Anatomy of the Cerebrum Flashcards
(85 cards)
1
Q
What is the cerebrum?
A
- Largest part of the forebrain
- Divided into two halves, the (cerebral hemipheres)
> which are separated by a deep median longitudinal fissure which lodges the falx cerebri - In the depth of the fissure, the hemispheres are connected by a bundle of fibers called the corpus callosum
2
Q
Name the parts of the brain?
A
- Cerebral hemisphere
- Diencephalon
- Brain stem – midbrain, pons and medulla oblongata
- cerebellum
3
Q
Name the older brain structures?
A
- The Brainstem
> Medulla
> Pons
> Reticular Formation - Thalamus
- Cerebellum
- The Limbic System
> Amygdala
> Hypothalamus
> Hippocampus
4
Q
What is the cerebral cortex?
A
Superficial layer of grey matter
5
Q
What is white matter?
A
Deeper to the cortex, contain axons to and from the cells of the cortex
6
Q
What are basal ganglia?
A
Number of nuclear masses buried within the white matter
7
Q
What is the lateral ventricle?
A
The cavity of hemisphere that stores CSF
8
Q
Name the parts of the cerebral hemispheres?
A
- Cortical
- Medullary
- nuclear
9
Q
Describe the function of the left hemisphere?
A
> Processes logical tasks (reading, writing, speaking, mathematics, and comprehension skills)
Controls the right side of our body
In the 1960s, it was termed as the dominant brain
10
Q
Describe the function of the right hemisphere?
A
> Processes non-verbal tasks/perceptual (spatial relationships, musical/artistic ability and mental imagery)
Controls the left side of our body
May also be related to some negative emotions
11
Q
What is the corpus callosum?
A
a wide band of axon fibers that connect the two hemispheres and allow them to communicate
12
Q
Describe the 3 surfaces of the cerebral hemispheres?
A
- a convex one [the superolateral/antero/posterior]
- a base = the slightly concave inferior surface
- a flat medial surface
13
Q
The cleft between the medial surfaces of the 2 hemispheres is called the?
A
longitudinal cerebral fissure
14
Q
What is found at the bottom of longitudinal fissure?
A
the hemispheres are connected by a large bundle of transverse fibres = the corpus callosum
> splenium = posteriorly
> body and genu = anteriorly
> rostrum = ventrally
15
Q
Name the 4 prominent sulci of the cerebral surface?
A
- Central sulcus (Sulcus of Rolando)
- Lateral sulcus (Fissure of sylvius)
- Parieto-occipal sulcus
- Cingulate sulcus
- Preoccipital notch
16
Q
Name the 4 gyri that make up the lateral surface of the frontal lobe?
A
- Precentral – between central and precentral sulci
- Superior frontal
- middle frontal
- inferior frontal
17
Q
What is the inferior frontal gyrus divided into?
A
- Orbital
- Opecular part
- Triangular part
18
Q
What is the motor cortex?
A
the area at the rear of the frontal lobes that control voluntary movements
19
Q
What is the sensory cortex?
A
the area at the front of the parietal lobes that receives information from skin surface and sense organs
20
Q
Describe the functional areas of the frontal lobe?
A
- Primary motor cortex (precentral gyrus)
– involved in initiation of voluntary movement. - Premotor or supplementary motor area (precentral gyrus)
– involved in initiation of voluntary movement - Broca’s area (Opecular and triangular parts of inferior frontal gyrus)
– production of written and spoken language - Prefrontal cortex (remainder of frontal lobe)
– involved in personality, insight and foresight
21
Q
What can the frontal lobe be functionally divided into and what does damage to these areas result in?
A
- motor - control of movement
> weakness/paralysis - premotor - integration of motor skills/learned action
> uncoordinated movements/impaired motor skills/speech - prefrontal - complex cognitive functions
> difficulties with planning/decision making/inhibition/memory/attention/ preservation/personality changes/aphasia
22
Q
What is the function of the frontal lobe?
