MCAT Psychology and Sociology Practice Test 2: biological foundations of behavior

Home > MCAT Test > MCAT behavioral sciences practice tests

Test Information

Question 7 questions

Time minutes

See All test questions

Take more free MCAT behavioral sciences practice tests available from

Long-term potentiation (LTP) involves communication between two neurons and is a major cellular mechanism underlying learning and memory processes. During LTP, a presynaptic neuron releases the neurotransmitter glutamate, which binds to receptors on the postsynaptic neuron. This leads to an influx of sodium, and ultimately calcium, followed by activation of various genes (see Figure 1). The initial receptor activated by glutamate is the AMPA receptor; the NMDA receptor is blocked by extracellular Mg2+ that must be displaced by a sufficient change in membrane potential before that channel will fully open.

LTP has been shown to be disrupted in neurodegenerative disorders, such as Alzheimer's disease, leading to memory deficits. In brains of Alzheimer's patients, loss of vital neurons occurs in the hippocampus (a region of the brain involved in memory acquisition). Several mechanisms are hypothesized to lead to this neurodegeneration. One involves calcium-mediated toxicity and occurs due to excessive glutamate-induced neuronal excitation.

Another potential contributing factor to this cell loss is exposure to chronic stress, which results in elevated levels of corticosteroids that can influence neuronal activity in the brain. This has led to the formation of the "Glucocorticoid Hypothesis of Aging." The intact hippocampus has an inhibitory effect on the stress axis (hypothalamic-pituitary-adrenal axis) that is responsible for inducing release of cortisol from the adrenal gland during times of stress. Thus, if the hippocampal region is compromised, it could lead to lack of inhibition of the stress axis and further release of cortisol, causing a feed-forward cycle of excessive release of steroids with each stressful event.

Figure 1 Synaptic Transmission During LTP

1. In which region of the brain is the hippocampus located?

  • A. Cerebellum
  • B. Occipital lobe
  • C. Temporal lobe
  • D. Hypothalamus

2. One treatment for Alzheimer's disease involves a drug that blocks NMDA receptors. This treatment could lead to all of the following EXCEPT:

  • A. a suppression of LTP.
  • B. a suppression of gene expression.
  • C. a significant decrease in intracellular sodium.
  • D. a significant decrease in intracellular calcium.

3. A researcher removes the adrenal glands from a rat and then supplements the rat with baseline levels of steroids for the remainder of its lifespan. Which of the following would be expected?

I. Blunted sympathetic nervous system response

II. Slowing of age-related neurodegeneration

III. Enhancement of LTP

  • A. II only
  • B. II and III
  • C. I and II
  • D. I, II and III

4. Which of the following statements is LEAST likely to be true?

  • A. Drugs that increase Cl influx into the postsynaptic cell could disrupt LTP.
  • B. Drugs that increase K+ efflux from the postsynaptic cell would result in hyperpolarization of the cell and would increase LTP.
  • C. The insertion of new AMPA receptors in the postsynaptic cell membrane would increase the rate at which Mg2+ is displaced from NMDA receptors upon subsequent stimulation by glutamate.
  • D. The influx of Na+ upon initial stimulation by glutamate depolarizes the postsynaptic cell in order to displace Mg2+.

5. AMPA receptors are found throughout the central nervous system and are comprised of four different subunits. Not all AMPA receptors have all the subunits. If a knockout mouse was made deficient for the gene for one of the AMPA receptor subunits, what would be the expected outcome?

  • A. An observed deficit only in LTP and the mouse's ability to learn.
  • B. Altered function in any region containing an AMPA receptor.
  • C. No change in LTP function due to the NMDA receptor still being present and functional.
  • D. Altered function and/or compensatory expression of other AMPA receptor subunits in regions with AMPA receptors that lack the affected subunit.

6. Based on Figure 1, what is a logical function of CREB?

  • A. Interact with the genomic DNA to enhance transcription
  • B. Interact with RNA to enhance translation
  • C. Bind ribosomes to enhance transcription
  • D. Bind RNA polymerase to enhance replication

7. Symptoms of Alzheimer's disease include all of the following EXCEPT:

  • A. disorientation.
  • B. forgetfulness.
  • C. mood swings.
  • D. slow, uncoordinated fine movements.