practice exam
Fast adaptation in the auditory system is characterized by
Calcium-induced channel closure - Fast adaptation: (1-2 ms) Ca+2 enters cell and induces channel closure
Assume that damage along the visual pathway would cause reduced (e.g. from binocular to monocular) or total loss of vision, depending in the location and severity of the damage. Both reduced and total loss/blindness would be considered to "affect" vision of the quadrant.
Damage to the optic CHIASM would affect peripheral vision in all 4 visual quadrants - Damage to the LEFT temporal retina would result in monocular vision in of the RIGHT superior and inferior visual fields ( i.e. 2 quadrants) - Damage to the RIGHT optic tract would result in total blindness of the LEFT superior and inferior visual fields (i.e. 2 quadrants) - Damage to the OPTIC CHIASM could lead to monocular vision in all 4 visual quadrants and reduced peripheral vision of all 4 visual quadrants
In which of the following conditions would you be able to detect a sweet taste?
Eat miraculin with lemon - Miraculin at a neutral pH is INCORRECT because it is inactive at a neutral pH - Miraculin with lemon is CORRECT because it is activates at an acidic pH, which activates the sweet taste receptor - Miraculin with sweeteners is INCORRECT because it blocks the normal action of sweeteners binding to sweet taste receptors
Which gradient primarily mediates the entry of potassium into hair cell stereocillia?
Electrical gradient The K+ concentration is high in both the endolymph, where the K+ enters from, and the hair cell. However, the endolymph has a Vm of +80 mV, while the hair cell has a Vm of -45 mV. Therefore, the electrical gradient plays a more major role in determining driving force and the flow of K+.
________________ contains a high [K+] and ____________ contains a low [K+]
Endolymph, Perilymph Endolymph has high [K+] Perilymph has low [K+] Both inner and outer hair cell cytoplasm have high [K+]
sensory cells must have a linear response to stimuli in order to effectively sense stimuli
FALSE nociceptive thermoceptors have low activity until the temperature is in the painful range
The optic nerve is made up of axons from what type of retinal cells?
Ganglion cells - only the ganglion cells send axon out of the retina
In the frog, axons from the posterior (temporal) retina target the _____ tectum because they express _____.
Ipsilateral anterior, high EphA and high EphB - ephrin B in the optic chiasm is repulsive and prevents temporal axons from crossing, and ephrin A in the posterior tectum is repulsive and prevents temporal axons from growing in the posterior.
A scientist observes an MRI from a patient suffering from sensory loss. She notices damage in the RIGHT ventral posterior medial nucleus (VPMN). Where is the patient likely to be experiencing sensory loss?
LEFT face touch - TOUCH and PAIN information for the BODY synapse in the contralateral VPLN - TOUCH and PAIN information for the FACE synapse in the contralateral VPMN
If the RIGHT optic TRACT of the brain is severed, the person would have
NO visual information about the LEFT visual field - C is the right optic tract - it carried all of the information from both the right and left eyes about the LEFT visual field.
An unconscious patient with damage to the Medial Longitudinal Fasciculus will respond to an influx of WARM water in the RIGHT ear in what way?
Only the left eye rotates to the LEFT - Damage to the MLF will prevent contraction of the medial rectus muscles, which are needed to move: ---right eye to the left ---left eye to the right - Warm water in the right ear mimics turning head to the right and excites the right horizontal canal ----slow movement the VOR moves eyes to the LEFT ----- with MLF damage, only the left eye moves to the left because this movement requites the lateral rectus muscle
Touch mechanoreceptors respond to membrane stretch, but differ in the amount of stretch required to reach threshold. The _________ corpuscles require the most stretch for activation and the _______ corpuscles require the least.
Ruffini, Pacinian Ruffini ~ 300 µm (skin stretch) Merkel ~ 30 µm (light touch: edges, points, curves) Meissner ~ 6 µm (heavy pressure: skin motion) Pacinian ~ 0.8 µm (vibration)
Which of the following correctly matches the non-visual pathway target to its function?
Superior colliculus - orienting movements of the head and eyes - Hypothalamus - reflex control of the pupil and lens INCORRECT the hypothalamus does regulation of circadian rhythms - Superior colliculus - orienting movements of the head and eyes CORRECT this is the role of the superior colliculus - Pretectum - regulation of circadian rhythms INCORRECT the pretectum does reflex control of the pupil and lens
What might be the outcome if your medial lemniscus on the LEFT side was damaged?
