The Heart Ch 19 Flashcards
What and where are the three layers of the heart wall?
Epicardium – visceral layer
Myocardium – cardiac muscle
Endocardium – inner myocardial surface (touches heart chamber)
What is coronary circulation and collateral routes?
Functional blood supply to the heart muscle
Alternate route of blood delivery to heart muscle.
Anastomoses-arteries grown together
What is thoracic pain caused by deficient blood delivery to myocardium?
Angina pectoris
What is myocardial infarction?
Heart attack. Lack of oxygen due to blockage of coronary system.
What anchors cardiac cells together and allow free passage of ions? What two things are they made of?
Intercalated discs
Desmosomes and gap junctions
What is functional syncytium?
cardiac muscle functions as one group. Single coordinated unit.
What are autorhythmic cells?
The cell that creates the action potential that travels through gap junctions to depolarize the contractile cells
Explain the action potential steps of the “pacemaker potential” autorhythmic cells.
(pacemaker potential): Slow Na+ channels open-Na+ enters cell
(depolarization): fast Ca+ channels open-Ca+ enters cell
(Repolarization): k+ channels open, k+ exits the cell
Explain step two of cardiac muscle contraction with the contractile cell.
Calcium from adjacent cells initiates:
(Depol)Fast Na+ channels open, Na+ enter cell.
(Plateau): Slow Ca+ channels open, Ca+ enters cell. (long period)
Ca+ also exits from sarcoplasmic reticulum to start muscle contraction.
(Repolarization ): k+ channels open, k+ exits the cell.
List the five steps of the conduction pathway of heart cells
1-SA node (spreads through atria)
2-AV node (sends to ventricles)
3-AV bundle of His (splits into two)
4-2 bundle branches (inside the interventricular septum)
5-Purkinje fibers (carries to heart apex and ventricular walls)
What is pericarditis?
Inflammation of pericardium
Visceral and parietal periCardia stick together.
Inflammatory fluid compresses heart limiting pumping action: cardiac tamponade.
What is an arrhythmia?
Irregular heart rhythm
What is fibrillation?
Rapid random contractions, SA node not in control. Defibrillation needed to shock heart to reestablish rhythm through SA node.
A defective SA node can lead to what three issues?
1-ectopic focus: SA node is replaced by another pacemaker, like AV node.
2-junctional rhythm: pace set by AV node l(esser than SA node, Bpm 50)
3-extrasystole: (arrhythmia) Hyperexcitable region of heart causes premature contractions before SA initiates regular contraction. PVCs most problematic. No blood to ventricle from pumping too soon.
What is a heart block? And the two types?
Inability of ventricles to receive impulse from AV node
Total heart block: ventricles forced to beat at own slow autorhythmic rate. Too slow for adequate circulation.
Partial heart block: some signals from SA node transmitted to AV node, but not all. Extra P waves without QRS or T wave afterward.
Pacemakers needed for both.
The heart is stimulated and inhibited by what centers? What result, what nerve, and what Chemical?
Stimulated by sympathetic cardioacceleratory center. Sympathetic cardiac nerve. Increases HR. Norepinephrine.
Inhibited by parasympathetic cardioinhibitory center. Vegas nerve. Decrease HR. Acetylcholine.
According to the electrical activity shown on an ECG, what represents each piece of a cardiac rhythm?
P wave: depolarization of SA node
QRS complex: ventricular depolarization (atrial masked here)
T-wave: ventricular Repolarization
The first sound of heart beat occurs as _____ valves close and signifies the beginning of ________.
Second sound occurs when ______ valves close at the beginning of ________ ________.
AV, systole
SL, ventricular diastole
What is a heart murmur? And two possible reasons?
Abnormal heart sounds.
1-incompetent valve: incomplete close valve/s
2-stenotic valve: incomplete opening of valve/s
What is a cardiac cycle and how long does each part take?
All events associated with blood flow through the heart.
