Waec Model Questions Vol1 2019 Biology Question 8

Practice essay / theory question 8 from the 2019 Waec Model Questions Vol1 Biology examination. This question covers coordination, nervous system, reflex arc .

Waec Model Questions Vol1 2019 Biology Essay / Theory
Topics: coordination nervous system reflex arc
Question 8 WAEC_MODEL_QUESTIONS_VOL1 • 2019 • BIOLOGY • essay
Waec Model Questions Vol1 2019 Biology Question 8 diagram

The diagram shows a simple spinal reflex arc that mediates the withdrawal response of a hand when it contacts a painful stimulus. The labelled parts are: A – sensory receptor, B – sensory (afferent) neuron, C – interneuron in the spinal cord, D – motor (efferent) neuron, E – skeletal muscle (effector), and F – synaptic junctions. The linear distances between successive parts are AB = 30 cm, BC = 10 cm and CD = 20 cm.

Question Parts

( a )
Identify each labelled part in the diagram and state its primary function in the reflex arc.
( b )
Explain, in order, the sequence of events that occur from the moment the receptor is stimulated until the muscle contracts.
( c )
If the conduction velocity of the sensory neuron is 80 m·s⁻¹, that of the motor neuron is 60 m·s⁻¹ and the synaptic delay at each junction is 0.5 ms, calculate the total time taken for the reflex response (from receptor activation to muscle contraction). Show all steps.
( d )
Discuss how demyelination of the sensory neuron would affect the reflex time calculated in part (c) and the possible clinical implications of such a change.

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About This Question

This is Waec Model Questions Vol1 2019 Biology Question 8. It is one of the essay questions from the 2019 Waec Model Questions Vol1 Biology examination.

The question covers coordination, nervous system, reflex arc .

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