Histology of Heart Flashcards
Can you have tetanic contraction of myocytes?
no –> need to relax in order to have diastole
2 layers of epicardium
- visceral layer
2. parietal layer
Heart chambers are lined by the ____ which is composed of endothelium and underlying connective tissue.
endocardium
T/F endothelium is contiguous with blood vessels and surfaces of heart valves.
T
T/F the endocardium has anti-thrombotic properties that may be reduced by injury or inflammation.
T
Is endocardium thicker in atria or ventricles?
atria b/c of a much thicker stroma/subendocardium
What constitutes the fibrous skeleton of the heart
annuli fibrosi and the membranous ventricular septum –> composed of dense connective tissue forming an aponeurosis with thick collagen fibers in different directions
What is the role of the fibrous skeleton of the heart?
electrically separate atria from ventricles
What are the annuli fibrosi?
the triangular regions between the aortic annulus and the AV valves
How close are inflow/outflow in LV?
close/shared border
How close are inflow/outflow in RV?
separate
What cells initiate spontaneous activity in the heart?
SA node
What cells allow for ventricular electrical delay?
AV node
The _____ conducts electrical signals to the apex of the heart.
Bundle of His
How are purkinje cells connected to one another?
lateral gap junctions, interacalated disks –> few myofibrils
What structures provide mechanical and electrical junctions between cells arranged end to end?
intercalated disks
What structures provide electrical connections between adjacent cardiac myocytes?
gap junctions
Myocardium: central or peripheral nuclei?
central
Why are there different layers of ventricular myocardium?
need to have muscles contracting in different directions to achieve “wringing” motion of LV contraction
The deepest fibers in the LV are longitudinal/circumferential.
longitudinal
Within a bundle, cardiac myocytes connect in series via ____
intercalated disks
Cardiac muscle: branched/not branched
branched vs striated/smooth
How many nuclei in cardiac muscle?
one/two vs. skeletal (multi) and smooth (one)
How are gap junctions blocked?
prolonged increase in intracellular calcium –> limits spread of damage from one cell to next
Constituents of thin filaments
actin (2 strands), tropomyosin, troponin
Role of tropomyosin
stabilize actin
Role of troponin
bind actin, bind tropomyosin, bind Ca2+
Constituents of thick filaments
myosin tail + 2 globular domains
Role of titin
provides restoring force in sarcomeres –> attached to z line and myosin thick filaments
As sarcomere is passively stretched, ____ extends first
titin
At long sarcomere lengths, the eleastic ____ region changes conformation producing an increase in passive tension
PEVK (proline-glutamate-valine-lysine)
Why is it hard to overstretch cardiac muscle?
tension is already high at lmax (because cardiac titin is stiffer and shorter than skeletal titin) vs. skeletal muscle which can take tension even beyond lmax
T/F each myocyte contacts one capillary
f–> several capillaries/myocyte and vice versa
How is ATP generation kept close to working sarcomeres in myocytes?
continuous strips of longitudinally arranged mitochondria
What structure promotes surface area for distribution of electrical potential to inside of cell/between sarcomeres?
t tubules
What is the voltage gated trigger for intracellular Ca release in myocytes?
ryanodine receptor
What secretes natiuretic peptides in atria?
secretory granules in golgi region of atrial myocytes –> regulate body fluid homeostasis via natriuresis, vasodilation, renin/angiotensin suppression –> granules constitutively released in ventricles and secreted non-constitutively in atria
