Glossary of Anatomy Chapter 9A: Muscles

Start Studying! Add Cards ↓

Muscle Fibres
Elongated multinucleate cell with a striated appearance.
Plasma membrane of a muscle fibre.
Cytoplasm of a muscle fibre.
Skeletal Muscle Tissue
Striated muscle responsible for voluntary motion.
Cardiac Muscle Tissue
Striated muscle of the heart responsible for non-voluntary contractions at a relatively steady rate.
Smooth Muscle Tissue
Nonstriated muscle of the visceral organs responsible for nonvoluntary conduction of fluids and other substances through internal body channels.
Excitability / Irritability
The ability to receive and respond to a stimulus.
The ability to shorten forcibly when adequately stimulated.
The ability to be stretched or extended.
The ability of a muscle fibre to recoil and resume its resting length after being stretched.
Muscle Functions
Producing movement, maintaining posture, stabilizing joints, and generating heat (skeletal muscle = most responsible for creating heat)
Fine sheath of connective tissue consisting mostly of reticular fibres that surrounds each individual muscle fibre.
Discrete bundle of muscle cells, segregated from the rest of the muscle by a connective tissue sheath.
Fibrous connective tissue which surrounds each fascicle.
An overcoat of dense irregular connective tissue which surrounds the whole muscle.
Series Elastic Components
Connective tissue sheaths and tendons which contribute to the natural elasticity of muscle tissue.
Rodlike contractile element which occupies most of the muscle cell volume. Composed of sacromeres arranged end to end.
The contractile unit of a muscle fibre, composed of myofilaments made up of contractile proteins.

The distance between two Z discs.

Consists of an A band flanked by two half I-bands.

Functional unit of skeletal muscle.
The movable bone to which a muscle is attached.
The immovable or less movable bone to which a muscle is attached.
Sheetlike, flat connective tissue tendon which anchors muscle to connective tissue covering of a skeletal element or to the fascia of other muscles.
Direct/Fleshy Attachments
The epimyseium of the muscle is fused to the periosteum of a bone or perichondrium of a cartilage.
Indirect Attachments
The muscle's connective tissue wrappings extend beyond the muscle either as a ropelike tendon or an aponeurosis. Tendons conserve space.
A red pigment that stores oxygen in muscle cells.
Granules of stored glycogen in muscle cells.
A Band
The dark, central region of a sarcomere consisting of thick filaments and thin filaments. The thin filaments don't overlap, leaving lighter region called the H zone.
I Band
Lighter bands on either end of a sarcomere, consisting only of thin filaments. Contains the midline interruption known as a Z disc.
H Zone
Lighter stripe in the midsection of the A band that corresponds to the region where there is only thick fibres and no thin fibres.
M line
Dark line at the centre of the H zone
Z disc
Darker area interrupting the midline of the I bands.
Thick Filaments
Myosin-based filaments extending the entire length of the A band in the sarcomere.
Thin Filaments
Actin-based filaments that extend across the I band and partway into the A band of a sarcomere.
Protein which makes up thick filaments.

Consists of a rodlike tail made from two interwoven heavy polypeptide chains and two globular heads.

The heads link the thick and thin filaments together, forming cross bridges.

The heads also contain ATP binding sites and ATPases to generate energy for contraction.
Protein that coils back on itself to create a helix, forming the thin filament.
G Actin
Globular actin. The actin subunit which bears the active sites to which the myosin heads attach during contraction.
F Actin
Fibrous actin. Polymer of actin which forms up the backbone of each thin filament.
Two strands of this rod-shaped protein spiral about the actin core to help stiffen the thin filament.

In a relaxed muscle fibre, they block actin's active sites so that the myosin heads cannot bind to the thin filament.
A three polypeptide complex consisting of TnI (actin-binding/inhibitor), TnT (tropomyosin-binding/positioner), and TnC (calcium binding)
Muscle that has primary responsibility for an action.
Muscle that has the same action as the prime mover.

Aids the agonist.
Muscle that opposes the action of the prime mover/agonist.
Parallel to the long axis.
At an angle to the long axis.
Sarcoplamsic Reticulum
An elaborate smooth ER with interconnecting tubules which surround each myofibril.

Regulates intracellular levels of ionic calcium.
Terminal Cisternae
Large, perpendicular cross channels of the sarcoplasmic reticulum at the A band-I band junctions.

Flank T-tubules.
Elongated tubes formed by the penetration of the sarcolemma into the muscle cell at each A band-I band junction.

Conducts impulses to the deepest regions of the muscle cell and to every sarcomere. Impulses signal for the release of Ca++ from the adjacent terminal cisternae. Ensures that every myofibril in the muscle fibre contracts at virtually the same time.
Successive groupings of the three membranous structures (terminal cisterna, T tubule, terminal cisterna)
The activation of myosin's cross bridges, which are the force-generating sites.

Shortening occurs when the tension generated by the cross bridges on the thin filaments exceeds the forces opposing shortening.
Contraction ends when the cross bridges become inactive and the tension generated declines.
Sliding Filament Theory of Contraction
During contraction, the thin filaments slide past the thick ones so that the actin and myosin filaments overlap to a greater degree.

Overall, the distance between successive Z discs is reduced, the I bands shorten, the H zones disappear, and the contiguous A bands move closer together but do not change in length.
Calcium in Muscle Contraction
(1) The AP propagates along the sarcolemma and down the T tubules.

(2) Transmission of the AP past the triads causes the terminal cisternae to release Ca++

(3) Some of the Ca++ bind to troponin, which changes shape and removes the blocking action of tropomyosin.

(4) Myosin heads attach and pull the thin filaments toward the centre of the sarcomere.

(5) The short-lived Ca++ signal ends & the continually active ATP-dependent Ca pump moves Ca back to the sarcoplasmic reticulum.

(6) Tropomyosin blockade is re-established. Relaxation occurs.

Discrete bundle of muscle cells, segregated from the rest of the muscle by a connective tissue sheath.

Add Cards

You must Login or Register to add cards