Questions tagged [cardiology]

The study of the physiology and pathology of the heart and the cardiovascular system.

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16 views

GHK Equation and Action potential

Can GHK equation be used to predict the membrane potential even if the cell is not at resting state? To say it again, can we use GHK equation at every moment during Action potential? I'm confused ...
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Is deoxygenated blood blue in colour? [duplicate]

I am asking this question because in every book vein is coloured blue. Is it really blue?
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60 views

why dead mouse doesn't bleed when we cut their skin?

When we are pricked by a needle, we bleed nevertheless it's so small wound. But when we do mouse anatomy, it doesn't bleed even if we cut their whole abdominal skin. Other student asked about that, ...
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Why does high blood pressure not damage the body during exercise?

Exercise is commonly understood to lower blood pressure by making the heart stronger. Mayo Clinic says, Regular physical activity makes your heart stronger. A stronger heart can pump more blood with ...
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Bundle of His and Atrioventricular Bundle difference

I see most definition using Bundle of His and AV bundle interchangeable including the wikipedia when you do a Google search for AV bundle But my text book treats as two different things. The action ...
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107 views

Garden Hose Analogy for Blood Vessel Resistance

I've been trying to reconcile the resistance component of Poisseuille's law with a mental analogy of a garden hose; specifically, I had assumed that the effects of reducing the radius of a blood ...
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24 views

How can the pressure during contraction vary between the left and right ventricles?

After reading this passage from my physiology textbook (Vanders Physiology p. 384), I'm confused about how exactly the right and left ventricle can create markedly different pressures as they pump ...
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58 views

How can I simulate heart electrical activity in a 2D plane?

I am not a biologist/medical student, I study software engineering. But I really like when medicine and engineering hold their hands together to achieve great things. As a side/toy project, I was ...
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Is there a way to derive Bazett's formula to correct QT interval in ECG?

As we know that QT interval in ECG is a function of heart rate (HR) and to comment on the pathology associated with altered QT interval, we must neutralise the effect of HR. For this Bazett's formula ...
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Popliteal artery for a heart bypass

My father undergone surgery 10 years ago to get 3 bypasses close to the heart. Surgeons did a very long cut on his leg to get the material to make the bypasses they would later put on his chest. What ...
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96 views

Why is the current flow shown to be flowing from the negative area towards the positive area?

When I was studying the ECG chapter in the book "Guyton and Hall Textbook of Medical Physiology", I noticed something odd in one of the pictures: As you can see the current is shown to be ...
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Concept of mean systemic filling pressure

Mean circulatory filling pressure (MCFP) in humans was defined by Guyton as "the pressure that would be measured at all points in the entiere circulatory system if the heart were stopped suddenly ...
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How are cardiac cells connected by intercalated discs?

I understand that intercalated discs run transversely across the longitudinal axis of the muscle. But what I don't understand is how this same disc binds the cardiac cells together. Are the cells ...
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When and Why does G0 phase occur?

I've asked this question, specifically because i've seen this question. As we see in this diagram , G0 phase occurs after M phase and at a specific point within G1 phase. Is there a meaning to ...
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Why didn't more muscles evolve the endurance of heart muscle? [closed]

The heart is a muscle capable of both the quick contraction of white muscle cells, and also the endurance of red muscle cells. Why haven't more muscles in the body adapted the same combo of abilities? ...
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Cancer in cardiac cells

We were recently taught that cancer occurs only in those cells which undergo cell division so, cancer is not possible in cardiac cells and neurons. But we know that till a certain age our heart grows ...
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35 views

Consequences of abnormal blood pressure unrelated to cardiac output?

A question from Kaplan's MCAT Biology Review asks: In bacterial sepsis (overwhelming bloodstream infection), a number of capillary beds throughout the body open simultaneously. What effect would this ...
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What happens to Mean systemic pressure during the start of aerobic exercise?

Hi this was one of the answers to a MCQ I had to do (it said it would decrease 2 times in the first 10 seconds of a run). I am not too sure what actually happens to it though Using the equation VR=MSP-...
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25 views

Can severe vasoconstriction increase systolic blood pressure?

I know that, vasoconstriction results in increased total peripheral resistance which is responsible for the rise in diastolic blood pressure. Also, cardiac output is responsible for the systolic blood ...
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39 views

How does noradrenaline result in rise of systolic blood pressure even when the cardiac output is decreasing?

Systolic blood pressure[SBP] depends on the cardiac output. When Nor adrenaline is given there is vasoconstriction due to alpha-1 action on blood vessel, vasoconstriction results in increased total ...
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18 views

Can we say that the source of the most circulatory regulation in the human is the nervous system?

local regulation of blood flow and Baroreceptors, both stimulate the neurons and send messages to the brain. so can we say that the source of the most circulatory regulation in the human is the ...
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closed circulatory system and blood supply to the heart endocardium

Human has closed circulatory system. in this type of circulation of blood, the vessels are not directly contacted with the cells and feed the cells by extracellular fluid. Now, how does the blood flow ...
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12 views

Relationship between blood pressure time series and ventricular dynamics of the heart

The answer to this question is probably very straightforward, but I have actually had some difficulty finding an explicit answer online. To what extent does the oscillatory pattern of arterial blood ...
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20 views

Frequency modulation of parasympathicus and sympathicus

According to my literature, the sympathetic nervous system accelerates heart rate and modulates < 0.1 Hz, whereas the parasympathetic nervous system decelerates heart rate and is modulated 0.04 - 0....
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Why is the afferent arteriole considered to be the last branch of the kidney artery

Why is the afferent arteriole considered to be the last branch of the kidney artery while the efferent arterial is also present and branches off on its own again?
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fibrous skeleton of the heart

is it true to say that "fibrous skeleton is between all of the myocardium and most of the cardiac muscle attach to that"? cause I can't get this that how can it be between all the muscles.
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how has the fibrous skeleton contributed to the structure of the heart valves?

