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110 Cards in this Set

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Name the 3 types of muscle tissue and whether they are (striated/non-striated) and (voluntary/involuntary).
Skeletal (striated, voluntary). Cardiac (striated, involuntary). Smooth (nonstriated, involuntary).
The heart has a pacemaker that initiates each contraction. This built-in rhythm is termed ___.
Autorhythmicity
What are the 4 functions of muscular tissue?
1) Produce body movements. 2) Stabilize posture 3) Store/move substances within body. 4) Generate heat.
Storage in the body is accomplished by sustained contractions of ringlike bands of smooth mm. called ___ which prevent outflow of contents of a hollow organ.
Sphincter
Process where heat is produced by muscular contraction.
Thermogenesis
What are 4 special properties of muscular tissue?
1) Electrical excitability 2) Contractility 3) Extensibility 4) Elasticity
What are the 2 main types of stimuli that trigger action potentials in muscle cells?
1) Autorhythmic electrical signals from mm. Itself. 2) Chemical neurotransmitters, hormones, etc. from other sources.
A muscle cell is also known as a ___.
Muscle fiber
Connective tissue layer separating muscle from skin, composed of areolar + adipose connective tissue.
Subcutaneous layer (or hypodermis)
Broad band of dense irregular connective tissue that lines the body wall and limbs, supports, surrounds muscles and other organs.
Fascia
Outermost layer of dense irregular connective tissue encircling entire muscle.
Epimysium
Layer of dense irregular connective tissue surrounding groups of 10-100+ muscle fibers, separating them into bundles called ___.
Perimysium. Fascicles.
Thin layer of areolar connective tissue separating individual muscle fibers from one another.
Endomysium
Cord of dense regular connective tissue composed of parallel bundles of collagen fibers that attach a muscle to the periosteum of bone.
Tendon
What 3 connective tissue layers form a tendon?
Epimysium, perimysium, endomysium
Tendon extending as a broad, flat layer.
Aponeurosis
Tubes of fibrous connective tissue that enclose certain tendons. Consists of a visceral + parietal layer, synovial fluid. Reduce friction.
Tendon (synovial) sheath
Neurons that stimulate skeletal muscle contractions are called ___.
Somatic motor neurons
Muscles are well supplied with nerves & blood vessels. Capillaries bring in ___, ___ and remove ___, ___ from muscle metabolism.
Capillaries bring in oxygen, nutrients & remove heat and waste.
Why are muscle fibers multinucleated?
Because muscle fibers are derived from the fusion of many myoblasts during embryonic development.
Enlargement of existing muscle fibers that occurs after birth.
Hypertrophy
Increase in number of muscle fibers.
Hyperplasia
Small number of myoblasts found in mature skeletal muscle are known as ___. Can fuse with one another or with damaged muscle fibers for repair.
Satellite cells
Process of replacement of muscle fibers by fibrous scar tissue.
Fibrosis
Plasma membrane of a muscle cell
Sarcolemma
Invaginations of sarcolemma that tunnel from surface to center of muscle fiber filled with interstitial fluid.
Transverse tubule
How do transverse tubules affect action potentials within a muscle fiber?
Action potentials travel along sarcolemma through T tubules, quickly spreading throughout muscle fiber. T tubules ensure that action potential excites all parts of muscle fiber at same time.
Cytoplasm of muscle fiber.
Sarcoplasm
What organic compound is largely found in the sarcoplasm for ATP synthesis?
Glycogen
Red-colored protein found only in muscle that binds oxygen diffused into muscle fiber from interstitial fluid. It releases oxygen when needed by mitochondria for ATP production.
Myoglobin
Contractile organelles of skeletal muscle.
Myofibril
Fluid-filled sacs encircling each myofibril (similar to smooth ER) that stores Ca2+ ions which trigger muscle contraction.
Sarcoplasmic reticulum
Area of sarcoplasmic reticulum that touches transverse tubule from both sides.
Terminal cisterns
What 3 structures form the triad?
1 transverse tubule, 2 terminal cisterns
Condition of muscles wasting away.
Muscular atrophy
Basic functional unit of a myofibril composed of thick and thin filaments.
Sarcomere
Region in center of H zone of sarcomere that contains proteins that hold the thick filaments together at center of sarcomere.
M line
Narrow region in center of A band of sarcomere that contains thick filaments but no thin filaments.
H zone
Lighter, less dense area of sarcomere that contains thin filaments but no thick filaments. A Z disc passes through the center of this band.
I band
Dark, middle part of sarcomere that extends entire length of thick filament and includes zone of overlap with thin filaments.
