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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 connective tissue sheath that surrounds skeletal muscle
Fascia connective tissue located outside the epimysium
Perimysium loose connective tissue that surrounds fasciculi
Four major functional characteristics of skeletal muscle Contractility, Excitability, Extensibility, Elasticity
Muscle cells muscle fibers
Bundle of muscles muscle fasiciuli
Myofibrils a threadlike structure that extends from one end of the fiber to the other
Actin myofilaments thin myofilaments
Myosin myofilaments thick myofilaments
Sarcomeres actin and myosin myofilaments highly ordered units and are joined from end to end to form the myofilfibril
Resting membrane potential the charge difference between the positively charge outside of most cell membranes and the negatively charged inside of most cell membranes
Action potential when a muscle cell is stimulated the charge of the cell is briefly reversed
Motor neurons nerve cells that carry sction motentials to skeletal muscle fibers
Neuromusclular junction or synapse axons that enter the muscles and branch that connects the muscles near the center of the cell
Motor unit a single motor neuron and all skeletal muscle fibers it innervates
Presynaptic terminal enlarged nerve terminal
Synaptic cleft space between the presynaptic terminal and the muscle cell
Synaptic vesicles secretes a neurotransmitter called acetycholine
Acetycholine a neurotransmittter secreted from the synaptic vesicles
Acetylcholinesterase the acetylcholine released into the synaptic cleft between the neuron and muscle cell is rapidly broken down by enzymes
Sliding filament mechanism the sliding of actin myofilaments past myosin myofilaments during contraction
Muscle twitch 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 a stimulus reaches this level
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 a muscle remains contracted without relax
Recruitment an increase in the number of motor units being activated
Creatine phosphate a high energy molecule that can be stored unlike ATP
Anaerobic respiration without oxygen
Aerobic respiration with oxygen
Oxygen debt the amount of oxygen needed in chemical reactions to convert lactic acid to glucose and replenish the depleted stores of creatine phosphate in muscle cells
Muscle fatigue results when ATP is used during muscle contraction faster than it can be produced in the muscle cells
Isometric the length of the muscle does not change, but the amount of tension increases during the contraction process
two types of muscle contractions isometric and isotonic
Isotonic the amount of tension produced by the muscle is constant during contraction, but the length of the muscle changes
Muscle tone refers to constant tension produced by muscles of the body for long periods of time
Fast-twitch fibers contract quickly and fatigue quickly. well adapted to perform anaerobic metabolism
Slow-twitch fibers contract more slowly and are more resistant to fatigue. better for aerobic metabolism
Origin the most stationary end of a muscle
Insertion the end of the muscle undergoing the greatest movement
Belly the portion of the muscle in between the origin and the insertion
Synergists muscles the work together to accomplish specific movements
Anatagonists muscles that work in opposition to one another
Thoracic Muscles muscles that move the thorax
Diaphragm accomplishes quiet breathing
External intercostals elevate the ribs during inspiration
Internal intercostals contract during forced expiration
Erector spinae group of muscles on each side of the back
Trapezius rotates scapula
Serratus anterior pulls scapula anteriorly
Pectoralis major adducts and flexes the arm
Latissimus dorsi rotates, adducts, and powerfully extends the arm
Deltoid attaches the humerus to the scapula and clavicle, and is the major abductor of the upper limb
Triceps brachi extends the forearm
Biceps brachii flexes the forearm
Brachialis flexes 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 digitorum flexes the fingers
Extensor digitorum extends the fingers
Gluteus maximus buttocks. Contributes most of the mass of the buttocks
Quadriceps femoris extends the leg; anterior thigh muscles
Sartorius flexes the thigh
Hamstring posterior thigh muscles; flexes the leg and extends the thigh
Gastrocnemius and soleus forms the calf muscle
calcaneal tendon (Achilles tendon) flexs the foot and toes
Peroneus the lateral muscles of the leg
Intrinsic foot muscles 20 muscles in the foot that flex extend, abduct, and adduct the toes
Created by: cody2482



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