Blood Pressure, Thermoreceptors and Homeostasis

• Ventricular contraction in vertebrate animals causes the ventricles to reduce in volume, forcing blood into major arteries.
• This process is pulsatile, reflecting heart contraction rate and strength.
• Each pulse of blood exerts physical force on blood vessel walls, measured as blood pressure.
• Arterial blood pressure changes can cause slight changes in organ volume, recorded by a plethysmograph.
• Plethysmograph recordings are used to study arterial blood pressure and local blood flow, which is organ or tissue-specific.
• Homeostatic mechanisms and external factors like temperature or body position can influence arterial blood pressure and local blood flow.
• Dermal sensory receptors in mammals detect skin temperature changes.
• Activated thermoreceptors send neuronal signals to the hypothalamus.
• Skin thermoreceptor information is integrated into a homeostatic mechanism to maintain stable body temperature in mammals.
• Physiological changes induced by this mechanism include alterations in local blood flow within the skin and other organs.
• Local blood flow is the volume of blood traveling through vessels supplying blood to tissue.
• Local blood flow can be increased or decreased by vasoconstriction and vasodilation, respectively.
• Changes in local blood flow due to vasoconstriction or vasodilation result in slight tissue volume changes.
• These changes in volume can be detected utilizing a plethysmograph.
• A pulse plethysmograph attached to a finger tip can record local volume changes from blood flow in finger vessels.
• The pulse wave recorded in the plethysmograph will provide information related to finger volume and heart (pulse) rate.
• Two experiments will be conducted: one to test if heating and cooling of the forearm induces vasodilation and vasoconstriction in finger arteries, and another to quantify gravity's influence on blood flow through the finger.

Ventricular contraction forces blood into arteries, creating blood pressure. Plethysmographs measure arterial blood pressure and local blood flow. Dermal thermoreceptors detect skin temperature changes, triggering homeostatic mechanisms to maintain stable body temperature.