Prelim 3

Question 1

The resting potential of nerve cells…

A. is more negative than the potassium equilibrium potential but less negative than threshold
B. is not influenced by Na+/K+ ATPase activity
C. is affected by the insulating property of myelin
D. is determined by the Nernst potentials of Na+, K+, and Cl-, as well as their permeabilities
E. is typically about 0 mV

Answer 1

D. is determined by the Nernst potentials of Na+, K+, and Cl-, as well as their permeabilities

Question 2

Which of the following pairs correctly describe an aspect of an action potential (AP)?
A. Chemical driving force on sodium – rising phase of the AP
B. Voltage-gated sodium channels reach threshold – voltage-gated potassium channels immediately open
C. Start of the undershoot of the AP – voltage-gated potassium channels are closed
D. Voltage-gated potassium channels – axon hillock membrane
E. Rising phase of the AP – active excitation of neighboring voltage-gated sodium channel

Answer 2

E. Rising phase of the AP – active excitation of neighboring voltage-gated sodium channel

Question 3

A ______ channel on the ______ of a neuron that allows the flow of ______ will cause an ______ that spreads ______.

A. ligand-gated; axon terminal; calcium; IPSP; actively
B. ligand-gated, dendrites, sodium, EPSP, passively
C. voltage-gated; dendrites; potassium; IPSP; actively
D. voltage-gated; axon; potassium; EPSP; actively

Answer 3

B. ligand-gated, dendrites, sodium, EPSP, passively

Question 4

Which of the following is NOT associated with synaptic plasticity?

A. Tetanic stimulation
B. Insertion of more AMPA receptors
C. Facilitation
D. Temporal summation
E. Depolarization of NMDA receptors

Answer 4

D. Temporal summation

Question 5

Which of the following plays the key role in determining whether a synapse is inhibitory or excitatory?

A. The identity/properties of the neurotransmitter released by the presynaptic cell
B. The concentration of calcium inside and outside the cell
C. The identity of the transmitter and properties of the receptors on the post-synaptic cell
D. The amount of transmitter released into the cleft
E. Whether the synapse is electrical or chemical

Answer 5

C. The identity of the transmitter and properties of the receptors on the post-synaptic cell

Question 6

Which of these pairings about synapses is correct?

A. Electrical synapse – uses G-protein coupled receptor (GPCR)
B. Chemical synapse – faster than electrical synapses
C. Ligand-gated receptor – made of connexins
D. Ionotropic receptor – is a channel
E. Chemical synapse – neurotransmitter is taken up by the post-synaptic neuron

Answer 6

D. Ionotropic receptor – is a channel

Question 7

Which of the following statements about cortical magnification is correct?

A. Folding of the cortical surface provides more processing area
B. More neurons process touch information than process visual information
C. Some lobes of the cerebral cortex are larger than others
D. More neurons process some specific attribute of a sensory modality than other attributes

Answer 7

D. More neurons process some specific attribute of a sensory modality than other attributes

Question 8

Which of the following statements is NOT an example of the ambiguity of receptor responses?

A. a single cone cell can differentiate wavelengths only within its sensitivity range
B. an olfactory receptor cell can give the same response to different odors
C. hair cells in the inner ear confound sound frequency (tone) and loudness
D. skin receptors fail to distinguish the location in the receptive field (RF) from the strength of the touch
E. a sweet taste cell responds with the same magnitude graded potential to different sugar molecules

Answer 8

A. a single cone cell can differentiate wavelengths only within its sensitivity range

Question 9

Which of these statements about sensory receptors is correctly paired?

A. hearing hair cell – chemosensory tip links
B. umami taste cell – Na+ channel propagates a graded potential
C. finger touch cell – stretch-sensitive channel propagates an action potential
D. rod – epithelial cell with GPCR and vitamin A propagates action potential in optic nerve
E. olfactory cell – GPCR on epithelial cell propagates action potential

Answer 9

C. finger touch cell – stretch-sensitive channel propagates an action potential

Question 10

What physiological mechanism explains how higher-order neural circuits refine ambiguous receptor signals to enhance sensory discrimination?

A. Increasing the amplitude of graded potentials in receptor cells.
B. Amplifying neurotransmitter release from receptors.
C. Using frequency coding rather than amplitude coding to sharpen a signal.
D. Lateral inhibition between different receptors in a center-surround circuit.

Answer 10

D. Lateral inhibition between different receptors in a center-surround circuit.

Question 11

Which of the following is true about central pattern generators?

A. They oscillate between contraction and inhibition or rest
B. They require several different types of cells to generate an oscillatory pattern
C. They require sensory feedback to oscillate
D. They can be distributed throughout the nervous system

Answer 11

A. They oscillate between contraction and inhibition or rest

Question 12

Which of the following statements accurately describes elements of excitation-contraction coupling in mammalian striate muscle in their proper order? Some steps of the complete process may be omitted.

A. Myosin binds ATP, Ca2+ is released from the SR, tropomyosin is shifted, sarcomere shortens
B. Ca2+ is pumped out of SR, Na+ binds to troponin, binding sites on actin exposed, sarcomere shortens
C. Myosin binds actin, sarcomere shortens, T-tubules depolarize, voltage-gated Ca2+ channels on SR open
D. SR is depolarized, acetyl choline is released, myosin head ratchets, troponin binds Ca2+
E. T-tubule is depolarized, troponin shifts tropomyosin, actin binds ATP, myosin ratchets

Answer 12

A. Myosin binds ATP, Ca2+ is released from the SR, tropomyosin is shifted, sarcomere shortens

Question 13

Which of the following correctly describes gamma motor neurons?

