The Brain

Question 1

1. what is the general role of the cerebellum?

2. what is the general role of the basal ganglia

Answer 1

1. co-ordination of ongoing movement

2. selection/initiation of voluntary movement

Question 2

1. what are the ridges/folds of the cerebellum called?
2. what are the name of the nuclei found within cerebellar white matter?
3. what is the comparator function of the cerebellum?
4. what is the motor memory function of the cerebellum?

Answer 2

1. folia
2. deep cerebellar nuclei
3. detects differences in motor error (i.e. between intended and actual movement) and subsequently provides correction
4. stores learned movements. Conscious voluntary movements eventually become unconscious and involuntary

Question 3

1. where does the cerebrocerebellum receive inputs from?
2. what is the cerebrocerebellum involved in?
3. where does the spinocerebellum receive inputs from?
4. what is the spinocerebellum involved in?
5. what structures make up the vestibulocerebellum
6. where does the vestibulocerebellum receive inputs from?
7. what is the vestibulocerebellum involved in?

Answer 3

1. cerebral cortex
2. regulation of highly skilled movements
3. spinal cord
4. control of movements; somatotopically arranged (lateral parts concerned with distal muscles; medial parts concerned with proximal musclea)
5. nodulus and flocculus
6. vestibular nuclei in brainstem
7. movements underlying balance and posture

Question 4

1. where do motor inputs from the cerebral cortex enter the cerebellum via?
2. how do sensory inputs from spinal cord and vestibular nuclei enter the cerebellum? (contralaterally or ipsilaterally?)
3. what is the role of the inferior olive?
4. what are the major output structures of the cerebellum?
5. where do these outputs relay info to?
6. what do the following use as their output?
   a) vestibulocerebellum
   b) spinocerebellum
   c) cerebrocerebellum

Answer 4

1. relay neurons in the pons. They decussate and relay info to contralateral cerebellum
2. ipsilaterally
3. relay modulatory inputs re timing, learning, and memory to contralateral cerebellum
4. deep cerebellar nuclei
5. ventrolateral complex of the thalamus
   6a) fastigial nucleus
   6b) interposed nuclei
   6c) dentate nuclei

Question 5

1. which cells are the input cells of the cerebellum?
2. which cells are the interneurons?
3. which cells are the output cells?
4. describe the microcicuitry of the cerebellum

Answer 5

1. mossy fibres (and climbing fibres which receive input from inferior olive)
2. granule cells
3. purkinje cells
4. granule cells receive excitatory input from mossy fibres. They branch in a T shape in the molecular layer (parallel fibres), and synapse onto purkinje cells
   purkinje cells cells use GABA and synapse onto deep cerebellar nuclei
   climbing fibres twist around the dendrites of purkinje cells and make multisynaptic connections. they alter the effectiveness of parallel inputs to the pukinje cell.

Question 6

1. what type of movements occur in response to cerebellar damage?
2. on what side of the body are movement errors found?
3. what is the effect of:
   a) vestibulocerebellar damage?
   b) spinocerebellar damage?
   c) cerebrocerebellar damage?
4. what part of the cerebellum is damaged by alcohol? What are the effects of this?

Answer 6

1. movements become jerky, imprecise, slow and unco-ordinated
2. same side
   3a) disturbances of balance and eye movements
   3b) impaired gait
   3c) impairments in highly skilled sequences of learned movemebnts
3. anterior cerebellum. Particularly affects the movements of the lower limbs (due to somatotopic arrangement of the cerebellum)

Question 7

1. which nuclei make up the striatum?
2. which nuclei make up the pars retuiculata?
3. which of the above are the a) input of the basal ganglia? b) output of the basal ganglia?
4. name 3 functions of the basal ganglia

Answer 7

1. caudate nucleus and putamen
2. globus pallidus, substantia nigra and subthalamic nucleus
   3a) striatum
   b) pars reticulata
3. modulate excitatory commands from motor cortex to control initiation and termination of movement
   selection and maintenance of voluntary movement
   non motor functions such as cognition, working memory and attention

Question 8

1. describe corticostriatal inputs into the basal ganglia
2. describe nigrostriatal inputs into the basal ganglia
3. are outputs from the basal ganglia excitatory or inhibitory?
4. which outputs control eye movements?
5. which outputs control limb and trunk movements

Answer 8

1. inputs from cerebral cortex to striatum. Excitatory (glutamate)
2. inputs from substantia nigra to the striatum. Use dopamine to modulate commands from cortex
3. inhibitory
4. outputs via substantia nigra to superior colliculus
5. outputs via globus pallidus interna to motor cortex

Question 9

1. what is the outcome of the direct pathway?
2. what is the outcome of the indirect pathway
3. what dopamine receptors are used in each pathway? What is the effect of dopamine on these receptors?
4. describe the direct pathway
5. describe the indirect pathway
6. what is the overall effect of dopamine on both pathways?

