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ANAT 321 > Sensory systems > Flashcards

Sensory systems Flashcards

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1
Q

What are the four main functions of sensory information?

A

Perception
Control of movement
Regulation of the function of internal organs
Maintenance of arousal

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2
Q

What is the modality property of a sensation?

A

Type of sense recruited by the stimulus (e.g., somatosensory, olfactory, gustatory, auditory, etc.)

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3
Q

What are the two main pathways conveying somatosensory information? For what submodalities are they responsible for?

A

Dorsal column-medial lemniscal pathway: fine touch, proprioception
Anterolateral pathway: pain and temperature

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4
Q

What are the specific afferent fibers involved in the the different somatosensory submodalities?

A

Aalpha and Abeta fibers: fine touch and proprioception
Adelat and C fibers: pain and temperature

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5
Q

What is particular about the morphology of primary sensory afferents?

A

They are pseudounipolar neurons (their cell bodies lay in the ganglia)

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6
Q

How is the intensity of a somatosensory stimulus coded?

A

Frequency of action potentials.

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7
Q

What particular type of receptor on primary somatosensory afferents converts the external stimulus into electrical signalling?

A

Low-threshold mechanoreceptor.

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8
Q

Why do we say that the different sensory receptors act as filters?

A

Because they are filtering out information by responding to a specific stimulus feature (creating channels, or labeled lines).

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9
Q

What skin sensory receptors respond to change in pressure? Respond to constant pressure?

A

Constant pressure: Merkel and Ruffini
Change in pressure: Meissner and Pacinian

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10
Q

What is a labeled line?

A

Afferent fiber mediating only one type of submodality.

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11
Q

True or false: pain and temperature primary afferent fibers have special sensory receptors, different from the ones mediating proprioception and fine touch.

A

False: they have free endings, no specialized sensory receptor at all.

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12
Q

True or false: one single sensory afferent can contain different labeled-lines.

A

True.

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13
Q

Why is combinatorial processing essential to comprehensive perception?

A

Necessary for the integration of parallel labeled lines in the CNS to generate full perception.

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14
Q

Place in order the following types of primary sensory afferent from the fastest to the slowest:

Adelta
Abeta
Aalpha
C

A

Aalpha >Abeta > Adelta > C

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15
Q

How are the Aalpha and Abeta afferents differentiating in their roles?

A

Aalpha afferents mediate proprioception information from muscle spindles and golgi tendon organs.

Abeta afferents mediate fine touch information from low threshold mechanoreceptors.

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16
Q

Receptive fields are inversely proportional to _____.

A

Innervation density.

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17
Q

Posterior-anterior is equivalent to ____-____.

A

Caudal-rostral.

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18
Q

True or false: sensitivity equals acuity.

A

False: sensitivity is determined by activation threshold, not innervation density.

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19
Q

How many segments is the spinal cord comprising of? What are their subcategories? How many segments are contained in each specific subcategory?

A

31 segments
8 cervical
12 thoracic
5 lumbar
5 sacral
1 coccygeal

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20
Q

If there are 31 segments to the spinal cord, how many spinal nerves are there?

A

62, since each segment corresponds to the entry point of a pair of spinal nerves.

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21
Q

At what segment does the spinal cord itself actually end? What is found below? Contained in what space?

A

The spinal cord ends around the first lumbar. Below, the cauda equina is extending through the lumbar cistern.

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22
Q

True or false: each dorsal root ganglion contains the sensory and motor information specific to its spinal nerve.

A

False: sensory information is contained in the dorsal root, motor information is contained in the ventral root, and both of the roots fuse to form one spinal nerve.

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23
Q

What is the ganglion equivalent in the CNS?

A

Nucleus.

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24
Q

What is a dermatome?

A

A region of the body innervated by a single pair of spinal nerves.

