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RECEPTOR.MCQ
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1993-08-06
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D:Created 14.49 06/08/1993
D:Subject : Physiology
D:Topic : Receptors
D:Level : Moderate
D:
D:Authors : Department of Physiology
D: The University
D: Leeds LS2 9NQ
I:MCQ SB 1
G:3
G:1:Dental Students
Q:1,2,3,4,5,6,7,8,9
G:2:Medical Students
Q:1,2,3,4,5,6,7,8,9
G:3:Science Students
Q:1,2,3,4,5,6,7,8,9
T:A
L:2
#:1
G: 10464 1 2 3
S:2
:Some somatic sensory information ascends the spinal cord via the
:anterolateral system:
B:N:5
B:1:F:1
:this is also known as the lemniscal system
B:2:T:2
:neurones of the lemniscal system ascend via the ipsilateral dorsal
:column
B:3:F:1
:are highly specific due to polysensory convergence
B:4:F:2
:the lemniscal cells of the ipsilateral dorsal column are postsynaptic
:to the primary afferents
B:5:T:2
:the dorsal column neurones synapse on neurones in the dorsal column
:nuclei
F:1
:No explanation available.
E:------
#:2
G: 10464 1 2 3
S:3
:Information from the somatosensory system ascends to the
:somatosensory areas of the cerebral cortex where there is a point to
:point representation of the body surface.
B:N:5
B:1:F:1
:this is known as somatotrophic representation
B:2:F:1
:the cerebral cortex is organized in four distinct layers
B:3:T:2
:is a mosaic of narrow vertical columns perpendicular to the brain
:surface
B:4:F:1
:each column responds to several different sensory submodalities
B:5:F:2
:the somatosensory homonculus lies on the precentral gyrus of the
:cerebral cortex
F:6
:Somatotopic representation is the term given to the orderly map of
:somatic sensory inputs on the post-central gyrus of the cerebral cortex
:or at other sites in the brain. The six layers of the cortex are
:organised into functionally distinct columns which run perpendicular to
:the cortical surface, each of which deal with only one modality of
:somatic input.
E:------
#:3
G: 10464 1 2 3
S:2
:Consider the effects of raising skin temperature from 35 to 45
:degrees C:
B:N:5
B:1:T:2
:warm receptors increase their rate of firing and give rise to a
:sensation of warmth
B:2:T:1
:cold receptors will be excited between 40 and 45 degrees C
B:3:T:1
:at 45 degrees C the heat begins to become unpleasant
B:4:T:1
:vasodilatation will occur locally
B:5:F:2
:in spinal man, reflex vasodilatation in the opposite limb would be
:absent
F:10
:The sensation of warmth will be mediated by warm receptors that
:increase their activity between 36 and 43 degrees C. At about 45
:degrees C cutaneous nociceptors are activated and give rise to
:discomfort. Cold receptors are usually silent at 35-40 degrees C but
:can be activated by rapid heating from 40 to 45 degrees C: the
:sensation of PARADOXICAL COLD - a sensation of coldness induced by
:heating cold spots between 40 and 45 degrees C can be explained by this
:anomalous activity of cold receptors. Local vasodilatation may be due
:to the direct effects of temperature on cutaneous vessels, but more
:generalised vasodilatation can occur by a spinal reflex.
E:------
#:4
G: 10464 1 2 3
S:1
:Vibration:
B:N:5
B:1:F:1
:sensation is mediated slowly adapting receptors
B:2:T:1
:sensation is mediated partly by Pacinian corpuscles
B:3:T:1
:sensation is carried by the dorsal column-medial pathway
B:4:F:1
:sensation is carried by slowly conducting primary afferent axons
B:5:T:1
:of a muscle gives rise to a reflex increase in tone in that muscle
F:10
:Vibration sensation is mediated by two groups of rapidly adapting
:cutaneous receptors: (a) Pacinian corpuscles which respond optimally in
:the range 200 - 250 Hz and (b) Meissner's corpuscles which respond
:optimally at around 30 Hz. Their rapidly conducting A-beta axons project
:centrally through the dorsal columns. Vibrations of around 100 Hz can
:also activate the primary (annulospiral) endings of muscle spindles.
:Their Ia afferent fibres make direct contacts with alpha motoneurones
:which innervate the same muscle or its synergists (i.e. the pathway is
:identical to the stretch reflex pathway). The reflex contraction of a
:muscle during vibration is sometimes called the tonic vibration reflex.
