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HA. Ch. 9
Muscular System I: Skeletal Muscle Tissue and Muscle Organization
| Question | Answer |
|---|---|
| 3 types of muscle tissue | skeletal, cardiac, smooth |
| skeletal muscle attaches to | skeleton |
| skeletal muscles have...very...and... | single...long...cylindrical striated cells |
| skeletal muscle | multinucleate (peripherally located) |
| skeletal muscle can be controlled | voluntarily |
| cardiac muscle occurs in the | heart wall |
| cardiac muscle has branching chains of | striated cells |
| cardiac muscle has one | nucleus per cell; some can be binucleate |
| intercalated discs of cardiac muscle contain | several types of cell junctions |
| cardiac cells are | electrically coupled by gap junctions |
| cardiac muscles are controlled | involuntarily |
| smooth muscle occurs chiefly in | walls of hollow organs |
| smooth muscle has what type of cells | single, fusiform nonstriated cells |
| smooth muscle cells are | uninucleate |
| smooth muscle is controlled | involutnarily |
| 3 types of tissues share | 4 specialized properties |
| 4 specialized properties | excitability, contractility, elasticity, extensibility |
| excitability is the ability of a muslce cell to respond to | nerve signals or other stimuli, causing electrical impulses to travel along the muscle plasma membrane |
| contractility is the ability to generate a strong | pulling force while muscle cells shorten or contract |
| elasticity is the ability of a muscle after being stretched, to | recoil passively to its original or resting length |
| extensibility is the ability to continue to | contract over a range of resting lengths |
| skeletal muscle tissue produces | movement |
| skeletal muscle tissue maintains | posture and body position |
| skeletal muscle tissue supports | soft tissue |
| skeletal muscle tissue regulates | entrance and exit of materials |
| skeletal muscle tissue generates | heat through muscle contractions to maintain body temperature |
| skeletal muscle tissue stabilizes | joints |
| skeletal muscles is surrounded by...and is comprised of | epimysium...bundles of muscle fascicles |
| muscle fascicle is a group or bundle of | muscle fibers surrounded by a perimysium |
| muscle fiber (myofiber or muscle cells) | a highly elongated cell comprised of myofibrils surrounded by endomysium |
| sarcolemma (skeletal) | plasma membrane of muscle fiber which is comprised of abundant myofibrils |
| sarcoplasm | cytoplasm of muscle fiber which contains numerous myofibirls |
| myofibril is a cylindrical structure which is as | long as the entire cell and consists of sarcomeres; surrounded by sarcoplasmic reticulum |
| myofibrils can...and are | shorten...responsible for contraction of the skeletal muscles fiber |
| myofibril contraction leads to | shortening the entire cell bec. a myofibiril is attached to the sarcolemma at each end of the cell |
| sarcoplasmic reticulum (SR) | internal membrane complex that is similar to the SER of other cells |
| the SR is closely associated with | the transverse tubules (T) |
| SR plays important role in | controlling the contraction of individual myofibrils via the release of calcium ions |
| transverse (T) tubules | deep invaginations of the sarcolemma which allow electrical impulses to quickly travel to the interior of the cell |
| terminal cisternae | expanded chambers on either side of a transverse tubule where the tubule of the SR has enlarged and fused |
| triad | combination of a pair of terminal cisternae plus a transverse tubule |
| sarcomere | myofibrils consist of sarcomeres, which are repeating units of myofilaments; smallest functional units of muscle fibers |
| myofilaments | sarcoplasm of muscle contains protein filaments, which generate contractile force |
| myofilaments determine the | striation pattern in skeletal muscle fibers |
| myofilaments fill most of the | sarcoplasm of each musle fiber (cytoplasm) |
| myofilaments are organized in the | repeating units called sarcomeres |
| 2 primary types of myofilaments in muscle cells | actin and myosin |
| actin | protein filaments found in thin filaments |
| myosin | protein filaments found in thick filaments |
| the striated apperance of skeletal muscle tissue arises from the | organization of the thick and thin filaments within the myofibrils of the sarcomere |
| myofibrils are arranged | parallel to the long axis of teh cell, with their sarcomeres arranged side to side |
| myofibrils of the sacromere give the apperance of | distinct dark and light bands (striations correspond to these bands of the individual sarcomeres) |
| m line | group of proteins which link the thick filaments that lie in the center of the sarcomere |
| z lines or z discs are open | meschworks of interconnecting proteins called actinins, which occur where thin filaments from adjacent sarcomeres join |
| thin filaments are attached to the | z lilne and extend toward the m line |
| zone of overlap | area where the thin filaments pass between the thick filaments |
| in a 3-D cross-sectional view each thin filament is surrounded by | 3 thick filaments arranged in a triangle, while 6 thin filaments surround each thick filament |
| a band | area containing thick filaments, including the m line, the h band, and the zone of overlap; appears as a "dark band" |
