2130 unit 4

parts of cardiovascular system

1) Heart → pump & makes pressure to move blood thru CV system

2) Blood vessels → tubes blood flows through (diff types & structures)

3) Blood → fluid carry gases, nutrients, hormones, immune cells, proteins, waste

What are the 4 primary functions of the cardiovascular system?

1) Distribution of blood to meet metabolic demands

2) Exchange/delivery of substances (nutrients, wastes, and hormones)

3) Heat regulation

4) Hemostasis (blood clotting)

5) Modulating inflamatory responses

what are the circuits of the CV system?

(1) pulmonary

• blood leave heart w pulmonary artery

• send blood to lungs (pick up O2, deliver CO2 waste pxd → return back to heart vis pulmonary veins)

(2) systemic

• blood leave heart w aorta & aortic branches

• send blood to organs & tissues in body EXCEPT lungs

• GOAL = pick up waste to deliver to lungs, deliver O2 from lungs

What is the path of the pulmonary circuit?

Heart (deoxygenated) --> lungs --> heart (oxygenated)

What is the path of the systemic circuit?

Aorta (oxygenated) --> all organs and tissues --> veins (deoxygenated) --> heart

• deliver blood back to R heart side w/ superior & inferior vena cava

How are the blood vessels organized?

Heart → arteries (break into…) → arterioles → capillaries

capillaries (combine to…) → venules → veins → heart

arteries vs veins

A → carry blood AWAY from heart

V → carry blood TOWARDS heart

capillaries

exchange occurs

EX → glucose, AAs, CO2 + O2 move in/out blood

how does blood move through the heart?

1. deliver blood to heart via superior & inferior vena cava (via systemic circuit)

2. blood enter R atrium (returned from all organs & tissue EXCEPT lungs)

3. blood enter R ventricle via RIGHT AV valve

4. R ventricle blood sends thru pulmonary arteries

   • go towards lungs w pulmonary circuit (L & R pulmonary arteries)

     • blood = DEC O2, INC CO2 (collected from systemic organs, O2 dropped & CO2 picked up)

   • uses pulmonary valve

   • pulmonary arteries deliver CO2 (exhaled) & O2 added (inhale) back to blood

5. pulmonary veins (2R, 2L) collect blood from diff areas on lungs & enter L side of heart

6. blood enter L atrium via pulmonary circuit

7. blood enter L ventricle via LEFT AV valve

8. L ventricle sends blood thru aorta

   • send blood to all organs but lungs w systemic circuit

     • blood =INC O2, DEC CO2 (collected blood from lungs, pick up O2 & drop CO2)

     • uses aortic valve

9. blood sent out to rest of body tissue/organs via systemic capillaries

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ventricles move blood to aorta & pulmonary arteries starting from apex → tip of heart & cascade contractions up towards atria

anatomy of the heart/organization of CV system

1. interventricular septum → wall divide L & R side prevent blood mix

   • left ventricular myocardium = L wall thicker bc INC pressure made to move blood thru systemic circuit bc gravity

2. atria → 2 top chambers

   • R = get blood from all organs/tissue except lungs via vena cava

   • L = get blood from lungs via pulmonary veins

3. ventricles → 2 bottom chambers

   • below atria

   • R = send blood via pulmonary arteries to lungs (DEC O2, INC CO2)

   • L = get blood via L atrium to aorta (INC O2, DEC CO2)

4. vena cava

   • #1 biggest vein

   • on R side

   • deliver blood back to heart from SYSM circulation

   • superior = blood from head/neck/chest/arms

   • inferior = blood from

5. pulmonary artery → deliver blood to lungs

6. pulmonary vein → 2L 2R collect blood from lungs & send to heart

7. aorta → blood sent to all tissues/organs except lungs

8. apex → bottom & start of where ventricles contract (send waves to top ventricles)

What are the 4 valves of the heart?

2 exits of ventricles → (1) aortic + (2) pulmonary valve

2 exits of atria → (3) R atrioventricular + (4) L atrioventricular (AV) valve

R atrioventricular (AV) valve

• prevent blood backflow from R ventricle → R atrium

• AKA tricuspid

L atrioventricular (AV) valve

• prevent blood backflow from L ventricle → L atrium

• AKA mitral

pulmonary valve (semilunar)

• has 3 cusps that fill, expand & close to prevent blood backflow into R ventricles from pulmonary arteries

• pass blood thru R ventricle → blood to pulmonary arteries → pulmonary circulation

aortic valve (semilunar)

• has cusps that fill, expand & close to prevent blood backflow into L ventricles from aorta

• pass blood thru L ventricle → blood to aorta → systemic circulation

what does a heart sound like?

