Lecture 4 - Basal Ganglia and Spinal Cord Flashcards
The basal ganglia is divided into two regions: the ________ and the _________ _______
Striatum & Lenticular Nucleus
The striatum of the basal ganglia consists of what two structures?
Caudate nucleus & the putamen
What are the appearances/orientations of the striatum’s structures?
Caudate - situated inferiority to the lateral ventricle
Putamen - inferior & lateral to the caudate
The putamen can be considered to part of both the ______ and the _____ _____
Striatum & lenticular nucleus
The ________ ________ is strictly part of the lenticular nucleus
Globus Pallidus
A main function of the basal ganglia is to facilitate __________ movements and inhibiting ___________/___________ movement
Desired, undesired or competing
The basal ganglia is not an ___________, but rather is a __________
Initiator, facilitator
What does the motor region of the basal ganglia have in common with the primary motor cortex?
It’s got a lil homunculus!
Where Parkinson’s is associated with a difficultly _______ing movements, Huntington’s is associated with a difficulty _______ing _______ movements
Initiating, inhibiting involuntary
A basal ganglia disorder known as _______ is associated with difficulty inhibiting undesired movements (e.g. tics, verbal, thoughts)
Tourette’s
The function of the direct pathway of the cortical-basal-ganglia-thalamic system is to?
Facilitates or encourages movement
The function of the indirect pathway of the cortical-basal-ganglia-thalamic system is to?
Inhibits or suppresses movement
Describe the process of the direct CBGTC system pathway
- The cortex sends signals to the basal ganglia (specifically, a part called the striatum).
- The striatum then sends inhibitory signals to another part of the basal ganglia called the globus pallidus internal (GPi), which normally inhibits the thalamus.
- When the GPi is inhibited, it stops sending its inhibitory signals to the thalamus.
- This allows the thalamus to send more excitatory signals back to the cortex, promoting movement.
Describe the process of the indirect CBGTC system pathway
- The cortex again sends signals to the striatum.
- The striatum sends inhibitory signals to another part of the basal ganglia called the globus pallidus external (GPe).
- When the GPe is inhibited, it reduces its inhibition on a part called the subthalamic nucleus (STN).
- The STN can then send excitatory signals to the GPi, which increases its inhibitory output to the thalamus.
- This leads to less excitation of the cortex, reducing movement.
Describe the effect of Parkinson’s on the CBGTC system
Affects the direct pathway (bias in favour of the indirect pathway, net effect of inhibition)
Voluntary movement becomes harder to initiate rigidity, slowness of movement
Describe the effect of Huntington’s disease on the CBGTC system
Affects the indirect pathway (bias in favour of the direct pathway, net effect of excitation)
movements are harder to inhibit; choreiform movement - involuntary continuous movements especially of the limbs
Where is the substantia Nigra located?
In the midbrain (aka: mesencephalon)
The substantia nigra produces _______
Dopamine
Direct pathway striatal neurons have _____ dopamine receptors, which are _______ by dopamine
D1, excited
Indirect pathway striatal neurons have ______ dopamine receptors, which are ________ by dopamine
D2, inhibited
In someone with Parkinson’s how does the lack of dopamine influence the nigrostriatal pathway
Excitation of the Direct Pathway: With reduced dopamine, the direct pathway is less activated, leading to decreased facilitation of movement. Patients often experience difficulty initiating movement, known as bradykinesia.
Inhibition of the Indirect Pathway: The indirect pathway, which normally helps suppress excessive movement, becomes overactive. This further inhibits movement and can lead to rigidity and tremors.
The subthalamic nucleus is part of the ________encephalon?
Di
The subthalamic nucleus can be seen as an input nucleus to what structure?
Basal ganglia
What structure has been seen to be a target for deep brain stimulation in Parkinson’s disease?
Subthalamic nucleus
What structure has hard-to-define boundaries anatomically, but is thought to be associated with the basal ganglia regardless?
Nucelus accumbens
The nucleus accumbens is located between what two structures?
