Chapter 39 – Motor Mechanisms and Behavior

Vocabulary flashcards covering key terms from Chapter 39: Motor Mechanisms and Behavior.

behavior

Internally coordinated responses (actions or inactions) of whole organisms to internal and/or external stimuli, excluding developmental changes.

thin filament

Two strands of actin and two strands of regulatory protein (tropomyosin) coiled together; a component of myofibrils in muscle fibers.

thick filament

A filament composed of staggered arrays of myosin molecules; a component of myofibrils in muscle fibers.

myofibril

A longitudinal bundle in a muscle fiber containing thin filaments of actin and regulatory proteins and thick filaments of myosin.

sarcomeres

The fundamental repeating units of striated muscle, delimited by Z lines.

sliding-filament model

Explains muscle contraction as the movement of thin (actin) filaments along thick (myosin) filaments, shortening the sarcomere.

tropomyosin

Regulatory protein that blocks myosin-binding sites on actin molecules.

troponin complex

Regulatory proteins that control the position of tropomyosin on the thin filament.

transverse (T) tubules

Infoldings of the plasma membrane of skeletal muscle cells.

sarcoplasmic reticulum (SR)

Specialized endoplasmic reticulum that regulates cytosolic calcium concentration in muscle cells.

motor unit

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

tetanus (muscle)

Maximal, sustained contraction of a skeletal muscle caused by very high-frequency stimulation.

myoglobin

Oxygen-storing, pigmented protein in muscle cells.

fast-twitch fiber

Muscle fiber specialized for rapid, powerful contractions.

slow-twitch fiber

Muscle fiber capable of sustaining long contractions.

cardiac muscle

Striated muscle forming the heart’s contractile wall; cells are joined by intercalated disks that relay electrical signals.

smooth muscle

Muscle lacking striations due to uniform myosin distribution; responsible for involuntary body activities.

hydrostatic skeleton

Skeleton consisting of fluid held under pressure in a closed body compartment; main skeleton of many soft-bodied invertebrates.

peristalsis

Alternating waves of contraction and relaxation in smooth muscles that move contents or propel an animal forward.

exoskeleton

Hard external encasement, such as a mollusk shell or arthropod cuticle, providing protection and muscle attachment.

chitin

Structural polysaccharide forming fungal cell walls and arthropod exoskeletons.

endoskeleton

Hard skeleton located within an animal’s soft tissues.

locomotion

Active motion from place to place.

behavioral ecology

Study of the evolution of and ecological basis for animal behavior.

fixed action pattern

Sequence of unlearned acts that is essentially unchangeable and usually completed once initiated.

sign stimulus

External sensory cue that triggers a fixed action pattern.

migration

Regular, long-distance change in location.

signal (behavior)

Transmission of a stimulus from one animal to another.

communication

Process involving transmission, reception, and response to signals between animals.

pheromones

Small molecules released into the environment for intraspecific communication; influence physiology and behavior.