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101 Cards in this Set
- Front
- Back
What physical property of light is most closely related to the perception of color?
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Light is electromagnetic radiation, which has three properties: wavelength, frequency, and amplitude. Wavelength is closely related to the perception of color because wavelengths
of 400-700 nm are visible to the naked human eye. Within this visible spectrum, different wavelengths appear as different colors. |
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Name eight structures in the eye that light passes through before it strikes the
photoreceptors. |
The eight structures of the eye through which light passes before striking the
photoreceptors are the cornea, the aqueous humor, the lens, the vitreous humor, the ganglion cell layer, the inner plexiform layer, the inner nuclear layer, and the outer plexiform layer |
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What is myopia, and how is it corrected?
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Myopia, or nearsightedness, occurs when the eyeball is too long. Parallel rays from a
distant light source, which are bent by the cornea and the lens, normally converge at exactly the same plane as the retina. When the eyeball is too long, the rays of light converge and cross before the retina. As a result, the image on the retina is a blurred circle This occurs because the amount of refraction that the cornea and the lens provide is too large to focus distant objects on the retina. To see distant points clearly, nearsighted people must use artificial concave lenses that help focus the image on the retina. |
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Give three reasons explaining why visual acuity is best when images fall on the
fovea. |
Visual acuity is best when images fall on the fovea for three reasons: 1) Visual acuity
improves as the ratio of photoreceptors to ganglion cells decreases. Relatively few photoreceptors feed each ganglion cell in the fovea, resulting in a low ratio, which maximizes visual acuity. 2) The fovea sits in a pit that the lateral displacement of the ganglion and bipolar cells creates above the photoreceptors. This allows light to strike the photoreceptors without passing through the other layers of retinal cells, minimizing light scatter that can blur the image. 3) Visual space is not mapped to the targets of visual input uniformly. The central few degrees of the retina are over-represented in “neural space.” Signals from individual cones in the fovea are represented in a larger volume of brain tissue than input from photoreceptors in peripheral regions of the retina. This specialization contributes to high acuity in central vision. |
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How does the membrane potential change in response to a spot of light in the receptive field center of a photoreceptor? Of an ON bipolar cell? Of an OFF-center ganglion cell? Why?
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Photoreceptors hyperpolarize in response to light. As a result, they release less neurotransmitters at the photoreceptor/bipolar cell synapse. ON-center bipolar cells depolarize in response to light in the receptive field center. This is their response to lessglutamate release at the photoreceptor/bipolar cell synapse. ON-center ganglion cells depolarize in response to light in the receptive field center. These ganglion cells receive direct input from ON-center bipolar cells.
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What happens in the retina when you “get used to the dark”? Why can’t you see color at night?
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Getting used to the dark is called dark adaptation. This capability is a consequence of a duplex retina, in which cones function best at high levels of illumination and rods function best at low levels of illumination. When moving from high to low levels of illumination, the retina must be adapted to the dark before the rods are maximally sensitive. Dark adaptation is a biochemical process in which rhodopsin, the rod photopigment, regenerates after being bleached in the light. The functional circuitry of the retina also readjusts as rhodopsin regenerates. Consequently, information from more rods is available to ganglion cells. The regeneration of unbleached rhodopsin and the resulting changes in functional circuitry take about 20-25 minutes. At night, it is difficult to detect colors because the cones, which have three photopigments with different spectral sensitivities, are inactive. Only cones are capable of color vision. At low levels of illumination, only rods are active and they contain only one photopigment. Rhodopsin’s peak sensitivity is 500 nm.
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In retinitis pigmentosa, early symptoms include the loss of peripheral vision and
night vision. The loss of what type of cells could lead to such symptoms? |
Rods are responsible for night vision. The degeneration of rod photoreceptors can lead
to early symptoms, such as loss of peripheral and night vision. The density of rod photoreceptors increases in the peripheral retina. |
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Rods are much more sensitive to light than cones
because |
B. Rods have much higher concentration of
photopigment. |
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The molecule in the rod that is directly affected by
photons is called |
Rhodopsin.
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All humans have a blind spot in their eye because of the
presence of the |
Optic disk
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What is the flow of information in the retina?
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Photoreceptor, bipolar cell, ganglion cell.
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What is the difference between ON-center ganglion cells and OFF-center
ganglion cells? |
ON-center ganglion cells receive input from ON
bipolar cells while OFF-center ganglion cells receive input from OFF bipolar cells. |
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The ability of the eye to distinguish two points that
appear close together is called |
Visual acuity.
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How is the aqueous humor different from the vitreous humor?
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Aqueous humor lies behind the cornea while the
vitreous humor lies between the lens and the retina. |
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What is the total number of different photopigment types
that are contained in the rods and cones of the retina? |
4
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How is phototransduction in cones different from that in
rods? |
Cones have different opsins.
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Pupils change size in response to different lighting
conditions. This is called: |
Pupillary light reflex.
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On a moonless night, one can see a dim star best with
one's |
Peripheral retina
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Most of the light refraction in our eye is done by the
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Cornea
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The only cell that has a axon that leaves the retina is the
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Ganglion cell
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Which cells actually capture the light energy within the
eye? |
Photoreceptors.