You could not feel touch information from the right side of your body - The first order neurons in the touch pathway enter the dorsal horn of the spinal cord and ascend in the ipsilateral dorsal column white matter (gracile or cuneate fasciculus). The 2nd order in the touch pathway neurons have their cell bodies in the gracile or cuneate nuclei and extend axons to the contralateral side of the medulla and ascend in the medial lemniscus. Thus, damaging the LEFT medial lemniscus would affect touch sensation for the RIGHT side of the body.
Glutamate binding leads to horizontal cell____, and light leads to horizontal cell ____.
activation/inhibition Horizontal cells are activated by glutamate binding. The glutamate is released by photoreceptors, Photoreceptors release less glutamate in the light, so light leads to inhibition/reduced activity of horizontal cells.
If you shine light onto a rod photoreceptor, which of the following would you expect to INCREASE?
activity of phosphodiesterase In the photoreceptors, the following are constitutively on/open: - guanylyl cyclase makes cGMP - K+ channels open in cell body Light activates the opsin, then.. - transducin trimeric G protein activated - phosphodiesterase activated - cGMP levels decrease cyclic-nucleotide gated - Na+ channels close - Na+ current decreases
In the cochlea, which region is most responsive to low frequency sounds?
apex
The TRPM8 and TRPV1 receptors are considered to be polymodal because they
are involved in both temperature and taste perception - Polymodal refers to the fact that these receptors are involved in more than one sensory modality.
Which of the following retinal cells has GABA-A receptors?
cones - Rods and cones have GABA-A receptors - Horizontal cells release GABA
Each cone will synapse on a single pair of bipolar cells, while many different rods will synapse onto the same pair of bipolar cells. This leads to
cones having higher acuity than rods - Cones provide color vision because they express S, M and L opsins, but this has nothing to do with the number of cones that synapse onto a pair of bipolar cells - Cones provide greater acuity, meaning higher resolution - Rods provide greater sensitivity, which is why they are most important for low light vision - Both rods and cones have center surround antagonism
Which of the following does not activate the otolith organs?
constant velocity - Neither the otolith nor the semi-circular canals is good at sensing constant velocity
The 2nd synapse in pain conduction for the body occurs in the _________
contralateral VPLN
The fibers of the Meyer's loop on one side of the brain carry information about the
contralateral superior visual field
Which of the following would cause INCREASED glutamate to be released from a rod cell?
decreasing phosphodiesterase activity cGMP is constitutively made in photoreceptor cells. The cGMP binds to sodium/calcium channels to open them, so decreased levels of cGMP would hyperpolarize the cell. When light hits a photoreceptor, PDE activity is increased, which breaks down cGMP, which hyperpolarizes. Decreasing PDE activity would allow the cGMP-gated Na+ channels to remain open and the depolarized rod/cone would release glutamate
Certain neurodegenerative diseases are associated with loss of the sense of smell (olfaction). It is believed that this occurs because in these diseases
fewer granule cells are made - although neurodegenerative diseases may eventually affect many different senses, loss/reduced olfaction can be an early warning sign of Parkinson's disease and other diseases that affect adult neurogenesis. - only the granule cells undergo adult neurogenesis, so fewer are made as the disease progresses - granule cells synapse on Mitral and tufted cells, but NOT on ORNs
The 1st synapse in pain conduction occurs in the ___________
ipsilateral dorsal horn of the spinal cord For pain, the DRG neuron enters the dorsal horn on the same side of the body as the pain sensation (ipsilateral) and has it's first synapse in the dorsal horn.
The LOWEST level of firing in an OFF center ganglion cell will be detected when the center of the receptive field is ____ and the surrounding area is ____
light, dark The highest firing for an OFF center cell would be when the center id dark and the surround is light. The lowest firing of the off center cell is when the center is light and the surround is dark.
