Introduction To The CNS And Functional Localisation Of The Cerebrum Flashcards
Why is white matter white
The presence of myelin
Describe the spinal cord
Rostrally continuous with brainstem
Extends from foramen magnum to L1-L2
Vertebral foramen
Ends at conus medullaris
Cauda equine
Surrounded by dura
Cervical and lumbosacral enlargements
Ascending ….. tracts
Sensory
Descending …… tracts
Motor
Differing amounts of gray matter correspond to……
Axons innervating lower and upper limbs
What are the 5 main divisions of the adult human brain
Forebrain - Telenchephalon and Diencephalon
Midbrain - Mesencephalon
Hindbrain - Metencephalon and Myencephalon
Components of the forebrain
Telencephalon -> cortex, limbic system, basal nuclei
Diencephalon-> thalamus, hypothalamus, subthalamus
What are the components of the mid brain
Tectum
Tegmentum
What are the components of the hindbrain
Metencephalon -> pons, cerebellum
Myelencephalon -> medulla
Describe the cerebrum
Divided into 2 cerebral hemispheres consist of the cerebral cortex, limbic system and basal nucleus
What are the 4 lobes of the cerebrum
Parietal, frontal, occipital, temporal
Describe the frontal lobe
Largest lobe
Location of the precentral gyrus where the primary motor areas are housed
Essential not only for regulating voluntary motor behaviour but also initiating it
Expressive or motor aspects of language also processed on the lateral surface in Broca’s motor speech area
What is Broca’s area
Located in inferior frontal gyrus
Generation of language
Lesion leads to Broca’s aphasia
What is Broca’s aphasia
Difficulty generating written or spoken language
Little difficulty with language comprehension
Describe the prefrontal area
Towards frontal pole of frontal lobe
Electrical stimulation does not elicit movement
Extensive connections with other lobes via fasciculi
Monitors behaviours and controls higher processs eg judgement
PF association areas which are concerned with emotion, motivation, personality
On the medial aspect of cingulate gyrus, important for modulating emotional aspects of behaviour
Why were prefrontal lobotomy’s carried out
Surgical intervention to separate prefrontal cortex from the rest of frontal lobe and thalamus for treatment of neuropsychiatric disorders
Icepick inserted through orbit
Symptoms often improved but patients left with severe mental deficits
Describe the parietal lobe
Important in regulating somatosensory functions
• Location of the postcentral gyrus where the primary somatosensory area is housed
• Involved in the initial cortical processing & perception of pain, temperature and proprioception
• Houses Wernickes’ area responsible for the receptive or sensory aspects of language
• Also concerned with spatial orientation and perception
What is Wernicke’s area
Located in superior temporal gyrus
Comprehension of language - lesion leads to Wernicke’s aphasia
What is wernicke’s aphasia
Lesion in wernickes area in superior temporal gyrus
Difficulty understanding written or spoken language
Person can generate speech but the language is meaningless - unconnected words
Describe the occipital lobe
Primarily involved in the processing of visual information
• Visual association areas surround and cover the lateral surface of this lobe
• Separated from the parietal lobe by the parieto-occipital sulcus
• Separated from the temporal lobe by the calcarine sulcus
Describe the temporal lobe
• Important for processing auditory information
• Superior temporal gyrus is an area where our ability to hear and interpret what we hear is processed
• The lateral surface functions for the perception of language.