E:------
#:5
G: 10464 1 2 3
S:2
:Some somatic sensory information ascends the spinal cord via
:the anterolateral system:
B:N:5
B:1:F:1
:this is also known as the lemniscal system
B:2:T:2
:neurones of the lemniscal system ascend via the ipsilateral dorsal
:column, and
B:3:F:1
:are highly specific due to polysensory convergence
B:4:F:2
:the lemniscal cells of the ipsilateral dorsal column are postsynaptic
:to the primary afferents and
B:5:T:1
:synapse in the medulla on neurones of the medial lemniscus.
F:1
:No explanation available.
E:------
#:6
G: 10464 1 2 3
S:2
:Consider the primary somatosensory receiving area in the
:cerebral cortex.
B:N:5
B:1:F:2
:the point to point map of the body surface on the cortex is an example
:of somatotrophic representation
B:2:F:1
:the cerebral cortex is organized into four distinct layers
B:3:T:2
:the cerebral cortex is a mosaic of narrow vertical columns
:perpendicular to the surface of the brain
B:4:F:1
:each column responds to several different sensory submodalities
B:5:F:2
:the somatosensory homunculus lies on the precentral gyrus of the
:cerebral cortex
F:6
:Somatotopic representation is the term given to the orderly map of
:somatic sensory inputs on the post-central gyrus of the cerebral cortex
:or at other sites in the brain. The six layers of the cortex are
:organised into functionally distinct columns which run perpendicular to
:the cortical surface, each of which deal with only one modality of
:somatic input.
E:------
#:7
G: 10464 1 2 3
S:1
:Consider the localisation of function in the cerebral cortex:
B:N:5
B:1:F:2
:lesions of the middle third of the superior temporal gyrus give rise
:to deafness
B:2:T:2
:lesions of the posterior temporal lobe (Wernicke's area) give rise to
:sensory aphasia (an impaired comprehension of auditory commands)
B:3:T:3
:a band of subcortical association fibres called the arcuate
:fasciculus connects the posterior temporal lobe and the area of cortex
:in front of the mouth and face area of the motor cortex
B:4:T:3
:the area in front of the mouth and face area of the motor cortex
:(Broca's area) is concerned with the coordination of muscles necessary
:for coherent speech
B:5:T:3
:lesions of Broca's area give rise to motor dysphasia (an inability to
:form coherent speech even though comprehension of an auditory command
:is normal)
F:14
:Central deafness is extremely rare because each cochlea is
:represented bilaterally in the brainstem and cortex. Sounds are
:processed in the middle third of the superior temporal gyrus;
:comprehension of the sounds is done posteriorly in the temporal lobe
:(Wernicke's area - described when Wernicke was only 26). Broca's area
:(described in 1861) is concerned with the coordination of muscles involved
:in speech - which are represented in the adjacent precentral gyrus. The
:link between Wernicke's area and Broca's area is via a bundle of
:association fibres called the arcuate fasciculus which arcs from the
:posterior temporal lobe, through the parietal lobe into the frontal lobe.
:Penfields (1959) attempts to investigate disorders of language using
:electrical stimulation of the cortex in conscious subjects found that
:electrical stimulation in Broca's and Wernicke's areas could arrest
:speech.
E:------
#:8
G: 10464 1 2 3
S:1
:The crayfish muscle receptor organ:
B:N:5
B:1:T:1
:is a proprioceptor
B:2:F:1
:is a secondary sensory cell
B:3:F:1
:generates a discharge linearly proportional to stimulus intensity
B:4:T:2
:generates a discharge linearly proportion to generator potential
:amplitude
B:5:T:2
:generator potential amplitude is proportional to log stimulus
:intensity
F:1
:No explanation available.
E:------
#:9
G: 10464 1 2 3
S:1
:Lateral inhibition (centre surround inhibition):
B:N:5
B:1:F:1
:can be observed in primary afferents from skin
B:2:F:1
:occurs in the spinothalamic tract
B:3:T:1
:occurs in the dorsal column nuclei
B:4:T:1
:occurs in the ventrobasal nuclei complex of the thalamus
B:5:T:1
:can be seen in retinal ganglion cells
F:9
:Lateral inhibition is a phenomenon that can be observed in the dorsal
:column nuclei ventrobasal thalamus, somatosensory cortex, retina
:lateral geniculate nuclei and visual cortex. The receptive fields of
:neurones in these sites include a central area, stimulation of which
:excites the neurone and a peripheral (surround) area, which when
:stimulated, inhibits the discharge of the neurone. This process allows
:spatial contrast to be added to the pattern of activity in a population
:of primary afferents with receptive fields at the edge of an object which
:activates them.
E:------
::