Dr Gawad Physiology Course Online Exam - Excitable – Course Lecture 5 – Neuromuscular Junction

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Questions: 6 | Attempts: 579 | Updated: Mar 21, 2023

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Dr Gawad Physiology Course Online Exam - Excitable Course Lecture 5 Neuromuscular Junction - Quiz

Dr Gawad Physiology Course Online Exam - Excitable – Course Lecture 5 – Neuromuscular Junction
6 MCQs (Only one correct answer)
Each MCQ: 1 mark, Total mark: 6
Allowed time: 6 minGood Luckdr Mohammed Abdel Gawad

Questions and Answers

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.

Explanation
The motor end plate contains a high concentration of acetylcholine receptors that are specific to skeletal muscle, not smooth muscle. Smooth muscle has different types of receptors. Therefore, the statement that the acetylcholine receptors in the motor end plate are similar to those in smooth muscle is false.

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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.

Explanation
The correct answer is EPP is a localized state of depolarization at the motor end plate. This is because EPP refers to the depolarization of the motor end plate, which is the specialized region of the muscle fiber where the nerve terminal makes contact. It is a localized event that occurs specifically at the motor end plate and is crucial for initiating muscle contraction. The other statements mentioned in the question are incorrect or unrelated to the concept of EPP.

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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.

Explanation
The firing level is reached after about +40 mV of depolarization.

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4.

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

Explanation
The correct answer explains that neuromuscular transmission shows a permeability change to Na+ at the receptor side of the neuro-muscular junction. This means that when a nerve impulse reaches the neuromuscular junction, the receptor site on the muscle cell membrane becomes permeable to Na+ ions, allowing them to enter the cell. This influx of Na+ ions triggers a series of events that ultimately leads to muscle contraction. This explanation highlights the key mechanism involved in neuromuscular transmission and how it is related to the permeability change to Na+ ions.

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5.

The neurotransmitter at the motor endplate is:
- A.
  
  Adrenaline.
- B.
  
  Noradrenaline.
- C.
  
  Acetyl choline.
- D.
  
  Calcium ions.
- E.
  
  Atropine.
Correct Answer
C. Acetyl choline.

Explanation
The correct answer is acetyl choline because it is the primary neurotransmitter responsible for transmitting signals from motor neurons to muscle fibers at the neuromuscular junction. Acetylcholine binds to receptors on the motor endplate, causing muscle contraction. Adrenaline and noradrenaline are not directly involved in muscle contraction, while calcium ions play a role in muscle contraction but are not neurotransmitters. Atropine is a medication that blocks the effects of acetylcholine and is not the neurotransmitter itself.

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6.

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.

Explanation
During neuromuscular transmission, the impulse is transmitted in one direction. This is because the release of Ach (acetylcholine) from the synaptic cleft triggers an action potential in the muscle fiber, causing muscle contraction. The impulse can only travel from the presynaptic neuron to the postsynaptic neuron, ensuring that the muscle contracts in response to the signal and preventing any backward transmission of the impulse. This unidirectional transmission is crucial for proper muscle function and coordination.

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Current Version
Mar 21, 2023

Quiz Edited by
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Mar 06, 2018

Quiz Created by
Gawad

Dr Gawad Physiology Course Online Exam - Excitable – Course Lecture 5 – Neuromuscular Junction

In the motor end plate, all the following are TRUE EXCEPT:

About neuromuscular transmission and end plate potential (EPP):

About activation of skeletal muscles, all the following is true except:

Neuromuscular transmission:

The neurotransmitter at the motor endplate is:

During neuromuscular transmission: