EX1; Cardiac Muscle Flashcards

1
Q

What is the one main feature of cardiac muscle that distinguishes it from skeletal muscle

A

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

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2
Q

What two contractile proteins are found in both skeletal and cardiac muscle

A

one of the myosin heavy chains (beta)

the troponin C in slow (but not fast skeletal muscle)

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3
Q

This contractile protein is expressed in cardiac muscle but not so much skeletal muscle (except masseter)

A

cardiac myosin heavy chain (alpha)

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4
Q

A unique isoform of this is expressed in cardiac muscle

A

troponin I

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5
Q

True or False

Nebulin is present in cardiac sarcomeres

A

False; it is not

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6
Q

This organelle is much larger in cardiac muscle than in skeletal muscle

A

mitochondria

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7
Q

Cardiac muscle cells are much smaller or larger than skeletal muscle cells

A

smaller

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8
Q

How are cardiac cells attached to one another compared to skeletal muscle cells

A

cardiac cells are attached end-on-end to each other via the physical connection of an intercalated disk
skeletal cells are attached to endows

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9
Q

Small regions along each intercalated disk that are further specialized for the rapid and direct transmission of action potentials between adjacent cells are what

A

gap junctions

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10
Q

Gap junctions allow for the heart to function as one unit, how?

A

They allow the quick passage of action potentials throughout all the ventricular cells simultaneously

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11
Q

The electrical synapses of the heart does not involve this

A

chemical transmitters for AP transmission

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12
Q

Where else would you find gap junctions besides the heart

A

in the brain tissues

not present in skeletal muscles

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13
Q

True or False

The events in the heart are much slower

A

True; the AP in ventricular cells ~200ms, AP in skeletal muscles ~3ms

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14
Q

The AP in cardiac muscle lasts until when, whereas in skeletal muscle the AP is complete before muscle even begins to shorten

A

twitch tension is relaxed

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15
Q

Why does the heart have such a long absolute refractory period during the cardiac AP

A

it prevents the heart from undergoing a tetanic contraction which could, otherwise, be life threatening

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16
Q

What is the first phase conductance changes (after depolarization) during ventricular action potential

A

Kꜛ
Naꜜ
(less NA coming into cell)

17
Q

What is the second phase conductance change during ventricular AP

A

Caꜛ

Kꜜ

18
Q

The “decrease” of K conductance in phase 2 allows for what to occur

A

it keeps the voltage gated Ca channel open

19
Q

What is the third phase conductance change during ventricular AP

A

Kꜛ
Caꜜ
decrease in Ca, major increase in K

20
Q

What is the fourth phase conductance change during ventricular AP

A

essentially no net flow

21
Q

What is the major source of activating Ca ions in the heart

A

they enter cells from interstitial space by passing through channels in sarcolemma during plateau phase of AP

22
Q

The activating Ca from the interstitial space somehow trigger what

A

the release of other Ca ions from the sarcoplasmic reticulum which binds to troponin C and causes activation of cardiac muscle

23
Q

What is the name of the process in which interstitial space Ca ions induce the SR to release Ca

A

calcium induced calcium release

24
Q

The primary mechanism for the removal of Ca ions from the sarcoplasm utilizes what

A

a Ca ATPase pump

another pump like this moves ions out of the cell across the sarcolemma

25
Q

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

A

Na/Ca exchanger

26
Q

There is a secondary action transport involving the Na/Ca exchanger which maintains what

A

It consumes ATP to maintain difference in Na concentrations

27
Q

Which source an removal system of Ca involves massive quantities

A

Source; Ca ions from SR

Removal; Uptake by SR (it isn’t really shuttled out, it just is moved around)