By the cremasteric reflex, physicians mean the polysynaptic external reflex of the cremasteric muscle that moves the testes upward in response to stimuli. The reflex is exhaustible and may therefore be absent due to age physiology. Abnormal reflex behavior of the cremaster muscle, on the other hand, may also indicate spinal cord lesions.
What is the cremasteric reflex?
The cremasteric reflex is the term used by physicians to describe the polysynaptic extrinsic reflex of the cremasteric muscle that causes the testes to move upward in response to stimuli. The cremasteric reflex is an innate foreign reflex of the cremasteric muscle. Thus, unlike intrinsic reflexes, the monkey gate and the receptor of reflex movement in the cremaster muscle are not located in the same organ. Because extraneous reflexes involve multiple neurons connected in series, they are also called polysynaptic reflexes. Multiple subthreshold stimuli can add up to a suprathreshold stimulus in polysynaptic reflexes, unlike in monosynaptic reflex movements. Thus, the cremasteric reflex can be triggered more quickly than intrinsic reflexes, but is just as quickly fatigable. The reflex is therefore also assigned to the fatiguing reflexes and can come to a standstill in older age due to age physiology. The cremaster muscle consists of muscle fibers of the two lower abdominal muscles and accompanies the spermatic cord and the testicles of the male in a loop. The reflex of this muscle is controlled by the spinal cord and moves the testicles towards the trunk in response to certain stimuli. For this reason, the cremasteric muscle is also popularly called the testicular elevator muscle.
Function and purpose
The afferent fibers of the cremaster muscle are located in the ramus femoralis, a part of the genitofemoral nerve. Because the reflex is a foreign reflex and thus its afferents are separate from its efferents, the efferent fibers of the muscle are located separately from the afferents in the ramus genitalis to the genitofemoral nerve. Most reflexes of human skeletal muscle are so-called protective reflexes. Those such as the eyelid closure reflex protect the visual organ from injury, for example, by automatically closing the eyelid in response to certain visual and sometimes auditory stimuli. The cremasteric reflex is triggered neither visually nor auditorily, but is controlled by temperature stimuli. Thus, the thermoreceptors of the skin play a role in the cremasteric reflex. When they register suprathreshold cold in the area of the inner thigh, for example, they transmit this information to the spinal cord in the form of action potentials. The cremaster reflex is connected in the spinal cord segments L1 and L2. The response of the central nervous system reaches the cremaster muscle and causes it to contract. This contraction causes the testes to move upward. They are thus moved to a more protected area, presumably to ensure sperm production in the face of counterproductive environmental stimuli. Thus, the cremasteric reflex is thought to have a kind of thermoregulatory function that ensures reproduction. The motor protective reflexes have in common that they are connected via the spinal cord, because a connection via the brain would result in a too long reaction time. The reflex movements would thus occur too late to fulfill a protective function against certain stimulus perceptions. However, the connection between the cremasteric reflex and thermoregulatory functions as the sole cause is now disputed, since the reflex movements cause the testes to move upward not only in response to temperature stimuli, but also in response to extreme arousal. In animals, the cremasteric reflex is also physiological and in certain breeds even retracts the testes into the abdominal cavity.
Diseases and complaints
The reflexes of the body are studied primarily by neurology. There, pathologic reflexes, such as those from the Babinski group, and altered reflex behavior of physiologic reflexes can provide clues to central nervous damage. The cremasteric reflex can also provide such clues. Although the exhaustive reflex may also be absent due to age, it is used clinically to check the associated spinal cord segments. An absent cremasteric reflex at a young age may indicate spinal cord damage. The cause of such damage to the central nervous spinal cord may be, for example, spinal cord trauma following an accident. Spinal infarctions also cause spinal cord damage.Degenerative diseases such as ALS, for example, gradually break down the motor nervous system, whose main switching points are located in the spinal cord. The inflammatory autoimmune disease multiple sclerosis can also cause lesions in the spinal cord, which are caused by immunologically induced inflammation and often permanently damage the central nervous system. Less commonly, a tumor in the L1 and L2 segments is the cause of an absent cremasteric reflex. On the other hand, the cremasteric reflex can also fail completely independently of spinal cord lesions. This is the case, for example, with testicular torsion. In this phenomenon, the testis twists around the supplying pedicle of vessels, thus cutting off its own blood supply and innervation. Most often, the phenomenon is caused by sports activities. Testicular dystopias also affect the cremasteric reflex. However, the reflex tends not to remain absent due to them, but is particularly vivid. The congenital anomalies are also called testicular dystopias and are thus characterized by an abnormal position of the testicles. Effects on the cremasteric reflex are mainly shown by the so-called pendulous testis. This is a retractile testicular malposition. Although the testicles are in normal position in the scrotum on one or both sides, they temporarily move into high scrotal or inguinal position due to a particularly lively cremasteric reflex. If the patient does not suffer from the phenomenon and the testes lie in the scrotal position most of the time, the pendulous testis does not necessarily require therapy.