Cardiac Muscle Question

[y0ssarian]

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Hey guys, I had this problem on a practice test in the biology section:

Cardiac muscle:
a. is innervated by the somatic motor
b. is not striated
c. is multi-nucleated
d. has voluntary contraction
e. does not require Ca2+

Could someone answer this question, and explain their choice? If needed, I can post the answer the book gives, but I think their reasoning is wrong.

 

[Thundercatz]

Hey guys, I had this problem on a practice test in the biology section:

Cardiac muscle:
a. is innervated by the somatic motor
b. is not striated
c. is multi-nucleated
d. has voluntary contraction
e. does not require Ca2+

Could someone answer this question, and explain their choice? If needed, I can post the answer the book gives, but I think their reasoning is wrong.

I think its all wrong or the Answer is E. They may contain Ca2+ but it isnt required? hehe

A is incorrect as it is innervated by the ANS.

B is incorrect as cardiac muscle is striated as they consist of myosin and actin (thick/thin filament).

C is incorrect as only skeletal muscle is multi-nucleated

D is incorrect as skeletal muscle is voluntary and cardiac/smooth are involuntary. Skeletal muscle is voluntary as it is innervated by the somatic nervous, which is voluntary. Cardiac/smooth muscle is innervated by the ANS, which is involuntary.

E. I believe Cardiac muscles do require Ca 2+ as they contain sacromeres.

 

[boxdesker]

From Wikipedia: http://en.wikipedia.org/wiki/Cardiac_muscle
"In contrast to skeletal muscle, cardiac muscle cannot contract in the absence of extracellular calcium ions as well as extracellular sodium ions"

I'm going to go ahead and say that there is a flaw with the question posted.

 

[Simiam]

This question was on another thread. The answer is D.

 

[baedero1]

i think the answer is D, b/c the heart contracts automatically by SA node in the right artium.

 

[boxdesker]

I would appreciate an explanation for how in the WORLD cardiac muscle has voluntary control?
I mean I can voluntarily eat lots of saturated fats and cholesterol and "voluntarily" stop my heart, but I don't think that counts...

 

[Shjfr]

I would appreciate an explanation for how in the WORLD cardiac muscle has voluntary control?
I mean I can voluntarily eat lots of saturated fats and cholesterol and "voluntarily" stop my heart, but I don't think that counts...

Hahaha. Yeah... cardiac muscle is NOT voluntary... last time I checked...

 

[Shjfr]

i think the answer is D, b/c the heart contracts automatically by SA node in the right artium.

The answer to D is "cardiac muscle is voluntary"

Your statement says that the hearts contracts "automatically"

I believe that is a contradiction...

 

[drgreen]

Te answer is F) none of the above

 

[Thundercatz]

Well,

I did some reading and it does seem like D is the answer. The heart is innervated by the ANS (which is involuntary), but the ANS does not control the contraction of the heart.

The heart contracts automatically by the sinoatrial node.

Guess I learned something today!😀

 

[y0ssarian]

Well,

I did some reading and it does seem like D is the answer. The heart is innervated by the ANS (which is involuntary), but the ANS does not control the contraction of the heart.

The heart contracts automatically by the sinoatrial node.

Guess I learned something today!😀

If the heart contracts automatically, doesn't that mean it's not voluntary?

 

[boxdesker]

If the heart contracts automatically, doesn't that mean it's not voluntary?

Correct. I'm not completely understanding what some of these posters are trying to say. They make excellent cases for why cardiac muscle is "automatic" then use that to reach the conclusion that it's "voluntary". Is this the same answer the book gives?

 

[Thundercatz]

In this case, it is voluntary because it is "automatically" controlled by the SA node. Its a tricky question. Cardiac muscle is in fact involuntary, but it has voluntary "contraction." Contraction is the key word in the answer choice. Where did this question come from?

To further explain this so nobody is confused. The Sinoatrial Node is the "pacemaker," so it starts or initiates the the normal heart beat, this aspect is voluntary. However, the heart is able to beat faster/slower by the control of the ANS. This aspect of the heart is involuntary. In summary, SA node initiates (voluntary) and the ANS controls the rate (involuntary).

This is a very good question! Thanks for posting it.

