HAPP - Cardiovascular System III

01/17/2024

What is preload?

The end diastolic volume that stretches the ventricle to its greatest geometric dimensions under variable physiologic demand

What is afterload?

The tension or stress developed in the wall of the left ventricle during ejection

Preload is the end-diastolic volume created by ______

Venous return

Afterload is the sum of factors that oppose ___________ during systole

Ejection of blood

What is cardiac output?

The output of blood that is ejected, specifically the left ventricle

What is stroke volume?

A certain volume of blood that is ejected each contraction/heartbeat

Cardiac output equation

CO (ml/min) = SV (ml) x HR (1/min)

Stroke volume equation

SV = EDV (end-diastolic volume) - ESV (end-systolic volume)

What is the end diastolic volume?

The filled volume of the ventricle prior to contraction

What is the end-systolic volume?

The residual volume of blood remaining in the ventricle after ejection

What is venous return?

The flow of blood back to the right side of the heart

Venous return and cardiac output must be _____

Equal

Balance between cardiac output and venous return is achieved via _______

Frank Starling Mechanism

If there is imbalance between cardiac output and venous return, this suggest _______ (higher cardiac output)

The blood is backing up somewhere in systemic circulation

If there is an imbalance between cardiac output and venous return, this suggest that _______ (venous return is more)

There is back up in the pulmonary circulation

The Frank Starling Mechanism is the ability of the heart to _________

Change its force of contraction and therefore stroke volume in response to changes in venous return

What is the ejection fraction?

The fraction of blood ejected by the ventricle relative to its end-diastolic volume

Ejection fraction equation

EF = (SV/EDV) x 100

Ejection fraction is typically ________

Less than 60% (55-70%)

How is ejection fraction used clinically?

As a clinical index for evaluating the inotropic status of the heart and crucial for determining etiology of heart failure

What are the 2 subdivisions of the autonomic nervous system?

Sympathetic and parasympathetic

What is the sympathetic nervous system?

Fight or flight

What is the parasympathetic nervous system?

Rest and digest

Which subdivision of the ANS decreases heart rate?

Parasympathetic

Which subdivision of the ANS increases heart rate, contractility of myocytes, provides vasodilation for coronary vessels, and increases the amount of blood pumped?

Sympathetic

What is iontropy?

State of contractility of the heart muscle (how forceful)

What is chronotropy?

Refers to heart rate, frequency

What is lusitropy?

State of relaxation of the heart muscle

What is dromotropy?

Refers to the conduction velocity of the electrical impulse in the cardiac tissue

Which division of the ANS increases constriction of blood vessels?

Sympathetic

Which neurotransmitter is released by sympathetic activation?

Norepinephrine

Which neurotransmitter is released by parasympathetic activation?

Acetylcholine

Which receptor is the dominant sympathetic receptor in the heart?

Beta-1

Which receptor is the dominant parasympathetic receptor in the heat?

M2

What is an example of a non-selective beta blocker?

Propranolol

What is an example of a beta-1 selective beta blocker?

Metoprolol

Which adrenergic receptors are focused on?

Alpha-1, alpha-2, beta-1, beta-2

Which adrenergic receptor is the dominant receptor in the heart?

Beta-1

What are the effects of beta-1?

Increased heart rate, increased force of contraction, increased velocity of electrical conduction, increased renin release

Where is alpha-1 located?

Smooth muscle of blood vessel, bladder, eye, GI tract

What is the function of alpha-1?

Vasoconstriction; increased afterload in arterioles and increased preload in veins

Where is alpha-2 located?

Presynaptic sympathetic neurons, pancreas, platelets, smooth muscle of blood vessel

What is alpha-2 function?

Decreased norepinephrine release, decreased insulin release, increased platelet aggregation

Where is beta-2 located and what is its function? (Related to heart)

Smooth muscle; relaxation of blood vessels or vasodilation

Calcium is necessary for the contraction of ______

Vascular smooth muscle and myocytes

Calcium is necessary for the conduction of ______

AV and SV nodes

What are the 2 classes of calcium channel blockers?

Dihydropryidines and Nondihydropyridines

Which class of calcium channel blockers has more effect on blood vessels?

Dihydropyridine

What is ANS activity on cardiovascular system regulated by?

Vasomotor center

Where is the vasomotor center and what is its function?

Lower pons and medulla of the brain stem; integrates mechanisms regulating blood pressure

When the vasomotor center increases sympathetic activity to the heart, _________ activity is decreased

Parasympathetic (inverse relationship)

What 3 inputs are received from the vasomotor center?

Baroreceptor, chemoreceptor, low-pressure receptor

What stimulus do baroreceptors sense?

Blood pressure

What stimulus do chemoreceptors sense?

Blood gases

What stimulus do low-pressure receptors sense?

Blood volume

Baroreceptors respond to changes in _______

Smooth muscle fiber length

What do baroreceptors do when activated?

Reduce cardiac output by lowering heart rate and stroke volume along with peripheral vascular resistance and blood pressure

What factors affect cardiac output?

Heart rate and stroke volume

What are some factors that affect heart rate?

ANS, catecholamines, body temperature

What are some factors that affect stroke volume?

Length of diastole, venous return (preload), contractility, afterload, heart rate

What are factors affecting venous return?

Blood volume (proportional)

Sympathetic stimulation (proportional)

Skeletal muscle activity (contraction = increase VR)

What is the relationship between blood volume and blood pressure?

Proportional

What are the 3 mechanisms that regulate plasma volume?

ADH (anti-diuretic hormone), Renin-angiotensin, ANH (atrial natriuertic hormone)

Which receptor in the Renin-Angiotensin system produces vasoconstriction?

AT1

Aldosterone promotes sodium ________ in the kidney and potassium ________

Reabsorption; excretion

ADH promotes water _______ in the kidney by increasing aquaporin-2

Retention

What are functions of ANH?

Inhibition of renin-angiotensin aldosterone system

Increasing water and sodium excretion with ANH leads to _______

Lower blood volume/pressure