A band
Narrow region of dense material that separates 1 sarcomere from the next.
Z discs
What are the 3 classes of proteins that build myofibrils and what 2 proteins fall in each category?
Contractile (generate force) - actin/myosin. Regulatory (switch contraction on/off) - troponin/tropomyosin. Structural (align filaments, provide elasticity/extensibility, link myofibrils to sarcolemma) - titin/dystrophin.
Contractile protein that makes up thick filament. Consists of tail and 2 heads that bind to actin thin filament during muscle contraction.
Myosin
Contractile protein that makes up thin filament. Contains a binding site for myosin head of thick filament during contraction.
Actin
Regulatory protein that is component of thin filament. When skeletal muscle is relaxed, it covers the binding site on actin filament and prevents myosin from binding to actin.
Tropomyosin
Regulatory protein that is component of thin filament. When calcium ions bind to this protein, it changes shape and moves tropomyosin away from binding site on actin molecules, beginning muscle contraction as actin binds to myosin.
Troponin
Structural protein that connects Z disc to M line of sarcomere, helping to stabilize position of thick filament. Because it can stretch and spring back unharmed, it accounts for elasticity & extensibility of myofibrils.
Titin
Structural protein that links thin filaments of sarcomere to integral membrane proteins of sarcolemma, which attach to proteins in connective tissue matrix. Reinforces sarcolemma and helps transmit tension from muscles to tendons.
Dystrophin
Which proteins connect into the Z disc? Which proteins are present in the A band? In the I band?
Actin, titin anchor into Z disc. A bands contain myosin, actin, troponin, tropomyosin, titin. I band contains actin, troponin, tropomyosin, titin.
At the onset of contraction, what organelle releases what substance into the muscle cell? What causes the myosin binding sites on actin to open?
Sarcoplasmic reticulum releases calcium ions. Ca2+ binds to troponin which moves tropomyosin away from myosin-binding sites on actin.
What are the 4 steps of the contraction cycle?
1) ATP hydrolysis - ATP is broken down into ADP & phosphate by ATPase on the myosin head. Energy from hydrolysis reorients and energizes myosin head. 2) Myosin attaches to actin to form cross-bridges - Energy from hydrolysis causes myosin head to attach to myosin-binding site on actin & releases phosphate. 3) Power stroke - crossbridge rotates and releases ADP. Slides thin filament past thick filament toward M line. 4) Detachment of myosin from actin - ATP binds to myosin head and causes it to detach from actin.
During full contraction, what happens to the H zone, Z line, I & A bands?
H zone disappears, Z line moves closer together, I band shortens, A band stays the same.
The process of an action potential spreading into T tubule to the sliding of filaments is called ___.
Excitation-contraction coupling (aka sliding filament theory)
Calcium-binding protein that enables many Ca2+ to be stored in sarcoplasmic reticulum. Concentration of Ca2+ is 10,000 higher in SR than in cytosol.
Calsequestrin
Each of the 600 crossbridges in one thick filament attaches and detaches about ___ times per second.
5 times per second
Condition where muscles are in a state of rigidity. Begins 3-4 hours after death and lasts 24 hrs. Caused by Ca2+ leakage into cytosol which allows myosin to bind to actin. Lack of ATP causes myosin to stay binded to actin.
Rigor mortis
In regards to the length-tension relationship in a skeletal muscle, why would tension decrease in a muscle fiber that is stretched to a longer length? Why would tension again decrease in a shorter than optimum length?
In a longer than normal muscle fiber, the zone of overlap shortens so fewer myosin heads can make contact with actin to contract so tension is zero. In a shorter muscle fiber, thick filaments crumple as they are compressed by Z discs so fewer myosin heads bind with actin.
The synapse between a somatic motor neuron and skeletal muscle fiber.
Neuromuscular junction
Region where communication occurs between 2 neurons, or between a neuron and target cell, ex. Muscle fiber.
Synapse
Small gap at synapse separating 2 cells.
Synaptic cleft
What happens to acetylcholine (Ach) after it binds with Ach receptor on the sarcolemma?
It is broken down by enzyme acetylcholinerase into acetyl and choline so it cannot activate Ach receptor.
List the events that lead to contraction and relaxation in a muscle fiber starting with the presynaptic end bulb.