• valves closing = change blood flow dynamic & make sound

• normal heart = lub (AV valve close, ventricle contract, blood go to atria) + dub (aortic & pulmonary valves close to send blood to ventricles)

• heart murmur = valve regurgitation, X close properly

• heart arrhythmia = irregualr heart contract

cardiomyocytes

• cardiac muscle cells

• allow for contraction & relaxation of heart

• diff types have diff APs

• (1) contractile cells

• (2) nodal/conducting cells

How are cardiomyocytes similar to skeletal myofibers?

• both striated (has myofibrils)

• need Ca++ to contract

• need mitochondria for ATP

• need AP

How are cardiomyocytes different from skeletal myofibers?

for cardiomyocytes:

• INC mitochondria

• make own AP from nodal cells (X motor neurons)

• branched (X cylindrical)

• has 1 nucleus

• Ca induced Ca release → extracellular fluid (via ion channels, down [] gradient to help SR release) + sarcoplasmic reticulum (store & release when AP occur

• electrical connected w gap junctions → cell comm. bc coupled together & shares info w gap junctions (channels let ions pass from 1 cell to another)

• intercalated discs → lock cells together w desmosomes proteins (hold cardiomyocytes together) & hold gap junctions

What are contractile cells?

• contract & relax to pump blood through the heart

What are nodal/conducting cells?

• Self-excitable cells by making own AP

• X contact → limited actin & myosin

• generate APs and spread electrical activity throughout heart

• EX → sinoatrial node. AV node, AV bundle, subendocardial branches

What is calcium-induced-calcium release in cardiomyocytes?

Calcium coming from extracellular fluid down its concentration gradient helps the release of intracellular calcium from the SR

• w/o = DEC Ca in cell from SR so Ca from outside induce Ca inside

• normal muscle cell only w SR = store Ca & release when AP

• cardiomyocyte = Ca from ECF + SR

Why are gap junctions important for normal heart functions?

allow ions to pass between cells so that contractile cells can communicate APs directly with each other

• electrically connect cells w special channels to let ions/Ca/Na thru

What are intercalated discs?

Connections that lock two cells together via desmosomes (glue proteins) where gap junctions are found

sinoatrial (SA) node

• in upper R side of R atrium

• move AP thru out heart so all of atria & contractile muscle of ventricle contract

• AKA pacemaker of heart → sets heart rate

• RMP unstable → self-excitable so contracts often (-60 lowest & -40 threshold)

F(x) =

• has APs w/ → pacemaker potential, depolarize & repolarize

• depolarization = Ca2+ voltage gated channels open @ threshold, move down [gradient] & INC (+) cell

• repolarization = potassium (K+) leaking out, INC (-) cell

pacemaker potential

• aka a graded potential to reach threshold

• Na+ & Ca2+ move into own ion channels & prevent K+ leave

• GOAL = cell INC (+) to make cell reach threshold

• THUS → INC Na+ Ca2+ in cell & DEC K+ out of cell

What are 5 ways the SA node AP differs from a neuron AP?

SA node has =

1. unstable RMP

2. higher threshold (~40 mV)

3. depolarization caused by influx of Ca++

4. X hyperpolarization

5. slower than a neuron

Why is the SA node AP slower than a neuron AP?

SA node w/o fast sodium-gated channels

THUS → depolarization mainly b/c rapid influx of Ca

ALSO good bc neurons fire INC often & X need heartbeat that fast

How is the SA node related to heart rate?

1 AP = 1 beat

Heart rate = # of AP conducted by SA Node

intrinsic = 100 bpm

resting = 70 bpm

what is resting heart rate?

bio M = 70 bpm

bio W = 80 bpm → smaller hearts

trained athlete = 40-60 bmp b/c INC efficient pump blood w muscle contract INC force & need DEC often occur

Why is nodal/conducting cardiomyocytes pathway important?

contractile cells in atria & ventricles need AP to move Ca from ECF inside & release SR Ca → then if enough [] in cytoplasm, contracts

• atria & ventricle CANNOT CONTRACT SIMOTANSEOUSLY

  • (1) atria contract = push blood into ventricles

  • (2) ventricle contract = push blood to lungs/body

• atria & ventricles X direct contact w gap junction → use R/L AV valve

How does an AP generated at the SA node spread throughout the heart?