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A single photon can be detected by the eye because one
molecule of rhodopsin can activate many molecules of phosphodiesterase, a process called |
Amplification.
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How do we focus on objects located at a distance less than 9 m from the eye
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A change in the shape of the lens
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What is absorption?
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The transfer of light energy to a particle or
surface |
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The structure of the eye responsible for converting light
energy into neural activity is |
Retina.
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Which of the following corresponds to the photoreceptor “dark current
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At rest, the membrane potential of a rod outer
segment is about –30 mV. |
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Which of the following is a role proposed for movement sensitive
neurons in the parietal area called MST? |
Navigation
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Mr. Stewart underwent a surgery to remove a tumor in his brain. During
the surgery, lesions developed in the optic radiations. What is the potential impact of these lesions |
Blindness
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The fact that only spiny stellate cells are found in layer IVC suggests that
layer IVC is involved in what type of projections? |
Projecting to neighbouring layers of the cortex
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What is the purpose of the decussation at the optic chiasm?
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To have each visual hemifield processed by the
contralateral side of the brain |
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Beyond the optic chiasm (i.e. after axonal decussation), a lesion in any
tract (i.e., optic tract or optic radiation) will cause which of the following symptoms? |
Loss of the contralateral visual hemifield
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Which of the following is the function of direction-selective striate cortex neurons
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Analysis of object motion
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Layers V and VI are involved in long-range projections from cortex.
Which type of neuron would most likely be involved in such connections |
Pyramidal cells.
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Which of the following is a region of sensory surface that, when
stimulated, changes the membrane potential of a neuron? |
Receptive Field
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Which of the following is the common characteristic in the receptive
fields in the ganglion cells of the retina, the LGN, and striate cortex neurons in layer IVC? |
Center surround antagonism
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The MAJOR target of the optic tract in the human is the
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Lateral geniculate nucleus of the thalamus
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At the optic chiasm, some fibers from the retina cross from one side of
the brain to the other, a process called |
Decussation
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The projection from the LGN to cortex is called the
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Optic radiation
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What is the most likely deficit resulting
from a V4 lesion? |
Color perception
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Susan fell down the staircase and injured her head, causing a transection
of the left optic nerve. What is the consequence of this lesion? |
Blindness in the left eye
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Where are the first binocular neurons encountered in the retinofugal
projections? |
LGN
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Visual cortex is divided into ________ layers
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6
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Which ganglion cell axons cross to the opposite side of the brain at the
optic chiasm? |
Axons from the nasal retina
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Which of the following is the major source of synaptic input to the LGN?
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Striate cortex
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What is the correct order of the structures through which visual
information passes from the retina to cortex |
optic nerve, optic chiasm, optic tract
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What is the biggest clue that information from different retinal ganglion
cell types are kept separate in the LGN? |
The fact that M-cells project only to layers 1 and
2 of the LGN |
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The majority of ganglion cells are _______, which have _______ receptive
fields |
P cells, small
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"Ganglion cells that are neighbours in the retina have axon terminals that
are neighbours in central visual structures." This organisation is an example of |
Retinotopic mapping
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. After 10
million years of living under these conditions, you would expect the population of this lost people to contain a high percentage of ______ in their retinas, compared with people living on the surface of the earth. |
Rod photoreceptors.
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Which of the following is NOT a target of the optic tract
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Visual cortex
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Changes in hair cell receptor potential results from the
opening of potassium channnels on the tips of the stereocilia when the cilia bend. These receptors are a type of |
mechanoreceptor.
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The base of the basilar membrane can be described as
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Stiff, narrow, and especially sensitive to high
frequencies. |
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Which of the following triggers movement of the ossicles in the auditory
pathway? |
Tympanic membrane
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Which of the following contributes to the pressure at the oval window
being 20 times greater than that at the tympanic membrane? |
Ossicles act like levers
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The main difference between the response of hair cells in
the auditory system and other neurons when K+ channels open is |
the opening of K+ channels depolarize the hair cells
but hyperpolarize most neurons. |
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The initial stages of the basic auditory pathway is
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Sound wave moves the tympanic membrane
Tympanic membrane moves the ossicles Motion at the oval window moves the fluid in the cochlea Movement of the fluid in the cochlea causes a response in sensory neurons |
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Why is movement at the oval window accompanied by a complementary motion at the round window
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Incompressible fluid in cochlea
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How do the pinnae of humans differ from the pinnae of
other animls such as cats and horses? |
humans cant move pinna
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Which of the following contains auditory receptor neurons?
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Organ of Corti
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The number of compressions or rarefactions of a sound
wave that passes by our ears each second is known as___ of sound and is expressed in units called |
Frequency, hertz
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All ascending auditory pathways converge on the
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Inferior colliculus.