Action potential arrives at presynaptic end bulb and causes Ca2+ voltage-gated channels to open. Ca2+ flows inward and triggers release of synaptic vesicles containing neurotransmitter Acetylcholine via exocytosis. Ach binds to ligand-gated channels which opens Na+ ion channels and causes inflow of Na+. AchE destroys Ach in synaptic cleft. Na+ in muscle fiber triggers voltage-gated Ca2+ channels to open on sarcoplasmic reticulum and Ca2+ flow into sarcoplasm. Ca2+ binds to troponin and causes it to move tropomyosin so myosin binding sites are exposed. ATP is hydrolized into ADP + phosphate by ATPase on myosin head and released energy causes myosin head to bind to actin, forming crossbridge, and phosphate releases. Powerstroke is caused by ADP release which powers myosin to push actin towards M line (contraction). Ca2+ voltage-gated channels in SR close and Ca2+ active transport pumps use ATP to restore low levels of Ca2+ in sarcoplasm. Low Ca2+ restores troponin-tropomyosin complex which blocks myosin binding site. Muscle relaxes.
Substance produced by bacteria that blocks exocytosis of NT at neuromuscular junction and causes paralysis.
Botulinum toxin (Botox)
Plant derivative that causes muscle paralysis by binding to and blocking Ach receptors so ion channels don't open.
Curare
Energy-rich molecule found only in muscle fibers synthesized from excess ATP.
Creatine phosphate
Creatine phosphate & ATP provide enough energy for muscles to contract maximally for (duration).
15 seconds
What is the role of creatine phosphate?
Excess ATP causes an ATP molecule to donate 1 phosphate head to creatine, forming creatine phosphate and ADP. When contraction begins and ADP levels rise, creatine phosphate returns its phosphate to ADP so ATP is regenerated quickly while other ADP return to mitochondria for ATP regeneration.
Series of ATP producing reactions that do not require oxygen.
Anaerobic respiration
What are the steps in anaerobic respiration? What duration of muscle activity does it provide?
When creatine phosphate supply is depleted, glucose (from blood & storage in muscle fibers) is broken down in a process called glycolysis. This produces pyruvic acid + 2 ATP. If oxygen is present, pyruvic acid enters aerobic respiration pathway to produce more ATP. If no oxygen is present, anaerobic RNXs convert pyruvic acid into lactic acid which is carried away by blood. It provides 30-40 sec of muscle activity.
Series of oxygen-requiring RXNs that produce ATP in mitochondria.
Aerobic respiration
What are the steps in aerobic respiration? What are the 2 sources of oxygen? What duration of muscle activity does it provide?
Pyruvic acid enters mitochondria where it is oxidized in RXNs that generate ATP, carbon dioxide, H2O, heat. It's slower than anaerobic respiration but yields 36 ATP. Oxygen comes from hemoglobin in blood and myoglobin in muscle fibers (both are oxygen-binding proteins). Provides 90%+ of needed ATP in activities more than 10 mins.
Inability of muscle to maintain force of contraction after prolonged activity.
Muscle fatigue
What are 6 factors that contribute to muscle fatigue?
Inadequate release of Ca2+ from SR, depletion of creatine phosphate, insufficient oxygen, depletion of glycogen & other nutrients, buildup of lactic acid & ADP, failure of motor neuron to release enough Ach.
The added oxygen that is taken into the body after exercise.
Oxygen debt / Recovery oxygen uptake
What are the 3 ways oxygen is used to restore muscle cells to the resting level after exercise?
1) Convert lactic acid into glycogen. 2) Synthesize creatine phosphate & ATP. 3) Replace oxygen removed from myoglobin.
The total tension a whole muscle can produce depends on ___.
# of muscle fibers contracting in unison.
Maximum tension is dependent on what 4 factors?
1) Rate at which nerve impulses arrive. 2) Amount of stretch before contraction. 3) Nutrient & oxygen availability. 4) Size of motor unit.
Complex consisting of somatic motor neuron plus all muscle fibers it stimulates.
Motor unit
Brief contraction of muscle fibers in a motor unit in response to an action potential lasting from 20 to 200 msec.
Twitch contraction
Brief delay between stimulus and muscular contraction when action potential sweeps over sarcolemma and Ca2+ is released from SR.
Latent period
Period where Ca2+ binds to troponin and crossbridges form.
Contraction period
Period where Ca2+ is actively transported back to SR, myosin binding sites are covered by tropomyosin, and myosin heads detach from actin.
Relaxation period
Period during muscle fiber contraction where it temporarily cannot respond to another action potential.
Refractory period
Stimuli arriving at different times causing larger contractions in muscle fiber.
Wave summation
What is the difference between unfused vs. fused tetanus?
