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Flashcards in deck_623225 Deck (60):

What does the pumping action of the heart tend to do to vesicular volume?

Remove blood from viens, pumps blood to arteries


What does a decrease in cardiac output tend to do to vesicular pressure

Increase venous pressure, decrease arterial pressure


If total peripheral resistance falls, what will happens to vesicular pressure at a constant cardiac output?

Arterial pressure will fall, venous pressure will rise


If total TPR rises, what happens to vesicular pressure if cardiac output constant?

Arterial pressure will rise, venous pressure will fall


What is TPR inversely proportional to?

The body's need for blood


What is the effect of metabolic changes on CVS, such as eating a meal?

TPR will change and generate signals in the form of changes in arterial and venous pressure


What is demand led pumping?

If the body needs more blood, the heart needs to pump more to meet the demand. This is expressed as changes in arterial and venous pressure


What is cardiac output?

Stroke volume x heart rate


Define stroke volume

The difference between end diastolic volume and end systolic volume. Amount of blood ejected at each heart beat


What is end diastolic volume determined by?

The filling of the heart, as during diastole the ventricles fill as venous pressure drives blood into them


What is end systolic volume?

The volume of blood in the left ventricle at the end of systole


What is end disastolic volume?

The volume of blood in the left ventricle at the end of diastole (filling)


To what pressure do the ventricles fill in diastole?

Until intraventricular pressure matches venous pressure `


What is the relationship between venous pressure and heart filling?

High the venous pressure, the more the hear fills in diastole


What is the relationship between venous pressure and ventricular volume known as?

Ventricular compliance curve


Why will TPR resistance change if metabolism changes?

Due to vasodilator metabolites produced proportionally


What are the three factors which determine how much the ventricles fill during diastole?

1) Venous pressure2) Heart rate3) Total peripheral resistance


What is starlings law?

The more the heart fills, the harder it contracts (up to a limit).There harder it contracts, the bigger the stroke volume


Define pre load

The end diastolic stretch of the myocardion, determined by venous pressure


Define after load

Fore necessary to expel blood into the arteries - determines what happens during systole


What does a rise in venous pressure lead to?

A rise in stroke volume, due to increased ventricular filling


What does the yellow slope on this graph indicate

INSERT GRAPH Contractility of the ventricle


What does the red circled point indicate?

The critical value - No further expansion possible as muscle can stretch no further, due to squashing/damage, Ventricles are at full capacity


Define contractility

The ability of the cardiac muscle fiber to shorten, causing muscle contraction in response to an electrical impulse


What does the green line indicate?

Sympathetic activity, causing an increase in contractility


What is the term for the effect noradrenaline and adrenaline have on the heart, and what does it do?

Positive inotropic effectIncrrease stroke volume at a given pre-loa and after-load


What is force of contraction determined by?

End diastolic volume Contractility


What are the two things which determine how much ventricle empties depend on?

How hard the ventricles contractHow hard it is to eject blood


How can difficulty of blood ejection be modified?

Depends mainly on TPR - The harder it is to ject blood, the higher the pressure rises in the arteries


What factor does after-load determine?

The effect of a given force of contraction during systole


What happens to systolic volume and stroke volume if arterial pressure falls?

End systolic volume falls and stroke volume rises


What happens to stroke volume if venus pressure rises?

Stroke volume will rise


What are baroreceptors?

Stretch receptors located in carotid sinus and aorta which sense arterial pressure and determine autonomic outflow to the heart


Where do baroreceptors send signals?

To the medulla oblongata


What happens if a baroreceptor detects a fall in arterial pressure

Increase heart rateIncrease contractility


How would a baroreceptor increase heart rate?

By reducing parasympathetic activityBy increasing sympathetic activity


How would a baroreceptor increase contractility?

By increasing sympathetic activity


What is the bainbridge reflex?

Sensed in right atrium - A rise in venous pressure causes a rise in heart rate, via reduced parasympathetic activity


Describe in general terms the role of the medulla of the brain in CVS reflexes

A collection of neurones which modify cardiac behabiour and circulation via the ANS


How does the medulla oblangata change heart rate and contractility?

Heart rate - Alters the firing of the SAN to change heart rateContractilty - Uses sympathetic nervous system


What does a rise in venous pressure cause?

Increase stroke volumeIncrease heart rateIncreased cardiac output


If arterial pressure falls, what happens to blood flow resistance in certain tissues?

The resistance to blood flow through certain vascular beds such as the skin and gut will rise


What happens to venous capacitance if arterial pressure falls?

Venous capacitance will be reduced by veno-constriction


What are the consequences of an increase in heart rate?

Cardiac output risesSubsequent decrease in venous pressure Reduced diastolic filling due to reduced venous pressureReduced stroke volume


What happens to TPR if you are eating a meal?

Increased activity of gut leads to local vasodilationReduce TPR


What does reduced gut TPR during a meal lead to?

Rise in venous pressure - increased COFall in arterial pressure - Rise in hr, so COVenous pressure reduced by extra pumping of heart, and arterial pressure raised


What happens in circulatory system in exercise?

Massively increased demand for bloodMuscle pumping forces extra blood back to the heart


Why can't exercise produce response in same way as gastric?

Becase speed and scale of changes in venous pressure tend to overload the CVSHuge increase in venous pressure, massive decrease in arterial


Why is the huge increase in venous pressure during exercise dangerous?

Tends to overfill the heart and pushes the ventricles onto the overloaded section of the starling curve. Risk of pulmonary oedema because the outputs of the right and left ventricle cannot be matched.


What does the starling curve provide?

Matching stroke volume to right and left side of heart


How does pulmonary oedema come about as a result of overfilled heart during exercise?

Left heart cannot respond to right due to increased venous return, so blood accumulates in the lungs. Water forced out, causing decreased lung function via oedema.


How is overfilling of the ventricles prevented in exercise?

Increase in heart rate, which occurs as exercise begins. When venous pressure starts to rise, heart rate already high.


What effect does standing up have on the CVS?

Blood pools in the superficial veins of the legs because of gravity, causing fall in central venous pressure


What are the consequences of standing up and the subsequent decrease in central venous pressure

Central venous pressure falls, so cardiac output falls.Subsequent decrease in arterial pressureFall detected by baroreceptors, triggering rise in heart rate.


What are the three results of of a fall in arterial pressure detected by baroceptors on standing?

Rise in heart rateVaso constriction of skin and gut to increase TPRVeno constriction to drive blood to heart


What condition do older people develop which accentuates effects on blood pressure when standing up?

Postural hypotension


What is the direct effect of haemorrhage?

Decreased venous pressure, causing fall in cardiac output


What does the fall in cardiac output after haemorrhage due to decreased venous pressure cause?

Arterial blood pressure to fall, which is detected by baroreceptors.Heart rate increases, as does TPR.


What does the rise in heart rate and TPR as a result of haemorrhage cause to happen?

Further lower venous pressure - Rise of heart rate pumps blood out, TPR helps arterial pressure but lowers venous.Thus, veno constriction must take place.


Describe the effects of a long term increase in blood volume

* Kidney controls blood volume * If blood volume increases for days > venous pressure increases * Increased cardiac output * Increased arterial pressure (hypertrophy of smooth muscle) * Increased TPR * Increased arterial pressure (new set value) * Hypertension (treatment: diuretic/vasodilator)