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25
What is the intermediate zone of the spinal cord containing?
Interneurons and autonomic neurons.
26
Fine touch and proprioception information climbs up in what part of the spinal cord? What about pain and temperature?
Fine touch and proprioception: dorsal column Pain and temperature: anterolateral column
27
True or false: all sensory information is located in dorsal regions of the spinal cord.
False: pain and temperature projections are situated anterolaterally.
28
Why would some sensory information synapse directly in the spinal cord instead of climbing up in the dorsal column?
To carry out motor reflexes.
29
In the spinal cord, fine touch and proprioception is ____, while pain and temperature is ____. Place: contralateral, ipsilateral.
In the spinal cord, fine touch and proprioception is ipsilateral, while pain and temperature is contralateral.
30
What are central pattern generators?
Intrinsic circuits of the spinal cord carrying stereotyped and rhythmic movements such as locomotion and scratching.
31
What is the equivalent of nerve in the CNS?
Fiber tract.
32
What are the main regions comprising the brainstem?
Medulla, pons and midbrain.
33
How is arm-leg information represented in the dorsal column? In the anterolateral column?
Dorsal column: arm lateral and leg medial Anterolateral column: arm medial and leg lateral
34
Refer to a sagittal section of the brainstem and place the fourth ventricle, the cerebral aqueduct, the superior and inferior colliculi and the pineal gland.
35
What are the dorsal columns becoming in the brainstem? What about the anterolateral columns?
Dorsal columns split in fasciculus gracilis (x2, carrying sensory inf. from lower body and legs) and fasciculus cuneatus (x2, carrying sensory inf. from upper body and arms). Anterolateral columns becomes the spinothalamic tracts.
36
True or false: the spinothalamic tract synapses in the brainstem.
False: only in the thalamus (refer to the name).
37
What are the dorsal column nuclei? Where are they located?
Located in the brainstem. Nucleus gracilis and nucleus cuneatus.
38
Where is the medial lemniscus beginning along the brainstem?
At the junction between the pons and the medulla.
39
At what point is the information from the dorsal column nuclei becoming contralateral?
When information forming the medial lemniscus.
40
Where is the synapse between first-order and second-order neurons of proprioception and fine-touch sensory information?
In the dorsal column nuclei.
41
Describe the somatotopic organization of the medial lemniscus.
Arm inf. located dorsally and leg inf. located ventrally.
42
What happens to the orientation of the medial lemniscus between the medulla and the midbrain?
Medial lemniscus "flips" on itself, meaning that in the midbrain the somatotopic organization of the medial lemniscus is inverted compared to the organization in the medulla.
43
At what level of the brainstem is the cerebral aqueduc formed?
At the level of the midbrain.
44
What are the 12 cranial nerves?
1. Olfactory 2. Optic 3. Oculomotor 4. Trochlear 5. Trigeminal 6. Abducens 7. Facial 8. Vestibulocochlear 9. Glossopharyngeal 10. Vagus 11. Spinal Accessory 12. Hypoglossal
45
Associate each cranial nerve to one of the following categories: sensory, motor and mixed.
Sensory: 1. Olfactory 2. Optic 8. Vestibulocochlear Motor: 3. Oculomotor 4. Trochlear 6. Abducens 11. Spinal Accessory 12. Hypoglossal Mixed: 5. Trigeminal 7. Facial 9. Glossopharyngeal 10. Vagus
46
Compare the organization of the grey matter in the spinal cord to the organization of the cranial nerve nuclei in the brainstem.
In both regions, somatic sensory information is found dorsally (except for pain and temperature), autonomic sensory and motor information are found centrally and somatic motor information is found ventrally. In the brainstem, dorsal information is lateralized and ventral information pushed medially, comparatively to the organization in the spinal cord.
47
How is called the central core of grey matter in the brainstem?
Reticular formation.
48
Name the main functions of the reticular formation.
Mediating stereotyped motor responses Carrying autonomic (visceral) functions Ascending arousal
49
Name the innervation targets of the oculomotor nerve.
Superior rectus Medial rectus Inferior rectus Inferior oblique Pupillary sphincter (control over pupil constriction) Ciliary muscle (changing lens shape) Levator palbebrae superiori (muscle raising eyelid)
