The mechanoreceptors of the sense of touch register touches by binding to pressure and strain stimuli. Mechanoreceptors and their subspecies of stretch receptors reside in the skin, where they are responsible for the exteroception of stimuli from the environment. The receptors can also fulfill interoceptive tasks and thus bind to stretch and pressure stimuli from the own body. Stretching receptors are therefore in many organs of man. They are found mainly in organs in which measurements of tissue tension are necessary, such as in the blood vessels or the lungs.
Stretching receptors also occur in the cervix and vagina of the woman. These sensory cells are especially relevant for the process of birth. They trigger the so-called Ferguson reflex as soon as they register the pressure of the descending child inside.
The reflex was first described by the Canadian Ferguson in the 20th century. A reflex is always an unconscious and automatic body reaction to a certain stimulus. In the case of the Ferguson reflex, the stretch stimulus on the extensor receptors in the vagina and cervix triggers the release of oxytocin. It is a hormone that causes contractions and additionally influences social interaction.
Stretching receptors are mechanoreceptors that respond to stimuli of elongation and tissue elongation by depolarization. These stretch receptors are located, among other things, in the uterus and the vagina, where they perceive the pressure of the child during the birth process. The sensory cells bind to the mechanical pressure stimuli and translate these stimuli into the language of the central nervous system.
As a bioelectric excitation, the stimulus travels across the spinal cord into the woman's midbrain. In a reflex response to the pressure stimuli, the diencephalon triggers the release of the hormone oxytocin. The uterus carries receptors for this hormone, to which the hormone binds and thus triggers a reflex response. This reflex is known as Ferguson reflex and corresponds to a so-called self-reflex. The effectors and affectors of the reflex circle are thus in the same organ, namely in the uterus.
The reflex initiates contractions through oxytocin release. After the release of oxytocin, the uterine muscles are stimulated to contract. Finally, these contractions initiate childbirth. In addition, the initiation of contractions by oxytocin increases the pressure on the receptors so that the Ferguson reflex becomes a loop, repeatedly leading to oxytocin release until the child is born. The sensory information on the mechanical dilation of the cervix thus repeatedly migrates into the dissipating neurons of the hypothalamus and the oxytocin levels in the mother's blood continue to increase.
The hormone oxytocin, in addition to the Ferguson reflex, also plays a crucial role in breastfeeding. For example, the milk ejection reflex is controlled by the oxytocin concentration in the mother's blood.
During and after birth, the hormone also causes a decrease in cortisol. This effect improves the mood of the mother, the emotional attachment to the child is increased and the perceived birth stress is reduced.
In obstetrics, it may be necessary to artificially induce a woman's contractions, such as when the Ferguson reflex fails. This artificial induction of contractions usually consists in the administration of oxytocin. In this way, the Ferguson reflex is artificially imitated. Its result and thus the hormone concentration in the blood of the mother are imitated from the outside, until the contractions are initiated.
The question of how peridural anesthesia affects the distribution of oxytocin at birth is controversially discussed. Peridural anesthesia is a central conduction anesthesia that is delivered to the spine via a cannula or a catheter. Usually a local anesthetic or an opioid analgesic is administered. With the help of peridural anesthesia, the woman experiences less pain at birth, as the pain sensation of the nerves in the epidural space of the spine is eliminated. Since the Ferguson reflex is also triggered by the nerves of the spine, an impairment of the reflex under peridural anesthesia is close. Therefore, it is suspected that peridural anesthesia has a negative effect on the concentration of oxytocin in the blood of the mother. A low oxytocin concentration not only causes a delay in labor, but also a high cortisol level. This could increase the birth stress for the mother under peridural anesthesia. So far, medicine has not agreed on the links between epidural anesthesia, Ferguson reflex and birth stress. However, the negative contexts described are conceivable.
In addition, the Ferguson reflex has negative effects on traumatic or other types of injuries to the reflex nerves in the spinal cord. For example, neurological disorders such as multiple sclerosis can cause inflammatory lesions in the reflex-mediating pathways that slow down or even eliminate the nerves. Such relationships can sometimes cause complications at birth, requiring an artificial induction of labor or caesarean section.Tags: