The pressure-flow model, first proposed by Ernst Münch, Phloem loading at the source and phloem unloading at the sink establish the pressure gradient.

a.) In source tissues, an accumulation of sugars in the sieve elements generates a lower or negative solute potential (ψs).

 b.) source tissue, causes a steep drop in the water potential (ψ), due to water potential gradient, water enters the sieve elements and causes turgor pressure (ψp ) decrease.

c.) In sink tissues, phloem unloading leads to a lower sugar concentration in the sieve elements, generating a higher or less negative solute potential.

d.) As the water potential of the phloem rises above that of the xylem, water tends to leave the phloem in response to the water potential gradient, causing a decrease in turgor pressure in the sieve elements of the sink.

Which of the following statements of sink and source tissue is FALSE?

#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?

#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: 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: 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: 11224

#Unit 7. System Physiology – Animal

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

#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?