Muscle Flashcards
In the relaxed state, the binding of myosin to actin is prevented because the binding site on actin is covered by _______.
tropomyosin
Dystrophin links the _____ with the _____.
cytoskeleton; extracellular matrix
The _____ is located in the t-tubule membrane.
DHPR (dihydropyridine receptor)
Single amino acid mutations in the regulatory regions of a _____ or a _____ produce muscle disease.
myofilament protein; regulatory protein
Striations results from the ______ in precise register across the width of the myofiber.
stacking of sarcomeres
At the Z line, _____ is a molecule that crosslinks actin filaments.
alpha-actinin
Increased calcium in the _____ cell binds to calmodulin and the Ca-calmodulin binds to CaM kinase and activates it so that one of the light chains on the _____ is phosphorylated.
smooth muscle; myosin head
As you exercise, more _____ are added and the muscle fibers get larger.
myofilaments
What is a muscle cell stem cell called?
satellite cells
Transmission of the action potential to the interior occurs via the ______ membrane.
transverse tubule (t-tubule)
Cardiac and smooth muscle can function without _____.
nervous innervation
How can cardiac and smooth muscle tension be graded?
1) neurotransmitters 2) hormone-like molecules 3) cell length
Bound to the actin filaments are two important regulatory proteins, _____ and ______.
tropomyosin; troponin
_____ links the cytoskeleton with the extracellular matrix.
Dystrophin
Depolarization of a muscle cell will open Na channels and an _____ is initiated.
action potential
A muscle cell is called a _____.
myofiber
The ______ is the connective tissue within the fascicles that surrounds and invests the muscle cells.
endomysium
The ______ is in the SR membrane and is a Ca release channel.
RyR (ryanodine receptor)
The ______ surrounds the fascicles.
perimysium
Where are the nuclei located in skeletal muscle cells?
in the periphery
The majority of people with _____ have mutations in the cardiac myosin heavy chain
FHC
Dantrolene blocks muscle contraction by blocking ____ release from the SR.
Ca+2
A fascicle is a ______.
bundle of muscle cells
______ causes a conformational change in the DHP receptor that in turn causes the calcium release channel to open and Ca flows out of the SR.
Depolarization
The endomysium is the connective tissue within the fascicles that ______.
surrounds and invests the muscle cells
How many nuclei does a skeletal muscle cell have?
many- can be several hundred
Both cardiac and smooth muscle cells are linked by ______.
gap junctions
About half of all cases of sudden death due to cardiac arrest in young athletes are due to ______.
familial hypertrophic cardiomyopathy (FHC).
The shortening of the sarcomere is about ____.
8 nm
Increased _____ in the smooth muscle cell binds to calmodulin, and the Ca-calmodulin binds to _____ and activates it so that one of the light chains on the myosin head is phosphorylated.
calcium; CaM kinase
In MH, the steady Ca+2 leak from the SR activates the _____ to pump Ca+2 back into the SR and a futile, heat-producing cycle occurs and is lethal if not corrected.
Ca+2 ATPase
In smooth muscle, removal of Ca is accomplished by ____ and _____ in the sarcolemma.
Ca pumps; Na-Ca exchangers
What is the incidence rate of MH?
1:15,000
_____ contains no troponin, but calcium is still the key regulatory molecule.
Smooth muscle
The DHPR (dihydropyridine receptor) is located in the ______.
t-tubule membrane
What does FHC stand for?
familial hypertrophic cardiomyopathy
Transmission of the action potential to the ____ occurs via the transverse tubule (t-tubule) membrane.
interior
Small motor units are recruited _____ and progressively larger motor units are _____ as the strength of contraction is increased.
first; recruited
Smooth muscle cells are so thin that Ca+2 entering via Ca+2 channels in the surface membrane can easily ______.
diffuse to the center of the cell
_____ makes up the thin filaments.
F-actin
The myosin in fast twitch muscle cycles about ____ times per second.
20
One of the subunits of the DHP receptor is a _____; the other molecule is the RyR (ryanodine receptor).
voltage-gated Ca channel
Fibroblasts prevent the premature differentiation of _____.
satellite cells
Each _____ is wrapped in its own SR.
myofibril
Depolarization causes a conformational change in the _____ that in turn causes the calcium release channel to open and Ca flows out of the SR.
DHP receptor
An abnormal calcium release channel in the SR causes a disease called _______.
malignant hyperthermia (MH)
What does MH stand for?
malignant hyperthermia
______ can repair itself; the cells can dedifferentiate, enter mitosis, and regenerate new muscle cells.
Smooth muscle
As strength increases, the cross sectional area of each cell is increased; new ______ are formed.
myofibrils
The thick filaments are_____ long and contain 300-400 myosins.
1.6 micrometers
_____ are recruited first and progressively _____ are recruited as the strength of contraction is increased.
Small motor units; larger motor units
Binding of _____ allows myosin to dissociate from actin.
