A Review of Classic Physiological Systems
Len Wisneski in The Scientific Basis of Integrative Health, 2017
Corticosteroids convert fat and protein to useable energy for the stress experience. The blood flow is diverted from organs that are not essential to the stress response and directed toward the organs and systems that are critical to the response, providing them with the glucose, fatty acids, and oxygen necessary for effective action. This event causes the hormones related to such nonessential functions as reproduction, growth, and appetite to be inhibited. Simultaneously, endorphins are released, which reduce the experience of pain during trauma. Ideally, the stress stimulus is not harmful and is a short-term event. In such situations, the circulating cortisol inhibits further pituitary release of ACTH. The situation resolves, and the body goes back to normal. It is as if the cortisol is set at a certain thermostatic temperature, and when that temperature is reached, it switches off. However, in circumstances involving long-term stress, this feedback loop is overridden by higher cortical centers, and the stress reaction continues, which can be devastating to long-term health.
Nature of Flow of a Liquid
Wilmer W Nichols, Michael F O'Rourke, Elazer R Edelman, Charalambos Vlachopoulos in McDonald's Blood Flow in Arteries, 2022
Hemodynamic factors that tend to affect the magnitude of blood flow disturbances include velocity, viscosity and density of the blood. For example, an increased blood velocity or a reduction of blood viscosity would increase the intensity of turbulence. The pulsatile nature of blood flow may also lead to flow instability. The effects of unsteady flow on the transition from laminar to turbulent flow have been evaluated by several investigators (Hale et al., 1955; Parker, 1977), but an understanding of the stability of unsteady flow, even in tube flow, is still poor (Parker, 1977; Chahed et al., 1991). Lesions that produce a partial obstruction to flow or an irregularity of the vessel wall would augment flow disturbances. The normal aortic and pulmonary valves also cause flow disturbances because the valvular leaflets act as natural projections into the stream of flow (Sabbah and Stein, 1979). Fluttering of the free margin of the leaflets may also contribute to the disturbances.
Drugs affecting the autonomic nervous system
Bev-Lorraine True, Robert H. Dreisbach in Dreisbach’s HANDBOOK of POISONING, 2001
Ergotism includes two types of manifestations, which may occur together or separately. Those resulting from contraction of blood vessels and reduced circulation include numbness and coldness of the extremities, tingling, pain in the chest, heart valve lesions, alopecia, oliguria from reduced renal blood flow, and gangrene of the fingers and toes. Hypercoagulability has also been reported.Those resulting from nervous system disturbances include vomiting, diarrhea, headache, tremors, contractions of the facial muscles, and convulsions.Methysergide, cabergoline, and pergolide have caused retroperitoneal, pericardial, and pleural fibrosis. Cabergoline has caused interstitial pneumonitis.
Topical negative-pressure wound therapy: emerging devices and techniques
Published in Expert Review of Medical Devices, 2020
Raymund E. Horch, Ingo Ludolph, Wibke Müller-Seubert, Katharina Zetzmann, Theresa Hauck, Andreas Arkudas, Alexander Geierlehner
The porous interface material (foam) with a pore diameter of 400 to 600 µm causes microdeformation when wound tissue gets drawn up into those pores resulting in tissue strain at a microscopic level (‘microstrain’). Changes in cell shape and structure modulate cellular behavior such as cell proliferation in wounds during NPWT [26,27,38]. Although the exact cell-signaling mechanism of mechanotransduction remains unclear, numerous studies showed decreasing blood flow close to the wound surface but an increased flow more distal of the wound bed [39,40]. Wound perfusion during NPWT depends on various factors including the amount of negative pressure and the manner in which the pressure is applied to the wound (continuous, intermittent or variable pressure) [41,42]. Full-thickness wounds in swine showed improved granulation tissue formation with varying levels of sub-atmospheric pressure [43]. Constant changes of perfusion seem to be an appropriate stimulus for the release of numerous growth factors, increasing levels of certain cytokines, and the production of extracellular matrix components, which in turn stimulates angiogenesis, and the formation of granulation tissue (Figure 1) [12,44–47]. Blood flow, as supplier of oxygen and nutrients, remains crucial for tissue regeneration [48]. However, in chronic wounds, it rather seems to be a mismatch of various pro- and anti-inflammatory cytokine concentrations causing wound chronification. NPWT is discussed to help establish an equilibrium between pro- and anti-inflammatory cytokines and thus promote the wound healing process [49,50].
Alzheimer’s dementia: pathogenesis and impact of cardiovascular risk factors on cognitive decline
Published in Postgraduate Medicine, 2019
Pitchaya Wanleenuwat, Piotr Iwanowski, Wojciech Kozubski
Adequate blood flow to the brain is essential for the delivery of nutrients, oxygen, and glucose for neuronal metabolism. Two of the known causes of cognitive deterioration in Alzheimer’s Disease patients are normal aging and any other existing conditions that may be influencing decreased cerebral perfusion. Additive effects of these two conditions may reach a certain point at which there is ‘neuronal crisis’ due to lack of ability of ATP synthesis known as the critically attained threshold of cerebral hypoperfusion (CATCH). Reaching this threshold means that problems such as increased oxidative stress, decreased neuronal signaling ability and neurodegeneration, including neuronal death, will gradually arise, especially in areas most susceptible to ischemic damage such as the pyramidal neurons of the hippocampus [11,12].
Contribution of Human Trophoblast Progenitor Cells to Neurogenesis in Rat Focal Cerebral Ischemia Model
Published in Brain Injury, 2021
Kerem Yanar, Muge Molbay, Eylem Özaydın-Goksu, Gozde Unek, Emre Cetindağ, Ali Unal, Emin Turkay Korgun
A condition where blood flow drops below a critical threshold in the entire brain or an area is called cerebral ischemia. Usually, in this case, damage occurs in the ischemic area. In ischemic injury, numerous cells are damaged, such as neurons, astrocytes, and oligodendrocytes. Cerebrovascular disease defined as stroke is one of the diseases leading to serious mortality and morbidity (1). According to the World Health Organization, 15 million people suffer strokes worldwide each year. Of these, 5 million dies, and another 5 million are permanently disabled. There is one stroke in 19 deaths in the USA, which means approximately 795,000 deaths (2). Eighty-seven percent of these stroke cases are ischemic. Stroke affects people of all ages, including infants. A stroke occurs in 1 in 4000 live births (3). The risk of stroke in babies is highest in the perinatal period and is one of the top 10 causes of child mortality (4). The average cerebral blood flow is 50–55 mL/100 g/min. If blood flow decreases under 30 mL/100 g/min, neurologic symptoms occur. Under 10 mL/100 g/min, membrane permeability is impaired, leading to ischemia. Ischemic neuronal deaths usually occur days after ischemia, and this is called deferred neuron death. This delay in neuronal death varies according to the area and the duration of ischemia. In some cases, deferred neuronal death can take days or weeks, while in others it can take several hours or less (5).
Related Knowledge Centers
- Autoregulation
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- Circulatory System
- Blood Vessel
- Homeostasis
- Nutrient
- Hormone