C-Cardiac MuscleMyocyte Structure & Function

Question 1

Regulators of Cardiac Output

Answer 1

preload
afterload
contractility

CO= Heart Rate x Stroke Volume

Question 2

Afterload is

Answer 2

pressure ventricles are pushing against to eject blood from the heart

Question 3

Preload is

Answer 3

volume in the heart (ventricle) before it beats

Question 4

Heart is made up of approximately 2 -3 billion _________ but this accounts for only about 1/3 of the number of cells

Answer 4

cardiac muscle cells

responsible for corrdinated contraction

Question 5

Other cell types include fibroblasts, endothelial cells, smooth muscle cells, and immune cells in the

Answer 5

heart

Question 6

Contraction starts at

Answer 6

the apex ofthe heart

Question 7

Other cell types include ___________ in the heart

Answer 7

fibroblasts
endothelial cells
smooth muscle cells
immune cells

Question 8

Fibrillar collagen type I and III are the most predominant components of the ECM and disruptions in the ECM occur with disease and___________

Answer 8

cardiac remodeling

Question 9

Cardiac muscles are __________ (like skeletal muscle)

Answer 9

striated

Question 10

Cardiac muscles are ___________ direct neural control (unlike skeletal)

Answer 10

NOT under

Question 11

Cardiac muscle cells are shorter, narrower & richer in mitochondria than skeletal muscle cells have __________ nucleus

Answer 11

only one or two

Question 12

__________ activity of myosin is slower in cardiac than skeletal but faster than smooth muscle

Answer 12

ATPase

Question 13

Cardiac muscle cells are connected with each other through_________-

Answer 13

intercalated discs

Coincide with the Z discs; contain desmosomes and gap junctions

Question 14

Ca2+ binding to troponin regulates __________ interaction

Answer 14

actomyosin

Question 15

coupling between cardiac muscle cells is both___________

Answer 15

mechanical and electrical

Question 16

Desmosomes provide adhesion and assure that the ______ generated in one cell passes to the other (connects to ECM)

Answer 16

force

Question 17

Ca2+ binding to ________ regulates actomyosin interaction

Answer 17

troponin

Question 18

_________ provide low resistance pathways for electrical current

Answer 18

Gap junctions

Question 19

_______ binding to troponin regulates actomyosin interaction

Answer 19

Ca2+

Question 20

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

Answer 20

Thick Filament

Question 21

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

Answer 21

Thin Filament

Question 22

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

Answer 22

Sarcomere

Question 23

End-to-end arrays of identical sarcomeres

Answer 23

Myofibril

Question 24

A single multinucleate muscle cell containing all the usual cell organelles plus many myofibrils

Answer 24

Myofiber

Question 25

Composed of two heavy chains and four light chains, ATPase activity (a vs b) motor proteins that move along actin filaments, while hydrolyzing ATP.

Answer 25

Myosin

Question 26

Similar to skeletal muscle myosin | Binds tropomyosin and troponin

Answer 26

Actin

Question 27

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

Answer 27

Troponin C (TN-C)

Question 28

Contains a unique N-terminal extension of 32 amino acids that contains 2 PKA phosphorylation sites critical for adrenergic responsiveness of the heart.

Answer 28

Troponin I (TN-I)***** -extension interacts with TN-C but is released with phosphorylation.

Question 29

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

Answer 29

Troponin T (TN-T)

Question 30

Only alpha isoform in the heart (but may be pathologically regulated)

Answer 30

Tropomyosin

Question 31

Troponin i

Answer 31

lies over myosin binding site inhibitor phosphorylation sites critical for adrenergic responsiveness of the heart. interacts with TN-C but is released with phosphorylation.

Question 32

AP leads to Ca release. Ca binds to troponin C. Troponin complex undergoes structural change, moving tropomyosin out of the way. Myosin binds actin and crossbridge moves. Ca is released, tropomyosin reblocks binding site - relaxation ****

Answer 32

Contraction – Relaxation Cycle

Question 33

Contraction – Relaxation Cycle****

Answer 33

AP leads to Ca release. Ca binds to troponin C. Troponin complex undergoes structural change, moving tropomyosin out of the way. Myosin binds actin and crossbridge moves. Ca is released, tropomyosin reblocks binding site - relaxation

Question 34

Cross bridge

Answer 34

myosin head attached/binding to actin | ultimately generates force

Question 35

“rest” state (state 1) during diastole

Answer 35

Cross bridges are initially in a weakly bound, non-force-generating “rest” state

Question 36

The triggering of force generation and contraction is governed by Ca2+ fluxes determined by the dynamics of electrochemical coupling of Ca2+ release and Ca2+ binding to ________

Answer 36

cTnC. Cross bridges and thin filaments now enter into a transition state (state 2)

Question 37

CO =

Answer 37

heart rate x stroke volume.

Question 38

actin (thin) filaments of muscle fibres slide past the myosin (thick) filaments during muscle contraction, while at constant length.

Answer 38

Sliding Filament Hypothesis

Question 39

Titin forms an ________, and there are many points of regulation within titin

Answer 39

elastic spring major protein in cardiac muscle cell

Question 40

also known as connectin, is a flexible intrasarcomeric filamentous protein, which is largest proteins known today.

Answer 40

titin

Question 41

Action potential leads ______ in the heart .

Answer 41

to ca release

Question 42

Calcium binds to ________ in the heart.

Answer 42

troponin C

Question 43

Troponin complex undergoes structural change, moving _______ out of the way.

Answer 43

tropomyosin

Question 44

Myosin binds _______ and crossbridge moves.

Answer 44

actin

Question 45

Calcium is released, __________ reblocks binding site - relaxation

Answer 45

tropomyosin

Question 46

The effect of increasing preload on force of contraction: the greater the volume of blood entering the heart during diastole (end-diastolic volume), the greater the volume of blood ejected during systolic contraction (stroke volume) and vice versa.

Answer 46

Frank-Starling Law of the Heart

Question 47

Frank-Starling Law of the Heart

Answer 47

The Greater the Preload, the greater the force generated” with a Length-tension relationship for the myocytes

Question 48

Mechanisms behind the length-tension relationship

Answer 48

Extent of overlap Change in the sensitivity of the myofilament to calcium: Increased calcium release

Question 49

At short lengths only a fraction of the potential cross-bridges are activated by a given increase in calcium. At longer lengths, more of the cross-bridges become activated by the same change in intracellular calcium. No time delay in the “sensor”.

Answer 49

Change in the sensitivity of the myofilament to calcium

Question 50

Occurs several minutes after changing the length of the muscle. May be due to stretch-sensitive ion channels in the cell membrane.

Answer 50

Increased calcium release

Question 51

Calcium Sensitivity of Cardiac Muscle Several factors regulate calcium sensitivity of the myofilament

Answer 51

Several factors regulate calcium sensitivity of the myofilament TnI phosphorylation Isoform composition sarcomere length

Question 52

The responsiveness of the myofilament to calcium is___________

Answer 52

“calcium sensitivity”

Question 53

_________ is the central factor in myocardial contraction

Answer 53

Calcium