Muscle Flashcards
what are the 3 types of muscle?
skeletal, cardiac, smooth
this type of muscle is striated, voluntary, and attached to bone
skeletal
this type of muscle of striated, involuntary, and in the heart
cardiac
this type of muscle is not striated, involutory, and lines hollow organs
smooth
as muscles contract, _____ is generated and this is thermogenesis
heat
motor neurons are found in ____ matter of the spinal cord
gray
what connects muscle to bone?
tendon
______ is a bundle of muscle fascicles
muscle
____ _____ are a bundle of muscle fibers/cells
muscle fascicle
_____ are a contractile assemble of proteins in a muscle cell
myofibrils
_____ are contracting subunits that make up myofibrils
sarcomere
___ _____ is the intracellular storehouse of calcium ions
sarcoplasmic reticulum
____ ____ are a network of tubular passages within striated muscle that are an extension of the plasma membrane
transverse tubules
____ is the primary protein of thin filament
actin
_____ is the primary protein of thick filament
myosin
myosin is driven by ___ to allow for muscle contraction
ATP
____ blocks myosin binding sites on thin filament during relaxation
tropomyosin
there are ___ actin subunits per tropomyosin molecule
7
____ is the calcium sensor that triggers muscle contraction and locks tropomyosin in place when the muscle is relaxed
troponin
troponin is ____ subunits long and is on the ___ filament
3, thin
____ is a spring-like connector of the thick filaments to the Z disc
titin
__-_____ is the primary structural protein of the Z-disc
alpha-actinin
______ is the primary structural proteins of the M-line
myomesin
____ connects the Z- disc to the membrane cytoskeleton and is associated with muscular dystrophy
dystrophin
_____ is the “template” for actin filament length
nebulin
what are the 2 contractile proteins?
actin, myosin
what are the 2 muscle regulatory proteins?
tropomyosin, troponin
what is the synapse between a somatic motor neuron and a skeletal muscle fiber called?
neuromuscular junction (NMJ)
in the end plate potential, depolarization is generated at the muscle membrane due to the binding of what?
Ach
the binding of ACh at the end plate potential triggers an ___ ____ if the EPP exceeds the threshold of the voltage-gated sodium channels
action potential
an action potential is generated at the NMJ if the ____ exceeds the threshold for the __ ___ ___ ____
EPP, voltage gated sodium channel
what part of the NMJ is the post-synaptic portion?
motor end plate
the motor end plate has ____ receptors and ligand gated channels
ACh
_____ is at the motor end plate and degrades Ach after a signal is sent to the muscle and clears the synapse for a new signal
acetylcholinesterase
muscle action potentials are ______ than nerves because of the different proteins
longer
action potentials in muscles track along the _____
membrane
what is the term for the junction of the transverse tubule with the sarcoplasmic reticulum?
triad
what receptor on the membrane surface is:
-L type votage-gated calcium channel
-found in T-tubule membrane
-moves in response to action potentials/voltage sensor
DHP
what receptor on the membrane surface is:
-calcium release channel
-found in the SR membrane
-opens to release calcium when the DHP receptor moves
RyR
what on the cell membrane:
-is found in the SR membrane
-pumps calcium into the SR against it’s concentration gradient
-takes calcium back into the SR via active transport
SR calcium-ATPase
during the contraction of skeletal muscle fibers, the width of the __ band does not change but the width of the ___ band narrows
A, I
in the sliding filament mechanism, the _____ filaments slide inwards towards the center of the sarcomere
thin
in the sliding filament mechanism, myosin heads attach to ____ filaments and pull them in both halves of the sarcomereno
thin
in the sliding filament mechanism, do the individual lengths of thick and thin filaments change?
no
in the sliding filament mechanism, what two things does contraction result in?
z-discs coming closer, sarcomeres shorten
what two things does sarcomere shortening lead to in the sliding filament mechanism?
myofibril shortening, whole muscle shortening
what molecule leads to shortening and contraction of muscle?
calcium
in the contraction cycle, what occurs so that myosin is energized and perpendicular to the thin filament?
