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Muscles Ch. 6
Question | Answer |
---|---|
4 characteristics of muscles? | contractility, excitability, extensibility, elasticity |
what is an epimysium? | connective tissue sheath surrounding each skeletal muscle |
myofibrils | threadlike structure that extends from one end of the fiber to the other |
2 major kinds of protein fibers | actin myofilaments and myosin myofilaments |
actin | thin myofilaments |
myosin | thick myofilaments |
sacromeres | joined end to end to form the myofibril; formed by actin and myosin; basic structural and functional unit of muscle |
I band | on each side of the Z line; consists of actin |
A band | extends the length of the myosin |
H zone | in the center of each sarcomere. |
positive and negative charge? | positive- outside of cell membrane. negative- inside of cell membrane |
resting membrane potential | charge difference across the membrane |
action potential | brief reversal of back of the charge |
motor neurons | nerve cells that carry action potentials to skeletal muscle fibers. |
synapse (neuromuscular junction) | near center of cell; formed by each branch that connects to the muscle. |
fascia | connective tissue outside the epimysium |
perimysium | surrounds fasciculi; is loose connective tissue |
fibers | single muscle cells that create fasciculi |
endomysium | connective tissue sheath surrounding each muscle fiber |
cytoplasm of each fiber | myofibrils |
resting membrane potential | charge difference across the membrane |
Action potential | brief reversal of the charge |
motor nuerons | nerve cells that carry action potentials to skeletal muscle fibers |
Synapse | near center of cell |
another word for synapse | neuromuscular junction |
motor unit | single motor neuron and all skeletal muscle fibers it innervates |
how is a synapse formed? | an enlarged nerve terminal resting in an indentation of the muscle cell membrane. |
presynaptic terminal | enlarged nerve terminal |
synaptic cleft | space between the presynaptic terminal and the muscle cell |
muscular fiber | postsynaptic terminal |
what does each presynaptic terminal include? | synaptic vessels |
synaptic vessels secret a neurotransmitter called what? | acetylcholine |
what does acetylcholine do? | diffuses across the synaptic cleft and binds to the postsynaptic terminal causing a change in the postsynaptic cell. |
acetylcholinesterase | enzyme that breaks down acetylcholine |
what happens when sarcomeres shorten? | the muscle shortens |
how does muscle contraction occur? | actin and myosin myofilaments slide past each other |
sliding filament mechanism | sliding of actin myofilaments past myosin myofilaments during contraction |
What bands shorten? | H and I |
What bands stay the same? | A bands |
Muscle Twitch | contraction of an entire muscle in response to a stimulus |
tetany | muscle remains contracted without relaxing |
threshold | a muscle fiber won't contract until it reaches this level |
all-or-none-response | a muscle fiber won't contract, but when it does, it does maximally |
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 where muscles relax |
recruitment | increase in number of motor units being activated |
ATP is needed for what | needed for energy for muscle contraction |
where is atp produced? | in the mitochondria |
What is ADP | adenosine diaphosphate |
True or False? It is necessary for muscle cells to constantly produce ATP | true |
creatine phosphate | high-energy molecule stored when at rest |
Can muscles store ATP at rest | no |
energy contained in ATP is used to synthesize what? | creatine phosphate |
anaerobic respiration | without oxygen |
aerobic respiration | with oxygen |
anaerobic example | lifting weights |
aerobic example | swimming |
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 | when ATP is used during muscle contraction faster than it can be produced in the muscle cells |
fast-twitch fibers | contract quickly and fatigue quickly |
slow-twitch fibers | contract more slowly and are more resistant to fatigue |
origin | most stationary end of muscle |
insertion | end of muscle undergoing the greatest movement |
belly | portion of muscle between the origin and the insertion |
true or false? Some muscles have multiple origins or head | true |
synergists | muscles that work together to accomplish specific movements |
anatgonists | muscles that work in opposition to each other |
prime mover | in a group of synergists, it's one muscle that plays a major role in accomplishing the desired movement |
how are muscles named? | according to location, size, shape, orientation of fibers, origin, insertion, and function |
occipitofrontalis | raises eyebrows |
orbicularis oculi | closes eyelids and causes "crows feet" |
orbicularis oris | puckers the lips |
zygomaticus | smiling muscle |
levator labii superioris | sneering |
depressor anguli oris | frowning |
mastication | chewing |
sternocleidomastoid | lateral neck muscle and prime mover |