ftptest.leeds.ac.uk/2015.02.ftptest.leeds.ac.uk.tar/ftptest.leeds.ac.uk/bionet/mcq_etc/phys_mcq.exe/CORTEX.MCQ

Text File | 1993-08-06 | 11KB | 325 lines

D:Created 14.45 06/08/1993
D:Subject    : Physiology
D:Topic      : Cortex
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:1,2,3,4,5,6,7,8,9,10,11,12
G:2:Medical Students
Q:1,2,3,4,5,6,7,8,9,10,11,12
G:3:Science Students
Q:1,2,3,4,5,6,7,8,9,10,11,12
T:A
L:2
#:1
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 :The postcentral gyrus:
B:N:5
B:1:T:2
 :consists of three parallel strips of cortex that can be distinguished
 :using cytoarchitectonics
B:2:T:2
 :consists of three parallel strips of cortex that can be distinguished
 :using physiological criteria
B:3:T:2
 :each strip contains columns that receive different types of
 :somatosensory information
B:4:F:2
 :the representation of the lower limb is near the lower lateral end of
 :this gyrus
B:5:T:1
 :gives rise to axons in that run in the pyramidal tract
F:5
 :The postcentral gyrus contains the primary somatosensory receiving
 :area, which is divided into strips concerned with inputs from joint and
 :slowly and rapidly-adapting cutaneous receptors.  The pyramidal cells of
 :this gyrus send efferent axons into the pyramidal tract.  The lower limb
 :area of the somatotopic map is on the medial aspect of the hemisphere.
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 :The postcentral gyrus:
B:N:5
B:1:T:2
 :consists of three strips of cortex which can be separated using
 :cytoarchitectonic and physiological criteria
B:2:T:2
 :is the site of the primary cortical receiving area for the sense of
 :touch
B:3:F:1
 :near its lower lateral end, contains a map of the lower limb
B:4:T:2
 :contains vertical columns of cells which respond to only one type of
 :natural stimulus
B:5:F:3
 :when stimulated with small electrical currents can give rise to non-
 :painful sensation referred to one part of the surface of the same side
 :of the body
F:1
 :No explanation available.
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 :In the cerebral cortex:
B:N:5
B:1:F:1
 :the Betz cells are the origin of the cortico-spinal tract
B:2:T:2
 :the cortex is arranged as a series of functionally similar columns of
 :cells which run perpendicular to the surface
B:3:F:2
 :non-specific afferent pathways terminate in the deeper layers of the
 :cortex
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 :specific afferent pathways terminate mainly in layer IV
B:5:T:1
 :layers V and VI contain the cells of origin of corticofugal fibres
F:10
 :Non-specific afferent pathways from the thalamus that are concerned
 :with activation of the cortex end predominantly in the superficial layers
 :of the cortex.  The specific afferent pathways (that project to the
 :primary receiving areas for somatic sensation or vision) terminate in
 :layer IV.  Layers V and VI give rise to efferent fibres from the cortex
 :The functional units of the cortex are cortical columns which deal with
 :modality-specific information (in the somatosensory cortex) or
 :orientation of bars (in the visual cortex).  Betz cells number 30,000 or
 :so and account for only about 3% of the cells of origin of the pyramidal
 :tract.
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 :Consider the localisation of function on the cerebral cortex:
B:N:5
B:1:T:2
 :a lesion of the anterior calcarine gyrus affects foveal vision on one
 :side of the visual field
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 :lesions of the parietal lobe can cause an inability to recognise the
 :form of objects by touch in the absence of any major somatic sensory
 :deficit
B:3:T:1
 :the temporal lobe is concerned with long term memory
B:4:F:1
 :speech is organised usually by the right parietal lobe
B:5:F:2
 :the area of cortex concerned with the direction of gaze is the lower
 :part of the post-central gyrus
F:3
 :The control of eye movements by the cortex is dependent on an area of
 :frontal lobe, in front of the pre-central gyrus.  The disorder described
 :in 2 is astereognosia.
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 :Consider the functions of the frontal lobe:
B:N:5
B:1:T:1
 :stimulation of the frontal cortex can elicit changes in blood pressure
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 :the frontal cortex regulates the activity of the limbic system (and
 :therefore emotional behaviour)
B:3:T:2
 :the frontal cortex is concerned with the development of behavioural
 :strategies
B:4:T:2
 :lesions of the frontal lobe can lead to uninhibited and impulsive
 :behaviour
B:5:F:2
 :removal of the frontal lobe (prefrontal leucotomy) is commonly used
 :as a treatment for psychotic behaviour
F:7
 :The influence of the frontal cortex on mood, emotions, and their
 :expression is dependent on its influence over the limbic system: the
 :latter controls autonomic, motor and endocrine behaviour, and one of the
 :autonomic responses to stimulation of the frontal cortex is a change in
 :blood pressure.  The frontal lobe also plays an important role in thinking
 :ahead - the development of behavioural strategies.
 :Prefrontal lobotomy or leucotomy are obsolete operations.
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 :Functions of the parietal lobe in man includes:
B:N:5
B:1:F:1
 :astereognosis
B:2:T:1
 :recognition of familiar objects
B:3:T:1
 :ability to answer simple questions
B:4:F:1
 :ability to concentrate on a sensory stimulus
B:5:F:1
 :appreciation of pain
F:10
 :Stereognosis, the ability to discriminate objects by their shape using
 :tactile sensation, depends on the parietal lobe.  The area immediately
 :behind the somatosensory cortex is concerned with the interpretation of
 :tactile information: inability to recognise objects by touch in the
 :presence of functional tactile pathways is known as astereognosia.
