11. Which statement is false? A. Nervous tissue and \"classical\" endocrine tiss

Question

11. Which statement is false? A. Nervous tissue and "classical" endocrine tissue are both derived from primordial ectoderm during embryonic development. B. Both neurotransmitters and hormones must remain active for several minutes in a synapse or in target tissue in order to stimulate an action potential or cause a cellular reaction. C. Norepinephrine is both a hormone and a neurotransmitter, depending on whether it is released at a synapse or secreted from the adrenal medulla. D. Neurotransmitters, as well as some hormones- especially the sex steroids- can cause a change in the resting membrane potential of a neuron.

Explanation / Answer

Option B is the correct answer. Neurotransmitters must remain active for several minute in a synapse in order to stimulate an action potential because after release of neurotransmitter in synaptic cleft it must interact with postsynaptic receptors. After interaction with receptors, depolarization occurs which opens the post synaptic membrane. The depolarization takes few miliseconds to several minutes. Hormones, once reaches to its target it binds with it receptors which brings a cascade of intracellular changes and cellular reaction occurs. Thus, hormones must be active for long time in circulation to reach the target but once it reaches the targets it does not take time to bring the cellular response.

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