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Identify the two structures that are separated by the tympanic
membrane. |
The auditory canal and the middle ear
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Compared with other extracellular fluids, endolymph has
an unusually |
High K+ concentration
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The fluid in the inner ear has greater inertia than in the
outer ear, and more pressure is needed to vibrate the fluid that the air can provide. This amplification in pressure is known as ______________ which is the function of the ___ ear |
sound force amplification, middle
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Output of the nuclei in the brain stem that process neural
responses to sound generated by the inner ear is relayed to the __________ in the thalamus. |
medial geniculate nucleus.
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Deafness in only one ear can occur from unilateral damage to the
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Cochlea nuclei
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Phase locking can be used to code for _____ frequencies, tonotopy can
be used to code for _________ frequencies and both phase locking and tonotopy are useful for coding ___________ frequencies. |
Low, High, Intermediate
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Following the principle of delay lines, a sound coming from one side will
cause optimal summation in the superior olive via afferents from |
the longest axon from the ipsilateral cochlear nucleus,
and shortest axon from the contralateral cochlear nucleus |
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Unilateral cortical lesion of striate cortex leads to complete blindness in
one visual hemifield, whilst auditory function is still retained to a certain extent after unilateral lesions because |
Each eye sends output of the hemifield to only the
contralateral hemisphere while each ear sends output to both hemispheres |
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A neuron in the auditory system is the most responsive to sound at one
frequency. This is known as |
Characteristic frequency.
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The columnar organization present in A1 is on the basis of:
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Frequency
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A neuron in the auditory system is the most responsive to sound at one
frequency. This is known as |
Characteristic frequency.
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What is one explanation for why there are so many central auditory relay
nuclei? |
It takes a lot of neural tissues to ascertain
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The duplex theory refers to the use of:
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Differences in time, phase and intensity for
horizontal localization |
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Nearby neurons have similar characteristic frequencies and the
systematic organisation of characteristic frequency within an auditory structure is called |
Tonotopy.
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Which structure is the first in the auditory pathway to have binaural
neurons? |
Superior olive.
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Medial geniculate neurons have axons that terminate predominately in
which layer of the primary auditory cortex? |
Layer IV.
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Where do the cell bodies (somas) of the primary afferent
axons of the somatic sensory system lie? |
Dorsal root ganglion.
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What type of information does the dorsal column-medial lemniscal
pathway carry? |
Touch and proprioception
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Lesion in which part of the brain would cause a neglect
syndrome, where a part of the body or a part of the world is ignored or suppressed? |
Parietal.
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What kind of receptive field property would give the
highest resolution in a sensory system? |
Small receptive field
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Touch and proprioceptive information ascends to the
cerebral cortex through which thalamic nuclei? |
Ventral posterior nuclei
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Primary sensory afferent axons have widely varying diameters and their
size correlates with the type of receptor to which they are attached. Which of these axons are the smallest and the slowest |
Temperature, pain, and itch
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At what point do the axons of the dorsal column-medial lemniscal
pathway cross to the opposite side of the CNS? |
The axons from the cells of the dorsal column
nuclei decussate in the medulla. |
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Which of the following is NOT TRUE acout the
topographic map of the body's surface sensations on the structure in the brain? |
This topographic map has to be continuous.
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What are mechanoreceptors?
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Sensitive to physical distortion
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A dermatome is the
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Area of skin innervated by the dorsal roots of a
single spinal segment. |
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Which quality of the somatic sensory cortical organization does the
distortion of the sensory homunculus reflect? |
The relative size of the cortex that is devoted to each
body part is correlated with the density of the sensory input received from that part. |
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A disease that usually affects only one dermatome is
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Shingles
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Pressure in the heart and blood vessels and stretching of
the digestive organs are perceived by |
Mechnoreceptors.
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To which stimuli do the majority of nociceptors respond
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Mechanical, Thermal, Chemical
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Nociceptors are found in most body tissues except
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Brain
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Small injections of morphine or endorphins into the dorsal horn can
produce |
Analgesia
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Jack felt some initial pain after being stabbed in the arm, but soon felt
no pain at all. Which neural region was probably engaged in increased activity during this time |
The periaqueductal gray matter.
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As it relates to the gate theory of pain, mechanoreceptor activation
results in |
Indirect inhibition of neurons projecting to the
spinothalamic tract |
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Which of the following phenomena would lead to referred pain?
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Nociceptors from the appendix and the navel synapse
on the same cell in the substantia gelatinosa |
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In large amounts, capsaicin causes analgesia by:
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desensitizing pain fibers and depleting substance p
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A patient presents with a deficit in the sensation of pain and temperature
on the left side of his body, but no other sensory deficits. Which region of the white matter in the spinal cord has most likely been damaged |
Ventral spinal cord on the right side
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The dorsal column-medial lemniscal pathway and the spinothalamic
pathway are significantly different. In what ways are the two pathways similar? |
Both pathways synapse in the VP nucleus of the
thalamus |
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At what point do the axons of the spinothalamic pathway cross to the
opposite side of the CNS? |
Axons of the spinothalamic pathway cross
immediately in the spinal cord and ascend contralaterally. |
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Aspirin is often administered to alleviate pain. From what you know
about nociceptors, how might aspirin work? |
By inhibiting the synthesis of prostaglandins
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