Block 5 - Musculoskeletal and Nervous System 2 Flashcards
What does the cerebellum do?
Coordination and refining of movements by detecting motor errors Motor memory (conscious and unconscious learned movements)
What does the basal ganglia do?
Selection and initiation of voluntary movements
Cognition, attention and working memory
What do the cerebellum and basal ganglia do together?
Increase the accuracy of movements by providing feedback loops to motor and sensory areas in the cortex to modify signals from UMN
What are the two pathways for signals to leave the cerebral cortex by?
Cerebral cortex - Brainstem - Spinal cord - Body - Movement
Cerebral cortex - Basal ganglia + Cerebellum - Thalamus - Cerebral cortex
Where is the cerebellum located?
In the hindbrain underneath the cerebral cortex
What is the structure of the dorsal surface?
What is this called?
Folded
Folia
What does damage of the cerebellum lead to?
Jerky, uncontrolled and inaccurate movements
IPSILATERAL (SAME SIDE)
What does damage of the basal ganglia lead to?
Uncontrolled and decreased movements at rest
What are the 3 parts of the cerebellum?
What do they do?
Where are they found?
Cerebrocerebellum: Inputs from the cerebral cortex; regulated high skilled movements and sequences
(2 SIDES)
Spinocerebellum: Input from the spinal cord
(MIDDLE)
Vestibulocerebellum: Inputs from the vestibular nuclei in the brainstem to coordinate movement, balance and posture. Made from foccules and nodules
(BOTTOM)
How is the cerebellum attached to the pons?
By peduncles
What are the three cerebellar peduncles?
Which pathways are they involved in?
Where do they project to?
Superior cerebellar peduncles: Efferent pathway - Midbrain
Middle cerebellar peduncles: Afferent pathway - Pons
Inferior cerebellar peduncles: Efferent and Afferent - Medulla + Spinal cord
What are two motor input pathways to the cerebellum?
Where do they decussate?
Cerebral cortex - Pontine nucleus (DECUSSATE) Cerebellum
Cerebral cortex - Red nucleus - Inferior olive (DECUSSATE) Cerebellum
What is the sensory input pathway to the cerebellum?
Does this pathway decussate?
Spinal cord/Vestibular nucleus - Inferior cerebellar peduncle - Cerebellum
Does NOT decussate
What is the output pathway from the cerebellum?
Cerebellum - Deep cerebellar nuclei (DECUSSATE in superior cerebellar peduncle) - Thalamus - Primary + premotor cortex
What are the deep cerebellar nuclei?
What do they do?
Output structures in the white matter
Relay corticol cerebellar information to the motor cortex and brainstem as a feedback mechanism to correct movement
What are the 2 output pathway for the vestibulocerebellum?
Fastigial nucleus - Medial descending systems - Motor execution
Vestibular nuclei - Balance and eye movements
What is the output pathway for the spinocerebellum?
Interposed nucleus - Lateral descending systems - Motor execution
What is the difference between lateral and medial descending systems?
Lateral = LIMBS Medial = TRUNK
What is the output pathway for the cerebrocerebellum?
Denate nucleus - Motor + premotor cortex - Motor planning
What are the 2 input pathways to the cerebellum?
Cerebral cortex, spinal cord and vestibular system –> Mossy fibres which synpase onto granule cells –> Parallel fibres which synapse with purkinje fibres
Inferior olive –> Climbing fibres which synapse with purkinje fibres
What is the output pathway from the cerebellum?
Purkinje fibres synapse onto neurones in the deep cerebellar nuclei –> GABA –> Thalamus and motor cortex
What are the interneurones in the cerebellum?
Granule, Satellite, Golgi and Basket cells
What happens if there is a lesion in the vestibulocerebellum?
Damage to balance and eyes
What happens if there is a lesion in the spinocerebellum?
Impaired gait and decreased smoothness of movement
What happens if there is a lesion in the cerebrocerebellum?
Impairments in highly skilled sequences
What is sent to sensory neurones before you tickle yourself?
An efference copy
What does alcohol degenerate in the cerebellum?
Which limbs are affected?
The anterior cerebellum
Lower limbs affected
What is cerebellar ataxia?
Jerky, imprecise and uncoordinated movements
What is Dyssynergia?
Patients move joints separately, not simultaneously
What is Dysmetria?
The inability to judge distance
What is Dysdiadochokinesia?
You can’t do rapid, alternating movements
What is an intention tremor?
A tremor when you’re moving
What is ataxicdysarthria?
Slurred speech
Where is the basal ganglia?
What is it?
