The Norway rat (Rattus Norvegicus), a widespread pest, was controlled for about a decade by the anticoagulant warfarin. This chemical substance, placed in food pellets, is absorbed by the intestinal tract and inhibits the clotting of blood. After a population decline for about 10 years, rat populations increased and stabilized. In one European population, as illustrated in the graph below, the percentage of rats resistant to warfarin has remained fairly stable over a number of years.

Resistance to warfarin is governed by a dominant autosomal gene, R. More than 15 percent of the resistant animals are heterozygous at this locus (Rr). The table below indicates the response to warfarin and relative reproductive fitness of individuals that are homozygous or heterozygous for the dominant gene (R). The RR individuals have a 20-fold increase in vitamin K requirement over individuals.

Fitness is a measure of the reproductive success of a particular genotype. The highest fitness is 1.00.

Which of the following is most likely correct concerning the gene for resistance to warfarin? 

#Question id: 11223

#Unit 7. System Physiology – Animal

Of those listed, which event occurs first following a depolarizing stimulus applied to the presynaptic membrane of an axon terminal?

#Question id: 11224

#Unit 7. System Physiology – Animal

How could you increase the magnitude of excitatory postsynaptic potentials (EPSPs) generated at a synapse?

#Question id: 11225

#Unit 7. System Physiology – Animal

What happens if twice as many inhibitory postsynaptic potentials (IPSPs) as excitatory postsynaptic potentials (EPSPs) arrive in close proximity at a postsynaptic neuron?

#Question id: 11226

#Unit 7. System Physiology – Animal

At the neuromuscular junction, the neurotransmitter acetylcholine (ACh) is degraded by acetylcholinesterase. If a neurophysiologist applies the naturally occurring acetylcholinesterase inhibitor, onchidal (produced by the mollusc Onchidella binneyi), to a synapse, what would you expect to happen?

#Question id: 11495

#Unit 7. System Physiology – Animal

In a neuron with a resting membrane potential of −65mV, the distribution of which ion across the neuronal membrane represents the greatest potential electromotive force (EMF)?

#Question id: 11496

#Unit 7. System Physiology – Animal

Forced rapid breathing results in alkalization of the blood which would lead to which of the following changes in neuronal activity?