chapter 17 cardio Flashcards by sheree weems

The heart is located in the

mediastinum of the thoracic cavity, specifically in the pericardial cavity.

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right side of the heart receives deoxygenated blood, pumps blood to the lungs to offload CO2 and pick up O2

Pulmonary Circuit

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left side of the heart receives oxygenated blood, pumps blood throughout body to supply O2 to tissues and pick up CO2

Systemic Circuit

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Blood Flow through the Heart

Right atrium → tricuspid valve → right ventricle → pulmonary valve → pulmonary trunk → lungs → pulmonary veins → left atrium → mitral valve → left ventricle → aortic valve → aorta → systemic circuit → inferior and superior vena cava

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functional blood supply to the heart muscle

Coronary circulation

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The heart is surrounded by the two layered pericardium that are called

Fibrous pericardium

Serous pericardium

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what is the name of superficial layer of the heart

Fibrous pericardium

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what is the name of the inner serous membrane that produces serous fluid of the heart

Serous pericardium

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– lines inner surface of the fibrous pericardium

Parietal pericardium

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adheres to the heart wall, considered the superficial layer of the heart wall

Visceral pericardium (epicardium)

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The heart wall consists of three layers

epicardium
myocardium
endocardium

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the layer of heart that (visceral pericardium) - the serous membrane that covers the heart

epicardium

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the layer of heart that is composed of cardiac muscle tissue

myocardium

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the layer of heart that is simple squamous epithelium that lines the chambers of the heart

endocardium

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contain noncontractile pacemaker cells

nodal tissue

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upper right atrium, pacemaker of the heart

Sinoatrial (SA) node

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– located where the interventricular septum meets the atria o Slight delay in conduction occurs here o Only electrical connection between the atria and ventricles

Atrioventricular (AV) node

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located primarily in the superior portion of the interventricular septum

Atrioventricular (AV) bundle (bundle of His)

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continue through the interventricular septum to the apex

Right and left bundle branches

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from the apex into the walls of the ventricles

Purkinje fibers

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generates impulses (“fires”) 60-75 times/minute

Sinoatrial (SA) node

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senses the arrival of the action potential, delays the impulse approximately 0.1 second and then responds by “firing” its action potential

Atrioventricular (AV) node

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Impulse passes from atria to ventricles via the

atrioventricular bundle (bundle of His)

AV bundle splits into two pathways in the

interventricular septum (bundle branches)

carry the impulse toward the apex of the heart

Bundle branches

carry the impulse to the heart apex and ventricular walls

is “a recording of the electrical activity of the heart” as the heart undergoes repeated cardiac cycles

ECG = electrocardiogram (EKG)

Lasts about 0.08 sec  Represents the electrical activity associated with depolarization of the atria the atria then undergo contraction

P wave

Also lasts about 0.08 sec; this is in spite of the much more massive ventricles that become depolarized  Associated with firing of the AV node and rapid conduction of AP by bundle of His, bundle branches, and Purkinje fibers, as well as the depolarization then of the remaining ventricular myocardium precedes and leads to ventricular contraction (ventricular systole)

QRS complex:

Caused by ventricular repolarization  Lasts ~ 0.16 sec (repolarization takes much longer than depolarization of the ventricle)  is more spread out and has a lower amplitude than QRS wave

T Wave

Time from beginning of atrial excitation to beginning of ventricular excitation

P-R Interval

Time interval during which the AP is in a plateau state  Entire ventricular myocardium is depolarized

S-T segment

Beginning of ventricular depolarization through ventricular repolarization.

Q-T Interval

Is stimulated by nerves, however is self-excitable (automaticity)  Contracts as a unit  Has a long (200 ms) absolute refractory period

Cardiac Muscle Contraction:  Heart muscle

Cardiac muscle contraction similar to

skeletal contraction

what is the difference between a skeletal and cardiac muscle with the means of stimulation

Skeletal:  Each skeletal muscle fiber must be stimulated to contract by a nerve ending  Cardiac:  Cardiac muscle cells are self-excitable  Can initiate their own depolarization in a rhythmic way (autorhythmicity – can pace the heart)

what is the difference between a skeletal and cardiac muscle the Organ versus motor unit contraction

 Skeletal:  All cells of a given motor unit are stimulated to contract at the same time.  Cardiac:  Depolarization wave is transmitted across the heart from cell to cell via ion passage through gap junctions, tying all cardiac muscle cells together into a single unit.

what is the difference between a skeletal and cardiac muscle the Length of absolute refractory period

 Skeletal:  Lasts 1-2 ms  Cardiac:  Lasts ~200ms, nearly as long as the contraction  This helps to prevent tetany which would stop the heart’s pumping action.

inexcitable period when Na+ channels are still open or are closed/inactivated.

refractory period

Duration of AP and contractile phase is much greater in in the ? then the ?

cardiac than in skeletal muscle.

refers to all events associated with blood flow through the heart

Cardiac cycle

contraction of heart muscle

Systole

relaxation of heart muscle

Diastole

Ventricular filling – mid-to-late diastole Heart blood pressure is ? as blood enters the ? when the AV valves are open, then the? ends?

low---atria and flows into ventricles atrial systole occurs diastolic volume

Isovolumetric Contraction Phase artia does what? Rising ventricular pressure results in ? blood vol. is

low in closing of AV valves constant

Ventricular ejection phase opens? end of?

semilunar valves | systolic volume

Isovolumetric relaxation – early diastole Ventricles do what? Backflow of blood in aorta and pulmonary trunk closes what? is a brief rise in aortic pressure caused by backflow of blood rebounding off semilunar valves

relax semilunar valves dicrotic notch

On right side, pressure differs, as this is the

pulmonary circuit

requires less pressure to circulate blood through the lungs that the systemic circulation requires to force blood through all of the other blood vessels in the body, which has to oppose greater gravitational forces

pulmonary circulation

But both sides of heart eject the ?

same blood volume with each heartbeat

Amount of blood pumped out of a ventricle during one contraction. is called

stroke volume

The 3 most important factors affecting stroke volume:

preload, contractility, afterload

the stroke volume that has amount ventricles are stretched by contained blood Slow heartbeat and exercise increase venous return to the heart, increasing SV  Blood loss and extremely rapid heartbeat decrease SV

preload

cardiac cell contractile force | is the increase in contractile strength

Contractility

Increase in contractility comes from:

Increased sympathetic stimuli  Certain hormones  Ca2+ and some drugs

contractility Agents/factors that decrease contractility include:

Acidosis  | Calcium channel blockers

the stroke volume that has back pressure exerted on valves by blood in the large arteries leaving the heart those with high blood pressure, SV can be significantly decrease

afterload