Human Cardio (NPB101L)

What is a Korotkoff sound?

tapping sounds that a partially occluded artery makes due to turbulent blood flow

What artery is involved in blood pressure reading?

Brachial artery

Is arterial or venous pressure higher?

arterial

What percentage of blood is in the arteries?

10-20%

What percentage of blood is in the veins?

70%

What is cardiac output (CO)?

volume of blood pumped by each of the ventricles per minute

What is the equation for cardiac output?

CO = HR x SV

What are the units for cardiac output?

L/min

What is compliace?

ability of a blood vessel wall to expand and contract passively with changes in prssure

What is the equation for compliance?

C=ΔV/ΔP

Which have higher compliance? Veins or arteries?

veins (10-20x greater)

When does vein collapse occur?

at pressures less than 10 mmHg

What is capacitance?

the volume of blood contained in a vessel for a given transmural pressure

What is the equation for capacitance?

capacitance = volume/transmural pressure (mmHg)

What is the relationship between compliance and capactiance?

vessels with high compliance also have high capacitance

What causes blood flow?

differences in pressure

What is vascular resistance?

a measure of how hard it is for blood to flow through a vessel

What is the equation for blood flow?

Flow rate (Q) = ΔP/Pressure (R)

What is the equation for resistance?

How is flow rate regulated?

changes in the radius of the vessel

What is Poiseuille's Equation?

What causes an increase in arterial volume?

increase in SV, CO, HR, or arterial resistance

What causes and increase in vein volume?

decrease in right heart pumping, reclining to upright body position change

What is MAP used to assess?

the average pressure in the arteries throughout the cardiac cycle (systole and diastole)

Why is MAP beneficial compared to just systolic/diastolic bp?

accurate representation of the overall perfusion pressure experienced by organs and tissues in the body

What is the equation for MAP?

MAP = 1/3 SBP + 2/3 DBP

What is the first step of the cardiac cycle?

ventricular filling

What happens during ventricular filling?

ventricles are relaxed, AV valves (mitrial & tricuspid) are open, andblood flows from atria to ventricles

What is the second step of the cardiac cycle?

isovolumetric contraction

What happens during isovolumetric contraction?

ventricles start contracting (no blood leaves yet), AV valves lose, semilunar valves are still closed

What is the third step of the cardiac cycle?

ventricular ejection

What happens during ventricular ejection?

ventricular pressure exceeds aortic/pulmonary pressure and semilunar valves open, blood is ejected out of ventricles, stroke volume leaves heart

What is the fourth step of the cardiac cycle?

isovolumetric relaxation

What happens during isovolumetric relaxation?

ventricles relax after ejection,semilunar valves close, AV valves haven't opened yet

What steps of the cardiac cycle are in systole?

2 & 3 (contraction and emptying)

What steps of the cardiac cycle are in diastole?

4 & 1 (relaxation and filling)

What is pulse pressure?

difference between systolic and diastolic blood pressures

What equation solves for pulse pressure (PP)?

PP = Systolic BP - Diastolic BP

What does pulse pressure provide information on?

force exerted by the heart each time it contracts to pump blood into the arteries

What is the elasticity and compliance of the arterial walls influenced by?

blood volume, heart rate and the function of the ventricles

How is hydrostatic pressure affected in the standing position?

added to areas below the heart and subtracted from areas above the heart

In a standing position, where is the vasculature pressure the highest?

near the feet

What happens when there is an increase in hydrostatic pressure in the lower body?

decrease in venous return, HR, CO, and arterial blood pressure

Why does standing up quickly sometimes result in dizziness?

inadequate cerebral blood flow

Where are the main baroreceptors that sense blood pressure located

carotid sinus and aortic arch

What will a fall in blood pressure will causing firing to do?

decrease

How does the medulla respond when baroreceptor firing decreases?

increasing sympathetic output

How is heart rate affected by an increase in sympathetic activity?

increase

What do sympathetic nerves release?

norepinehrine

What does norepinephrine bind to?

alpha1-adrenergic receptors on smooth muscle cells in the vessel walls (causing vasoconstriction)

What do sympathetic efferents to the heart release?

norepinephrine

What does norepinephrine from the heart bind to?

beta-adrenergic receptors

What does B-adergenic receptors increase?

