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.
...
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36
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How did the cardiovascular system evolve?
While others have addressed the big picture aspects of your question, I think it would be useful to look at the specifics.
Have a look at the heart (or more accurately, the hearts) of the earthworm: ...
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25
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Why does the face turn pale in dangerous situations?
Red blood cells are not equipped with a motor system to propel them through the blood stream. Instead, they are passively transported through the vasculature by the the pumping action of the heart. ...
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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 ...
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23
votes
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Will the heart keep beating if it's separated from the body?
Short version
The heart has the ability to beat independently of the brain as long as it has oxygen. The heart will eventually stop beating as all bodily systems begin to stop working shortly after ...
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22
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What is the speed of blood?
As you note yourself, this depends strongly on the vessel that you are studying. I found this table in reference 1:
It lists speeds between 34 and 45 cm/sec for the inferior vena cava and 12 to 16 cm/...
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14
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What is the cause that angina pectoris is felt in your left arm?
It has mainly to do with the embryonic origin of organs, with the heart being a typically left sided organ, it develops sharing some nerves with the left thorax and left arm.
There is however high ...
12
votes
Will the heart keep beating if it's separated from the body?
Sydney Ringer showed in 1882 that when the heart, when separated from the body and immersed in lactated Ringer's solution, or even isotonic saline solution, will beat because it has its own pacemaker ...
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12
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How did the cardiovascular system evolve?
This kind of question was raised in a book called "Darwin's Black Box" by Michael Behe, who is a biochemistry professor in the U.S. - he calls this 'irreducible complexity' (IC). For example, the ...
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10
votes
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Can defibrillation be done with a car battery?
In general, no.
Car batteries are designed to provide a large amount of amperage, to turn the starter with a high amount of torque via an electric motor. Generally this is done at 12 or 24 volts.
...
10
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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 ...
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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 ...
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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 ...
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7
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What is a lethal dose of THC?
According to the abstract from this paper, the intragastric LD50 of $\Delta^9THC$ (tetrahydrocannabinol) in sesame oil using Fischer rats was 1270 mg/kg. Assuming rats and humans are identical (they'...
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6
votes
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Does our heart stop when we sneeze?
Both your linked fact from the University of Arkansas
When you sneeze, the intrathoracic pressure in your body momentarily increases. This will decrease the blood flow back to the heart. The heart ...
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6
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How does Bernoulli’s Principle apply to the cardiovascular system?
Bernoulli's principle can be a little tricky when applied to the cardiovascular system, but it still holds true across the entire system. You mention a good point that the relationship doesn't seem ...
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6
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How did the cardiovascular system evolve?
This is a good question, but it has a vast scope, as you're talking about the progression of millions of different living animals over hundreds of millions of years, none of which are still alive, so ...
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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 ...
- 41.2k
6
votes
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 ...
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6
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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 ...
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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 ...
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6
votes
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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 ...
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6
votes
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 ...
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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 ...
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5
votes
How to analyse an ECG?
First bump is called P point, middle is QRS wave (as in Q-down, R-up, S-down), and last bump is T. Every feature is representation of electrical activity in certain region of heart. E.g. P bump is ...
5
votes
Will the heart keep beating if it's separated from the body?
I was wondering if a heart keeps beating if it is separated from the body?
Yes, it does. Here's a video showing it (don't click if you're squeamish!): https://www.youtube.com/watch?v=NEuSCPifKhA
It's ...
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5
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Similarity between a heart attack and a spasm
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 ...
- 1,122
5
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What is the cause that angina pectoris is felt in your left arm?
Our pain-sensing neurons work in useful ways only when they inform about skin areas or muscles. When nettles sting your left hand, you want to retract your left hand right away. This is in part an ...
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5
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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 ...
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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 ...
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