Micturition Reflex.

Summary

The micturition reflex controls urination by involving signals between the bladder, spinal cord, and brain. When the bladder stretches, it sends signals to the sacral region of the spinal cord, activating parasympathetic neurons that cause the bladder to contract. These sensory signals also travel to the brain, creating a conscious urge to urinate. If urination isn’t convenient, the brain sends signals to inhibit the reflex and keep the external urinary sphincter contracted. When urination is desired, the brain relaxes the sphincter, allowing urination to occur.

Takeaways

• 🟢 The micturition reflex involves impulses traveling between the urinary bladder and the sacral region of the spinal cord.
• 🔁 The reflex is coordinated by neurons in the spinal cord and can be influenced by signals from the brain.
• 📈 When the bladder becomes stretched, the frequency of action potentials sent to the spinal cord increases.
• 🧠 Parasympathetic neurons are activated, causing the bladder's smooth muscle to contract, initiating the urge to urinate.
• ⬆️ Sensory signals also stimulate ascending pathways to the pons and cerebrum, creating the conscious desire to urinate.
• 🚫 If urination isn't convenient, the brain sends inhibitory signals down the spinal cord to stop the reflex.
• 🔒 Somatic motor neurons keep the external urinary sphincter contracted, preventing involuntary urination.
• ✔️ When urination is desired, the brain stimulates the micturition reflex and reduces action potentials in the somatic motor neurons.
• ⚙️ The relaxation of the external urinary sphincter occurs when the brain reduces inhibition, allowing urination.
• 🧩 The process involves a complex interaction between spinal cord neurons, parasympathetic control, and brain signaling.

Q & A

What is the micturition reflex?

The micturition reflex is the process that involves impulses traveling from the urinary bladder to the sacral region of the spinal cord and back to the bladder, coordinating bladder contraction and urination.

What role do the neurons in the spinal cord play in the micturition reflex?

Neurons in the spinal cord coordinate the micturition reflex by processing signals from the bladder and sending parasympathetic impulses back to the bladder to cause muscle contraction.

How does bladder stretching influence the micturition reflex?

When the urinary bladder stretches, it increases the frequency of action potentials sent to the sacral region of the spinal cord, activating parasympathetic neurons that cause the bladder's smooth muscle to contract.

What happens when parasympathetic neurons are activated in the micturition reflex?

When parasympathetic neurons are activated, they cause the smooth muscle in the bladder wall to contract, aiding in the process of urination.

How do sensory signals from the bladder reach the brain?

Sensory signals from the bladder stimulate ascending pathways to the pons and cerebrum, which triggers the conscious desire to urinate.

What prevents urination if it's not convenient at the moment?

If urination is not convenient, the brain sends impulses down the spinal cord to inhibit the micturition reflex, and somatic motor neurons keep the external urinary sphincter contracted, preventing urination.

What is the role of somatic motor neurons in the micturition reflex?

Somatic motor neurons carry impulses that keep the external urinary sphincter contracted, preventing urination until the brain signals that urination is desired.

How does the brain control the external urinary sphincter during urination?

When urination is desired, the brain decreases action potentials in the somatic motor neurons, causing the external urinary sphincter to relax, allowing urine to pass.

What pathways are involved in the conscious desire to urinate?

The sensory signals from the bladder travel through ascending pathways to the pons and cerebrum, which generate the conscious desire to urinate.

How does the brain influence the micturition reflex?

The brain can either inhibit or stimulate the micturition reflex. It inhibits the reflex by sending impulses to prevent bladder contraction or stimulates it by initiating bladder contraction and relaxing the external urinary sphincter when urination is desired.