The Dreaded HAZIM – H-zones, A-bands, Z-lines, I-bands, and the M-line

Posted by on Oct 1, 2013 in Exam Preparation, Exercise Science, Review Topics | 0 comments

HAZIM is the mnemonic device I’m using to remember all the various zones, lines, and bands related to a sarcomere.

As you’ll recall from my previous post we discussed how myosin fits inside multiple actin filaments much in the same way as a piston fits inside a cylinder.


Let’s look at the image from the wikipedia page on sarcomere:


Sarcomere. Source: Creative Commons

This image is very useful, but it misses the last portion of the mnemonic, M-line (or M-bridge, the NSCA book uses both terms).


Microscopic image of sarcomere with M-line called out

Now take a look back in the NSCA book, and you will find some images that give you a cross-sectional depiction of what each zone looks like.  Here is my re-creation of the various bands:


A-band I-band M-line

Keep in mind the A-Band image is operating under the assumption that we are looking at a portion of the A-band that has both actin and myosin filaments, if we look in the H-zone (myosin only) it would look the same minus the green circles.


I couldn’t come up with any better mnemonic than HAZIM, which I have included below superimposed over a Reddit rage face…who for the purposes of this page we can refer to as the character Hazim.


HAZIM – Now associated with a reddit rage face due to lack of creativity on my part


Anyways, if you know the word HAZIM, and you have a structural representation of a sarcomere in your brain…that is you know that actin has to be anchored somewhere, myosin has to be anchored somewhere, and you remember that myosin slides between actin filaments much like a piston in a cylinder, you should be able to recreate a drawing of a sarcomere on paper.

In fact, do that.  Now.  Use the HAZIM mnemonic to remember that there are different zones and lines that start with those letters, and then identify them on your drawing.  Two lines, Two bands, and 1 zone…should be easy enough =).

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