Underneath the cerebral cortex but outside the thalamus
A collection of functionally distinct nuclei
What is the input zone to the basal ganglia?
Caudate nucleus and putamen –> Striatum
What is the output zone to the basal ganglia?
Globus Pallidus and substantia nigra –> Pars Reticula
What excites and inhibits the basal ganglia?
Excities: Glutamate from the motor cortex
Inhibits: Basal ganglia and feedback mechanisms
What are the three input pathways to the Basal Ganglia?
What neurotransmitter is involved with 2 of them?
Corticostriatal pathway: Cerebral cortex –> Striatum (Glutamate)
Nigrostriatal pathway: Substantia Nigra –> Striatum (Dopamine)
Medium spiny neurones: Inputs to the striatum
What are the two output pathways from the basal ganglia?
Striatum - Substantia Nigra - Superior colliculus - Eye movements
Striatum - Globus pallidus - limb and trunk movements - thalamus - motor cortex
What does the globus pallidus do to the thalamus?
What does this mean for movement?
Globus pallidus inhibits the thalaus causing decreased excitation of the motor cortex and decreased movement
What happens when the substantia nigra release dopamine and it binds to D1 in the striatum?
What pathway is this?
Removes inhibition of the globus pallidus
Thalamus excites the motor cortex
Movement occurs
DIRECT PATHWAY
What 2 things happen when the substantia nigra release dopamine and it binds to D2 in the striatum?
What pathway is this?
Decreases inhibition on the globus pallidus causes increased inhibition of the thalamus
Decreased inhibition of the subthalamic nucleus leads to increased excitation of the subthalamic nucleus and increased inhibition of the thalamus
Thalmus sends no signal to the motor cortex causing no movement
INDIRECT PATHWAY
2 causes of Parkinson’s disease?
Idiopathic
Genetic
What type of disorder is Parkinson’s?
4 symptoms?
Hypokinetic (can't initiate movement) T: Tremor of hands R: Rigidity of muscles A: Akinesia (no movement) P: Postural problems
What happens in Parkinson’s disease?
Degeneration of neurones in the substantia nigra causes a decrease in dopamine
Decreased excitation of the direct pathway
Decreased inhibition of the indirect pathway
Increased inhibition of the thalamus and decreased movement
2 types of surgery used to treat Parkinson’s?
Stem cell transplant to the putamen
Brain surgery to inactivate or remove the globus pallidus or thalamus
What happens during Huntington’s disease?
2 symptoms and the type of disorder
What drugs are used?
Loss of output from neurones in the striatum
Hyperkinesia: Excessive and uncontrolled movements
Drugs to DECREASE dopamine levels
What happens in Hemiballismus?
3 symptoms
Death of striatal inputs to to globus pallidus decreases inhibition of the subthalamic nucleus and decreases excitation of the globus pallidus causing inhibition of the thalamus
Rapid, flinging and violent movements of the limbs
What are Gyri?
Mounds of the brain
What are Sulci?
Grooves in the brain
What are Folia?
Mounds on the cerebellum
What lobes does the central sulcus separate?
Frontal and partietal
What does the longitudinal fissue separate?
The right and left hemispheres
Which is motor and sensory: the precentral or postcentral gyrus?
PREcentral gyrus = MOTOR
POSTcentral gyrus = SENSORY
How many hemispheres does the cerebellum have?
2
What is the Flocculondular system involved in?
What does it project to?
Equilibrium and muscle tone
Projects to the vestibular system
Where is the Paleocerebellum?
What does it cause?
Anterior hemisphere and vermis
Propulsive and stereotyped movement
What does the Neocerebellum cause?
Coordination of skilled and voluntary movement
What do the medial, superior and lateral parts of the homunculus control?
Medial: Pelvis and lower limbs
Superior: Trunk
Lateral: Face and upper limbs
What is the anterior and posterior supply to the brain?
What cerebral arteries do they form?
Where do they join?
Anterior: Internal carotid artery –> Anterior and middle cerebral arteries
Posterior: Vertebral artery –> Basilar artery –> 2 posterior cerebral arteries
Join at the Circle of Willis
Which cerebral arteries supply the lower and upper regions of the body?
How?
Anterior: Lower
Middle and posterior: Upper
By supplying areas of the homunculus
What does a lesion in the middle cerebral artery cause?
Contralateral upper limb weakness
Hemiplegia (contralateral paralysis)
Hemianaethesia
What does a lesion in the anterior cerebral artery cause?
Contralateral lower limb weakness
Hemiplegia (contralateral paralysis)
Cortical-type sensory loss
What does a lesion in the posterior cerebral artery cause?
