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The rate at which fluid is filtered across vascular endothelium (transendothelial filtration) is determined by the sum of two outward forces, capillary pressure and colloid osmotic pressure beneath the endothelial glycocalyx (), and two absorptive forces, plasma protein osmotic pressure and interstitial pressure (). The Starling equation is the ...
The action potential travels from one location in the cell to another, but ion flow across the membrane occurs only at the nodes of Ranvier. As a result, the action potential signal jumps along the axon, from node to node, rather than propagating smoothly, as they do in axons that lack a myelin sheath.
Through the processes of vasoconstriction and vasodilation, these cells can actively control the rate of blood flow by means of: Contraction of cellular processes that encircle capillaries as in pericytes, which possess contractile proteins such as α-actin , tropomyosin , and myosin enabling them to contract and relax.
In non-excitable cells, and in excitable cells in their baseline states, the membrane potential is held at a relatively stable value, called the resting potential. For neurons, resting potential is defined as ranging from –80 to –70 millivolts; that is, the interior of a cell has a negative baseline voltage of a bit less than one-tenth of a ...
The two types of aquaporins expressed in the CNS are aquaporin-1, which is expressed by specialized epithelial cells of the choroid plexus, and aquaporin-4 (AQP4), which is expressed by astrocytes. [12] [13] Aquaporin-4 expression in astrocytes is highly polarized to the endfoot processes ensheathing the cerebral vasculature. Up to 50% of the ...
Erythrocyte aggregation is the reversible clumping of red blood cells (RBCs) under low shear forces or at stasis. Stacked red blood cells flow across drying slide. Erythrocytes aggregate in a special way, forming rouleaux. Rouleaux are stacks of erythrocytes which form because of the unique discoid shape of the cells in vertebrate body. The ...
Vascular resistance occurs when the vessels away from the heart oppose the flow of blood. Resistance is an accumulation of three different factors: blood viscosity, blood vessel length and vessel radius. [30] Blood viscosity is the thickness of the blood and its resistance to flow as a result of the different components of the blood.
A Reynolds number of less than 2300 is laminar fluid flow, which is characterized by constant flow motion, whereas a value of over 4000, is represented as turbulent flow. [16] Due to its smaller radius and lowest velocity compared to other vessels, the Reynolds number at the capillaries is very low, resulting in laminar instead of turbulent flow.