ATP hydrolysis
in the contraction cycle, what is the crossbridge?
myosin head attaches to the binding site on actin and the phosphate group is released
in the contraction cycle, describe the power stroke
myosin head pivots and pull the thin filament towards the center of the sarcomere, generating force and ADP is released
in the contraction cycle, what causes the crossbridge to detach for actin?
actin binds to another ATP and myosin heads detach
in simple terms, outline the contraction cycle
- myosin bind ATP and becomes energized
2.myosin head binds to actin to form a crossbridge (energy is held onto) - crossbridge pivots, pulling thin filament past the thick filament toward the center of the sarcomere (powerstroke)
- myosin heads bind to ATP, crossbridge detaches from actin
what action is needed to start the contraction cycle?
calcium released into sacroplasm
what two events occur for the relaxation phase of muscle?
- calcium pumps reaccumulate calcium into the SR
- troponin blocks binding site
troponin holds tropomyosin in position to block ______ -____ _____ on actin
myosin binding sites
Why does acetylcholinesterase destroy Ach?
so that another muscle action potential does not arise unless more Ach is released from the somatic motor neuron
in muscle contraction, a muscle potential travels along a ___ ____ and triggers a change in the ______ that causes calcium release channels to open and calcium ions go into the sarcoplasm
transverse tubule, DHR
after calcium is released into the sarcoplasm, it binds to ____ on the thin filament and exposes the myosin-binding sites on actin
troponin
how are calcium levels in the sarcoplasm restored?
calcium channels close, calcium ATase pump uses ATP to pump out back into the SR
what molecule blocks the myosin-binding sites on actin?
tropomyosin
what type of contraction:
-is the activation of muscle but shortening is prevented
-change in tension and rate of force development is measure
isometric
what type of contraction:
-activation of muscle when muscle shortening is allowed
-change in length and rate of shortening can be measured
isotonic
what are the two important components of the electrical stimulus that leads to skeletal muscle contraction?
amplitude (strength of signal)
frequency (rate of signaling)
what type of ATP production:
-one step reaction/fast
-transfers P from creatine-phosphate to ADP to regenerate ATP
-limited capacity
creatine kinase
what type of ATP production:
-multistep reaction
-anaerobic
-converts 1 glucose to 2 ATP
glycolysis
what type of ATP production:
-multistep reaction
-requires oxygen and mitochondria
-able to convert glucose to 36 ATP as well as fatty acids and amino acids into ATP
oxidative phosphorylation
what are the 3 muscle fiber types?
slow-oxidative, fast-oxidative, fast-glycolytic
what type of muscle fiber:
-red muscle
-small diameter
-slow myosin aerobic metabolism
slow-oxidative
what type of muscle fiber:
-red muscle
-intermediate diameter cells
-fast myosin, aerobic and anaerobic metabolism
fast-oxydative
what type of muscle fiber:
-white muscle
-large diameter cells
-anaerobic metabolism
fast-glycolytic
define a motor unit
motor neuron and the population of muscle fibers it innervates
during muscle fiber recruitment, as the load increased, the ____ of the motor units recruited increase
size
in what order are motor units recruited?
slow oxidative, fast oxidative, fast glycolytic
____ ____ provides a reservoir of high energy phosphate that accumulates during muscle cell rest
creatine kinase
creatine kinase provides ATP during the ___ ___ _____ of a contraction
first few seconds
what is ATP production in the cell limited by?
amount of creatine kinase stored in the cell
creatine kinase powers ___ ____ of muscle activity
short periods
glycolysis and/or oxidative phosphorylation during periods of rest can regenerate ___ _____ from ATP and creatine because the creatine kinase enzyme can run in reverse
creatine phosphate
what is described as a glucose polymer that is stored by muscle cells and the liver?
