1. Which one of the following is not a general characteristic of postsynaptic po
ID: 260458 • Letter: 1
Question
1. Which one of the following is not a general characteristic of postsynaptic potentials?
A. Postsynaptic potentials have longer refractory periods than action potentials.
B. Postsynaptic potentials decrease in amplitude with distance away from the synapse.
C. Postsynaptic potentials are produced by neurotransmitter molecules binding to chemically-gated channels.
D. Postsynaptic potentials produced near the axon hillock have a stronger effect on action potential generation than those produced in the dendrites.
2. Which one of the following statements about the human placenta is false?
A. Maternal blood is circulated through large sinuses in the placenta.
B. The umbilical artery and vein carry fetal blood.
C. The secretion of estrogen and progesterone by the placenta is less important during the first 3 months of gestation.
D. The placenta is capable of higher levels of estrogen and progesterone secretion than the corpus luteum.
E.There is direct exchange of maternal and fetal blood in the placenta.
Explanation / Answer
1. Chemical synapses are junctions between two neurons through which signals can be exchanged with each other and to non-neuronal cells such as muscles or glands.These synapses include Presynaptic and Postsynaptic ends. Postsynaptic potentials are changes in the membrane potential of the postsynaptic terminal of a chemical synapse. Presynaptic neuron releases neurotransmitters from its terminus at the end of an axon into the synaptic cleft. The neurotransmitters bind to receptors on the postsynaptic terminal, which may or may not be a neuron. Postsynaptic potentials are graded potentials and graded potentials are not associated with the refractory period. Hence the correct answer to this question is, option A. Postsynaptic potentials have longer refractory periods than action potentials.
2. The umbilical vein in the placenta carries oxygenated, nutrient-rich blood of the mother from the placenta to the fetus, and the umbilical arteries carry deoxygenated nutrient-depleted blood. which is also the mother's blood, from the fetus to the placenta. The placenta's one of the important jobs is that it should not allow the maternal and fetal blood to mix and allow the exchange of nutrients between them. So, the correct answer to this question is B. The umbilical artery and vein carry fetal blood. (Which is false)
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