to the bladder.
The cortex of the brain is predominantly inhibitory. How can damage to the cortex effect micturition?
Loss of central cortical inhibition over sacral centers occurs in diseases like dementia, stroke, parkinsonism. This causes incontinence.
When you have the urge to urinate due to bladder filling, the cortex is what allows your to say “no”. Damage to this causes incontinence.
Babies don’t have a fully developed cortex and that’s why they don’t have the inhibition either.
The dorsal root carries ____ signals to the spinal cord and the ventral root carries _____ signals from the spinal cord.
sensory, motor
The bladder is made of smooth muscle and can expand to hold more volume. If there is a problem with storage function, what 3 things occur?
What happens if there is a problem with voiding function? What 3 things can occur?
- Storage function problems
- increased frequency of urination
- increased urgency
- urge incontinence
- Voiding function problems
- Hesitancy
- Weak stream
- Incomplete bladder voiding
Explain the afferent and efferent responses of storage reflexes for the bladder.
Afferent activity is generated by filling of the bladder. Sensory fibers in the pelvic nerve enters the sacral cord via the sacral dorsal root ganglion.
Efferent responses to bladder filling are controlled at supraspinal levels by activating somatic (pudendal) motor neurons in the anterior horn of the sacral spinal cord. These responses are associated with inhibition of the detrusor motor neuron with cortical inhibition of detrusor activity.
