Cardiac Muscle Fibers

Question 1

Cardiac muscle is …… in origin

Answer 1

Mesodermal

Question 2

Mention arrangement of cardiac muscle fibers

Answer 2

Longitudinal, tranverse & oblique

Question 3

Myosin is present in ….., the connected end is attached to …..

Answer 3

A band
Transverse filament (M line)

Question 4

Actin is found in ….., its connected end is attached to …..

Answer 4

I & A bands

Z line

Question 5

SR is composed of ….&….

Define them

Answer 5

Sarcotubules: anastomosing tubules surrounding myofibrils

Terminal cisternae: ring around myofibil close to T-tubule

Question 6

Each sarcomere has …. T-tubule(s)

Answer 6

One

Question 7

Define diad & its site

Answer 7

Level of Z-line

1 T-tubule + 1 terminal cisternae of SR

Question 8

Intercalated disc is composed of ……&……

Describe their position

Answer 8

Tranverse portions: right angle to sarcolemma

Longitudinal portions: parallel to sarcolemma

Question 9

Components of transverse portion and function

Answer 9

Fascia adherens, desmosomes (prevent separation), gap junction (allow direct communication & transmission of impulses)

Question 10

Components of longitunidal portion

Answer 10

Large gap junctions

Question 11

Electron dense secretory granules are found in …… . Contain …… which …..

Answer 11

Right atrium, to lesser extent left atrium & ventricles
Atrial natriuretic factor
Controlling blood pressure

Question 12

Damage of mycardium heals by ….

Answer 12

Fibrosis

Question 13

Describe composition of epicardium

Answer 13

Mesothelial cells

Subserous layer of loose connective tissue, contains coronary blood vessles, fat cells & nerves

Question 14

Cardiac muscle fibers are found in ….

Answer 14

Myocardium

Question 15

Describe composition of endocardium

Answer 15

1. Endothelium (simple squamous epithelium & subendothelil CT)
2. Thick middle layer of CT rich in elastic fibers
3. Subendocardium: loose CT with blood vessels, nerves & Purkinje fibers.

Question 16

Compare angina & myocardial infarction

Answer 16

A: slowly progressive reduction of coronary artery lumen by atheroma impairs oxygenation of ventricular muscle leading to chest pain usually brought by exertion.
M.I.: complete obstruction of one of the coronary arteries results in oxygen deprivation of an area of heart. Muscle fibers die.

Question 17

Middle layer of CT of valves is rich in …..

Answer 17

Elastic & collagen fibers

Question 18

Moderator band consists of ……

Answer 18

Purkinje fibers

Question 19

GR: Purkinje fibers are pale in colour.

Answer 19

Due to high content of glycogen

Question 20

Mention inclusions of cardiac muscle fibers

Answer 20

Glycogen, lipid droplets, lipofuscin

Question 21

Comapre SR & T-tubule of cardiac muscle fibers & skeletal muscle

Answer 21

SR is less developed but T tubule are wider and numerous than those of skeletal muscle.