Gauer-Henry reflex
The Gauer-Henry reflex (after Otto Gauer (1909–1979) and James Paget Henry (1914–1996)) describes a mechanism in medicine that regulates blood volume by stretching the heart tissue.
Working principle
Baroreceptors in the heart, especially in the right atrium (type B atrial receptors), are stretched as the filling volume increases. Mediated by afferents of the vagus nerve , less antidiuretic hormone (ADH) is released from the pituitary gland . ADH causes increased water reabsorption in the kidneys by incorporating aquaporins into the luminal membrane in the distal tubule and especially in the collecting tube , through which water diffuses from the urine into the renal medulla and from there into the blood. The blood volume is reduced by the decreased ADH release. As a result, the B-sensors are also stretched less, which means that the inhibition of ADH release decreases again.
The atrial natriuretic peptide (ANP) works in a similar way (but has an opposite effect to ADH), which is released by the heart muscle cells themselves when they are stretched and which increases sodium excretion, which results in increased water excretion.
These two mechanisms are described in medicine with the catchy phrase "atrium full - bladder full": Increased filling of the atrium results in increased bladder filling.
An increased cardiac output leads to an increased glomerular filtration rate with increased primary urine formation . Now water is increased by ADH and decreased tubularly reabsorbed by ANP. This increases or decreases the blood volume with the opposite effect on urine production .
Examples
The Gauer-Henry reflex can be observed, for example, when taking a bath: when you are in the water you have to urinate. The water pressure causes the blood, which is normally “drawn” into the veins of the leg and abdomen by gravity, to circulate throughout the system, which is equivalent to a central increase in pressure.
During the countdown , astronauts in the space shuttle and other space shuttles are sometimes lashed to their recumbent seats for several hours. This posture causes blood to flow from the legs to the upper body. Since going to the toilet is not an option in this situation, the astronauts wear special diapers during the start-up procedure . In weightlessness, the same mechanism works as when you are in water.
In addition, the Gauer-Henry reflex can also be triggered by increased drinking, as this increases the blood volume, which irritates the atrial myocytes and baroreceptors, especially in the right atrium, and thus leads to a reduced release of ADH and increased release of ANP.
literature
- Schmidt, Lang, Thews: Human Physiology . 29th edition, Springer 2005
Individual evidence
- ↑ International Space Hall of Fame
- ^ JP Henry, OH. Gauer, JL. Reeves: Evidence of the atrial location of receptors influencing urine flow . In: Circ Res . , 1956 Jan, 4 (1), pp. 85-90, PMID 13277115 .