1. SA node creates AP & send to neighboring cells w gap junctions

   • Ca come into nodal cells = cell INC (+), threshold hit, make own AP

2. AP travel to atrial cardiomyocytes

   • AKA contractile muscle cells & neighbor cells

   • atria depolarize = contract, move blood into AV node

3. AV node gets AP → send AP btwn atria & ventricle

   • AP slows down (let atria finish contract) & pass to ventricles to contract

   • conduction starts in the interventricular septum

4. AV bundle gets AP & send to bundle branches

   • in the interventricular septum

   • AV bundle split into bundle branches

5. L & R bundle branches get AP & travel as branches contract same time to L & R ventricles

6. AP then travel subendocardial branches

   • under surface of heart in ventricular muscle

   • send AP from apex of ventricles → top of ventricles

   • AP travel fast at apex → quick move w wave to walls of both ventricles

7. ventricular cardiomyocytes get AP

   • contractile & contract bottom up

   • send AP w gap junctions

   • contract when AP @ apex

can the SA node fail?

• intrinsic rate of SA node AP = fastest of all nodal/conducting cells

  • THUS → depolarizes & spreads AP before rest can fire AP

• SA node fail = AV node takes over (2nd fastest)

What is the maximum heart rate?

220 - age

how does the autonomic nervous system affect the SA node?

• get input from both branches

• PSYN = heart rate DEC 100 bpm (rest, relax)

• SYN = heart rate INC 100 bpm (fight, flight)

What system keeps the heart rate below 100 bpm?

parasympathetic system (PSYN of ANS)

• ACh bind to MUSCARINIC receptors on SA node

• THUS → DEC permeability of Na+ & Ca2+, INC permeability of K+

• THEN → DEC slope of pacemaker potential = INC time reach threshold = DEC heart rate

What system raises the heart rate above 100 bpm?

sympathetic nervous system (SYN of ANS)

• Norepinephrine binds to ADRENERGIC receptors on SA node

• THUS → INC permeability to Na+ & Ca++ ions

• THEN → slope of pacemaker potential INC = INC frequent fire = threshold reach faster = INC heart rate

SYN also releases epinephrine (adrenal gland) → hormone act of SA node, bind to adrenergic receptor & INC heart rate

what causes a change in the heart rate?

ANS innervates =

• AV node → cause change in heart rate & keep coordinated heart contraction

• ventricular cardiomyocytes → change force of ventricular contraction

Why does an AP slow down at the AV node?

To allow the atria to finish contracting before excitement is sent to the ventricles.

Why does an AP speed up at the subendocardial branches?

To allow the AP to spread throughout the heart and have a quick contraction of the ventricles.

What is bradycardia?

• heart rate is too low

• X enough blood & O2 delivered to tissue

• need pacemaker in surgery maybe

• dizzy, faint, tired

What is arrhythmia?

irregular heart rate

need pacemaker

How does a pacemaker work?

Acts as an SA node to stimulate heart to contract

THEN kick in when the heart starts beating irregularly

electrocardiogram (ECG/EKG)

• AKA 12 lead ECG

• give info abt electrical activity of the heart & how AP spread in heart

• help diagnose heart issues → arrhythmia, heart attack, conduction issues

how does a ECG work?

waves = P, T, QRS

• sums up all electrical events in heart b/c body fluids conduct APs

• from surface of skin → 10 sticky electrode disks placed on diff chest/arm/legs

• THUS → give 12 views of heart electrical activity from diff areas

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has 3 waves →

1. P wave = depolarization ARTIA

2. QRS wave = depolarization VENTRICLES

3. T wave = REPOLARIZATION ventricles

What does the P wave of an ECG indicate?

• Atrial depolarization

• measure TOTAL SUM of all AP occurs in atria

• find heart rate if measure time from 1 P wave to next

• RESULT = contraction

  • atria contract & pump blood to ventricles

PR interval

• time from P wave to start of QRS wave

• tell if electrical conduction normal btw atria & ventricles

QT interval

• tell cardiac conditions

What does the QRS wave of an ECG indicate?

• Ventricular depolarization & atria repolarization

• atrial repolarization masked by larger QRS activity w ventricle depolarization

• bigger wave than P wave → ventricles w INC mass = INC cells

• RESULT = contraction

  • ventricles contract, pump blood out of heart

What does the T wave of an ECG indicate?

