Unit 3: Cardiovascular Physio Flashcards by Sasha K.

Define “circulation”.

the movement of extracellular fluid (plasma, RBC/WBC/platelets) from region to region within the body

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Define “internal environment”.

interstitial fluid

environment that our cells are in direct contact with

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Describe the major functions of the cardiovascular system.

Transport
~oxygen from lungs to interstitial fluid surrounding cells everywhere in body
~nutrients from digestive tract to interstitial fluid everywhere
~also will pick up metabolic waste and deposit it into interstitial fluid > sites of elimination (Ex) Co2 > lungs). most other wastes removed by kidneys
~also transport of hormones, heat

~Self-repair mechanism (blood clotting)

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Identify the three major components of the cardiovascular system and relate each to the major functions described

Blood- transportation, defense, etc.
Blood vessels (lymph vessels)- allow blood to travel
heart- pumping blood

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Describe each of the three major types of blood vessels - both anatomically and functionally.

Arteries/arterioles- resistance vessels
~Thick, muscular tubes that carry oxygen-rich blood from heart > body.
~Act like highways, delivering blood with a strong push from the heart.
Capillaries- exchange vessels
Driving forces: diffusion, filtration, osmosis
~Tiny, thin-walled vessels where blood exchanges oxygen, nutrients, and waste with body cells.
~Act like small bridges, allowing essential substances to pass between blood & cells.
Veins- capacitance vessels
influence how much blood returned to heart (venous return)
~medium tubes carry oxygen-poor blood back to the heart.
~Act like rivers, relying on muscle contractions and valves to keep blood flowing upward.

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Diagram/describe the flow of blood through the heart, naming all of the chambers and valves along the way.

Add to your diagram a description of where the blood leaving the heart goes and where the blood entering the heart comes from

Vena cava
right atrium
right AV / tricuspid valve
right ventricle
right semilunar valve
pulmonary trunk
pulmonary veins
left atrium
left AV / mitral valve
left ventricle
left semilunar valve
aorta

> systemic circulation
Arteries, capillaries, veins

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Name the blood vessels and describe the oxygen content of the blood in each blood vessel and heart chamber.

vena cava > right atrium = low oxygen

right ventricle > pulm. arteries = low oxygen

exchange Co2 and O2

left atrium > left ventricle = high oxygen

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What is the primary function of the heart?

to pump blood to supply oxygen and nutrients to your body’s parts, like muscles and organs, and to carry away waste products.

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What is the function of the atria?
Of the ventricles?

atrium- receives blood returning to the heart from blood vessels

ventricle- pumps blood out into blood vessels

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What is the function of the valves? What causes the valves to open and close?

to permit blood to flow forward while preventing it from flowing backward

Heart valves open and close in response to changes in pressure within the heart chambers during its pumping cycle.

When the heart contracts, higher ventricular pressure closes the AV valves to prevent blood from returning to the atria; increased pressure forces the semilunar valves to open, enabling blood to exit the heart.

As the ventricles relax, lower pressure causes the semilunar valves to close, preventing backflow from the arteries. This pressure difference leads to the opening of the AV valves, allowing blood to flow from the atria to the ventricles

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Describe the microscopic structures that make the heart function as a pump.

Intercalated Discs: Special connections between cells that help them work together.
gap junctions- cells function in unison

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Describe the transmission of electrical energy through the conduction system of the heart.

What type of tissue is the conduction system made of?

cardiac muscle tissue

The transmission of electrical energy through the heart’s conduction system begins with the SA node generating an impulse in the atria, causing them to contract. The impulse then travels to the AV node, delaying briefly to allow ventricular filling. It continues through the bundle of His and spreads via Purkinje fibers, triggering ventricular contraction and the pumping of blood. The heart then undergoes repolarization and relaxation before the next cycle begins.

The sinoatrial (SA) node serves as the initial source of the action potential (AP), which subsequently spreads throughout the atrial myocardium, reaching all atrial cells. This propagation activates the atrioventricular (AV) node, prompting the generation of another AP in its cells. After a brief delay, the AP travels down the AV bundle (Bundle of His), which then divides into left and right bundle branches, featuring side branches that allow adjacent cells to depolarize. Near the apex, each branch of the AV bundle ascends along the ventricular walls, stimulating neighboring cells, particularly the Purkinje fibers, to initiate their own action potentials through cell-to-cell communication.

