Micturition Reflex.

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7 May 202001:38

Summary

TLDRThe 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.

Outlines

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🧠 Overview of the Micturition Reflex

The micturition reflex is a coordinated process involving signals traveling between the urinary bladder and the sacral region of the spinal cord. When the bladder stretches due to urine accumulation, action potentials are sent to the spinal cord, prompting a parasympathetic response that causes bladder wall contraction. Sensory signals also reach higher brain centers, creating the conscious urge to urinate. If urination is not timely, the brain inhibits the reflex and keeps the external urinary sphincter contracted via somatic motor neurons. When urination is desired, the brain stimulates the reflex and relaxes the sphincter for urine release.

Mindmap

Keywords

💡Micturition reflex

The micturition reflex is the physiological process that controls urination. It involves signals being sent from the urinary bladder to the sacral region of the spinal cord and back. This reflex is essential for coordinating the contraction of the bladder muscles and can be influenced by higher brain centers when urination is consciously controlled.

💡Urinary bladder

The urinary bladder is the organ that stores urine until the body is ready to excrete it. When the bladder becomes full and stretches, it sends signals to the spinal cord to initiate the micturition reflex, which ultimately causes the bladder to contract and expel urine.

💡Sacral region

The sacral region refers to the lower part of the spinal cord where nerve signals related to bladder control are processed. It plays a key role in receiving sensory input from the bladder and sending motor signals that trigger bladder contraction during the micturition reflex.

💡Parasympathetic neurons

Parasympathetic neurons are part of the autonomic nervous system that control involuntary functions. In the context of the micturition reflex, they carry signals from the spinal cord to the bladder, causing the smooth muscles of the bladder to contract and facilitate urination.

💡Smooth muscle

Smooth muscle refers to the involuntary muscle found in the walls of the urinary bladder. During the micturition reflex, these muscles contract in response to parasympathetic stimulation, helping to push urine out of the bladder.

💡Pons

The pons is a part of the brainstem that relays signals from the spinal cord to the higher brain centers, such as the cerebrum. In the context of the micturition reflex, it helps process the sensory information that signals the conscious desire to urinate when the bladder is full.

💡Cerebrum

The cerebrum is the largest part of the brain, responsible for higher brain functions like conscious thought. It processes signals from the bladder that create the awareness or desire to urinate, allowing a person to voluntarily control the timing of urination.

💡External urinary sphincter

The external urinary sphincter is a ring of skeletal muscle that controls the release of urine from the bladder. It can be consciously contracted or relaxed to either prevent or allow urination, making it an essential component for voluntary control over the micturition reflex.

💡Somatic motor neurons

Somatic motor neurons control voluntary muscle movement, including the contraction of the external urinary sphincter. When urination is not appropriate, these neurons keep the sphincter contracted. When it’s time to urinate, signals from the brain reduce action potentials in these neurons, allowing the sphincter to relax.

💡Action potentials

Action potentials are the electrical signals transmitted by neurons to communicate with muscles or other neurons. In the context of the micturition reflex, they are sent from the bladder to the spinal cord and from the spinal cord to the bladder, initiating muscle contraction. The frequency of these signals increases as the bladder becomes fuller.

Highlights

The micturition reflex involves impulses traveling from the urinary bladder to the sacral region of the spinal cord and back to the bladder.

This reflex is coordinated by neurons in the spinal cord and can be influenced by signals from the brain.

When the urinary bladder becomes stretched, there is an increase in the frequency of action potentials sent from the bladder to the sacral spinal cord.

Parasympathetic neurons from the sacral spinal cord to the bladder are activated, causing the bladder wall’s smooth muscle to contract.

Sensory signals sent to the sacral region also stimulate ascending pathways to the pons and cerebrum, leading to the conscious desire to urinate.

If urination is not convenient, the brain sends impulses down the spinal cord to inhibit the micturition reflex.

Somatic motor neurons carry impulses to keep the external urinary sphincter contracted, preventing urination.

When urination is desired, signals from the brain stimulate the micturition reflex.

The brain decreases action potentials in the somatic motor neurons, relaxing the external urinary sphincter.

The micturition reflex is a complex process that involves coordination between the spinal cord and the brain.

Increased bladder wall stretch leads to more frequent action potentials sent to the sacral spinal cord.

Parasympathetic neuron activation causes bladder contraction in response to these signals.

The conscious desire to urinate is triggered by sensory pathways reaching higher brain centers like the pons and cerebrum.

The brain plays a key role in deciding whether to urinate by sending inhibitory signals to the reflex arc.

Urination is ultimately controlled by the relaxation of the external urinary sphincter, regulated by somatic motor neurons.