PGY 206: Exam 3 Cardiovascular System

functions of the circulatory system

respiratory, nutritive, excretory, regulation, and protection

respiratory function of the cardiovascular system

to transport oxygen and carbon dioxide

nutritive function of the cardiovascular system

to carry absorbed digestion products to the liver and to tissues

excretory function of the cardiovascular system

to carry metabolic wastes to kidneys for excretion

hormonal regulation function of the cardiovascular system

to carry hormones to target tissues to produce their effects

temperature regulation function of the cardiovascular system

to divert blood to cool or warm the body

blood clotting protection function of the cardiovascular system

to prevent blood loss when vessels are damaged

immune protection function of the cardiovascular system

includes leukocytes (WBCs) that protect against disease causing agents

components of the cardiovascular system

blood, heart, and blood vessels

components of the lymphatic system

lymphatic vessels and lymph nodes

plasma

straw-colored liquid consisting of water and dissolved solutes, mostly sodium

plasma proteins

constitute 7-9% of the plasma

albumin

produced in the liver, accounts for 60-80% of plasma proteins and maintains colloid osmotic pressure needed to pull water from interstitial fluid to capillaries, and maintains blood pressure

alpha and beta globulins

plasma proteins that transport lipids and fat soluble vitamins

gamma globulins

plasma proteins that are lymphocytes which are antibodies that function in immunity

fibrinogen

plasma protein that is an important clotting factor, converted to fibrin during the clotting process

erythrocytes

red blood cells that are flattened disks with large surface area to promote diffusion of gasses, lack nuclei and mitochondria so they have a short life (replaced every 3-4 months), contains hemoglobin which contains iron, and heme helps transport oxygen from the lungs to the tissues

leukocytes

white blood cells, contain nuclei and mitochondria, granular (help detoxify foreign substances) and agranular (produce antibodies)

platelets

fragments of megakaryocytes, lack nuclei, important for blood clotting by releasing seratonin to vasoconstrict and reduce blood flow to that area

intrinsic blood clotting pathway

exposes subendothelial tissue (collagen) to the blood, exposure to collagen activates plasma protein factors to form fibrin 

extrinsic blood clotting pathway

damaged tissue releases through thromboplastin (tissue factor NOT part of the blood) which initiates a short cut to formation of fibrin

blood clotting features

extensive cascade of clotting factor mostly produced by the liver, and common to both pathways is the conversion of fibrinogen to fibrin by thrombin

pulmonary circulation

path of blood from the right ventricle through the lungs and back to the heart

systemic circulation

path of oxygen-rich blood pumped to all organ systems to supply nutrients

cardiac muscle

striations, muscle fibers, intercalated disks, contains nucleus (similar to skeletal muscle but contains intercalated disks)

cardiac muscle cells

made up of sarcomeres which contain actin and myosin, contracts via sliding-filament mechanism, these are activated by calcium transients, joined by gap junctions (electrical synapses), APs occur spontaneously, cells behave as one unit

myocardial action potential

the depolarization comes from the gap junction, then rapid upshoot occurs (voltage-gated Na+ channels open causing inward diffusion of Na+), plateau phase (membrane potential stayed depolarized but voltage-gated Ca2+ channels open causing inward flow of Ca2+), rapid repolarization (voltage-gated K+ channels open slowly causing rapid outward diffusion of K+ to repolarize cells)

excitation-contraction coupling in the heart muscle

APs of myocardial cells stimulates opening of voltage-gated Ca2+ channels in sarcolemma, Ca2+ diffuses into cell stimulating the opening of Ca2+ release channels in sarcoplasmic reticulum (SR) by a Ca2+ induced Ca2+ release mechanism, Ca2+ binds to troponin and stimulates contraction

characteristics of myocardial APs

refractory periods last almost as long as contraction does, voltage-gated Na+ must “reset” at repolarized potentials before they can open again, not tetanus (due to long refractory period allowing heart muscle to relax)

heart pumping sequence

Cardiac depolarization begins in SA node in the right atria, this depolarization spreads to other (left) atria, and then it passes to the ventricle septum to the bottom of the heart and along the walls of the ventricle, then atria contract and push blood in to the ventricle, ventricles contract and push blood up and out large arteries

electrocardiogram (ECG)

measures the electrical activity of the heart per unit time, does not measure flow of blood