| h band is the area | containing thick filaments only |
| i band | the area containing thin filaments only, appears as a "light band" |
| during contraction, the z lines/discs move | closer together, and the I bands and H bands shorten |
| memory aid | A bands are dArk, I bands are lIght (anisotropic characteristics and isotropic characteristics respectively) |
| thin filaments | F actin, nebulin, G actin, tropomyosin, troponin |
| F actin | strand of 300-400 globular G actin molecules |
| nebulin | slender strand of proteins that holds the F actin strand together |
| G actin molecules contains an | active site that can bind to a thick filament, in the same manner that a substrate molecule binds to an enzyme's active site |
| tropomyosin: protein molecules that | form a long chain, which covers the active sites, preventing actin-myosin interaction |
| troponin | protein molecules that hold the tropomyosin strand in place |
| troponin changes position to | move the tropomyosin molecule, exposing the active site prior to a muscle contraction |
| troponin acts as the | regulator molecule of a muscle contraction |
| thick filaments | myosin, proteins of M line, cross bridges, titin |
| approximately how many myosin molecules comprise the thick filament? | 500 |
| each myosin molecule consists of a | double myosin strand with an attached, elongate tail and a free globular head |
| proteions of the m line interconnect | adjacent thick filaments, midway along their length |
| myosin heads are also known as | cross-bridges bec they connect thick filaments and thin filaments during a muscle contraction |
| myosin heads project | outward toward the surrounding thin filaments, as the entire myosin molecules are oriented away from the M line |
| titin | protein molecule that makes up the core of each thick filament |
| a strand of titin extends the | length of the filament and attaches the M line to the Z line |
| an exposed portion within the I band is | highly elastic and will recoil after stretching |
| titin is completely | relaxed in the normal resting sarcomere |
| titin becomes tense only | when some external force stretches the sarcomere |
| when sarcomere of titin is stretched the titin strands help | maintain the normal alignment of the thick and thin filaments |
| when the stretching force is removed, titin fibers help | return the sarcomere to its normal resting length |
| shapes of skeletal muscle | spindle-shaped cylinders, triangles, sheets |
| each skeletal muscle is an...and contains | organ...tissue elements, blood vessels and nerves, as well as being comprised mostly of muscle fiberss |
| organization levels in a skeletal muscle | whole muscle - fascicle - fiber - myofibril - sarcomere - myofilament (actin and myosin) |
| connective tissue elements | epimysium, perimysium, endomysium |
| epimysium | DICT sheath wrapped around a whole muscle |
| perimysium | fibrous CT sheath around a fascicle |
| endomysium | thin reticular fiber CT sheath around each muscle fiber |
| every skeletal muscle fiber is | innervated and stimulated by a nerve cell to contract |
| every skeletal muscle fiber has a | rich blood supply and has fine nerve fibers and capillaries in the endomysium |
| origin of skeletal muscle | immovable attachment from which a muscle extends |
| insertion of skeletal muscle | more movable attachment |
| skeletal muscles attach to bones through | tendons, aponeuroses or direct attachments |
| skeletal muscle contraction exerts a | pull, or tension, and shortens the muscle fiber in length |
| the skeletal muscles attach to the | skeleton in a way that keeps them at a near-optimal length for generating maximum contractile forces |
| muscle contraction is accurate for | muscles involved in activities such as walking where the muscles contract and relax repeatedly |
| muscle fibers(skeletal) are stretched to | near optinmal length before stimulation of contraction occurs |
| the presence of | calcium ions is the trigger for a contraction in skeletal muscle |
| the presence of | ATP is required for the contraction to occur |
| sliding filament theory or mechanism explains the | physical changes that occur between the thin and thick filaments during muscle contraction |
| the h band and i band get...with the sliding filament theory | smaller |
| the zone of overlap gets...with sliding filament theory | larger |
| the z lines move...with sliding filament theory | closer |
| the width of the a band ...during sliding filament theory | remains constant throughout the contraction |
| mechanism steps of the sliding filament theory 1) | myosin heads of thick filaments bind to active sites on thin filaments, causing sliding to occur |
| step 2) | cross-bridge binding; myosin head pivots toward the m line, pulling the thin filament toward the center of the sarcomere |
| step 3) | cross bridge then detaches and returns to irs original position and is ready for the next cycle of "bind, pivot, detach, return" regarding its original position |
| step 4) | z lines move toward the m line when the thick filaments pull on the thin filaments, causing the sarcomere to shorten |
| when a nerve cell stimulates a muscle fiber, it sets up an | impulse in the sarcolemma that signals the sarcoplasmic reticulum to release calcium ions |
| the release of calcium ions then initiates the | sliding of the myofilaments (translates to muscle contraction) |
