EX1; Cardiac Muscle

Question 1

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

Answer 1

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

Question 2

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

Answer 2

one of the myosin heavy chains (beta)

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

Question 3

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

Answer 3

cardiac myosin heavy chain (alpha)

Question 4

A unique isoform of this is expressed in cardiac muscle

Answer 4

troponin I

Question 5

True or False

Nebulin is present in cardiac sarcomeres

Answer 5

False; it is not

Question 6

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

Answer 6

mitochondria

Question 7

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

Answer 7

smaller

Question 8

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

Answer 8

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

Question 9

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

Answer 9

gap junctions

Question 10

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

Answer 10

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

Question 11

The electrical synapses of the heart does not involve this

Answer 11

chemical transmitters for AP transmission

Question 12

Where else would you find gap junctions besides the heart

Answer 12

in the brain tissues

not present in skeletal muscles

Question 13

True or False

The events in the heart are much slower

Answer 13

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

Question 14

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

Answer 14

twitch tension is relaxed

Question 15

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

Answer 15

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

Question 16

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

Answer 16

Kꜛ
Naꜜ
(less NA coming into cell)

Question 17

What is the second phase conductance change during ventricular AP

Answer 17

Caꜛ

Kꜜ

Question 18

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

Answer 18

it keeps the voltage gated Ca channel open

Question 19

What is the third phase conductance change during ventricular AP

Answer 19

Kꜛ
Caꜜ
decrease in Ca, major increase in K

Question 20

What is the fourth phase conductance change during ventricular AP

Answer 20

essentially no net flow

Question 21

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

Answer 21

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

Question 22

The activating Ca from the interstitial space somehow trigger what

Answer 22

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

Question 23

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

Answer 23

calcium induced calcium release

Question 24

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

Answer 24

a Ca ATPase pump

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

Question 25

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

Answer 25

Na/Ca exchanger

Question 26

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

Answer 26

It consumes ATP to maintain difference in Na concentrations

Question 27

Which source an removal system of Ca involves massive quantities

Answer 27

Source; Ca ions from SR

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