Chapter 10 Study Guides (Gemini)

Skeletal Muscle

Body movement, maintenance of posture, protection/support, regulating elimination (sphincters), and heat production.

Characteristics

Excitability, conductivity, contractility, extensibility, and elasticity.

Epimysium

Dense irregular connective tissue wrapping the whole muscle.

Perimysium

Dense irregular connective tissue wrapping a fascicle (bundle of fibers).

Endomysium

Areolar connective tissue wrapping an individual muscle fiber (cell).

Sarcolemma

The plasma membrane of a skeletal muscle fiber.

Sarcoplasmic Reticulum (SR)

Internal membrane complex that acts as a reservoir and storage for Calcium ions (Ca2+).

Triad

A T-tubule in the middle of two terminal cisternae (storage sacs) of the SR.

Sarcomere

The functional unit of a myofibril, marked at both ends by Z-discs.

I-Band

Light-appearing region containing only thin filaments; bisected by the Z-disc.

A-Band

Dark-appearing region containing the entire length of thick filaments.

H-Zone

The central portion of the A-band; contains only thick filaments (no overlap).

M-Line

The protein meshwork in the center of the H-zone; attachment site for thick filaments.

Z-Disk

Specialized proteins that anchor thin filaments and mark the ends of a sarcomere.

Motor Unit

A single motor neuron and all the muscle fibers it controls.

Synaptic Knob

The expanded tip of the axon that releases Acetylcholine (ACh) into the synaptic cleft.

Excitation-Contraction Coupling

An electrical signal (action potential) triggers the release of Ca2+ from the SR.

Crossbridge Formation

Step 1: Myosin head attaches to the exposed binding site on actin.

Powerstroke

Second step; myosin pulls the thin filament toward the center; ADP and Pi are released.

Release of Myosin

Third step; a new ATP binds to the myosin head, causing it to let go of the actin.

Reset Myosin Head

Step 4: ATP is split into ADP and Pi to "cock" the myosin head back like a spring.

Relaxation

Nerve signals stop, ACh is broken down, and Ca2+ is pumped back into storage.

Creatine Phosphate

Immediate ATP source; provides 10-15 seconds of energy by giving a phosphate to ADP.

Glycolysis

Anaerobic ATP source; converts glucose to pyruvate in the cytosol; 2 ATP per glucose.

Aerobic Cellular Respiration

Long-term ATP source; occurs in mitochondria; requires oxygen; produces ~30 ATP.

Oxidative Fibers

Fatigue-resistant "red" fibers; use aerobic respiration; many mitochondria and myoglobin.

Glycolytic Fibers

Fatigable "white" fibers; use anaerobic respiration; large glycogen reserves; powerful.

Isometric Contraction

Muscle contracts but length stays the same.

Isotonic Contraction

Tension remains the same while muscle length changes.

Concentric Contraction

Isotonic sub-type; the muscle shortens as it contracts.

Eccentric Contraction

The muscle lengthens as it contracts.

Cardiac Muscle

Found in the heart; striated (has sarcomeres), involuntary, and has intercalated discs.

Acetylcholinesterase (AChE)

The enzyme in the synaptic cleft that breaks down ACh to stop the muscle contraction.

Oxygen Debt

The extra oxygen needed after exercise to replace ATP, creatine phosphate, and glycogen.