Histology of Heart

Question 1

Can you have tetanic contraction of myocytes?

Answer 1

no –> need to relax in order to have diastole

Question 2

2 layers of epicardium

Answer 2

1. visceral layer

2. parietal layer

Question 3

Heart chambers are lined by the ____ which is composed of endothelium and underlying connective tissue.

Answer 3

endocardium

Question 4

T/F endothelium is contiguous with blood vessels and surfaces of heart valves.

Answer 4

T

Question 5

T/F the endocardium has anti-thrombotic properties that may be reduced by injury or inflammation.

Answer 5

T

Question 6

Is endocardium thicker in atria or ventricles?

Answer 6

atria b/c of a much thicker stroma/subendocardium

Question 7

What constitutes the fibrous skeleton of the heart

Answer 7

annuli fibrosi and the membranous ventricular septum –> composed of dense connective tissue forming an aponeurosis with thick collagen fibers in different directions

Question 8

What is the role of the fibrous skeleton of the heart?

Answer 8

electrically separate atria from ventricles

Question 9

What are the annuli fibrosi?

Answer 9

the triangular regions between the aortic annulus and the AV valves

Question 10

How close are inflow/outflow in LV?

Answer 10

close/shared border

Question 11

How close are inflow/outflow in RV?

Answer 11

separate

Question 12

What cells initiate spontaneous activity in the heart?

Answer 12

SA node

Question 13

What cells allow for ventricular electrical delay?

Answer 13

AV node

Question 14

The _____ conducts electrical signals to the apex of the heart.

Answer 14

Bundle of His

Question 15

How are purkinje cells connected to one another?

Answer 15

lateral gap junctions, interacalated disks –> few myofibrils

Question 16

What structures provide mechanical and electrical junctions between cells arranged end to end?

Answer 16

intercalated disks

Question 17

What structures provide electrical connections between adjacent cardiac myocytes?

Answer 17

gap junctions

Question 18

Myocardium: central or peripheral nuclei?

Answer 18

central

Question 19

Why are there different layers of ventricular myocardium?

Answer 19

need to have muscles contracting in different directions to achieve “wringing” motion of LV contraction

Question 20

The deepest fibers in the LV are longitudinal/circumferential.

Answer 20

longitudinal

Question 21

Within a bundle, cardiac myocytes connect in series via ____

Answer 21

intercalated disks

Question 22

Cardiac muscle: branched/not branched

Answer 22

branched vs striated/smooth

Question 23

How many nuclei in cardiac muscle?

Answer 23

one/two vs. skeletal (multi) and smooth (one)

Question 24

How are gap junctions blocked?

Answer 24

prolonged increase in intracellular calcium –> limits spread of damage from one cell to next

Question 25

Constituents of thin filaments

Answer 25

actin (2 strands), tropomyosin, troponin

Question 26

Role of tropomyosin

Answer 26

stabilize actin

Question 27

Role of troponin

Answer 27

bind actin, bind tropomyosin, bind Ca2+

Question 28

Constituents of thick filaments

Answer 28

myosin tail + 2 globular domains

Question 29

Role of titin

Answer 29

provides restoring force in sarcomeres –> attached to z line and myosin thick filaments

Question 30

As sarcomere is passively stretched, ____ extends first

Answer 30

titin

Question 31

At long sarcomere lengths, the eleastic ____ region changes conformation producing an increase in passive tension

Answer 31

PEVK (proline-glutamate-valine-lysine)

Question 32

Why is it hard to overstretch cardiac muscle?

Answer 32

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

Question 33

T/F each myocyte contacts one capillary

Answer 33

f–> several capillaries/myocyte and vice versa

Question 34

How is ATP generation kept close to working sarcomeres in myocytes?

Answer 34

continuous strips of longitudinally arranged mitochondria

Question 35

What structure promotes surface area for distribution of electrical potential to inside of cell/between sarcomeres?

Answer 35

t tubules

Question 36

What is the voltage gated trigger for intracellular Ca release in myocytes?

Answer 36

ryanodine receptor

Question 37

What secretes natiuretic peptides in atria?

Answer 37

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