Muscle attachments, movements and actions

Origin is the point of attachment that does not move, while the insertion is the point of attachment that moves.

When the insertion is pulled towards the origin, the muscle shortens.

Action is the act of shortening the muscles.

An action name has two parts:
a. Action - for example, flexion, extension, etc.
b. Joint - for example, elbow, knees, etc.

Rules to Determine Actions in the Muscles.

a. Muscle will move the joint it crosses
b. Muscles pull towards the origin, not push.
c. Direction of the joint = direction of movement. For example, the movement of anterior elbow will cause flexion while the movement of the hip will result in lateral hip movements such as abduction.
d. If movement is at an angle, will result in a multiplanar movement.

Ask yourself these questions:

a. Where is the origin?
b. How about the insertion?
c. Imagine the two ends.
d. What kind of movement will happen between those two ends?

In application, you can remember this by thinking of crunches.


Wait, not that kind of crunch (the chocolate bar).... the kind that we all just love to do on our spare time:



sixpackabsguide.com

The origin of the rectus abdominis also known as the abs is the medial pubis.  The insertion is in the medial ribs and the xiphoid process. Think, what joint will move when flexion happens in this region?

Action, therefore, will be called lumbar intervertebral flexion.


Naming skeletal muscles can vary depending on

a. Appearance
b. Location
c. Function
d. Origin and insertion
e. Relative size
f. Number of origins
g. Fiber orientation


Starting with...

Appearance.

a. Serrate - A good  way I remember this is by the serratus anterior. To me, it looks sort of like chicken feathers.... or the serrated ends of a leaf?
b. Semi - partly
c. Detloid - triangular in shape
d. Rhomboid - rhombus in shape. Well, if you ask me, I think the rhomboid major and minor doesn't really look rhomboid in shape...
e. Trapezius

Size.

a. Maximus - the LARGEST
b. Medius - medium
c. Minimus - smallest
d. Major - larger
e. Minor - smaller
f. Longus - LONGER
g. Brevis - shorter

Position.

a. lateral/medial
b. posterior/anterior
c. inferior/superior
d. external/internal

Fiber Orientation.

a. rectus - straight
b. oblique - angled (remember the horse's obliques?)
c. transversus - horizontal
d. orbicularis - round/circular

Numbers - Bi/tri/quadri

Actions - Extensor, flexor, adductor, pronator, levator (elevation), depressor, erector (holds  up)

Drawing Info from Names.

Triceps brachii

Tri - three, ceps - heads, brachii - upper arm

Some joint options you have to remember include:

a. Temporomandibular joint
b. Atlanto-occipital joint
c. Cervical intervertebral joint
d. Thoracic intervertebral joint
e. LUmbar intervertebral joint
f. Vertebrocostal and Sternocostal joint

How I remember this is by the word TACTLUVS. I love it when people are tactful, hence, TACTLUVS. I know, corny, but it works! At least for me.

Some actions of the Skeletal Muscles include:

a. Agonist - or the prime mover, or the muscle that initiates the movement.
b. Antagonist - or the villain! It works against the agonist.
c. Synergist - assists the agonist. In a movie, this is usually the funny best friend.

    Neutralizer - neutralizes the muscle by removing excess actions (kind of like a buffer in Chemistry!)

    Fixator - fixes the origin by stabilization

Here are some exercise related information to remember:

a. Muscle atrophy - is the decrease of size of muscle as a result of lack of exercise. This causes the myofibrils to disassemble.

b. Muscle hypertrophy - the increase of size of muscle as a result of exercise. The cells do not increase, but the amount of protein, mitochondria, ATP, myofibrils and myofilaments increase. This is a non - pathogenic increase.

c. Muscle dystrophy - a pathogenic, diseased skeletal muscle caused by degeneration. A good example would be a disease called the Duchenne muscular dystrophy. This is a sex linked disease from the recessive allele, most commonly seen in males. This gene codes for dystrophin.

d. Strains - stretch/tear 

e. Charley Horse - pain and stiffness at a local area after a contusion.

Quick Factoid:  In adult skeletal muscle tissue, there are embryonic like cells that are called satellite cells.

STUDY BREAK

No wonder why people say, "I love you will all my butt". It's because it's the largest muscle there is!

