Glossary of A&P Chapter 9 - Muscle Tissue
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- what are the three types of muscle tissue?
- what are the 5 functional characteristics?
- muscle excitability
- respond to chemicals released from nerve cells
- muscle conductivity
- ability to propagate electrical signals over membrande
- muscle contractility
- ability to shorten and generate force
- muscle extensibility
- ability to be stretched without damaging the tissue
- muscle elasticity
- ability to return to original shape after being stretched
- what are the 4 muscle tissue functions?
- 1. produce body movement and body heat
2. stabilizing body positions
3. regulating organ volumes
4. movement of substances within the body
- what type of tissue is skeletal muscle?
- connective tissues
- superficial fascia
- loose connective tissue and fat underlying the skin
- deef fascia
- dense irregular connective tissue around muscle
- connective tissue components of the muscle and their function
- -epimysium-surrounds the whole muscle
- perimysium - surrounds bundles of 10-100 muscle cells
- endomysium - separates individual muscle cells
- a cord of dense connective tissue that attaches a muscle to the periosteum of a bone
- a tendon that extends as a broad, flat layer
- what supplies each skeletal muscle?
- a nerve, artery and two veins
- where are nerve fibers and capillaries found?
- the endomysium between individual cells
- motor unit
- one somatic motor neuron and all the skeletal muscle cells it stimulates
- how many muscle cells does a motor neuron stimulate?
- 10-2,000 cells
- where are muscle fibers normally scattered?
- throughout the belly of muscle
- muscle cell membrane
- T (transverse) tubules
- invaginations of the sarcolemma into the center of the cell
filled with extracellular fluid
carry muscle action potentials down into cell
- lie in rows throughout cell
use ATP during contraction
- the sarcoplasm is filled with tiny threads called myofibrils, these contain what?
- myoglobin and glycogen
- red-colored, oxygen-binging protein
- what does the sarcoplasmic reticulum do and what is its function?
- separates and encircles each myofibril and functions in a relaxed muscle to store calcium ions
- the contractile unit, composed of myofilaments
- what creates the striations in skeletal muscle?
- thick and thin filaments that overlap each other in a pattern
- what is the structure of a myofibril?
- contains a sarcomere that has light I bands and Dark A bands. the I bands contain thin filaments. each sarcomere is separated by Z discs. in the overlapping region, six thin filaments surround each thick filament
- which supporting proteins help to anchor the thick and thin filaments in place?
- M line
- what three proteins build myobibrils?
- what three types of proteins build myofibrils?
- contractile proteins
- what do regulatory proteins do?
- turn contraction on and off
- what do structural proteins do?
- provide proper alignment, elasticity, and extensibility
- what are the contractile proteins?
- myosin and actin
- what are the regulatory proteins?
- Troponin (Tnl, TnT, TnC) and tropomyosin
- what are the structural proteins?
- which proteins act on thick filaments?
- myosin and actin
- which proteins act on thin filaments?
- troponin and tropomyosin
- what does myosin look like?
- two golf clubs twisted together, has myosin heads that cross bridges and extend toward the thin filaments
- what holds myosin in place?
- the M line proteins
- which proteins make up thin filaments?
- actin, troponin, tropomyosin
- what holds thin filaments in place?
- Z lines
- from one Z line to the next is a ....
- what covers the myosin- binding site on each actin molecule in relaxed muscle?
- what is troponin responsible for?
- for binding to ion and moving tropomyosin out of the way when muscle cotnracts
- what does titin do?
- anchors thick filaments to the M line and the Z disc
- how far can the portion of the molecule between the Z disc and the end of the thick filament stretch/
- to 4 times its resting length and can spring back unharmed
- which protein plays a role in recovery of the muscle from being stretched?
- what does the M line do?
- connects to titin and adjacent thick filaments
- another name for M line
- an inelastic protein that helps align the thin filaments
- what does dystrophin do?
- links thin filaments to sarcolemma and transmits the tension generated to the tendon
- what happens in the sliding filament mechanism of contraction?
- 1. myosin cross bridges and pull on thin filaments
2. thin filaments slide inward
3. Z discs come toward each other
4. sarcomeres shorten, muscle fiber shortens, muscle shortens
- how does a skeletal muscle contract?
- 1. nerve impulses reach an axon and synaptic vesicles release ACh
2. ACh diffuses to receptors on the sarcolemma and Na+ channels open and Na+ rushes into the cell
3. the inside of the muscle cell becomes more positive, triggering a muscle action potential that travels over the sarcolemma and down the T tubules
4. SR releases Ca+2 into the sarcoplasm
5. Ca+2 binds to troponin and casues troponin-tropomyosin complex to move and reveal myosin binding sites on actin--the contraction cycle beings
- contraction cycle
- repeating sequence of events that cause the thick and thin filaments to move past each other
- what are the 4 steps to contraction cycle?
- 1. ATP hydrolysis
2. Attachment of myosin to actin to form crossbridges
3. power stroke
4. detachement of myosin from actin
- how long does the contraction cycle last?
- it keeps repeating as long a there is ATP available and there is a high Ca+2 level near the filaments
- how are myosin heads activated?
- by ATP
- what do activated myosin heads attach to?
- how does skeletal muscle relaxation occur?
- -acetylcholinestrerase breaks down ACh within the synaptic cleft
-muscle action potential ceases
-Ca+2 release channels close
-active transport pumps Ca2+ back into storage in the sarcoplasmic reticulum
-calcium -binding protein (calsequestrin) helps hold Ca+2 in SR
-Tropomyosin-troponin complex recovers binding site on the actin
- what are the 4 parts of a twitch contraction?
- latent period
- how long is the latent period of a twitch contraction?
- 2 msec
- what is happening during the latent period
- Ca+2 is being released from SR and slack is being removed from elastic components
- what is happening during the contraction period?
- filaments slide past each other
- how long is the contraction period?
- 10-100 msec
- how long is the relaxation period?
- what is happening during the relaxation period?
- active transport of Ca+2 into SR
- how long is the refractory period?
- 5 msec for skeletal muscle and 300 msec for cardiac muscle
- what is happening during the refractory period?
- muscle can not respond and has lost its excitability
- unfused tetanus
- if stimulate is at 20-30 times/sec
there will be only partial relaxation between stimuli
- fused tetanus
- if stimulate is at 80-100 times/second
a sustained contraction with no relaxation between stimuli will result
- what causes wave summation and both types of tetanus?
- Ca+2 remaining in the sarcoplasm
- why is a force of second contraction easily added to the first?
- because the elastic elements remain partially contracted and do not delay the beginning of the next contraction
- what are the features of muscle tone?
- keeps muscle firm even though relaxed
does not produce movement
- what is muscle tone used for?
- essential for maintaining posture (head upright) and important in maintaining blood pressure -tone of smooth muscles in walls of blood vessels
- muscle tone
- involuntary contraction of a small number of motor units - alternately active and inactive in a constantly shifting pattern
- isotonic contractions
- contractions where a load is moved
2 types - concentric and eccentric
- concentric contraction
- a muscle shortens and does work -ex. picking up a book or kicking a ball
- eccentric contractions
- a muscle contracts as it lengthens
-ex. walking up a steep hill
- isometric contraction
- no movement occurs because the muscle neither shortens nor lengthens, builds to its peak tension-producing capacity
-ex. maintaining upright posture or hold joints in stationary position - sitting in a chair, squats
- when does muscle use ATP the most?
- when active
- how long does sarcoplasmic ATP last?
- a few seconds
- what are the 3 sources of ATP production within muscle?
- creatine phosphate
anaerobic cellular respiration
aerobic cellular respiration (better for muscle)
- how is creatine phosphate formed?
- excess ATP within resting muscles is used to form it
- which is more plentiful within muscle when resting? ATP or creatine phosphate? by how much?
- creatine phosphate is 3-6 times more plentiful
- how long is maximal contraction of muscles using creatine phosphate ?
- 15 seconds - used for 100 meter dash
- what happens to those athletes that tried creatine supplementation?
- they gain muscle mass but they shut down the bodies own synthesis because the body says they already have high level of creatine from the supplement so there is no reason to produce more, so it shuts off.
- anaerobic cellular respiration
- ATP is produced from glucose breakdown into pyruvic acid during glycolysis
- what happens if there is no O2 present in anaerobic cellular respiration?
- pyruvic acid is converted to actic acid which diffuses into the blood
- how long can glycolysis continue anaerobically to provide ATP?
- 30-40 seconds of maximal activity - 200 meter race
- what type of cellular respiration occurs for activity lasting over 30 seconds?
- aerobic cellular respiration
if sufficient oxygen is available, pyruvic acid enters the mitochondria to generate ATP, water and heat
fatty acids and amino acids can also be used by the mitochondria
- how much of the ATP energy is provided by aerobic cellular respiration if activity lasts more than 10 minutes?