Caudate and putamen
The nucleus accumbens mediates what type of behaviour? It plays a role in what?
Goal-directed, addicition
What are the 5 major subcortical white matter tracts?
- Superior longitudinal fasciculus
- Arcuate Fasciculus
- Corpus Callosum
- Internal capsule
- Corona Radiata
The superior longitudinal fasciculus has an important function in ___________________
Language processing
Which of the 5 main white matter subcortical tracts is also known as part of the 4 SLF tracts?
Arcuate fasciculus
What does the arcuate fasciculus connect?
Wernicke’s to Broca’s
The ______ connects the two hemispheres
Corpus Callosum
The corpus callosum is complete by age __, and growth continues until the ____ decade of life
4, 3rd
What are the two major pathways of the corpus callosum?
Forceps Major & Forceps Minor
Where is the forceps major pathway located?
Splenium (posterior part of CC)
Where is the forceps minor pathway located?
Genu (anterior part of the corpus callosum)
The splenium of the corpus callosum connects the ______ lobes of both hemispheres
Occipital
The genu of the corpus callosum connects the ______ lobes of both hemispheres
Frontal
The _______ connects the cerebral cortex with the subcortical structures, brainstem & spinal cord
Internal Capsule
The Internal Capsule separates the _______ from the lenticular nuclei
Caudate
T/F The internal capsule is unidirectional
F. Bidirectional - afferent and efferent
The corona radiata can be described as fibres from the _______ radiating to various parts of the _______ and ________
Internal capsule, cerebral cortex, basal ganglia
A nickname for the cerebellum is the?
Little brain
T/F The cerebellum has its own gyri, sulci, and subcortical structures
T
What separates the two cerebellar hemispheres
Vermis
The cerebellum is part of the ________encephalon
Met
The cerebellum is considered to be the largest _____ structure in the CNS
motor
Which has more neurons: the cerebellum or the cortex?
Cerebellum
What are the 3 nuclei of the cerebellum?
FID!
Fastigial
Interpositus
Dentate
The _____ cerebellar peduncle is the most medial, while the ______ cerebellar peduncle is the most lateral
Fastigial, Dentate
Lesions in each of the three cerebellar nuclei could result in?
F - Loss of balance/positional sense, involuntary breathing/eye movements
I - Tremor
D - Ataxia
The input and output to/from the cerebellum is controlled by the cerebellar _______
Peduncles
Describe what each of the three cerebellar peduncles are responsible for
Superior (mostly output from Cb)
Middle (mostly input to Cb via pons – movement and cognition)
Inferior (mostly input to Cb via pons - vestibular)
What are the three main principles to remember when thinking of the cerebellar peduncles?
- Receives input from specific CNS regions and sends information back to the same regions
- Input and output preserve somatotopy of the cerebral cortex and other areas
- Unlike the cerebral cortex, the cerebellum receives input from, and controls output to, the ipsilateral side of the body
Therefore, damage to the cerebellum results in deficits to the ipsilateral side of the body
Describe the 3 output zones of the cerebellar peduncles
Lateral zone: dentate nucleus - thalamus – cortex
Intermediate zone: interpositus nucleus – red nucleus (midbrain – important for motor function) as well as thalamus
Medial zone: fastigial nucleus – vestibular spinal cord region as well as thalamus
Describe the ventral view of the brainstem (midbrain)?
Large lateral columns called cerebral peduncles (descending white matter)
Continuation of the corticospinal and corticobulbar tracts
The cerebral peduncles go up to the _______ and down to the _______
Internal Capsule, Pyramids
Describe the dorsal view of the brain stem (midbrain)?
Superior and inferior colliculi
The superior colliculi integrates what type of info for orientation of what parts of our body? What reflex is it responsible for?
Visual, auditory, and somatosensory
Eyes & head
Startle reflex
Inferior Colliculi is a relay station of ______ stimuli from the ______ to the _______
Auditory, cochlea, cortex
When thinking of the brainstem (midbrain) from a rostral POV, it merges with the ______encephalon
Die
Describe what can be found inside the brainstem (midbrain)?
