Summary of Urinorganen 5(5) Miktion

Scientific Concepts and Physiological Mechanisms of Urination (Micturition)

• Anatomy of the Urinary Bladder and Sphincters:
  • The urinary bladder is composed of smooth muscle called the detrusor muscle.
  • There are two sphincters controlling urine flow:
    • internal sphincter: smooth muscle, involuntary control.
    • external sphincter: striated muscle, under voluntary control.
  • The ureters bring urine from the kidneys to the bladder, opening at the back of the bladder near the urethra.
• reflex arc in Urination:
  • Urination in infants is primarily a reflex involving:
    1. Receptors: Stretch receptors in the bladder wall detect bladder filling.
    2. Afferent sensory neurons: Carry signals from stretch receptors to the spinal cord.
    3. Integration center: Spinal cord processes the signals.
    4. Efferent motor neurons: Parasympathetic neurons send signals to contract the detrusor muscle.
    5. Effectors: detrusor muscle contracts and internal/external sphincters relax, allowing urine to flow.
  • This reflex arc allows automatic urination without brain involvement in infants (autonomous bladder).
• Role of the Brain in Adult Micturition:
  • In adults, the brain modulates the reflex by sending inhibitory signals to prevent urination until socially appropriate.
  • As the bladder fills, stretch receptors send signals to the spinal cord and brain.
  • The brain suppresses the reflex until voluntary relaxation of the external sphincter and contraction of the detrusor muscle occur.
  • This control allows voluntary initiation and inhibition of urination.
• Voluntary Control and Reflex Interaction:
  • Adults can initiate urination voluntarily by relaxing the external sphincter and contracting abdominal muscles.
  • Once urination starts, a reflex is triggered that promotes detrusor contraction and sphincter relaxation.
  • Urination can also be voluntarily stopped midstream by contracting the external sphincter.
• Clinical Relevance:
  • In people with spinal cord injuries, brain signals may not reach the bladder, leading to an autonomous bladder where urination occurs reflexively at a certain bladder volume without voluntary control.

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Summary of Micturition Mechanism:

• Bladder fills → stretch receptors activated → sensory signals to spinal cord.
• In infants: spinal reflex triggers detrusor contraction and sphincter relaxation → urination.
• In adults: brain sends inhibitory signals to suppress reflex until voluntary urination.
• Voluntary relaxation of external sphincter + detrusor contraction → urination.
• Voluntary contraction of external sphincter can stop urination midstream.
• spinal cord injury can lead to loss of voluntary control → autonomous bladder reflex.

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Researchers or Sources Featured

No specific researchers or external sources were mentioned in the subtitles. The explanation appears to be a general physiological overview likely from a medical or biological educational context.

Notable Quotes

— 06:21 — « When the brain senses that Oh my god, it's starting to get a lot, the brain is also involved and constantly sends down inhibitory signals that say, don't pee, don't pee, don't pee, don't pee, don't pee. »

— 06:46 — « Then when it's time to go to the toilet, you just go to the toilet and then we turn off the brain from this inhibitory reflex. And then only friend comes in. »

— 07:32 — « People with back injuries where the signals from the brain don't work can have this kind of autonomous bladder so that at a certain level of filling it urinates. »

— 08:26 — « You can stop the mission once it has started if I have started to urinate and so Oh now someone comes and sees me here I was standing here urinate here on a place where you can't at all Yes you can do that by willfully contract the external failure. »

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