Dr Gawad Physiology Course Online Exam - Excitable – Course Lecture 4, 5, 6
12 MCQs (Only one correct answer)
Each MCQ: 1 mark, Total mark: 12
Allowed time: 13 min
Good Luck
dr Mohammed Abel Gawad
- 1.
In the motor end plate, all the following are TRUE EXCEPT:
- A.
The acetylcholine receptors are similar to those in smooth muscle.
- B.
The nerve ending contains many vesicles and mitochondria.
- C.
Lack of Ca diminishes the release of acetylcholine.
- D.
There is a high concentration of the cholinesterase enzyme.
- E.
There is a delay of neuromuscular transmission of 0.5 millisecond
Correct Answer
A. The acetylcholine receptors are similar to those in smooth muscle. -
- 2.
About neuromuscular transmission and end plate potential (EPP):
- A.
Neuromuscular transmission occurs only from the muscle to the nerve.
- B.
EPP is always maximal and rapidly conducted along the surface of the muscle.
- C.
EPP is a localized state of depolarization at the motor end plate.
- D.
EPP is augmented by increased Mg concentration in ECF.
- E.
EPP is associated with decreased excitability of the motor end plate.
Correct Answer
C. EPP is a localized state of depolarization at the motor end plate. -
- 3.
About activation of skeletal muscles, all the following is true except:
- A.
The resting membrane potential is about -90 mV.
- B.
The magnitude of the action potential is more than that in nerves.
- C.
The firing level is reached after about +40 mV of depolarization.
- D.
The spike is propagated along the muscle surface at a speed of 5 m /second.
Correct Answer
C. The firing level is reached after about +40 mV of depolarization. -
- 4.
The action potential of skeletal muscles:
- A.
Has a prolonged plateau phase.
- B.
Has a smaller magnitude than that of smooth muscles.
- C.
Causes uptake of Ca into the lateral sacs of the sarcoplasmic reticulum.
- D.
Spreads inwards to all parts of the muscle fibre via the T-tubules.
- E.
Is not essential for contraction.
Correct Answer
D. Spreads inwards to all parts of the muscle fibre via the T-tubules. -
- 5.
Neuromuscular transmission:
- A.
Is caused by release of acetylcholine from the muscle side.
- B.
Shows a permeability change to Na+ at the receptor side of the neuro-muscular junction
- C.
Can be facilitated by curare.
- D.
Is blocked by curare because it competes with Na+ influx at the M.E.P.
Correct Answer
B. Shows a permeability change to Na+ at the receptor side of the neuro-muscular junction -
- 6.
The neurotransmitter at the motor endplate is:
- A.
Adrenaline.
- B.
Noradrenaline.
- C.
Acetyl choline.
- D.
Calcium ions.
- E.
Atropine.
Correct Answer
C. Acetyl choline. -
- 7.
During neuromuscular transmission:
- A.
Ca++ enters through synaptic cleft.
- B.
Ach is released from synaptic cleft.
- C.
There is a delay of about 5 milliseconds.
- D.
The impulse is transmitted in one direction.
Correct Answer
D. The impulse is transmitted in one direction. -
- 8.
During muscle contraction, all the following is true except:
- A.
The binding sites at the actin filaments are activated by Ca.
- B.
The sliding filament theory of contraction assumes that sliding of actin continues as long as Ca is attached to troponin C
- C.
The detachment of myosin heads from actin needs binding of ATP.
- D.
The transverse tubules (T.T.) contains Ca voltage gated channels
Correct Answer
D. The transverse tubules (T.T.) contains Ca voltage gated channels -
- 9.
About the of skeletal muscles, all the following is true except:
- A.
Hypertrophy develops as a result of forced repeated contractions.
- B.
The function of the T system is the rapid transmission of the action potential from the cell -membrane to inside the muscle fibre
- C.
After the spike potential, the muscle excitability is abolished
- D.
Acetylcholine released at the M.E.P. is rapidly hydrolyzed by cholinesterase.
Correct Answer
C. After the spike potential, the muscle excitability is abolished -
- 10.
Among the steps of skeletal muscle relaxation:
- A.
Inward spread of the depolarization wave along the transverse tubules.
- B.
Pumping of Ca back into the sarcoplasmic reticulum.
- C.
Release of Ca from the sarcoplasmic reticulum.
- D.
Binding of Ca to troponin C.
Correct Answer
B. Pumping of Ca back into the sarcoplasmic reticulum. -
- 11.
Concerning isometric and isotonic muscle contractions:
- A.
In isometric contraction, the elastic elements are not stretched.
- B.
During isometric contraction a load is moved and work is done.
- C.
During isotonic contraction most of the energy transformed into heat.
- D.
During isotonic contraction the muscle length is not changed.
Correct Answer
C. During isotonic contraction most of the energy transformed into heat. -
- 12.
In skeletal muscles:
- A.
The initiation of contraction occurs by binding of Ca to tropomyosin.
- B.
The action potential follows the work done.
- C.
The one way conduction at the M.E.P. is due to location of the chemical mediator (acetylcholine) in the nerve terminals.
- D.
Fatigue sets in after fatigue occurs in the nerves.
Correct Answer
C. The one way conduction at the M.E.P. is due to location of the chemical mediator (acetylcholine) in the nerve terminals. -
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