Afterload Flashcards
Define the relationship between mean arterial pressure, cardiac output and total peripheral resistance Define the term afterload Outline the factors that influence arterial blood pressure Describe the reflex control of arterial blood pressure Describe the mechanisms that regulate vascular tone Briefly outline the processes leading to lymph formation
Define systolic arterial pressure
Peak pressures in the arteries when the left ventricle is ejecting blood during ventricular systole
Define diastolic arterial pressure
The residual pressure in the arteries when the left ventricle is filling during ventricular diastole
What is the equation for establishing mean arterial pressure?
DBP+(SBP-DBP)/3
Define afterload
The peak ventricular wall tension during systole.
This is determined by the resistance to ejection from the ventricle.
Increased systemic vascular resistance results in increased afterload
What equation can be used to determine blood flow?
Flow= driving force/resistance
What receptors are responsible for responding to changes in pressure?
Baroreceptors
What receptors are responsible for responding to changed in chemical imbalances?
Chemoreceptors
Name the specific region of the internal carotid that contains baroreceptors?
Carotid sinus
What is found within the carotid body
Chemoreceptor zone
Which of the cranial nerves innervates the carotid sinus?
Glossopharyngeal
How is a impulse stimulated in the carotid sinus nerve?
Pressure increases in the artery leading to an increase in the diameter. The elastic conversion of the tunica media amplifies the increase in diameter (detecting length not pressure).
The baroreceptor endings in the adventitia stretch causing mechanical distortion of the nerve endings.
This leads to a discharge of action potentials and a impulse in the carotid sinus nerve
Define compliance
A term used to describe how easily a structure can be stretched - the higher the compliance the easier to stretch
How does age effect compliance?
Compliance decreases with age due to increased collagen and decreased elastin
The heart cannot eject a given stroke volume into a rigid arterial system as readily as into a more compliant system
What is required in order for the heart to maintain stroke volume against a increased afterload?
To maintain stroke volume at increased afterload requires the heart to contract more forcefully (increased contractility)
Sympathetic nervous system influence is required to maintain cardiac output (inotropic effect)
Where is the main site of resistance within the circulatory system?
The arterioles (the greatest fall in pressure occurs across the arterioles; the smallest across the arteries.
Arteriolar radius controls TPR and thus increased blood pressure is a consequence of arteriolar narrowing
