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Ch 6

Four major functional characteristics Contractility Excitability Extensibility Elasticity
The ability of skeletal muscles to shorten with force Contractility
The capacity of skeletal muscle to respond to a stimulus Excitability
The ability to be stretched Extensibility
Ability to recoil to their original resting length after they have been stretched Elasticity
Each skeletal muscle is surrounded by a connective tissue sheath called the Epimysium
Another connective tissue located outside the epimysium. Surrounds & separates muscles. Fascia
Threadlike structure that extends from one end of the fiber to the other Myofibrils
The fasciculi are composed of single muscle cells called Fibers
Myofibrils consist of 2 major kinds of protein fibers: Actin & myosin myofilaments
Thin myofilaments Actin myofilaments
Thick myofilaments Myosin myofilaments
Actin and myosin myofilaments form highly ordered units called Sarcomeres
What is the basic structural and functional unity of the muscle? The Sarcomere
Nerve cells that carry action potentials to skeletal muscle fibers Motor neurons
Occurs as actin and myosin myofilaments slide past one another causing the sarcomeres to shorten. Muscle contraction
A contraction of an entire muscle in response to a stimulus that causes the action potential in one or more muscle fibers Muscle twitch
• is needed for energy for muscle contraction • is produced in the mitochondria • is short-lived and unstable ATP (adenosine triphosphate)
Without oxygen Anaerobic respiration
The portion of the muscle between the origin and the insertion is the Belly
The _____ is the end of the muscle undergoing the greatest movement Insertion
The ____ is the most stationary end of the muscle Origin
Muscles that work together to accomplish specific movements are called Synergists
Muscles that work in opposition to one another Antagonists
Most muscles have names that are Descriptive
Some muscles are named according to their Location, size, orientation of fibers, shape, origin, insertion, and function, etc.
Occipitofrontalis Raises the eyebrows
Orbicularis oculi Closes the eyelid and causes "crow feet"
Orbicularis oris Puckers the lips
Buccinator Flattens the cheeks
Zygomaticus Smiling muscle
Levator labor superioris Sneering
Depressor Anguli oris Frowning
Mastication Chewing
4 pairs of mastication muscles 2 pairs of ptertygoids, temporalis, and masseter
Change the shape of the tongue Intrinsic tongue muscles
Move the tongue Extrinsic tongue muscles
Sternocleidomastoid Lateral neck muscle and prime mover
Group of muscles on each side of the back Erector spinae
Elevate the ribs during inspiration External intercostals
Contract during forced expiration Internal intercostals
Diaphragm Accomplished quiet breathing
Trapezius Rotates scapula
Serratus anterior Pulls scapula anteriorly
Pectoralis major Adducts and flexes the arm
Latissimus dorsi Medially rotates, adducts, & powerfully extends the arm
Deltoid Attaches the humerus to he scapula and clavicle, major abductor of the upper limb
Triceps brachii Extends the forearm
Biceps brachii Flexes the forearm
Brachioradialis Flexes and supinates the forearm
Flexor carpi Flexes the wrist
Extensor carpi Extends the wrist
Flexor digitorum Flexes the fingers
Extensor digitorum Extends the fingers
19 hand muscles Intrinsic hand muscles
Interossi muscles Located between the metacarpals. Responsible for abduction and adduction of the fingers
Gluteus maximus Buttocks
Gluteus medius Hip muscle and common injection site
Quadriceps femoris Extends the leg; anterior thigh muscles
Sartorius Flexes the thigh "tailors muscle"
Hamstring Muscles- posterior thigh muscles; flexes the leg and extends the thigh
Gastrocnemius and soleus Form the calf muscle
Calcaneal tendon Flex the foot and toes
Peroneus The lateral muscles of the leg
Intrinsic foot muscles 20 muscles located within the foot
Extends the length of the myosin The A band
Center of each sarcomere, consists of only myosin H zone
Change difference across the membrane Resting membrane potential
The brief reversal back of the charge Action potential
Nerve cells that carry action potentials to skeletal muscle fibers Motor neurons
A single motor neuron and all the skeletal muscle fibers it innervates Motor unit
The enlarged nerve terminal Presynaptic terminal
The space between the presynaptic terminal and the muscle cell is Synaptic cleft
Where the muscle remains contracted without relaxing Tetany
The increase in number of motor units being activated is called Recruitment
Created by: Codyjrowe