Neurobiology Ch 11 Dashboard Q's

You measure changes in membrane potential in an ON-center bipolar cell that is exposed to light in the center of its receptive field. What response would you expect to see? a. An action potential b. Depolarization due to increased release of glutamate by the photoreceptor cell c. Hyperpolarization due to decreased release of glutamate by the photoreceptor cell d. Hyperpolarization due to increased release of glutamate by the photoreceptor cell e. Depolarization due to decreased release of glutamate by the photoreceptor cell

E

Which sequence represents the most direct pathway for the transmission of visual information from the eye to the brain? a. Photoreceptor → bipolar cell → ganglion cell → brain b. Horizontal cell → bipolar cell → ganglion cell → brain c. Photoreceptor → bipolar cell → amacrine cell → brain d. Photoreceptor → horizontal cell → ganglion cell →brain e. Photoreceptor → bipolar cell → amacrine cell → ganglion cell → brain

A

Which statement about color vision is false? a. Because there are several different color types of cones, they are more sensitive to low (dim) illumination levels than the population of rods is. b. Cones (in humans) come in three different "colors": blue, green, and red (or short-, medium-, and long-wavelength). c. Different wavelengths of light produce different patterns of activity in the cone population as a whole. d. Information from specific color cones can be selectively relayed to specific regions of a retinal ganglion cell's receptive field. e. The different photopigments in each cone are highly sensitive to a small range of wavelengths but can actually be activated by photons of a wide range of wavelengths.

A

The iris a. is responsible for the refraction of light onto the retina. b. regulates the amount of light entering the eye. c. applies tension to the lens. d. contains the pigment epithelial cells that nourish photoreceptors. e. covers the cornea, shielding it from harmful UV rays.

B

Which mechanism is not a component of the phototransduction signaling cascade initiated by light falling on a rod? a. Absorption of a photon of light by 11-cis retinal b. Activation of protein kinase A c. A conformational change in the rhodopsin protein d. Dissociation of the α subunit of transducin from the β/γ complex e. Increased activity of PDE (phosphodiesterase)

B

The fovea a. covers approximately 40 percent of the retina. b. lies at the center of the optic disk. c. lies at the center of the macula lutea. d. is synonymous with "fundus." e. is the only part of the retina that contains xanthophyll.

C

The main reason that rods are more sensitive to light than cones is that a. the photopigment of rods is much more sensitive to light than the photopigment used in cones. b. the eye contains 1000 times as many rods as cones. c. the rod transduction mechanism provides greater signal amplification. d. rods are sensitive to a much broader range of wavelengths. e. rods have many different types of opsin proteins.

C

The mechanism that accounts for light-induced hyperpolarization of photoreceptors is a. the gating of ion channels by released retinal monomers. b. a sudden increase in the concentration of cAMP, leading to activation of potassium channels. c. a rapid fall in the concentration of cGMP, leading to closure of Na+ / Ca2+ channels. d. a rapid rise in the concentration of cGMP, leading to closure of Na+ / Ca2+ channels. e. light-induced photoisomerization of membrane-bound calcium channels.

C

Which statement regarding photoreceptor cells is true? a. Like typical sensory neurons, they fire action potentials when the cell depolarizes to threshold in response to stimuli. b. Unlike typical neurons, their resting membrane potential is more negative, usually around -100mV. c. Unlike typical neurons, cation channels are open at rest, allowing the influx of sodium and calcium. d. Unlike typical neurons, neurotransmitter release is dependent on an influx of potassium ions. e. Unlike typical neurons, they hyperpolarize in response to a stimulus due to opening of chloride channels.

C

The two main functions of the retinal pigment epithelium are _______ and _______. a. structural support to maintain curvature of the retina; phagocytosis of shed outer segments b. structural support to maintain curvature of the retina; synthesis of rhodopsin c. phagocytosis of shed outer segments; synthesis of rhodopsin d. phagocytosis of shed outer segments; regeneration of the photoreceptor photopigments e. synthesis of rhodopsin; regeneration of the photoreceptor photopigments

D

Which statement about center-surround receptive fields in the retina is false? a. Cells that are inhibited by light in their center are excited by light in their surround. b. Cells that are excited by light in their center are inhibited by light in their surround. c. The surround portion of the receptive field is typically an annulus (or doughnut-shaped ring) that surrounds the circular center. d. Light in the center of an off-center cell will increase its firing rate. e. The best stimulus for an on-center cell is light in its center and darkness in its surround.

D

Why is myopia in humans thought to be more common now than it was in ancient times? a. The vigorous exercise associated with early human lifestyles better nourished the retina. b. Early humans were not exposed to the environmental toxins present in modern life. c. Chronic exposure to fire smoke had a protective effect on the vision of early humans. d. Early humans did not engage in the kinds of activities (e.g., reading and writing from an early age, watching television) characteristic of modern life. e. Myopia was not less common; it was less recognized.

D