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Lesson 9 - Muscle Physiology and Axial Musculature

Now that we've gotten through naming a whole bunch of stuff on the skeleton, we can move along and attach some muscles to bumps on the bone to then move this body around, and have the ability to stand with good posture!

But before we do that, let's find out a bit of how muscle tissue actually works. Please print out print out the lecture in the desired format here:
Muscle Physiology (full pager)
Muscle Physiology (2 per page)
Muscle Physiology (3 per page)

Please watch the following videos to prepare yourself for class.

Preview Questions  
(printable version)
9.1. We have learned before that muscles contract and actively shorten. That is their one, main activity they do all they long if required. How does the body use this quality?
9.2. When we look at how a muscle is built and consider what its qualities are, we mentioned the fact that it contracts. It also needs to be able to receive information of when to contract. The brain mostly controls our skeletal muscles, the ones that make us move around. Can you list other muscle characteristics?
9.3.  Reading anatomy language is often confusing and difficult. It’s like a foreign language. That is, because a lot of the words used are constructions of Greek or Latin pre- and suffixes. If you learn those, you will be able to understand that language much better. So, which 3 prefixes help us understand that we talk about muscle?
9.4.  Most of the time we think of muscles, we mean the ones that move us around in the world. We also have other ones that we don’t think too much about, but are equally important. Can you list the 3 types of muscle?
9.5.  A muscle mainly needs to contract. In order to know when to do that, a nerve has communicate with it. Muscles have three main specific organelles who make that possible. First, the cell membrane is specialized, in that it can be stimulated by a nerve and carry an impulse deep into the muscle via tubular extensions. What is the cell membrane in a muscle called?
9.6.  Then, our muscles have long, tubular organelles that contract. They lay parallel to one another and span the entire muscle length. What are those specialized organelles called?
9.7. Muscle contraction at its deepest level are two parallel arranged protein threads, with one pulling on the other. Interestingly, with ATP present, the pulling, or over a whole muscle, the contraction, is continuous, as long as calcium is present. Calcium makes the two threads be able to stick to one another. What is the organelle called that harbors the calcium?
9.8.  As we go deeper into the myofibril, the contractile muscle organelle, we discover the two protein threads. What is the thick one called  (The one with a head and tail)? What about the thin one?
9.9. During muscle contraction, the thick filament’s head attaches repeatedly to the thin filament and pulls on it. In physiology, we describe this process in a theory. What is it called?
9.10. Muscles contract when a nerve sends an impulse to them. It can connect to varied amounts of muscle fibers; all the muscle cells contract when stimulated. If a nerve innervates (connects to) many muscle cells, such as seen in your quad muscles in the front of the thigh, how do you think that muscle behaves as it comes to strength?
9.11. Muscle uses a ton of ATP. Most of that in a resting state is produced in the mitochondria, which a muscle has a lot of. However, if that is not enough, the muscle needs to be able to get energy from alternative sources. Remember ATP becoming ADP as it gives off energy? Good. In order to make the ADP back to a ATP molecule, a phosphate has to be attached. Thankfully, there is a molecule in the muscle having one of those it happily gives to the ADP. What is that molecule called?
9.12. Some muscles are concerned with posture. They have to contract for long periods of time, but are a little slower than others, who mainly move us around. The composition of a muscle is slightly different depending on what they are needed for. A postural muscle for example has more oxygen storage molecules (myoglobin) to assure long sustained contraction. What is the other main kind?
9.13. If we lift something off the ground, your arm muscles contract to raise the weight. When the muscle shortens during a contraction, we call it being an isotonic contraction. What do we call it when the muscle length doesn’t change?
9.14. Muscles come in many shapes to accommodate the different forces put upon them. One of the interesting differences between certain muscles is how the muscle fiber attaches to a tendon, which then anchors it to the bone. Parallel arranged fibers are long with limited lifting strength. When the fibers attach to the tendon in an angle, the individual muscle fibers are shorter, which gives them a greater lifting power. Those fibers kind of look like a feather. What do we call such a muscle fiber arrangement?
9.15. When muscles contract and shorten, they rub against other tissues. This can create heat, which expands a tissue and makes it inflamed. We see that in Carpal Tunnel Syndrome. What are some friction reducing structures?

Here is an audio of the in-class presentation on Muscle Physiology:

Now we can get started with some of these muscles. In this session the focus is on the axial muscles, the ones of the trunk and neck. We will cover the extremity muscles next after that.
This material has a lot to do with visualization of muscle, being able to name them, and understand the movement it produces as it shortens, or contracts. One good way to study the material are flashcards. Here is a handout that shows the individual muscles drawn with the bones. It's ideal to cut out and use as flashcards when memorizing the names. Study Help: Muscle Flashcard Labels
Moving right along. Here are the labelling pictures as well as a term list. Print those out and go through them as you watch the video. Hand the labelled pictures in at the beginning of class to get credit.

