Chapter 12: Muscle Physiology

These flashcards cover key terms and concepts related to muscle physiology, including different types of muscles, contraction mechanisms, and energy systems.

Efferent Nervous System

The branch of the nervous system that carries signals away from the central nervous system to effectors (muscles and organs).

Skeletal Muscle

Striated and voluntary muscle that attaches to bones and is primarily examined in this chapter.

Cardiac Muscle

Striated and involuntary muscle that makes up the heart wall.

Smooth Muscle

Non-striated and involuntary muscle located in internal organs and blood vessels.

Fascicles

Bundles of muscle fibers within skeletal muscle.

Fascia

A sheet of fibrous connective tissue that covers muscles.

Superficial Fascia (subcutaneous layer)

Immediately deep to the skin. Composed of areolar and adipose tissue. Stores water and fat, reduces heat loss, protects, assists nerves and blood vessels.

Deep fascia

Composed of irregular connective tissue. Separates muscles into functional groups/units.

Epimysium

Outer layer of connective tissue that surrounds the entire muscle.

Perimysium

Surrounds bundles of muscle fibers.

Fascicles

Bundles of muscle fibers

Endomysium

Inner layer. Surrounds and separates individual muscle fibers.

Sarcolemma

Plasma membrane around skeletal muscle

Sarcoplasm

The liquid component within a muscle fiber.

Myofibrils

Small thread-like structures within muscle fibers that are the contractile elements.

Sarcomere

Basic functional units of striated muscle fibers

Z-disc

Plates that separate one sarcomere from another

A-band

Dark area containing thick filaments and areas of thin filaments that overlap thick

I-band

Light region containing only thin filaments

H Zone

Located in center of each A-band. Contains only thick filaments.

M Line

Divides H Zone in half

Myosin

Myofibril contractile protein forming thick filaments

Actin

Myofibril contractile protein forming thin filaments

Myosin Tails

Point towards M Line in center of sarcomere

Myosin Heads (cross bridges)

Contain an actin binding site and ATPase site.

Myosin Binding Sites

On each actin molecule. Allow attachment of myosin cross bridges.

Tropomyosin

Regulatory protein in thin filaments, covers myosin binding sites on actin molecules whilst muscles are relaxed.

Troponin

Regulatory protein in thin filaments, holds tropomyosin in place in relaxed muscle tissue,

Sarcoplasmic Reticulum (S.R.)

Fluid-filled sacs that encircle myofibrils, storing calcium and releasing it during muscle contraction.

Transverse Tubules (T-Tubules)

Extensions of sarcolemma that protrude deep into the muscle. Allow impulses and nutrients to travel deep into muscle fibers.

Sliding Filament Mechanism

The process by which skeletal muscles shorten as thick and thin filaments slide past each other.

Calcium's Role in Contraction

Calcium ions increase in the sarcoplasm to trigger muscle contractions by changing the shape of troponin-tropomyosin complex.

ATP

Energy source for living cells. Attached to sites on myosin molecules within relaxed muscle.

Motor end plates

Portion of a muscle fiber that is directly across the synaptic cleft from the synaptic end bulbs. Contain acetylcholine receptors.

Acetylcholinesterase

Enzyme breaks down AcH in synaptic cleft

Power Stroke

The action of myosin heads pulling thin filaments towards the center of the sarcomere during muscle contraction.

Excitation-Contraction Coupling

The process by which an action potential triggers muscle cell contraction.

Isotonic Contraction

A muscle contraction in which the muscle changes length while the tension remains constant.

Concentric contraction

Shortening of muscle

Eccentric Contraction

Lengthening of muscle

Isometric Contraction

A muscle contraction where tension is produced without a change in muscle length.

Myogram

A record of muscle contraction that depicts different periods of muscle activity.

Twitch Contraction

A brief contraction of all muscle fibers in a motor unit in response to a single impulse.

Wave Summation

Occurs when 2 stimuli are applied, second is delayed until first refractory period has ended.

Tetanus

Sustained contraction in which the muscle can only partly relax between impulse stimulation.

Glycolysis

The metabolic pathway that breaks down glucose into pyruvic acid, providing ATP for muscle contraction.

Aerobic Cellular Respiration

The process of producing ATP with the presence of oxygen, yielding more energy and involving the Krebs Cycle.

Oxygen Debt

The extra oxygen consumed post-exercise to restore depleted oxygen supplies in the body.