1. Responsible for movement Main function is contraction and shortening
Muscular System
Responsible for movement
Main function is contraction and shortening

2. Muscle System A. General Information 1. 3 muscle types
a. Skeletal
b. Cardiac
c. Smooth
2. Differ based on cell structure, body location, and how they are stimulated to contract

3. Muscle System – General Function
B. General Function
3. Contract due to electrochemical impulses
4. 3 general functions (we will cover each of these individually)
a. Motion
b. Heat production
c. Posture and body support

4. Muscle System – General Function
B. General Function (cont)
4. (cont)
a. Motion
i. General movement of the body
Examples: walking, running, writing, swimming, etc.
ii. Breathing and moving of body parts, without actually moving, are caused by skeletal muscle
iii. Blood flow and food flow through the associated systems is caused by smooth muscle

5. Muscle System – General Function
B. General Function (cont)
4. (cont)
b. Heat production
i. Muscle metabolism helps to support the internal temperature
ii. Muscles make up 40% of the body weight and are continuously active creating heat
iii. Shivering is a response to the body needing to warm up

6. Muscle System – General Function
B. General Function (cont)
4. (cont)
c. Posture and body support
i. Skeletal muscle gives form and support
ii. Some muscles work in opposition to gravity
iii. Oppositional muscles (to gravity) work without our control, that is why we get the head nodding when I am particularly boring!

7. Muscle System – General Function
C. Basic Characteristic Properties
1. Irritability
Receives and responds to nerve stimulus
2. Contractility
Responds to stimulus by contration
3. Extensibility
Opposing muscles will stretch or lengthen muscle fibers after the stimulus stops
4. Elasticity
Tends to return to original length

8. Muscle System – General Function
D. Basic Characteristic of Smooth and Skeletal Muscles
1. Skeletal and smooth muscles are elongated
Called muscle fibers
2. Contraction is dependant on the type of myofilament
Myo- and mys- and sarco- prefixes mean the term is dealing with muscles

9. Muscle System - Skeletal
E. Skeletal Muscle Characteristics
1. The muscles are usually:
a. long and narrow
b. span a joint
c. are attached by tendons to bones
2. The origin of a muscle is the more fixed or stationary attachment
a. Generally the proximal attachment
3. The insertion is the more movable end
a. Generally the distal attachment

10. Skeletal Muscle Fibers

11. Muscle System - Skeletal
E. Skeletal Muscle Characteristics
4. The belly or gaster is the fleshy or thickened portion
a. Usually on the bone proximal to the bone being moved
5. The tendon spans the joint between the bones
6. Tendons in the wrist and ankle are protected by a tendon sheath
a. Lubricate the tendons with synovial fluid, although the tendon is covered by a retinaculum

12. Muscle System - Skeletal
E. Skeletal Muscle Characteristics
7. Made up of skeletal muscle fibers
8. Attach to the skeleton
9. Are cigar shaped
10. Multinucleated cells
11. Largest muscle fibers
a. Some up to 30cm long (almost a foot!)
12. Striated muscle
13. Voluntary muscle (can control)
a. Mostly reflexive

13. Muscle System - Skeletal
E. Skeletal Muscle Characteristics
14. Contracts with great force
15. Become tired easily and must rest
16. Muscles that contract together are called synergistic
a. Muscles of the upper arm (biceps and brachialis) contract to flex the elbow
17. Muscles that contract opposite to each other are called antagonistic
a. The triceps muscle contracts to extend the elbow

14. Muscle System - Skeletal
E. Skeletal Muscle Characteristics
18. Architecture (just a few) of the Origin or Insertion (a.k.a. Tendon Shapes)
a. Parallel or fusiform
i. Have Fibers that run parallel to each other
ii. Are sometimes called Strap Muscles
iii. These are long muscles
iv. Have good endurance, but are not strong
ex. Sartorius and Sternocleidomastoid muscles

15. Muscle System - Skeletal
E. Skeletal Muscle Characteristics (cont)
18. Architecture (just a few) of the Origin or Insertion (a.k.a. Tendon Shapes) [cont]
b. Convergent
i. The origin is wider than the point of insertion
ii. Fibers converge at the insertion point to maximize contraction
iii. Sometimes called Triangular Muscles
ex. Pectoralis Major

16. Muscle System - Skeletal
E. Skeletal Muscle Characteristics (cont)
18. Architecture (just a few) of the Origin or Insertion (a.k.a. Tendon Shapes) [cont]
c. Pennate
i. Many fibers per unit area, are strong, provide dexterity and tire quickly
3types (we will go into more detail for each)
(indent) Unipennate
(indent) Bipennate
(undent) Multipennate

17. Muscle System - Skeletal
c. Pennate (cont)
3 types (cont)
Unipennate (cont)
Muscle fibers are arranged in a diagonal direction into the tendon
Allows for great strength
Examples: Lunbricals, Externsor Digitorum Longus
Bipennate (cont)
Muscle fibers are concentrated into two rows
Facing in opposite diagonal directions into the central tendon (looks like a feather)
Example: Rectus Femoris

18. Muscle System - Skeletal
c. Pennate (cont)
3 types (cont)
Multipennate
Multiple rows of diagonal fibers with a branching central tendon (two or more)
Example: Deltoid (three sections, [anterior/posterior/middle])

19. Muscle System - Skeletal
E. Skeletal Muscle Characteristics (cont)
18. Architecture (just a few) of the Origin or Insertion (a.k.a. Tendon Shapes) [cont]
d. Circular
i. Appear circular in shape
ii. Surround a body opening
act as a sphincter

20. Tendon/Muscle Shapes

21. Parallel Muscles

22. Parallel and Pennate

23. Circular Muscles

24. Muscle System – Skeletal Fibers
F. Skeletal Muscle Fibers
1. Anatomy of a skeletal muscle fiber
a. Fibers are bundled together by connective tissue
b. Each single fiber is bundled by a connective tissue sheath called endomysium
i. The endomysium package is called a bundle

25. Muscle System – Skeletal Fibers
F. Skeletal Muscle Fibers
1. Anatomy of a skeletal muscle fiber (cont.)
c. Several muscle bundles are wrapped by a coarse fibrous membrane called perimysium
d. The wrapped fiber bundles are called a fasicle
e. Many fasicles are bundled together in a tissue called epimysium
f. Epimysia are blended together to form tendons or aponeuroses (which attach muscles indirectly to bones)

26. Skeletal Muscle Epimysium

27. Muscle System - Smooth G. Smooth Muscle Characteristics
1. No striations
2. Involuntary movement (can’t control)
3. Found in the walls of hollow organs
a. Examples: stomach, urinary bladder, bronchial tubes, etc.
4. Overall description:
a. Visceral
b. Nonstriated
c. Involuntary

28. Muscle System - Smooth G. Smooth Muscle Characteristics
5. Cells are spindle shaped
6. Have a single nucleus
7. Arranged in sheets or layers
8. Usually one layer is circular, the other is arranged longitudinally
9. They contract opposite or antagonistically, changing the shape of the organ

29. Smooth Muscle Fibers

30. Muscle System - Cardiac
H. Cardiac Muscle Characteristics
1. Found only in the heart
2. It is striated and involuntary
3. Cushioned by small amounts of connective tissue
4. Arranged in spiral shapes
5. Connected by intercalated discs, sends chemicals to allow for controlled contractions
6. Usually contracts at a steady rate

31. Cardiac Muscle Fibers