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Thick filaments in skeletal muscle are composed of
myosin
troponin
tropomyosin
calmodulin
actin
During isotonic contraction of a skeletal muscle fibre:
None of the above
A-bands shorten
Tension increases
Fibres relax
The sarcomere shortens
In skeletal muscle calcium facilitates contraction by binding to:
the thick filament
Motor unit’ refers to:
a single muscle fibre plus all the motor neurons that innervate it
all of the motor neurons supplying a single muscle
a pair of antagonistic muscles
a single motor neuron plus all the muscle fibres it innervates
all of the muscles that affect the movement of any given joint
During an isometric contraction of a skeletal muscle:
the I-bands shorten and the A-bands stay the same length
sarcomere length does not change
the thick and thin filaments slide past each other
tension does not change
none of the above
The cross bridge in the sacromere of skeletal muscle are made of:
myelin
With regard to knee jerk:
the Golgi body is an important component
it is a visceral reflex
the impulse travels via type Ca afferent fibres
the stimulus begins in the tendon
it is a monosynaptic reflex
The most important contractile proteins are:
all of the above
Which role do Ca2+ ions play in the muscle contraction?
prevent the contraction
excitation-contraction coupling
form cross bridges
excite the myofiber
release energy for the contraction
Smooth muscle is not cross striated because:
it has gap junctions
it is surrounded by a basal lamina
of myosin and actin in the myofibril
myofibrils are not in register with each other
myofibrils are in register with each other
lntercalated discs are most likely to be observed in:
longitudinal section of cardiac muscle
transverse section of smooth muscle
longitudinal section of skeletal muscle
transverse section of cardiac muscle
transverse section of skeletal muscle
During strong exercise, oxygen consumption is greatest in the:
skeletal muscles
brain
liver
kidneys
heart
An increase in force of a skeletal muscle contraction is initially achieved by:
recruitment of nerve fibers
increased intracellular calcium
recruitment of motor units
recruitment of muscle fibers
increased lactic acid
Which area of the sacromere consists only of myosin filaments?
H-zone
Z-disc
I-bands
A-bands
M-line
Which muscle cell compound stores oxygen?
myoglobin
creatine phosphate
lipid droplets
hemoglobin
glycogen
Smooth muscle is:
voluntary and spindle shaped
involuntary and spindle shaped
voluntary and striated
involuntary and striated
innervated by the somatic nervous system
Skeletal muscle ls:
innervated by ANS
Cardiac muscle is:
Which type of muscle cell is multinucleated?
Cardiac
Smooth
Cardiac and smooth
Skeletal
What is an example of a smooth muscle?
bladder
masseter (face)
rectus abdominis (belly)
pronator teres (forearm)
How many actin filaments surround each myosin filament?
seven
four
six
two
eight
The muscular system is controlled by which system?
the respiratory system
the urinary system
the nervous system
the endocrine system
the cardiovascular system
How many types of muscle are there?
three
five
The sacroplasmic reticulum stores:
calcium ions
chloride ions
sodium ions
hydrogen ions
potassium ions
Which of the following should affect the strength or force of skeletal muscle contraction?
the number of muscle fibers at rest
concentration of Na+
the degree of muscle stretch
the series-elastic elememts
stronger stimuli
Which of these is true of skeletal muscle:
forms the walls of hollow internal organs
many peripherally located nuclei per muscle fiber
may be autorhythmic
under involuntary control
spindle-shaped cells
Which of these is not a major property of muscle?
contractility
elasticity
extensibility
secretability
excitability
What is each myofibril made of?
contains sacroplasmic reticulum
is the same thing as a muscle fiber
many muscle fibers
contains T-tubules
many sacromeres
Myosin myofilaments are
attached to filaments that form the M-line
thinner than actin myofilaments
attached to the Z-disk
absent from the H zone
found primarily in the I band
The part of the sacrolemma that invaginates into the interior of skeletal muscle fibers is the
Sacroplasmic reticulum
T-tubule system
Terminal cisternae
Mitochondria
Myofibrils
Which of these events occurs during the lag (latent) phase of muscle contraction?
Active transport of Ca2+ into the sacroplasmic reticulum
Sacromere shortening
Ca2+ binding to troponin
Cross-bridge movement
Breakdown of ATP to ADP
Muscle contraction which cannot move weight because it is too heavy is:
isometric
eccentric
isotonic
isokinetic
concentric
Voluntary skeletal muscles in the leg are innervated
Somatic motor neurons
CNS fibers
Postganglionic neurons
All the above
Preganglionic neurons
A small motor unit would control which type of movement?
fast but brief
sprinting
intense and strong
delicate and precise
marathon running
Muscle fibers type 1 have only one of the following features:
a slow refractory period
easily fatigued
slow onset of contraction
low mitochondrial content
many enzyme for glycolysis
Muscle fibers type Ila are:
slow-twitch, oxidative, fatigue resistant
fast-twitch, oxidative-glycolytic, relatively fatigue resistant
fast-twitch, oxidative, fatigable
slow-twitch, glycolytic, fatigable resistant
fast-twitch, glycolytic, fatigable
Muscle fibers type IIb are:
Muscle fibers type 1 are
These bands of the sacromere do not shorten during contraction
A bands
H, I and M bands
Z discs and A bands
I bands
a and d
The role of transverse tubules in skeletal muscle fibers is to:
connect the sacrolemma to the sacroplasmic reticulum
spread the action potential quickly
bind the myofibrils
bind to the receptors- dihydropyridine receptors
connect the sacromeres to each other
The cross bridges of the sarcomere in skeletal muscle are components of:
titin
The function of tropomyosin in skeletal muscle In
sliding on actin to produce shortening
binding to myosin during contraction
releasing Na+ after contraction
covering up the actin binding sites of myosin at rest
releasing Ca2+ after initiation of contraction
The cell membranes In skeletal muscle:
become more permeable to glucose in the presence of insulin
are ligand dependent
are impermeable to fat-soluble substances
are more permeable to sodium than to potassium ions
become less permeable to potassium in the presence of insulin
A skeletal muscle fibre at rest:
is normally innervated by more than one motor neuron
becomes more excitable as its resting membrane potential increase in absolute value
contains intracellular stores of calcium ions
becomes less excitable as the extracellular ionized calcium levels fall
presents with a membrane which is positively charged on the inside with respect to the outside
In skeletal muscle:
contraction occurs when its pacemaker cells depolarize sufficiently to reach the threshold for firing
contraction strength is related to the influx of K+ ions
actin and myosin filaments shorten when it contracts
calcium is taken up by the sarcotubular system when it contracts
the sarcomeres shorten during contraction
Visceral smooth muscle differs from skeletal muscle in that
excitation depends more on influx of extracellular calcium than release of calcium from endoplasmic reticulum
its cells have unstable resting membrane potentials
it is not paralyzed when its motor nerve supply is cut
it contracts when stretched
A property shared by:
skeletal and cardiac ventricular muscles is their stable resting membrane potential
all types of muscles is that contraction strength is related to their initial length
cardiac and visceral smooth muscles is their spontaneous activity when denervated
skeletal and cardiac muscles is their striated microscopical appearance
The action potential of skeletal muscle:
is longer than the action potential of cardiac muscle
is not essential for muscle conduction
has a prolonged plateau phase
has different amplitudes
spreads inwards to all parts of the muscle via T tubules
Smooth muscle need help of:
secondly molar for contraction
monoamine oxidase for contraction
K+ for contraction
calmodulin for contraction
acetyl choline for contraction