Mechanosensory information from the lower body decussates (crosses the midline) in the
medulla - Mechanosensory information from the body ascends in the spinal cord via the Cuneate (upper body) or Gracile (lower body) fascicles crosses, then crosses the midline in the caudal medulla and ascends via the medial lemniscus to the thalamus
An image that falls in the BINOCULAR portion of the RIGHT visual field is detected in the
nasal right and temporal left retina
For two odorants to be perceived differently it is necessary that they - have completely different molecular structures - bind to completely different - olfactory receptor neurons - stimulate different trimeric G proteins - A and B - none of the above
none of the above (a) FALSE Odorants with very similar molecular structures can be perceived differently (e.g. D and L enantiomers of carvone). (b) FALSE most odorants probably bind to several different ORNs. Two odorants that are perceived differently may bind overlapping but distinct sets of ORNs (c) FALSE regardless of which receptor they bind, all odorant stimulate the Golf Trimeric G protein
A DIFFERENCE between touch and pain sensations from the body is that - neurons carrying pain sensation synapse in the VPLN - touch sensory neurons have their cell bodies in the DRGs - only pain sensation has dermatomes - neurons carrying pain sensation do not synapse in the thalamus - none of the above
none of the above (a) NOT a DIFFERENCE neurons carrying pain and touch sensation BOTH synapse in the VPLN(b) NOT a DIFFERENCE BOTH touch and pain sensory neurons have their cell bodies in the DRGs(c) FALSE both pain and touch sensation have dermatomes(d) FALSE neurons carrying pain and touch sensation both synapse in the thalamus
A stroke patient suffers severe ischemia in the LEFT lateral geniculate nucleus (LGN) of the thalamus. You should expect the patient to have REDUCED - Pain sensation from the left side of the body - Pain sensation from the right side of the body - Touch sensation from the left side of the face - Pain sensation from the right side of the face - None of the above
none of the above - The LGN relays visual information - The VPLN and VPMN are the thalamic nuclei responsible for relaying somatosensory information to the cortex.
Neurons that convey the sense of __________ do NOT synapse in the thalamus on the way to the cortex pain from the face - touch - taste - vision - none of the above
none of the above Olfaction is the only sense that doesn't synapse in the thalamus on the way to the cortex
Which of the following sensory receptor cells have axons?
olfactory receptor neurons - The axons of the ORNs make up cranial nerve I. None of the other cell types have axons.
The most sensitive two point discrimination would be achieved by
small receptive field and high receptor density - Receptor density: Higher = increased discrimination - Size of receptive field: Smaller= increased discrimination
In class we discussed an experiment in which the optic nerve of a frog's eye was cut and then reattached after the eye was rotated 180 degrees. The diagram below shows the normal and rotated orientation of the eye. In the normal eye A dorsal and C is ventral, while B is anterior and D is posterior. Alter rotation both the anterior-posterior and dorsal-ventral axes are flipped.
- Axons from the B region of the retina grew to the posterior tectum - Axons from the retina grow to the original targets The frog is able to see the fly normally after the operation, but it cannot catch the fly. This is because the axons from the retina grew to their original target, essentially flipping the frog's map of the visual world. The original target for anterior retina (B) are in posterior tectum and for posterior retina (D) are in anterior tectum.
Which of the following statements about hair cells is CORRECT? - Stereocilia protrude into perilymph, which is high in potassium - The cytoplasm of the hair cell is lower in potassium compared to perilymph - Influx of potassium into stereocilia depolarize their hair cell When depolarized, hair cells fire action potentials - More than one of the above
- Influx of potassium into stereocilia depolarize their hair cell Stereocilia protrude into endolymph cytoplasm is higher in K+ than perilymph CORRECT: Influx of potassium into stereocilia depolarize their hair cell hair cells show graded release of NT
If right dorsal horn of a spinal cord segment is damaged, which of the following is the likely result?
- Loss of touch sensation on the right side of the body at and below the damage - Loss of pain sensation on the right side of the body only at the level of the damage -When the right dorsal horn is damaged, this would affect both pain and touch information for the right side entering in that segment and affect all touch information from the right side that was ascending in the Cuneate and Gracile columns from below the level of injury. Pain information below the injury would not be affected because pain information ascend in the contralateral anterolateral white mater tract.
Which of the following is a function of the tip-links?
- Open mechanically gated channels - Open K+ channels - Connect adjacent stereocilia (ribbon synapse?)
Which of the following statements about somatosensation is CORRECT?
- Touch and pain sensation both map to the somatosensory cortex - Body parts with smaller receptive fields generally map to larger portions of the somatosensory cortex (C) FALSE Neurons with free nerve endings are PAIN/temp sensors and have their 1st synapse in the dorsal horn
When would an OFF-center ganglion cell be the MOST active?
