Tag Info

Hot answers tagged

4

To answer your questions, one needs to address certain issues one at a time. Veins do have valves, but they function to hold blood from settling in the legs. When you flex muscles, the blood flows towards the heart. Valve failure occurs when people stand (especially if they stand relatively still) for long periods of time every day over many years, dilating ...


3

Yes, this is the effect of metabolizing ethanol and also the reason why excess amount of ethanol can lead to hypoglycemia. Ethanol is oxidized by the alcohol dehydrogenase to acete aldehyde. This reaction needs consumes one molecule of NAD+ per molecule ethanol oxidized: Ethanol + NAD+ <=> Acetaldehyde + NADH + H+ Acetaldehyde is oxidized by the ...


3

It's a general phenomenon that the time scale correlates with the size scale of complex systems. Energy consumption is the main concern dealing with the speed for biological organizations. In the absolute sense, a turtle has a higher speed than a small bug. But based on their sizes, the bug seems much quicker and faster. So we need to normalize the speed ...


3

Check out Van Der Pol (chaotic) oscillator. It can be used to model heart rhythms. If a stimulus is applied to the oscillator, it will return to the curved envelope discussed in the article. However, if "pushed just right", the oscillator's current state will be pushed towards the very center of the loop, and it will stop oscillating. This is the mechanism ...


3

Even if it were possible to selectively destroy sensory (afferent) nerves alone, the individual would not be able to walk/move normally immediately afterwards, because there would be no environmental stimuli with which to orient one's actions. Two of the senses people often overlook are balance (or spatial orientation) and proprioception (where the body ...


2

It is more complicated than this, but... I don't think it has as much to do with the refractive index of water but rather the shape of our corneas and the loss of this shape advantage under water, for if the eyes are protected by goggles, one can see quite clearly underwater (much the same as a camera can, as the shape of it's lenses are not affected). Any ...


2

If you took someone that had never ridden a roller coaster, or even been exposed to rapid acceleration, and had them try a virtual one - would they feel the same stomach lurch as I did? Probably not. A congenitally blind person, who can distinguish between a globe and a cube by her touch, is not able to tell which one is which (without touching) when ...


2

The basal lamina is a specialised type of extracellular matrix. It is found on the basal side of all epithelial tissue but can also surround other cell types like myocytes and adipocytes. It is also called the basement membrane, although it is not the traditional plasma membrane that we have come to know and love. Rather, it is composed of proteins (often ...


2

How do cells know whether they should grow the hyaline cartilage? Both growth factors and cytokines are involved but the trigger mechanism is unclear [1]. Bones grow in length at the level of epiphyseal plate where chondrocytes produce hyaline cartilage which by addition of calcium and phosphorus ions turns into hard bone [2]. It is believed that the ...


2

As discussed in the comments, there are theoretical and practical problems with arriving at such data. There have been controlled experiments using canines, but you have specifically stated your interest in humans. I offer a summary of a few observational studies that may be helpful. In this study, 117 patients in intensive care units (who are likely to ...


2

An increase in linear dimension by $x$ causes an increase of $x^3$ in volume and mass. The force that a muscle can generate roughly scales with the cross-sectional area of the muscle, an increase of $x^2$ for a muscle scaled by a factor of $x$. This means that larger animals need proportionally larger muscles (by a factor of $\sqrt {x}$) to achieve ...


1

The fundamental principle behind this is a "sensor" or the excitation-contraction coupling, regardless where you are. Let's consider the striated muscle and the cardiac muscle. The function of excitation-contraction coupling in skeletal muscle is as voltage sensor to tell the SR, "We have got an action potential; release Ca2+ for contraction". This is a ...



Only top voted, non community-wiki answers of a minimum length are eligible