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Chapter 9 Flashcard

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synaptic cleft

synaptic cleft
a gel-filled space that separates a muscle fiber and axon terminal
a gel-filled space that separates a muscle fiber and axon terminal
How is ATP regenerated quickly?
Direct phosphorylation of ADP by creatine phosphate (CP)
Anaerobic pathway: glycolysis and lactic acid formation
Aerobic respiration
Direct phosphorylation of ADP by creatine phosphate (CP)  <br />Anaerobic pathway: glycolysis and lactic acid formation <br />Aerobic respiration
voltage gated channels
Vm causes these channels to open.
Vm causes these channels to open.
what are the modified organelles in muscle fibers
Myofibrils
Sarcoplasmic reticulum
T tubules
Myofibrils <br />Sarcoplasmic reticulum <br />T tubules
what are skeletal muscles stimulated by
somatic motor neurons(nerve cells)
somatic motor neurons(nerve cells)
muscular dystrophy
Group of inherited muscle-destroying diseases that generally appear during childhood.
Age of onset is btwn 2 and 10. Muscle weakness progresses. Afflicted individuals usually die of respiratory failure, usually by age 25.
Group of inherited muscle-destroying diseases that generally appear during childhood. <br />Age of onset is btwn 2 and 10.  Muscle weakness progresses.  Afflicted individuals usually die of respiratory failure, usually by age 25.
How long does ATP last?
4-6 seconds. ATP is the only source of energy for contractile activities; therefore it must be regenerated quickly
4-6 seconds. ATP is the only source of energy for contractile activities; therefore it must be regenerated quickly
Cardiac Muscle
found only in heart
Striated
Involuntary: cannot be controlled consciously
found only in heart <br />Striated <br />Involuntary: cannot be controlled consciously
M line
line of protein (myomesin) that bisects H zone vertically
line of protein (myomesin) that bisects H zone vertically
Fast fibers
they can contract in 0.01 seconds or less after stimulation.
large in diameter; contain densely packed myofibrils, large glycogen reserves, and few mitochondria.
Massive ATP use off of anaerobic metabolism
Powerful contractions but quick to fatigue
Short term, power activities
they can contract in 0.01 seconds or less after stimulation. <br />large in diameter; contain densely packed myofibrils, large glycogen reserves, and few mitochondria. <br />Massive ATP use off of anaerobic metabolism <br />Powerful contractions but quick to fatigue <br />Short term, power activities
myofilaments
Orderly arrangement of actin and myosin myofilaments within sarcomere
Orderly arrangement of actin and myosin myofilaments within sarcomere
I band
lighter regions in striations
lighter regions in striations
A band
dark regions in striations
dark regions in striations
what are the three types of muscle tissue
Skeletal
Cardiac
Smooth
Skeletal <br />Cardiac <br />Smooth
Muscle Fatigue
Physiological inability to contract despite continued stimulation
Usually occurs when there are ionic imbalances
Levels of K+, Ca2+, Pi can interfere with E‑C coupling
Prolonged exercise may also damage SR and interferes with Ca2+ regulation and release
Lack of ATP is rarely a reason for fatigue, except in severely stressed muscles
Physiological inability to contract despite continued stimulation <br />Usually occurs when there are ionic imbalances <br />Levels of K+, Ca2+, Pi can interfere with E‑C coupling <br />Prolonged exercise may also damage SR and interferes with Ca2+ regulation and release <br />Lack of ATP is rarely a reason for fatigue, except in severely stressed muscles
Direct phosphorylation of ADP by creatine phosphate (CP)
