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Muscles

Chapter 6

TermDefinition
Contractility the ability of skeletal muscle to shorten with force.
Excitability the capacity of skeletal muscle to respond to a stimulus.
Extensibility the ability to be stretched.
Elasticity ability to recoil to their original resting length after they have been stretched.
Epimysium a connective tissue sheath that surrounds a skeletal muscle.
Fascia another connective tissue that is located outside the epimysium.
Fasciculi (Fascicle) muscle composed of numerous visible bundles.
Perimysium loose connective tissue that surrounds fasciculi.
Fibers single muscle cells.
Endomysium connective tissue sheath.
Myofibrils a threadlike structure that extends from one end of the fiber to the other.
Actin Myofilaments thin myofilaments. They resemble 2 minute strands of pearls twisted together.
Myosin Myofilaments thick myofilaments. They resemble bundles of minute golf clubs.
Sarcomeres the basic structural and functional unity of the muscle.
Resting Membrane Potential the charge difference across the membrane.
Action Potential the brief reversal back of the charge.
Motor Neurons are nerve cells that carry action potentials to skeletal muscle fibers.
Synapse near the center of the cell.
Motor Unit a single motor neuron and all the skeletal muscle fibers that it innervates.
Presynaptic Terminal the enlarged nerve terminal.
Synaptic Cleft the space between the presynaptic terminal and the muscle cell.
Synaptic Vesicles secretes the neurotransmitter.
Acetylcholine diffuses across the synaptic cleft and binds to the postsynaptic terminal causing a change in the postsynaptic cell.
Acetylcholinesterase yields only one action potential in the skeletal muscle and only one contraction of the muscle cell (breaks it down).
Sliding Filament Mechanism the sliding of actin myofilaments past myosin myofilaments during contraction.
Muscle Twitch is a contraction of an entire muscle in response to a stimulus that causes the action potential in one or more muscle fibers.
Threshold a muscle fiber will not respond to stimulus until the stimulus reaches this level
All-or-None Response the muscle fiber will contract maximally.
Lag Phase the time between application of a stimulus to a motor neuron and the beginning of a contraction.
Contraction Phase the time of contraction.
Relaxation Phase the time during which the muscle relaxes.
Tetany where the muscle remains contracted without relaxing.
Recruitment the increase in number of motor units being activated.
Creatine Phosphate when at rest they can't stockpile ATP but they can store another high-energy molecule.
Anaerobic Respiration without oxygen.
Aerobic Respiration with oxygen (more efficient).
Oxygen Debt the amount of oxygen needed in chemical reactions to convert lactic acid to glucose and to replenish the depleted stores of creatine phosphate stores in muscle cells.
Muscle Fatigue results when ATP is used during muscle contraction faster
Isometric (equal distance) the length of the muscle does not change, but the amount of tension increases during the contraction process.
Isotonic (equal tension) the amount of tension produced by the muscle is constant during contraction, but the length of the muscle changes.
Muscle Tone muscle tone refers to constant tension produced bu muscles of the body for long periods of time. Keeps head up and back straight.
Fast Twitch Fibers contract quickly and fatigue quickly. Well adapted to perform anaerobic metabolism. Ex. white meat of a chicken's breast.
Slow Twitch Fibers contract more slowly and are more resistant to fatigue. They are better suited for aerobic metabolism. Ex. dark meat of a duck's breast or the legs of a chicken.
Origin (head) is most stationary end of the muscle.
Insertion is the end undergoing the greatest movement.
Belly the portion of muscle between the origin and the insertion
Synergists muscles that work together to accomplish specific movements
Antagonists muscles that work in opposition to one another
Prime Mover a group of synergists, if one muscle plays the major role in accomplishing the desired movement
Nomenclature (names that are descriptive) location, size, orientation of fibers, shape, origin, insertion, and function
Occipitofrontalis raises the eyebrows
Orbicularis Oculi closes the eyelids and causes "crows feet" wrinkles in the skin at the lateral corners of the eye.
Orbicularis Oris puckers the lips
Buccinator flattens the cheeks. Trumpeter's muscle
Orbicularis Oris & Buccinator kissing muscles
Zygomaticus smiling muscle
Levator Labii Superioris sneering
Depressor Anguli Oris frowning
Mastication chewing
Temporalis & Masseter 2 pairs of mastication
Intrinsic Tongue Muscle change the shape of the tongue
Extrinsic Tongue Muscle move the tongue
Sternocleidomastoid lateral neck muscle and prime mover
Erector Spinae group of muscles on each side of the back. Responsible for keeping the back straight and the body erect
External Intercostals elevate the ribs during inspiration
Internal Intercostals contract during forced expiration
Diaphragm accomplishes quiet breathing. Dome-shaped muscle. Aids in breathing
Linea Alba consists of white connective tissue rather than muscle (tendinous area of the abdominal wall)
Rectus Abdominis on each side of the linea alba
Tendinous Inscriptions cross the rectus abdominis at three or more locations, causing the abdominal wall of a well-muscled person to appear segmented.
Trapezius rotates scapula
Serratus Anterior pulls scapula anteriorly
Pectoralis Major adducts and flexes the arm
Latissimus Dorsi medially rotates, adducts, and powerfully extends the arm. "Swimmer muscle."
Pectoralis Major & Latissimus Dorsi attaches the arm to the thorax
Deltoid attaches the humerus to the scapula and clavicle, and is the major abductor of the upper limb.
Triceps Brachii (3 heads / antagonists) extends the forearm. Occupies the posterior compartment of the arm
Biceps Brachii (2 heads / antagonists) flexes the forearm. Occupies the anterior compartment of the arm.
Brachialis flexes the forearm
Brachioradialis flexes and supinates the forearm
Retinaculum strong band of fibrous connective tissue that covers the flexor and extensor tendons and holds them in place around the wrist so that they do not "bowstring" during muscle contraction
Flexor Carpi flexes the wrist
Extensor Carpi extends the wrist
Flexor Digitorium flexes the fingers
Extensor Digitorium extends the fingers
Intrinsic Hand Muscles 19 hand muscles located within the hand
Interossi located between the metacarpals, are responsible for abduction and adduction of the fingers
Gluteus Maximus buttocks. Contributes most of the mass of the buttocks.
Gluteus Medius hip muscle and common injection site
Quadriceps extends the leg; anterior thigh muscles
Sartorius "tailors muscle" flexes the thigh
Hamstring posterior thigh muscles; flexes the leg and extends the thigh (wolves kill this way)
Gastrocnemius (left) & Soleus (right) (back view) form the calf muscles. They join to form the calcaneal tendon
Calcaneal Tendon (Achilles Tendon) flex the foot and toes
Peroneus the lateral muscles of the leg "planters flexion (turning the lateral side of the foot outward)
Intrinsic Foot 20 muscles located within the foot. Muscles flex, extend, abduct, and adduct the toes
Created by: Iyanna Patrick