| motor neurons innervate individual skeletal muscle fibers at | neuromuscular synapses or junctions (motor end plates) |
| neuromuscular synapse is a specific synapse between | a motor neuron and a muscle cell |
| synaptic terminal is the expanded tip of the | motor neuron's axon, at the neuromuscular synapse |
| synaptic vesicles are small | secretory vesicles in the cytoplasm of the synaptic terminal |
| synaptic vesicles contain | acetylcholine |
| neurotransmitter is a | chemical released by a neuron to communicate with another cell |
| acetylcholine is a (ACh) | neurotransmitter that signals the muscle cell to contract; released at the axon terminal |
| synaptic cleft is a narrow space that seperates | the synaptic terminal from the motor end plate of the skeletal muscle fiber |
| acetylcolinesterase or cholinesterase | is an enzyme which breaks down ACh molecules and is released into the synaptic cleft |
| an electrical impulse arrives at the | synaptic terminal |
| ACh is released and | binds to receptor sites on motor end plate |
| a change in local transmembrane potential occurs and results in | generation of an electrical impulse, or action potential |
| electrical impulse travels | all over the surface of the sarcolemma and into each T tubule |
| action potential's continue to be | generated until AChE removes the bound ACh |
| immediately after ACh signals a single contraction it is | broken down by AChE |
| each muscle fiber must be | served by a neuromuscular junction |
| motor unit consits of one | motor neuron and all the skeletal muscle fibers it innervates(controls) |
| motor units contain different | numbers of muscle fibers distributed widely within a muscle |
| the size of a motor unit indicates | the level of control of the movement |
| a motor neuron that controls 2 or 3 muscle fibers (eye) has more | precise control of muscle movement than a motor neuron that innervates up to 2000 muscle fibers (leg) |
| muscle twitches contain different | numbers of muscle fibers distributed widely within a muscle |
| all-or-none principle states that a characteristic in which each muscle fiber | either contracts completely or not at all |
| all or none principle says that all muscle fibers in a motor unit | contract simultaneously |
| all or none principle says that the amount of force, exerted by the muscle as a whole, depends on | how many motor units are activated |
| recruitment is the smooth, but | steady incrase in muscular tension that is produced by increasing the number of motor units that are activated |
| muscle tone is teh | resting tension in a skeletal muscle |
| in a resting muscle, some | motor units are always active w/o producing enough tension to cause movement, but the activity tenses the muscle |
| intermediate fibers contract | quickly |
| fast glycolytic fibers or white fibers are .... fibers bec.... | white...contain little myoglobin |
| few...are in white fibers...but there are | mitochondria or capillaries...abundant glycosomes that contain glycogen as a fuel source |
| white fibers contract...fatigue | rapidly...quickly |
| levers are | rigid bars or structures that move on a fixed point |
| fixed point is called | fulcrum |
| when effort is applied to the lever | a load is moved |
| a motor neuron that controls two or three muscle fibers (eye) has more...control of muscle movement than a motor neuron that.. | precise...innervates up to 2000 muscle fibers (leg) |
| muscle twitch | a single, momentary contraction, which is a response to a single stimuli |
| muscle twitches contain different | numbers of muscle fibers distributed widely within a muscle |
| all or none principle says that a characteristic in each muscle fiber either | contracts completely or not at all |
| all or none princple says that all muscle fibers | in a motor unit contract simultaneously |
| all or none principle says that the amount of force exerted by the muscle as a whole depends on | how many motor units are activated |
| recruitment is the smooth, but | steady, increase in muscular tension that is produced by increasing the number of motor untis that is activated |
| muscle tone | the resting tension in a skeletal muscle |
| muscle tone in a resting muscle, some motor units are | always active without producing enough tension to cause movement, but the activity tenses the muscles |
| muscle tone stabilizes the | position of bones and joints |
| muscle spindles are specialized muscle cells that are monitored by | sensory nerves, which control the muscle tone in the surrounding muscle tissue |
| muscle hypertrophy is the enlargment of | skeletal muscles that undergo excessive repeated stimulation that produces near maximal tension |
| muscle atrophy is reduction in | skeletal muscle size, tone, and power, as a result of inadequate stimulation to maintain resting muscle tone in the affected area |
| types of skeletal muscle fibers | slow oxidative (red I), intermediate (fast oxidative, IIa),fast glycolytic fibers (white, type IIx) |
| red fibers are relatively | thin fibers which are red becasue of their abundant myoglobin |
| red fibers obtain energy from | aerobic metabolic reactions |
| red fibers contract...extremely... | slowly...resistant to fatigue as long as enough oxygen is present |
| red fibers deliver | prolonged contractions |
