Tutorial 01 – Part 1 Flashcards
What are the three parts of the brain stem from top to bottom?
Mesencephalon/midbrain
Pons („bridge“)
Medulla (oblongata)
What parts are at/head from the mesencephalon?
- cerebral peduncles on ventral side with substantia nigra
- quadrigeminal plate with superior and inferior colliculi on dorsal side
What is at the base of the pons and what is the pons connected to?
- connected to cerebellum by thick fiber tracts
- at base of pons (ventral aspect), there is the unpaired basilar artery (blood supply to vital brain stem structures)
What does the medulla look like?
Like a thicker continuation of the spinal cord
What does the medulla contain?
Vital centers for circulation and respiration
What decussation is at the medulla?
Decussation of the pyramidal tract
How many cranial nerves are there?
12 on each side -> 24 in total
Cranial nerve 2
Optic nerve
Cranial nerve 3
Oculomotor nerve
Cranial nerve 4
Trochlear nerve
Cranial nerve 1
Olfactory nerve
Cranial nerve 5
Trigeminal nerve
Cranial nerve 6
Abducens nerve
Cranial nerve 7
Facial nerve
Cranial nerve 8
Vestibulocochlear nerve
Cranial nerve 9
Glossopharyngeal nerve
Cranial nerve 10
Vagus nerve
Cranial nerve 11
Spinal accessory nerve
Cranial nerve 12
Hypoglossal nerve
What can small brain stem lesions entail?
Selective dysfunction of specific nerves while sparing others, allowing for clinical localization
Where do cranial nerves get input from?
Input from the head‘s sensory systems and motor control of facial and laryngeal muscles
Where does cranial nerve 1 end in?
Basal forebrain (above brainstem)
Where does cranial nerve 2 send collaterals to?
Cranial nerve 2 (optic nerve) only sends collaterals to brain stem (superior colliculi)
Where does cranial nerve 11 ascend from?
Spinal cord (fake cranial nerve)
What can emotional processing signal presence of?
Emotional processing can signal presence of (or prospect for) reward or punishment and initiate motor programs to pursue or avoid
What does dopamine code for?
Reward prediction
Which circuitry do most drugs of abuse act on?
Elements of limbic circuitry
What can neurotransmitter release trough drugs cause and which neurotransmitters are at play?
Neurotransmitter release (dopamine from VTA, but also noradrenalin, serotonin, and others) through drugs causes unphysiologically elevated levels with psychological alterations
What happens to the receptors when overstimulated?
Internalization of receptors
What response does drug abuse dampen?
Response of the emotional reinforcement circuitry to natural (less potent) awards
Two distinct dopaminergic systems in midbrain
Substantia nigra pars compacta (SNc)
Ventral tegmental area (VTA)
Classifying dopaminergic cells according to gene and protein expression shows…
A variety of subtypes, some of which not strictly adhere to a SNc-VTA separation, show mixed properties, or extended to surrounded nuclei
Typical SNc-type neurons
SOX6, ALDH1A1, PITX3, DCC, GIRK2
Typical VTA-type neurons
CALB1, ALDH1A1, CALB1, PITX3, DCC, GIRK2
Which pathways is VTA origin of?
Mesolimbic pathway (to basal ganglia and amygdala)
Mesocortical pathway (to prefrontal cortex)
What is the main target site for VTA
Ventral striatum (nucleus accumbens and ventral parts of putamen)
Which area are aversion-encoding VTA neurons targeting?
Nucleus accumbens shell region
Which region are VTA neurons activated by motivation and reward are densely innervating?
Nucleus accumbens core region
VTA neurons are implicated in
Incentive-based behavior, motivation, cognition
What neurotransmitters do VTA neurons co-transmit dopamine with?
Glutamate or GABA
What is the origin of the nigrostriatal pathway?
Ventral SCn
What do ventral SNc neurons traget (which part)?
Dorsocaudal part of striatum (caudate nucleus and dorsal putamen)
What lead to deficit in acquiring new motor skills while having no effect on consolidated skills in rodents?
Selective ablation of a ALDH1A1 subtype
What is phasic ventral SNc neuronal firing associated with?
Start-stop signals and acceleration in movement
What are dosal and lateral neurons of the Snc similiar to?
More similar to VTA neurons
What are dorsal and lateral neurons of the SNc implicated in?
Salience and novelty and novelty detection, reward prediction, and contribute to the mesolimbic pathway
Which cells are selectively lost in parkinson disease and what do they contain less of?
Ventral SNc cells – contain less neuromelanin pigment than dorsal cells and are selectively lost in PD
What do neuromelanin sequest from and what does that lead to?
Neuromelanin sequester toxic dopamine metabolites (quinones) and bind iron – leading to less intracellular aggregation of α-synuclein (Lewi bodies) and mitochondrial dysfunction, believed to be the cause of premature cell death
What may intensify vulnerability to Parkinson disease?
Gene variants
What do ventral SNc cells look like (what attributes do they have)?
They are much larger than VTA cells and have extremely branched axonal endings and show high intensity burst firing
What baseline activity do ventral SNc cells have and what does that lead to?
High baseline activity and little capacity to increase mitochondrial respiratory activity in case of stress
What makes ventral SNc cells more vulnerable than other dopaminergic cells?
Multiple hits
