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