glycogen
glycolysis occurs during ___ intensity exercise and powers ____ periods of muscle activity
high, short
what type of ATP production powers extended periods of muscle activity?
oxidative phosphorylation
in oxidative phosphorylation, ____ is the major fuel for the first 5-10 minutes and _____ _____ are the next fuel
glycogen, fatty acids
how do muscles grow?
more myofibrils in the muscle cytoplasm
slow-oxidative fibers use what type of ATP prouction?
oxidative phosphorylation
slow-oxidative fibers are ____ resistant
fatigue
postural muscles are what type of fiber?
slow-oxidative
what type of ATP production is used by fast-oxidative fibers?
oxidative phosphorylation
what type of ATP production is used by fast-glycolytic fibers?
glycolytic metabolism
fast-glycolytic fibers are prone to ____
fatigue
_____ is a prolonged contraction and allows us to walk
tetanus
what 3 factors affect how much tension a whole muscle can produce?
-number of active motor units
-number of muscle fibers in each motor unit
-fiber types of the activated motor units
what are the 4 potential causes of muscle fatigue?
- high extracellular K- depressed membrane potential and reduces excitability
- high intracellular ADP- inhibits crossbridge cycling
- calcium regulation disruption- insufficient calcium release
4.acidification of sarcoplasm- myosin’s ATPase activity less in acid
this describes what skeletal muscle’s fatigability:
-slow myosin ATPase
-least amount of tension
-less likely to fatigue
slow oxidative
this describes what skeletal muscle’s fatigability:
-fast myosin ATPase
-moderative level of tension
-moderate likely to fatigue
fast oxidative
this describes what skeletal muscle’s fatigability:
-fast myosin ATPase
-greatest amount of tension
-most likely to fatigue rapidly
fast glycolytic
what is the effector of the somatic nervous system?
skeletal muscle
what is the motor neuron pathway of the somatic nervous system?
-one neuron pathway
-single somatic motor neurons extends from CNS to synapse directly with effector
what is the neurotransmitter of the somatic nervous system?
ACh
what is the receptor type on the effector organ in the somatic nervous system?
cholinergic
what is the action of the neurotransmitter on the effector on the somatic nervous system?
always excitatory causing contraction of skeletal muscle
what controls the motor output in the somatic nervous system?
voluntary control from cerebral cortex, contributions from basal nuclei, cerebellum, brain stem, and spinal cord
what are the four sources of input to lower motor neurons?
- local circuits in the brain stem and spinal cord
- upper motor neurons from brain stem
- basal nuclei
- cerebellum
what source of input to lower motor neurons is the highest level of control?
upper motor neurons from cerebral cortex
what sources of input to lower motor neurons are the middle level of control?
basal nuclei, cerebellum
what source of input to lower motor neurons is the lowest level of control?
local circuits in brain stem and spinal cord
what is the role of the sensory neuron in somatic reflex arches?
peripheral receptor
what is the role of interneurons in the somatic reflex arches?
relax sensory information
what is the role of the somatic motor neuron in somatic reflex arches?
integrating center and effector control
what is the effector in the somatic reflex arches?
skeletal muscle
what are the three sources of response for the somatic reflex arches?
pain, length of muscle change, excessive muscle tension
____ ___ ____ arches may result in excitation or inhibition of alpha motor neurons
somatic reflex arches
what are the two sensory receptors that trigger skeletal muscle reflex responses?
muscle spindles, golgi tendon organs
__ ___ ____ are responsible for the control of involuntary movement that regulates posture, balance, muscle tone, and reflective movement of the head and trunk
upper motor neurons
what is controlled by vestibular nuclei?
posture and balence
what is controlled by the reticular formation?
posture and muscle tone during movements/ongoing movements
the ___ ______ tract exists muscles in upper motor neuron pathways
medial reticulospinal
the ____ _____ tract inhibits muscles in upper motor neuron pathways
lateral reticulospinal
what is the role of the superior colliculus?
