Ch. 20 - The Heart Flashcards by Maia Lindo

Where is the heart located?

mediastinum; mostly left of midline

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C/C fibrous and serous pericardium

F - protects and anchors heart; prevents overstretching

S - parietal layer fuses with F percardium; visceral layer in direct contact with heart

*serous fluid found in between parietal and visceral pericardia

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What are the layers of the heart wall?

epicardium, myocardium, endocardium

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What are sulci?

grooves on outside of heart that separate chambers; contain BV and fat

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What is an auricle?

pouch-like structure on anterior surface of each atrium; helps atria hold greater vol of blood

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Which chambers receive?

atria

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Which chambers pump?

ventricles

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Where does the R atrium receive blood from? Where does it pump blood to?

superior/inferior vena cava, coronary sinus; right ventricle via tricuspid valve (right AV)

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Where does the R ventricle receive blood from? Where does it pump blood to?

right atrium; into pulmonary trunk via right semilunar valve (pulmonary valve)

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Where does the L atrium receive blood from? Where does it pump blood to?

oxygenated blood from lungs; left ventricle via bicuspid valve (left AV)

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Where does the L ventricle receive blood from? Where does it pump blood to?

left atrium; aorta via left semilunar valve (aortic valve)

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AV valves prevent back flow from…

…ventricles into atria

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Semilunar valves prevent back flow from…

….arteries into ventricles

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What triggers the opening and closing of heart valves?

pressure changes; not neurons/AP!

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What are valves composed of?

dense irregular CT covered with endocardium

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How do AV valves prevent back flow?

papillary muscles attached to valve cusps by chordae tendinae; chordae prevent valve cusps from opening into atrium

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What are semilunar valves composed of?

3 moon-shaped cusps

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When do semilunar valves open?

when pressure in ventricles exceed pressure in arteries

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What is the function of coronary arteries?

supply myocardium cells with fresh nutrients and O2; branch off aorta

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What is the function of coronary veins?

collect waste from cardiac muscle and drain into coronary sinus, which then empties into R atrium

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What is systole and diastole?

S - contraction

D - relaxation

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What does the cardiac cycle consist of?

systole + diastole of both atria followed by systole + diastole of both ventricles

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What are characteristics of cardiac muscle?

branched, intercalated discs connected by gap junctions and desmosomes, involuntary, striated, single central nucleus

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How do cardiac muscle sarcomeres differ form skeletal muscle?

more mitochondria (25% of cell vol)
T-tubules wider but less abundaent
SR less prominent; need Ca2+ from outside cell

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How do cardiac muscles produce ATP?

- aerobic cellular resp a. at rest: use FA, glucose b. during exercise; use lactic acid - creatine phosphate when something is wrong!

What are the role of autorhythmic fibers?

- generate spontaneous AP that trigger heart contractions 1. act as pacemaker, setting baseline rhythm of electrical excitation that causes contraction 2. form conduction system; propagates AP through heart muscle

What is the sinoatrial (SA) node?

- cluster of cells in wall of R atrium - repeated spontaneous depolarization; no stable resting potential - triggers contraction of both atria

What is the atrioventricular (AV) node?

- located in b/t 2 atria (atrial septum) | - signal is slightly delayed at AV node

Why is the delay of the signal at AV node important?

atria have to contract then relax; ventricles have to contract then relax

What is AV bundle?

- where signal can be transmitted from atria and ventricles - send signal down ventricular septum to apex - Purkinje fibers conduct signal up ventricle wall - triggers contraction of ventricles

What are the 3 phases of an AP in a ventricular contractile fiber?

1. rapid depolarization 2. plateau 3. repolarization: closure of Ca2+ channels and K+ outflow when additional K+ channels open **prolonged refractory period

What occurs during depolarization phase?

Na+ inflow as Na+ channels open; resting membrane potential is -90mv

What occurs during plateau phase?

- Ca2+ inflow from outside cell/SR as Ca2+ channels open --> Ca2+ binds to troponin - K+ outflow as K+ channels open

What occurs during repolarization phase?

- Ca2+ channels close - K+ channels open to let K+ out of cell - muscle contraction ceases --> relaxation!

Is tetanus possible in cardiac muscle cells?

no because potential is maintained

What occurs at atrial and ventricular diastole?

4 chambers are relaxed; passive filling of blood into heart

What occurs at atrial systole, ventricular diastole?

atria contract; blood pushes into ventricles

What occurs at atrial diastole, ventricular systole?

atria relaxes; ventricles contract; blood pushes out of heart

What does an electrocardiogram record?

spread of AP through heart

What are the recognizable waves in an EKG that appear with each heartbeat?

1. P wave - atrial depol (contraction!) 2. QRS complex - rapid ventricular depol (contraction!) 3. T wave - ventricular repol (relaxes)`

Describe the AP propagation through the heart

1. electrical impulse from SA node to walls of atria; atria contract= 2. impulses reaches AV node; delay 3. bundle branches carry signal from AV node to apex 4. signal spreads through ventricle walls; ventricles contract

What causes the sound of a heartbeat?

turbulence of blood flow caused by closure of valves

What is the first heart sound?

- AV valves close soon after V systole begins

What is the second heart sound?

- SL valves close near beginning of V diastole

What does the R-R interval tell you?

length of time a heartbeat takes

What kinds of information can you get from an ECG?

how muscles are conducting AP; can detect valve malfunction

What is cardiac output? (CO)

vol of blood ejected from a ventricle each minute

What is stroke volume? (SV)

vol of blood ejected by the ventricle with each contraction

What is heart rate? (HR)

number of beats per minute

What is the formula for cardiac output?

CO = SV x HR

Depending on activity level, what are normal levels of cardiac output?

Resting - 5L/min Mild exercise - 10L/min Intense exercise - 19.5L/min

How many times can the average person increase their CO resting value? How about a top endurance athlete?

4-5 times; 7-8 times

What is a cardiac reserve?

difference between person's max cardiac output & cardiac output at rest

What hormones influence heart rate?

epinephrine, norepinephrine

How are specific ion concentrations crucial to heart rate?

1. increased K+ blocks AP generation 2. increased Na+ blocks Ca2+ 3. increased Ca2+ speeds heart rate and force of contraction

What other factors influence heart rate?

age, gender, physical fitness (athletes have lower rate), body temp (increased temp leads to increased heart rate)

What are the 3 factors of regulation of stroke volume?

preload, contractility, afterload

What is preload?

degree of stretching more blood filling chamber --> more stretching --> greater force of contraction

What is the amount of blood in chamber dependent on?

venous return and duration of diastole (relaxation)

What is contractility?

force of contraction of myocardium

C/C positive and negative inotropic agents

+ : increase contractility by increasing Ca2+ inflow - : decrease contractility by decreasing Ca2+ inflow/increasing K+ outflow

What does inotropic mean?

drugs acting on contractility fibres

What is afterload?

amount of pressure required to open semilunar valves

What causes high afterload?

high BP

What leads to increased stroke volume?

increased preload + contractility, decreased afterload

Ch. 20 - The Heart Flashcards

(65 cards)