Cardiovascular System Tutorial Questions Flashcards
Why is it important to regulate blood pressure?
The blood pressure represents the driving force for blood flow.
Blood flow is mostly regulated by local changes to resistance (radius of arterioles)
However, if BP is not stable, then the regulation changes resistance to regulate flow becomes much more complicated.
BP can fluctuate dramatically. One major factor that affects BP is gravity.
How is the short-term control of blood pressure achieved?
MAP = CO x Total peripheral resistance -> HR x SR x Total peripheral resistance
Therefore BP is regulated by changes to HR, SV, Total peripheral resistance
Short term control of BP is by change in sympathetic and parasympathetic activation.
How is BP controlled in longer term?
Mostly by changes in blood volume (including BV -> inc. BP)
Balance of fluid intake and fluid output (Largely urination)
Controlled hormonally (vasopressin angiotensin 2 and aldosterone
These hormones increase salt and water reabsorption from the kidney -> increase blood volume (conserve water)
Define the following terms and explain the effects of an increase in each variable on the arterial blood pressure
Cardiac Output
Cardiac Output
Volume of blood ejected by ventricle per minute (CO = HR x SV) will increase BP
Define the following terms and explain the effects of an increase in each variable on the arterial blood pressure
Stroke Volume
Volume of blood ejected per contraction of ventricle.
Will increase BP
Define the following terms and explain the effects of an increase in each variable on the arterial blood pressure
Preload
Degree of stretch of ventricle prior to systole (end diastolic volume)
Will increase BP
Define the following terms and explain the effects of an increase in each variable on the arterial blood pressure
Contractility
Force generated by myocardium independent of fibre length (related to CA2+)
Increase in BP
Define the following terms and explain the effects of an increase in each variable on the arterial blood pressure
Afterload
Resistance against which the ventricle has to pump
Reduces SV (and therefore BP)
Define the following terms and explain the effects of an increase in each variable on the arterial blood pressure
Total peripheral resistance
Resistance to blood flow harder for blood to flow through arterioles
More blood in artery -> increase BP
Describe the structure of the arteries.
Arteries are principally elastic
Can stretch and recoil as each pulse of blood passes along them.
As they stretch, the increase in blood pressure during systole is lessened. As people age their arteries become less elastic, causing their systolic blood pressure to be higher.
As they recoil, the decrease in BP during diastole is also lessened.
The force BP is maintained by compressing the blood in the arteries.
This helps to maintain continuous blood flow. pulse pressure is reduced and pulsatile flow in reduced.
Describe the structure of the Arterioles
Arterioles have a large amount of smooth-muscle in their walls.
By resulting the contraction of the smooth muscle the arteriole radius and hence blood flow through the vessel can be controlled.
Overall arterioles make up the major components TPR
As the blood flows through the arterioles there is a significant reduction in blood pressure due to the energy loss.
In addition to the increase in HR, contractility, TPR there will also be what?
Venoconstriction
