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Health Science 2211- Lecture 2
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what is the cardiac muscle called that forms the wall of the heart?
myocardium
how are the muscles arranged in the myocardium?
spiral and circular bundles
The heart's four chambers must beat in an ______________.
organized manner
When does a chamber of the heart contract?
when an
electrical impulse
moves across it
Concentric layers of
cardiac muscle cells
are called?
cardiomyocytes
Describe the structure of cardiomyocytes.
short, fat, branched, striated cells
with a
central nucleus
interconnected by
intercalated discs
what are intercalated discs?
areas where the
plasma membranes intermesh
what are the 2 ways that intercalated discs connect adjacent cardiac muscle cells?
desmosomes
gap junctions
Define desmosome.
tight seals
that
weld
the
plasma membranes
together
Define gap junctions.
ionic channels
responsible for propagation of electrical signal from cell to cell during muscle contraction
what does intercalated discs enable?
enable
synchronized contraction
of muscle fibers (atria and ventricles contract at the same time)
what is the sarcolemma?
plasma membrane
of muscle cell
what are T (transverse) tubules?
tiny invaginations of the sarcolemma
that quickly
spread electrical signal
to all parts of the muscle fiber
during contraction
Muscle fibers are filled with bundles of threads called?
myofibrils
what do myofibrils consist of?
consist of
thick and thin filaments
which are the
contractile structure
of muscle
what is a sarcomere? (structure in myofibrils) Where is it found? (2)
group of
overlapping thin and thick filament
s
each sarcomere is found
between 2 Z discs
what are striations?
when a
thick and thin filaments overlap
each other in a pattern
what happens to filaments during contraction and relaxation of the muscles?
they
slide
past each other
what is the heartbeat?
single sequence
of atrial contraction followed by a ventricular contraction
what controls the heartbeat? Describe it.
special tissue called
nodal tissue
has characteristics of
both nerve and muscle tissue
Cardiac muscle cells in nodal tissue are
authorthytmic
,
what does this mean?
self-excitable
can generate electrical impulses without an external stimulus
where are the authorthytmic nodal cells located?
in the
cardiac conduction system
What is the Sinoatrial (SA) node and where is it located?
it's the
pacemaker
of the heart
cluster of cells in
wall of right atrium
what is the function of the SA node?
begins an
action potential
followed by
contraction of both atria
, expelling contents into ventricles
What is the atrioventricular (AV) node? and where is it located?
transmits electrical signals to AV
Bundle (bundle of His)
located in
atrial septum
what is the atrioventricular (AV) bundle?
Bundle of His
only place where signal can be transmitted from atria and ventricles
what is the difference between systole and diastole?
systole
: contraction
diastole
: relaxation; filling
what is the ECG or EKG?
a
recording of the electrical changes
that accompany the cardiac cycle
what does the
P wave
indicate?
atrial contraction
what does the
QRS complex
indicate?
rapid ventricular contraction
what does the
T wave
indicate?
ventricular relaxation
______________ system can increase or decrease heart rate.
Nervous
what 5 things influence heart rate?
hormones (epinephrine)
age
gender
physical fitness
body temperature
Author
CanuckGirl
ID
256377
Card Set
Health Science 2211- Lecture 2
Description
heart physiology
Updated
1/14/2014, 6:59:36 AM
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