Unfused tetanus is a sustained but wavering contraction (it can partially relax between stimuli - 20-30x per sec). Fused tetanus is a sustained contraction in which individual twitches cannot be detected (80-100x per sec).
The process in which the number of active motor units increases. What is this process responsible for?
Motor unit recruitment is responsible for producing smooth movements rather than a series of jerks.
Small amount of tension in muscle due to weak, involuntary contractions of motor units. Small groups of motor units are alternatively active and inactive in a constant pattern.
Muscle tone
State of limpness in which muscle tone is lost.
Flaccid
What is the difference between hypotonia vs. hypertonia? What is the difference between spasticity vs. rigidity?
Hypotonia - decrease in muscle tone. Hypertonia - increase in muscle tone. Spasticity - increased muscle tone due to reflexes where as rigidity does not involve reflexes.
Tension developed by muscle remaining almost constant while muscle changes in length is called ___.
Isotonic contraction
Type of contraction where muscle shortens to produce force and movement.
Concentric isotonic contraction
Type of contraction where muscle lengthens to produce force and movement.
Eccentric isotonic contraction
Type of contraction where no movement occurs. Tension is generated without muscle shortening.
Isometric contraction
Type of skeletal muscle fiber that has an increase in blood supply, oxygen, mitochondria, and is therefore aerobic, slow ATP production. Ex. Marathon runner. (red/white)
Red fiber
Type of skeletal muscle fiber that has less blood supply, oxygen, and is therefore anaerobic, quick ATP production. Ex. Sprinter. (red/white)
White fiber
Type of muscle fiber with abundant mitochondria and blood supply. Red. High ATP generation via aerobic respiration. Slow ATP hydrolysis, slow contraction, high fatigue resistance, low glycogen. Recruited first. Found in postural muscles ie. Neck. Function - maintain posture & aerobic endurance activities.
Slow oxidative fibers
Type of muscle fiber with abundant mitochondria and blood supply. Red-pink. Intermediate ATP generation via aerobic & anaerobic respiration (glycolysis). Fast ATP hydrolysis, fast contraction, medium fatigue resistance, intermediate supply glycogen. Recruited second. Found in lower limb mm. Function - walking, sprinting.
Fast oxidative-glycolytic fibers
Type of muscle fiber with few mitochondria and blood supply. White. Low ATP generation via anaerobic respiration (glycolysis). Fast ATP hydrolysis, fast contraction, low fatigue resistance, high glycogen. Recruited third. Found in upper limb mm. Function - rapid, intense movements of short duration.
Fast glycolytic fibers
List the skeletal muscle fibers in the order that they are recruited.
SO, FOG, FG
Irregular transverse thickenings of sarcolemma that connect ends of cardiac muscle fibers to eachother.
Intercalated discs
What 2 types of cell junctions are present in intercalated discs in cardiac muscle tissue? What type of connective tissue lining does it lack?
Desmosomes (support), gap junctions (spread action potential). Lacks epimysium.
Why do cardiac & smooth muscle contractions last longer than skeletal muscle contractions?
In cardiac/smooth muscle fibers, Ca2+ enters sarcoplasm from sarcoplasmic reticulum (like skeletal muscle) and interstitial fluid. In cardiac mm, channels for Ca2+ from interstitial fluid stay open longer. In smooth muscle there are no transverse tubules so Ca2+ takes longer to reach all filaments.
What is the difference between visceral single-unit smooth muscle tissue vs. multiunit smooth muscle tissue?
Stimulation of 1 visceral muscle fiber causes contraction of many adjacent fibers. Stimulation of 1 multiunit fiber causes contraction of that fiber only.
Smooth tissue lack transverse tubules & have low Ca2+ sarcoplasmic reticulum storage. Instead it has small pouchlike invaginations of the plasma membrane called ___ that contain extracellular Ca2+ for muscle contraction.
Caveolae
Structure in smooth mm similar to Z disc in striated muscle fiber. Thin/intermediate filaments attach to it.
Dense bodies
Process that allows smooth mm to undergo great changes in length while retaining ability to contract effectively.
Stress-relaxation response
Almost all muscle in the body is derived from what embryonic tissue?
Mesoderm
Why does muscle strength decrease with aging?
With aging, muscle is replaced by connective & adipose tissue. Slow oxidative fibers appear to increase.
What 3 types of stimuli trigger smooth muscle?
Neurotransmitters, hormones, autorhythmic signals.
Smooth muscle contract/relax in response to what 6 factors?
Action potentials from ANS, stretching, hormones, changes in pH, oxygen/carbon dioxide levels.