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WorksheetsMuscles
Total questions: 23
Worksheet time: 25mins
Put the following stages of neuromuscular transmission into the correct temporal sequence
1. Ach diffuses across the cleft
2. voltage-gated Ca2_ channels in axon terminal open
3. generation of end-plate potential
4. reabsorption of choline by axon terminal
5. binding of Ach to receptors on sarcolemma
1,5,3,4,2
2,1,3,4,5
2,1,5,3,4
1,5,4,3,2
5,4,2,1,3
Which of the following statements about thick filaments is/are TRUE?
1. thick filaments are in the order of 12-18 nm in diameter
2. thick filaments are around 1.6 microns in length
3. each thick filament is made up of a large number of molecules of the protein myosin all packed togeher
2 & 3
2 only
1, 2 & 3
3 only
1 only
A number of muscle fibres collected together by a connective tissue sheath are known as which of the following?
tendon
motor unit
sarcolemma
fascicle
fibula
The motor-end plate is the name given to which of the following?
group of myofibrils immediately below the neuromuscular junction
region where motoneurone axon terminal loses its myelin sheath
cover that seals the drive shaft on a Holden Commodore
part of neuromuscular junction that is closest to motoneurone soma
region where motoneurone axon terminal and sarcolemma are in close apposition
Which of the following statements concerning the structure of a myofibril is/are TRUE?
1. the distance between the two bands is known as the sarcomere
2. the dark bands are caused by thin filaments and the light bands by the thick filaments
3. the Z line is caused by the junction between successive blocks of thick filaments
1 only
1, 2 & 3
1 & 2
2 & 3
2 only
Which of the following statements about skeletal muscle is/are TRUE?
1. under the light microscope skeleta muscle appears striated
2. alternating dark and light bands are caused by highly ordered arrangement of thin and thick filaments within myofibril
3. dark bands known as I bands, light bands as A bands and thin line which is sometimes observed splitting I bands is known as Z lines
1, 2 & 3
2 & 3
1 & 2
2 only
1 only
Which of the following statements is/are TRUE?
1. thin filaments are in the order of 5-8 nm in diameter
2. thin filaments are around 1 micron long
3. thin filaments contain two chains of myosin which are twisted around each other to form a double helix
2 & 3
1 & 2
2 only
1 only
1, 2 & 3
If a muscle was found to have 90 muscle fibres innervated by each motoneurone, it would probably be involved in which of the following types of movement?
stabilisation of the ear ossicles during hearing
lower leg extension during kicking a football
upper arm flexion while tossing the caber
movement of the eyeball during reading
movement of the thumb whilst writing
Which of the following structures are typically 1-2 microns thick?
myofibrils
transverse tubules
muscle fibres
thin myofilaments
sarcolemma
An end-plate potential is the direct consequence of which of the following?
flow of Na+ into the cell and K+ out of the cell
opening of ligand-gated Ca2+ channels in motoneurone axon terminal
flow of Na+ out of cell and K+ into cell
binding of Ach to muscarinic Ach receptors
Which of the following is NOT a feature of a muscle fibre at rest?
interactions between the myosin cross-bridges and actin thin filaments are prevented by tropomyosin filaments
myosin cross-bridges have been "primed" by the breakdown of ATP by ATPase present on cross bridges
sarcoplasmic Ca2+ concentration is very low
ADP produced by hydrolysis of ATP remains bound to ATPase on cross-bridge
endoplasmic reticulum concentration of Ca2+ is very low
Which of the following statements about the sliding filament mechanism of muscle contraction is FALSE?
cross-bridge cycle is repeated many times following just a single AP
a single AP causes a shortening of around 1% of the length of sarcomere
shortening of myofibril is active
lengthening of myofibril is passive
one cross bridge cycle only decreases sarcomere length by 20 nm
Which of the following statements about rigor mortis is TRUE?
the stiffness which skeletal muscles exhibit 2-3 days after death
due to failure of Ca2+ to bind to troponin complex and displace tropomyosin filament
partly due to leakage of Ca2+ into endoplasmic reticulum
due to absence of ATP which is required to bind to cross bridges and detach thick filaments from thin
lasts about 4 hours
Ach release from axon terminals of motoneurones is initiated by which of the following?
presence of APs in muscle fibre
opening of voltage-gated Ca2+ channels
opening of ligand-gated Ca2+ channels
endocytosis
release of Ca2+ from sarcoplasmic reticulum
The thin myofiliament protein that physically blocks the myosin binding sites on each molecule of actin whilst a muscle fibre is at rest is called?
tropomyosin
myosin
toponin
trypsin
troponin complex
Which of the following statements about motoneurones is/are TRUE?
1. they have their cell bodies in the posterior horns of the spinal cord.
2. they have myelinated axons.
3. they have axons which do not branch.
4. they usually form a contact with one muscle fibre.
1 only
1, 2 & 3
1, 2 & 4
1 & 2
2 only
Which of the following statements about skeletal muscle contraction is/are FALSE?
1. force generated during a muscle contraction is independent of the number of motor units recruited
2. during an isometric contraction the muscle produces tension but the length of the muscle does not change
3. during an isotonic contraction the length of the muscle decreases but he tension remains the same
1 only
2 only
1 & 2
3 only
1, 2, 3
In a myofibril, actin binding sites and an ATPase are normally found on the?
cross-bridges of thick filaments
tropomyosin
troponin complex
cross-bridges of thin filaments
double helix of actin
The troponin complex contains three polypeptides which have binding sites for which of the following?
1. tropomyosin.
2. actin
3. Ca2+
2 only
2 & 3
1 only
1, 2 & 3
3 only
Which of the following statements concerning muscle contraction is FALSE?
1. If a second action potential arrives in a muscle fibre before the tension generated by the first action potential has declined, then the two will summate to produce a larger twitch.
2. A Titanic contraction is where increasing the action potential frequency even more produces no further increase in the tension produced.
3. The maximal force which can be generated is usually is around the normal resting length of the muscle.
2 only
1 only
1, 2 & 3
3 only
2 & 3
Which of the following structures contains a fluid which is most like extracellular fluid?
transverse (T) tubules
sarcoplasm
mitochondria
motoneurones
myofibrils
Which of the following would you NOT expect to find at the mammalian neuromuscular junction?
acetylcholinesterase
muscarinic acetylcholine receptors
Schwann cells
voltage-gated Ca2+ channels
synaptic vesicles containing the neurotransmitter acetylcholine
Which of the following is the CORRECT sequence of events according to the sliding-filament mechanism?
1. Energy released from the breakdown of the ATP is used to return the cross bridge to its "primed" position.
2. Binding of the cross bridges to the thin filaments triggers the cross bridges to flick.
3. Ca2+ binds to the calcium binding sites on the troponin complex.
4. Movement of the tropomyosin filament exposes the myosin binding sites on the actin molecules.
5. Cross-bridges detach from the thin filaments.
3, 4, 2, 5, 1
3, 2, 4, 5, 1
3, 4, 2, 1, 5
4, 3, 2, 5, 1
3, 5, 2, 4, 1
