Passive movement

Passive movement detection senses radiated heat, such as that from a human body. These units are also sensitive to heat emitted by radiator, convection heaters and direct sunlight, so careful siting is required. 

Rigidity is muscular stiffness throughout the range of passive movement in a limb segment. Cogwheel rigidity, which is typical for parkinsonism, means that tremor is superimposed on muscle stiffness. 

Molecules and ions are in constant motion and the velocity of their motion is proportional to their temperature. This passive movement of molecules and ions from one place to another is referred to as diffusion. When a molecule is unevenly distributed across a permeable membrane with a higher concentration on one side and a lower concentration on the opposite side, there is said to be a concentration gradient or a concentration difference. Although all of the molecules are in motion, the tendency is for a greater number of molecules to move from the area of high concentration toward the area of low concentration. This uneven movement of molecules is referred to as net... 

Proprioceptors originating in muscles and joints of the exercising limbs provide substantial input to the medullary respiratory center. In fact, even passive movement of the limbs causes an increase in ventilation. Therefore, the mechanical aspects of exercise also contribute to the ventilatory response. The increased metabolism associated with exercise increases body temperature, which further contributes to the increase in ventilation during exercise. (Not surprisingly, ventilation is also enhanced in response to a fever.) Exercise is associated with a mass sympathetic discharge. As a result, epinephrine release from the adrenal medulla is markedly increased. Epinephrine is believed to stimulate ventilation. 

When the action potential reaches the synaptic bouton, depolarisation triggers the opening of voltage-operated calcium channels in the membrane (Figure 2.5). The concentration gradient for Ca2+ favours the passive movement of this ion into the neuron. The subsequent rise in cytoplasmic Ca2+ ion concentration stimulates the release of neurotransmitter into the synaptic cleft, which diffuses across this narrow gap and binds to receptors located on the postsynaptic neuronal membrane (Figure 2.5). 

Soergel, K. H., Whalen, G. E., Harris, f. A., Passive movement of water and sodium across the human small intestinal mucosa, J. Appl. 

The liver secretes about 1 L of bile daily. Bile flow and composition depend on the secretory activity of the hepatic cells that line the biliary canaliculi. As the bile flows through the biliary system of ducts, its composition can be modified in the ductules and ducts by the processes of reabsorption and secretion, especially of electrolytes and water. For example, osmotically active compounds, including bile acids, transported into the bile promote the passive movement of fluid into the duct lumen. In the gallbladder, composition of the bile is modified further through reabsorptive processes. 

In humans, tizanidine reduces pathologically increased muscle tone, including resistance to passive movements and alleviates painful spasms and clonus. 

A number of suggestions have been made that calcium may be transported because it is coupled to the movement of other ions or because it moves passively down an electrochemical gradient established by the movement of some other ions600. Thus, a sodium-induced potential has been found which was sufficient to account for the passive movement of calcium into the shell gland of the domestic fowl during egg shell formation. In the mollusc, the shell side of the mantle is normally positive relative to blood and a potential of this type would, of course, tend to move calcium away from the extrapallial fluid. A potential of this orientation could be produced by the movement of an anion into the animal (mollusc) and the low chloride concentration of the extrapallial fluid could be accounted for on this basis. 

HDL may be taken up in the liver by receptor-mediated endocytosis, but at least some of the cholesterol in HDL is delivered to other tissues by a novel mechanism. HDL can bind to plasma membrane receptor proteins called SR-BI in hepatic and steroidogenic tissues such as the adrenal gland. These receptors mediate not endocytosis but a partial and selective transfer of cholesterol and other lipids in HDL into the cell. Depleted HDL then dissociates to recirculate in the bloodstream and extract more lipids from chylomicron and VLDL remnants. Depleted HDL can also pick up cholesterol stored in extrahepatic tissues and carry it to the liver, in reverse cholesterol transport pathways (Fig. 21-40). In one reverse transport path, interaction of nascent HDL with SR-BI receptors in cholesterol-rich cells triggers passive movement of cholesterol from the cell surface into HDL, which then carries it back to the liver. In a second pathway, apoA-I in depleted HDL in-... 

