Ferguson reflex
Encyclopedia
The Ferguson reflex is an example of positive feedback
and the female body's response to pressure application in the cervix
or vaginal walls
.
Upon application of pressure, oxytocin
is released and uterine contractions are stimulated (which will in turn increase oxytocin production, and hence, increase contractions even more), until the baby is delivered. The Ferguson reflex also occurs in animals.
Sensory information regarding mechanical stretch of the cervix is carried in a sensory neuron, which synapses in the dorsal horn before ascending to the brain in the anterolateral columns (ipsi and contralateral routes). Via the median forebrain bundle, the efferent reaches the PVN and SON
of the hypothalamus. The posterior pituitary releases oxytocin due to increased firing in the hypothalamo-hypophyseal tract
. Oxytocin acts on the myometrium
, on receptors which have been upregulated by an increasing oestrogen-progesterone ration. This causes myometrial contraction and further positive feedback on the reflex.
Positive feedback
Positive feedback is a process in which the effects of a small disturbance on a system include an increase in the magnitude of the perturbation. That is, A produces more of B which in turn produces more of A. In contrast, a system that responds to a perturbation in a way that reduces its effect is...
and the female body's response to pressure application in the cervix
Cervix
The cervix is the lower, narrow portion of the uterus where it joins with the top end of the vagina. It is cylindrical or conical in shape and protrudes through the upper anterior vaginal wall...
or vaginal walls
Vagina
The vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...
.
Upon application of pressure, oxytocin
Oxytocin
Oxytocin is a mammalian hormone that acts primarily as a neuromodulator in the brain.Oxytocin is best known for its roles in sexual reproduction, in particular during and after childbirth...
is released and uterine contractions are stimulated (which will in turn increase oxytocin production, and hence, increase contractions even more), until the baby is delivered. The Ferguson reflex also occurs in animals.
Sensory information regarding mechanical stretch of the cervix is carried in a sensory neuron, which synapses in the dorsal horn before ascending to the brain in the anterolateral columns (ipsi and contralateral routes). Via the median forebrain bundle, the efferent reaches the PVN and SON
Supraoptic nucleus
The supraoptic nucleus is a nucleus of magnocellular neurosecretory cells in the hypothalamus of the mammalian brain. The nucleus is situated at the base of the brain, adjacent to the optic chiasm...
of the hypothalamus. The posterior pituitary releases oxytocin due to increased firing in the hypothalamo-hypophyseal tract
Hypophyseal portal system
The hypophyseal portal system is the system of blood vessels that link the hypothalamus and the anterior pituitary in the brain.It allows endocrine communication between the two structures. It is part of the hypothalamic-pituitary-adrenal axis. The anterior pituitary receives releasing and...
. Oxytocin acts on the myometrium
Myometrium
The myometrium is the middle layer of the uterine wall, consisting mainly of uterine smooth muscle cells , but also of supporting stromal and vascular tissue...
, on receptors which have been upregulated by an increasing oestrogen-progesterone ration. This causes myometrial contraction and further positive feedback on the reflex.