- 90% of ATP energy
- what is muscle fatigue?
- the inability to contract after prolonged activity
- what are the factors that contribute to fatigue?
- -central fatigue - feeling of tiredness and a desire to stop
-insufficient release of ach from motor neurons
-depletion of creatine phosphate
-decline of Ca+2 within the sarcoplasm
-insufficient oxygen or glycogen
-buildup of lactic acid and ADP
- what happens as a muscle is stretched past optimal length?
- fewer cross bridges exist and less force is produced
- what does the optimal overlap of thick and thin filaments produce?
- the greatest number of cross bridges and the greatest amount of tension
- what happens if muscle is overly shortened- less than optimal?
- fewer cross bridges exist and less force is produced
thick filaments are crumpled by Z discs
- what are the red muscle fibers?
- myoglobin, mitochondria and capillaries
- what makes white muscle fibers
- less myoglobin and less capillaries giving fibers their pale color
- what causes the variation in contraction and relaxation speeds?
- how fast myosin ATPase hydrolyzes ATP
- what do slow oxidative or slow twitch muscle fibers look like? what is their function and where are they found?
- -red in color
-prolonged, sustained contraction for maintaining posture
-found in neck, back and leg muscles
- what do oxidative- glycolytic or fast -twitch A muscle fibers look like? and what is their function? what are they used for?
- -red in color
-they split ATP at very fat rate
-used for walking and sprinting
- what do fast glycolytic or fast-twitch B muscle fibers look like? what is their function? where are they found?
- -white in color
-anaerobic movements for short duration - used in weight lifting
-found in shoulder and arm muscles
- why are fast twitch muscle fibers longer?
- they need more myoglobin
- what do anabolic steroids do?
- increases muscle size, strength and endurance
- what are the side effects of anabolic steroids?
- liver cancer
facial hair and voice deepening in females
atrophy of testicles and baldness in males
- what are anabolic steroids most similar to?
- what are the two types of smooth muscle?
- visceral - single unit and multiunit
- where is visceral smooth muscle found?
- int he walls of hollow viscera and small BV
- what do the gap junctions of visceral muscle serve to do?
- cause fibers to contract in unison
- multiunit smooth muscle
- individual fibers with their own motor neuron ending
- where is multiunit smooth muscle found?
- large arteries, large airways, arrector pili muscles, iris, ciliary body
- what does smooth muscle look like?
- small involuntary muscle cells tapering at the ends, single oval, centrally located nucleus, and lack T tubules and have little SR for Ca+2 storage
- how do smooth muscle fibers contract? relax?
- by twisting motion into a helix as it shortens and relaxes by untwisting
- what is the regulator protein that binds calcium ions in the cytosol of smooth muscle?
- calmodulin - it takes the place of troponin in striated muscle
- what is calmodulins role in smooth muscle?
- it activates the enzyme myosin light chain kinase, which facilitates myosin-actin binding and allows contraction to occur in a relatively slow rate
- describe the regeneration of skeletal muscle fibers?
- they cannot divide after 1 year
their growth is from enlargement of existing cells and through repair satellite cells and bone marrow produce some new cells. if there is not enough numbers - fibrosis occurs most often
- describe the regeneration of muscle fibers
- they cannot regenerate or divide. all healing is done by fibrosis - scar formation
- describe smooth muscle regeneration
- regeneration is possible
the cells can grow in size -hypertrophy. some cells like the uterus can divide - hyperplasia. new fibers can form from stem cells in BV walls
- involuntary contraction of single muscle
- a painful spasm
- involuntary twitching of muscles normally under voluntary control - eyelide or facial muscles
- rhythmic, involuntary contraction of opposing muscle groups
- involuntary, brief twitch of a motor unit visible under the skin
- muscle atrophy
- wasting away of muscles
- what causes muscle atrophy?
- disuse (disuse atrophy) or severing of the nerve supply (denervation atrophy)
- what happens in muscle atrophy?
- the transition to connective tissue can not be reversed
- increase in the diameter of muscle fibers
- what causes muscle hypertrophy?
- very forceful, repetitive muscular activity and an increase in myofibrils, SR and mitochondria
- rigor mortis
- state of muscular rigity that begins 3-4 hrs after death and lasts about 24 hrs
- what causes rigor mortis?
- after death, Ca+2 ions leak out of the SR and allow myosin heads to bind to actin. since ATP synthesis has ceased, crossbridges cannot detach from actin until proteolytic enzymes begin to digest the decomposing cells
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