EX1; Cardiac Muscle Flashcards
What is the one main feature of cardiac muscle that distinguishes it from skeletal muscle
the filaments in cardiac sarcomeres are not all the same length; possibly related to the need of the heart to pump blood following different amounts of dissension during filling
What two contractile proteins are found in both skeletal and cardiac muscle
one of the myosin heavy chains (beta)
the troponin C in slow (but not fast skeletal muscle)
This contractile protein is expressed in cardiac muscle but not so much skeletal muscle (except masseter)
cardiac myosin heavy chain (alpha)
A unique isoform of this is expressed in cardiac muscle
troponin I
True or False
Nebulin is present in cardiac sarcomeres
False; it is not
This organelle is much larger in cardiac muscle than in skeletal muscle
mitochondria
Cardiac muscle cells are much smaller or larger than skeletal muscle cells
smaller
How are cardiac cells attached to one another compared to skeletal muscle cells
cardiac cells are attached end-on-end to each other via the physical connection of an intercalated disk
skeletal cells are attached to endows
Small regions along each intercalated disk that are further specialized for the rapid and direct transmission of action potentials between adjacent cells are what
gap junctions
Gap junctions allow for the heart to function as one unit, how?
They allow the quick passage of action potentials throughout all the ventricular cells simultaneously
The electrical synapses of the heart does not involve this
chemical transmitters for AP transmission
Where else would you find gap junctions besides the heart
in the brain tissues
not present in skeletal muscles
True or False
The events in the heart are much slower
True; the AP in ventricular cells ~200ms, AP in skeletal muscles ~3ms
The AP in cardiac muscle lasts until when, whereas in skeletal muscle the AP is complete before muscle even begins to shorten
twitch tension is relaxed
Why does the heart have such a long absolute refractory period during the cardiac AP
it prevents the heart from undergoing a tetanic contraction which could, otherwise, be life threatening
What is the first phase conductance changes (after depolarization) during ventricular action potential
Kꜛ
Naꜜ
(less NA coming into cell)
What is the second phase conductance change during ventricular AP
Caꜛ
Kꜜ
The “decrease” of K conductance in phase 2 allows for what to occur
it keeps the voltage gated Ca channel open
What is the third phase conductance change during ventricular AP
Kꜛ
Caꜜ
decrease in Ca, major increase in K
What is the fourth phase conductance change during ventricular AP
essentially no net flow
What is the major source of activating Ca ions in the heart
they enter cells from interstitial space by passing through channels in sarcolemma during plateau phase of AP
The activating Ca from the interstitial space somehow trigger what
the release of other Ca ions from the sarcoplasmic reticulum which binds to troponin C and causes activation of cardiac muscle
What is the name of the process in which interstitial space Ca ions induce the SR to release Ca
calcium induced calcium release
The primary mechanism for the removal of Ca ions from the sarcoplasm utilizes what
a Ca ATPase pump
another pump like this moves ions out of the cell across the sarcolemma
This mechanism in the sarcolemma moves Na in and Ca out of the cell, does not use ATP, it is driven by a Na gradient
Na/Ca exchanger
There is a secondary action transport involving the Na/Ca exchanger which maintains what
It consumes ATP to maintain difference in Na concentrations
Which source an removal system of Ca involves massive quantities
Source; Ca ions from SR
Removal; Uptake by SR (it isn’t really shuttled out, it just is moved around)
