1. Introduction to the Muscular System
October 18, 2017

2. Muscle Functions
What are the functions of muscles?

3. Muscle Functions Producing movement Muscle contraction allows movement
Of the body
For facial expression
To move fluids, digesting food, and other substances through the body
Maintain blood pressure

4. Muscle Functions Maintaining posture
Muscles are constantly varying their
contraction to maintain posture while we
are seated or standing.
Stabilizing joints
Muscle contraction helps
keep joints in
position
If muscles are too weak, joints fall out of place, leading to damage.

5. Muscle Functions Generating heat
Muscle contraction requires an enormous amount of energy.
When food is converted to ATP to power the muscles, nearly 75% of the energy is lost to heat.
Remember: shivering functions to raise body temperatures by contracting muscles
If muscles are too weak, joints fall out of place, leading to damage.

6. Gross Anatomy of Muscle Tissue
Notice the prefixes! -mys, -myo, and -sarco

7. Gross Anatomy of Muscle Tissue
A single muscle cell is called a muscle fiber.
Muscle fibers are LONG (up to 1 ft).
Each muscle
fiber is
wrapped in a
delicate
connective
tissue called
endomysium
Remember:
Endo = inside

8. Gross Anatomy of Muscle Tissue
Multiple fibers (cells!) are grouped together to form a fascicle.
Each fascicle is wrapped up with a connective tissue called
perimyscium.
Remember:
peri = around

9. Gross Anatomy of Muscle Tissue
Blood vessels branch out between the fascicles.
The whole muscle is covered by a thick, tough layer of connective tissue called epimysium.
Epi = outer

10. Gross Anatomy of Muscle Tissue
The epimysia fuse to
The periosteum (outer connective tissue) of bone
- or -
The perichondrium (outer connective tissue)of cartilage
Tendons (rope like connective tissue that connects muscle to bone)
Aponeuroses (sheetlike connective tissue that attaches muscle to bones, cartilage, or other muscles)

11. Gross Anatomy of Muscle Tissue

12. Gross Anatomy of Muscle Tissue

13. Gross Anatomy of Muscle Tissue
This is a micrograph of muscle tissue, magnified ~70 X
Identify:
Nuclei,
Muscle fibers,
Endomysium
Perimysium
Blood vessels

14. Gross Anatomy of Muscle Tissue
This is a micrograph of muscle tissue, magnified ~70 X
Identify:
Nuclei,
Muscle fibers,
Endomysium
Perimysium
Blood vessels

15. Comparison of Skeletal, Smooth, and Cardiac Muscle
What do you already know about the three types of muscles?

16. Comparison of Skeletal, Smooth, and Cardiac Muscle
Attached to bones (or, in the face, to skin)
Walls of heart
Walls of hollow organs, airways, and arteries

17. Comparison of Skeletal, Smooth, and Cardiac Muscle
Regulation of contraction
Nervous system excites contraction.
No effect of hormones
Nervous system excites or inhibits contraction.
Hormones and other chemicals (e.g. CO2, pH, low O2, ) may stimulate or inhibit contraction.
Intrinsic regulation from a pacemaker within the heart.
Natural rhythm can be excited or inhibited by the nervous system OR by body hormones
Speed of contraction
Slow to fast
Very slow
slow
Rhythmic contraction No
Yes, can be triggered by stretch receptors
Yes, has internal pacemaker
Muscle contraction is stimulated by nervous system.
Hormones have no effect
Contraction can be stimulated (excited) OR reduced (inhibited) by EITHER the nervous system OR hormones OR body chemicals (e.g. pH)
Smooth muscle can retain tone without nervous stimulation.

18. Turn & Talk
Relate at least 3 differences between skeletal, cardiac, and smooth muscle to differences in their function.
Smooth muscle can retain tone without nervous stimulation.

19. Quick Review
The connective tissue covering that encloses the sarcolemma of an individual muscle fiber is called the
Epimysium
Perimysium
Endomysium
periosteum

20. Quick Review 2) A fascicle is A muscle A bundle of muscle fibers
A bundle of myofibrils
A group of myofilaments

21. Quick Review 3) Muscle tissue that is involuntary cardiac muscle only
Smooth muscle only
Skeletal muscle only
Cardiac and smooth muscle
Cardiac and skeletal muscle

22. Quick Review
4) The muscle tissue that consists of single, very long, cylindrical, multinucleate cells with very obvious striations is:
cardiac muscle only
Smooth muscle only
Skeletal muscle only
Cardiac and smooth muscle
Cardiac and skeletal muscle

23. Quick Review
5) Which of the following is NOT a function of the muscular system
Producing movement
Maintaining posture
Stabilizing joints
Generating heat
hematopoiesis