20.5 histology

Question 1

what is the fibrous ring around the valves?

Answer 1

heart skeleton

Question 2

what are the fn of the heart skeleton?

Answer 2

supports valves
electrical insulation btwn atria and ventricles
provides a site for muscle attachment

Question 3

describe a cardiac muscle cell

Answer 3

elongated, branching, 1-2 centrally located nuclie

Question 4

what are the contractile proteins of cardiac muscle cells?

Answer 4

actin and myosin myofilaments

Question 5

what are the specialized cell-to-cell connections in cardiac muscle cells?

Answer 5

intercalated discs

Question 6

describe an intercalated disc

Answer 6

cell membranes interdigitate at ends
desmosomes act as staples to attach cells
gap junctions allow AP to move from one cell to the next

Question 7

electrically, cardiac muscle cells of each atria and ventricle behave

Answer 7

as a single unit

Question 8

describe the difference between the sarcoplasmic reticulum of cardiac and skeletal muscle cells

Answer 8

cardiac do not have a dilated terminal cisternae and comes in contact with t-tubule at various points
skeletal have dilated terminal cisternae and lie close to the t-tubule at one point only

Question 9

where do the t-tubules form in cardiac muscle fibers?

Answer 9

at the z disks

Question 10

do cardiac or skeletal muscle fibers have larger t-tubules?

Answer 10

cardiac

Question 11

how is the orientation of t-tubules and sarcoplasmic reticulum of cardiac muscle cells responsible for the delayed onset of cntx and prolonged cntx phase

Answer 11

it is a casual orientation, not designed for easy access to ion movement/AP movement

Question 12

what is the SA node and where is it located?

Answer 12

sinoatrial node

medial to the opening of the superior vena cava

Question 13

what is the pacemaker of the heart

Answer 13

SA node

Question 14

what is the SA node made of?

Answer 14

specialized cardiac muscle cells

Question 15

how are the muscle cells of the SA node specialized?

Answer 15

they generate their own spontaneous AP

Question 16

where does the AP travel after being generated in the SA node?

Answer 16

to the atrial muscle cells (to cntx)

to the AV node

Question 17

what is the AV node and where is it located?

Answer 17

atrioventricular node

medial to the tricuspid valve

Question 18

what are APs conducted more slowly in the AV node than other parts of the conducting system?

Answer 18

it ensures the ventricles only cntx after the atria have completed their cntx

Question 19

where is the AV bundle located?

Answer 19

it passes through a hole in the cardiac skeleton to reach the interventricular septum

Question 20

what do the R and L AV branches travel through and what is their destination

Answer 20

extend beneath the endocardium to apices of R and L ventricles

Question 21

what are the purkinje fibers?

Answer 21

large diameter cardiac muscle cells that form myofibrils at the apices of the ventricles

Question 22

describe the route of electrical current (AP) in the heart

Answer 22

originate in the SA nodes
to AV node
along AV bundle
splits into R and L bundle branches
purkinje fibers
ventricle walls and papillary muscles

Question 23

what differentiates purkinje fibers from other cardiac cells?

Answer 23

many cap junctions