Questions tagged [cardiology]

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

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T-tubules in Muscle Cells

I understand that T-tubules are common to striated muscles such as skeletal and cardiac muscles (with smooth muscle cells having caveolae) but what precisely (if any) is the difference in the T-...
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What happens in aortic valve stenosis?

Normally work done by heart for increasing the velocity of blood is only 1% of total work! In stenosis as the cross section of valve decreases it will cause increase of velocity of blood (Bernoulli’s ...
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Calculation of blood flow rate and pressure change in heart

Question: Blood flows from the left ventricle of the heart through the aortic valve and then to the aorta for system circulation. In a patient, the diameter of left ventricle outflow tract (LVOT) is ...
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Why is mean systemic filling pressure used to calculate pressure differential for venous return?

I'm really struggling to understand venous return curves and their relationship to mean systemic filling pressure. I understand mean systemic pressure is the pressure that would be measured throughout ...
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Volumes of the four heart chambers

We know that the left ventricle which feeds blood into the aorta is typically the largest chamber of the heart. I'm looking for the typical absolute and relative sizes of the four heart chambers.
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How does the SNS increase the heart rate when it causes an increase in cellular uptake of potassium?

Since β-Adrenergic stimulation increases cellular uptake of potassium, this will reduce the plasma concentration of potassium. Thus, a more negative membrane voltage will arise as the potassium ions ...
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sympathetic nervous system and vasoconstriction

At the moment I am very confused and I would highly appreciate any explanation. When the sympathetic nervous system is activated because we are for example exercising, our blood vessels constrict. The ...
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Can we improve the hemocompatibility of VAD by growing a single layer of endothelial cells on the surface?

Maglev centrifugal pumps have been used in the latest ventricular assist devices (VAD) and several experimental total artificial hearts (TAH). Compared to previous generation pumps, maglev pumps don’t ...
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Do afterload and stroke volume form part of a negative feedback loop in blood pressure regulation?

Blood pressure is the product of cardiac output and total peripheral resistance: $\text{BP} = \text{CO} \times \text{TPR}$ Since cardiac output is the product of heart rate and stroke volume, we have: ...
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Pulse pressure, vascular physiology

I always though compliance of a vessel is a thing that prevents systolic pressure to goes up a lot and also prevents the diastolic pressure to goes down a lot, and that works because in ...
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Heart rate and Metabolic rate relationship

Metabolic rate in humans can be approximated using the Penn State equation. It can also be estimated using direct and indirect calorimetry. According to Kleiber's law, metabolism scales across species ...
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Why did the requirement for coronary circulation arise?

Why the heart does not absorb the blood directly(for it's oxygen requirement) rather than taking it through coronary circulation? Is it related to the permeability of myocardium? Having such a ...
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Why does the sympathetic nervous system constrict in heart failure?

As I learn about heart failure in medical school, we are consistently taught that one of the compensatory responses to heart failure (and the accompanying reduction in cardiac output) is for the ...
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How much charge is moved for one heart beat?

Roughly, how much charge cycles (in and out of our heart cells) for each heart beat? I am just looking for the total number of Coulombs, but, since all charge can apparently be accounted for with just ...
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What benefit do cardiomyocytes accrue by requiring calcium induced calcium release (relative to skeletal myocytes)?

According to 2 sources I've read, in contrast to skeletal myocytes, cardiac myocytes need calcium to diffuse in to result in contraction. One source says that they need large amounts of calcium to ...
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Does your blood stop moving in between heart beats?

Does blood stop moving in between heart beats or does it move continuously?
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Is the volume of blood pumped by the right and left ventricles the same?

Wikipedia says that the definition of stroke volume is: stroke volume (SV) is the volume of blood pumped from the left ventricle per beat Why the left ventricle specifically? Why aren't both ...
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Phenotype of a possible gene mutation

I have noticed multiple cases where patients had similar body characteristics : decreased ability to gain weight (slim) they are capable of sleep only 6 hours or less with normal functioning (...
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Why is Heart Rate Recovery after exercise reasonably well described by a mono-exponential decay?

I have been measuring my heart rate recovery after exercise and I see that it can be fit reasonably well using a single exponential: $HeartRate(t) = HR_{max} \times e^{-t/\tau} + HR_{resting}$ This ...
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Trouble in understanding graph of pressure time in different chambers of heart

In the book, it is written that from 0 s to 0.125 s-Atrial Systole; 0.125 s to 0.325 s-Ventricular Systole; 0.325 s to 0.6 s-Ventricular Diastole Why a bump is there from 0.125 s to about 0.175 s in ...
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How does increased resistance to flow decrease blood pressure?

I have recently encountered this question: Waldenström's macroglobulinemia is a condition which causes increased blood viscosity due to high protein content in the blood. How would Waldenström's ...
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The location of pulmonary valve in comparison with the aortic valve

According to most transverse diagrams of heart, the pulmonary valve, in comparison to the aortic valve, angles towards the left side a little bit. Take, for instance, the pulmonary valve is more ...
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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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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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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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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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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 ...
ANA negative's user avatar
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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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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 ...
Chemo-Mike's user avatar
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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? ...
Anju Maaka's user avatar
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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 ...
Vaibhav Raj's user avatar
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1 answer
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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 ...
Nicholas Hassan's user avatar
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377 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 ...
sourav thampan's user avatar
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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 ...
sourav thampan's user avatar
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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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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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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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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 ...
Lia Ahmed's user avatar
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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 ...
Navoneel Karmakar's user avatar
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1 answer
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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 ...
Dahen's user avatar
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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 ...
CoffeeIsLife's user avatar
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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 ...
John's user avatar
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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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