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