Intercalated discs connect cardiac muscle fibers into a functional syncytium

Question 1

describe cardiac muscle cells

Answer 1

striated
short
fat
branched
interconnected
use sliding filament mechanism

Question 2

describe cardiac muscles in term of nucleus

Answer 2

contains one or at most two large, pale, centrally located nuclei

Question 3

In contrast, the plasma membranes
of adjacent cardiac cells interlock like the ribs of two sheets of
corrugated cardboard at dark-staining junctions called

Answer 3

intercalated discs

Question 4

Intercalated discs contain anchoring________ and__________

Answer 4

desmosomes

gap junctions

Question 5

The ______ prevent adjacent cells from separating during contraction, and the _____ allow ions to pass from cell to cell transmitting current across the entire heart

Answer 5

desmosomes

gap junctions

Question 6

Because gap junctions electrically couple cardiac cells, the myocardium behaves as a single coordinated unit, or

Answer 6

functional syncytium

Question 7

why is it significant that cardiac cells have 25% to 35% mitochondria in comparison to skeletal muscle having 2%

Answer 7

it makes them highly resistant to fatigue which is important because the heart is working all the time and if stops you are dead :(

Question 8

in contrast to skeletal muscle, the myofibrils of cardiac muscle cells vary greatly in ____ and _____ extensively, accommodating the abundant ______between them.

Answer 8

diameter
branch
mitochondria

Question 9

The system for delivering Ca2+ is ____ elaborate in cardiac muscle cells. The cardiac sarcoplasrnic reticulum is ____ and ____ the large terminal cisterns seen in skeletal muscle. As a result, cardiac muscle fibers do not have ____. In addition, the
T tubules are ____ and ____ than in skeletal muscle.

Answer 9

less
simpler
lacks
triads
wider
fewer

Question 10

Some cardiac muscle cells are ____ excitable

Answer 10

self

Question 11

what are the 2 kinds of myocytes in the heart

Answer 11

contractile cardiac muscle cells

pacemaker cells

Question 12

responsible for the heart’s pumping

activity

Answer 12

contractile cardiac muscle cells

Question 13

certain locations in the heart contain special noncontractile cells, called ____ cells, that spontaneously depolarize.

Answer 13

pacemaker

Question 14

what is the special property of the heart called in terms of self excitability

Answer 14

automaticity

autorhythmicity

Question 15

Because heart cells are electrically
joined together by gap junctions, these
cells can initiate not only their own
\_\_\_\_\_-, but also that of the rest
of the \_\_\_\_

Answer 15

depolarization

heart

Question 16

if you cut all of the nerves of the heart will it still beat

Answer 16

yes, because it requires no neutral input

Question 17

the heart contracts as a ____

Answer 17

unit

Question 18

all fibers in the heart contract as a ____ or the heart ________

Answer 18

unit

doesn’t contract at all

Question 19

recruitment cannot happen in the heart

because it acts as a

Answer 19

single huge motor unit.

Question 20

The influx of Ca2+ from extracellular fluid triggers

Answer 20

Ca2+

release from the SR

Question 21

In cardiac muscle, depolarization opens _________ in the plasma membrane. These _______ Ca2+ channels allow entry of 10-20% of the Ca2+ needed for contraction. Once inside, this influx of
Ca2+ triggers Ca2+ -_____channels in the SR to release bursts of Ca2+ (“calcium sparks”) that account for the other _______ of the Ca2+ needed for contraction

Answer 21

special Ca2+ channels
slow
sensitive
80-90%

Question 22

Tetanic contractions ______ occur in cardiac muscles

Answer 22

cannot

Question 23

If the heart were to contract tetanically, it would be ___________-, and so would be _____ as a pump

Answer 23

unable to relax and fill

useless

Question 24

The absolute refractory period in the heart is nearly ______________, which prevents ________ contractions.

Answer 24

as long as the contraction itself

tetanic

Question 25

which type of respiration does the heart depend on

Answer 25

aerobic

Question 26

Consequently, the real danger of an inadequate blood supply to the myocardium is not
lack of nutrients, but lack of

Answer 26

oxygen