Transmission of a nerve impulse is unidirectional.
Transmission of a nerve impulse is unidirectional because synapses are valvular in their action, transmitting the impulses only in one direction, which is always from the axon of one neuron to the cell body of the next neuron and never in the reverse direction.
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33.
Draw a labelled diagram of the transverse section of the hyaline cartilage.
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34.Give four differences between a bone and cartilage.
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35.Describe the carbonic acid exchange theory for absorption of mineral salts by plants.
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36.What are growth regulators ? Explain the role played by auxins in phototropic responses in plants.
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37.
Give two differences each between :
(i) Active absorption and Passive absorption
(ii) Transpiration and Guttation.
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38.
Diagrammatically show the components of a reflex arc. (Use arrows to indicate the flow of impulse)
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39.Write an account of the chemical events taking place during muscle contraction.
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40.What are the functions of the placenta in mammals ?