 :Lesions of the lower parietal lobe can effect the arcuate fasciculus,
 :which connects areas concerned with comprehension of the spoken word
 :with areas of cortex involved in the coordination of muscles of speech;
 :lesions of this bundle of fibres leads to an inability to answer simple
 :questions.
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 :The electrical activity of the cortex (as shown by the EEG):
B:N:5
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 :undergoes a rhythmical fluctuation
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 :is controlled by thalamocortical fibres that terminate in the
 :superficial layers of the cortex
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 :is regulated by the non-specific thalamic nuclei
B:4:F:1
 :during sleep consists of low amplitude, high frequency waves
B:5:F:1
 :becomes desynchronised during hyperventilation
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 :The EEG shows waves of differing frequency, depending on the
 :functional state of the cortex.  This activity is controlled from the
 :non-specific thalamic nuclei (such as the intralaminar nuclei) via
 :thalamocortical fibres that terminate in the superficial layers of the
 :cortex.  During deep sleep the frequency of brain waves diminishes, and
 :they become greater in amplitude, i.e. synchronization occurs, and is
 :attributable to the presence of synchronous activity in cortical cells.
 :A similar phenomenon can occur during hyperventilation due to alkalosis
 :and changes in plasma ionised calcium levels.
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 :Consider the electroencephalogram:
B:N:5
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 :the normal waking rhythm is the alpha rhythm
B:2:F:2
 :the rhythm of the EEG is controlled by the ventrobasal nuclei of the
 :thalamus
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 :the alpha rhythm can be suppressed by opening the eyes
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 :the rhythm of the EEG is slowed by hyperventilation
B:5:F:1
 :the beta rhythm is the dominant rhythm during deep sleep
F:9
 :The alpha rhythm (8-12 Hz) is the dominant waking rhythm when the eyes
 :are shut.  This rhythm becomes desynchronised, i.e. faster and of lower
 :amplitude, when the eyes are open or during mental activity and
 :increases to >12 Hz i.e. into the beta range of frequencies.  The dominant
 :rhythms during deep sleep are slow waves.  The frequency of the EEG is
 :controlled by the ascending reticular formation and by the non specific
 :nuclei of the thalamus, such as the intralaminar nuclei, and not by the
 :specific nuclei they are concerned with discriminative sensation, such
 :as the ventrobasal nuclei.
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 :Cytoarchitectonics:
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 :is the study of the cytoplasmic structures in neurones
B:2:T:2
 :is the anatomical technique which has been used to divide the cortex
 :into areas of differing structure
B:3:F:2
 :was used by Rexed to divide the dorsal horn of the spinal cord into
 :five laminae
B:4:F:1
 :depends on a study of the sizes of nuclei and nucleoli in neurones
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 :depends on the size and packing density of neurones
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 :Cytoarchitectonics divides neural tissues into areas according to the
 :sizes of neuronal somata and the density of packing of neurones.
 :Brodman divided the cortex into areas which were found to correspond to
 :different functions (Areas 3, 1 and 2 - somatosensory areas, area 5-
 :motor cortex, areas 17, 18, 19 - visual areas 1 2 3) Rexed's laminae in the
 :spinal grey matter were based on cytoarchitectonics (Lamina I is one
 :site of origin on the spinothalamic tract and Lamina II (the substantia
 :gelatinosa) consists of interneurons concerned with the modulation of
 :nociceptive transmissions.
 :Rexed divided the dorsal horn into six laminae, not five.
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 :Consider visual evoked potentials in man:
B:N:5
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 :the visual evoked potential has a latency of around 100 msec
B:2:F:1
 :the visual evoked potential has a latency of around 20 msec
B:3:T:2
 :the visual evoked potential is due to activation of visual cortical
 :      neurones by a sudden visual stimulus
B:4:T:1
 :the visual evoked potential originates from the striate cortex
B:5:T:2
 :delay in latency of the visual evoked potential can be due to
 :      demyelination in the visual pathway
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 :The visual evoked potential has a latency of about 100 msec and is due
 :to activation of cortical neurones in the striate (visual, calcarine)
 :cortex.  Delay can be due to demyelination in the visual pathway.
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 :Simple cells in the visual cortex:
B:N:5
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 :receive an afferent input from the lateral geniculate nucleus
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 :have circular receptive fields
B:3:T:1
 :are orientation sensitive
B:4:T:1
 :can be driven by inputs to both eyes
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 :are not excited by diffuse light
F:1
 :No explanation available.
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 :Recordings from the visual cortex show that changes in
 :stimulation of the cortex can be elicited by:
B:N:5
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 :moving an object across the retinal field
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 :changing an object's intensity
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 :changing an object's contrast gradient
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 :changing the orientation of an object's orders
B:5:F:1
 :changing the hue at a constant intensity
F:7
 :Recognition of visual perceptions is mediated by the occipital lobes.
 :The visual cortex is stimulated by changes in light intensity, movement
 :of an object across the retina, changes in orientation of an object's
 :borders, and changes in the gradient of contrast (light to dark).  The
 :visual cortex is especially sensitive to contrast signals as opposed to
 :perception of steady signals.  Specific points in the retina are linked
 :with specific points in the visual cortex.
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