Have a great day,

M



Kinds of muscle tissues

Some features of the muscle tissues include

1. Excitability - is the ability for muscle tissues to transmit electrical changes in muscles fibers to allow contraction.

2. Contractility - is the ability for the muscle fibers to shorten to allow contraction

3. Elasticity - is the ability of the muscle fibers to go back to its original length once released from the muscle contraction

4. Extensibility - is the ability for the muscle fiber to stretch

I like to remember this as E3C. E cubed C. Easy, EC... get it? Ha - ha, very funny.

There are three kinds of muscle tissues.

a. Skeletal
b. Cardiac
c. Smooth

Let's start with Skeletal muscle tissue...

Skeletal.

This is my illustration.

But this is what it looks like in real life....

biologyonlineus.com



stevegalik.org



Features of Skeletal Muscle tissue include rod, long shaped muscle fibers, striations (stripes), many nuclei, voluntary control and no mitosis in adults. 

Some functions are for movements, posture to help resist  gravity, to regulate our temperature, to store materials and for support, lining muscles in skeleton.

Cardiac.

Getting tired of my sucky illustrations yet?  The highlights are the parts you have to know!





But they look this this in real life...





medicalpicturesinfo.com



They are only seen in the walls of the heart, they are striated like the skeletal muscles, but they only have one or two nuclei per cell. They are branched in shape, have intercalated disks and are involuntary. No mitosis allowed in adult cardiac muscles. What sets them apart is the absence of perimysium and epimysium.

It's main function is to help the transportation of blood throughout the entire body.

Smooth Muscle tissue.

This is what they look like in real life...



siumed.edu

The Smooth muscle tissues are typically seen in visceral organs such as the stomach and the lining of blood vessels. They have no striations, that is probably why they are called "smooth" muscle tissue. They have fusiformed shape cells that has a single nuclei inside. What they are needed to function is to help transport materials, for example, food into the tubes of the intestine. They are also involuntary. What sets them apart besides the lack of striations is their ability to divide through mitosis in adults. A good way to remember is to think of your digestive track. If you look at a colonoscopy picture, the lining looks very smooth.



avrupatimes.com

Also think of how you cannot voluntarily control its contractions, how acidic the stomach is inside  and thus, the high rate of mitosis to replace the cells rapidly.

Now, I don't know about you, but I find the whole skeletal muscle organization kind of confusing. Bundles after bundles after bundles after bundles... it does not end, so I just list it down to keep it simple.

Here is a picture of a neuromuscular junction/skeletal muscle fiber.

Quick factoid: Skeletal muscle fibers get new nuclei by the fusion of embryonic myoblasts.


From superficial to deep:

a. Tendon - Attached muscle to a bone

b. EPIMYSIUM - Dense Irregular Connective tissue

c. Muscle - an organ

d. PERIMYSIUM - Dense Irregular Connective tissue

e. Fascicle - Bundles of muscle fibers

f. ENDOMYSIUM - Areolar Connective tissue

g. Myofibers - wrapped by Sarcolemma (cell membrane) with sarcoplasm (similar to a cytoplasm).  Muscle fibers are individual skeletal muscle cells.

h. Myofibril - proteins rods that grabs, pulls and releases. Has the ability to shorten in the contraction of muscles.

i. Myofilament - protein units

j. Myosin and Actin - principle proteins of muscle contraction.

The Actin filaments are thin filaments. I remember this because they kind of rhyme. Actin for thin. They are made up of tropomyosin and troponin. Tropomyosin covers the binding sites while Troponin binds to calcium to allow contraction.

The Myosin filaments are thick filaments. A good way to remember is to think of the SIN gluttony (from myoSIN). When we indulge in gluttony, we become thick in stature. Sounds silly, but it works for me!  These thick filaments consists of a tail and a head that is essential for the formation of crossbridges during muscle contraction.



partyofsin.com

The Titin are for extensibility, elasticity and for attachment to Z discs.

Sarcomere.

A sarcomere is a functional contractile unit in a skeletal muscle fiber.

This is what they look like in an artificial sarcomere model:



http://www.onlinesciencemall.com

The blue lines are the myosin (thick), and the red lines are the actin (thin).

Have a great day,

M