133
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Why is the heart not in the middle of the body?
First of all, let me make it clear that the heart is at the vertical centre of the body -- it is not shifted towards left (or right). However, it is slightly tilted towards the left in most cases.
...
- 14.2k
24
votes
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ECG wave names origin
Interesting question! I searched briefly and came up with an answer from this short paper.
I won't repeat all the details of the paper, but to be not a completely link-only answer I will give a brief ...
- 47.2k
10
votes
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Why is Heart Rate Recovery after exercise reasonably well described by a mono-exponential decay?
I think most people would take exponential decay in a circumstance like this to be the null hypothesis. That is, if you had something not exponential decay, that would be curious and interesting and ...
- 47.2k
9
votes
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Is a one ventricle heart feasible?
Alternative Heart Morphologies
Amphibians and some reptiles have a three-chambered heart, with 2 atria and a single ventricle. There are still separate circulatory pathways for the lungs and the rest ...
- 47.2k
8
votes
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How does increased resistance to flow decrease blood pressure?
There is not enough information in the question to solve it.
The answer key from the original question makes a logical error:
Viscosity is directly proportional to resistance.
This is true. An ...
- 47.2k
6
votes
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How can heart disease cause excessive sweating?
The answer lies in compensation. Take myocardial infarction, for starters. MI, if large enough, severely weakens the heart, and hence, at the same level of stimulation, it can no longer pump blood ...
- 4,689
6
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ECG wave names origin
According to this site: http://www.ecglibrary.com/ecghist.html
Originally the waves were designated as A,B,C& D but after correction they were termed as P,QRS, T.
Why PQRST and not ABCDE? The ...
- 4,836
6
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Why do people perceive blood pressure as the force that moves the blood forwards (see details)?
In the vascular system, pressure is what moves blood forwards, at least in an analogous manner to voltage...just like voltage, pressure itself doesn't move things, but a pressure gradient does. You ...
- 47.2k
6
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Why is the heart adversely impacted by chronic psychological stress, yet it benefits from routine physical exercise?
From the perspective of sympathetic nervous system
Exercise induced adaptations of heart
A common phenomenon in endurance athletes is the athlete's heart /athletic heart syndrome
Once athletes stop ...
- 1,955
6
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Heart rate vs body size
The paper you link finds that there is not a significant correlation between body mass and resting heart rate in humans. While there is a well known negative correlation across mammals:
This is the ...
- 12.3k
6
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Does blood clot reduce blood flow?
A blood clot can nearly completely or completely block an artery, in which case the blood flow will be reduced or stopped.
How do we know this?
Pulmonary Embolism (Merck Manuals):
Pulmonary ...
- 8,124
6
votes
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How are monocytes larger than capillaries?
They aren't completely rigid and can change shape to squeeze through (see Downey et al).
If they are activated, monocytes can get stuck in capillaries and block them, which contributes to poor ...
- 47.2k
5
votes
Accepted
Why is the current flow shown to be flowing from the negative area towards the positive area?
By convention, positive current is assumed to be the direction of flow of positive charges. The trouble is that in many common situations (like this one), the current is actually carried by electrons ...
- 3,645
5
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Why does high blood pressure not damage the body during exercise?
Actually it can. See https://clinicalhypertension.biomedcentral.com/articles/10.1186/s40885-016-0052-y for instance:
Deleterious effects of HRE [hypertensive response to exercise] on structure and ...
- 3,060
5
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How does the SNS increase the heart rate when it causes an increase in cellular uptake of potassium?
It's important to keep in mind that extracellular potassium concentration is normally very tightly regulated at 4.2 mEq/L (±0.3 mEq/L in nonpathological circumstances.) It's precisely because so many ...
- 26k
4
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What prevents backflow of blood from right atrium to vena cava during atrial systole
Pressure differences. Atrial contractions are much more gentle than ventricular ones, and in normal circulation the venous pressure in the vena cava often stays higher than the right atrium, even ...
- 47.2k
4
votes
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Isolating the vasculature of an organ?
The typical name for this technique is "corrosion casting" - if you search for literature on corrosion casting you will find many many papers detailing the technique. Another answer mentions "...
- 47.2k
4
votes
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At what stage is the nervous system developed enough to interpret neuronal signals as 'pain'?
First, there is some confusion on your part about heart cells and pain perception. Heart cells generate an action potential intrinsically; they do not need the central nervous system to beat (your ...
- 26k
4
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Seizures and blood pressure
Yes, seizures can affect autonomic function including blood pressure. Such symptoms can even result in death. Note though that not all seizures are the same: there are many different types with many ...
- 47.2k
4
votes
The 4-chambered heart
The short answer is crocodiles may be secondarily cold blooded, but the long answer is warm blooded and cold blooded is not a binary condition but a spectrum.
It has to do with how much heat you ...
- 15.4k
4
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Can the heart generate its own rhythm independent to the SAN?
Your textbook and review guide are correct, but the missing details may be a little confusing. Yes, the heart has the property of automaticity, meaning action potentials fire on their own at a certain ...
- 8,831
4
votes
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How do veins's valve pocket sinus tend to become hypoxic?
As veins are not permeable to O2 thus O2 can't escape into surrounding cells.
Veins are not like impermeable rubber tubes, they are 'living' structures requiring, like all cells, Oxygen and glucose ...
- 26k
4
votes
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When endothelial cells in blood vessels (arteries or veins) are damaged, does atheroma form first or blood clot?
It is unlikely that atheroma would develop as a complication of a thrombus.
Atherosclerosis and thrombosis are two independent disorders and not two stages of the same disorder. Atherosclerosis is a ...
- 8,124
4
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Was Dr. Livesey's treatment a valid one in the Treasure Islands?
The procedure described here is called venesection. It is no longer standard of care, but was when Treasure Island was written.
Here is an excerpt from the first edition of Cecil's Textbook of ...
- 8,831
4
votes
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Can fats clog veins or capillaries?
I know that so much fats running in the bloodstream could deposit in arteries, harden forming a plaque and cause atherosclerosis. But what about veins (which are formed from same types of layers as ...
- 982
4
votes
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Consequences of abnormal blood pressure unrelated to cardiac output?
Blood pressure, as you noted, is just a means to an end: the flow of blood through tissues. The trouble is, many of the body's regulatory systems use blood pressure (rather than flow) as an index of ...
- 1,307
4
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Do afterload and stroke volume form part of a negative feedback loop in blood pressure regulation?
However, it then seems that hypertension, which increases afterload, would lead to a decrease in blood pressure and form a negative feedback loop. Is this in fact what happens in the human body?
Yes ...
- 26k
3
votes
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How does heart beat faster while doing a strenuous task?
I am sure that there are many ways that your body can regulate heart rate, but I am going to cover this topic briefly from the perspective of $\ce{CO2}$/$\ce{O2}$ concentrations, and pH.
The medulla ...
- 556
3
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Isolating the vasculature of an organ?
I think that you are looking for plastination. Its developer, Gunther von Hagens, uses it to preserve whole bodies as well as selected tissues, such as muscles, nerves and vessels, for teaching uses ...
- 1,313
3
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Is there any relationship between heartbeat rate and life span of an animal?
There is a relationship: they are negatively correlated. Shorter-lived animals tend to have faster heartbeats, and longer-lived animals tend to have slower heartbeats. It gets more striking than that, ...
- 504
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