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47 Cards in this Set

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  • Back
3 Cell types in Cardiac muscle:
1. Cardiac myocytes
2. Endothelium (endocardium)
3. Cardiac fibroblasts
3 Similarities of cardiac muscle to skeletal:
-Both have basal laminas surrounding individual cells
-Both are striated
-Both have similar mechanisms of contraction
4 Major differences between Cardiac and skeletal muscle:
-Cardiac is involuntary
-Cardiac has only 1-2 nuclei
-Nuclei are CENTRAL
-Cells BRANCH
How do cardiac myocytes compare to skeletal in terms of size?
They are smaller
How does the blood supply to cardiac muscle compare to skeletal?
It is much more highly vascularized.
What 3 things do cardiac muscles require to be supplied for their continual energy demand?
-Mitochondria
-Myoglobin
-lipid droplets
What type of creatine kinase is in:
-Skeletal muscle
-Cardiac muscle
Skeletal = MM

Cardiac = MB
What connects cardiac muscle cells together as a syncytium?
Intercalated disks
What 2 proteins from cardiac muscle indicate MI?
-CK-MB
-Troponin I
What do cardiac myocytes have in place of the Triad?
Dyads
Where are Dyads located?
At the Z-line, not the AI junction like in skeletal muscle.
ARE cardiac myocytes a syncytium?
No; they just can act like they are by the intercalated disks.
2 components in a skeletal muscle intercalated disc:
-transverse part
-lateral part
What is the transverse part made of?
A half a z line
2 structures that compose the "half z-line" of transverse parts of intercalated disks:
-a Fascia adherens which does NOT encircle the cell
-Desmosome
What butts against the half-Z bands?
Actin filaments and N-cadherins
What 2 structures are found in the Lateral part of intercalated disks?
-Gap junctions ( to allow cell-cell signalling/rythmicity)
-Desmosomes
Gap junctions are made up of:
connexins
How are Atrial myocytes in comparison to ventricular?
-Smaller
-Fewer t-tubules
What special hormone is released from atrial myocytes?
ANF (atrial natiuretic peptide)
What are Atrial NODE myocytes like?
Small and embedded in dense CT
What are AV Bundle of his cells like? What are they called?
Purkinje fibers - LARGE and have few myofibrils.
What causes cardiac myocytes to become Purkinje cell fibers?
Secretion of ENDOTHELIN from endothelial cells in developing coronary arteries.
What is the Endocardium?
The lining of cardiac endothelial cells
What type of epithelium is the endocardium?
Simple squamous
What are the most abundant cells in the heart?
Cardiac fibroblasts
What is the major fuel for cardiac myocytes?
Triglyceride (Fatty acids)
Where are triglycerides stored in cardiac myocytes?
In membrane bound lipid droplets near the nucleus.
Does the heart undergo anaerobic metabolism?
No; it's largely aerobic.
Serum levels of MM-CK are diagnostic for:
Skeletal muscle dystrophy
Serum levels of MB-CK are diagnostic for:
Myocardial infactions
What innervates cardiac myocytes?
The vagus nerve and sympathetics.
When does myocyte death begin during a heart attack?
When does inflammation occur?
When does Wound healing begin?
Death - immediately
Inflammation - 12-16 hrs later
Healing - 2-3 days later
What is synthesized during wound healing following an MI?
-Collagen III
then
-Collagen I
What secretes the collagen for wound healing?
Cardiac fibroblasts
What are the last 2 steps in wound healing?
-Angiogenesis
-Scar formation
What does Scar formation consist of?
Crosslinking collagen by lysyl oxidase
What are 2 types of injury to cardiac myocytes?
1. Hypertrophy
2. Ischemic
What characterizes pathological cardiac hypertrophy?
Re-expression of embryonic cardiac genes
Is the replacement of myocytes lost due to ischemia with with Fibroblasts a good idea?
No; it would only create a non-contractile scar.
Where might stem cells for cardiac myocyte regeneration be obtained?
-Embryonic - but requires transplantion
-Adult - from bone marrow or the heart itself.
So 2 possible sources of adult stem cells for cardiac myocyte regeneration:
-Bone marrow
-Heart itself
(but neither is proven)
What are embryonic stem cells in terms of differentiation capability?
Pluripotent
Where are embryonic stem cells derived?
From the inner cell mass of blastocyst stage embryos
How do embryonic stem cells turn into beating cardiomyocytes in developing embryos?
Precardiac endoderm induces Precardiac mesoderm to do it.
What happens when precardiac endoderm is cultivated with ESCs?
They are induced to become beating cardiac myocytes with VERY HIGH FREQUENCY.
Can leftover adult cardiac myocytes be induced to regenerate infarcted myocardium?
Maybe.