Anatomy & Physiology - Muscular System Vocabulary PT2

Antagonist

Antagonist

 These muscles act in opposition to the movement generated by the agonists and are responsible for returning a limb to its initial position.

Hamstrings

any one of the three posterior thigh muscles in between the hip and the knee (from medial to lateral: semimembranosus, semitendinosus and biceps femoris). 

Belly

The widest part of a muscle

Insertion

 the place where one end of a muscle is attached to the freely moving bone of its joint.

Complete Tetany

 the stimulus frequency is so high that the relaxation phase disappears completely, contractions become continuous.

Myocyte

A muscle cell

Synaptic Vesicle

 small, electron-lucent vesicles that are clustered at presynaptic terminals. They store neurotransmitters and release them by calcium-triggered exocytosis.

Conductivity

 Ability to cross space in between neurons. 

Myofibril

a cylindrical bundle of contractile filaments within the skeletal muscle cell. These are composed of individual contractile proteins called myofilaments.

Temporal Summation

 the effects of impulses received at the same place can add up if the impulses are received in close temporal succession. 

Contractility

the ability of muscle cells to forcefully shorten

Myofilament

threadlike structures that comprise the myofibril inside the muscle cell. There are two main types of myofilaments: thin filaments and thick filaments. In skeletal muscle, these are arranged in a repeating pattern of light and dark bands.

Tendon

 a flexible but inelastic cord of strong fibrous collagen tissue attaching a muscle to a bone.

Contraction Phase

 A single muscle twitch has a latent period, a contraction phase when tension increases, and a relaxation phase when tension decreases.

Myoglobin

a protein that's found in striated muscles, which includes skeletal muscles and heart muscle. Its main function is to supply oxygen to myocytes.

Elasticity

 the ability to recoil or bounce back to the muscle's original length after being stretched.

Myosin

 a fibrous protein that forms (together with actin) the contractile filaments of muscle cells and is also involved in motion in other types of cells.

Endomysium

  the key element that separates single muscle fibers from one another. It allows their autonomous gliding during muscle contraction. 

Mysoin ATPase

 An enzyme that causes ATP hydrolysis which provides energy for actomyosin contraction.

Epimysium

 a sheath of fibrous elastic tissue surrounding a muscle.

Neuromuscular Junction

  a synaptic connection between the terminal end of a motor nerve and a muscle (skeletal/ smooth/ cardiac).

Threshold Stimulus

The minimum strength required for the stimulus to initiate the response of muscle contraction

Oxygen Debt

 The difference between the amount of oxygen needed by the muscles and the actual amount present 

Titin

 a molecular spring in muscle cells. Binds calcium at specific sites, thereby increasing its stiffness.

Extensibility

 the ability of a muscle to be stretched. 

Synergist

assists the agonist muscle or “primary mover” for a specific action at a joint. This muscle is not the main muscle involved in the action, but works in synergy with the primary muscle.

Origin (Head)

 the proximal site that stays more stable and relatively fixed during muscle contraction. The head is a portion at the end of the origin muscle where it fixes to the bone.

Fixator

  A muscle which acts as the stabilizer and helps the agonist work effectively of one part of the body during movement of another part. 

Perimysium

 the sheath of connective tissue surrounding a bundle of muscle fibers.