99 Cards in this Set
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sliding filament model
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during contraction, thin and thick filaments slide past each other so that actin and myosin overlap
*neither thick nor thin filaments actually change in length
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What happens as a muscle cell shortens
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-I band shortens
-Distance between Z-discs shorten
-H-zone disappears
-Continuous A-bands move closer together, but their length does not change
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What specific molecule binds calcium?
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troponin -- binds to calcium and changes shape of troponin c
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Tropomyosin
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covers up the myosin binding site on actin
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Why is troponin important?
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key protein that binds to calcium and changes the shape of troponin c
causes us to expose the myosin binding site on the actin molecule
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Which organelles have the highest resting concentration of calcium?
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the SR has the highest resting concentration of calcium
the mitochondrion provides the ATP energy a cell needs for muscle activity
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What induces a skeletal muscle to contract?
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1. the fiber must be activated (stimulated by a nerve ending)
2. Action potential must be generated (electrical current) in the sarcolemma
3. action potential must be propagated along the sarcolemma
4. intracellular calcium ion levels must rise briefly, providing the trigger for contr…
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What nerve cells innervate skeletal muscles?
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somatic motor neurons
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where/ how many neruomuscular junctions are located in a muscle fiber
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each muscle fiber has 1 neuromuscular junction that is about midway in length down the muscle fiber
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What is within the axon terminal?
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synaptic vescicles
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what are the importance of synaptic vesicles?
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they contain neurotransmitter -- acetylcholine
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What are the components of the neuromuscular junction?
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-axon terminals
-synaptic cleft
-junctional folds
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how is an action potential generated?
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a) generation of an end plate potential
b) depolarization: generation and propagation
c) repolarization: restoration of sarcolemma to its original state
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How does a motor neuron stimulate a muscle fiber?
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a) nerve impulse reaches the end of an axon, synaptic vesicles dock with the membrane and release ACh
b) ACh diffuses across the synaptic cleft
c) ACh attaches to receptors on the sarcolemma of the muscle fiber
d) ACh triggers an action potential
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Acetylcholinesterase
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breaks down ACh into its building blocks: acetic acid and choline
helps remove ACh and thus stops muscle contraction
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Generation of an end plate potential in the formation of an action potential
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when ACh attaches to the receptors on the sarcolemma, ligands open and allow Na+ and K+ to pass
more Na+ diffuses in than K+ diffuses out
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Depolarization in the formation of an action potential
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the end plate potential initiates a chain reaction of na+ channels opening to allow for the inflow of sodium
creation of a chemical gradient
Once threshold is reached, an action potential is generated
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what is "propagation" of an action potential
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the action potential moves in all directions creating a rippling effect away from the neuromuscular junction
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What is repolarization in the formation of an action potential?
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na+ channels close and K+ channels open
refractory period
cell can not be stimulated again until repolarization is complete
restores electrical conditions
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The na+/K+ pump restores what?
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ionic conditions
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excitation coupling
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...
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a contraction in which the muscle does not shorten but its tension increases
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isometric
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T/F
The thin filaments (actin) contain a polypeptide subunit G that bears active sites for myosin attachement
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T
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How is the force of muscle contraction controlled?
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by multiple motor unit summation (recruitment)
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T/F
A motor neuron and all the muscle cells that is stimulates are referred to as a motor end plate
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F
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Used to convert ADP to ATP by high-energy phosphate group.
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creatine phosphate
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T/F
A resting cell potential is caused by a difference in the concentration of certain ions in and outside the cell
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T
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Single unit smooth muscle
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coupled via gap junctions
contracts rhythmically
my exhibit spontaneous action potentials
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multi unit smooth muscle
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rare gap junctions
infrequent spontaneous depolarizations
structurally independent of muscle fibers
rich nerve supply
graded contactions
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Locations of multi unit smooth muscle
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-large airways
-large arteries
-arrector pilli muscles
-internal eye muscles
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hyperplasia
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division of smooth muscle
can divide and make smooth muscle cells
only in non striated muscle
happens in:
-arteries: atherosclerosis
-uterus: puberty, pregnancy
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What is the effect of the neurotransmitter on the muscle cell membrane?
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to modify its ion permeability properties temporarily
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contractures
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a shortening/hardening of muscles leading to deformity and rigid joints
caused by a lack of ATP
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How are the strongest muscle contractions normally achieved?
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by increasing the stimulation to the maximum stimulus
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oxygen deficit
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-recovery oxygen uptake
-amount of oxygen taken into the body immediately after exertion
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What is the latent period
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-time in which the impulse is traveling down the sarcolemma and t-tubules
-immediately follows the stimulus at a skeletal muscle
-when the events of excitation coupling occur
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what results from resistance exercise?
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-increase in the number of myofibrils
-increase in respiratory efficiency
-increase in circulatory efficiency
does not increase number of muscle cells
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What effects the velocity and duration of muscle contraction
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load on the muscle fiber
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aponerousis
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sheet-like indirect attachement to a skeletal element
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what surrounds an individual muscle cell?
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endomysium
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Smooth muscles that act like skeletal muscle but are controlled by the autonomic nerves and hormones
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multiunit muscles
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why does rigor mortis occur?
what is rigor mortis?
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there is not ATP available to release attached actin and myosin molecules
stiffening of muscles and joints a few hours after death lasting 1-4 days
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how does the body restore oxygen uptake after oxygen deficit?
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-replaces oxygen removed from the myoglobin
-converts lactic acid back into glycogen stored in the liver
-resynthesizes creatine phosphate and ATP in the muscle fibers
DOES NOT increase level of lactic acid in the muscle
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The warm up period required of athletes to bring their muscles to peak preformance
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treppe
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What is the main effect of the warm up period for athletes
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to enhance the availability of calcium and the efficiency of enzyme systems as the muscle contractions increase in strength
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Refractory period
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when a muscle is unable to respond to stimuli temporarily
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What are ways that a muscle contraction can be graded?