 

[Danny289]

I had to check my A&P book. it is somthing there but you find the answer lol:
A&P Marttini 7th Edition page 134:
" A typical cardiac muscle cell has one centerally poisitoned nucleus, but some cardiocytes have as many as five." 😕
maybe is sleeping time lol

 

[y0ssarian]

In this case, it is voluntary because it is "automatically" controlled by the SA node. Its a tricky question. Cardiac muscle is in fact involuntary, but it has voluntary "contraction." Contraction is the key word in the answer choice. Where did this question come from?

The question came from Kaplan's 2007-2008 DAT book. They did give D as the answer. I still don't understand how automatic equates to voluntary, as it's usually associated with involuntary actions, like smooth muscle contractions.

 

[Shjfr]

In this case, it is voluntary because it is "automatically" controlled by the SA node. Its a tricky question. Cardiac muscle is in fact involuntary, but it has voluntary "contraction." Contraction is the key word in the answer choice. Where did this question come from?

To further explain this so nobody is confused. The Sinoatrial Node is the "pacemaker," so it starts or initiates the the normal heart beat, this aspect is voluntary. However, the heart is able to beat faster/slower by the control of the ANS. This aspect of the heart is involuntary. In summary, SA node initiates (voluntary) and the ANS controls the rate (involuntary).

This is a very good question! Thanks for posting it.

So the SA node voluntarily initiates contraction of cardiac muscle?

I'm going to pretend I never read this thread and carry on with my studies...

 

[creative8401]

Hi everyone. Hope you all had a great day. Let's take a look at this question, and yes I agree its a tricky one, but doable. Ok..

Cardiac muscle, as everyone surely knows, is involuntary. Meaning that yes you cannot simply say "heart speed up", and it will follow orders. No, it does not work that way....I hope you all agree .

But please take a look at the question again, and choice D. Now, there is a difference between voluntary contraction and voluntary control. I believe we are all very tied up with the word voluntary and not looking at the second part of choice D. Yes, even though the heart is involuntary as in you mentally have no control over it, it however contracts voluntary. In other words, you cant voluntary control ("I'm thinking I want my heart to speed up...nooo) it, but the heart will voluntary contract (thanks to the SA node). Many students were on the right path by saying that voluntary means "automaticity", but that makes it difficult to understand. Thus the question is the difference between voluntary control versus contraction.

Hope this helps. Goodnite.

 

[y0ssarian]

That makes more sense, thanks.

 

[Simiam]

Hi everyone. Hope you all had a great day. Let's take a look at this question, and yes I agree its a tricky one, but doable. Ok..

Cardiac muscle, as everyone surely knows, is involuntary. Meaning that yes you cannot simply say "heart speed up", and it will follow orders. No, it does not work that way....I hope you all agree .

But please take a look at the question again, and choice D. Now, there is a difference between voluntary contraction and voluntary control. I believe we are all very tied up with the word voluntary and not looking at the second part of choice D. Yes, even though the heart is involuntary as in you mentally have no control over it, it however contracts voluntary. In other words, you cant voluntary control ("I'm thinking I want my heart to speed up...nooo) it, but the heart will voluntary contract (thanks to the SA node). Many students were on the right path by saying that voluntary means "automaticity", but that makes it difficult to understand. Thus the question is the difference between voluntary control versus contraction.

Hope this helps. Goodnite.

Great explanation, much better than my "The answer is D." hehe

 

[HoangDDS]

Hey guys, I had this problem on a practice test in the biology section:

Cardiac muscle:
a. is innervated by the somatic motor
b. is not striated
c. is multi-nucleated
d. has voluntary contraction
e. does not require Ca2+

Could someone answer this question, and explain their choice? If needed, I can post the answer the book gives, but I think their reasoning is wrong.

I just took the Kaplan's full length test #1, and this was question #32 in the bio section and the orginal poster of this thread missed type the question or had an older version. I have the 08-09 edition. Anyways choice D is actually "has involuntary contraction" . Which Is the correct answer for the above question.

 

[Streetwolf]

Good job people, you were given the correct answer choice and came up with false facts to justify it 😉

The muscle is NOT voluntary in any way, shape, or form. The SA node is not voluntary. It fires when it fires and there is no way you can control it by thought alone. The closest you can come really is activating parasymp or symp to control the rate, but it's still going to contract whether you like it or not.