Intercalated discs connect cardiac muscle fibers into a functional syncytium Flashcards
describe cardiac muscle cells
striated short fat branched interconnected use sliding filament mechanism
describe cardiac muscles in term of nucleus
contains one or at most two large, pale, centrally located nuclei
In contrast, the plasma membranes
of adjacent cardiac cells interlock like the ribs of two sheets of
corrugated cardboard at dark-staining junctions called
intercalated discs
Intercalated discs contain anchoring________ and__________
desmosomes
gap junctions
The ______ prevent adjacent cells from separating during contraction, and the _____ allow ions to pass from cell to cell transmitting current across the entire heart
desmosomes
gap junctions
Because gap junctions electrically couple cardiac cells, the myocardium behaves as a single coordinated unit, or
functional syncytium
why is it significant that cardiac cells have 25% to 35% mitochondria in comparison to skeletal muscle having 2%
it makes them highly resistant to fatigue which is important because the heart is working all the time and if stops you are dead :(
in contrast to skeletal muscle, the myofibrils of cardiac muscle cells vary greatly in ____ and _____ extensively, accommodating the abundant ______between them.
diameter
branch
mitochondria
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.
less simpler lacks triads wider fewer
Some cardiac muscle cells are ____ excitable
self
what are the 2 kinds of myocytes in the heart
contractile cardiac muscle cells
pacemaker cells
responsible for the heart’s pumping
activity
contractile cardiac muscle cells
certain locations in the heart contain special noncontractile cells, called ____ cells, that spontaneously depolarize.
pacemaker
what is the special property of the heart called in terms of self excitability
automaticity
autorhythmicity
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 \_\_\_\_
depolarization
heart
if you cut all of the nerves of the heart will it still beat
yes, because it requires no neutral input
the heart contracts as a ____
unit
all fibers in the heart contract as a ____ or the heart ________
unit
doesn’t contract at all
recruitment cannot happen in the heart
because it acts as a
single huge motor unit.
The influx of Ca2+ from extracellular fluid triggers
Ca2+
release from the SR
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
special Ca2+ channels
slow
sensitive
80-90%
Tetanic contractions ______ occur in cardiac muscles
cannot
If the heart were to contract tetanically, it would be ___________-, and so would be _____ as a pump
unable to relax and fill
useless
The absolute refractory period in the heart is nearly ______________, which prevents ________ contractions.
as long as the contraction itself
tetanic
which type of respiration does the heart depend on
aerobic
Consequently, the real danger of an inadequate blood supply to the myocardium is not
lack of nutrients, but lack of
oxygen
