Micturition Reflex

  1. The micturition reflex involves impulses traveling from the urinary bladder to the sacral region of the spinal cord and from the sacral region of the spinal cord back to the bladder.
  2. It is coordinated by neurons in the spinal cord and can be influenced by signals from the brain.
  3. When the urinary bladder becomes stretched there is an increase in the frequency of action potentials carried from the bladder wall to the sacral region of the spinal cord.
  4. In response, parasympathetic neurons from the spinal cord to the bladder are activated, and this causes the smooth muscle on the bladder wall to contract.
  5. The sensory signals to the sacral region of the spinal cord also stimulate ascending pathways to the pons and cerebrum, which results in a conscious desire to urinate.
  6. If the urination is not convention at the time, the brain sends impulses down the spinal cord to inhibit the micturition reflex.
  7. Impulses carried via somatic motor neurons keep the external urinary sphincter contracted, which also prevents urination.
  8. When urination is desired, signals from the brain stimulate the micturition reflex. The brain also decreases action potentials in the somatic motor neurons to reflex the external urinary sphincter.

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