Flexor how to get rid of acne scars on face fast Reflex and the Withdrawal Reflexes – Medical Physiology

In the spinal or decerebrate animal, almost any type of cutaneous sensory stimulus from a limb how to get rid of acne scars on face fast is likely to cause the flexor muscles of the limb how to get rid of acne scars on face fast to contract, thereby withdrawing the limb from the stimulating object. This is called the flexor reflex.

In its classic form, the flexor reflex is elicited most powerfully by stimulation of how to get rid of acne scars on face fast pain endings, such as by a pinprick, heat, or a wound, for which reason it is also called a nociceptive reflex, or simply a pain reflex. Stimulation of touch receptors can also elicit a weaker and how to get rid of acne scars on face fast less prolonged flexor reflex.

If some part of the body other than one of how to get rid of acne scars on face fast the limbs is painfully stimulated, that part will similarly be withdrawn from the stimulus, but the reflex may not be confined to flexor muscles, even though it is basically the same type of reflex. Therefore, the many patterns of these reflexes in the different areas how to get rid of acne scars on face fast of the body are called withdrawal reflexes.

The pathways for eliciting the flexor reflex do not pass how to get rid of acne scars on face fast directly to the anterior motor neurons but instead pass first how to get rid of acne scars on face fast into the spinal cord interneuron pool of neurons and only how to get rid of acne scars on face fast secondarily to the motor neurons. The shortest possible circuit is a three- or four-neuron pathway; however, most of the signals of the reflex traverse many more how to get rid of acne scars on face fast neurons and involve the following basic types of circuits: (1) diverging circuits to spread the reflex to the necessary muscles how to get rid of acne scars on face fast for withdrawal; (2) circuits to inhibit the antagonist muscles, called reciprocal inhibition circuits; and (3) circuits to cause afterdischarge lasting many fractions of a second how to get rid of acne scars on face fast after the stimulus is over.

Figure 54-9 shows a typical myogram from a flexor muscle during how to get rid of acne scars on face fast a flexor reflex.Within a few milliseconds after a pain nerve begins to how to get rid of acne scars on face fast be stimulated, the flexor response appears. Then, in the next few seconds, the reflex begins to fatigue, which is characteristic of essentially all complex integrative reflexes of how to get rid of acne scars on face fast the spinal cord. Finally, after the stimulus is over, the contraction of the muscle returns toward the baseline, but because of afterdischarge, it takes many milliseconds for this to occur. The duration of afterdischarge depends on the intensity of the how to get rid of acne scars on face fast sensory stimulus that elicited the reflex; a weak tactile stimulus causes almost no afterdischarge, but after a strong pain stimulus, the afterdischarge may last for a second or more.

The afterdischarge that occurs in the flexor reflex almost certainly how to get rid of acne scars on face fast results from both types of repetitive discharge circuits discussed in how to get rid of acne scars on face fast chapter 46. Electro-physiologic studies indicate that immediate afterdischarge, lasting for about 6 to 8 milliseconds, results from repetitive firing of the excited interneurons themselves. Also, prolonged afterdischarge occurs after strong pain stimuli, almost certainly resulting from recurrent pathways that initiate oscillation in how to get rid of acne scars on face fast reverberating interneuron circuits. These, in turn, transmit impulses to the anterior motor neurons, sometimes for several seconds after the incoming sensory signal is how to get rid of acne scars on face fast over.

Thus, the flexor reflex is appropriately organized to withdraw a pained how to get rid of acne scars on face fast or otherwise irritated part of the body from a stimulus. Further, because of afterdischarge, the reflex can hold the irritated part away from the how to get rid of acne scars on face fast stimulus for 0.1 to 3 seconds after the irritation is over. During this time, other reflexes and actions of the central nervous system can how to get rid of acne scars on face fast move the entire body away from the painful stimulus.

Pattern of withdrawal. The pattern of withdrawal that results when the flexor reflex how to get rid of acne scars on face fast is elicited depends on which sensory nerve is stimulated. Thus, a pain stimulus on the inward side of the arm how to get rid of acne scars on face fast elicits not only contraction of the flexor muscles of the how to get rid of acne scars on face fast arm but also contraction of abductor muscles to pull the how to get rid of acne scars on face fast arm outward. In other words, the integrative centers of the cord cause those muscles to how to get rid of acne scars on face fast contract that can most effectively remove the pained part of how to get rid of acne scars on face fast the body away from the object causing the pain. Although this principle, called the principle of "local sign," applies to any part of the body, it is especially applicable to the limbs because of their how to get rid of acne scars on face fast highly developed flexor reflexes.

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