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Muscular system Ch
Chapter 9 definitions
| Term | Definition |
|---|---|
| Muscle fiber | A skeletal muscle cell |
| Endomysium | Delicate connective tissue that covers each muscle fiber |
| Fascicles | Bundles of muscle fibers |
| Perimysium | Sheath of tougher connective tissue that encase the fascicles |
| Epimysium | Surrounds the muscle as a whole and binds all the muscle fibers together |
| Fascia | Connective tissue surrounding the muscle outside the epimysium |
| Deep fascia | Connective tissue that lies between muscles |
| Superficial fascia | Hypodermis that resides just under the skin |
| Direct attachment | Muscle fibers merge with the periosteum of the bone, forming a strong attachment |
| Indirect attachment | The epimysium extends past the muscle as a tendon. The tendon then merges with the periosteum |
| Aponeurosis | Broad tendon that attaches muscle to muscle |
| Sarcolemma | Plasma membrane surrounding each muscle fiber |
| Sarcoplasm | Cytoplasm of the cell |
| Myofibrils | Long protein bundles that fill the sarcoplasm and store glycogen and oxygen |
| Sarcoplasmic reticulum | (SR) Smooth endoplasmic reticulum of a muscle fiber that surrounds each myfibril and where calcium ions are stored |
| Transverse (T) tubules | System of tubules that extends across the sarcoplasm formed from inward projections of the sarcolemma; allow electrical impulses to travel deep into the cell |
| Myofilaments | Finer fibers within myofibrils; can be thick or thin; gives skeletal muscles its striated appearance |
| Thick myofilaments | Made of the protein myosin |
| Thin myofilaments | Made of the protein actin |
| Z-disc | Also called a Z-line; serves as an anchor point for thin myofilaments |
| Sarcomere | Section between the Z-discs where muscle contraction occurs |
| Cross bridge | When the myosin heads latch onto the actin myofilaments |
| Motor neuron | Nerve that stimulates a skeletal muscle to cause contraction |
| Neuromuscular junction | Connection between a motor neuron and a muscle fiber |
| Muscle tone | Continuous state of partial contraction |
| Motor unit | The neuron and all the fibers it stimulates |
| Twitch | Single, brief contraction |
| Threshold | Minimum voltage needed to cause a muscle fiber to contract |
| Treppe | Successive twitches contract more forcefully than the previous one; staircase phenomenon |
| Incomplete tetanus | Rapid contraction with only partial relaxation |
| Complete tetanus | Rarely occuring, twitches merge into one prolonged contraction |
| Recruitment | The process by which an increasing number of motor units are called into action |
| Isometric contractions | The tension within a muscle increases while its length remains the same |
| Isotonic contractions | The muscle changes length and moves a load, while the tension within the muscle remains the same |
| Aerobic | With oxygen |
| Anaerobic | Without oxygen |
| Origin | End of a muscle that attaches to the more stationary bone |
| Belly | Thick mid-section of a muscle |
| Insertion | End of a muscle that attaches to the more movable bone |
| Prime mover | Main muscle triggering the movement |
| Synergists | Muscles that assist the prime mover |
| Antagonists | Oppose the action of the prime mover, therefore balancing the movement |
| Hypertrophy | Muscle enlargement due to strength training |
| Atrophy | Muscle shrinkage due to lack of use |
| Flexors | Muscles that flex the wrist, located on the anterior of the forearm |
| Extensors | Muscles that extend the wrist, located on the posterior of the forearm |
| Frontalis | Muscle of the head and neck that raises eyebrows and shows expressions of surprise |
| Orbicularis oculi | Muscle of the head and neck that closes the eye |
| Zygomaticus | Muscle of the head and neck that makes laughing possible |
| Orbicularis oris | Muscle of the head and neck that draws lips together |
| Buccinator | Muscle of the head and neck that makes smiling and blowing possible |
| Temporalis | Muscle of the head and neck that closes the jaw |
| Masseter | Muscle of the head and neck that closes the jaw |
| Sternocleidomastoid | Muscle of the head and neck that flexes the head; "prayer muscle" |
| Trapezius | Muscle of the head and neck that extends the head (looking up), flexes the head to one side, and elevates the shoulder |
| External intercostals | Muscles of the truck that elevate the ribs |
| Internal intercostals | Muscles of the trunk that depress the ribs |
| Diaphragm | Muscle of the trunk that enlarges the thorax to trigger inspiration |
| Rectus abdominis | Muscle of the trunk that flexes lumbar region to allow bending forward |
| Transverse abdominal | Muscle of the trunk that compresses contents of the abdomen |
| Internal oblique | Muscle of the trunk that stabilizes the spine to maintain posture and permits rotation at the waist |
| External oblique | Muscle of the trunk that stabilizes the spine |
| Deltoid | Muscle of the shoulder and upper arm that abducts, flexes and rotates the arm |
| Pectoralis major | Muscle of the shoulder and upper arm that flexes and adducts the upper arm |
| Serratus anterior | Muscle of the shoulder and upper arm that pulls the shoulder down and forward |
| Trapezius | Muscle of the shoulder and upper arm that raises or lowers shoulders |
| Latissimus dorsi | Muscle of the shoulder and upper arm that adducts and extends the arm backward |
| Rotator cuff | Muscle of the shoulder and upper arm that rotates and adducts the arm; consists of 4 muscles - supraspinatus, infraspinatus, teres minor, and subscapularis |
| Brachialis | Muscle that flexes the forearm |
| Biceps brachii | Muscle that flexes the forearm |
| Triceps brachii | Muscle that extends the forearm |
| Brachioradialis | Muscle that helps flex the forearm |
| Pronator muscles | Pronates the forearm |
| Supinator | Supinates the forearm |
| Iliacus | Muscle acting on the hip and thigh that flexes the thigh |
| Psoas major | Muscle that acts on the hip and thigh that flexes the thigh |
| Sartorius | Muscle that acts on the hip and thigh that adducts and flexes the leg; permits sitting "cross-legged" |
| Adductor muscles | Muscles that acts on the hip and thigh that adducts the thigh; consists of 4 muscles - adductor magnus, adductor brevis, adductor longus, and gracilis |
| Quadriceps femoris | Muscles that act on the hip and thigh that flex the thigh and extend the leg; consists of 4 muscles - rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius |
| Gluteus medius | Muscle acting on the hip and thigh that abducts and rotates the thigh outward |
| Gluteus maximus | Muscle acting on the hip and thigh that extends and rotates the thigh outward |
| Gluteus minimus | Muscle acting on the hip and thigh that abducts and rotates the thigh |
| Hamstring group | Muscles that act on the hip and thigh that extend the thigh; consists of 3 muscles - biceps femoris, semitendinosus, semimembranosus |
| Gastrocnemius | Muscle acting on the foot that causes plantar flexion of the foot |
| Soleus | Muscle acting on the foot that causes plantar flexion of the foot |
| Tibialis anterior | Muscle acting on the foot that causes dorsiflexion of the foot |
| Extensor digitorum longus | Muscle acting on the foot that causes dorsiflexion of the foot |
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