Muscular System Flashcards
Skeletal muscle
Controlled by the conscious mind and moves the bones of the skeleton, also referred to as voluntary striated muscle
Cardiac muscle
Makes up the structure of the heart and controls the heart to beat
Smooth muscle
Found all over the body in places such as the eyes, the air passageways in the lungs, the stomach and intestines, the urinary bladder, the blood vessels, and the reproductive tract
Epimysium
A fibrous connective sheath surrounding skeletal muscle
Aponeuroses
Broad sheet of fibrous connective tissue which help muscles attach to other muscles or bones
Linea alba
The most prominent aponeurosis, runs lengthwise between the muscles on an animal’s ventral midline
Agonist (or prime mover)
Used to describe a muscle or muscle group that directly produces a desired movement
Antagonist
A muscle or muscle group that directly opposes the action of an agonist
Synergist
A skeletal muscle that contracts at the same time as an agonist and assists it in carrying out its action
Fixator muscles
Stabilize joints to allow other movements to take place
Sarcolemma
Muscle cell membrane
Sarcoplasmic reticulum
A storage of organelle for calcium ions
Myofibrils
Hundreds or thousands creates most of the volume of one skeletal muscle fiber, composed of thousands of even tinier protein filaments
Transverse tubules (T-tubules)
A system of tubules that extend in from the sarcolemma
Sarcomere
The basic contracting unit of skeletal muscle
Z line or Z disc
A disc present on each end of a sarcomere
Actin
One protein filament responsible for contraction. Thin, attach to the Z lines and extend toward the center of the sarcomere but do not meet
Myosin
A protein filament responsible for contraction within a sarcomere. Thick, appear to float in the middle of the sarcomere between parallel actin fibers. Do not connect to Z lines
I bands
Large light-colored bands present microscopically in a myofibril, made up of thin actin filaments
A bands
Darker bands present between I bands, areas where the thick myosin filaments and thin actin filaments overlap
H band
The light-colored area located in the middle of the A band, made up of myosin filaments only, with no overlapping actin filaments, so it does not cover the entire width of the myosin filament
Cross-bridges
Two globular heads attached to a twisted tail produced by the myosin molecule, interacts with the actin to shorten the sarcomere during the muscle contraction
Neuromuscular junctions
Sites where the ends of motor nerve fibers connect to muscle fibers
Motor unit
Used to describe one nerve fiber and all the muscle fibers it innervates
Endomysium
A delicate connective tissue layer that surrounds each individual skeletal muscle fiber, composed of fine, reticular fibers
Fasicles
Groups of skeletal muscles, bound together by a tougher connective tissue layer called the perimysium
Perimysium
Tough connective tissue layer composed of reticular fibers and thick collagen fibers
Epimysium
A fibrous connective tissue layer composed largely of tough collagen fibers, surrounds groups of muscles
All-or-nothing principle
When an individual muscle fiber either contracts completely when it receives a nerve impulse, or it does not contract at all
Twitch contraction
A single muscle contraction, can be divided into three phases
Three phases of twitch contraction
The latent phase, the contracting phase, and the relaxation phase
Creatine phosphate (CP)
The “battery charger” that converts ADP back to ATP, a compound in muscle fibers
Myoglobin
Stored oxygen attached to large protein molecules
Aerobic metabolism
The process when strenuous muscle contractions begin to deplete the oxygen supply to a muscle fiber, myoglobin can release its stash of oxygen molecules to resupply the fiber
Cutaneous muscle
Skin muscle, when an animal twitches its skin to get rid of an insect
Intercalated discs
Firm, end-to-end attachments between cardiac muscle cells, also transmits impulses from cell to cell to allow large groups of cardiac muscle cells to contract in a coordinated manner
Sinoatrial (SA) node
The hearts “pacemaker”, located in the wall of the right atrium. The impulse that starts each heartbeat begins here
Two main forms of smooth muscle
Visceral smooth muscle and multi-unit smooth muscle
