2: Lecture 6 Flashcards
What causes period of inactivity
voltage gated ion channels of heart undergo a conformational change (instead of giving off action potentials)
What is P wave
Depolarization caused by atrial systole (contraction of atria)
What is QRS complex
Depolarization by ventricular systole (contraction of ventricles)
What does the delay window before QRS complex represent
Time for electrical signal in atria to move through bundle of his into ventricles
What is T wave
Repolarization of ventricles
What is PR interval
Delay at atrioventricular node (AV node)
What are semilunar valves
Open up into the aorta or pulmonary artery
AV valves
Open when blood moves from atrium to ventricle to fill up ventricle
What do the 1st and 2nd heart sound represent?
1st–>AV closing
2nd–>semilunar valves closing
What is the SA node
Small collection of cells that initiate atrial systole–>causes rhythmic activity in the heart
Functions of AV node
Provides delay in impulse transmission
Protects ventricles from atrial fibrillation
Function of Bundle of His
Divides right and left bundles
Provides orderly depolarization of ventricles (damage can lead to ventricular fibrillation)
Causes of Arrhythmias and Treatment
1) Abnormal pacemaker activity
2) Impaired cardiac conduction
Treatment
Insertion of pacemaker (electrical device/act as defibrillator)
Electrical ablation
Some cases drug treatment
3 Ways to slow normal pacemaker activity
1) Make resting membrane potential more hyperpolarized (more negative by using drugs that open K+ channels)
2) Reduce diastolic depolarization (by blocking SOME voltage gated sodium channels to slower rate of change of membrane potential)
3) Make a more positive threshold potential (administer drugs to change voltage sensitivity of different ion channels)
What is Delayed afterdepolarization?
Heart is working too fast and doesn’t have time to reset itself
Can lead to ectopic heart beat
What is pathophysiology?
Heart tissue death resulting in non-conductible scar tissue
Results in out of sync contractions (ventricular fibrillation which can kill you)
5 Classes of antiarrhythmic drugs
1) Na+ channel blockers (Quinidine)
2) Beta blockers (Propranolol)
3) K+ channel blockers (Sotalol
4) L-Type Ca2+ channel blockers (Verapamil)
5) Miscellaneous (adenosine, K+, and Mg2+ ions), not widely used
Main action of Class 1: Na+ channel blockers (antiarrhythmic drugs)
ex. Quinidine
Slow intraventricular conduction (increases QRS) and increase ventricular action potential (increase QT)
Selective for abnormal tissue
Slow intraventricular conduction only
Main action of Class 2: Beta-blockers (antiarrhythmic drugs)
ex. Propranolol
Slow AV conduction and prolong PR interval
Main action of Class 3: K+ channel blockers (antiarrhythmic drugs)
ex. Sotalol
Prolong ventricular action potential and prolong PR interval
Main action of Class 4: L-Type Ca2+ channel blockers (antiarrhythmic drugs)
ex. Verapamil
Slow AV conduction and prolong the PR interval (like beta blockers)
What is Type 1 diabetes
Insulin-dependent/Juvenile onset diabetes (10%)
Body fails to produce insulin in pancreas, requires insulin injections
Take Metformin (hypoglycemic drug)
What is Type 2 diabetes
Insulin resistant/Adult onset diabetes (80-90%)
Inability of cells to use insulin, can be combined with insulin deficiency
Tied to lifestyle and obesity
What is Diabetic macrovascular disease?
Accelerated atherosclerosis involving aorta, medium, and large arteries
Consequences: myocardial infarction and gangrene of lower extremities
