Cerebral Hemispheres Flashcards
Describe the general features of the cerebrum
Sulcus = dip Gyrus = elevation Fissure = larger dip
Gray matter on the surface.
White matter inside.
Basal Ganglia (collection of neuronal cell bodies buried in the white matter)
Lateral ventricle is the cavity in each hemisphere
Is the pattern of sulci and gyri variable?
Yes
Change pattern depending on what you use your brain for
Some sulci and gyri are constant features
What is the corpus callosum?
Bridges the two cerebral hemispheres
What sulci can you see on the cerebrum?
Just above temporal lobe is the lateral sulcus
Joint to this is the central sulcus which runs to the medial surface of the cerebrum
On the medial surface the cingulate sulcus can be seen above the corpus callosum.
The pirate-occipital sulcus can be seen at the back
This divides the brain into frontal, parietal and occipital and temporal lobes
What gyri can you see on the cerebrum?
Precentral gyrus:
-Just anterior to central sulcus
Postcentral gyrus:
-Just posterior to central sulcus
Cingulate gyrus:
- Superior to corpus callosum
- Inferior to cingulate sulcus
Where is the hippocampus located?
Medial end of temporal lobe which curls into itself
What structures are inside the lateral sulcus?
Transverse temporal gyri
Insula
What is the difference between different Brodmann Areas?
Each broaden area has a different function and therefore different cellular makeup
Describe the functional areas of the cortex
Posterior part of the cerebral hemisphere is sensory while the anterior part is motor.
Medial portions of the cerebral hemisphere (limbic system)
-Storage and retrieval of processed information
Dominant and non-dominant hemisphere for different tasks
There are primary sensory areas and adjacent association areas
What does the frontal lobe do?
Motor function
Intellect
What does the parietal lobe do?
Somatosensory
What does the occipital lobe do?
Vision
What does the temporal lobe so?
Hearing and smell
What does your Precentral gyrus do?
Area 4: Primary Motor Cortex
(Frontal lobe)
Somatotropic representation of contralateral half of body through motor homunculus
What does the inferior frontal gyrus do?
Area 44, 45
Broca’s area of motor speech
Frontal lobe
What does the prefrontal cortex do?
Cognitive functions of higher order- intellect, judgement, prediction, planning
Frontal lobe
What does the post central gyrus do?
Areas 1, 2, 3
Primary sensory area
(Parietal lobe)
Receives general sensations from contralateral half of body.
Somatotopic representation through sensory homunculus
What does the superior parietal lobule do?
Interpretation of general sensory information (sensory association area) and conscious awareness of contralateral half of body
can recognise what you touch
What does the inferior parietal lobule do?
Interface between somatosensory cortex and visual and auditory association areas.
IN DOMINANT HEMISPHERE, CONTRIBUTES TO LANGUAGE FUNCTIONS
What can a parietal lobe lesion cause?
Hemisensory neglect
Inability to be aware of opposite side of body.
Will not even know that side is there
What does the superior temporal gyrus do?
Areas 41, 42
Primary auditory complex
Heschl’s convolusions
What are the auditory association areas of the temporal lobe?
Posterior to 41, 42.
In dominant hemisphere -> Wernicke’s area
Crucial for understanding of spoken word.
has connections with other language areas.
What does the inferior surface of the temporal lobe do?
Receives fibres from olfactory tract
Conscious appreciation of smell
Where is the primary visual cortex?
On the medial surface of the occipital lobe, on either side of the calcimine sulcus is the primary visual cortex
(Area 17)
Apart from the primary visual cortex what else does the occipital lobe do?
The rest of the occipital lobe is the visual association cortex concerns with interpretation of visual images.
(Areas 18, 19)
What is the limbic lobe?
The medial surface of the cerebral hemisphere has areas which together form a functional limbic lobe involved in memory and emotional aspects of behaviour.
It includes the cingulate gyrus, the hippocampus (medial aspects of temporal lobe), parahippocampal gyrus and the amygdala (subcortical grey matter close to temporal pole)
Describe the language areas of the brain
Broca’s area is the motor speech area.
Wrenches’ area is the auditory association area necessary for recognition of the spoken word.
Is in the dominant hemisphere.
What is aphasia?
Problem with speech due to damage to one or more speech areas in the brain
Describe Broca’s aphasia
“Walk Dog”
Understands speech
Misses small words
Aware of difficulties in speech
(can’t put thoughts into words)
Damage to frontal lobe
Weakness/paralysis of one side of body
Wernicke’s aphasia
“You know that smoodle pinkered and that i want to get round him like you want before”
Fluent speeach, with new meaningless words, can’t understand speech, doesn’t know of mistakes
Damage to temporal lobe
No paralysis
There are 3 types of myelinated axon fibres bundles into tracts. What are they?
- Commisural fibres
- Association fibres
- Projection fibres
What are commisural fibres?
- Connect corresponding areas of the two hemispheres
- Corpus Callosum
What are association fibres?
- Connect 1 part of the cortex with the other (same hemisphere).
- They may be short or long
What are projection fibres?
Run between the cerebral cortex and various subcortical centres.
They pass through the corona radiata and the internal capsule
What is the internal capsule?
Made up of projection fibres passing to and from the cerebral cortex
It is a narrow area between the thalamus and caudate nucleus medially and the lentiform nucleus laterally.
It derives blood supply from the middle cerebral artery and is frequently affected in a stroke
Why is an internal capsule stroke so dramatic?
All projection fibres coming from the cerebral cortex to the spinal cord must come through these two channels in the diencephalon.
If there is a stroke there will be massive effects to the contralateral side of the body
What are the basal ganglia?
Subcortical nuclei (collection of neuronal bodies - grey matter) deep within each cerebral hemisphere.
made up of the caudate nucleus, putamen and globes plallidus
Substantia nigra in midbrain is functionally part of them though not anatomically
What are the individual basal ganglia?
CAUDATE (one with a tail)
The PUTAMEN (means the hard shell)
GLOBUS PALLIDUS (the pale globe
The hard shell + the globe forms a lens like structure - the LENTIFORM NUCLEUS
SUBSTANTIAL NIGRA (the black substance, lies in the midbrain!)
The SUBTHALAMIC NUCLEII
What is the topographical anatomy of the basal ganglia?
The caudate nucleus starts as a large head medial to the internal capsule, a body and a slender curving tail which follows the curve of the lateral ventricle.
lateral to the internal capsule is the lentiform nucleus made up of the putamen laterally and globes plaids medially
How can you find the lateral ventricle, internal capsule, thalamus and lentiform nucleus on a brain section?
Identify the lateral ventricles and a third ventricle (if present)
Lying in the wall of the lateral ventricle is the caudate nucleus
Lying beside the third ventricle is the thalamus (diencephalon)
lateral to the caudate and thalamus lies the internal capsule
lateral to the internal capsule is the lentiform nucleus made up of the globes plaids medially and the putamen laterally
What are the connections of the basal ganglia?
- the caudate nucleus and the putamen are the “input regions” receiving input from the motor cortex, premotor cortex and from thalamus
- They are in turn connected to the output regions (the globes plaids and substantial nigra)
- The globes plaids then projects primarily to the thalamus (which in turn sends fibres to motor area of cortex)
What does the basal ganglia do?
The major function is to help regulate initiation and termination of movements.
Because they play a role in controlling the motor system they are often referred to as the “extrapyramidal system”
What is the pathology of the basal ganglia?
Parkinson’s
Chorea
Athetosis etc