The akinesia or bradykinesia is characterized by a poverty of spontaneous movements and slowness in initiation of movements. Rigidity or increased muscle tone occurs in response to passive movements. The loss of normal postural reflexes is a disorder of postural fixation and equilibrium. 

Parkinsonism is a clinical syndrome that comprises four main features bradykinesia (a slowness and poverty of movement), muscular rigidity (increased resistance of muscles to passive movement), resting tremor, which usually disappears during voluntary movement, and abnormalities in posture and gait. 

Beament, J. W.L. (1964). The active transport and passive movement of water in insects. Adv. Insect Physiol., 2, 67-129. 

Unlike enzymes or G protein-coupled receptors, the consequence of ion channel activation does not involve the depletion of a substrate or the generation of a product. Rather, when an ion channel opens (or activates), it permits the passive movement of Na+, Ca2+, K+, or CF ions down their electrochemical gradients. By regulating the flow of ionic charges across membranes, activated ion... 

Smith M. Case report akathisia abolished by passive movement. Acta Psychiatr Scand 1998 97(2) 168-9. 

Figure 3-7. Passive movements of K+, Na and Cl- across a membrane can account for the electrical potential difference across that membrane, as predicted by the Goldman equation (Eq. 3.20). Usually K+ fluxes make the largest contribution to Em-...

The initiation of an electrogenic process causes an adjustment of the passive ionic fluxes across the membrane. In particular, the net charge actively brought in is soon electrically compensated by appropriate passive movements of that ion and other ions into or out of the cell. The actual electrical potential difference across the membrane then results from the diffusion potential caused by these new passive fluxes plus a steady-state contribution from the electrogenic process involving the active transport of various charged species. We can represent the electrical potential difference generated by the active transport of species/, atj, by... 

Neuroleptic-induced parkinsonian side effects are characterized by the triad of tremor, muscle stiffness, and slowness of motion. For the most part, these physical indicators are relatively easy to identify. The tremor, which is somewhat coarse and may include classic "pill-rolling," is worse at rest, and is distinguishable from the fine, intention tremor of lithium. Muscle stiffness or rigidity is notable for the increased resistance to passive movement ("cogwheeling"). 

Convection (also known as advection) is a more passive movement of biological and chemical materials, in that the agent moves with the water or air within the soil. Onedimensional solute flow rates in the z dimension can be represented by... 

Individual movement by walking was modeled as a jump from 1 cell to a randomly selected neighboring cell at a time set by the (probabilistic) residence time. The probability density function was obtained from a simulation of a random walk process with parameters derived from experimental work (Englund and Hamback 2004). The model incorporated passive movement downstream by implying that 1% of the movement to other cells was long-distance movement (drift) in a downstream direction. Drift distance was incorporated as an exponential distribution, with an assumed average of 10 m. 

Na extrusion from plant cells is powered by the operation of the plasma membrane H -ATPase generating an electrochemical gradient that allows plasma membrane Na /H antiporters to couple the passive movement of inside the cells, along its electrochemical potential, to the active extrusion of Na [21]. Recently, AtSOSl from Arahidopsis thaliana has been shown to encode a plasma membrane Na /H antiport with significant sequence similarity to plasma membrane Na /H antiporters from bacteria and fungi [32]. The overexpression of SOSl improved the salt tolerance of Aro-hidopsis, demonstrating that improved salt tolerance can be attained by limiting Na accumulation in plant cells [33] (Table 10.1). 

Spasticity is a common symptom in multiple sclerosis. It is defined as an increase in muscle tone characterized by initial resistance to passive movement followed by sudden relaxation. Spasticity can be treated with a number of drugs. 

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