Exam 1 Flashcards By MATI (Heart)

1. Functional blood supply of the heart itself

2. shortest circulation in body

1. Thoracic pain caused by deficiency in blood delivery to myocardium

2. Cells are weakened by temporary lack of oxygen

1. Prolonged coronary blockage causing areas of myocardial cell death

   1. Replaced with noncontractile scar tissue

   2. Damage to left ventricle most serious

1. muscle cells which are short, fat, branched, and interconnected; with one (sometimes two) centrally located nuclei

   1. Endomysium (loose connective tissue with many capillaries) fills intercellular space

      1. Connects cardiac muscle to fibrous skeleton (something cells can pull against)

1. interlocking junctions between myocytes that contain

   1. Desmosomes that hold cells together; prevent separation during contraction

   2. Gap junctions that allow ions to pass cell-to-cell; electrically coupled adjacent cells

1. large mitochondria (35% of cell volume) provide resistance to fatigue

2. Most of remaining volume consists of myofibrils, composed of sarcomeres

   1. Z discs, A bands, and I band present

   2. SR simpler than in skeletal muscle; no triads

   3. T tubules wider, less numerous; entering cell 1 per sarcomere at Z discs

1. a network of specialized cardiac muscle cells that generate and pass along electrical signals to make the heart beat in a steady, coordinated way

2. Initiates and distributes impulses to coordinate depolarization and contraction of heart

cardiac pacemaker cells

1. they have unstable resting potentials called pacemaker potentials

   1. Continuously depolarizing, drifting slowly toward threshold

   2. Produce action potentials that spread throughout heart

found in the sinoatrial (SA) node, atrioventricular (AV) node, and the His-Purkinje system, forming the heart’s electrical conduction hierarchy.

irregular rhythms which may be due to defects in intrinsic conduction system

1. rapid, irregular twitching contractions; useless for pumping blood

   1. Causes circulation to cease; may result in brain death

   2. Treatment: defibrillator shocks (depolarizes) all myocytes at once (repolarization follows), giving heart “clean slate” to restart sinus rhythm

the normal, healthy electrical pattern/rhythm of the heartbeat, starting from the heart’s natural pacemaker (SA node)

1. (abnormal pacemaker) may appear if SA node defective

   1. If AV node takes over, it sets junctional rhythm at 40–60 beats/min

a type of arrhythmia (irregular heartbeat) in which the heart’s electrical impulses originate from the atrioventricular (AV) node

1. premature, extra heartbeats/contractions—either atrial or ventricular—that interrupt the normal rhythm and often feel like skipped or stronger beats

   1. Heart has longer time to fill, so next contraction is felt as thud as larger volume of blood is being pushed out

1. If AV node is defective, it may happen

   1. Few impulses (partial block) or no impulses (total block) reach Ventricles- beat at their own intrinsic rate

   2. Too slow to maintain adequate circulation

   3. Treatment: artificial pacemaker

1. region in the medulla oblongata that increases heart rate and contractility via sympathetic stimulation

   1. sends signals through sympathetic trunk to increase both heart rate (HR) and force of contraction

      1. Targets SA and AV nodes, heart muscle, and coronary arteries

1. a group of neurons in the medulla oblongata that slows heart rate by increasing parasympathetic output through the vagus nerve

2. ends parasympathetic signals via vagus nerve to decrease HR

   1. Targets SA and AV nodes

1. machine that measures heart electrical activity

2. detects electrical currents generated by heart

1. a graphic recording of heart’s electrical activity

2. Composite of all action potentials at given time; not a tracing of a single AP

3. Electrodes are placed at various points on body to measure voltage differences

   1. 12 lead ECG is most typical

period of myocardial contraction

period of myocardial relaxation

1. all events associated with blood flow through the heart during one complete heartbeat

   1. Ventricular systole and diastole

   2. Atrial systole and diastole

volume of blood in each ventricle at end of ventricular diastole

volume of blood remaining in each ventricle after systole ends

a small downward deflection in the arterial pressure waveform that marks the closure of the aortic valve and the transition from systole to diastole.

a period of total heart relaxation, lasts about 0.4 s

abnormal heart sounds heard when blood hits obstructions

1. valve problems

   1. Incompetent (or insufficient) valve:

      1. fails to close completely, allowing blood backflow

   2. Stenotic valve

      1. fails to open completely, restricts blood flow through valve

         1. high-pitched sound or clicking as blood forced through narrow opening

1. the amount of blood pumped out by each ventricle in 1 minute

   1. Product of heart rate (HR) and stroke volume (SV)

1. the volume of blood pumped out by each ventricle per beat

   1. Correlates with force of contraction

difference between resting and maximal CO

% of blood ejected from the ventricles each beat (SV / EDV)

the heart increases stroke volume as end‑diastolic volume (preload) increases, because stretching cardiac muscle fibers enhances contraction strength, up to an optimal limit

amount of blood returning to heart (slow heartbeat and exercise increase venous return)

1. the pressure that ventricles must overcome to eject blood (the back pressure from arterial blood pushing on SL valves)

   1. about 80 mm Hg in aorta

   2. about 10 mm Hg in pulmonary trunk

the baseline activity of the vagus nerve—the main parasympathetic nerve—which influences heart rate, digestion, inflammation, and the body’s ability to return to calm after stress

an SNS reflex that increases heart rate in response to increased stretching of the right atrium and/or inferior vena cava due to greater venous return (increased preload)

depresses heart

increases HR and contractility, up to a point

alters resting membrane potential, which can lead to heart block and cardiac arrest

results in feeble heartbeat; arrhythmias

1. abnormally fast heart rate (>100 beats/min)

   1. May result from elevated body temperature, stress, certain drugs, or heart disease

   2. If persistent, may lead to fibrillation

1. resting heart rate slower than 60 beats/min

2. heart hypertrophies and SV increases, lower resting HR , still provides same CO

3. May result from low body temperature, drugs, or PSNS activation

4. May result in grossly inadequate blood circulation in nonathletes

   1. warning of brain edema due to head trauma

1. CO is so low that blood circulation is inadequate to meet tissue needs

2. Progressive condition; reflects weakening myocardium caused by

   1. Coronary atherosclerosis

1. clogged arteries caused by fat buildup; impairs oxygen delivery to cardiac cells

   1. Heart becomes hypoxic, contracts inefficiently

1. aortic pressure greater than 90 mmHg causes myocardium to exert more force to eject blood against greater afterload

heart becomes weak as dead contractile cells are replaced with scar tissue

ventricles stretch and become flabby, and myocardium deteriorates, often for unknown reasons

1. left side failure due to CHF

2. Blood backs up in pulmonary circuit (pressure rises) and fluid leaks from the blood vessels into the lung tissue causing pulmonary edema

1. right side failure due to CHF

2. blood backs up in systemic circuit, impairing ability of body cells to obtain adequate nutrients and oxygen and remove wastes causing edema mostly noticeable in extremities

gives rise to right atrium, coronary sinus, and SA node

becomes pectinate muscles of atria

becomes left ventricle?

gives rise to proximal aorta, pulmonary trunk, and right ventricle

connects atria (remnant is fossa ovalis in adult)

connects pulmonary trunk to aorta (remnant ligamentum arteriosum in adult)

heart murmurs

Decline in cardiac reserve and max HR, heart becomes less efficient

Heart stiffens; conduction system fibrosis causes arrhythmias

1. MI or heart stroke

2. NOTE: Many investigators think diet (not aging) is the single most important contributor to cardiovascular disease