Cerebral Hemispheres Flashcards
What are the general features of the cerebral hemisphere?
Sulcus (dip), gyrus (elevation), fissure (deeper dip), grey matter on surface, white matter inside , basal ganglion in white matter, lateral ventricle is the cavity in each hemisphere
What is the main fissure separating each hemisphere?
Median longitudinal fissure
What is the corpus callosum?
Large white matter tract that connects the 2 hemispheres of the brain
What separates the pre and post-central gyrus?
Central sulcus
Also separates the frontal and parietal lobe
What separates the frontal and temporal lobes?
Lateral sulcus
What separates the parietal and occipital lobes?
Parieto-occipital sulcus
What is separated by the cingulate sulcus?
Parietal and frontal lobes
Is on medial surface of the hemisphere
What is the frontal lobe split into?
Split into superior, middle and inferior gyrus
What is the temporal lobe split into?
Superior, middle and inferior temporal gyri
What is the parietal lobe split into?
Superior and inferior parietal lobule
Describe the insula of the brain
Found in transverse temporal gyri - Heschl’s convolutions
Which part of the brain is motor and which part is sensory?
Posterior part after central sulcus is sensory and anterior part is motor
There are primary sensory areas ad associated areas
What is the function of medial portions of the cerebral hemisphere?
Storage and retrieval of processed information
Limbic system
Is the frontal lobe motor or sensory?
Motor
Describe the primary motor cortex in the frontal lobe
Area 4 - pre-central gyrus
Somatotopic representation of contralateral half of body - motor homunculus
What area is the inferior frontal gyrus?
Broca’s area of motor speech
Area 44 and 45
What is the function of the prefrontal cortex in the frontal lobe?
Cognitive functions of higher order intellect, judgement, prediction and planning
What type of neurons is the parietal lobe?
Somatosensory
What is the primary sensory area of the parietal lobe?
Post central gyrus - Area 3,1,2
Receives general sensations from contralateral half of body
Somatotopic representation - sensory homunculus
What is the superior parietal lobule?
Interpretation of general sensory information (sensory associated area) and conscious awareness of contralateral half of body
What is the inferior parietal lobule?
Interface between somatosensory cortex, visual and auditory association areas
In dominant hemisphere contributes to language functions
What happens if there is parietal lobe lesion?
Hemisphere neglect
Right left agnosia
Acalculia - signs of dementia
Agraphia - inability to spell and communicate by writing
What are the main functions of the temporal lobe?
Hearing and smell
What is the superior temporal gyrus?
Primary auditory cortex
Areas 41 and 42
What are the auditory association areas of the temporal lobe?
Posterior to 41 and 42
In dominant hemisphere is called the Wernicke’s area
Crucial for understanding for spoken word and has connections with other language areas
What is the main function of the occipital lobe?
Vision
What are the main areas of the occipital lobe?
On medial surface - on either side of calcarine sulcus is the primary visual cortex (area 17)
Rest is visual association cortex (areas 18 and 19) and concerned with interpretation of visual images
Where is the limbic lobe?
Medial surface of cerebral hemisphere has areas which together form functional limbic lobe
What is the function of the functional limbic lobe?
Memory and emotional aspects of behaviour
What does the limbic lobe include?
Cingulate gyrus, the hippocampus, parahippocampal gyrus, and amygdala
What are the language areas of the brain?
Broca’s area is the motor speech area
Wernicke’s area is auditory association in dominant hemisphere
What is aphasia?
Problem with speech due to damage to one or more speech areas in brain
What is Broca’s aphasia?
Understands speech but misses small works, is aware of difficulties
Damage to frontal lobe
Weakness/paralysis of one side of body
What is Wernicke’s aphasia?
Fluent speech, with new meaningless words as cant understand speech and doesn’t know of mistakes
Damage to temporal lobe
No paralysis
What are the 3 types of myelinated axon fibres bundled into tracts?
Commissural fibres
Association fibres
Projection fibres
What is the function of commissural fibres?
Connect corresponding areas of two hemispheres
What is the function of the association fibres?
Connects of part of cortex with other and may be short or long
Short connect primary and association areas
Long connect lobes
What is the function of projection fibres?
Run between the cerebral cortex and various subcortical centres
Pass through corona radiata and internal capsule
Describe a 3D cerebral tractography
3D modelling technique that maps functional white matter tracts using data collected using MRI
Based on symmetry of brain water diffusion
Describe the internal capsule
Made up of projection fibres passing to and from the cerebral cortex
Narrow area between thalamus and caudate nucleus medially and lentiform nucleus laterally
What is the blood supply of the internal capsule?
Middle cerebral artery and is frequently affected by strokes
Describe the basal ganglia
Subcortical nuclei (collection of neuronal cell bodies in grey matter) deep in each cerebral hemisphere
Made up of caudate nucleus, putamen and globus pallidus
Also a part is the substantia nigra
What are the individual basal ganglia?
Caudate (has tail)
Putamen (hard shell)
Globus pallidus (pale globe)
Substantia nigra (lies in midbrain)
Subthalamic nuclei
What makes up the lentiform nucleus?
Putamen and globus pallidus
Where is the caudate nucleus?
Starts as large head medial to internal capsule, a body and slender curving tail which follows curve of the lateral ventricle
What are the input regions of basal ganglia?
Caudate nucleus and putamen
Receive input from motor cortex, premotor cortex and thalamus
What are the output regions of basal ganglia?
Input region connected to output regions
Globus pallidus and substantia nigra
Where does the globus pallidus project to?
Primarily to the thalamus which sends fibres to motor area of cortex
What is the main function of the basal ganglia?
Help regulate initiation and termination of movements
They play a role in controlling the motor system - extrapyramidal system
What pathology can be associated with basal ganglia?
Parkinson’s, chorea and athetosis