• Anterior medial areas important in complex aspects of learning memory and emotion
What does the left brain control
Reading, writing
Decision making
Speech and language
What ones the right cerebral hemisphere relate to
Senses (touch, smell, sight, taste, feel)
Recognition (faces, voice inflections)
Where can you see grey matter
Outer layer (cortex)
Inner clusters (basal nucleus, thalamus)
Where would you see white matter
Tracts connecting cortex to nuclei
what connects cerebral hemispheres
Corpus callosum
What are white fibres
Relay information to and from specific areas
Referred to as association fibres
Short association fibres
Connect areas in adjacent gyri, across one or two sulci
Long association fibres
AKA fasciculi
Connect areas further apart ie cross more than 2 sulci
Commissural fibres
Cross the midline to connect areas of the cortex in one hemisphere with the same areas in the opposite hemisphere, connecting similar functional areas to enable co-ordination of activity between the two hemispheres
What is the biggest collection of commissural fibres
Corpus callosum
What is split-brain syndrome
Lesions in corpus callosum as a result of traumatic injury or surgical intervention (corpus callostomy)
Little effects on day to day life - deficits only revealed through testing
Loss of inter hemispheric transfer of information eg loss of coordination between right and left hands
Neuroplasticity
Projection fibres
Travel to or from the cortex to or from the thalamus or descend through the basal nuclei, brainstem or spinal cord
Converge as the internal capsule
Name of tracts follow pattern of where they begin and where they finish
What are the 3 types of cortical areas including examples
Motor areas - primary motor cortex
Sensory areas - primary somatosensory cortex
Association areas - approx 75% of the total surface area of the cerebral cortex
What are the 3 motor areas
Primary motor area
Supplementary motor area
Premotor area
Primary motor area
Precentral gyrus, somatotopy organised
Supplementary motor area
Motor maps for posture, efferent to anterior and lateral corticospinal tracts
Premotor area
Motor maos for movement of larger muscle groups, processes anticipates and plans voluntary movements
2 sensory areas
Primary somatosensory cortex
Somatosensory association area
Primary somatosensory cortex
Post central gyrus
Receives Afferent from dorsal columns, anterolateral and trigeminal pathways
Somatotopic organisation
Size of cortical representation correlated to tactile sensation of that part of the body
Histological organisation for the different types of peripheral receptors
Somatosensory association area
Critical for the interpretation of significance of sensory information
Lesions result in tactile agnostic - inability to interpret the significance of proprioceptive and tactile information
Astereognosis - inability to recognise an object placed in the hand
What are brodmann’s areas
52 areas defined by difference in neuronal cellular architecture
Correlation with cortical function
Where are deep structures of the cerebrum
Located under the cortical areas
Contains cell bodies and white matter tracts that connect various pats of the brain to one another
Gray matter brucellosis which of the basal nuclei and limbic system contribute
Basal nuclei
Group of interconnecting nuclei within the forebrain, Diencephalon and midbrain
Critical role in the initiation and control of voluntary movement
Include caudate & lenticular nuclei (putamen & globus pallidus), subthalamic nucleus and substantia nigra
Limbic system
Interconnected and interacting structures that play a significant role in drive related and emotional behaviours
Play a role in memory and learning. The deep forebrain structures of the limbic system which are located in the temporal lobe include the amygdala and the hippocampus
Describe Diencephalon
Consists of several sets of paired structures on either side of the 3rd ventricle
• Largest structure the thalamus also includes the hypothalamus, posterior pituitary gland and pineal gland
• The thalamus – sensory switchboard
• The hypothalamus – controls homeostatic, autonomic and endocrine functions
• Pineal body – produces melatonin and maintains circadian rhythm
• Habenular nucleus – regulates CNS neurotransmitters such as dopamine and serotonin. Has a role in the behaviour of addiction and motivation
What are the midbrain and hind brain
Components of the brainstem
Conduit for the ascending and descending tracts
Houses the cranial nerve nuclei
Areas regulate aspects of cardiovascular and respiratory function, cortical activity and consciousness
Describe the midbrain
Pair of cerebral peduncles
Provides important linkages between components of the motor system, particularly the cerebellum, basal nuclei and cerebral hemispheres
Contains substantia nigra, superior and inferior follicular and the red nucleus
What is the hind brain composed of
Pons and medulla oblong at a
What is the pons
Carries info from the poutine nuclei to the cerebellum
Involved in respiration taste and sleep and contains the substantia nigra, sup and inf colliculi and red nucleus
Describe the medulla oblongata
Merges with the spinal cord
Corticospinal fibres descend in pyramids on its anterior surface
Houses the Oliver y nuclear complex
Sensory tract fasciculus gracious and cunaeatus on posterior aspect
Hindbrain cerebellum description
Outgrowth of the pons
Outer surface is covered by the cerebellar cortex
• Has two hemispheres and a central area known as the vermis
• Contains a far greater number of neurons than any other subdivision of the brain although very few neuronal types
• Connected to the brainstem by the cerebellar peduncles and it receives somatosensory information from the spinal cord, motor information from the cerebral cortex and input about balance from the vestibular apparatus in the inner ear
• Is important for maintain posture and for coordinating head and eye movements and is also involved in fine tuning the movements of muscle and in learning motor skills
• Recent imaging studies have revealed that it is also involved in language and other cognitive functions
