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13

Interestingly there is a inverse negative correlation between heart rate and life span, meaning the faster your heart rate is, the shorter is your lifespan. See this figure (from the paper 2 cited below): When the authors plotted the approximately total heartbeats vs. the lifespan, the amount of total heartbeats was in a pretty narrow corridor: So it ...


11

The basic reason is osmosis, the tendency of solutes to move from an area of high concentration to one of low concentration across a permeable barrier. So, ingesting large amounts of salt results in a high sodium concentration in the blood stream. This in turn causes water to enter the blood vessels by osmosis. More water in the blood means a greater volume ...


11

Simple answer, yes. It really is a matter of how technical you wish to be. By defintion, all arterial flow conveys blood away from the heart. The largest arteries exhibit the Windkessel effect which allows for the compression-based effects that bobthejoe inferred. Explicity, as blood is pumped out of the left ventricle, it stretches te aorta, and this ...


11

The normal cardiac cycle is comprised of two distinct phases: the systolic phase in which the heart contracts, ejecting the blood, followed by the the diastolic phase when the cardiac muscle relaxes, refilling the heart with blood. This cycle is assured by specialised cardiomyocytes (Cardiac muscle cells) that conduct electrical impulses through the heart. ...


10

Polynomial gives a good hint. By adding in a known tracer of known amount that should only circulate in the blood stream, the concentration of the tracer when completely distributed will give the volume of distribution. If the tracer only stays in the bloodstream (and that's a fairly large IF), then the VD will be equal to the VBlood. However, as many ...


10

It is easy. Method A, simple, is based on "counting the fish in the pond" method. Make rough estimate of amount of blood in the organism. Choose a component of blood that is replenished slowly [from liver or marrow etc]. That takes time to replenish. Red blood cells are probably OK. Some easily measurable and slowly replenished component of blood. Let's ...


10

Trans fatty acids are digestible, but they cause an increase in LDL and a decrease in HDL, which is the leading mechanism for atherosclerosis. So, they increase the risk of a cardiac infarct. LDL means Low Density Lipoprotein, it's one of the 5 major lipoprotein groups. Lipoproteins carries the fatty acids and cholesterol which were absorbed from ...


10

Dizziness after eating, which can lead to falls and passing out, is called postprandial hypotension, and as the heart is indeed responsible for responding to hypotension by increasing it's rate - which can be seen in any number of clinical scenarios from blood loss to standing up too suddenly - failure to do so, for any reason including heart disease, can ...


8

Quick answer, no. Imagine a balloon; as you compress the balloon, there will be a lot of air that leaves it. But as you let it relax, the balloon pulls in surrounding air even as you fill it from another side. When the aortic and tricuspid valves are closed, there is blood flow forward but due to conservation of mass, the blood goes back to fill in the ...


8

Lipids require more oxygen to burn, but also they are cheaper to store (since they have great calorific power than carbohydrates and they're hydrophobic, thus not requiring water for their storage). The body can store so much lipids that it becomes an almost everlasting energy source (A normal adult have enough energy stored as fat to allow basal metabolism ...


8

Very simply putting, irregular heat beat means that the pulse is not regular. It can be diagnosed by checking your pulse clinically. Irregularities are further classified as: Regularly Irregular: this occurs in heart blocks where every second or third beat is skipped regularly causing a pattern. Usually as time progresses the degree of block worsens and ...


8

Ewing's sarcoma is a bone cancer. As such, it does not arise as a primary tumor in the heart. Ewing's sarcoma does metastasize. Like any metastatic cancer, it seeds along it's venous return to the heart, "taking root" in suitable tissue. Cardiac metastases of Ewing's sarcoma are exceedingly rare, with only a few reported cases. Since all blood returns to ...


7

In layman's terms: an Asystole is not affected by the electric shocks of a defibrillator. A defibrillator is used when the heart goes in fibrillations because it actually CAUSES an asystole. The idea is that you basically reset the heart to a blank state so you can start normal CPR procedure to help the heart go back to a normal rythm. That's why you see ...


7

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 ...