Creatine phosphate is a unique molecule located in muscle fibers that donates a phosphate to ADP to instantly form ATP
Creatine kinase is enzyme that carries out transfer of phosphate
Muscle fibers have enough ATP and CP reserves to power cell for about 15 seconds
Creatine phosphate is a unique molecule located in muscle fibers that donates a phosphate to ADP to instantly form ATP <br />Creatine kinase is enzyme that carries out transfer of phosphate <br />Muscle fibers have enough ATP and CP reserves to power cell for about 15 seconds
T tubules
Tube formed by protrusion of sarcolemma deep into cell interior
Increase muscle fiber’s surface area greatly
Lumen continuous with extracellular space
Allow electrical nerve transmissions to reach deep into interior of each muscle fiber
penetrate cell’s interior at each A–I band junction between terminal cisterns
Tube formed by protrusion of sarcolemma deep into cell interior <br />Increase muscle fiber’s surface area greatly <br />Lumen continuous with extracellular space <br />Allow electrical nerve transmissions to reach deep into interior of each muscle fiber <br />penetrate cell’s interior at each A–I band junction between terminal cisterns
myosin myofilaments
thick filaments
Extend length of A band
Connected at M line
thick filaments <br />Extend length of A band <br />Connected at M line
Isometric contraction
no shortening; muscle tension increases but does not exceed load
no shortening; muscle tension increases but does not exceed load
Responses are graded by what
Changing frequency of stimulation
Changing strength of stimulation
Changing frequency of stimulation <br />Changing strength of stimulation
contraction strength is a function of
The number of crossbridges that can be made per myofibril
The number of myofibrils per muscle fiber
The number of contracting muscle fibers
The number of crossbridges that can be made per myofibril <br />The number of myofibrils per muscle fiber <br />The number of contracting muscle fibers
Enomysium
fine areolar connective tissue surrounding each muscle fiber
fine areolar connective tissue surrounding each muscle fiber
what is threshold for channels in muscle fibers
In order for these channels to open, the Vm must depolarize from its resting value of –90mV to approximately –50mV.
In order for these channels to open, the Vm must depolarize from its resting value of –90mV to approximately –50mV.
what are the four important functions of muscle
Produce movement: responsible for all locomotion and manipulation
Example: walking, digesting, pumping blood
Maintain posture and body position
Stabilize joints
Generate heat as they contract
Produce movement: responsible for all locomotion and manipulation <br />Example: walking, digesting, pumping blood <br />Maintain posture and body position  <br />Stabilize joints <br />Generate heat as they contract
Smooth muscle
found in walls of hollow organs
Examples: stomach, urinary bladder, and airways
Not striated
found in walls of hollow organs <br />Examples: stomach, urinary bladder, and airways <br />Not striated
what are the four main characteristics of all muscles
Excitability (responsiveness): ability to receive and respond to stimuli
Contractility: ability to shorten forcibly when stimulated
Extensibility: ability to be stretched
Elasticity: ability to recoil to resting length
Excitability (responsiveness): ability to receive and respond to stimuli <br />Contractility: ability to shorten forcibly when stimulated <br />Extensibility: ability to be stretched  <br />Elasticity: ability to recoil to resting length
fibrosis
Replacement of normal tissue with heavy fibrous connective tissue (scar tissue).
Replacement of normal tissue with heavy fibrous connective tissue (scar tissue).