assist with movements of the heads, trunk, and eye movements through the tectospinal tract and respond to sudden or unexpected stimuli
what tract is used by the superior colliculus?
tectospinal
what is the role of red nucleus?
control precise voluntary movements of the upper limbs through the rubrospinal tract
what tract is used by red nucleus?
rubrospinal
what tract of the upper motor neuron tract:
-crosses body at medulla
-responsible for precise and agile movements of hands and feet
lateral corticospinal
what tract of the upper motor neuron tract:
-crosses body at the spinal cord
-responsible for trunk and proximal parts of the limbs
ventral corticospinal
what pathways of the upper motor neurons control facial expression, chewing, speech, and movements of the eyes, tongue, and neck?
corticobulbar
where does the corticobulbar pathway descend from?
cerebral cortex along corticobulbar tract
do all axons of the corticobulbar pathways cross over?
no
why does the face have a large representation in the motor homunculus?
emotionally expressive
what are the 4 actions of the basal nuclei?
- control initiation of movement
- control suppression of unwanted movement
- regulation of muscle tone
- regulation of non-motor processes
in what way do basal nuclei control the suppression of unwanted movement?
tonic inhibition of neurons in the thalamus
in what way do basal nuclei regulate muscle tone?
they send action potentials through the reticulospinal tract
in what way do basal nuclei regulate non-motor processes?
limbic system
what are 3 diseases of the basal nuclei?
parkinson’s, huntington’s, tourette’s
what are the 4 roles of the cerebellum?
- monitors intention for movement
- monitors actual movement
- compares command signals with sensory information
- sends out corrective feedback
does smooth muscle have myofibrils?
no
what is unique about thick filaments in smooth muscle?
have myosin crossbridges alone entire length
thin filaments of smooth muscle are composed of tropomyosin but no _____
troponin
does smooth muscle have z lines?
no
where do you find smooth muscle?
lining hollow structures and organs
smooth muscle cytosolic calcium concentration are increased in a ____ _____
graded manner
the amount of tension generated in a smooth muscle depends on what?
concentration of calcium in the cytosol
in what 3 ways can extracellular calcium enter for smooth muscle contraction?
voltage calcium channels, ligated calcium channels, stretch activated cation of sodium and calcium
what is the purpose of G-protein coupled receptors in smooth muscle contractions?
release of calcium from intracellular stores
____ is the calcium sensor in smooth muscles
calmodulin
how is kinase activated in smooth muscle?
ca bound calmodulin complex binds to myosin light-chain kinase
what is the role of myosin light chain kinase (MLCK) in smooth muscle?
phosphorylates myosin’s regulatory light chain when active
what activates the MLCK in smooth muscle?
ca calmodulin
what is the role of myosin light chain phosphatase (MLCP)?
dephosphorylates myosin’s regulatory light chain to relax smooth muscle
myosin is related to ___ filament
thick
actin is related to ____ filament
thin
activated MLCK phosphorylates the myosin regulatory light chain (RLC) by transferring a ______ from ____
phosphate, ATP
contraction in smooth muscle is ____ and lasts ____ than contraction in skeletal muscle
slower, longer
what two things lead to relaxation in smooth muscles?
decrease in sarcoplasm calcium levels, dephosphorization of myosin by MLCP
___ ___ ___ ____ are connected by gap junctions so that excitation of cell results in the excitation of the entire collection of interconnected muscle cells
single-unit smooth muscles
____ _____ ____ _____ are rare and activate individually after reception of the activation signal
muti-unit smooth muscles
for both cell types of autonomic innervation, physical interconnections in the ______ of the cell membrane facilitate the development of tension through smooth muscle tissue
desmosomes
the stomach has what type of autonomic innervation cell type?
single-unit
the eye and uterus prior to pregnancy have what type of autonomic innervation cell type?