And here are the lecture handouts for the muscles of the axial skeleton:
Axial Musculature (full pager)
Axial Musculature (2 per page)
Axial Musculature (3 per page)

Please also watch these videos to prep yourself well for class:

Preview Questions  
(printable version)
9.16. We are now concerning ourselves with muscles of the trunk. First, some that move the head and neck. Most superficially in the back is a muscle that is anchored to the back of the head & all along the spine. From that broad origin, it reaches towards the tip of the shoulder. With these attachments, can you explain a couple of the ways the trapezius moves the head?
9.17. Another muscle, that moves the head around quite a bit is in the front of the neck. It anchors close to the midline into the sternum and clavicle. From there, it reaches up to the head behind the ear. Look at those attachments and visualize them approximating each other (coming closer together). When I do that, I better understand the action of a muscle, which helps me clinically, when I try to figure out which muscle might have gotten hurt by an injury. What is the name of the muscle with those attachments?
9.18. The next muscle is on the side of the neck. Push with your fingertips deep into the flesh above your clavicle and rub sideways. Is it tight in there? Painful? Do you feel a nervy, electricity like pain depending over what structure you rub? If you do, you felt a nerve underneath your fingers; one that carries messages from the neck (brain) into the arm. What is this muscle that reaches from the side (transverse process) of the cervical vertebrae to the upper ribs called?
9.19. This next muscle is deep in the front of the neck. It gets often injured during a car accident. When one’s head doesn’t touch the headrest it is free in space. If a car hits from behind and the vehicle is forcefully pushed forward, that head will lag behind and slam violently backwards. When the neck buckles backwards, the front of the neck overstretches and this deep muscle gets injured. Can you name the muscle?
9.20. We have a few more players in the back. Right underneath the occiput, there is a group of deep laying muscles that help move the head on the neck. They are also somehow neurologically wired to eye movements and deeply connect to strong fascia (collagen filled, ligament like connections through the body) in the back. These features makes that muscle group clinically interesting. Can you name this muscle group?
9.21. Overlying those muscles, and underneath the trapezius are a set of posterior back muscles. One runs straight up and down lying medial. The other’s fibers orient more diagonally from the midline towards the mastoid process of the temporal bone. Can you name those 2 muscles?
9.22. With that, let’s leave the neck. As we check out the back trunk musculature, we find a more superficial group generally reaching from the pelvic area upward. Some muscle fibers stay medial reaching up vertical, while others reach laterally onto the ribs. These superficial muscles are concerned with larger movements, such as side bending or trunk rotation. Can you name that group?
9.23. Deeper to that massive layer are many deep, deep muscles that attach right onto the different parts of the vertebrae. Some span from the outside of vertebrae (transverse process) below and reach diagonally towards the midline (Spinous processes) of vertebrae a few segments higher. Function of these deep muscles is crucial for low back stability and protection. It is one of the main one’s to activate and strengthen with any low back ailment / weakness. What muscle am I referring to?
9.24. Looking at the chest in the front guides us to muscles that lie in between ribs. There are 2 layers, an outside, and inside one. Which of the 2 helps raise the ribcage up and by doing that increase the lung volume?
9.25. When talking about breathing, I cannot stop being amazed by the next muscle that covers the rib-cage from underneath. It often is referred to as ‘parachute’ shaped because it reaches deep into the lung cavity. When it contracts, it shortens, which move it inferior. By doing that, the lung volume increases, and since the lungs attach to the rib-cage and this muscle, it makes us inhale. What is this muscle’s name?
9.26. And lastly when talking about the axial musculature, we will discuss the fronts and sides of our stomachs, our gut muscles. They lie behind our muffin tops and help us move our trunks, compress the abdominal contents, and most importantly, when strong, give us a solid foundation, from which the arms and legs can move from (core strength). All the muscles that wrap around the gut have some attachments to the lumbodorsal fascia in the back. In the front, they attach to a tough, fibrous tissue that reaches vertically from the pubic symphysis to xiphoid process. I like the name of that structure. Can you name it?
9.27. On the sides of our gut, we have two layers of diagonally oriented muscles. Their fiber direction are in near 90 degree angles to one another. This is great, because as it comes to trunk movements, they support one another greatly. This orientation also makes them very stabilizing. What two muscles am I describing?
9.28. This next animal is my favorite. And by the way, thinking evolutionarily and of us as a whole organism, muscle cells are in some ways individual animals and deserve to be treated well! One of the most important core muscles is the one that wraps horizontally around the gut. It is the deepest layer and in need of attention in most of us who sit more then occasionally. Can you name this muscle?
9.29. And, last but not least, the 6-pack muscle, the most superficial one. Can you name it?

Here is the Anatomy Academy handout describing the muscles that we're discussing in class. It's not mandatory to print it, but it is useful for the student who likes to read and visualize terms that way.

For the nerdy types like me, I have a link to a muscle cadaver videos that I sometimes show in class.

I made an amateur video from this in-class presentation. It's a bit retro style ...

As you study for the terms, here is a good video in which I show the parts on the models:

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