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Chapter 6

Muscles

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 The ability to recoil to their original resting length after they have been stretched
Epimysium Each skeletal muscle is surrounded by a connective tissue sheath
Fascia Another connective tissue located outside the epimysium. It surrounds and separates muscles
Perimysium Loose connective tissue that surrounds the fasciculi
Myofibrils A threadlike structure that extends from one end of the fiber to the other
Fasciculi Composed of numerous visible bundles
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 Actin and myosin myofilaments form highly ordered units called
Actin & myosin myofilaments 2 major kinds of protein fiber
Sarcomere Basic structural and functional unity of the muscle
one Z-line disc to another Each sarcomere extends from
A banded appearance Arrangement of actin and myosin give
Actin Each Z-line is an attachment for
Myosin The A band extends the length of the
A band Darker, central region in each sarcomere
H-Zone Light area in the center. Consists of only myosin
M line Myosin myofilaments are anchored in the center of the sarcomere at a dark staining band called
Positively charged The outside of most cell membranes is
negatively charged inside of the cell membranes
Resting membrane potential The charge difference across the membrane is called
action potential The brief reversal back of the charge
Motor neurons nerve cells that carry action potentials to skeletal muscle fibers
Axons enters the muscles and branch
neuromuscular junction Each branch that connects to the muscle forms
synapse Another word for neuromuscular junction
Motor unit A single motor neuron and all the skeletal muscle fibers it innervates are called
neuromuscular junction formed by an enlarged nerve terminal resting in an indentation of the muscle cell membrane
presynaptic terminal enlarged nerve terminal
synaptic cleft the space between the presynaptic terminal and the muscle cell is the
postsynaptic terminal muscle fiber is the
synaptic vesicles secrete a neurotransmitter. Each presynaptic terminal contains one
Acetylcholine neurotransmitter
Sarcolemma The acetylcholine diffuses across the synaptic cleft and binds to receptor molecules in the muscle cell membrane
Acetylcholinesterase the acetylcholine released into the synaptic cleft between the neuron and the muscle cell is rapidly broke down by an enzyme
sliding filament mechanism the sliding of actin myofilaments past myosin myofilaments during contraction
A Bands do not change in length
H and I Bands shorten
Muscle twitch 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 that stimulus reaches a level called
all-or-none phenomenon
lag phase the time between application of a stimulus to a motor neuron and the beginning of a contraction
contraction phrase the time of contraction
relaxation phase time during which the muscle relaxes
tetany where the muscles remains contracted without relaxing
recruitment the increase in number of motor units being activated
Adenosine triphosphate ATP
ATP needed for energy for muscle contraction
ATP produced in the mitochondria
ATP short-lived and unstable. It degenerates to the more stable
ADP adenosine diphosphate
ADP plus phosphate
creatine phosphate Can't stockpile ATP but can store another high-energy molecule
Anaerobic respiration without oxygen
aerobic respiration with oxygen (more efficient)
oxygen debt amount of oxygen needed in chemical reactions to covert lactic acid to glucose and to replenish the depleted stores of creatine phosphate stores in muscle cells
Muscle fatigue occurs after exercising our muscles strenuously for a long time
Flexion movement, generally in the sagittal plane, that decreases the angle of the joint and brings two bones close together
extension opposite of flexion, so it is a movement that increase the angle, or the distance, between two bones or parts of the body
rotation movement of a bone around its longitudinal axis
abduction moving a limb away from the midline, or median plane, of the body
adduction opposite of abduction, so it is the movement of a limb toward the body midline
circumduction combination of flexion, extension, abduction, and adduction commonly seen in ball-and-socket joints such as the shoulder
Frontalis raises eyebrows
orbicularis oculi blinks and closes eyes
orbicularis oris closes and protrudes lips
temporalis closes jaw
zygomaticus raises corner of mouth
masseter closes jaw
buccinators compresses cheek as in whistling and sucking; holds food between teeth during chewing
sternocleidomastoid flexes neck; rotates head
platysma pulls corners of mouth inferiorly
pectoralis major adducts and flexes humerus
rectus abdominis flexes vertebral column
biceps brachii flexes elbow and supinates forearm
triceps brachii extends elbow
deltoid abducts humerus
trapezius extends neck and adducts scapula
latissimus dorsi extends and adducts humerus
erector spinae extends back
gluteus maximus extends hip
soleus plantar flexes foot
Created by: hale