Tag Info

Hot answers tagged

6

First of all, it will be practically impossible to make an estimation of how long a transplanted organ will live and how many times it could be transplanted. However, it is relatively safe to say that it will not live forever. To be able to receive an organ transplantation, the HLA MHC-complexes of donor and receiver need to be matched very carefully, to ...


5

The median lifetime of an organ transplant is some 5 to 10 years mainly due to chronic rejection mediated by host-versus-graft immune responses. Hence long-term transplants definitely have a limited half life. However, this graft rejection is relatively slow and early explantation and re-implantation in a new host may actually "reset" this process? With ...


5

The "back of your mind" is correct: "if the muscle gets bigger, it's simply because individual cells get bigger." Growth of muscle can occur in three ways: by an increase in muscle cell numbers by an increase in muscle fiber diameter by an increase in fiber length. However, growth in cell numbers is limited to the prenatal and immediately postnatal ...


4

A tissue can undergo two types of quantitative growth: hypertrophy - cells increase in size hyperplasia - cells increase in number There are tissues that grow as a result of one of the above processes and there are tissues that grow because both processes happen. A Google search for muscular growth yields as first result Muscle hypertrophy. And this is ...


4

Vision deteriorates for both reasons, but I'm not quite sure how to separate the effects of aging from wear and tear. Cataracts are the leading cause of blindness in the world. Ways in which environment (which falls under the category of wear and tear in my book) affects cataract formation: UV light: people living at high altitudes (e.g. Tibet) have ...


4

If there are no pacemaker cells active, no muscle contraction will occur. This condition is named asystole. It can be a temporary or definitive condition. Some would call it "extreme bradycardia" in temporary cases, but this is just an euphemism. Edit: Ok, so let's try to clear up the confusion a bit. Technically, there is no asystole involved here (not ...


3

Why can I feel this, when no forces are actually being applied to my stomach? Acceleration sensors are in the ears and are part of the vestibular system. The vestibular nuclei in the brain uses acceleration- and visual signals to decide what happens to your body. It can be fooled by visual signals without the presence of acceleration signals. The role ...


3

$H_2S$ is the end product of sulfur related respirations (like sulfate respiration, sulfur respiration, etc...). By aerob (oxygen) respiration the oxygen in $O_2$ has 0 oxidation number, by $CO_2$ the oxygen has -2 oxidation number, so it was reduced while the carbon was oxidized. By the thiosulfate respiration of Salmonella enterica the following reaction ...


2

To add my 2 cents worth: Breathing rate and depth is regulated by chemoreceptors in the medulla. These chemoreceptors primarily respond to pH of the blood, but the pH is for an important part determined by the CO2/HCO3- equilibrium as explained by @TomD. Essentially it is the increase in CO2 that is sensed by the medulla and which increases breathing ...


2

I concur with @souvik.bhattacharya but I wish to elaborate on it. The lung collapse indeed stops gas exchange in marine mammals by keeping the air away from the lung tissue that normally exchanges O2, CO2 and N2. Build up of N2 results in the bends after the pressure drops when re-surfacing (McDonald & Ponganis, 2012). However, a study by Hooker et al. ...


2

I think I got the answer.... The primary anatomical adaptations for pressure of a deep-diving mammal such as the sperm whale center on air-containing spaces and the prevention of tissue barotrauma. Air cavities, when present, are lined with venous plexuses, which are thought to fill at depth, obliterate the air space, and prevent "the squeeze." The lungs ...


2

Vitamin D does not bind to Calcium. It is a pre-hormone which is converted to calcitriol. Calcitriol has an intracellular receptor (VDR) that, as a heterodimer with Retinoid-X receptor, regulates gene expression. I guess the "should not be had together" is because of possible over-absorption of Calcium. There are commercially available supplements (e.g. 1, ...


1

It is not the absolute plasma levels that are important, it is about their relative differences during the cycle. The steep rise in FSH during the first days induces follicle stimulation. The LH surge at day 12 induces maturation of the egg and stimulates its release (see wiki page). The fact that LH's absolute plasma levels are higher may theoretically have ...


1

I hope you might edit your question to give examples of such comparative injuries. I'm trying hard to imagine an example of this phenomenon, but I can't. The human body doesn't have a tripwire, or a lower limit of injury under which it will not respond. Normally the body mounts appropriate defenses against all injuries from the very minor, like a paper cut, ...


1

Bradycardia is a heart rate under 60 beats per minute. Your strip shows a heart rate of ~54 BPM (so, yes, it's bradycardia), and the rhythm is trigeminy. There is no asystole involved. In the following rhythm strip, initially it shows supraventricular tachycardia (of >150 BPM). After adenosine administration, a short period of asystole occurs, allowing the ...


1

No, macroscopically human muscle works by oscillation. This means that when a muscle is contracted (isometric contraction), some fibers alternatively contract through the actin/myosin process while some others relax at the same time. The end result is that the muscle as a whole keeps the same length, although it still does consume energy to stay in that ...



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