ATP
What is the triad?
apposition of the SR and the t-tubule that looks dark in microscopy
The AChR is an _____ that opens and causes depolarization.
ion channel
In normal, relaxed muscle [Ca]i is _____.
low (
Muscles that ______ tend to have small motor units while large muscles that make _____ have large motor units.
perform fine movements; gross movements
______ in the regulatory regions of a myofilament protein or a regulatory protein produce muscle disease.
Single amino acid mutations
Calsequestrin is found at the _____, and each molecule binds about 50 Ca.
terminal cisterna
Patients with MH have a _____ when they are given volatile anesthetics (such as halothane) for surgery.
catastrophic rise in body temperature
The end of the SR at its contact with the _____ is called the terminal cisterna.
t-tubule
Patients with MH have a catastrophic rise in body temperature when they are given _____ for surgery.
volatile anesthetics (such as halothane)
Nebulin is associated with ______ and is thought to be important for keeping the thin filaments organized.
actin thin filaments
_____ is associated with actin thin filaments and is thought to be important for keeping the thin filaments organized.
Nebulin
Where is the DHP receptor located?
in all muscles
_____ is found at the terminal cisterna, and each molecule binds about 50 Ca.
Calsequestrin
The end of the SR at its contact with the t-tubule is called the _____.
terminal cisterna
Bound to the _____ filaments are two important regulatory proteins, tropomyosin and troponin.
actin
Calsequestrin is found at the terminal cisterna, and each molecule binds about _____.
50 Ca
The DHP receptor is the cause of ______.
muscular dysgenesis
In smooth muscle, removal of ____ is accomplished by pumps and Na-Ca exchangers in the sarcolemma.
Ca
There are no _____ in cardiac muscle, so scar tissue forms.
satellite cells (stem cells)
A _____ is a bundle of muscle cells.
fascicle
The myosin in ____ cycles about 5 times per second.
slow twitch muscle
An action potential in the motor axon causes release of the neurotransmitter _______.
acetylcholine (ACh)
An ______ in the motor axon causes release of the neurotransmitter acetylcholine (ACh).
action potential
Muscle cells contain several long contractile units called _____ that are composed of sarcomeres linked end to end.
myofibrils
What is the current treatment for MH?
dantrolene
Each skeletal muscle cell of a mammal is innervated at _____, usually near _____.
one spot; the center of the cell
What is halothane?
a volatile anesthetic
In MH, the _____ from the SR activates the Ca+2 ATPase to pump Ca+2 back into the SR and a futile, heat-producing cycle occurs and is lethal if not corrected.
steady Ca+2 leak
How can skeletal muscle tension be graded?
1) increase freq of APs 2) recruit additional motor units 3) change the muscle length
F-actin makes up the ______.
thin filaments
An ______ in the SR causes a disease called malignant hyperthermia (MH).
abnormal calcium release channel
______ result from the stacking of sarcomeres in precise register across the width of the myofiber.
Striations
At the____, alpha-actinin is a molecule that crosslinks ______.
Z line; actin filaments
Muscles that perform fine movements tend to have _____ while large muscles that make gross movements have ______.
small motor units; large motor units
The myosin in _____ cycles about 20 times per second.
fast twitch muscle
The ______ are used for postural or relatively maintained contractions.
slow oxidative fibers
The thick filaments are 1.6 micrometers long and contain ______ myosins.
300-400
The myofilaments are bundled into _____.
myofibrils
Each troponin is bound to the end of one _____ molecules and induces a conformational change in the ______ that exposes the binding sites.
tropomyosin; tropomyosin
The myosin in slow twitch muscle cycles about ___ times per second.
5
In some cases FHC is due to mutations in ______.
troponin
The rate of myosin turnover is _____ in fast twitch muscle than in slow twitch muscle.
faster
The majority of people with FHC have mutations in the ______.
cardiac myosin heavy chain
The RyR (ryanodine receptor) is in the SR membrane and is a ______.
Ca release channel
The fast twitch fibers have high _____ content.
glycolytic
In ______, [Ca]i is low (
normal, relaxed muscle
Each myofibril is wrapped in its own ____.
SR
____ links the myosin thick filaments to the Z-line.
Titin
______ blocks muscle contraction by blocking Ca+2 release from the SR.
Dantrolene
Actin exists as either _____ (______) or ______ (___).
G-actin (globular-single units); F-actin (filamentous)
The rate of ______ is faster in fast twitch muscle than in slow twitch muscle.
myosin turnover
One of the subunits of the DHP receptor is a voltage-gated Ca channel; the other molecule is the ______.
RyR (ryanodine receptor)
_____ prevent the premature differentiation of satellite cells.
Fibroblasts
Smooth muscle contains no _____, but calcium is still the key regulatory molecule.
troponin
Depolarization of a muscle cell will open _____ and an action potential is initiated.
Na channels
The _____ is the cause of muscular dysgenesis.
DHP receptor
_____ is rod shaped and binds to 6-7 actin molecules of one strand.
Tropomyosin
As strength increases, the _____ of each cell is increased; new myofibrils are formed.
cross sectional area
The AChR is an ion channel that opens and causes ______.
depolarization
Titin links the _____ to the _____.
myosin thick filaments; Z-line
What is the mortality rate for MH?
10%
Binding of ATP allows _____ to dissociate from _____.
myosin; actin
Muscle cells contain several long contractile units called myofibrils that are composed of _____ linked end to end.
sarcomeres
What is the contractile unit of the muscle called?
myofibril
About _____ of all cases of sudden death due to cardiac arrest in young athletes are due to familial hypertrophic cardiomyopathy (FHC).
half
Increased calcium in the smooth muscle cell binds to _____ and this binds to CaM kinase and activates it so that one of the _____ on the myosin head is phosphorylated.
calmodulin; light chains
The _____ surrounds the entire muscle.
epimysium
Virtually all muscles are a mix of _____ but each motor unit is ______.
all three types of fibers; homogeneous
The _____ are bundled into myofibrils.
myofilaments
As soon as myosin binds, it exerts a force of about ____.
5 pN