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Describe the excitation-contraction-coupling mechanism of myocardial contraction.

Electrical Signal: electrical signal starts in the heart’s natural pacemaker (SA node) and spreads through the heart.

Calcium Release: The signal causes calcium to be released inside heart muscle cells.

Calcium Activation: Calcium activates proteins in the muscle cells, including troponin.

Muscle Contraction: Activated troponin allows actin and myosin (proteins in muscle cells) to interact and cause muscle contraction.

Sliding Filaments: Actin and myosin filaments slide past each other, shortening the muscle cell and causing contraction.

Relaxation: calcium is pumped back out of the cell, and the muscle relaxes.

This process repeats with each heartbeat, allowing the heart to pump blood efficiently. The electrical signal triggers the release of calcium, which then activates the muscle contraction machinery, leading to the rhythmic beating of the heart.

excitation - AP
Ap = membrane
contraction = interaction between thin and thick myofilaments

diffusion of calcium

in myocardial cells, diffusion of Ca originates from SR or extracellular… calcium diffuses until it binds to troponin-tropomyosin complex; shape change ; binding site on actin uncovered, myosin heads can latch on..

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Define diastole and systole.

Diastole:
heart’s “relaxation” phase.
During diastole, the heart fills with blood as its chambers relax.
heart “resting” and getting ready to pump blood.

Systole:
heart’s “contraction” phase.
During systole, the heart’s muscular walls contract, squeezing blood out.
heart “working” to pump blood out to the body or lungs

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Describe the pacemaker action potential.

What is the mechanism of “autorhythmicity” in the pacemaker tissues?

The ability of myocardial autorhythmic cells to generate AP in absense of input from NS results from their unstable membrane potential (starts at -60 mV and slowly drifts up toward threshold)

This is AKA pacemaker potential, rather than resting membrane potential, bc it never “rests” at a constant value

Whenever pacemaker potential depolarizes to threshold, the autorhythmic cell fires an AP

—3 phases
no resting phase

in between AP = pacemaker potentil [slow depolarization due to sodium funny channels and slow ca channels], voltage gated channels open (2 types- fast Ca cause rapid depolarization to produce AP, as they close, K channels open > repolarization

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Describe the different stages of the myocardial action potential.

What ions / ion channels are responsible for the different stages?

How does the myocardial action potential relate to the phases of contraction (twitch)?

Phase 0- depolarization
Na channels open

Phase 1- initial repolarization
Na channels close

phase 2- plateau
Ca channels open; Fast K channels close

Phase 3- rapid repolarization
Ca channels close, Slow K channels open

Phase 4- resting membrane potential

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Describe the different waveforms of the electrocardiogram.

What specifically is represented by each waveform?

Identify the points in time when the SA and AV nodes begin to depolarize.

P wave- electrical activity in the atrium
[not a measure of AP, but measures electrical differences between 2 recording electrodes at the time AP are moving through myocardium of atria]
atrial depolarization

P wave- spread of atrial depolarization
initiation p wave - SA node depolarizes
peak to end - spread of depolarization

QRS wave- [complex] - represents electrical excitation within ventricles
[Q wave, large R wave, small S wave]
ventricular depolarization

QRA begining - AV node depolarizes
spread of ventricular depolarization

T wave- return to resting state within ventricles
Ventricular repolarization

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Define bradycardia and tachycardia.

bradycardia- abnormally slow heart rate

tachycardia- abnormally fast heart rate

[detectable by ECG or taking pulse]

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Define and describe each of the different degrees of AV nodal block (aka heart block).

1st degree- long P-R interval

2nd degree- more than 1 P wave per QRS

3d degree- independent P wave & QRS wave rhythms

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Describe the pattern of depolarization known as a circus rhythm.

Explain how a circus rhythm can be generated and sustained.

What pattern would be observed on an ECG.

