Hypoxia systems

Enhanced automaticity occurs in hypoxia, hypokalemia, hypercarbia, excessive sympathetic nervous system stimulation, or high concentrations of catecholamines. These conditions may lead to arrhythmias. Decreased automaticity may also lead to production of arrhythmias by enhancing ectopic activity in latent pacemakers (ectopic foci) or by altering conductivity and refractoriness in conduction pathways of myocardium. 

The nervous system is vulnerable to attack from several directions. Neurons do not divide, and, therefore, death of a neuron always causes a permanent loss of a cell. The brain has a high demand for oxy gen. Lack of oxygen (hypoxia) rapidly causes brain damage. This manifests itself both on neurons and oligodendroglial cells. Anoxic brain damage may result from acute carbon monoxide, cyanide, and hydrogen sulfide poisonings. Carbon monoxide may also be formed in situ in the metabolism of dichloromethylene. 

State of deviation of plasma pH (systemic acidosis) or tissue extracellular pH (tissue or local acidosis) from normal (ca. pH 7.4) towards lower values. Deviation of 0.1 pH units is significant. Systemic acidosis can be caused by lung or kidney failure. Local acidosis can be the consequence of injury, inflammation, or tumor growth, due to disruption of blood supply. Local acidosis is normally associated with hypoxia. 

Hyperactivity of the orexin system, e.g. triggered by energy depletion, metabolic failure, hypoglycemia or hypoxia, in the context of starvation, sleep derivation, and stress, may predispose to addiction and... 

TDAG8 appears restricted to the immune system. As tissue inflammation is usually followed by local hypoxia and acidosis, the pH-sensing property of TDAG8 appeared of particular interest in this context. Unexpectedly, however, the phenotype of mice... 

Inhalant intoxication dehrium can occur as a consequence of disturbances in dopaminergic, glutamatergic, and GABAergic neu to transmission secondary to acute, high-level exposure to psychoactive ingredients in solvents such as toluene, trichloroethane, and trichloroethylene. Systemic effects of solvent inhalation such as cerebral hypoxia and/or metabolic acidosis may also be involved (Rosenberg 1982). Under these circumstances, inhalant intoxication dehrium develops over a short period of time (usually hours to days) and tends to fluctuate during the course of the day. Usually, the delirium resolves as the intoxication ends or within a few hours after cessation of use. 

Renal Effects. Acute nephrosis has been reported in humans after acute, lethal intoxication (Fazekas 1971) by methyl parathion (Wofatox). This may be a secondary effect of hypoxia related to the neurologic effects of methyl parathion on vascular smooth muscle and on the electrical conduction system of the heart. It could also be related to therapeutic efforts. 

Deprived of their substrate in severe or prolonged hypoxia, some ATPase-driven systems, including ion pumps, may become impaired. Further, with the decrease in the availability of O2 as its terminal electron acceptor, the mitochondrial transport chain becomes increasingly unable to accept reducing equivalents from cellular metabolic processes. Hence the intracellular pH falls, subjecting the cell as a whole to a reductive stress and favouring those enzyme systems with acid pH optima. 

Hypoxia, hypercarbia, pain, central nervous system... 

Automaticity of cardiac fibers is controlled in part by activity of the sympathetic and parasympathetic nervous systems. Enhanced activity of the sympathetic nervous system may result in increased automaticity of the SA node or other automatic cardiac fibers. Enhanced activity of the parasympathetic nervous system tends to suppress automaticity conversely, inhibition of activity of the parasympathetic nervous system increases automaticity. Other factors may lead to abnormal increases in automaticity of extra-SA nodal tissues, including hypoxia, atrial or ventricular stretch [as might occur following long-standing hypertension or after the development of heart failure (HF)], and electrolyte abnormalities such as hypokalemia or hypomagnesemia. 

The principal function of the circulatory system is to supply oxygen and vital metabolic substrates to cells throughout the body, as well as removal of metabolic waste products. Circulatory shock is a life-threatening condition whereby this principal function is compromised. When circulatory shock is caused by a severe loss of blood volume or body water it is called hypovolemic shock, the focus of this chapter. Regardless of etiology, the most distinctive manifestations of hypovolemic shock are arterial hypotension and metabolic acidosis. Metabolic acidosis is a consequence of an accumulation of lactic acid resulting from tissue hypoxia and anaerobic... 

Isolated seizures that are not epilepsy can be caused by stroke, central nervous system trauma, central nervous system infections, metabolic disturbances (e.g., hyponatremia and hypoglycemia), and hypoxia. If these underlying causes of seizures are not corrected, they may lead to the development of recurrent seizures I or epilepsy. Medications can also cause seizures. Some drugs that are commonly associated with seizures include tramadol, bupropion, theophylline, some antidepressants, some antipsy-chotics, amphetamines, cocaine, imipenem, lithium, excessive doses of penicillins or cephalosporins, and sympathomimetics or stimulants. 

Although the kidneys are not considered endocrine glands per se, they are involved in hormone production. Erythropoietin is a peptide hormone that stimulates red blood cell production in bone marrow. Its primary source is the kidneys. Erythropoietin is secreted in response to renal hypoxia. Chronic renal disease may impair the secretion of erythropoietin, leading to development of anemia. The kidneys also produce enzymes. The enzyme renin is part of the renin-angiotensin-aldosterone system. As will be discussed, these substances play an important role in the regulation of plasma volume and therefore blood pressure. Other renal enzymes are needed for the conversion of vitamin D into its active form, 1,25-d i hyd ro xyv itamin D3, which is involved with calcium balance. 

Hellstrand That is what I am getting at. There are a lot of phase shifts in this system. One observation we have made is that under hypoxia we see a decrease in amplitude but an increase in frequency of the waves. We are trying to model a case where this would account for reduction of force simply on the basis of non-linearity of the [Ca2+] versus myosin phosphorylation versus force reactions. It seems intuitively that this could explain why there can be a reduction in force although there is no reduction in the overall level of global Ca2+. Is amplitude modulation something that people have seen ... 

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