NOTES: The Muscular System (Ch 8, part 2)

NOTES: The Muscular System (Ch 8, part 1) Functions, Characteristics, Types of Muscle Tissue Functions of Muscle: 1. Movement 2. Heat production (thermogenesis)- byproduct

of cellular respiration (converting glucose to ATP in the mitochondria of cells) 3. Posture & body/joint support **Muscles can be voluntary or involuntary**

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 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! 3 Types of Muscle Tissue: 1. Smooth

2. Cardiac 3. Skeletal 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

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) 2. CARDIAC MUSCLE Found only in the heart Composed of striated cells joined end to

end (only 1 nucleus) Cells are connected by INTERCALATED DISCS (which function in transmitting the impulse of contraction from cell to cell) -Involuntary -Cells dont get fatigued

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

SKELETAL MUSCLE ACTIONS *when a muscle contracts, its insertion is pulled towards its origin. Interaction of Skeletal Muscles: Skeletal muscles function in groups

The muscle responsible for most of a movement is the: PRIME MOVER (or AGONIST) 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 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.