P wave of ECG

atrial depolarization

QRS complex of ECG

ventricular depolarization, atrial repolarization

T wave of ECG

ventricular repolarization

cardiac cycle

refers to the repeating pattern of contraction and relaxation of the heart

systole

phase of contraction

diastole

phase of relaxation

end-diastolic volume (EDV)

total volume of blood in the ventricles at the end of diastole

stroke volume (SV)

amount of blood ejected from the ventricles during systole, also calculated by EDV-ESV

end-systolic volume (ESV)

amount of blood left in ventricles at the end of systole

lub

first sound produced by the closing of the AV valves during isovolumetric contraction

dub

second sound produced by the closing of the semilunar valves when pressure in ventricles falls below the pressure in the arteries

atrial systole

step 1 of cardiac cycle, atrial contraction occurs and pushes 10-30% more blood into the ventricle

isovolumetric contraction

step 2 of cardiac cycle, contraction of the ventricle causes ventricular pressure to rise above atrial pressure, AV valves close, then ventricular pressure is less than aortic pressure, semilunar valves are closed, volume of blood in ventricle is EDV

ejection

step 3 of cardiac cycle, contraction of the ventricle causes ventricular pressure to rise aortic pressure (approx. 80 mmHg), semilunar valves open, then ventricular pressure is greater than atrial pressure, AV valves are closed and the volume of blood ejected is SV

isovolumetric relaxation

step 4 of cardiac cycle, ventricular pressure drops below aortic pressure and back pressure causes semilunar valves to close, AV valves are still closed, volume of blood in the ventricle is ESV

rapid filling of ventricles

step 5 of cardiac cycle, ventricular pressure decreases below atrial pressure, AV valves open, rapid ventricular filling occurs

what phase of the cardiac cycle does this represent

systole

what phase of the cardiac cycle does this represent

diastole

what part of the heart does this represent

artery

what part of the heart does this represent

left ventricle

types of blood vessels

arteries, arterioles, capillaries, venules, veins

tunica externa

outer layer of connective tissue of arteries and veins

tunica media

middle layer of smooth muscle of arteries and veins

tunica interna

innermost simple endothelial cell layer of arteries and veins

elastic arteries

numerous layers of elastin fibers between smooth muscle, they expand when the pressure of the blood rises acting as a recoil system when ventricles relax

muscular arteries

are less elastic and have a thicker layer of smooth muscle, diameter changes as BP rises and falls

arterioles

contain highest % of smooth muscle, greatest pressure drop and greatest resistance to flow

capillaries

smallest blood vessels, only 1 endothelial cell thick, these provide direct access to cells permitting the exchange of nutrients and wastes

continuous exchange in capillaries

adjacent endothelial cells tightly joined together, contain intercellular channels that permit passage of molecules (not proteins) between capillary blood and tissue fluid, found in muscles, lungs and adipose tissue

fenestrated exchange of capillaries

wide intercellular pores, provides greater permeability, found in kidneys, endocrine glands, and intestines

discontinuous (sinusoidal) exhange of capillaries

large, leaky capillaries found in liver, spleen and bone marrow

capillary hydrostatic pressure

blood pressure exerted against the inner capillary wall, promotes movement of fluid into tissues (filtration)

colloid osmotic pressure

blood pressure exerted by plasma proteins, promotes reabsorption into circulatory system (capillaries)

net blood pressure

hydrostatic pressure (Pcap) - colloid osmotic pressure (π)

venules

formed when capillaries unite

veins

contain little smooth muscle or elastin, capacitance vessels (blood reservoirs), contain 1-way valves that ensure blood flow to the heart

arrythmia

abnormal heart rhythyms

bradycardia

heart rate slower than 60 beats per minute

tachycardia

heart rate faster than 100 beats per minute

flutter

extremely rapid rates of excitation and contraction of atria or ventricles, can lead to fibrillation

fibrillation

contractions of different groups of myocardial cells at different times, makes coordination of pumping impossible, ventricular fibrillation is life-threatening (atrial is not)