Answer 9

1. removal of inhibition on the thalamus, thus enabling the initiation of movement
2. increase inhibition of the thalamus, thus preventing movement
3. direct - D1 receptors; excitatory effect
   indirect - D2 receptors; inhibitory effect
4. GP tonically inhibits the thalamus. Commands from cerebral cortex excite the striatum. Striatum inhibits the GP therefore thalamus is disinhibited. Substantia nigra facilitates this pathway via D1 receptors
5. commands from cerebral cortex excite the striatum. Striatum inhibits the GPe. GPe inhibits GPi which tonically inhibits the thalamus. Effect of Striatal excitation is increased inhibition of thalamus
   GPe also inhibits Subthalamic nucleus which excites the GPi. Inhibition of the GPe disinhibits the STN, increasing inhibition of GPi on thalamus.
6. Dopamine excites the direct pathway and inhibits the indirect pathway, with a net effect to increase facilitatory inputs to the motor regions.

Question 10

1. Name 4 clinical characteristics of parkinson’s disease
2. describe the neuropathology of parkinson’s
3. How does L-DOPA act pharmacologically
4. what are the side effects of L-DOPA treatment?
5. Describe 3 other treatments for parkinson’s

Answer 10

1. tremor. muscle rigidity, akinesia. postural problems
2. degeneration of neurons in the substantia nigra, leading to decrease in dopamine availability.
   Results in decreased activity of the direct pathway and increased activity in the indirect pathway
3. as a precursor of dopamine, it raises dopamine availability.
4. drug resistance, involuntary movements and psychosis
5. dopamine agonists - have many side effect such as sudden sleepiness
   foetal stem cell transplants - transplantation of foetal stem cells into putamen to increase production of dopamine
   deep brain stimulation/surgery

Question 11

1. what does the central sulcus divide?
2. what does the lateral sulcus divide?
3. what does the longitudinal fissure divide?
4. which cortex is found anteriorly to the central sulcus?
5. which cortex is found posteriorly to the central sulcus?
6. In terms of somatotopic arrangement:
   a) where is the head and neck represented?
   b) where is the trunk and upper limb prepresented?
   c) where is are the lower limbs represented?

Answer 11

1. frontal and parietal lobes
2. parietal and occipital lobes from temporal lobe
3. left and right cerebral hemispheres
4. motor cortex (precentral gyrus)
5. somatosensory cortex (postcentral gyrus)

6a) laterally
6b) middle
6c) medially

Question 12

1. within the circle of willis, where is:
   a) anterior cerebral artery
   b) middle cerebral artery
   c) posterior cerebral artery
2. what parts of the brain do the following arteries supply?
   a) anterior cerebral artery
   b) middle cerebral artery
   c) posterior cerebral artery
3. what is the effects of disruption of the following arteries?
   a) anterior cerebral artery
   b) middle cerebral artery
   c) posterior cerebral artery

Answer 12

1a) top of the circle of willis
1b) continuation of the internal carotid artery
1c) base of circle of willis

2a) medial surface of the cerebral hemisphere (controls the lower limbs) up to the parieto-occipital sulcus
2b) lateral surface of the cerebral hemisphere (controls the upper body)
2c) temporal and occipital lobes

3a) contralateral lower limb weakness/hemiplegia
contralateral sensory loss
contralateral hemoneglect
frontal lobe behavioural abnormalities
BEHAVIOURAL AND LOWER LIMB DYSFUNCTION
3b) contralateral upper limb weakness
hemianaesthesia
language difficulties
ipsilateral gaze preference and hemianopia
LANGUAGE AND UPPER LIMB DYSFUNCTION
3c) contralateral homonymous hemianopia (loss of visual field on one side)
larger infarcts affecting the thalamus may cause contralateral hemisensory loss and hemiparalysis
VISUAL DYSFUNCTION