Average heartbeat 75/min
Cardiac cycle takes .8 seconds
.1 for atrial systole
.3 for ventricle systole
.4 quiescent period
When is ventricular filling taking place? What are the valves and atrium doing? And what is EDV?
Mid to late diastole. AV valve open. 80% of blood flow to ventricle. Atrial systole occurs delivering remaining 20%.
EDV: volume of blood in each ventricle at the end of ventricle diastole.
What is happening in the ventricular systolic phase (2)?
And what is ESV?
1-Atria relax and ventricles contract.
2-Rising ventricular pressure results in closing of AV valves.
3-Isovolumetric contraction in phase: all valves closed.
4-ejection phase, ventricular pressure exceeds pressure in artery, SL valves forced open.
ESV: volume of blood remaining in each ventricle
Phase 3 of the cardiac cycle.
When is isovolumetric relaxation and what is occurring?
Early diastole.
1-Ventricles relax.
2-Backflow of blood in aorta and pulmonary trunk closes SL valves:
Dicrotic notch caused by backflow of blood rebounding off closed SL valve.
What is cardiac output? And the formula to define it?
Amount of blood pumped by each ventricle in one minute.
CO = HR • SV
What is HR, SV, and cardiac reserve?
HR – number of heartbeats per minute
SV – amount of blood pumped out by ventricle beat. EDV-ESV=SV
CR – difference between resting and maximal CO (co-blood pumped in 1min).
What are the three factors that affect stroke volume?
Preload contractility and afterload
What is Frank starling law of the heart.?
Preload is the critical factor in controlling SV.
- give more blood, pumps more blood.
What are the five factors of preload?
1-cardiac muscle exhibits a length tension relationship.
2-at rest, cardiac muscle cells are shorter than optimal length.
3-slow heartbeat and exercise increased venous return and SV.
4-increased venous return stretches ventricles and increases contraction force.
5-blood loss and extremely rapid heartbeat decrease SV.
The factor affecting SV: contractility, does what?
(measurement of how strong the heart is )
Increase in contractile strength (independent of stretch and EDV)
Because:
Increased sympathetic stimuli
Certain hormones
Calcium and drugs similar to epi-and and digitalis
Called: positive inotropic agents
What factors decrease contractility, making the heart weaker? And what are those called?
Acidosis.
Increased extracellular potassium. Calcium channel blocker’s.
Negative inotropic agents.(lowers SV and CO)
Positive and negative chronotropic factors to do what?
What do you call clinically abnormally high or low heart rate?
Positive – increased heart rate
Negative – decrease heart rate
Tachycardia – abnormally high heart rate
Bradycardia – abnormally low HR
Sympathetic nervous system stimulation is activated by _____, and releases ______.
Stress, anxiety, excitement or exercise
Epinephrine and norepinephrine
Parasympathetic nervous system stimulation is mediated by ________, and opposes _________.
ACH
SNS
What is the atrial reflex?
Sympathetic reflex initiated by increased blood in the atria
- causes stimulation of SA node triggering atrial contraction and faster HR
- simulate baroreceptors in atria causing increased SNS stimulation
- give heart more blood, beats faster
What is hypocalcemia?
What is hypercalcemia?
Hypo: depresses heart rate
hyper: prolongs plateau phase in leads to spasms that do not allow hard to rest
What is hypo kalemia?
What is hyperkalemia?
Hypo: makes heartbeat feebly and arrhythmically
Hyper: interferes with depolarization by lowering action potential. May lead to heart block and cardiac arrest.
What is congestive heart failure caused by?
- blood flow problem
Coronary atherosclerosis
Persistent hi blood pressure
Multiple myocardial infarction
Dilated cardiomyopathy(ventricle walls stretched becoming flabby)
What do the left and right heart failure’s congest?
Left heart failure: pulmonary congestion
Right heart failure: Peripheral congestion
What are the fetal heart structures and their function?
Foramen ovale: connects two atria
Ductus arteriosus: connect pulmonary trunk in aorta