A
The frontal lobe is the area of the brain responsible for higher cognitive functions:
1. Problem solving
2. Spontaneity
3. Memory
4. Language
5. Motivation
6. Judgment
7. Impulse control
8. Social and sexual behavior
23
Q
Consequences of lesions of premotor motor cortex?
A
clinical syndrome of apraxia
> Patients have normal reflexes and no muscle weakness
> patients have difficulty performing complex motor tasks such as tying shoelaces
24
Q
Consequences of lesions in the most anterior parts of the frontal lobe?
A
They may affect the ability of someone to plan their future life
> The most anterior parts of the frontal lobe are concerned with the planning of movement and future actions
25
Describe the location of the temporal lobe?
1. The convex anterior (the temporal pole)
> fits into the large lateral part of the middle cranial fossa.
2. The posterior part of the temporal lobe
> sits on top of the tentorium cerebelli
26
Lateral surfaces of the temporal lobes are composed of?
1. Superior gyri
2. Middle gyri
3. inferior gyri
27
Describe the cortical regions of the temporal lobe and their functions?
1. Primary Auditory Cortex – superior surface + superior temporal gyrus
> Responsible for hearing
2. Primary Olfactory Cortex –
> Interprets the sense of smell once it reaches the cortex via the olfactory bulbs (Not visible on the superficial cortex)
3. Wernicke’s Area – posterior portion of superior temporal gyrus
> For Language comprehension
> Located on the Left Temporal Lobe
28
What are the hallmark symptoms of Wernickes aphasia?
1. Language comprehension is inhibited
2. Words and sentences are not clearly understood
3. sentence formation may be inhibited or non-sensical.
29
Describe the functions of the central auditory system?
1. High-level auditory abilities
> “recognition, interpretation, integration”
e.g., speech recognition, speaker recognition, recognition of a familiar melody, etc.
2. plays a role in some more basic auditory abilities
e.g. sound localization and at least part of frequency analysis.
30
What is the arcuate fasiculus?
A white matter tract that connects Broca’s Area and Wernicke’s Area through the Temporal, Parietal and Frontal Lobes
> Allows for coordinated, comprehensible speech
31
Damage to the arcuate fasciculus may result in?
Conduction Aphasia
> Where auditory comprehension and speech articulation are preserved, but people find it difficult to repeat heard speech
32
Where do you usually find the lesions that cause conduction aphasia?
superior temporal or inferior parietal
1. conduction aphasia plus limb apraxia
> parietal lesions
2. conduction aphasia without apraxia
> temporal lesions
33
Lesions on arcuate fibers result in?
1. conduction aphasia
2. ideomotor apraxia
34
What is the Brocas area?
a motor speech area at the back end of the inferior frontal gyrus
- usually In one hemisphere: the left in right handed persons
> is the centre for motor control of speech [it sends impulses to the motor cortex]
35
Describe the roles of the temporal lobe?
plays a role in emotions, and is also responsible for smelling, tasting, perception, memory, understanding music, aggressiveness, and sexual behavior.
The temporal lobe also contains the language area of the brain.
35
Describe the consequences of damage to the Brocas area?
expressive aphasia
- the patient knows what they want to say but they cannot get the words out
i.e. They cannot speak the words
> When it is injured , there is no paralysis of muscles , yet the patient says only words with great difficulty [ataxic or motor aphasia].
36
Describe the functions of the temporal lobes?
1. memory
2. auditory processing
3. object recognition
4. identifying
5. naming
37
Lesions of the temporal lobes can cause?
1. amnesia
2. Wernickes aphasia (more if left side is affected)
3. agnosias
4. prosopagnosia (if right side damaged - faces not recognized)
5, category specific deficits
38
Where is the occipital lobe?
- at the back end of the cerebral hemisphere the occipital lobe is continuous with the temporal lobe and sits on top of the tentorium cerebelli, the shelf of dura that separates it from the posterior cranial fossa.
- The tentorium lies in the transverse cerebral fissure, below the cerebral hemispheres and above the cerebellum
39
What are the functions of the occipital lobes?