Substantia Nigra
Cerebral aqueduct surrounded by the periaqueductal gray matter
What is the periaqueductal gray involved with?
Involuntary vocalization and pain sensation
Describe the dorsal POV of the Pons
Cerebellar peduncles & the pineal gland
What can be found inbetween the cerebellar peduncles?
The origin of the 4th ventricle, this widens into the medulla portion of the ventricle
What does the pineal gland produce?
Melatonin
Describe the lateral POV of the pons?
Large root of CN V - trigeminal
What can be found inside the pons?
Lateral & medial lemniscus
What is a lemniscus?
A bundle of secondary sensory fibers in the brainstem
The lateral lemniscus is part of the ______ pathway. It connects to the _______
Auditory, inferior colliculus
The medial lemniscus is associated with ____, ____ and _____. It connects to the ____ and _____
touch, vibration & proprioception. Thalamus, cortex
Describe the ventral aspect of the medulla oblongata
Pyramids! - prominent bundles of white matter
T/F: 85-90% of the fibres of the pyramids cross the midline
T
What can be found inside the medulla oblongata?
Cranial nerve nuclei (many of them involved with speech/swallowing (IX, X, XI, XII)
Describe the dorsal aspect of the medulla oblongata
Fourth ventricle
Fasciculus gracilis
Fasciculus cuneatus
Olive
Central pattern generator networks
The Fasciculus gracilis is associated with sensation from what body part?
Legs
The Fasciculus cuneatus is associated with sensation from what body part?
Arms
The Olive has connections to the what structure? It is responsible for integration of what type of info?
Cerebellum, motor/sensory, sound localization & analysis
The central pattern generator plays a role in what actions?
Chewing, swallowing, and respiration
Where does the spinal cord end?
Medullaris
White matter of the spinal cord is on the _____, gray matter is _______
Periphery, centrally
Describe the function of the dorsal horn & ventral horn gray matter
Dorsal horn gray matter - cell bodies that receive afferent input
Ventral horn gray matter - cell bodies of the lower motor neurons
Describe the white matter of the spinal cord (dorsally vs ventrally)
Dorsally - dorsal columns (afferent)
Ventrally - corticospinal tract (efferent)
What type of cell bodies are in the spinal cord? What about outside the spinal cord in a spinal ganglion?
1) motor
2) sensory
What happens to voluntary movements with damage to upper motor neurons? What pyramidal tract is this associated with?
Spasticity, stronger reflexes, muscle weakness
The pyramidal tract
What happens with posture & tone after damage to the upper motor neurons? What pyramidal tract is this associated with?
weakness, reduced reflexes, decreased muscle tone
The extrapyramidal tract
Damage to lower motor neurons results in:
(e.g., progressive muscular atrophy, poliomyelitis):
Loss of muscle innervation: diminished reflexes, muscle wasting, weakness/paresis
The cortico-spinal (pyramidal) tract controls what?
Primary voluntary motor activity
What is the origin of the cortico-spinal tract?
Primary motor and somatosensory cortex
Describe the path of the cortico-spinal tract
Upper motor neurons are in the cortex -> project through the corona radiata to the internal capsule -> cerebral penduncles -> pyramids of the medulla -> travel to spinal cord to synapse on the lower motor neurons
Most fibres of the corticospinal tract cross - they continue as what? They control what?
Lateral corticospinal tract - arms and legs
The fibres of the corticospinal tract that do not cross over form what? They control what?
Anterior corticospinal tract - head & trunk
What is a dermatome?
area of the body innervated by the neurons in single dorsal root
What is a myotome?
muscles or parts of the muscle innervated by a single ventral root
What are the significances of sciatica, chickenpox, and shingles in relation to the spinal cord?
Some health conditions that manifest themselves along dermatomes. May feel excessive pain in specific “bands” of the body because they are attacking specific dermatomes