| red fibers are best for | maintaining postures |
| inter. fibers contract | quickly |
| inter. fibers are...dependent and have a high... | oxygen...myoglobin content and have abundant mitochondria and a rich capillary supply |
| inter. fibers are fatigue | resistant but less so than type I |
| inter. fibers are...in many of their characteristrics compared to types I and IIx | intermediate |
| inter. fibers are best for | long term production of fairly strong contractions such as required locomotion of the lower limbs |
| white fibers are...fibers because... | pale...they contain little myoglobin |
| white fibers are about | twice the diameter or type I fibers |
| white fibers contain more | myofilaments |
| white fibers generate much more | power |
| white fibers depend on | anearobic patheways to make ATP |
| few...are present in white fibers but there are... | mitochondria or capillaries...abundant glycosomes that contain glycogen as a fuel source |
| white fibers contract | rapidly and fatigue quickly |
| white fibers are best for | short burts of power, such as required in lifting heavy objects for brief periods |
| lever is a rigid | bar/structure that moves on a fixed point |
| fixed point | fulcrum |
| when effor is applied to the lever | a load is moved |
| in the human body | bones = levers, joint = fulcrum, effort is exerted by skeletal muscles pulling on their insertions |
| 1st class levers (effort-fulcrum-load) may operate at a | mechanical advantage or disadvantage |
| 2nd class levers (fulcrum-load-effort) all work at a | mechanical advantage |
| 3rd class levers (fulcrum-effort-load) all work at a | mechanical disadvantage |
| most muscles of the body are in | 3rd class lever systems to provide speed of movement |
| mechanicnal advanctage allows | slow and strong movements |
| mechanical disadvantage allows muscles to | move quickly and far but takes extra effort |
| fascicle = | bundle of muscle fibers |
| parallel muscle | long axes of the fascicles are parallel to the long axis of the muscle, and the muscle extends from origin to insertion |
| most of the skeletal muscles in the body are | parallel muscles |
| parallel muscles have a | central body, or belly/gaster |
| example of parallel muscle | biceps brachii |
| convergent muscle | origin is broad, and the fascicles converge toward the tendon of insertion, its common attachment site |
| convergent muscle fibers may pull on a | tendon, or tendinous sheet, or a slender band of collagen fibers known as a raphe |
| example of convergent muscle | pecoralis major of anterior chest |
| circular muscle (sphincter) | fascicles are arranged in concentric rings around an opening or recess |
| in a circular muscle, when the muscle contracts, the diameter | of the opening decreases |
| example of circular muschle | orbicularis oris |
| pennate muscle (penna -feather) the fascicles are | short and attach at an oblique angle to a tendon that runs through the body of the muscle |
| unipennate | fascicles insert into one side of the tendon |
| example of unipennate | extensor digitorum longus muscle |
| bipennate | fascicles insert into both sides of the tendon |
| example of bipennate | rectus femoris muscle of thigh |
| multipennate | fascicles insert into a tendon that branches within the muscle |
| arrangement of multipennate muscles look like many | feathers situated side by side, whose quills are all inserted into one tendon |
| example of multipennate | deltoid muscle of shoulder |
| skeletal muscles are arranged in | opposing groups across movalbe joints, allowing one group of muscles to reverse or modify the action of the opposing group |
| agonist (prime mover) | muscle whose contraction bears the main responsibility for a particular movement |
| example of agonist | biceps brachii for forearm flexion of the elbow |
| antagonist | groups of muscles whose actions oppose that of the corresponding agonist |
| example of antagonist | triceps brachii during forearm flexion but they also act as antagonist by extending the forearm |
| synergists aid the | agonists either by adding a little extra force to the same movement or by reducing undesirable extra movements that the agonist may produce |
| synergists stabilize | joints as fixators |
| naming skeletal muscles | location, shape, relative size, direction of fascicles, location of attachments, number of origins, action |
| brachialis muscle | arm |
| intercostal muscles | between ribs |
| externus or supericialis | describe muscles that are visible at the body surface |
| internus/profundus | describe muscles lying beneath the body surface |
| extrinsic | superficial muscles that position/stabilize organs |
| intrinsic | deep muscles that function within the organ |
| trapezius | trapezoidal shape |
| deltoid | triangular |
| rhomboideus | rhomboid |
| orbicularis | circle |
| magnus/major/maximus vs | minor/minimus |
| longus (long)/longissimus vs | brevis |
| teres | long and round |
| rectus | straight |
| transervsus | fascicles lie at right angles |
| oblique | fascicles lie at oblique angles |
| origin is always | named first |
| biceps, triceps, quadriceps | 2, 3, 4 |
| flexor vs | extensor |
| abductor vs | adductor |
| exceptions | platysma and diaphragm |
Created by:
handrzej
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