Contralateral hemisensory loss
Hemiparesis (loss of vision fields)
What is the pathway of the Dentatorubrothalamocortical pathway?
Does it decusate?
What is its role?
Cerebellum - dendate nucleus - red nucleus - thalamus - motor and somatosensory cortex
DECUSSATES
To refine movement
How does the brain make a somatosensory map?
What is the somatosensory map of?
Through ascending tracts
Of what the limbs are doing
What is lost during disconnection syndromes?
White matter
How many regions of the brain are there?
49
How are the different regions of the brain distinguished between?
Histological differences
What fibres link the right and left side of the brain?
Commisural fibres
What fibres link the same side of the brain?
Associated fibres
Which area of the brain is the primary motor cortex in?
Area 4
Which area of the brain is the supplementary motor cortex in?
Area 6
Which ares of the brain is the somatosensory cortex in?
Areas 1, 2 and 3
Which areas of the brain is the associated areas of the somatosensory cortex in?
39 and 40
What do lesions in area 4 cause?
Contralateral flaccid paralysis
Babinski
What do lesions in area 6 cause?
Contralateral spasticity
Increase in deep tendon reflexes
What do lesions in area 8 cause?
Difficulty moving the eye to the opposite side
lesion in left = eye cannot move to the right
What do lesions in area 1,2 and 3 cause?
Contralateral loss of touch, pressure and proprioception
Decreased pain in sensory areas
What do lesions in area 40 cause?
Tactile and proprioceptive dystonia (can’t tell what things are when you touch them)
Contralateral loss of left to right discrimination
Hemineglect
Apraxia
What do lesions in area 39 cause?
Akesia
Dyslexia
Agraphia (can’t write)
Which hemisphere is language controlled by?
Left
What is the dominant hemisphere involved with?
- language
- motor
- maths
- music
- surroundings
Speech Skilled motor formation Analytical arithmitic Trained musical ability Following directions
What is the non-dominant hemisphere involved with?
- language
- motor
- maths
- music
- surroundings
Emotion Spacial analysis and attention Estimation and lining up of numbers Untrained musical ability Spacial orientation
What could Karl Wernicke’s patient do/not do?
Where was the lesion?
What condition did they have?
What was their hearing, speech and understanding like?
- Hear and speak fluently but not understand
- The lesion was at the junction of the temporal , parietal and occipital lobes
- Receptive/sensory aphysis
What could Pierre Broca’s patient do/not do?
Where was the lesion?
What condition did they have?
What was their hearing, speech and understanding like?
- They could understand language, know how to respond and move but could not speak
- Lesion in posteroinferior frontal lobe
- Expressive/motor aphysis
What is agraphia?
Slow and laboured speech
Where is the site in the brain for hearing?
Primary auditory cortex in the lateral fissure next to the language perception area
What happens to hearing if there is a one sided lesion?
Why?
There is no hearing loss as hearing is bilateral
What are the 3 tracts in the prefrontal cortex?
Neocortex, thalamus and limbic system
What 6 things is the prefrontal cortex involved in?
Decision making, goal directed behaviour, planning, prioritising, sequencing, thinking
What does a lesion in the prefrontal cortex lead to?
Disinhibition
Personality and concentration change
Higher intelligence
Less shy
What functions does the middle cerebral artery supply?
Speech, language and hearing
Also supplies the frontal eye fields
What area does the anterior cerebral artery supply?
Basal ganglia, internal capsule and prefrontal cortex
What function does the posterior cerebral artery supply?
Vision
What % of blood to the brain does the middle cerebral artery supply?
60-80%
What areas of the brain does the middle cerebral artery run to?
Basal ganglia, internal capsule and thalamus
What is Homohymous Hemianopia?
Loss of a field of view in both eyes
What is Global Aphasia?
A language disorder
What is contralateral hemineglect
You are unaware of the side of your body opposite to the lesion
What is Ipsilateral gaze preference
The eyes point towards the lesion
What is Anosognosia
A decrease in self awareness
How does the anterior cerebral artery supply the internal capsule and basal ganglia?
By the medial striate artery (of Heubner)
What function does the anterior cerebral artery supply?
Defecation
What is vision controlled by?
The medial surface of the occipital lobe
Perpendicular to the parieto-occipital sulcus near th calcarine sulcus
What is visual agonsia?
Loose half the field of view
What does the posterior cerebral artery receive information from?
From the posterior communicating artery and other brain areas
Where is a movement planned?
Prefrontal cortex
Where is a movement sequenced?
Motor cortex
Where is movement initiated?
Basal ganglia
