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4 functions muscle provides to organs.
movement, maintenance of posture, joint stabilization, heat generation (shivering)
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What are the 4 specialized characteristics of muscle?
contractility (shortening), excitability (electrical impulse through nerve fibers), extensibility (PASSIVE stretching w/ contraction of opposing muscle), elasticity (recoils passively after being stretched)
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Locations of skeletal muscles.
attachments to bones, abdominal wall, esophagus
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Location of cardiac muscle.
Heart
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Location of smooth muscles.
Tubular organs (GI and repro tract), hair follicles, Eye, Vasculature
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Muscle cell type that provides contractile ability to small structures.
myoepithelium
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Example of myoepithelium.
around mammy gland epithelium to provide alveoli with ability to squeeze out milk products
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Myoepithelium is made of _______ or _______ epithelium.
columnar or cuboidal
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Connective tissue cells which have contractile ability; function in third-intention healing wounds.
myofibroblasts
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Muscle cells are called _________- because they are elongated.
fibers
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Contraction of muscles depends on _______, which include...
myofilaments; actin and myosin
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The plasma membrane of a muscle cell is called the _______.
sarcolemma
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Skeletal muscle fibers are ___________ because the embryonic cells fuse.
multinucleated
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Skeletal muscles cells have obvious _______ and contractions are ________.
striations; voluntary
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When a muscle span two or more joints, it is called _________.
biarticular/multijoint
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Muscle attachment that is so short that the muscle appears to attach directly to the bone.
Direct or "fleshy" attachment
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Muscle attachment in which the connective tissue extends well beyond the muscle.
Indirect attachment
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Example of direct attachment of muscles.
intercostal muscles
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Example of indirect muscle attachment.
flexors and extensors of the antebrachium
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2 types of indirect muscle attachments.
tendons, aponeurosis
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Skeletal muscles structure from biggest to smallest.
myofiber --> myofibrils --> myofilaments --> sarcomeres
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_________ are the organelles of the skeletal muscle cell; made up of ______.
myofibrils; filaments
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The basic unit of skeletal muscle contraction
sarcomere
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Myofibrils are long rows of repeating _________
sarcomeres
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Boundaries of sarcomeres are called _______.
Z discs (or lines)
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3 types of filaments that make up myofibrils and sarcomeres.
myosin (thick), actin (thin), titin (elastic)
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Sarcomere structure applies to......., but not....
skeletal and cardiac muscles; smooth muscle
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Proteins of the sarcomere (4)
myosin, actin, troponin, tropomyosin
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During sarcomere contraction, ___________ get closer together and ________ get smaller.
Z bands; I bands
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Invaginations of sarcolemma into the cell.
T tubules
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T tubules form a tubular network inside the muscle cell at the junction of...
the A and I bands
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The T system formed by T tubules allows for...
conduction of depolarization impulses for simultaneous contraction of sarcomeres
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Sarcoplasmic reticulum is synonymous with _______.
smooth endoplasmic reticulum (HOWEVER, only in muscle cells is it called this)
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The tubules of the sarcoplasmic reticulum surround ________ and form channels called _________, which serve the purpose to....
myofibrils; terminal cisternae; store Ca+ and release it when the muscles are stimulated to contract
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Motor neutrons innervate __________ and meet at a __________.
muscle fibers; motor end plate
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Neurotransmitters are released by nerve signals and initiate...
calcium ion release and muscle contraction
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A motor neuron and all the muscle fibers it innervates.
motor unit
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The finer the movement, the ________ the muscle fibers/motor unit.
fewer
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Release of neurotransmitters initiates the...
T system and ultimately, contraction
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The types of skeletal muscle fibers are..., and they are grouped based on...
fast, slow, and intermediate-twitch fibers; whether or not they predominantly use oxygen to produce ATP
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Large, predominantly anaerobic muscle fibers that fatigue rapidly majority of skeletal muscle fibers.
fast fibers (white muscle)
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Smaller skeletal muscle fibers that can continue contracting; rely on aerobic metabolism, contain moe mitochondria and myglobin.
slow fibers (red muscle)
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The amount of tension a muscle provides when contracted is based upon...
the frequency of stimulation (how many stimulations are happening); the number of motor unit involved (providing range of motion, rather than all or nothing)
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The amount of force provided by a muscle depends on...
how many motor units are activated
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Even at rest, some muscle units are active and tense even though they are not causing movement.
resting tone
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Cardiac muscle function to...
reduce the size of the chambers of the heart
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Cardiac muscle is a system of ________ and _________ similar to skeletal muscle.
sarcomeres and sarcoplasmic reticulum
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In cardiac muscle, bundles form thick _______.
myocardium
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What are 3 major differences between skeletal and cardiac muscle?
- 1. cardiac muscle cells are single cells joined together at intercalated discs; skeletal muscle cells share cytoplasm/are actually fused.
- 2. cardiac muscle cells branch; skeletal muscle cells are elongated on one axis.
- 3. cardiac muscle cells have nuclei at the center; skeletal muscle cell nuclei are pushed off to the side of the cell.
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The fact that cardiac muscle cells each beat separately without any stimulation.
inherent rhythmicity
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Intercalated discs are only present in _________ and provide...
cardiac muscle; sites of attachment for cardiac muscle cells
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Intercalated discs join cells together in order to...
allow for simultaneous contraction
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Highly modified cardiomyocytes that are part of the conduction system of the heart.
purkinje fibers
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Purkinje fibers lack ___________, and they are connected by __________ and ___________ instead of __________.
T tubules; gap junctions and desmosomes; intercalated discs
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There are 2 layers of smooth muscle in tubular organs. What are the layers and hat is their function?
- 1. Outer longitudinal layer- reduces length
- 2. Inner, circular layer- reduces diameter
Together, they move food, fluid, etc through the tubular organ
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Smooth muscle cells are _______-shaped (like fibroblasts), but unlike fibroblasts, they have...
spindle; a large amount of cytoplasm
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Smooth muscle contractions are ________ and ________, and they do not always require a ________.
slow and sustained; nervous signal
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What is the difference between smooth muscle contraction and skeletal muscle contraction?
As smooth muscle filaments contract, the entire cell shrinks in all directions; as skeletal muscle fibers contract, the muscle shorts longitudinally due to sarcomeres
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In smooth muscle contraction, calcium binds to ________, and this complex activates ___________, which phosphorylates ________ and allows it to bind to _______.
calmodulin; myosin light chain kinase (MLCK); myosin; actin
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In skeletal muscles, myosin heads bind to actin in the presence of ________, and the sarcomeres contract in...
calcium; one direction
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