Part 2 of 6 Anatomy Flashcards
Explain the specific functions of the different tracts of the motor system.
Pyramidal Tracts
Overarching function: simple voluntary movement
- Corticobulbar tract: cranial nerves, head and facial muscles
- Corticospinal tracts: upper limb, trunk, lower limb
Non-pyramidal Tracts
Generally, the rubro-, vestibulo-, reticulo-, tecto- spinal tracts are all involved in the innervation of trunk, but there are also more specific functions.
- Reticulo & vestibulo: maintain posture and balance by affecting axial muscles
- Rubro: control coarse limb movements by affecting flexor muscle
- Tecto: acts in conjunction with superior colliculi to mediate head, neck and eye movements in response to visual stimuli
(MM 18)
Trace the path of the corticospinal tract (one of the pyramidal pathways).
- See MM1 (p1, bk1)
Be able to identify the major landmarks on the medial brain. (Sagittal section of brain).
Major Landmarks:
- Sulci: calcarine, parietooccipital, central
- Gyri: parahippocampal, cingulate
- Areas:
- Lobes: occipital, frontal
- Thalamus, hypothalamus
- Pons, medulla, midbrain
- Cerebellum
See F585 - Major anatomical features of the medial brain.
Explain the organisation of grey matter in the cerebrum.
2 Areas of Grey Matter
- Cerebral Cortex
- Basal nucleibodies
Other Bodies
- Basal nuclei are subcortical collections of grey matter - the structure of the basal nuclei and their links to the tele-, dien- and mesen- cephalons are shown in the figure.
F586 - Basal ganglia structure and brain divisions.
Understand the structure and relations of the basal ganglia.
See F587 - Structure and relations of the basal ganglia.
What are the functions of the basal ganglia?
- Initiation and maintenance of voluntary movements (via a variety of pathways - indirect and direct)
- Inhibition of involuntary (unwanted) movements
- Memory
- Reward pathways
(MM 19)
Explain the organisation of the white matter in the cerebrum.
White Matter Organisaton
- Assocation fibres - connect areas of cortex within a single cerebral hemisphere
- Commissures - connect hemispheres e.g. corpus callosum - thick band of white matter-connects cerebral hemispheres
- Projection fibres - link cortex to diencephalon, brain stem, cerebellum and spinal cord
Association fibres are one way white matter is organised in the cerebrum. Describe the major association fibres in the brain.
Association fibres – connect different cortical areas of the same hemisphere. They run subcortically.
Major ones below:
- Superior longitudinal fasciculus: Connect Occipital, temporal, parietal and frontal lobes
- Inferior longitudinal fasciculus - connects occipital cortex with temporal (“What” loop of visual pathway)
- Arcuate fasciculus - connects Wernicke’s area with Broca’s area
- Short association fibres - between adjascent gyri
See F589 - Association fibres and white matter in the brain.
Commisural fibres are one way white matter is organised in the brain.
Describe the common structures which the commisural fibres form in the brain and which parts of the brain they connect.
Commissures - between 2 hemispheres
Structures Formed
- Corpus callosum (largest commissure) - connect different cortical areas of the 2 hemispheres
- Forceps minor (anterior forceps) connects the frontal lobes of the two hemispheres. Crosses midline via genu of corpus callosum.
- Forceps major (posterior forceps) connects the occipital lobes of the two hemispheres. Crosses midline via splenium of the corpus callosum.
- Common commisures and corpus callosum regions and the areas of the brain they link can be seen in F590 - Commisural fibres and the corpus callosum.
Projection fibres are one way white matter is organised in the nervous system. Explain the structures involved.
Projection fibres carry information from the cortext to other regions of the central nervous system, e.g. diencephalon, brain stem, cerebellum, spinal cord.
Structures Formed
- This figure shows the main projection fibre tracts which all run through the internal capsule
- All sensory and motor projection pathways run through the internal capsule
F591 - Projection fibres and the internal capsule
Briefly explain the functional organisation of the cerebral cortex (not whole brain).
Functional Organisation of Cerebral Cortex
- Primary Cortical Areas - Motor & Sensory
- Association Cortical Areas - Most developed part of cortex in human
- Unimodal association areas
- Motor
- Sensory
- Multimodal association areas
- Unimodal association areas
(MM 20)
Describe the organisation and location of the primary cortical areas in the cerebral cortex, i.e. the areas which are not the association areas.
See F592 -
Primary cortical areas – motor and sensory.