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-changing the frequency of the stimulus
-changing the strength of the stimulus
NOT by changing the muscles involved in the contraction
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What is excitation coupling
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a sequence of events which the transmission of an action potential along the sarcolemma leads to the sliding of myofilaments
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high extracellular calcium can lead to what?
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apoptosis
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Isometric vs isotonic
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Isometric- "same measure" tension develops and load does not move
Isotonic- "same tension" muscle tension develops and overcomes the load
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amount of muscle shortening measured
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isotonic
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amount of increasing muscle tension measured
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isometric
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latent period
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the first few milliseconds following simulation when excitation contraction coupling
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wave/temporal summation
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when a second contraction occurs before the muscle has completely relaxed
greater muscular force
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incomplete/unfused teatnus
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when a muscle is in a sustained quivering state
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complete teatnus
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sustained contraction
muscle relaxation dissapears
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stimuli that produce no observable contractions
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sub-threshold stimuli
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stimuli that the first observable contraction occurs
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threshold stimuli; beyond this point the muscle contracts more vigorously
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strongest stimulus that increases contractile force
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maximal stimulus
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why is the size principle important
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it describes how largest motor units are the least excitable
allows for increase in force during weak contractions
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muscle tone
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helps stabilize joints and maintain posture
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concentric isotonic contractions
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the muscle shortens and does work
ex: flex biceps when picking up a weight
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eccentric muscle contractions
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muscle generates force as it lengthens
ex: straightening your arm on a bench press
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motor unit
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axon of a motor neuron and the muscle fibers it innervates
all muscle fibers in a particular unit are of the same type
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force of muscle contraction factors
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-size of muscle fiber (hypertrophy)
-number of muscle fibers recruited
-frequency of stimulation
-degree of muscle stretch
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what are the factors that influence velocity and duration of muscle of contraction?
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-muscle fiber type
-load
-recruitment (delivers increasing shock to bring more and more muscle fibers into play)
greater load = greater latent period
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glycolytic fibers
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rely more on glycolysis and creatine phosphate than oxygen for ATP generation
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slow oxidative fiber
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-endurance type activities (running a marathon)
-depends on oxygen delivery (has high oxidative capacity)
-little power
-many mitochondrion (sites of oxygen use)
-rich capillary supply
-Red in color
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fast glycolytic fiber
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-short term fast movements
-contracts fast
-uses little oxygen
-depends on glycogen reserves
-few mitochondria
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fast oxidative fibers
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-sprinting and walking
-rely on oxygen
-rich supply of myoglobin and capillaries
-contract quickly
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Aerobic excercise
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-increases mitochondria
-increases capillaries
-more myoglobin
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Can resistance activities convert fast oxidative fibers into fast glycolytic fibers
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yes
but they can also revert if resistance activity is discontinued
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How do aerobic and resistance exercises differ in their effects on muscle size and function?
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muscle resistance activities increase muscle size and strength
aerobic activities increase muscle endurance
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smooth muscle layers
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longitudinal layer
circular layer
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caveolae
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pouch-like foldings containing large numbers of calcium channels in smooth muscle
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how does calcium enter a smooth muscle
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through caveolae channels from the extracellular space
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how does smooth muscle myofilaments differ from skeletal muscle myofilaments
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-thick filaments are fewer but have myosin heads along the entire length
-thick filaments contain myosin heads along their entire length
-no troponin complex in thin filaments (calmodulin)
-thick and thin filaments arranged diagonally (contract in corkscrews)
-have an intermediate fil…
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what is calcium binding site in smooth muscle
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calmodulin
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single unit smooth muscle
(visceral or unitary)
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-walls all hollow organs except the heart
-more common than multi-unit
-longitudinal and circular sheets
-innervated by autonomic nerve fibers
-recruitment is not an option
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recruitment in muscles
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delivery of increasing shock to bring more and more muscle fibers into play
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muscular dystrophy
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muscle destroying disease during childhood
muscles enlarge due to deposit of connective tissue
muscles degenerate
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Duchenne muscular dystrophy (DMD)
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sex linked recessive disease in males
form of muscular dystrophy
sarcolemma tears allowing for inflow of Ca2+ and damages contraction fibers
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smooth muscles that act like skeletal muscles but are controlled by autonomic nervous system
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multi-unit smooth muscle
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a sheet-like indirect attachment to a skeletal element
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aponeurosis
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periotontis
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the inflammation of the peritoneum
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mesentary
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double layer of peritoneum
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Layers of the alimentary canal from innermost to outermost
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mucosa
submucosa
muscularis externa
serosa (visceral peritoneum)
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purpose of mucosa membrane
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secrete, absorb, protect
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lamina propria
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nourishes the mucosa layer and provides lymph
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muscularis mucosae
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external to the lamina propria in the mucosa layer
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submucosa
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outer to the mucosa layer
provides nourishment and lymphatic vessels
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Muscularis Externa
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responsible for peristalsis (adjacent contraction)
and segmentation (non adjacent contraction)
has inner circular layer and outer longitudinal layer
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serosa
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outer layer of the alimentary canal
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rather than the serosa layer, the esophagus has what?
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adventitia
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short reflexes are controlled by what
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the enteric nervous system
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long reflexes are controlled by what
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CNS and extrinsic autonomic nerves
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parietal cells
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secrete intrinsic factor
H , Cl
absorbs b-12 for the absorption of iron
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chief cells
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secrete pepsinogen
breaks down triglycerides
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cementum
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attaches the tooth to the periodontal ligament
the periodontal ligament anchors the tooth to the bony socket
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EXSC 223: Exam 1