- When the center is darker than the surround - When the center is lighter than the surround INCORRECT this is the opposite and would lead to the lowest amount of activity - When the center and surround are both in light INCORRECT this would lead to a lower amount of activity than when the center is darker than the surround - When the center is darker than the surround CORRECT OFF-center ganglion cells are the most active for the longest period of time when this situation occurs - When the center and surround are both in darkness INCORRECT this would lead to a lower amount of activity than when the center is darker than the surround
On a dare, a foolhardy graduate student swallows the contents of a small vial from the laboratory refrigerator. Luckily, the student doesn't die, but they do report an odd loss of taste sensation. Specifically, they can still taste salty and sour, but cannot taste sweet, bitter or umami. What compound might have been in the vial?
- a phospholipase C inhibitor a) INCORRECT a PDE inhibitor would prevent the breakdown of cGMP and cAMP, but these molecules are not involved in taste sensation b) INCORRECT - sweet, bitter and umami all lead to activation of PLC, which converts PIP2 into IP3 and DAG. The IP3 opens IP3 receptors on the ER, leading in increased cytoplasmic CA+2 and opening calcium-gated TRPM5. Activating the IP3 receptor would enhance sensation of sweet, bitter and umami c) CORRECT PLC is needed to make IP3 for sensation of sweet, bitter and umami d) INCORRECT all 5 taste sensation require ATP receptors, so an ATP receptor antagonist would bock all 5 taste sensations.
Anosmia is a condition in which someone is unable to perceive odorants (i.e. has a poor or no sense of smell). Although anosmia can be a side effect of other diseases, some completely healthy people can have a genetic condition that causes anosmia. Mutation in which gene(s) might cause anosmia? Remember, mutations can increase or decrease protein function
- cyclic nucleotide gated Na+/Ca+2 channel - a chloride transporter - phosphodiesterase The signaling cascade for olfaction is: 1. odorant binds GPCR 2. Golf activated 3. adenylyl cyclase III activated 4. cAMP produced 5. cAMP binds to and opens cAMP-gated Na+/Ca+2 channel 6. Ca+2 binds and opens Ca+2 gated Cl- channel 7. Cl- move out of cell, further depolarizing the ORN a) mutations in the cyclic nucleotide gated Na+/Ca+2 channel could affect step 5 (b) mutation in a chloride transporter could affect step 7 (c) phosphodiesterase breaks down cAMP, so mutations in PDE could affect step 5
What might be the symptoms of a person who has a mutation that LOWERS the threshold of the NaV1.7 channel?
- hypersensitivity to painful stimuli - increased action potential firing by nociceptive neurons NaV1.7 is the voltage-gated Na+ channel that initiates the pain signal in nociceptors. Lowering the threshold would make the neuron fire an AP at a lower level of pain signal and cause increased/ hypersensitivity to painful stimuli. It might also make normally non-painful stimuli become painful
In the otolith organs, if a hair cell is EXCITED by a backward tilt of the head, then a hair cell in a similar position, but on the opposite side of the striola will be________ by a ________ tilt of the head.
- inhibited, backward - excited, forward Hair sells on the opposite sides of the striola have their stereocillia in opposite directions and are therefore activated by opposite head movements. - If A and B are on opposite sides of the striola, then: when A is active B will be inhibited - If A is activated by backward tilt, then B will be inhibited by backward tilt and excited by forward tilt.
Mutations in the TRPM5 receptor would affect which sensation of which taste(s)?
- sweet - umami Sweet, bitter and umami stimulate the GPCRs that activate PLC and lead to opening of the TRPM5
Fibers carrying information from the inferior visual field will project to
- the area dorsal to the calcarine sulcus - the area of visual cortex contralateral to the visual field (b) TRUE The inferior visual field maps to areas of V1 dorsal/superior/above the calcarine sulcus (c) TRUE the left visual field maps to the right/contralateral visual cortex
Damage to which quadrant would lead to loss of PAIN sensation on the RIGHT side of the body at the site of injury (not below), and the loss of TOUCH sensation at and below the site of injury?
A Pain and touch information for the right side of the body enter in quadrant A. Pain information synapses in the dorsal horn in A and the 2nd order neuron crosses to the contralateral side and ascends in the anterolateral white matter tracts in quadrant D. Therefore damage to A would affect pain at that level of the spinal cord, but NOT below. Touch information enterers the dorsal horn in quadrant A and ascends in the dorsal column white matter (Gracile or Cuneate fasciculus) to the medulla. The first synapse is on the second order neuron in the gracile or cuneate nucleus. Therefore, damage in quadrant A would affect touch sensation at that level and below.
Which neurotransmitter plays an essential role in taste cell signaling to taste sensory nerves?
ATP - ATP signaling is required for taste sensation, while serotonin may regulate, but not required for taste sensation.