Primary Cortical Areas
- Motor
- Primary motor cortex: execution of movements
- 2 special motor cortices:
- Frontal eye field - voluntary mvt of eyes
- Broca’s area - present in one hemisphere nly, usualy left, motor speech area which directs muscles of speech production. Involved even in planning of speech.
- Sensory
- Primary general sensory cortex: touch, specifically localisation, intensity, texture
- Primary visual cortex: colours, edges, light and darkness
- Primary auditory cortex: hearing, specifically sound, pitch, tones
See F593 - Cerebral cortex functional organisation (see the red boxes for primary areas and orange for special areas)
There are 2 types of association areas in the brain - unimodal and multimodal. Explain the organisation, function and location of the unimodal association areas in the brain.
Unimodal Association Areas
Unimodal Sensory Association Areas
- Detailed perception of stimuli other than just simple shapes, contour, textures, tones and colours, for example:
- Temporal visual association area - recognition of faces, animals, vehicles, trees
- Temporal auditory association area - recognition of birds, voices
- Parietal somatosensory association area - stereognosis (3D perception), graphaesthesia (writing on skin), spatial awareness
Unimodal Motor Association Areas
- Complex movement planning
- Premotor areas: repetitive learned motor skills, e.g. playing an instrument, typing
- Supplementary motor areas
F593 - Cerebral cortex functional organisation (blue boxes)
There are 2 types of association areas in the brain - unimodal and multimodal. Explain the organisation, function and location of the multimodal association areas in the brain.
Multimodal Association Areas
1. Posterior MMAA
- Function:
- Spatial awareness, high order perception and language
- Wernicke’s area: involved in speech comprehension
- Location: Junction of occipital, temporal and parietal lobes.
2. Limbic MMAA
- Function: Receives input from sensory cortices - link sensory inputs with emotion + memory formation + learning.
- Location: Near limbic system
3. Anterior MMAA (Prefrontal Cortex)
- Function: Use info from unimodal association areas and MMAA for complex concept formation, planning, decision making.
- Location: Dorsolateral prefrontal cortex
F593 - Cerebral cortex functional organisation (see light pink regions - multimodal association cortex, also note location of Wernicke’s area)
F594 - Locations of multi-modal association areas.
Explain the location of the uni-modal association areas with relation to the primary areas of the cerebral cortex.
- Unimodal association areas are adjacent to the primary areas.
- Remember the unimodal association areas are:
- Sensory unimodal association areas: somatosensory, visual, auditory
- Motor unimodal association areas: supplementary motor, premotor
See F595 - Uni-modal AA relation to primary cortical areas.
What is the somatotopic map/ homunculus?
- The primary cortical areas, as you may recall, are:
- Motor
- Somatosensory
- Both of these primary cortical areas have representative areas of the body. (Somatotopy is the point-for-point correspondence of an area of the body to a specific point on the central nervous system.)
- Distribution is not equal, e.g. parts of the body requiring delicate or finely controlled movements have larger portions of the homunculus, such as the face and hands.
- Somatotopic arrangement can also be seen in subcortical areas - internal capsule, thalamus, spinal cord.
See F596 - Somatotopic map/ homunculus - primary cort. areas.
Explain briefly the processes in your brain which would happen if you accidentally smashed a bottle of acid on your foot and ran to the lab shower.
See it shatter (visual cortex) –> heart the crash (auditory cortex) –> feel the skin burning (somatosensory cortex) –> posterior MMAA process the info –> limbic MMAA allows remembering of instructions to run to the shower –> prefrontal MMAA uses all this information to make the decision to run to the shower –> motor output.
(MM 21)
Explain the lateralisaton of cortical function.
- Both cerebral hemispheres are used for almost every activity and hemispheres appear identifcal, but lateralisation is actually present, i.e. each hemisphere has unique abilities not shared by its partner.
- Cerebral dominance refers to the hemisphere that is dominant for language (90% people = left hemisphere has greater control over language abilities, other 10%, roles are reversed or equal usually left-handed or male)
Left hemisphere
- Language
- Analytical process - science, math
- Detail
Right hemisphere
- Spatial awareness
- Musical, artistic
- Overall picture
Explain the function of the frontal lobe and what you would expect if the frontal lobe was dysfunctional.
F597 - Frontal lobe function and dysfunction
Explain the function of the parietal lobe and what you would expect if the parietal lobe was dysfunctional.
F598 - Parietal lobe function & dysfunction.
See also the picture of the ‘interlocking finger test’, which is shown by the examiner to the patient to see whether the patient can mimic the hand positions shown. Poor performance correlates well to parietal lobe dysfunction. There is also a picture there showing unilateral visual neglect.
