Term | Definition |
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 |