1. sensory integration
2. visuoperception
3. vision
> contains visual areas
40
Lesions of the occipital lobes can cause?
1. heminopia
2. blindsight
3. visual agnosia
4. colour agnosia
41
What is apperceptive visual agnosia?
- cannot recognize by shape
- cannot copy drawings
- often involves prosopagnosia
42
What is associative visual agnosia?
- can copy but unaware what it is: cannot assign meaning to object
- difficulty in transferring visual info into words
43
What is visual object agnosia?
inability to recognize object by sight
- basses on lesion
1. lateral occipital cortex (cortical) = appreciative visual agnosia
2. associative fibre connections (transcortical) = associative visual agnosia (disconnection syndrome
44
What is alexia?
acquired inability to read
1. alexia without agraphia/pure alexia/pire word blindness/visual verbal agnosia - disconnection syndrome
2. alexia with agraphia - lesion at angular gyrus
3. third alexia/alexic agraphia - seen with brocas aphasia
45
Describe pure alexia?
• Was described by Dejerine
• Left occipital lesion, usually an infarction
• Involve the commisural fibres in splenium
• Fibres from right occipital lobe are disconnected from language centres in the left parietal lobe
• Patients are unable to read because of disruption the visual stimulus from the right occipital lobe cannot be transferred to the region of the opposite angular gyrus
46
What are verbal disconnection disorders?
• Verbal output is exclusively sub served by the left hemisphere
• So in callosal lesion patient have difficulty in communicating from right hemisphere
47
What is left visual anomia?
• Image seen in right visual field (left hemisphere) are normally named or described, while those shown in the left hemi field (right hemisphere) cannot.
• Lesion site: Posterior and dorsal portion of splenium
48
What is left hemialexia?
• Special case of anomia for words shown in the left visual field, patient unable to report aloud or write down those presented on the left side
• Lesion site: Ventral and anterior portion of splenium
49
What is left auditory anomia?
• Repetition of verbal material (syllables, words and numbers) or naming of auditory stimuli (sound and voices) are normal when presented to each ear separately- due to the bilateral projection of cortical auditory pathway
. Bilateral simultaneous stimulation of both ear, results in deficit from left ear i.e right hemisphere
• Lesion site: Posterior inferior trunk/isthmus
50
What is left tactile anomia?
Patient can describe and name objects palpated with the right hand (without vision)but not with the left hand
• Also k/a pseudoastereognosis
• Lesion site: posterior trunk
51
What is right olfactory anomia?
• Odors presented to right nostril (right hemisphere) are not named, while those presented to left nostril (left hemisphere) are-olfactory inputs project ipsilaterally.
• No anosmia: patient winces in response to unpleasant odours
52
What are motor disconnection disorders?
• Difficulty in coordinating bimanual gesture due to lack of sensory motor transfer,
• eg- difficulty in tie shoelaces in absence visual inspection
• Rapid alternating movement of both hand also impaired, eg-hand clapping/tapping
• Lesion: anterior corpus callos um
53
Where is the parietal lobe located?
- Lies between the frontal occipital and temporal lobes.
- It is seperated from the frontal lobe by the central sulcus .
- it is largely seperated from the temporal lobe by the lateral sulcus, but at the back end of this sulcus the parietal,occipital and temporal lobes are confluent on the lateral surface of the hemisphere.
54
The lateral surface of the parietal lobe is divided into?
1. Postcentral gyrus – between central and post central sulci
2. Superior parietal lobule
3. Inferior parietal lobule
> Intraparietal sulcus separates superior and inferior lobules
55
Name the inferior and medial components of the parietal lobe?
a. inferiorly composed of:
1. Supramarginal gyrus
2. Angular gyrus
b. Medially contains:
Precuneus
- bounded by subparietal and calcarine sulci
56
Describe the functions of the parietal lobes?
1. sensory integration
2. visual attention
3. perceptual awareness
4. attention
57
Lesions of the parietal lobe can cause?
