Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
59 Cards in this Set
- Front
- Back
Muscle Tissue |
A primary tissue type, divided into; -skeletal muscle -Cardiac muscle -Smooth muscle |
|
Skeletal muscles |
-are attached to the skeletal system -allow us to move -The muscular system |
|
The muscular system |
-includes only skeletal muscles |
|
Functions of skeletal muscles |
-produce skeletal movement -maintain body position -support soft tissues -guard openings -maintain body temp. -store nutrient reserves |
|
Skeletal muscle structures |
-muscle tissue(muscle cells or fibers) -connective tissues -nerves -blood vessels |
|
Muscles have three layers of connective tissues |
-epimysium -perimysium -endomysium |
|
Epimysium |
–exterior collagen layer –connected to deep fascia –Separates muscle from surroundingtissues |
|
Perimysium |
–surrounds muscle fiber bundles(fascicles)
–contains blood vessel and nervesupply to fascicles |
|
Endomysium |
–surrounds individual muscle cells(muscle fibers)
–contains capillaries and nervefibers contacting muscle cells –contains myosatellite cells (stem cells) that repairdamage |
|
Muscle attachments -endomysium, perimysium, and epimysium come together: |
-at ends of muscles
-to form connective tissue attachment to bone matrix -i.e, tendon(bundle) or aponeurosis(sheet) |
|
Nerves |
-skeletal muscles are voluntary muscles, controlled by nerves of the central nervous system( brain and spinal cord) |
|
Blood Vessels |
Muscles have extensive vascular systems that -supply large amounts of oxygen -supply nutrients -Carry away wastes |
|
Skeletal Muscle Fibers |
-are very long -develop through fusion of mesodermal cells(myoblasts) -become very large -contain hundreds of nuclei |
|
The sarcolemma |
-The cell membrane of a muscle fiber(cell) -Surrounds the sarcoplasm( cytoplasm of muscle fiber) -A change in transmembrane potential begins contractions. |
|
Transverse tubules (T tubules) |
-transmit action potential through cell -allow entire muscle fiber to contract simultaneously -have the same properties as sarcolemma |
|
Myofibrils |
-lengthwise subdivisions within muscle fiber -made up of bundles of protein filaments(myofilaments) -Myofilaments are responsible for muscle contraction -Types of myofilaments: -thin filaments -thick filaments |
|
Thin filaments
|
-made of the protein actin |
|
Thick filaments |
-made of the protein myosin |
|
sarcoplasmic reticulum(SR) |
-a membranous structure surrounding each myofibril -helps transmit action potential to myofibril -similar in structure to smooth endoplasmic reticulum -forms chambers(terminal cisternae) attached to T tubules |
|
Triad |
-is formed by one T tubule and two terminal cistern -Cisternae: -concentrate Ca2+(via ion pumps) -release Ca2+ into sarcomeres to begin muscle contraction |
|
Sarcomeres |
-the contractile units of muscle -structural units of myofibrils -form visible patterns within myofibrils |
|
Muscle striations |
-a striped or striated pattern within myofibrils: -alternating dark, thick filaments( A bands) and light, thin filaments( I bands) |
|
Sacromeres |
-M lines and Z lines |
|
M line |
-the center of the A band -at midline of sacromere |
|
Z lines |
-the centers of the i bands -at two ends of sarcomere |
|
Sacromeres |
-zone of overlap -the H Band |
|
Zone of overlap |
-the densest, darkest area on a light micrograph -where thick and thin filaments overlap |
|
The H Band |
-the area around the M line -has thick filaments but no thin filaments |
|
Sarcomeres -Titin |
-are strands of protein -reach from tips of thick filaments to the z line -stabilize the filaments |
|
Sarcomere Funcion |
-transverse tubules encircle the sarcomere near zones of overlap -Ca2+ released by SR causes thin and thick filaments to interact |
|
Muscle contraction |
-is caused by interactions of thick and thin filaments -structures of protein molecules determine interactions |
|
Four thin filament proteins |
-F-actin(Filamentous actin) -Nebulin -tropomyosin -troponin |
|
F-actin(Filamentous actin) |
-is two twisted rows of globular G-actin -the active sites on G-actin strands bind to myosin |
|
Nebulin |
- Holds F-actin strands together |
|
Tropomyosin |
-is a double strand -prevents actin-myosin interaction |
|
Troponin |
-A globular protein -binds tropomyosin to G-actin -Controlled by Ca2+ |
|
Initiaing Contraction |
-Ca2+ binds to receptor on troponin molecule -Troponin-tropomyosin complex changes -exposes active sit of F-actin |
|
Thick filaments |
-contain twisted myosin subunits -contain titin strands that recoil after stretching -the myosin molecule -tail -head |
|
The myosin molecule: -Tail |
-binds to other myosin molecules |
|
The myosin molecule: -Head |
-made of two globular protein subunits -reaches the nearest thin filament |
|
Myosin Action |
-During contraction, myosin heads: - Interact with actin filaments, forming cross-bridges -Pivot, producing motion |
|
Sliding filament theory |
-thin filaments of sarcomere slide toward M line, alongside thick filaments -the width of A zone stays the same -Z lines move closer together |
|
The process of contraction |
-neutral stimulation of sarcolemma -cisternae of SR release Ca2+ |
|
Neutral stimulation of sarcolemma |
-causes excitation-contraction coupling |
|
Cistern of SR release Ca2+ |
-which triggers interaction of thick and thin filaments -consuming ATP and producing tension |
|
The neuromuscular junction |
-is the location of neural stimulation -action potential (electrical signal) |
|
Action potential (electrical signal) |
-travels along nerve axon -ends at synaptic terminal |
|
Synaptic terminal |
-realeases neurotransmitter(acetylcholine or ACh) -into the synaptic cleft (gap between synaptic terminal and motor en plate) |
|
The Neurotransmitter: - Acetylcholine or ACh |
-travels across the synaptic cleft -binds to membrane receptors on sarcolemma (motor end plate) -causes sodium-ion rush into sarcoplasm -is quickly broken down by enzyme (acetylcholinesterase or AChE) |
|
Action potential |
-generated by increase in sodium ions in sarcolemma -travels along the T tubules -leads to excitation-contraction coupling |
|
Excitation- contraction coupling |
-action potential reaches a triad: -realeasing Ca2+ -triggering contraction -requires myosin heads to be in "cocked" position: -loaded by ATP energy |
|
Five steps of the contraction cycle |
-exposure of active sites -formation of cross-bridges -pivoting of myosin heads -detachment of cross-bridges -reactivation of myosin |
|
Fiber Shortening |
-as sacromeres shorten, muscle pulls together, producing tension |
|
Contraction Duration |
-depends on: -duration of neural stimulus -number of free calcium ions in sarcoplasm -availability of ATP |
|
Relaxation |
-Ca2+ concentrations fall -Ca2+ detaches from troponin -active sites are re-covered by tropomyosin -sarcomeres remain contracted |
|
Rigor Mortis |
-a fixed muscular contraction after death -cause when: -ion pumps cease to function; ran out of ATP -calcium builds up in the sarcoplasm |
|
The Contraction Cycle |
-Skeletal muscle fibers shorten as thin filaments slide between thick filaments -Free Ca2+ in the sarcoplasm triggers contraction -SR releases Ca2+ when a motor neuron stimulates the muscle fiber -Contraction is an active process -Relaxation and return to resting length are passive |
|
The all-or-none principle |
-as a whole, a muscle fiber either contracted or relaxed |
|
Tension of a single muscle fiber |
-Depends on: -the number of pivoting cross-bridges -the fibers resting length at the time of stimulation -the frequency of stimulation |