cardiac muscle VM and cell biology

Question 1

Cardiac myocyte

Answer 1

Cardiomyocytes normally branch, usually one or 2 nuclei with each cardiomyocytes, cardiomyocyte nuclei are located centrally within the fibers

Intercalated discs between cardiomyocytes in longitudinal section, mainly composed of fascia adherens (in transverse part), and gap junctions (in the lateral part), cell adhesion and electrical coupling

Cross section is variable bc of branching (accumulation of collagen os a scar)

Question 2

blood vessels

Answer 2

Contain epithelium (endothelium), CT found in all three tunicas (intima, media, adventitia) and muscle spicifically smooth muscle

the tunica intima borders the lumen and consists of endothelium (simple squamous epithelium) and subendothelial CT
internal elastic lamina
Tunica media-vascular smooth muscle arranged in concentric layers with fenasterated elastic laminae, with sheets of elastic fiber
external lamina (in larger arteries)
Tunica Adventitia- outermost layer,  (

Question 3

Cardio myocytes vs skeletal muscle

Answer 3

Similarities: basal lamina, striated

Differences: involuntary, smaller, 1-2 central nuclei, branch, vascular, many mitochondria, myoglobine, lipid droplets, MB CK(if theres MBCK in blood think cardiac damage) intercalated discs, CICR

Question 4

Intercalated discs

Answer 4

IDs are sarcolemmal specialized that mediated CM-CM binding and enable CM to be in syncytium
Transverse: Transmits CM forces (fascia adherens, N cadherins N cadherins/desmosomes

Lateral part: mediates CM cm signaling (Gap junctions and a few desmosomes

last I band modified Z line, gap junctions (fascia adherens and zonula adherens) N cadherin in intercellular space

Question 5

Excitation-contraction coupling: cardiac

Answer 5

excitation (electrical): AP depolarization–T tubules Phase 2 of AP: L-type Cav 1.2–CA influz– Ca in C r
CICR : Ryr in Sr –> CA

Contraction physical– Ca binds troponin C– tropomyosin moves, TP hydrolysis activates the myosin head, the myosin head binds to actin, power stroke myosin into A band (sarcomere shortens–contraction)

During contraction (a-band stays the same, i band length shortens, relaxation- L type Ca channel inactivates, Phospholamban (PL) is phosphorylated SERCA pumps CA back into the SR

Question 6

Beta adrenergics

Answer 6

modulates contraction vs relaxation, cAMP increased, protein kinases activated, phosphorylation L type Ca channel T tubule (increase Ca into mocyte–enahced contractile), phosphorylation of phospholamban–Ca into SR, relaxation

Question 7

innervation of the myocardium

Answer 7

modulates the hearts intrinsic rhythm. Sympathetics (cervical ganglia–> heart and great vessels)–> increase HR (positive chronotropism)

Parasympathetics (vagus)– heart great vessels–> decrease HR (negative chronotropism)

Vagal neurotransmitter (Ach) activates muscarinic AchR in SA nodes. 
Negative Inotropism (reduced contractile force--IE the muscarinic AChR is a Beta adrenergic antagonist)

Question 8

Regional histologic differences in the heart

Answer 8

ventricular myocardium
Atria, SA, AV nodes (smaller CMs with fewer striations) atrial myocytes have granules (G) containing atrial natriuretic factor (ANF aka ANP)

bundle of His: Purkinje CMs (specialized for conduction, in the embryonic heart (endothelin–cardiac myocyte–purkinje fiber)

Cardiac fibroblasts -hearts most abundant by number not volume

Question 9

Chronology of Heart attakc

Answer 9

immediate: myocyte death--MBCK and cTNL
then inflammation
then would healing via cardiac fibroblasts
Angiogenesis (VEGF, FGF)
Scar