The Heart Flashcards by chrissy Finucane

What is the pericardium?

A double walled sack around the heart

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Parietal pericardium

Lines the internal surface of the fibrous pericardium

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Visceral pericardium

Lines the surface of the heart

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Homeostatic imbalance

Pericarditis

Inflammation of the pericardium, rough serous membrane, heart rubs against the pericardial sac. visceral and parietal pericardia stick together

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Homeostatic imbalance

cardiac tamponade

Large amounts of inflammatory fluid compress the heart, limiting it’s pumping action (it must be drained)

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Three layers of the heart wall

Epicardium- visceral layer of the pericardium

Myocardium- Cardiac muscle layer forming bulk of heart, fibrous skeleton of the heart

Endocardium- Endothelial layer of the inner myocardial surface

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The way heart muscle is bundled allows it to function as a syncytium, what does that mean?

It “works together” as a single coordinated unit

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What is the difference between the pulmonary circuit and the systemic circuit?

They going opposite direction one drop off oxygen, the other picks up the oxygen.

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Coronary circulation

Functional blood supply to the heart muscle itself

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Anastomoses

Also known as collateral routes, ensures blood delivery to the heart even if major vessels are obstructed

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Homeostatic imbalance

angina pectoris

(Choked chest) thoracic pain caused by deficiency and blood delivery to myocardium

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Homeostatic imbalance

myocardial infarction

A heart attack caused by lack of oxygen due to blockage of the coronary system, areas of cell death are repaired with scar tissue

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Why is damaged cardiac muscle not replace?

Because muscle cells do not undergo mitosis because they are missing centrioles

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Heart valves

Atrioventricular valves- Tricuspid, bicuspid(mitral)

semilunar valves: pulmonary and aortic

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Heart valves function

They ensure unidirectional blood flow through the heart

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Incompetent valve

Makes swishing sound, blood backflows or regurgitates through partially open valve

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Stenotic valve

High-pitched sound or click because valvular opening is narrowed so bloodflow is restricted

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Cardiac muscle

Striated, short, fat, branched and interconnected. connective tissue endomysium acts as tendon and insertion

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Intercalated discs

Made of gap junctions and desmosomes. anchor cardiac cells together and allow free passage of ions

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Autorhythmic cells

Create the action potential which travel through the gap junction to depolarize the contractile cells (slow sodium Fast calcium)

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Contractile cells

Fast sodium slow calcium

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What is the difference between autorhythmic cells and contractile cells

Autorhythmic set the pace uses calcium

Contractile cells like the rest of the heart use sodium to contract

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Why must there be a 0.1 second delay between as SA and AV nodes

Because all heart chambers cannot squeeze at the same time

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Sequence of electrical excitation to the heart

Intrinsic

SA node generates impulse
Atrial excitation begins
Impulse delayed at AV node
Impulse passes to heart apex
Ventricular excitation begins
Ventricular excitation complete

Arrhythmias

Irregular heart rhythm

Fibrillation

Rapid out of step contraction where control of heart rhythm is taken away by SA node fibrillating ventricles are useless pumps. defibrillization is needed to shock heart and allow SA node to reestablish rhythm

Ectopic focus

SA node is replaced by another pacemaker like AV node

Junctional rhythm

Pace set by AV node usually 50 beats

Extrasystole

Hyperexcitable region of the heart causes premature contractions, before SA node initiates regular contraction premature ventricular contraction PVC are most problematic

Heart block

Inability of ventricles to receive impulses from AV node. Total heart block-Ventricles forced to beat at own slow autorhythmic rate. To slow for adequate circulation Total or partial heart block a pacemaker can recouple atria to ventricles

Extrinsic innervation of the heart

Sympathetic nerve- speeds up (100) | parasympathetic nerve- vagus nerve tells it to slow down

Why does parasympathetic nerve dominate control over the heart?

Parasympathetic controls because it maintains the heart rate

Cardiac output problem

CO= HR x SV The amount of blood pumped by each ventricle in one minute

Stroke volume problem

SV= EDV - ESV Stroke volume = end-diastolic volume - end-systolic volume EDV is The amount of blood collected in a ventricle during diastole ESV Is the amount of blood remaining in a ventricle after contraction

Stroke volume | preload

The amount the ventricles are stretched by contained blood

Stroke volume | Contractility

Cardiac cell contractile force due to factors other than EDV

Stroke volume | afterload

Back pressure exerted by blood in the large arteries leaving the heart

Frank-starling law

Preload is a critical factor in controlling stroke volume, cardiac muscle exhibits a length tension relationship. at rest, cardiac muscle cells are shorter than optimal length

Factors influencing stroke volume positive inotropic agents Negative inotropic agent

Positive- increase and contractility Ex increased sympathetic stimuli, catecholeamines, calcium Negative- Decrease in contractility Ex acidosis, calcium channel blockers, extracellular vitamin K

Positive chronotropic factors

Increased heart rate | example tachycardia

Negative chronotropic factors

Decrease heart rate | example bradycardia

ANS vagal tone

Slowing heart rate PNS dominates the autonomic stimulation

Bainbridge reflex

Sympathetic reflexes initiated by increase blood in atria (increase venous return) Stimulation of SA node stimulate Baroreceptors in atria causing increased SNS stimulation

Hypocalcemia

Depresses heart rate

Hypercalcemia

Prolongs plateau phase and leads to spasms that do not allow heart to rest

Hypokalemia

Makes heart beat feebly and arrhythmically

Hyperkalemia

Interferes with depolarization by lowering action potential and may lead to heart block and cardiac arrest

Fetal heart structure | Foramen ovale

Connects the two atria At birth becomes the fossa ovalus

Fetal heart structure | Ductus arteriosus

Connect pulmonary trunk and the aorta After birth becomes ligamentum arteriosum

Why does the fetus heart structures have the foramen ovale and the ductus arteriosus?

To bypass the lungs before they are born

If you have a junctional rhythm what is absent on an ECG?

The P wave

If you have a partial heart block what is seen on an ECG?

More P waves than QRS waves

Fibrillation looks like what on an ECG?

Chaotic waves

P wave corresponds to ____ of a SA node; T wave corresponds to ___ ___

Depolarization, ventricular repolarization

Aortic valves sounds are heard where?

Second intercoastal space at right sternal margin

Pulmonary valve sounds are heard where?

Second intercostal space at left sternal margin

Where are bicuspid valve sounds heard

Over heart apex in fifth intercostal space in line with the middle of the clavicle

Where are tricuspid valves sounds heard?

Right sternal margin of the fifth intercostal space variation include over sternum or over left sternal margin in 5th intercostal space