Lecture 9 Muscle organization

Question 1

Describe the different ways fascicles are organized in skeletal muscles.

Answer 1

Parallel - fascicles run parallel to each other along a long axis. Ex: rectus abdominis

Convergent - fascicles come from a broad origin and converge towards the insertion point. Ex: pectoralis major

Circular - fascicles form concentric rings. Ex: orbicularis oris

Pennate - “feather like” arrangement where short fibers are obliquely attached to tendon. Unipennate, bipennate, and multipennate forms
**Muscles with pennate arrangement don’t move a lot (or as much as the other arrangements) but are much more powerful

Question 2

What is the function of agonist (prime movers)

Answer 2

a given muscle that is the prime mover for a joint. Example: biceps brachii

Question 3

What is the function of antagonosts

Answer 3

a muscle that works against the agonist muscle. Example: triceps brachii

Question 4

What is the function of synergists

Answer 4

a muscle that works with the agonist. Example: brachialis

Question 5

What is the function of fixators

Answer 5

a muscle that stabilizes the agonist. Example: deltoid

Question 6

Explain how muscle names incorporate action

Answer 6

supinator - supinates the forearm

Question 7

Explain how muscle names incorporate body region

Answer 7

rectus femoris - located on the femur

Question 8

Explain how muscle names incorporate attachements

Answer 8

sternocleidomastoid - attached to the sternum (“sterno”), the clavicle (“cleido”), and the mastoid process (“mastoid”)

Question 9

Explain how muscle names incorporate orientation

Answer 9

external abdominal oblique - outer / abdomen / side

Question 10

Explain how muscle names incorporate shape/size

Answer 10

gluteus maximus. “Maximus” = HUGE

Question 11

Explain how muscle names incorporate number of heads

Answer 11

triceps brachii. TRI - three CEPS - head

Question 12

Discuss the causes and dysfunction of muscular dystrophy.

Answer 12

•dystrophy means abnormal structure
•an inherited disease
•disorder that affects groups of muscles
•skeletal muscle degenerates
•muscle replaced by adipose and fibrous connective tissue
•common and serious form is Duchenne muscular dystrophy
-x-linked recessive gene
-1/3500 births, mostly males
-lack the protein called dystrophin