6. Heart and Vascular System I

Question 1

What is the main difference between skeletal muscle, cardiac muscle and smooth muscle?

Answer 1

Skeletal: striated and volunatry
Smooth: nonstriated and involuntary
CARDIAC: STRIATED AND INVOLUNTARY

Question 2

Smooth muscle occurs as sheets/bundles of elongated fusiform cells, with centrally located nuclei. There are no visible striations (looks like collagen). How are they interconnected and what do they produce?

Answer 2

Interconnected by gap junctions to help spread electrical current
Produces continuous contraction of low force: Rhythmic contraction that is inherent but responsive to ANS

Question 3

As skeletal muscle, smooth muscle contains contractile apparatus of thin and thick filaments. What are they anchored to and what are those made of?

Answer 3

Filaments anchor to cytoplasmic densities/dense bodies which are comprised of desmin and vimentin intermediate filaments

Question 4

How does contraction work and what shape does the smooth muscle assume?

Answer 4

Tension is trasmitted via densities to the membrane and the cells contract as one unit and assume globular shape

Question 5

What are caveolae?

Answer 5

Indents on the smooth muscles whicha are equal to T tubules in skeletal M

Question 6

Cardiac Muscle is short, branched and Y-shaped with more centrally located nuclei. They have extensive capillaries because the heart needs alot of O2. What are the two main hallmarks of cardiac muscle?

Answer 6

Intercalated discs and purkinje cells

Question 7

What are intercalated discs?

Answer 7

Transverse junctions at the ends of cells that allow passage of electrical currents & communication

Question 8

What are purkinje cells?

Answer 8

Modified cardiac muscle cells that act as the pacemaker for the heart

Question 9

Fibrous pericardium is the outer covering of dense connective tissue. What are the 3 components of serous pericardium?

Answer 9

1. parietal serous pericardium : inner surface of fibrous
2. Visceral serous pericardium: covers outer surface heart (EPICARDIUM)
3. pericardial cavity is space between parietal and visceral

Question 10

What are the three layers of the heart wall?

Answer 10

Epicardium
Myocardium
Endocardium

Question 11

Epicardium is ther outermost layer of the heart, and can also be called visceral serous pericardium. What is in this layer?

Answer 11

Simple squamous epithelium - Mesothelium
and dense fibrocollagenous CT with elastic fibers

**coronary artery branches embedded in adipose tissue

Question 12

The thickest layer of the heart is the myocardium. What are the three different things that compose it?

Answer 12

Cardiomyocytes which are contractile
Nodal cardiomyocytes (purkinje) in SA/AV node
Myoendocrine cardiomyocytes

Question 13

What is the difference between skeletal and cardiac muscles regarding T tubules?

Answer 13

Cardiac have Dyad (diad) T tubules which skeletal have triad

Question 14

What are the main characterizations of myocardium? (6)

Answer 14

Striations
intercalated discs
Dyad T tubule system
LOTS of mitochondria
Lipofuscin granules
atrial granules (myoendocrine cells)

Question 15

Intercalating discs connect cardiomyocytes where and for what function?

Answer 15

Connect always at Z lines, where cells meet end to end

They bind cells, transmit forces of contraction and spread excitation/electrical signaling

Question 16

What are the three types of membrane to membrane contacts of intercalating junctions?

Answer 16

Transverse region (perpendicular to cell striations): 1. fascia adherens and 2. desmosomes
Longitudinal region (parallel to cell striations): 3. gap (Nexus) junctions

Question 17

What are actin filaments at the ends of terminal sarcomeres that insert into the junction and transmit contractile forces between cells? **most predominant kind of intercalating disc

Answer 17

Fascia adherins

Question 18

What provide anchorage for the intermediate filaments of the cytoskeleton?

Answer 18

Desmosomes

Question 19

What are sites of low electrical resistance that allow excitation to pass between cells?

Answer 19

Gap/Nexus junctions

Question 20

Dyad T-tubules consist of 1 T tubules and 1 SR cisterna (Ca2+), and can be found where and do what?

Answer 20

Found at Z lines, in fewer quantity that Triad

Permits uniform contraction of myofibrils within a single cardiomyocyte

Question 21

Lipofuscin granules are small bodies that accumulate with age in non-dividing cells… What do they contain?

Answer 21

material derived from residual bodies after lysosomal disgestion

Question 22

Myoendocrine cells are atrial cardiomyocytes that contain membran bound granules (small amount found in left atrium and ventricles) which contain what to do what?

Answer 22

Contain precursor of atrial natriuretic factor (ANF) and brain factor BNF which targets kidney to decrease H+ and H20 retention

Question 23

The endocardium is NOT thick walled and contains simple squamous endothelium and a thin layer of loose CT. Why does thickness differ in ventricles vs atria?

Answer 23

Ventricular endocardium has a subendocardial layer with a thin layer of CT with smooth muscle and contains purkinje fibers

Question 24

What is different about endocardium in the atria?

Answer 24

Purkinje fibers are often closer to the endothelium and intermixed with myocardium

Question 25

What is important to remember about nodal (purkinje) myocytes, which are modified cells within SA/AV nodes that initiate/relay electrical signals?

Answer 25

They do not have intercalated discs!

Question 26

What do parasympathetic and sympathetic fibers that terminate in the AV/SA nodes MODIFY?

Answer 26

rate of intrinsic cardiac muscle contraction

Question 27

Purkinje fibers are highly specialized conducting fibers that generate and transmit impulse. Where are they seen and what do they lack?

Answer 27

They are larger and seen at the periphery of myocardium and they mostly lack T Tubules

Question 28

Cardiac (fibrous) skeleton is made up of dense irregular CT located in the endocardium. It anchors valves and surrounds AV canals to maintain shape. What are the other two things that it does?

Answer 28

1. Contribues to interventricular and interatrial septa
2. extends into the valve cusps and chordae tendineae where is serves as an electrical insulator between atria and ventricles

Question 29

Heart valves are extensions of endocardium and have a core of fibroelastic CT (lamina fibrosa) covered by endothelium. What does this layer function in?

Answer 29

Condenses to form a valve ring (VR) which creates the central portion of the valve