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Flashcards in cardiac muscle structures Deck (30):
1

contractile cells of the heart

myocytes

2

The largest cell population by number is

endothelial cells, followed by cardiac fibroblasts

3

predominant components of the ECM are:

Fibrillar collagen type I and III

4

disruptions in the ECM occur with

disease and cardiac remodeling

5

Cardiac muscles are:

1. striated
2. not under direct neural control (unlike skeletal which are)
3. shorter, narrower
4. richer in mitochondria
5. one nucleus
6. Ca2+ binds to troponin, which regulates actomyosin interaction

6

ATPase activity of myosin is

slower in cardiac than skeletal but faster than smooth muscle

7

in cardiac muscle, Ca2+ binds to

troponin, which regulates actomyosin interaction

8

Cardiac muscle cells are connected with each other through

intercalated discs

9

coupling between cardiac muscle cells is

both mechanical and electrical

10

intercalated discs

1. Coincide with the Z discs; contain desmosomes and gap junctions
2. Desmosomes provide adhesion and assure that the force generated in one cell passes to the other (connects to ECM)
3. Gap junctions provide low resistance pathways for electrical current

11

Myofibrils and mitochondria occupy about

85% of the heart cell volume (the rest contains sarcolemma, T-tubules, SR, intercalated disks, gap junctions, etc)

12

thick filament

composed of hundreds of long, contractile myosin molecules arranged in a staggered side by side complex

13

thin filament

composed of hundreds of long, contractile myosin molecules arranged in a staggered side by side complex

14

saracomere

unit of contractile activity composed mainly of actin and myosin and extending from Z line to Z line in a myofibril

15

myofibril

end to end arrays of identical sarcomeres

16

myofiber

a single, multinucleated muscle cell containsing all the usual cell organelles plus many myofibrils

17

muscle

organized array of muscle fibers

18

a cardiac muscle cell is made up of

sarcomeres

19

sarcomere is defined as

z line to z line

20

the a band is

thick filaments

21

the I band is

thin filament extensions from the Z line

22

major contractile protein

1. myosin
2. actin

23

Myosin

1. Composed of two heavy chains and four light chains (RLC, ELC) with a mass of about 480,000 daltons.
2. Developmental regulation of isoforms (and with disease).
3. HC isoform determines ATPase activity (a vs b)

24

Actin is

1. Similar to skeletal muscle myosin
2. Binds tropomyosin and troponin

25

major regulatory

1. troponin C
2. troponin I
3. troponin T
4. tropomyosin

26

Troponin C (TN-C)

A dumbbell shaped protein with the N-lobe containing only one Ca2+-binding site (unlike skeletal which contains two)

27

troponin I (TN-I)

1. Contains a unique N-terminal extension of 32 amino acids that contains 2 PKA phosphorylation sites critical for adrenergic responsiveness of the heart.
2. This extension interacts with TN-C but is released with phosphorylation.

(KNOW THIS)

28

TN-C ca2+ binding sites

only one calcium binding site, compared to 2 in skeletal

29

Troponin T (TN-T)

1. Binds tropomyosin.
2. Developmental regulation of isoform expression (and perhaps pathological regulation).

30

Tropomyosin

only the alpha isoform is in the heart