I'm a little bit (or a lot!) confused that how has the fibrous skeleton contributed to the structure of the heart valves? Since the fibrous skeleton takes part in the cardiac muscle, how does it help ...
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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 ...
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Is there any case in which excitability increases with lowering the RMP?

My professor says , at a more negative RMP, less sodium ion channels are inactivated, so if you take 2 of the exact same neuron with the same threshold potentials, and try to excite them starting from ...
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Understanding the ECG waveform with respect to Lead Positions

I am really confused about the Representation of potential in an ECG graph. First i will ask what is on the vertical axis? (I guess it is electrical potential in millivolts) But again it changes for ...
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69 views

In the PR segment of an ECG, how come there's no current flowing?

I don't really know how to phrase the question, but to put it as clearly as I can, I don't get why it is the P wave "flattens down" when the atria have completely depolarized. I get that the ...
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60 views

Why is there disagreement on the number of surfaces of the human heart?

I am finding that some state that there are 5 and some that say that there are 3. For example, "Cardiology: An Integrated Approach" that was published in 2018 states that There are 3 surfaces of ...
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36 views

How much blood do we have when the heart first starts to beat?

How much blood do we have when the heart beats for the first time? It should be between the third and fourth week of embryonic life.
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Why does a stronger heart cause blood pressure go down

Intuitively, why does a stronger heart cause blood pressure to go down? The answers I've found from a cursory google search seem to indicate that it has to "work less hard" to pump the blood and that ...
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199 views

Was Dr. Livesey's treatment a valid one in the Treasure Islands?

Here is that incident from Treasure Island by Robert Louis Stevenson, where Billy Bones had a 'minor' heart attack or a stroke (according to R.L. Stevenson). To give a little background about Billy ...
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Correlation seen with low billirubin levels but not the gene that causes Gilbert's syndrome

I was reading the following study on associations between bilirubin and CAD (coronary artery disease). They looked at the bilirubin association, and the genes that cause Gilbert's syndrome, which ...
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Frameshift Mutation

With regards to LMNA frameshift mutations further downstream in the tail region, specifically (p.Arg455Gln fs*5) which has yet to be found/recorded in any medical literature...Does anyone have any ...
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54 views

Why does higher venous volume increase atrial pressure?

If the cardiac output stays the same (hypothetically, although obviously it doesn't stay the same), then why does higher venous volume increase right atrial pressure? Shouldn't the flow rate be ...
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Does increasing contractility increase LV ESP?

I see many PV diagrams showing a negligible difference in the ESP when contractility increases. I'm wondering why this is the case, because if more blood is being pumped out into the aorta, the MAP ...
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26 views

Vasoconstriction and blood flow

The resistance in a blood vessel is equal to the pressure difference divided by the blood flow. Let us now say that a sympathomimetic causes vasoconstriction which increases the resistance. Does this ...
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How does the cardiovascular system improve upon repeated, strenuous exercise?

New here, hopefully this is the right place to post this question. It's widely known that repeated, strenuous aerobic exercise gradually improves the capacity of one's cardiovascular system — $\text{...
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59 views

Can anybody recognize this cardiac waveform? [closed]

Is this an artifact or an arrhythmia?
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912 views

Difference between Premature Atrial Contraction and Atrial Fibrillation

what is the difference between Premature Atrial Contraction and Atrial Fibrillation. I know that both have irregular heart beat but have normal QRS complex. Both have abnormal or absence P waves but a ...
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41 views

Definition for different arrhythmia

I am wondering if there is an organization, a document or a research that standardize all the rhythms? Such as describing how long should the ECG be flatline to be considered as asystole? The rhythm I ...
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226 views

How are monocytes larger than capillaries?

I have read that the average size of a capillary is about 8 micrometers. How is it possible that the 15 micrometer or so monocytes in blood do not block these vessels? https://en.m.wikipedia.org/wiki/...
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Is the medium which transmits the electrical impulse through the heart different to a nerve?

According to Nerve A nerve is an enclosed, cable-like bundle of nerve fibres called axons Being an Axon An axon (from Greek ἄξων áxōn, axis), or nerve fiber, is a long, slender projection of a ...
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369 views

Cardiac cycle and atrial contraction

During atrial contraction ("a" in the figure), why does the ventricular pressure match the atrial pressure? The ventricular pressure generally stays the same throughout passive filling until it ...
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124 views

Is returning cholesterol to the liver really performed by HDL?

Various answers in biology SE, including two quite upvoted ones (1, 2) claim that (in humans) returning cholesterol to the liver is done by HDL. If I understand correctly, Wikipedia's Reverse ...
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268 views

When endothelial cells in blood vessels (arteries or veins) are damaged, does atheroma form first or blood clot?

I have learnt from Khan Academy's video on atheresclerosis that when the endothelial cells of an artery are damaged, atheroma forms at the site, and if the atheroma’s fibrous cap is ruptured, ...
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135 views

How do veins's valve pocket sinus tend to become hypoxic?

For context, this question relates to the formation of deep vein thrombosis as I read that hypoxemia in vein can trigger coagulation cascade and cause a thrombus to form in vein. I read that vein's ...

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