refractory period
muscle fiber cannot be stimulated for a specific amount of time, until repolarization is complete
muscle fiber cannot be stimulated for a specific amount of time, until repolarization is complete
skeletal muscle
can be consciously controlled
Contract rapidly; tire easily; powerful
longest of all muscle and have striations (stripes)
can be consciously controlled <br />Contract rapidly; tire easily; powerful <br />longest of all muscle and have striations (stripes)
what are the three phases of muscle twitch
Latent period: events of excitation-contraction coupling
No muscle tension seen
Period of contraction: cross bridge formation
Tension increases
Period of relaxation: Ca2+ reentry into SR
Tension declines to zero
Latent period: events of excitation-contraction coupling <br />No muscle tension seen <br />Period of contraction: cross bridge formation <br />Tension increases <br />Period of relaxation: Ca2+ reentry into SR  <br />Tension declines to zero
contraction
the activation of cross bridges to generate force
Shortening occurs when tension generated by cross bridges on thin filaments exceeds forces opposing shortening
the activation of cross bridges to generate force  <br />Shortening occurs when tension generated by cross bridges on thin filaments exceeds forces opposing shortening
actin myofilaments
thin filaments
Extend across I band and partway in A band
Anchored to Z discs
thin filaments <br />Extend across I band and partway in A band <br />Anchored to Z discs
Flaccid Paralysis
Weakness or loss of muscle tone typically due to injury or disease of motor neurons
Weakness or loss of muscle tone typically due  to injury or disease of motor neurons
H zone
lighter region in middle of dark A band
lighter region in middle of dark A band
wave (temporal) summation
results if two stimuli are received by a muscle in rapid succession
results if two stimuli are received by a muscle in rapid succession
muscle twitch
simplest contraction resulting from a muscle fiber’s response to a single action potential from motor neuron
simplest contraction resulting from a muscle fiber’s response to a single action potential from motor neuron
contraction
Once actin’s myosin binding site is exposed, myosin will attach to it.
At this point myosin has just hydrolyzed ATP into ADP and Pi – however both molecules are still bound to the myosin.
The ATP hydrolysis provides the energy for the “cocking” of the myosin head
Once myosin is bound to actin, the myosin head will release the ADP and Pi which will cause it change conformation. This results in the thin filament sliding along the thick filament.
Myosin then remains bound to actin until it binds to another ATP. Myosin then hydrolyzes the new ATP and the cycle can begin again
Once actin’s myosin binding site is exposed, myosin will attach to it. <br />At this point myosin has just hydrolyzed ATP into ADP and Pi – however both molecules are still bound to the myosin. <br />The ATP hydrolysis provides the energy for the “cocking” of the myosin head <br />Once myosin is bound to actin, the myosin head will release the ADP and Pi which will cause it change conformation.  This results in the thin filament sliding along the thick filament. <br />Myosin then remains bound to actin until it binds to another ATP.  Myosin then hydrolyzes the new ATP and the cycle can begin again
depolarization
generation and propagation of an action potential (AP)
If end plate potential causes enough change in membrane voltage to reach critical level called threshold, voltage-gated Na+ channels in membrane will open
Large influx of Na+ through channels into cell triggers AP that is unstoppable and will lead to muscle fiber contraction
AP spreads across sarcolemma from one voltage-gated Na+ channel to next one in adjacent areas, causing that area to depolarize
generation and propagation of an action potential (AP) <br />If end plate potential causes enough change in membrane voltage to reach critical level called threshold, voltage-gated Na+ channels in membrane will open <br />Large influx of Na+ through channels into cell triggers AP that is unstoppable and will lead to muscle fiber contraction <br />AP spreads across sarcolemma from one voltage-gated Na+ channel to next one in adjacent areas, causing that area to depolarize
Graded muscle responses
vary strength of contraction for different demands
vary strength of contraction for different demands
Isotonic conrtaction
muscle shortens because muscle tension exceeds load
muscle shortens because muscle tension exceeds load
spasm
A sudden, involuntary smooth or skeletal muscle twitch. Can be painful. Often caused by chemical imbalances. Almost always caused by a lack of potassium
A sudden, involuntary smooth or skeletal muscle twitch.  Can be painful.  Often caused by chemical imbalances. Almost always caused by a lack of potassium
end plate potential
local depolarization caused by:
ACh released from motor neuron binds to ACh receptors on sarcolemma
Causes chemically gated ion channels (ligands) on sarcolemma to open
Na+ diffuses into muscle fiber
Some K+ diffuses outward, but not much
Because Na+ diffuses in, interior of sarcolemma becomes less negative (more positive)
local depolarization caused by: <br />ACh released from motor neuron binds to ACh receptors on sarcolemma  <br />Causes chemically gated ion channels (ligands) on sarcolemma to open <br />Na+ diffuses into muscle fiber <br />Some K+ diffuses outward, but not much <br /> Because Na+ diffuses in, interior of sarcolemma becomes less negative (more positive)
ligand gated channels
the binding of an extracellular molecule (e.g., hormone, neurotransmitter) causes these channels to open.
the binding of an extracellular molecule (e.g., hormone, neurotransmitter) causes these channels to open.