1. neglect
2. inattention
3. dyscalia
4. anomia
5. agraphia (writing problems)
6. alexia (learning problems)
7. apraxia (orient sound)
58
What is parietal neglect syndrome?
failure to recognize side of body contralateral to injury
> deny own limbs
> objects in contralateral visual field ignored
59
Describe the functions of the parietal lobe?
1. Senses and integrates sensation(s)
> touch, smell, and taste
2. Spatial awareness and perception
> Proprioception - Awareness of body/body parts in space and in relation to each other
> hand eye coordination and arm movement
60
Name and describe the functions of the cortical regions of the parietal lobe?
1. Primary Somatosensory Cortex (Post central Gyrus) – Site involved with processing of tactile and proprioceptive information.
2. Somatosensory Association Cortex - Assists with the integration and interpretation of sensations relative to body position and orientation in space. May assist with visuo-motor coordination
3. Primary Gustatory Cortex – Primary site involved with the interpretation of the sensation of Taste
60
Name and describe the specialized area found in the parietal lobe?
Wernicke’s area
> is responsible for matching written words with the sound of spoken speech
61
Name the components of the medial surface of the cerebrum?
Sulci: Parietooccipital, Calcarine, Cingulate
Gyri: Cingulate, Parahippocampal
62
What is the limbic lobe?
The limbic lobe is located deep in the brain, and makes up the limbic system
63
What are the cerebral lobes?
B
1.
Frontal - from frontal pole to
central sulcus
2. Temporal- lateral sulcus to
parietal occipital sulcus
3.
Parietal- from central sulcus to
parietooccipital sulcus +
preoccipital notch
4
Occipital -bounded by parietal
and temporal lobes
5
Limbic lobe - interposed
between corpus callosum
frontal, parietal and occipital
lobes
64
What is Broadmans map?
• Brodmann produced a numbered, cytological map of cerebral cortex based upon its regional histological characteristics
• Subdivisions with similar cellular and laminar structure are called
'areas'
• Brodmann's numbering of these cortical locations has become one of the standard ways to identify brain areas.
65
What is the language area of the brain?
> Organized around the lateral
fissure.
> Broca's area: concerned with expressive aspects of language.
> Wernick's area: responsible for comprehension of the spoken words.
> Nearby regions of temporal lobe and parietal lobe (angular gyrus & supramarginal gyrus of the inferior parietal lobule) are important in naming, reading, writing, and calculation.
66
Describe hemispheric dominance?
> The localization of speech centers & mathematical ability is the criterion for defining the dominant cerebral hemisphere.
> In 96% of normal right-handed individuals and 70% of normal left-handed individuals, the left hemisphere contains the language centers. These are left hemisphere dominant.
• Cerebral dominance becomes established during the first few years after birth.
67
Describe the white matter of the brain?
> Underlies the cortex, contains nerve fibers, neuroglia cells and blood vessels.
The nerve fibers originate, terminate or sometimes both, within the cortex.
> Depending on their origin & termination, these nerve fibers are classified into three types: Association, Projection & Commissural
68
What are association fibers?
Unite different parts of the same hemisphere, are of two types
1. long - connect more distant parts
2. short - connect adjacent gyri
69
What are commissural fibers?
Connect the corresponding regions of the two hemispheres
70
What are projection fibers?
Consist of afferent and efferent fibers of the cerebral cortex
71
Name long association fibers?
1. Uncinate fasciculus: connects frontal to temporal lobe
2. Superior longitudinal fasciculus: connects the frontal, occipital, parietal, and temporal lobes
3. Arcuate fasciculus: connect gyri in frontal to temporal lobes
4. Inferior longitudinal fasciculus:
connects occipital to temporal pole
5. Cingulum: connects frontal & parietal lobes to the para-hippocampal gvrus and adjacent temporal gyri
72
Name commissural fibers?