Fibrillation is a consequence of circus rhymthm

circus rhythm- self-re-generating AP that transits through the myocardium in ventricles or atrium

Pattern: no evidence of P or QRS or T wave.. just irregular wave form; or just may be a flat line

initiation due to ectopic pacemaker and this can be due to hyperexcitability of cells due to hypoxia or excess K, traumatic injury

Cells contracting but not working together..
can be problematic

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Describe the forces that lead to “exchange” between
capillaries and interstitial fluid.

Pay particular attention to the “exchange” of oxygen, carbon dioxide and water.

it takes place either by movement between endothelial cells or movement through the cells

Pg. 496

in capillary, there are 2 types of movement - molecular driven by diffusion (concentration gradient)
and water movement driven by 1) pressure / filtration 2) osmosis
these 2 oppose

filtration out of capillary dominates
pressure drops as you move down capillary length
at the venous end, osmotic movement of water into capillary dominates

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What factors influence the movement of water between capillaries and interstitial fluid?

What effect would altering any of these factors have on water distribution?

pressure and osmosis

high blood pressure = pressure gradient dominant over osmotic&raquo_space;> water builds up in tissue

high salt diet - water moves into blood until pressure balances it out.

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Describe two different ways to determine cardiac output.

[flow]
how much blood is pushed out of the heart

1) MAP / TPR
total peripheral resistance
[diamater of blood vessel is big factor]

2) Stroke volume (SV) x heart rate (HR)

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What is the principal regulatory factor contributing to peripheral resistance?

diameter of the blood vessels

[systemic circuit]

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Describe the (intrinsic) Frank-Starling law of the heart. How does this phenomenon help increase cardiac output to match increased physical activity? How does it contribute to maintaining a balanced output from the left and right ventricles?

if venous return increases, this results in increased end-diastolic volume [volume of ventricle will be greater at the end of the diastolic phase if there is more blood flowing into it] The ventricle will contract with force proportional to its volume [length-tension relationship] The heart contracts as forcefully as it needs to eject the volume it receives, in the form of its end-diastolic volume

Describe the innervation of the heart by the parasympathetic and sympathetic systems.

~innervated by both the parasympathetic and sympathetic systems. ~During rest, heart primarily under parasympathetic control, ~During activity or stress, it falls under sympathetic control.

Describe the effect and the mechanism of parasympathetic stimulation on the heart.

Chronotropic effect slows HR by slowing SA node activity (AP generation)

Describe the effect and the mechanism of sympathetic stimulation on the heart.

~chronotropic: ---increases HR by increasing AP generation by SA node ~inotropic effect: affects strength of contraction---increases force of contraction by influencing calcium influx into cell

Describe how blood flow (distribution) is regulated intrinsically by carbon dioxide.

metabolic vasodilation- blood vessels respond intrinsically to metabolic byproducts in their vicinity Increased skeletal muscle activity during exercise > skeletal muscles generate Co2 as byproduct > Co2 stimulates metabolic vasodilation of blood vessels in the muscle > increased blood flow to muscle Co2 levels increased > vasodilation

Describe the effect of the parasympathetic and sympathetic regulation of blood vessels.

Sympathetic stimulation : blood vessels within muscles can vasoconstrict (decreases blood flow) in the viscera and vasodilate (enhance blood flow) in the muscle Parasympathetic Regulation: Parasympathetic nerves mainly relax blood vessels in specific areas, like the digestive system; helps increase blood flow to those areas, which is useful for digestion, etc

Describe the baroreceptor reflex.

baro = pressure reflex that helps to regulate blood pressure If BP drops too low, not enough flow/pressure to keep blood moving BP always being monitored; if too low, will drive BP up by increasing HR/ Stroke volume/ resistance predominantly measured within baroreceptors found in carotid sinus; also some in the aorta [pressure sensitive sensory receptors that will detect stimulus > graded/AP generation > sensory neurons carry info towards CNS]

Describe the different factors that affect venous return to the heart.