• Ventricular repolarization

• “up” phase → during AP

Why is repolarization represented as a 'positive' wave in an ECG?

• direction of waves in an ECG based on direction of electrical activity towards a particular electrode

• heading TOWARDS electrode = increase in voltage = INC wave

• heading AWAY from electrode = DEC voltage = DEC wave

Why is the QRS wave much larger than the P wave?

The ventricles are much larger in mass than the atria and therefore have more cells depolarizing

What is systole?

measure of force exerted by cardiomyocytes on vessels when heart is contracting

top # on BP measurement

What is diastole?

measure of force exerted by cardiomyocytes on vessels in btwn heartbeats when heart is relaxing

bottom # on BP measurement

cardiac cycle

• sequence of events occur in EVERY SINGLE heartbeat

• go thru 5 phases of systole (contract) & diastole (relax) during 1 heart beat

isovolumetric ventricular systole

• ventricles start contraction BUT X pump blood out of heart yet

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• muscle → contraction

• ECG → QRS wave (starting during atrial contraction)

• Volume → X change

• Valves → all closed

• Pressure → ventricular INC dramatically BUT < aortic

ventricular systole

• ventricles contract & move blood out of heart → aorta (L ventricle) + pulmonary arteries (R ventricle)

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• muscle → contraction

• ECG → X new event

• Volume → DEC ventricular volume

• Valves → semilunar valves (pulmonary & aortic) open, AV valves closed

• Pressure → ventricular > aortic

isovolumetric ventricular diastole

• ventricles relax BUT X fill w/ blood

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• Muscles → relaxation

• ECG → T wave (starting during ventricular systole)

• Volume → X change

• Valves → all closed

• Pressure → DEC ventricular pressure, aortic > ventricular

late ventricular diastole

• ventricles relax & fill w/ blood from atria

• X fully filled & cont till atrial systole phase (little top up)

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• Muscles → relaxation

• ECG → X new event takes place

• Volume → INC ventricular volume

• Valves → AV valves open, semilunar valves closed

• Pressure → arial pressure > ventricular pressure

atrial systole

• atria contract = move blood to ventricles

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• Muscles → contraction

• ECG → P wave (starting during late ventricular contraction)

• Volume → INC ventricular volume

• Valves → AV valves open, semilunar valves closed

• Pressure → atrial pressure > ventricular pressure

does the atria relax/atrial diastole occur?

• YES → when ventricles contract & overpowered so X distinct phase

end systolic volume (ESV)

• V of blood remain in ventricles at end of systole AFTER ventricles contracted

• tells efficiency of the heart's pumping ability

What does a lower ESV indicated?

INC effective contraction

What does a higher ESV indicate?

DEC effective contraction

Heart dysfunction

end diastolic volume (EDV)

• volume of blood in ventricles RIGHT BEFORE ventricular contraction

What is stroke volume (SV)?

• volume of blood pumped out by the ventricles in each heartbeat

• influences cardiac output

What is the formula for stroke volume?

SV = EDV - ESV

INC stroke V = INC EDV

INC stroke V = DEC ESV

What is cardiac output (CO)?

• volume of blood the heart pumps per minute

• measures heart f(x) + overall CV health

• typical CO = 5-6 L/min

• INC CO when exercise → INC demand tissue to pump blood to meet INC metabolic demands & deliver O2 to exercise

What is the formula for cardiac output?

CO = HR x SV

CO = heart rate x stroke volume

Why is cardiac output important?

• essential 4 adequate blood flow to all tissues & organs

• ensures proper O2 & nutrients delivered to cell & waste products remove

what can INC cardiac output?

• INC # AP on SA node = INC heart rate

• INC activation of sympathetic activity on SA node → release norepinephrine, bind to adrenergic receptors, INC SA node pacemaker = INC depolarization = INC heat rate

• INC stroke V

• INC EDV, DEC ESV

what affects stroke volume?

• any factors affecting EDV & ESV

  1. ANS innervation → affect Ca2+ permeability

  2. preload on heart w/ EDV → affect contraction size

What is the distribution of muscarinic and adrenergic receptors on the ventricular muscles?

stroke volume based on contractile ventricle cardiomyocytes

• INC adrenergic receptors → for SYN

• DEC muscarinic receptors → for PSYN

UNLIKE →

• SA node/pacemaker = muscarine & adrenergic receptors

• AV node = muscarine & adrenergic receptors (control to speed/slow for coordinated heart contraction)

How is SV affected by activation of the SYN ANS?