1. Corpus callosum
- Connects the corresponding regions of the two hemispheres except the temporal lobes, that are connected by anterior commissure
2. Anterior commissure
- connects the inferior and middle
temporal gyri & the olfactorv regions of the two hemispheres
3. Posterior commissure
- connects the left and right midbrain
Important in the bilateral pupillary reflex
4. Hippocampal commissure (commissure of fornix)
- connects the two hippocampi with each other
73
What is the corpus callosum?
Corpus Callosum
> Connects the corresponding regions of the two hemispheres except the temporal lobes, that are connected by anterior commissure
• It is shorter craniocaudally than is the hemisphere
The callosal fibers linking the frontal poles curve forward forming anterior forceps (forceps minor)
The callosal fibers linking the occipital poles curve backward forming posterior forceps (forceps major)
74
Structure of the corpus callosum?
The posterior portion of the corpus callosum is called the splenium; the anterior is called the genu; between the two
• is the truncus, or "body", of the corpus callosum.
• The part between the body and the splenium is often markedly thinned and thus referred to as the "isthmus"
• The rostrum is the part of the corpus callosum that projects posteriorly and inferiorly from the anterior most genu, as can be seen on the sagittal image of the brain.
• The rostrum is so named for its resemblance to a bird's beak.
75
Function of corpus callosum?
1. Genu connect the prefrontal cortex between the two halves of the brain.
2. Midbody and splenium interconnect areas of the premotor and supplementary motor regions and motor cortex
3. Posterior body of the corpus. communicates somatosensory information between the two halves of the parietal lobe and visual center at the occipital lobe.
76
What is agenesis of corpus callosum?
Agenesis of the corpus callosum (ACC) is a rare birth defect (congenital disorder) in which there is a complete or partial absence of the corpus callosum.
• The development of the fibers that would otherwise form the corpus callosum become longitudinally oriented within each hemisphere and form structures called Probst bundles.
77
Name congenital callosal disorders?
1. hypogenesis (partial formation)
2. dysgenesis (malformation) of the corpus callosum
3. hypoplasia (underdevelopment) of the corpus callosum
78
What is the diagnosis of agenesis of corpus callosum?
• Diagnosis
- Callosal disorders can be diagnosed only through a brain scan
- They may be diagnosed through an MRI, CT scan, prenatal ultrasound, or prenatal MRI
79
Signs and symptoms of agenesis of corpus callosum?
1. Poor motor coordination
2. Delays in motor milestones such as sitting and walking
3. Delayed toilet training
4. Chewing and swallowing difficulties
5. Vision impairments
6. Hypotonia
7. Low perception of pain
Research: shown to have some cognitive disabilities (difficulty in complex problem solving) and social difficulties (missing subtle social cues), even when their intelligence quotient is normal.
Other characteristics sometimes associated with callosal disorders include seizures, spasticity, early feeding difficulties and/or gastric reflux, hearing impairments, abnormal head and facial features, and mental retardation.
80
Splitting the brain?
A procedure in which the two hemispheres of the brain are isolated by cutting the connecting fibers (mainly those of the corpus callosum) between them. Usually done to prevent uncontrollable seizures in patients with severe epilepsy.
With the corpus callosum severed, objects (apple) presented in the right visual field can be named Obiects (pencil) in the left visual field cannot.
81
What are projection fibers?
- Consist of Afferents & Efferents of the cerebral cortex
- Deeper to the cortex, these fibers are arranged radially as the corona radiata.
- Then the fibers converge downward, form internal capsule, between thalamus and basal ganglia.
- Continue in the crus cerebri of the midbrain, basilar part of pons, & pyramid of medulla oblongata.
82
What is the internal capsule?
Bundle of projection fibers, passes through the interval between the thalamus and the basal ganglia
83
What are the 5 parts of the internal capsule?
1. Anterior limb: Thalamocortical &
Frontopontine fibers
2. Genu: corticobulbar fibers
3. Posterior limb: Corticospinal, Corticobulbar & Thalamocortical fibers
4. Retrolenticular part:
Geniculocalcarine fibers
5. Sublenticular part (not shown):
geniculo-temporal fibers