Venoconstriction Venodilation respiratory pump- decreases pressure in thorax as lungs expand in inhalation; moves blood up from abdomen; at exhalation, there is increased pressure and this pushes blood along in thoracic cavity ~during inhalation, pressure in thoracic cavity decreases, vena cava expands, blood in other veins flow towards vena cava leading to heart. Expiration - slows flow. Venous return increases during inhalation. Skeletal muscle pump - skeletal muscles moving/squeezing/ contracting on veins which exert pressure on veins, pushing blood along ~centered around veins having valves , veins squeeze out blood, valves ensure it is squeezed towards heart

Formula for pulse pressure

systolic - diastolic pressure

Formula for MAP (mean arterial pressure) [pressure difference]

Pulse pressure = systolic - diastolic pressre MAP = diastolic pressure + 1/3(pulse pressure)

Although many myocardial cells are capable of auto-rhythmicity, 1 group of cells in the right atrium predominates over all others:

SA node (sinoatrial node)

since body fluids contain a high concentration of __________,, they are electrically conductive

electrolytes

Blood flows from high to low concentration/pressure, a pressure difference generated by:

contraction and relaxation of heart

The amount of blood flow, called ____________________, is a product of the balance between pressure differences generated by the heart and resistance generated by blood vessels

cardiac output

Average cardiac output is

5-6 L/min

Specialized exchange vessels are

capillaries

Arteries and arterioles are also known as

resistance vessels [carry blood away from heart, towards capillaries]

The only portion of the vascular system where exchange between blood and tissues can occur:

capillaries = exchange vessels

Veins and venules are also known as

capacitance vessels [receive blood from capillaries, return to heart via veins]

The __________, when heart relaxed, is the lowest point of pressure in the entire circulatory system, so all blood will move towards it

ventricle

The valve between the atrium and ventricle is the

Right atrioventricular valve AKA tricuspid valve

When the heart is contracting, the right AV valve (tricuspid) will be

closed

A vein carries blood _________ the heart

towards

Arteries carry blood _______ _______the heart

away from

The resting stage is AKA

diastolic phase

Diastole means

not contracting [atrium and ventricles relaxed] blood flowing from high to low pressure atria > ventricle

Basic 6 steps of the mechanical cardiac cycle

Atrial systole begins Atrial systole ends, atrial diastole begins Ventricular systole- 1st phase 2nd phase early late

When the atria contracts, blood is pushed :

into ventricle [expands 20-30%] [no vessels]

The first heart sound is caused when

AV valves close [atriventricular] "Lub"

the 2nd heart sound is caused by

semilunar valves close [vibration of walls > sound] "Dub"

Pacemaker cells have a unique set of voltage gated channels [including HCN/ funny channel] , so they have a unique:

action potential pattern

What is the primary function of the valves in the heart?

to permit blood to flow forward while preventing it from flowing backward

The plateau phase of a myocardial cell action potential (indicated by 2 in the image above) is caused by movement of:

calcium ions into the cell

Pacemaker tissues like the SA and AV node are made of :

muscle cells.

Excitation is linked to contraction by:

calcium ions entering the cell through voltage gated calcium channels calcium ions released from the sarcoplasmic reticulum

The rapid depolarization phase (indicated by B in the image above) of a pacemaker cell action potential is caused by movement of:

calcium through fast L-type channels

The delay between closure of the AV valves and opening of the SL valves results in a phase called:

isovolumetric phase

Opening of the atrioventricular valves occurs when

pressure inside the ventricle is less than the pressure inside the atrium

Electrical excitation of the heart originates from ______1_______ and spreads through the heart by ______2_________

1- sinoatrial node 2- gap junctions and specialized muscle cells called the conduction system

The valves of the heart open and close because:

blood pressure pushes them open and closed

The unique ion channel(s) in the SA node that are responsible for the SA nodes autorhythmicity (segment A) due to its hyperpolarizing threshold:

HCN channel Slow T-type calcium channel Sodium “Funny” channel

blood exiting ventricles is exiting at a very high pressure and will enter

into arteries [oxygenate or not]

_________ are very muscular with thick elastic bands in their structure, giving them strong resistance to high pressure blood entering them

Arteries

What would happen to water distribution between the blood and the tissues if all of the plasma proteins were removed from the blood?

water would accumulate in the tissues

Water moves from capillary blood into interstitial spaces due to _____ and back into capillary blood due to _____.

filtration; osmosis

Where is most of the blood found in a person at rest?

in the veins

AV nodal block (aka heart block) is commonly a result of:

AV node degeneration

blood flow = _______/________

volume/time

Parasympathetic stimulation alters heart rate by:

stimulating potassium (K+) channels to open and slow T-type calcium (Ca2+) channels to close

Describe the effect of end-diastolic volume on stroke volume An increase in end-diastolic volume stretches ventricular muscle cells to lengths closer to optimum, increasing:

the strength of contraction and thereby increasing stroke volume.

