Bio 436 Lecture 7 Cardiac Cells Test Questions and Correct Answers
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Course
BIO 436
Institution
BIO 436
Sarcomere The basic unit of muscle contraction.
A unit of proteins between Z-discs
Thin Filaments (actin, tropomyosin, troponin) Thick Filaments (myosin) Stabilizer proteins (titin, nebula)
Sequential events of contraction Ca+ binds to troponin> moves tropomyosin exposing actin> 1. Cross b...
Sequential events of contraction ✅Ca+ binds to troponin> moves tropomyosin
exposing actin>
1. Cross bridging myosin to actin
2. Power stroke ADP & P released
3. Detachment binding of ATP
4. Cocking of myosin head ATP split into ADP & P
Cardiac and Skeletal Muscle Similarities ✅Microscopically similar to skeletal muscle in
many ways:
- Basic contractile unit is the sarcomere
Cardiac and Skeletal Muscle Differences ✅-cardiac fibers (cells) don't stretch length or
width of the heart (more individual and normal sized cell)
-at the end of cells, they have the Intercalated discs with the desmosomes, gap
junctions
-cardiac muscle has very little SR
-majority of Ca++ for crossbridging comes from outside of the cell
-Cardiac muscles fibers cannot undergo tetanus due to long refractory period
Intercalated discs ✅Cardiac fibers form these where they meet, in which the cell
membranes interdigitate extensively
Desmosomes ✅form tight connections so that cardiac cells don't pull apart during
contractions.
-proteins inside the cell that form as an anchor
"velcro"
, Gap junctions ✅provide channels for electrical continuity and propogation throughout
the heart
made up of proteins called connexions?
-All ions can pass through Na+, K+, Ca+
Syncitium ✅Cells that are linked together via gap junctions
with many respects they act like one large cell.
one of the atria and another on the ventricles
Myogenic ✅Because of the autorhythmic cells which are linked to the contracting cells
through gap junctions, the atrial and ventricular cells are referred to as __________?
SA node ✅pacemaker cells
located in the right atrium
dictates heartbeat
show the fastest rate of spontaneous depolarization
1% of total cells
Action potentential of Pacemaker cell ✅No sarcomeres in pacemaker cells
HCN (hyperpolarized- activated cyclic-nucleotide channels) ✅contained in all
pacemaker cells (leaky channels)
Spontaneous depolarization is caused by Na+ flowing through channel that opens when
hyper polarized
cannot stop polarizing
Sinus venosus ✅frog's SA node
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