50
List the observable consequences occuring from damage to occulomotor nerve.
Ipsilateral eye drifts laterally (lateral strabismus). Affected eye cannot move medially beyond the mid-position. Ipsilateral eyelid drops shut + vertical eye movements are impaired + pupil dilates and does not constrict in response to light + eye cannot focus on near objects
51
Name the innervation target of the trochlear nerve.
Superior oblique.
52
List the observable consequences occuring from damage to trochlear nerve.
Affected eye drifts upward.
53
Name the innervation target of the abducens nerve.
Lateral rectus.
54
List the observable consequences occuring from damage to abducens nerve.
Ipsilateral eye deviates medially. Both the ipsilateral and contralateral eyes cannot move past the mid-position when the patient attempts to move them toward the affected side.
55
List the observable consequences occuring from damage to facial nerve.
Paralysis of the ipsilateral side of the face. No autonomic contraction of the stapedius muscle (results in hearing booming sounds louder). Corneal blink reflex impaired in one eye.
56
The periaquaductal gray exemplifies what functions of the brainstem?
Integration of stereotyped motor responses + carrying autonomic functions.
57
What nerve is prominently carrying visceral sensory inf. from the body to the brainstem? Where does it synapse in the brainstem?
Vagus nerve, synapsing in the nucleus of the solitary tract.
58
What two general pathways are taking the arousal projections from the brainstem?
Dorsal pathway passing through the thalamus. Ventral pathway that projects directly into the cortex.
59
What neurotransmitter is known to mediate arousal and attention?
Norepinephrine.
60
True or false: NE neurons fire during REM sleep.
False.
61
Where is dopamine mostly originating from?
Substantia nigra and VTA (ventral tegmental area).
62
Where is acetylcholine originating from in the brain? And where does it project?
From basal forebrain. Projecting to cerebral cortex, hippocampus and amygdala.
63
True or false: receptive fields of sensory and motor neurons are conserved all the way up to the cortex.
False: only somatotopic organization is.
64
Histamine is more likely to wake you up or to put you to sleep?
Wake you up.
65
What is the main role of lateral inhibition?
Sharpening contrast of sensory signals.
66
True or false: the thalamus is a binary structure.
True.
67
What are the main groups of nuclei in the thalamus?
Relay, association and intralaminar.
68
What associations below are incorrect? LGN - vision MGN - hearing Ventral anterior and ventral lateral - somatic sensation from the body VPL - somatic sensation from the face VPM - basal ganglia and cerebellum
Incorrect: Ventral anterior and ventral lateral - somatic sensation from the body VPL - somatic sensation from the face VPM - basal ganglia and cerebellum Corrected: VPL - somatic sensation from the body VPM - somatic sensation from the face Ventral anterior and ventral lateral - basal ganglia and cerebellum
69
Generally speaking, feedforward projections from the relay nuclei of the thalamus input in what layer of the cortex? Feedback projections output from what layer of the cortex to reach back relay nuclei of the thalamus?
Inputting in layer 4. Outputting in layer 6.
70
True or false: input and output regions of the association nuclei are sensibly the same.
True.
71
True or false: association nuclei take the most space in the thalamus.
True.
72
Provide two hypotheses for which cortical information would project to the thalamus only to reach back to the cortex.
1. Send an efference copy to broadcast a motor command to other cortical regions. 2. Coordinate activity in different cortical regions.
73
What are the respective targets of the medial dorsal and pulvinar association nuclei?
Medial Dorsal: prefrontal cortex. Pulvinar: parietal, occipital and temporal lobes + superior colliculus.
74
Why do we say that the thalamus is the gate-keeper of the brain?
The thalamus controls incoming information to the cortex.
75
Generally speaking, feedforward projections from association nuclei of the thalamus input in what layer of the cortex? Feedback projections output from what layer of the cortex to reach back thalamic association nuclei?
Inputting in top layers. Outputting in layer 5.
76
What are the two firing modes of thalamic neurons? What are they corresponding to?