multi-unit
pacemaker cells have an unsteady resting membrane due to ___ ___ ____
leaky ion channels
in slow wave autorythmic cells, threshold is never reached and an ____ signal is needed to reach potential
autonomic
the knee jerk reflex is a _____ _____ ____
monosynaptic reflex arch
the knee jerk flex is a ___ lateral reflex
ipsi
the ____ ____ ____ _reflex causes muscle relaxation in response to too much tension and regulates muscle tension
golgi tendon organ
the golgi tendon organ reflex is ___lateral
ipsi
in the golgi tendon organ reflex, the opposing muscle is activated/contracts through a _____ reflex
polysynaptic
the withdrawal reflex (flexor reflex) involves ____ receptors
pain
the withdrawal reflex (flexor reflex) is ___lateral
ipsi
the withdrawal reflex (flexor reflex) is a ____ reflex arch to move a limb
polysynaptic
the withdrawal reflex (crossed extensor reflex) causes what?
extension of the opposite limb during a flexor reflex to maintain balance
the withdrawal reflex (crossed extensor reflex) is a _____ reflex arch
poly
the withdrawal reflex (crossed extensor reflex) is ____lateral, as sensory inputs enter one side of the spinal cord and motor outputs exit on the opposite side
contra
a ____ is a brief contraction by a muscle stimulated by a single action potential
twitch
what are the 3 phases of twitch?
latent, contraction, relaxation
the ___ phase is the brief delay between the situation and the start of contraction
latent
the ____ phase is the time period when the muscle is actively generating tension
contraction
the ____ phase is the time period when the muscle tension is decreased to baseline
relaxation
multiple stimuli leads to a wavering but sustained contraction called ____ _____
incomplete/unfused tetanus
a high frequency rate of stimuli makes the muscle not relax at all and a maximum force to be reached. This is ___ _____
complete tetanus
large motor units control what type of movement?
large-scale and powerful
small motor units control what type of movement?
precise
____ stimulus activates a single motor unit and produces a small force contraction
threshold
____ stimulus recruits and activates multiple motor units and produces a greater force
submaximal
____ stimulus recruits and activates all motor neurons and produces maximum contraction force
maximal
isometric contraction can occur when?
you try to lift an object too heavy for your muscles to move
______ contractions are used to maintain posture
isometric
in ____ contractions, tension develops in the muscle but does not reach the force level required to move the load
isometric
in an ____ contraction, tension rises to a level larger than the load and remains contact while the muscle changes lnegth
isotonic
____ contraction is the contraction used when moving objects
isotonic
_____ is the major factor that determines the shortening velocity of a muscle
load
in ___ contractions, load and velocity and inversely relation, and as load increases, shortening velocity decreases
isotonic
tetanus is the maximum _______
tension
maximum shortening velocity occurs with ___ load
zero
maximum isometric tension occurs with ____ velocity
zero
human muscle nerves are stimulated through skin at points known as ____ _____
motor points
the duration of a muscle twitch is determined by what?
speed at which calcium is released into the sarcoplasm compared to the slower re-uptake of calcium into the SR by CA ATPase
what leads to a larger stimulus in muscle contraction?
build up of calcium
____ ___ _____ responds to changes in muscle length
muscle spindle reflex
____ _____ ___ responds to tension changes
golgi tendon reflex
____ is needed to allow myosin to release from actin
ATP
the end plate potential is a ____ potential
graded
is an isometric contraction, the latent period allows for what to occur?
build up of tension
what is the Y axis on an isotonic graph?
distance shortened
does smooth muscle have sarcomeres?
no
what is unique about the calmodium calcium sensor in smooth muscles?
is not bound/is free in the cytoplasm
in smooth muscle, the phosphate group is added to what chain on the myosin light chain?
regulatory
what removes phosphate from myosin in smooth muscle?
phosphatase
what is the overall goal of alpha/gamma coactivation?
resent in sensitivity to muscle spindle length changes