atrial fibrillation

most common type of irregular heartbeat (no P wave on ECG), occurs when abnormal firing of electrical impulses cause atria to quiver/fibrillate, treated by cardioversion, ablation, blood thinners, anti-arrhythmic medications

murmurs

produced as blood regurgitates through valve flaps due to damaged or defective valves, can be caused by: damaged valves from antibodies made in response to infection or congenital defects, mitral (bicuspid) valve becomes thickened and calcified, damage to papillary muscles, or valves do not close properly

septal defects

typically congenital, holes form in the septum between the left and right sides of heart, may occur in interatrial or interventricular septum, causes blood to pass from left to right during contraction

atherosclerosis

most common form of ateriosclerosis (hardening of the arteries), happens in 50% of US population, plaque builds up in small arterioles increasing resistance to blood flow, occurs from hypertension, smoking, high cholesterol, and diabetes which damage endothelial cell wall

process of atherosclerosis

monocytes become macrophages and engulf lipids to transform into foam cells, smooth muscle cells synthesize connective tissue proteins where smooth muscle cells migrate to tunica interna and proliferate forming fibrous plaques.

lipoproteins

carry lipids in the blood

Low-Density Lipoproteins (LDLs)

produced in the liver, carry cholesterol to the arteries, high in peopel who eat a diet rich in saturated fats

High-Density Lipoproteins (HDLs)

carry cholesterol away from the arterial wall, protect against atherosclerosis, low in sedentary people, can be increased by drugs like statins fibrates, or niacin

Coronary Artery Bypass Graft surgery

treats blocked heart arteries by creating new passages for blood to flow to your heart muscle. It works by taking arteries or veins from other parts of your body (grafts) and using them to reroute blood around the clogged artery

Ischemia

oxygen supply to tissue is deficient, most common cause is atherosclerosis of coronary arteries

angina pectories

substernal pain

myocardial infarction

changes in ST segment of ECG, can be tested by increased blood levels of creatine phosphokinase (CPK), lactate dehydrogenase (LDH), and troponins (T and I).

ischemic heart disease or MI symptoms

chest discomfort, pain and discomfort in other areas (one or both arms, the back, neck, jaw, or stomach, shortness of breath, other signs may be breaking out in a cold sweat, nausea, or lightheadedness. More common in women

ischemic heart disease or MI symptoms more common in women

pain and discomfort in back, neck, or jaw, shortness of breath, and nausea

hypertension (HTN)

(130/80 mm Hg) blood pressure in excess of normal range for age and gender

primary/essential hypertension

result of a complex or poorly understood process (most common)

secondary hypertension

result of a known disease process

dangers of hypertension

patients are asymptomatic until damage occurs, increases workload of the heart, congestive heart failure, damaged cerebreal blood vessels (can cause stroke)

treatments of hypertension

modification of lifestyle (stop smoking and alcohol intake, weight reduction, reduced Na+ intake, more K+ intake), medications (diuretics, beta blockers, calcium antagonists, ACE inhibitors, Angiotensin II-receptor antagonists)

heart failure

cardiac output is insufficient to maintain blood flow required by body (to meet metabolic demand), increased venous volume and pressure

causes of heart failure

myocardial infarction, congenital defects, hypertension, aortic (semilunar) value stenosis, disturbances in electrolyte concentrations (K+ and Ca2+)

treatment for heart failure

vasodilators and diuretics

mean arteriole pressure (MAP)

represents the average arterial pressure during the cardiac cycle (closer to diastolic pressure as the period of diastole is longer than systole), depends on how much blood is being pumped by the heart (cardiac output) and diameter of the arterioles

equation for mean arterial pressure

mean arterial pressure = cardiac output x total peripheral resistance

auscultation (art of listening)

indirect method of correlating blood pressure and arterial sounds

laminar flow

normal blood flow, blood in the central axial stream moves faster than blood flowing closer to the artery wall, smooth and silent

turbulent flow

vibrations produced in the artery when cuff pressure is greater than diastolic pressure and lower than systolic pressure

measurement of MAP

blood pressure cuff is inflated above systolic pressure, occluding the artery. As cuff pressure is lowered, the blood will flow only when systolic pressure is above cuff pressure, producing the sounds of Korotkoff. Korotkoff sounds will be heard until cuff pressure equals diastolic pressure, causing the sounds to disappear