Question 13

Describe the overall process of initiating a movement

Answer 13

1. sensory input regarding the state of the limb we want to move - proprioception and touch
2. planning of movement in prefrontal cortex
3. sequencing of movement in in supplementary motor and premotor cortcies
4. generation of signal in motor cortex based on sensory info
5. basal ganglia enables initiation of movement
6. fine tuning from cerebellum based on sensory/proprioceptive information

Question 14

1. apart from primary motor cortex (area 4), name 2 other areas involved in motor control. What are their roles?
2. apart from the primary somatosensory cortex, name 2 other areas involved in sensory perception. What are their roles?
3. what are the effects of lesions in areas:
   a) 4
   b) 6
   c) 8
   d) 1/2/3
   e) 40
   f) 39

Answer 14

1. 6 - premotor cortex - planning of complex movements
   8 - movement planning
2. 5 - somatosensory asssociation area
   40 - somatosensory association cortex
   Both are involved in sensory processing

3a) contralateral flaccid paralysis with babinski’s sign
3b) contralateral spasticity and increased reflexes
3c) unilateral gaze preference
d) contralateral decrease in touch sensations and proprioception
e) contralateral hemineglect, apraxia and tactile/proprioceptive agnosia
f) alexia/dyslexia

Question 15

1. Name and describe the functions of the 2 key areas in speech and language
2. what are the effects of lesions in these areas?
3. what is the name of the fibres that connect these 2 areas
4. what is global aphasia and what is it a result of?

Answer 15

1. Brocca’s area - language production/expression (motor)
   Wernicke’s area - language comprehension/reception
2. broca’s - motor aphasia - understands language but can’t speek
   wernicke’s - sensory aphasia - can speak but can’t understand language
3. arcuate fasiculus
4. inability to produce and understand language. Result of lesions affecting both regions (stroke of middle cerebral artery)

Question 16

1. where is the hearing area found?
2. what area is this next to?
3. why does a lesion in one hemisphere not result in unilateral hearing loss?
4. where is the visual cortex found?
5. what is the role of visual association areas?

Answer 16

1. deep within lateral sulcus
2. next to wernicke’s area
3. because hearing is represented bilaterally
4. 2 gyri either side of the calcarine sulcus on the medial surface of the occipital lobe. This is perpendicular to the parieto-occipital sulcus
5. help us identify what we have seen

Question 17

1. what does the prefrontal cortex have links to?
2. what is the role of the prefrontal cortex? (6)
3. what are the effects of lesions in the prefrontal cortex? (7)

Answer 17

1. all parts of the neocortex (except primary motor and sensory areas) and thalamus and limbic system
2. HIGHER INTELLECTUAL FUNCTIONS
   - abstract thinking
   - decision making
   - prioritising and sequencing
   - increase adaptive and decrease maladaptive functions
   - goal directed behaviour
   - inhibitions
3. • disinhibition
     - changes in personality and social function
     - decreased concentration
     - decreased judgement
     - decreased abstract thought
     - decreased problem solving ability
     - decreased initiative

Question 18

1. which hemisphere is dominant in terms of language production in most people?
2. what handedness is more likely to have bilateral representation of language?
3. in terms of language, what is the role of the non-dominant hemisphere?

Answer 18

1. left (>95% of right handed people and >60-70% of LH people)
2. left
3. non verbal functions relating to language such as imparting emotional significance to language.

Question 19

1. name the 2 layers that make up the dura mater
2. name the 4 dural partitions and where they divide the cranial cavity
3. where is the extradural space found?
4. what is an extradural haematoma?
5. what is a subdural haematoma?
6. where is the subarachnoid space?
7. where are the dural venous sinuses found?

Answer 19

1. outer periosteal layer and inner menningeal layer
2. FALX CEREBRI - downward projection in the longitudinal fissure
   TENTORIUM CEREBELLI - horizontal projection that separates the cerebellum from cerebrum
   FALX CEREBELLI - midline projection between the 2 cerebellar hemispheres
   DIAPHRAGMA SELLAE - dural projection that covers the sella turcica of the sphenoid bone
3. between dura mater and bone
4. bleeding into extradural space due to rupture of menningeal artery or torn dural venous sinus
5. bleeding into the subdural space (between dura mater and arachnoid mater) Bridging veins cross this space.
6. between arachnoid mater and pia mater
7. between the 2 layers of the dura mater