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