092414 cardiac cell

Question 1

similarities btwn cardiac and skeletal musc

Answer 1

basal lamina
striated
similar contractile proteins
mechanism of contraction is similar

Question 2

differences btwn cardiac muscle and skeletal musc

Answer 2

cardiac muscle:

involuntary
myocytes are smaller
1-2 CENTRAL nuclei
myocytes branch

AEROBIC-so more VASCULAR, more MITOCHONDRIA, more MYOGLOBIN, more LIPID DROPLETS (lipid droplets are a major energy source)

has MB-creatinine kinase (specific for cardiomyocytes) and cTnl

has intercalated discs

Question 3

transverse intercalated discs’ fxn

Answer 3

transmit force

has fascia adherens (N-cadherins) and desmosomes

Question 4

lateral interacalated discs fxn

Answer 4

cell-cell signaling via gap jxns (nexus) and some desmosomes

Question 5

fascia adherens

Answer 5

are like zonula adherens (adherens jxns) except they don’t encircle the cell. only are on part of it

Question 6

L type Calcium channels

Answer 6

are for the calcium to enter the cell initially in the excitation phase of ecitation contraction coupling in cardiac musc

Question 7

ryanodine receptors

Answer 7

located in SR

are calcium channels that allow for calcium-induced calcium release

Question 8

in cardiac muscle, what does calcium ultimately bind to?

Answer 8

troponin-C

this binding causes tropomyosin to move

Question 9

how is myosin head activated?

Answer 9

by ATP hydrolysis. so it binds actin

Question 10

during contraction, what lengths of the sarcomere stay the same and what shortens

Answer 10

A band stays same

I band shortens

Question 11

how does relaxation of cardiac musc occur

Answer 11

L type channels inactivate

Calcium is re-sequestered into SR via SERCA (sarco endoplasmic reticulum calcium ATPase)

Question 12

how do catecholamines stimulate and relax cardiac muscle?

Answer 12

contraction:
increase cAMP levels. activate protein kinases. phosphorylation. activation of L type calcium channel. increased calcium influx. enhanced contractile force.

relaxation:
increase cAMP levels. activate protein kinases. phosphorylation. phospholambin in SR activated. increases calcium uptake by SR. increased relaxation.

Question 13

how do atria, SA, AV nodes differ from ventricular myocardium w regards to histology

Answer 13

atria, SA, AV nodes have smaller myocytes with fewer striation

atria-there’s membrane-bound granules containing atrial natriuretic factor (ANF/ANP), which is vasodilatory

Question 14

what does the bundle of His contain

Answer 14

Purkinje myocytes

Question 15

how are PUrkinje myocytes special?

Answer 15

they are specialized for conduction

they are differentiated from cardiac myocytes (this differentiation is caused by endothelin)

Question 16

what is the heart’s most abundnat cell type

Answer 16

cardiac fibroblasts

Question 17

chronology of heart attack

Answer 17

immediate-myocyte death, releasing MB-CK and cTnl

15 hours-inflammation

add 2-3 days: wound healing through cardiac fibroblasts–collagen deposition (fibrosis)

add 2-4 days: angiogenesis

lastly, scar deposition: due to collagen cross linking

Question 18

can cardiomyocytes naturally regenerate?

Answer 18

yes, but at a rate that is too slow in the case of a heart attack

Question 19

can skeletal myoblasts (skeletal muscle stem cells) regenerate cardiomyocytes?

Answer 19

approach has been abandoned because of inefficacy and arrhythmia

Question 20

are cardiac fibroblasts endogenous cardiomyocyte stem cells?

Answer 20

no, but recent work has suggested that cardiac fibroblasts can be induced into cardiomyocytes

Question 21

to remuscularize the heart, the best approach currently looks to be

Answer 21

via inducing pluripotent stem cells to become cardiomyocytes (b/c other approaches may show some benefits for better heart function, but they do not actually re muscularize/replace with cardiomyocytes)