A. They are present in extensor muscles like the quadriceps, but not in flexors
B. They perform a sensory function in the spindle and do not innervate muscle.
C. They are co-activated with alpha motor neurons during voluntary acts.
D. They innervate the extrafusal muscles of the muscle spindle.

Answer 13

C. They are co-activated with alpha motor neurons during voluntary acts.

Question 14

Which of the following is needed for the extension half of the knee jerk reflex (a simple monosynaptic reflex circuit)?

A. intrafusal muscle fibers
B. γ-(gamma) motor neuron
C. spinal interneuron
D. spindle afferent neuron

Answer 14

D. spindle afferent neuron

Question 15

Which of the following pairings correctly describes one of the types of mammalian muscle?

A. Smooth muscle – voluntary contraction by alpha and gamma motor neurons
B. Striate muscle – peristaltic contractions of the gut
C. Smooth muscle – no sarcomeres, myosin is not activated by ATP
D. Cardiac muscle – cells are organized as a syncytium

Answer 15

C. Smooth muscle – no sarcomeres, myosin is not activated by ATP

Question 16

Which statement describes how insect asynchronous muscle differs from mammalian striate muscle?

A. In insects, myosin and actin movement is asynchronous.
B. Ca2+ is pumped out of SR, Na+ binds to troponin, binding sites on actin exposed, sarcomere shortens
C. Insects have consistently high intracellular concentration of Ca2+
D. Insect muscle lacks tropomyosin that blocks the actin binding sites.
E. Insect muscle is not organized into antagonistic pairs.

Answer 16

C. Insects have consistently high intracellular concentration of Ca2+

Question 17

Which statement about bacterial flagella and F1-F0 ATP synthase is true?

A. Movement in both is driven by energy from ATP
B. A cell can have many ATP synthase molecules, but only one flagellum
C. They are both molecular rotors
D. The synthase allows protons to pass through, but flagella allow cations and anions to pass

Answer 17

C. They are both molecular rotors

Question 18

Dynein and myosin are both motor proteins, yet in cells they produce different kinds of motion, bending vs shortening. A factor that contributes to this difference is…

A. Microtubules are linked by nexin which constrains dynein from causing sliding like myosin-actin
B. Myosin can move either way once attached to an actin filament, but dynein only moves in a retrograde (backwards) direction
C. Dynein has two heads, whereas the myosin protein only has a single head
D. Dynein is always attached to a microtubule, but myosin detaches from actin
E. Dynein produces rotation whereas myosin produces shortening

Answer 18

A. Microtubules are linked by nexin which constrains dynein from causing sliding like myosin-actin

Question 19

Which of the following processes definitively involves cellular motion triggered by direct action of motor proteins?

A. Protrusion of cilia outside the boundary of the plasma membrane
B. Rapid closing of Venus’ flytrap leaves
C. Cilia bending in the flow of urine in the collecting duct of the mammalian kidney
D. Spore release by the Pilobolus fungus
E. An infectious bacterium contacting a host cell with an elongating pilus

Answer 19

E. An infectious bacterium contacting a host cell with an elongating pilus

Question 20

In fish that can change gonads from ovaries to testes, the hypothalamus releases ____ that stimulates the anterior pituitary to release ____, which triggers ____.

A. CRH; ACTH; testosterone production
B. GnRH; FSH and LH; ACTH release
C. CRH; FSH and LH; corticosteroid production
D. GnRH; ACTH; testosterone and estrogen production

Answer 20

A. CRH; ACTH; testosterone production

Question 21

Which of the following hormones is NOT directly involved in both the male and female HPG axis in humans?

A. Gonadotropin Releasing Hormone (GnRH)
B. Inhibin
C. Corticotropin releasing hormone (CRH)
D. Luteinizing hormone (LH)
E. Androgens

Answer 21

C. Corticotropin releasing hormone (CRH)

Question 22

Sex determination by haplo-diploidy refers to…

A. In flowering plants haploidy is the normal fertilization and diploidy refers to double fertilization
B. Snakes in which females have two z chromosomes and males have only one z chromosome
C. A system in wasps in which males are haploid and females are diploid
D. Bees in which females develop from unfertilized eggs and males from fertilized eggs

Answer 22

C. A system in wasps in which males are haploid and females are diploid

Question 23

Which of the following mechanisms describes a similarity in sex change in the blue head wrasse AND striped maple trees?

A. The oldest individual in the group changes their sex
B. Both can involve a response to stress
C. Both species primarily change to terminal male phenotypes
D. In both species, the sex of other individuals around them determines their sex change

Answer 23

B. Both can involve a response to stress

Question 24

Which statement about the HPG axis is true?

A. Positive feedback by estrogen coordinates the timing of ovulation
B. The HPG axis first evolved in mammals
C. Progesterone stimulates release of FSH during the follicular phase of the ovarian cycle
D. The hormones in this axis are released by neurons
E. Inhibin also has direct negative feedback on the testis and ovary

Answer 24

A. Positive feedback by estrogen coordinates the timing of ovulation

Question 25

Which of the following is TRUE about ASEXUAL reproduction?

A. Organisms that reproduce asexually cannot also reproduce sexually
B. It does not occur in plants
C. It occurs only in prokaryotes
D. It produces clones
E. It enables genetic diversification

Answer 25

D. It produces clones