1. NOTES: The Muscular System (Ch 8, part 1) Functions, Characteristics, Types of Muscle Tissue

2. **Muscles can be voluntary or involuntary**
Functions of Muscle:
Movement
Heat production (thermogenesis)- byproduct of cellular respiration
(converting glucose to ATP in the
mitochondria of cells)
Posture & body/joint support
**Muscles can be voluntary or involuntary**

3. 4 Characteristics of Muscle Tissue
Excitability (irritability): ability to respond to certain stimuli by producing electrical signals called action potentials
Stimuli= neurotransmitters or hormones
Click for animation

4. 4 Characteristics of Muscle Tissue
Contractility: ability to shorten & thicken
Extensibility: muscle can be stretched without damage to the tissue
Most muscle tissue is found in pairs: one contracts while the other is relaxed & stretching
Elasticity: muscle returns to its original shape after contraction & extension
Click for animation!

5. 3 Types of Muscle Tissue:
Smooth
Cardiac
Skeletal

6. 1. SMOOTH MUSCLE
• Walls of hollow internal organs (arteries, respiratory passages, digestive canals
-Involuntary muscle
• Smooth muscle fibers (cells) contain filaments of actin and myosin & 1 nucleus (no striations)
• Muscle fibers (cells) are separate
and organized in flattened sheets
Joined by electrical junctions

9.  Characteristics Unique to Smooth Muscle Contraction:
• Can maintain a contraction longer than skeletal muscle
• Can change length without changing tension (smooth muscle lining the stomach can stretch but still maintain pressure inside the stomach)

10. 2. CARDIAC MUSCLE • Found only in the heart
• Composed of striated cells joined end to end (only 1 nucleus)

11. • Cells are connected by INTERCALATED DISCS (which function in transmitting the impulse of contraction from cell to cell)
-Involuntary
-Cells don’t get “fatigued”

12. • The network of cardiac cells contracts as a unit (all-or-none response!)
• Cardiac muscle is SELF-EXCITING and AUTO-RHYTHMIC

14. 3. Skeletal Muscle
Attaches to skeleton & is responsible for voluntary body movements
Each muscle fiber (cell) is elongated and multinucleated; has distinct transverse striations
Muscle fibers are grouped in bundles (each bundle is a FASCICLE)

15. SKELETAL MUSCLE ACTIONS
*The type of movement a skeletal muscle produces depends on the way the muscle attaches on either side of a joint.
• Immovable end of a
skeletal muscle is called
the ORIGIN (may be
more than one)
• Movable end of a skeletal muscle is called the INSERTION

16. SKELETAL MUSCLE ACTIONS
*when a muscle contracts, its insertion is pulled towards its origin.

17. Interaction of Skeletal Muscles:
Skeletal muscles function
in groups
The muscle responsible
for most of a movement
is the: PRIME MOVER (or AGONIST)

18. Interaction of Skeletal Muscles:
Muscles that contract and assist the prime mover are: SYNERGISTS
Muscles that resist the action of the prime mover are: ANTAGONISTS

19. Muscles that function as joint stabilizers are called FIXATOR muscles
Maintain posture or balance
Most muscles function as one or more of these. A muscle that may be a prime mover during flexion may be an antagonist during extension.