Regulation of the heart (or any organ or tissue) by neural input, circulating hormones, or any other factor originating from outside the organ is referred to as ________ control.

extrinsic

An increase in heart rate can be mediated through :

a decrease in parasympathetic activity and/or an increase in sympathetic activity

Which of the following could occur as a result of an increased heart rate: total peripheral resistance to increase blood pressure to increase cardiac output to decrease stroke volume to increase

blood pressure to increase

Sympathetic stimulation alters heart rate by speeding up the rate of:

pacemaker potential depolarization

The Frank-Starling Law of the Heart states that increased end diastolic volume will result in :

stronger contractions (and increased stroke volume)

Sympathetic stimulation alters heart rate by: increasing: stimulating:

increasing the number of calcium channels that open increasing the number of sodium channels that open stimulating G-protein coupled receptors with norepinephrine stimulating a cAMP second messenger transduction pathway

the pressure created in the ventricles is called the _________________ because it is the force that drives blood through the blood vessels

driving pressure

a decrease is blood vessel diameter is AKA

vasoconstriction

an increase in blood vessel diameter is AKA

vasodilation

the heart is composed mostly of cardiac muscle, AKA

myocardium

the aorta and pulmonary trunk (artery) direct blood from the heart to :

the tissues and lungs

The venae cavae and pulmonary veins:

return blood to the heart

each cardiac cycle has 2 phases:

diastole- cardiac muscle relaxed systole- muscle contracts

stroke volume is the volume of blood pumped per:

contraction

The opening and closure of the atrioventricular and semilunar valves is driven by

differences in pressure on either side of the valve

Not every atrial contraction is followed by a ventricular contraction this is describing what?

second-degree heart block

The second heart sound is produced by:

closure of the semilunar valves

The ECG can be used to determine a lot about heart function, but what specific activity within the heart is the ECG actually measuring and displaying?

electrical activity

There is a delicate balance between capillary blood pressure and plasma osmolarity. Decreased plasma osmolarity would result in:

decreased movement of fluid from the tissues into the blood

In conditions where the ventricles are no longer controlled by the SA node, but are controlled exclusively by the AV bundle what would you expect? [3d AV nodal block ?]

very slow palpated pulse no pulse change in response to ANS stimulation independent P wave and QRS wave patterns on an ECG

Describe why atrial repolarization is usually not detected on a normal ECG It occurs :

at the same time as the QRS complex.

What may be observed on the ECG of a patient with 1st degree AV nodal block?

a PR interval longer than 0.2 seconds a regular rhythm

What ECG waveform represents contraction of the ventricles?

none of the ECG waveforms represent contraction

Sympathetic stimulation alters heart rate by:

speeding up the rate of pacemaker potential depolarization

What's happening during 0 and 1?

1- Na+ channels open 2- Na+ channels close

What's happening during 2 and 3?

3- Ca2+ channels open; Fast K+ channels close 4- Ca2+ channels close; Slow K+ channels open

What's happening during 4?

resting potential

Describe the mechanisms utilized by epinephrine which results in cardiac rate increase

Epinephrine binds to receptors that post ganglionic NS stimulates (B1 receptors on SA node and myocardium) ; g protein coupled receptors; when binds here, G protein alpha subunit latches onto adenylate cyclase > ATP converted into CAMP > acts on sodium funny / HCN channels and slow/ T type calcium channels >>> pacemaker potential depolarizing faster> threshold quicker > AP

Epinephrine & caffeine: effect on heart rate and force?

increased HR increased force

Acetlycholine & pilocarpine & nicotine: effect on heart rate and force?

decreased HR no effect on force

calcium (CaCl2): effect on heart rate and force?

no affect on HR increased force

Potassium (Kcl): effect on heart rate and force?

decreased HR decreased force