UNIVERSITI TUNKU ABDUL RAHMANCENTRE FOR FOUNDATION STUDIES

FOUNDATION IN SCIENCEJAN 2016

FHSB1224 BIOLOGY II

TUTORIAL 3 NERVOUS SYSTEM II

Instructor’s Guide:1. Standard answers are not encouraged. Discuss with the students and lead them to the

correct answer. 2. Allow and push the students to express and explain the answers, at the same time,

correct their mistakes or concepts.3. If the tutorial questions are not yet covered in the lecture, it should be carried forward

to the next tutorial.

Student’s Guide:At university level, the tutor facilitates student learning without spoon-feeding. Therefore, you are expected to:

Read your textbook, attempt the questions before the tutorial You may enter the class and sign your attendance after showing your tutor that all

tutorial questions have been completed; even if you don’t know how to do, write something - you’re not advised to leave answers blank in the finals.

Write answers on board if you wish to receive tutor feedback (no answer, no feedback)

Be independent: consult textbooks or dictionaries on your own first before asking the tutor

All questions are compulsory. 1 mark may reflect 1 answer point. (No half mark is awarded in the finals marks)

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(May 2015)Q1. Figure 1 illustrates the mechanism of impulse transmission in a synapse.

Figure 1

(a) With the help of Figure 1, relate the role of synapse and neurotransmitters in an impulse transmission. (4 marks)

(b) Name TWO (2), categories of membrane potential that are important for the occurrence of muscle contraction. (2 marks)

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(Jan 2015)Q2. (a) Botulinum toxin A (BTX A) is a very powerful neurotoxin which has the

ability to bind to the acetylcholine (ACH) receptor. When injected in minute amounts into muscle, a temporary local paralysis of the muscle will occur. Figure 2.1 below shows the action of BTX A at the neuromuscular junction.

Figure 2.1

Based on Figure 2.1, explain how BTX A would cause temporary paralysis of muscle. (4 marks)

(b) Figure 2.2 shows a synaptic transmission of signal.

Figure 2.2

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(i) Describe the mechanism of transmission shown. (4 marks)

Q3. (a) Figure 3.1 shows the changes in potential difference across an axon membrane when action potential is generated in a nerve cell.

Figure 3.1

(i) Explain the formation of curve labelled A as shown in Figure 3.1. (3 marks)

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(ii) The local anaesthetics lidocaine (xylocaine) and procaine (novocaine) prevent voltage-gated Na+ channels from opening. Explain how this could block the conduction of pain signals in sensory nerves. (3 marks)

(iii) A neuron receives a stimulus that by itself can bring the neuron threshold, but no action potential is produced at the postsynaptic neuron. Explain what could cause this to happen. (3 marks)

(iv) Organophosphates can combine with enzyme acetylcholinesterase which can lead to continuous, uncontrolled muscle contractions. Explain briefly how this could happen. (4 marks)

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