Excitation-contraction (E-C) coupling
events that transmit the action potential (AP) along sarcolemma (excitation) are coupled to sliding of myofilaments (contraction)
events that transmit the action potential (AP) along sarcolemma (excitation) are coupled to sliding of myofilaments (contraction)
repolarization
restoration of resting conditions
Na+ voltage-gated channels close, and voltage-gated K+ channels open
K+ efflux out of cell rapidly brings cell back to initial resting membrane voltage
restoration of resting conditions <br />Na+ voltage-gated channels close, and voltage-gated K+ channels open <br />K+ efflux out of cell rapidly brings cell back to initial resting membrane voltage
perimysium
fibrous connective tissue surrounding fascicles (groups of muscle fibers)
fibrous connective tissue surrounding fascicles (groups of muscle fibers)
synaptic vesicles
contain neurotransmitter acetylcholine (ACh)
contain neurotransmitter acetylcholine (ACh)
sarcolemma
muscle fiber plasma membrane
muscle fiber plasma membrane
motor unit
consists of the motor neuron and all muscle fibers (four to several hundred) it supplies
consists of the motor neuron and all muscle fibers (four to several hundred) it supplies
Atrophy
Reduction in size of a cell, tissue, or organ
Reduction in size of a cell, tissue, or organ
eccentric contractions
muscle contracts as it lengthens (eg - calf muscle as you walk up a steep hill)
muscle contracts as it lengthens (eg - calf muscle as you walk up a steep hill)
what are the four steps to the cross bridge cycling
Cross bridge formation: high-energy myosin head attaches to actin thin filament active site
Working (power) stroke: myosin head pivots and pulls thin filament toward M line
Cross bridge detachment: ATP attaches to myosin head, causing cross bridge to detach
Cocking of myosin head: energy from hydrolysis of ATP “cocks” myosin head into high-energy state
Cross bridge formation: high-energy myosin head attaches to actin thin filament active site <br />Working (power) stroke: myosin head pivots and pulls thin filament toward M line  <br />Cross bridge detachment: ATP attaches to myosin head, causing cross bridge to detach <br />Cocking of myosin head: energy from hydrolysis of ATP “cocks” myosin head into high-energy state
nerve and blood supply
Each muscle receives a nerve, artery, and veins
Consciously controlled skeletal muscle has nerves supplying every fiber to control activity
Each muscle receives a nerve, artery, and veins <br />Consciously controlled skeletal muscle has nerves supplying every fiber to control activity
epimysium
dense irregular connective tissue surrounding entire muscle; may blend with fascia
dense irregular connective tissue surrounding entire muscle; may blend with fascia
sarcoplasm
muscle fiber cytoplasm
muscle fiber cytoplasm
what four steps must occur for skeletal muscle to contract
Nerve stimulation- every muscle cell is in contact with a nerve
Action potential, an electrical current, must be generated in sarcolemma
Action potential must be propagated along sarcolemma
Intracellular Ca2+ levels must rise briefly
Nerve stimulation- every muscle cell is in contact with a nerve <br /> Action potential, an electrical current, must 	be generated in sarcolemma <br /> Action potential must be propagated along 	sarcolemma <br /> Intracellular Ca2+ levels must rise briefly
junctional folds
Infoldings of sarcolemma that contains millions of ACh receptors
Infoldings of sarcolemma that contains millions of ACh receptors
slow fibers
Contract slowly because its myosin ATPases work slowly.
Depends on oxygen delivery and aerobic metabolism.
Is fatigue resistant and has high endurance.
Contract slowly because its myosin ATPases work slowly. <br />Depends on oxygen delivery and aerobic metabolism. <br />Is fatigue resistant and has high endurance.
causes shortening of a muscle fiber
Z discs are pulled toward M line
I bands shorten
Z discs become closer
H zones disappear
A bands move closer to each other
Z discs are pulled toward M line	 <br />I bands shorten <br />Z discs become closer <br />H zones disappear <br />A bands move closer to each other
Muscle fiber contraction
At higher intracellular Ca2+ concentrations, Ca2+ binds to troponin
Troponin changes shape and moves tropomyosin away from myosin-binding sites
Myosin heads is then allowed to bind to actin, forming cross bridge
Cycling is initiated, causing sarcomere shortening and muscle contraction
When nervous stimulation ceases, Ca2+ is pumped back into SR, and contraction ends
At higher intracellular Ca2+ concentrations, Ca2+ binds to troponin  <br />Troponin changes shape and moves tropomyosin away from myosin-binding sites <br />Myosin heads is then allowed to bind to actin, forming cross bridge <br />Cycling is initiated, causing sarcomere shortening and muscle contraction <br />When nervous stimulation ceases, Ca2+ is pumped back into SR, and contraction ends
connective tissue sheaths
Each skeletal muscle, as well as each muscle fiber, is covered in this
Support cells and reinforce whole muscle
Each skeletal muscle, as well as each muscle fiber, is covered in this <br />Support cells and reinforce whole muscle
hypertrophy
Increase in size of a cell, tissue or an organ.
In muscles, hypertrophy of the organ is always due to cellular hypertrophy (increase in cell size) rather than cellular hyperplasia (increase in cell number)
Increase in size of a cell, tissue or an organ.   <br />In muscles, hypertrophy of the organ is always due to cellular hypertrophy (increase in cell size) rather than cellular hyperplasia (increase in cell number)
Sarcomere
Smallest contractile unit (functional unit) of muscle fiber
Contains A band with half of an I band at each end
Consists of area between Z discs
align end to end along myofibril, like boxcars of train
Smallest contractile unit (functional unit) of muscle fiber <br />Contains A band with half of an I band at each end <br />Consists of area between Z discs <br />align end to end along myofibril, like boxcars of train
cramp
A prolonged spasm that causes the muscle to become taut and painful.
A prolonged spasm that causes the muscle to become taut and painful.
myofibrils
are densely packed, rodlike elements
Single muscle fiber can contain 1000s
Accounts for ~80% of muscle cell volume
Striations
Sarcomeres
Myofilaments
Molecular composition of myofilaments
are densely packed, rodlike elements  <br />Single muscle fiber can contain 1000s <br />Accounts for ~80% of muscle cell volume  <br />Striations <br />Sarcomeres <br />Myofilaments <br />Molecular composition of myofilaments
Muscle fiber types
slow fibers
fast fibers
slow fibers <br />fast fibers
sarcoplasmic reticulum
network of smooth endoplasmic reticulum tubules surrounding each myofibril
network of smooth endoplasmic reticulum tubules surrounding each myofibril
concentric contractions
(muscle shortens and does work - picking up a book)
(muscle shortens and does work - picking up a book)
acetylcholinesterase
stops contractions
stops contractions
axons
(long, threadlike extensions of motor neurons) travel from central nervous system to skeletal muscle
(long, threadlike extensions of motor neurons) travel from central nervous system to skeletal muscle
spastic paralysis
Sustained involuntary contraction of muscle(s) with associated loss of function
Sustained involuntary contraction of muscle(s) with associated loss of function
sliding filament model of contraction
states that during contraction, thin filaments slide past thick filaments, causing actin and myosin to overlap more
states that during contraction, thin filaments slide past thick filaments, causing actin and myosin to overlap more
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Cassidy Kennedy
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