Quiz 4 - Muscle cells, types

Skeletal Muscle

Striated, voluntary muscle that attaches to bones and produces body movement. Multinucleated

Cardiac Muscle

Striated, involuntary muscle found in the heart; cells branch and connect with intercalated discs.

Smooth Muscle

Non-striated, involuntary muscle found in walls of organs and blood vessels.

Movement (muscle function)

Skeletal muscle contraction moves bones and body contents.

Stability

Muscles hold bones in place and resist gravity.

Sphincter Control

A ring-shaped muscle that contracts and relaxes to close or open body passages, acting as a valve to regulate the flow of substances. Muscles regulate openings such as eyelids, urethra, and anus.

Thermogenesis

Heat production by skeletal muscle.

Glycemic Control

Skeletal muscles absorb and use large amounts of glucose.

Epimysium

Connective tissue surrounding the entire muscle.

Perimysium

Connective tissue that surrounds bundles of muscle fibers (fascicles).

Endomysium

Thin connective tissue surrounding each individual muscle fiber.

Fascicle

Bundle of muscle fibers wrapped by perimysium.

Muscle Fiber

A single skeletal muscle cell.

Sarcolemma

Plasma membrane of a muscle fiber.

Nuclei (skeletal muscle)

Multiple nuclei located at the edge of muscle fibers.

Sarcoplasm

Cytoplasm of a muscle fiber.

Myofibril

Long protein bundles inside muscle fibers responsible for contraction.

Myofilaments

Protein filaments inside myofibrils responsible for muscle contraction.

Thick Filament

Myosin protein filament that pulls actin during contraction

Thin Filament

Actin filament that interacts with myosin during contraction.

Myosin

Thick filament protein with heads that form cross bridges with actin.

Actin

Thin filament protein that provides binding sites for myosin.

Tropomyosin

Protein that blocks myosin binding sites on actin when muscle is relaxed.

Troponin

Protein that binds calcium and moves tropomyosin to allow contraction.

Titin

Elastic protein that stabilizes thick filaments and prevents overstretching.

Sarcomere

Functional contractile unit of muscle fiber (Z disc to Z disc).

Z Disc

Boundary of a sarcomere; anchors thin filaments. On each sides

A Band

Dark region where thick and thin filaments overlap.

I Band

Light region containing only thin filaments.

H Zone

Region containing only thick filaments.

M Line

Center of sarcomere where thick filaments are anchored.

Direct (Fleshy) Attachment

Muscle connects directly to bone via epimysium fibers.

Indirect Attachment

Muscle connects to bone through a tendon.

Aponeurosis

Broad sheetlike tendon connecting muscle to bone.

Infraspinatus

Example of muscle with direct attachment.

Gastrocnemius

Calf muscle attached indirectly via the calcaneal tendon.

Rectus Sheath

Aponeurotic sheath surrounding rectus abdominis.

Neuromuscular Junction

Synapse between motor neuron and muscle fiber.

Motor Nerve Fiber

Neuron that stimulates muscle contraction.

Presynaptic Terminal / Axon Terminal

End of neuron that releases neurotransmitter.

Synaptic Vesicles

Vesicles containing acetylcholine.

Synaptic Cleft

Gap between neuron and muscle fiber.

motor end plate

Region of sarcolemma containing ACh receptors.

Acetylcholine (ACh)

Neurotransmitter that stimulates muscle contraction.

Slow Oxidative Fibers (Type I)

Red, fatigue-resistant fibers using aerobic respiration.

Fast Glycolytic Fibers (Type II)

White fibers that contract quickly but fatigue rapidly.

Cardiomyocytes

Cardiac muscle cells.

Intercalated Discs

Specialized junctions connecting cardiac cells.

Gap Junctions

Channels allowing electrical signals to pass between cardiac cells.

Sinoatrial Node

Natural pacemaker that sets heart rhythm.

Multiunit Smooth Muscle

Smooth muscle where fibers contract independently.

Unitary Smooth Muscle

Smooth muscle where many cells contract together.

Cross Bridge

Connection formed when myosin head binds actin.

Power Stroke

Myosin head pulls actin toward center of sarcomere.

Sliding Filament Theory

Actin slides over myosin causing sarcomere shortening.

Excitation

Nerve signal releases ACh and stimulates muscle fiber.

Excitation-Contraction Coupling

Electrical signal triggers calcium release.

Contraction

Myosin cross bridges pull actin and shorten sarcomere.

Relaxation

Calcium removed and muscle returns to resting state.