Thursday; Ch 10: Muscle Tissue & Physiology

What are the three muscle tissue types?

Skeletal (connected to skeleton; voluntary, striated), Cardiac (heart; involuntary, striated, intercalated discs), Smooth (mostly located in hollow organs; involuntary, non-striated)

List five properties of muscle cells.

Excitability, Contractility, Conductivity, Distensibility, Elasticity

Define sarcoplasm and sarcolemma.

Sarcoplasm = cytoplasm of muscle cell; Sarcolemma = plasma membrane

What are myofibrils?

Protein bundles responsible for contraction

What is the sarcoplasmic reticulum (SR)?

Stores and releases calcium ions

What are T-tubules?

Inward extensions of the sarcolemma that conduct impulses

What is a triad?

T-tubule plus two terminal cisternae of the SR

What are the three types of myofilaments?

Thick (myosin), Thin (actin, troponin, tropomyosin), Elastic (titin)

What is the function of titin?

Provides elasticity and stabilizes thick filaments

What structures make up a sarcomere?

Z-discs, I band, A band, H zone, M line

Which bands change during contraction?

I band and H zone shorten; A band stays the same

Explain the sliding filament theory.

Myosin heads pull actin toward the M line, shortening the sarcomere; filaments do not shorten.

What is resting membrane potential in muscle?

About –90 mV (negative inside due to Na⁺/K⁺ gradients)

What maintains RMP?

Sodium-potassium pump (3 Na⁺ out, 2 K⁺ in)

What types of channels help ion movement?

Leak channels (always open), gated channels (open with signals)

What are the two phases of an action potential?

Depolarization (Na⁺ in) and Repolarization (K⁺ out)