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Ch.6 Muscles


Contractility Shorten with force
Excitability Respond to a stimulus
Extensibility Recoil
Epimysium Connective tissue sheath that surrounds each skeletal muscle
Fascia Connective tissue located outside the Epimysium. Surrounds and separates muscles
Fasciculi Numerous visible bundles
Perimysium Surrounds Fasciculi; Loose connective tissue
Fasciculi are composed of SINGLE Muscle Cells
Muscle cells Fibers
Muscle Fiber contains Several nuclei
Endomysium Connective tissue sheath that surrounds each muscle fiber
Cytoplasm of each fiber is filled with Myofibrils
Myofibrils Threadlike structure that extends to both sides of the fiber
2 Major types of protein fibers Actin & Myosin
Thin myofilaments Actin
Thick myofilaments Myosin
Sarcomere Basic structural and functional unity of the muscle
I bands are Light
A bands are Dark
H zone contains Myosin
Resting Membrane potential Charge difference across the membrane
Action Potential Brief reversal back of the charge
Motor Neurons nerve cells that carry action potentials to skeletal muscle fibers
Neuromusclular Junction Synapse near the center of the cell
Motor unit Single motor neuron and all skeletal muscle fibers it innervates
Presynaptic Terminal Enlarged nerve terminal
Acetylcholine Neurotransmitter
Acetylcholinesterase Enzymes that break down acetylcholine
Muscle Contraction Occurs when As actin and myosin myofilaments slide past one another.
Sliding Filament Mechanism Sliding of actin myofilaments past myosin myofilaments during contraction
Muscle Twitch Contraction of an entire muscle in response to a stimulus that causes the action potential in one or more muscle fibers
Time of contraction Contraction phase
Relaxation Phase Time during which the muscle relaxes.
Tetany Where the muscle remains contracted without relaxing
Recruitment The increase in the number of motor units being activated
ATP is needed for Energy for muscle contraction
ATP is produced in the Mitochondria
ATP is Short-lived and unstable
ATP Adenosine Triphosphate
Anaerobic Respiration Without oxygen
Aerobic Respiration With Oxygen
Oxygen Debt Amount of oxygen needed in chemical reactions to convert lactic acid to glucose.
Muscle Fatigue When ATP is used during muscle contraction faster than it can be produced in the fibers.
2 types of muscle contractions Isometric & Isotonic
Isometric Equal distance
Isotonic Equal Tension
Muscle Tone Constant tension produced by muscles of the body for long periods of time.
Muscle Tone keeps Head up and Back straight
Fast-Twitch Contract quickly and fatigue quickly
Slow-Twitch Contracts slowly and more resistant to fatigue
Origin (Head) most stationary end of the muscle
Insertion Is the end of the muscle undergoing the greatest moment.
Belly is located Between origin and the insertion
Synergist Muscles that work together
Antagonist Muscles that work in opposition
Prime Mover Muscle that plays major role
Nomenclature Shape,Size,Orientation of fibers, shape,origin,insertion,and function.
Occipitofrontalis Raises eyebrows
Orbicularis Oris Puckers
Buccinator Flattens cheeks
Zyogomaticus Smiling
Levatorlabii Sneering
Deppressor Anguliaris Frowning
Mastication Chewing
Two muscles of the tongue Intrinic and Extrinic
Intrinic Changes the shape
Extrinic Moves
Neck: Sternocle Idamastiod Rotates and extends head
Neck: Tarticallis Twisted neck; Wry neck
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 muscles”
Triceps brachii Extends the forearm. Occupies the posterior compartment of the arm.
Biceps brachii Flexes the forearm. Occupies the anterior compartment of the arm.
Brachialis Flexes forearm
Brachioradialis Flexes and supinates the forearm
Retinaculum (bracelet) 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.
19 hand muscles called the Intrinsic hand muscles
Interossi muscles, located between Metacarpals
Interossi muscles are responsible for Responsible for abduction and adduction of the fingers.
Gluteus maximus Buttocks
Quadriceps femoris Extends the leg; anterior thigh muscles
Sartorius “Tailors muscle”; flexes the thigh
Hamstring Posterior thigh muscles; flexes the leg and extends the thigh.
peroneus muscles Lateral muscles of the leg
20 muscles located within the foot Intrinsic foot muscles
The arm is attached to the thorax by the Pectoralis major and latissimus dorsi muscles.
Pectoralis major Adducts and flexes the arm
Latissimus dorsi Medially rotates, adducts, and powerfully extends the arm. “Swimmer muscles”
Deltoid Attaches the humerus to the scapula and clavicle, and is the major abductor of the upper limb.
External intercostals Elevate the ribs during inspiration.
Internal intercostals Contract during forced expiration.
Diaphragm – accomplishes Quiet breathing.
Dome-shaped muscle Aids in breathing.
Serratus anterior Pulls scapula anteriorly
Trapezius Rotates scapula
Created by: kaykay82596



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