Cardiology Flashcards
hallmark of reversible cellular injury
swelling
ex: angina causes swelling of myocytes with 70% stenosis
subendocardial ischemia will produce ST depression
Swelling is due to failure to maintain ATP generation in hypoxic tissues therefore impaired Na/K ATPase function
incomplete occlusion of coronary artery
chest pain at rest
unstable angina
vasospasm of the coronary artery causing chest pain
prinzmetal variant angina
when does necrosis of the myocardium occur
> 20 min of occlusion of blood flow
When does ST elevation occur?
when there is damage to the entire wall of the myocardium => transmural infarct
Will see ST depression when it is subendocardial
What marker is helpful in determining another infarction occurring a few days following initial infarction?
CK-MB
troponin-I stays elevated for 7 days but CK-MB elevates within 4-6 hours and returns to normal level within 72 hrs.
CO2 produced/O2 consumed
Respiratory quotient (RQ) = 0.8
Which gas has a higher diffusion gradient in the alveolus: O2 or CO2?
O2
mixed venous O2 = 40 mm Hg; Alveolar PO2 = 100 mmHg
mixed venous CO2 = 46 mmHg; alveolar CO2 = 40 mmHg
BUT both gases diffuse at the same rate, because CO2 is 20x soluble in water than O2
How can volume depletion being assessed on physical exam?
Assess blood pressure while lying and standing. Normally blood pressure is compensated upon standing, but in volume depletion the blood pressure will drop due to decreased preload.
important buffering systems in the blood
bicarbonate and proteins (hemoglobin)
Apoptosis vs necrosis
Apoptosis is programmed cell death that “fine-tunes” cell populations. Necrosis is pathological and often the result of massive tissue destruction. Necrosis ultimately results in the spilling of cellular contents which invokes INFLAMMATION
3 layers of blood vessels (except capillaries)
tunica intima, tunica media, tunica adventitia
Note: the small vessels (vasa vasorum) that supply the large blood vessels with nutrients run through the adventitia
How much of the total blood volume do arteries contain?
12%
The small and large veins contain ~60% total blood volume (small veins having 45%)
Why does pulse pressure increase with age?
the amount of collagen in large arteries increases with age, decreasing the elasticity
major site for regulation of distribution of blood flow and arterial pressure regulation
arterioles
Why are capillaries not prone to rupture, but vena cavae can?
Capillaries have a small radius, and the vena cavae have a larger radius. The radius is what determines the wall tension.
LaPlace:
Tension ~ change in P x radius
What varies the strength of cardiac muscle cell contraction?
intracellular calcium concentration during cell activation
Depends upon the number of crossbridges
Note: skeletal muscle strength of contraction is controlled by changing the frequency of action potentials
What defines the ends of the sarcomere?
Z line
the Z line is composed of alpha-actin
parallel bundles of sarcomeres
myofibril
contain gap junctions (connexons) for electrical continuity and desmosomes (cadherin) for physical strength
intercalcated discs
thin filaments are composed of
F-actin
When is the heart muscle perfused?
During relaxation (diastole); the force of contraction impedes blood flow
How does calcium ion trigger differ between skeletal muscle and cardiac muscle?
Cardiac muscle intracellular calcium comes from the SR (75%) and ECF (25%). Skeletal muscle only uses SR stores of calcium.
How does intracellular calcium get expelled from the cell?
3 Na+-Ca2+ exchanger
