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Muscles

Anatomy/Physiology Chapter 6 - Muscles

TermDefinition
Contractility ability to shorten skeletal muscles with force
Excitability capacity to respond to a stimulus
Extensibility ability to be stretched
Elasticity ability to recoil after muscles have been stretched
Epimysium connective tissue sheath surrounding the skeletal muscle
Fascia connective tissue located outside the epimysium; surrounds and separates muscles
Muscle Fasiculi numerous visible bundles inside muscles
Perimysium loose connective tissue surrounding the muscle fasiculi
Fibers the fasiculi are composed of these single muscle cells
Endomysium connective tissue sheath surrounding each fiber
Myofibrils threadlike structure that extends from one end of the fiber to the other
Actin Myofilaments thin; resemble two minute strands of pearls twisted together
Myosin Myofilaments thick; resemble bundles if minute golf clubs
Sacromeres basic structural and functional unity of the muscle
Z line attachment site for actin
I band light area on each side of the Z line that consists of actin
A band extends the length of the myosin and is the darkest central region in each sacromere
H zone light area in the center of each sacromere
M line dark staining band anchored in the center of the sacromere
Resting Membrane Potentisl 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
(Occipito)Frontalis moves the eyebrows
Zygomaticus used for smiling
Buccinator & Orbicularis Oris used for kissing
axons enter the muscles and branches
neuromuscular junction or synapse each branch that connects to the muscle forms _____ near the center of the cell
motor unit single motor neuron and all the skeletal muscle fibers it innervates
synaptic vesicles secrete a neurotransmitter
postsynaptic terminal muscle fiber
presynaptic terminal enlarged nerve terminal
synaptic cleft space between the presynaptic terminal and the postsynaptic terminal, or muscle cell
single muscle many motor units form ____
acetylcholine neurotransmitter that diffuses across synaptic cleft and binds to the postsynaptic terminal causing change in the postsynaptic cell
acetylcholinesterase enzymes that break down acetylcholine released into the synaptic cleft between the neuron and the muscle cell
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 muscle fibers
threshold point in which the muscle fiber will contract maximally
all-or-none response phenomenon of threshold
lag phase time between application of the stimulus to a motor neuron and the beginning of a contraction
contraction phase time of contraction
relaxation phase time during which the muscles relax
tetany condition in which the muscle remains contracted without relaxing
recruitment increase in number of motor units being activated
adenosine triphosphate (ATP) needed for energy for muscle contraction
ATP produced in the mitochondria, short-lived and unstable, it degeneratesto the more stable ADP plus phosphate
ADP more stable energy
creatine phosphate high-energy molecules that muscle cells can store
anaerobic respiration without oxygen
aerobic respiration with oxygen and is more efficient
oxygen debt 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 than it can be produced in the muslce cells
two types of muscle contraction isotonic, isometric
isometric (equal distance) length of the muscle does not change, but the ampunt 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 refers to constant tension produced by muscles of the body for long periods of time
fast-twitch fibers well adapted to perform anaerobic metabolism contract quickly
slow-twitch contract more slowly and more resistant
origin(head) most stationary part of the muscle
insertion part of the muscle that undergoes the greatest movement
belly located between the origin and the insertion
synergists muscles that work together
antagonists muscles that work opposite of each other
prime mover in a group of synergists, it plays the major role
muslces named according to location, direction, size, shape, etc.
muscles help what? to produce heat essential for maintenance or normal body temperature
what is each muscle fiber? single cylindrical cell containing several tissues
cytoplasm of each fiber is ____ filled with myofibrils
myofibrils consist of... two major protein fibers- actin myofilaments and myosin myofilaments
actin and myosin myofilaments form what? highly ordered units called sarcomeres
meuromuscular junction formed by an enlarged nerve terminal resting in an indentation of the muscle cell membrane
muscle contraction occurs as actin and myosin myofilaments slide past one another causing the sarcomeres to shorten
during sliding filament mechanism... H and I bands shorten, but the A bands do not change in length
if successive stimuli are given... you get successive twitches that occur so frequently the muscle does not have time to fully relax
during period of inactivity energy contained in ATP is used to synthesize creatine phosphate
points of attachment of the muscle origin(head) and insertion
two characteristics of skeletal muscle voluntary and are striated
outside of most cell membranes... positively charged compared to the inside of the cell membrane, which is negatively charged
gastrocnemius calf muscle
triceps brachii back of the arm and flexes the arm
biceps brachii front of the arm
quads front of the thigh
hamstrings back of the thigh
rectus abdominus abs
buttocks gluteus maximus
Created by: haleyskye96