Transmission mode: wakefulness. Bursting mode: slow wave sleep.
77
What determines whether a thalamic neuron is in transmission mode or bursting mode?
Resting membrane potential of the thalamic neuron.
78
List the main sources of thalamic modulator inputs.
Brainstem, inhibitory GABAergic inputs from thalamic reticular nucleus and feedback projections from the cerebral cortex.
79
Information arriving or leaving the cerebral cortex passes through which structure?
Internal capsule.
80
Regarding the morphology of the cerebral cortex, folds are called ____ and fissures are called ____.
Gyri. Sulci.
81
The central and lateral sulci delimit what lobes?
Frontal, parietal and temporal lobes.
82
The cingulate sulcus delimits what lobe?
Limbic.
83
List the sulci of the frontal lobe delimiting the precentral gyrus, the inferior frontal gyrus, the middle frontal gyrus and the superior frontal gyrus.
Central sulcus, precentral sulcus, inferior frontal sulcus and superior frontal sulcus.
84
List the sulci of the frontal lobe delimiting the postcentral gyrus, the superior parietal gyrus, the supramarginal gyrus and the angular gyrus.
Central sulcus, postcentral sulcus, intraparietal sulcus, lateral sulcus and superior temporal sulcus.
85
On what surface of the cortex are found the parahippocampal and fusiform gyri?
On the ventral surface.
86
What structure is found buried under the parahippocampal region? Under the uncus?
Hippocampus. Amygdala.
87
In what does result the sectioning of the corpus collosum?
Split-brain patient. Two hemispheres do not communication anymore.
88
True or false: the corpus collosum is made exclusively of white matter.
True.
89
True or false: the cortex is made exclusively of grey matter.
True.
90
Generally speaking, how many layers does have the cortex?
Six.
91
Associate the right layer(s) to the right function: Layers: II, III, IV, V, VI Functions: - Output for feedforward projections to other regions of the cerebral cortex. - Input for feedforward projections from thalamic relay nuclei. - Projects to a broad range of subcortical targets. - Output for feedback projections to the thalamus.
II and III - Output for feedforward projections to other regions of the cerebral cortex. IV - Input for feedforward projections from thalamic relay nuclei. V - Projects to a broad range of subcortical targets. VI - Output for feedback projections to the thalamus.
92
In what layer of the cortex are found the largest pyramidal cells?
Layer V.
93
Give three staining techniques for the cortex layers. What are they respectively staining?
Golgi stain: cell body, axon and dendrites. Nissl stain: cell body. Weigert stain: myelinated axon in the CNS.
94
Provide an example of a functional column in the CNS.
Ocular dominance columns in the primary visual cortex.
95
What are the evolutionary pressures likely to have shaped the human brain as it is actually?
Computational efficiency and wiring cost.
96
True or false: each neuron has a single axon.
True (but there can be branching).
97
Provide a brief overview of how cortex layers communicate in a functional column.
Information from thalamocortical projections -> layer 4 -> layers 2/3 -> layers 5/6 (+ feedforward cortical projections) -> subcortical feedback projections.
98
True or false: the postcentral gyrus is located in the frontal lobe.
False: parietal lobe.
99
From what regions is the somatosensory association cortex comprised of?
Area 5 and SII.
100
Describe the flow of information between layers of cortex areas with different levels of processing.
Feedforward projections: layers 2/3 (output) -> layer 4 (input). Feedback projections: layers 5/6 (output) -> pretty much any layer except 4.
101
True or false: receptive fields get smaller as information flows to higher-level processing areas.
False: the opposite.
102
Regarding cortex distribution, what are the three global levels of information processing?
Primary sensory cortex, unimodal association cortex and multimodal association cortex.
103
Name two multimodal association areas.
Frontal association cortex. Posterior multimodal association cortex.
104
True or false: Broca's region is situated on the temporal lobe and Wernicke's region is located on the frontal lobe.
False: Broca's region is situated on the frontal lobe and Wernicke's region is located on the temporal lobe.

ANAT 321 (2 decks)

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