Principles of Human Physiology - Muscle Physiology

These flashcards cover key terminology and concepts related to muscle physiology, including skeletal, smooth, and cardiac muscles, their characteristics, and regulation.

Skeletal Muscle Fibers

The three types include slow oxidative, fast oxidative, and fast glycolytic, each with distinct characteristics related to fatigue resistance and contraction speed.

Extrafusal Fibers

Contractile cells that make up skeletal muscle, innervated by alpha (α) motor neurons.

Intrafusal Fibers

Contractile cells of the muscle spindle that adjust the sensitivity of the muscle to stretch, innervated by gamma (γ) motor neurons.

Golgi Tendon Organs (GTOs)

Sensory receptors located in tendons which detect tension and inhibit muscle contraction during excessive stretching.

Smooth Muscle

Muscle tissue found in internal organs and blood vessels, characterized by involuntary action, spindle shape, and non-striated appearance.

Calmodulin

A regulatory protein in smooth muscle that binds calcium and activates myosin light-chain kinase.

Single-Unit Smooth Muscle

Type of smooth muscle where fibers contract as a single unit, commonly found in the intestines and blood vessels.

Multi-Unit Smooth Muscle

Type of smooth muscle where fibers are individually innervated, allowing for fine control, located in large airways and arteries.

Cardiac Muscle

Striated muscle similar to skeletal muscle but under involuntary control, featuring intercalated disks and pacemaker cells.

Excitation-Contraction Coupling

The process in muscle cells where an action potential leads to an increase in intracellular calcium, resulting in contraction.

Myosin Light-Chain Kinase (MLCK)

An enzyme activated by calcium-bound calmodulin that initiates contraction in smooth muscle by phosphorylating myosin.

Autonomic Nervous System Control

Regulation of smooth and cardiac muscle activity that is involuntary and modulated by neurotransmitters and hormones.

Pacemaker Cells

Specialized cells in cardiac muscle that generate spontaneous action potentials, controlling the rhythm of the heart.

Recruitment in Muscle

The process where additional motor units are activated to increase muscle force during contraction.

Striations in Muscle

The alternating dark and light bands seen in skeletal and cardiac muscle, associated with the arrangement of sarcomeres.

Tension in Smooth Muscle

Smooth muscle can maintain tone and tension without continuous stimulation, linked to its ability to stretch.

Crossbridge Cycling

The process of muscle contraction where myosin heads bind to actin in the presence of ATP and calcium, leading to muscle shortening.