7

To say that there is a cutoff of one minute at which time shocking becomes ineffective is incorrect. The best way to defibrillate a heart within one minute of VFib onset is with electric shock. In fact, short of certain drugs in certain instances, it's the only way to defibrillate Vfib, regardless of the amount of time that has passed. If the one minute ...


6

Insects primarily get oxygen through diffusion of air through their skin. I doubt the antennae need hemolymph circulation.


6

This is a specific version of the great cancer question: "Why are some cancers more common than others?" The answer is either "Some have more common causes", and (or) "Some are cured spontaneously more often". So now all you are asking is "What causes cancer?" and "How do we cure it?" Given that, I don't expect a general definitive answer will be ...


6

This page (and many others) explain the idea rather well. This is more of a physics than a biology question, but the fundamental concepts are the same. In fact, contrary to what you wrote in the question, the measured blood pressure should be lower than expected if the arm is elevated above heart level. When you reduce the pressure on the bent pipe, ...


5

Insects do not posses closed circulatory system, but a space where organs float in a fluid called hemolymph. They don't have blood vessels (but some arthropodes have pumps that act a like heart). The hemolymph allows nutrients and excretion products to diffuse, but usually doesn't serve as a means to transmit oxygen to the tissues. In insects, the oxygen is ...


5

Because of reflected pressure waves and the stiffness of the blood vessel. The forward pressure wave from the heart travels much faster than the blood itself and is reflected at areas of tapering and branching. This backward wave slows the forward flow of blood, and at the same time, when it meets the next forward pressure wave, that forward pressure wave ...


5

I would be very surprised if the time of day made a difference. I've personally never heard mention of such a phenomenon in discussions with intensive care practitioners (where of course HR and BP are measured constantly). However this is only the case during rest, this paper (on horses) suggests that there is some difference in HR and BP after exercise ...


5

According to the Wikipedia page on Supraventricular tachycardia the heart can go to a new faster rate in the space of a single beat, and then come down again just as quickly, as shown in this image taken from the Wikipedia page.


5

There are many reasons why the maximal heart rate decreases with age. The most prevalent is the heterogenous thickening of the walls of the heart. Cardiac output is stroke volume times heart rate. When the wall thickens, the heart needs more energy to achieve the same pumping (bigger stroke volume) or it needs to increase heart rate at rest. Because of ...


5

The parasympathetic supply to the heart is by nerves and that is truncated during surgery as pointed out. The sympathetic supply to the heart is by two means: Through sympathetic nerves from the sympathetic trunk From the adrenal medulla which secretes both adrenaline and nor-adrenaline directly into the blood stream The heart contains the beta ...


5

To put it in very simple words the reason for isovolumetric contaction and relaxation is to make the necessary pressure changes that is necessary to allow blood to flow into or flow out of the ventricles. The basic formula you need to remember to understand this is:- Fluids flow from high pressure area to low pressure area along the pressure gradient ...


5

I was able to do some reading and research and I found some interesting information that was a). news to me. And b). the answer is yes... And no. A spasm can be the cause of a heart attack by causing the coronary artery to contract. When that artery contracts, it causes a dramatic decrease in blood flow to the heart. When the heart looses access to ...


4

The number you are looking for might be quite large depending on the level of detail you demand for the measurement. There is no single number for the area of most objects in fact. The importance of fractals is much related to the question of what is the perimeter or surface area of something. The classic example is trying to determine the length of ...


4

In terms of cell bodies? Zero. There are autonomic projections from the spinal cord (sympathetic) and vagus nerve (parasympathetic) to the sinoatrial node, the atrioventricular node, and at discrete points in the atria and ventricles.


4

According to this source, gold is not a necessary trace element for living organisms. Would have been cool, though...


4

The purpose of valves is to maintain blood pressure against gravity until it reaches the heart. The Superior Vena Cava (SVC) inlets exist above the heart, and any valves would only prevent gravity from helping bloodflow. The Tricuspid prevents blood from the SVC from just directly flowing into the Right Ventricle. As a note: The Eustachian Valve either ...



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