1. SYN NS neurons innervate to ventricular cardiomyocytes

   • has adrenergic receptors on these contractile cardiomyocytes

   • able to bind norepinephrine (NTM) OR epinephrine (hormone)

2. activate adrenergic receptor on ventricular cardiomyocytes = INC Ca++ permeability

   • RESULT → INC Ca2+ in cytoplasm from SR = INC contraction strength

3. THUS → INC SV = INC pump blood each beat = INC CO

How is SV affected by the activation of the PYN ANS?

1. PSYN NS neurons innervate SOME contractile cardiomyocytes

2. PSYN release ACh when activated & binds to muscarinic receptors

3. RESULT → DEC Ca++ permeability = DEC Ca2+ into cytoplasm from SR = DEC contraction strength

4. THUS → DEC SV modestly = DEC CO

What is preload?

load on heart before contraction

load = volume of blood in ventricles (aka just EDV)

How does preload affect the SV?

• INC EDV (INC full heart) = INC stretch of contractile cells of ventricle = INC contraction force of cells upon systole

• THUS → INC amount of blood ejected from heart = INC SV

• protective mechanism (frank starling’s law)

What is Frank Starling's Law of the heart?

INC preload (INC full heart & INC EDV) = INC cardiac output

• w/o this, cause INC full heart w each beat

• THUS → INC SV maintain regular ESV

How can you increase EDV and preload?

VENOUS RETURN

• squeezing veins to force more blood back into heart (venous return)

What is the general pathway of blood flow through the systemic circuit?

Aorta --> arteries --> arterioles --> capillaries/body cells --> venules --> veins

• DEC venules than capillaries → capillaries combine to make venules

Which circulatory system contains most of the blood?

Systemic circuit (85%)

• each organ & tissue supplied by one of major arteries & smaller arteries/arterioles/capillaries/venules/smaller veins

• blood move back to heart w major vein & empty to R atrium w vena cavas

what is the distribution of blood in the body?

• total blood V = 4-6 → heart circulates entire blood V in 1 min

• most blood in systemic circuit (85%)

  • veins > arteries > capillaries

• little blood in heart & pulmonary circuit (15%)

What are the 3 layers of blood vessels?

Tunica externa, tunica media, and tunica interna.

What is the tunica externa?

Fibrous connective tissue: protects vessel, adheres it to surrounding tissues, and maintains its appropriate structure. Neurons and blood vessels are found here.

What is the tunica media?

Smooth muscle: contract or relax to various stimuli.

Elastin: allows vessels to stretch and recoil back to their resting shape.

Collagen: protein common in connective tissue.

What is the tunica interna?

Endothelial cells: important for normal vessel function.

How does the tunica media differ between arteries, arterioles, and veins?

Arteries: elastin is much more abundant than smooth muscle

Arterioles: smooth muscle is much more abundant than elastin

Veins: have some smooth muscle and elastin

How do the diameters of the different blood vessels compare?

Veins > arteries > arterioles = venules > capillaries

How do the wall thicknesses compared to diameters of the different blood vessels compare?

Arterioles > arteries > capillaries > venules = veins

What kind of vessels are arteries?

Distribution vessels: carry blood away from the heart.

What kind of vessels are arterioles?

Resistance vessels: carry blood from arteries to capillaries.

What kind of vessels are capillaries?

Exchange vessels: oxygen, nutrients, and ions are exchanged into cells while CO2 enters the blood.

What is the function of venules?

Carry blood from capillaries to veins.

What kind of vessels are veins?

Capacitance vessels: carry blood back to the heart.

How do the blood pressures of the different vessels compare?

Arteries > arterioles > capillaries > venules > veins

What is the main mechanism behind increasing EDV?

Exercising causes flight or fight response --> SNS innervates blood vessels and contraction of smooth muscle --> decreases diameter of vessels and forces blood forward

What is the skeletal muscle pump?

Veins squeezed by surrounding skeletal muscle --> muscle contracts and bulges --> squeezes vein and narrows diameter --> more blood returns to heart --> increases EDV, SV, and CO

Why is blood flow regulation important?

Ensures that different organs receive the appropriate amount of blood based on their needs. Maintains blood pressure. Increases or decreases heat loss from the body by redistributing blood.

Which organ receives the most blood?

Liver (25%).

Which two organs receive the least blood?

Heart and skin (5% each).