HR and contractility (SV and CO)

What do parasympathetic nerves innervate?

only certain vascular bed and locations

What do parasympathetic nerves release?

acetylcholine

What does acetylcholine from the parasympathetic nerves bind to?

muscarinic AChR

How does the parasympathetic nervous system affects vessels?

vasodilation, decrease in HR and Contractility (SV and CO)

What causes an increase in blood pressure?

increase in baroreceptor firing, decrease in SNS, increase in PNS

How does a rise in vasodilation and drop in resistance affect blood pressure?

decrease blood pressure

What causes a decrease in blood pressure?

decrease firing rate of baroreceptors, decrease in PNS, increase in SNS

What is reactive hypermia?

reaction to a decrease in blood flow to a tissue with no change in the tissue's metabolism

What is the result of reactive hypermia?

transient higher than normal blood flow after removal of the decrease/restriction

What is the mechanism behind reactive hypermia?

build up of local metabolites that would normally be swept away with blood flow

What is active hyperemia?

increased blood flow caused by an increase in metabolic activity, such as exercise

What is the mechanism behind active hypermia?

release of metabolites causes vasodilation and increase blood flow

How does MAP respond to increase in HR and CO?

increase

What happens when active skeletal muscles release metabolites?

causes vasodilation, decreases TPR, and increases blood flow

How does SNS respond to exercise?

increase to inactive muscles, renal, and splanchnic and decreases blood flow

What does the skeletal muscle pump do?

increase venous return to sustain CO

Why does blood pressure increase to exercise?

O2 demand increases

How does heart rate respond to the diving reflex?

decreases (bradycardia)

What is the mechanism behind the diving reflex?

bradycardia and vasoconstriction at nonessenetial organs

What happens during the P wave of the electrocardiogram?

depolarization of atria

What happens during the QRS wave of the electrocardiogram?

depolarization of ventricles

What happens during the T wave of the electrocardiogram?

repolarization of ventricles

How is HR related to RR?

inversely proportional

What is the function of the Aorta (Elastic Artery)?

expands during systoles and recoils during diastole to maintain blood flow

What is the function of the muscular arteries?

regulates vasoconstriction and vasodilation to control blood flow and pressure

What is the function of the arterioles (resistance vessels)?

major site of vascular resistance, controls blood pressure

What is the function of the capillaries (exchange vessels)?

exchange of gases (O2,CO2), nutrients, and waste products with surrounding tissues

What is the function of the venules (small veins)?

drain blood from capillary beds

What is the function of the medium sized veins?

collect blood from venules and direct it to larger veins

What is the function of the large veins (capacitance vessels)?

serve as blood reservoirs (~60-70% volume). Transport blood directly to the heart

What is the purpose of muscle contraction?

When skeletal muscles contract (during walking, running, standing, etc), they compress the veins running through them and it forces blood back to the heart

What is the purpose of the one way valve?

open when blood is pushed upward by the contracting muscles, allowing blood to pump to the heart

How do muscles contracting affect valves?

it opens them

What is TPR?

total peripheral resistance, the amount of force exerted on circulating blood by the vasculature of the body

What are the factors that affect the force of total peripheral resistance?

length of vessels, diameter of vessels, viscosity of blood

Do longer blood vessels have more or less resistance?

more

How is vascular resistance related to the radius of the vessel?

inversely proportional to the fourth power of the radius of the vessel

Does blood with higher viscosity offer more or less resistance?

more resistance (thicker)

What are the factors that affect blood viscosity?

hemocrit (percentage of red blood cells in the blood), plasma protein concentration, and temperature

What is venous pooling?

gravity causes blood to pool in the lower extremities, reducing the volume of blood that returns to the heart

What is reduced stroke volume?

the reduced venous return leads to less blood being pumped out by the heart with each beat, which can initially lower blood pressure

What do baroreceptors monitor?

the stretch of arterial walls, which is proportional to blood pressure

How do baroreceptors respond when blood pressure drops?

less stretch = less action potentials being sent to the medulla oblongata = more SNS/less PNS

What does norepinephrine do?

causes smooth muscle in the walls of the arterioles and veins to contract, which increases vascular resistance and raises blood pressure

How does a decrease in diameter affect the arteries?

increase in resistance decrease in blood flow to the venous side

How does a decrease in diameter affect the veins?

decrease in capacitance, increase in pressure, increase in blood flow and venous return

How does the heart rate increase during the tilt table exercise?

SNS stimulates SA node to increase heart rate and maintain cardiac output and improve blood flow