Basal Ganglia Flashcards
basal ganglia definition
Collection of neuronal nuclei that connect the cerebral cortex to the thalamus and brain stem
What is the basal ganglia made up of
caudate nucleus
putamen
globus pallidus
substantia nigra
subthalamic nucleus
role of the basal ganglia
motor control
cognitive function
emotion
motivation
learning
receive information from the
cerebral cortex
sends information to the
thalamus and brain stem
Globus pallidus
Main output centre of the basal ganglia
Prevents unwanted movements - inhibitory on the thalamus
how to promote smooth movement
balance direct and indirect pathways
Glia cells = Satellite cell role
peripheral NS
surround neutron cell bodies in ganglia
regulate O2, CO2, nutrient and neurotransmitter levels around neuron’s in ganglia
Glia cells = Schwann cells
peripheral NS
surround axons
responsible for myelination of peripheral axons
participate in repair process after injury
Glia cells = Oligodendrocytes
CNS
myeline axons
structural framework
Glia cells - astrocytes
CNS
maintain BBB
structural support
regulate ion nutrient and dissolves gas conc
absorb and recycle neurotransmitters
form scar tissue after injury
Glia cells = Microglia
CNS
remove cell debris, waste and pathogens
phagocytosis
Serotonin - output from what cell and its function?
Raphe nucleus
Arousal, sensory processing, mood, emotion
Dopamine - output from what cell and its function?
compact part of substantial nigra
ventral tegmental nucleus
Motivation, motor control, memory and learning
Noradrenaline - output from what cell and its function?
Ceruleus nucleus
arousal, attention, memory, pain, stress
direct pathway
silences the neurons in globus pallidus - this frees the thalamusfrom the inhibitory effects of the global pallidus= allows moving quicker
indirect pathway
Subthalamic nucleus = leads to increased suppression of unwanted movements
how is serotonin synthesised
tryptophan ->(TPH) -> 5-Hydroxytryptophan -> (AADC) -> 5HT (serotonin)
where are the enzyme responsible for serotonin synthesis located
specific neurons and brainstem
what does tryptophan cross BBB with and how
using a common transporter with other LNAAs(large neutral amino acids = valine, leucine, isoleucine, phenylalanine, tyrosine, methionine)
effects of high levels of LNAAs
high protein diet, tryptophan is less likely to be taken up by the brain and is the rate limiting step for serotonin synthesis in the brain
are males or female more capable of producing serotonin
males - 52% more capable of producing serotonin
Tryptophan deficiency = precursor of serotonin = 4th fold decrease in brain serotonin synthesis in females compared to males
seronin transporter
vesicular monoamine transporter
how is serotonin transported to post synapse
- packed into vesicles
- transported by exocytosis
how does serotonin go back to pre synapse
via serotonin transporter
steps at post synaptase = serotonin
· Stop continuous stimulation of certain logic receptors located at the postsynaptic membrane
· Monoamide oxidase = degrades serotonin = 5-hydroxy indole acetic acid- number of certain logic receptors found in the brain (7 families, 14 receptors)
how are serotonin levels controlled
· If level of serotonin is high at synaptic cleft = signal the property when a receptor presynaptic cell and this will signal to the rest of the cell that deserted and production should slow down = less serotonin at the end will be produced
· When receptor is not simulated = signals to the cells that there is not enough serotonin produced = accelerate serotonin acceleration
what two groups are Serotoninergic monoaminergic brainstem nuclei concentrated in
- The raphe magus, raphe obscurus and raphe pallidus= projects from the medulla to the spinal cord and modulates afferent pain signals, thermoregulation, cardiovascular control and breathing.
- The rostral median and dorsal raphe that project from the pons/midbrain to the forebrain and all cortical areas
what do serotoninergic cells regulate
arousal, attention, mood, cognition
what are the families of 5HT receptors are there GPCRs
· Seven families and 15 subtypes of 5HTR (5HTR1-5HTR7)
· All of them are G-protein-coupled receptors, except for 5HT3, which is a ion channel.
step from tryptophan to 5-HTP called
tryptophan hydroxylation
step from 5-HTP to 5HT called
5HTP decarboxylation
dopamine synthesis
phenylalanine
(phenylalanine hydroxylate)
tyrosine
(tyrosine hydroxylate)
L-DOPA
(aromatic L amino acid decarvoxylase)
dopamine
dopamine to noradrenaline
dopamine
(dopamine B hydroxylate)
noradrenaline
where is dopamine synthesised
CNS
chromium affinity cells in adrenal medulla
how is dopamine/ noradrenaline transported
Dopamine (precursor of noradrenaline)
Dopamine is transported into synaptic vesicle by vesicular monoamine transporters (vMATs)
vMAT1 expressed
chromium affinity cell sof the adrenal gland
vMAT2 expressed
neurons
role of vMATs
accumulate monoamines in vesicles by exchange transport with H+
role of NET and NAT
· After release = reuptake by norepinephrine transporter (NET) or noradrenaline transporter (NAT)
· NET is Na+/K+-ATPase-dependent and transports noradrenaline into the cell by Na+/Cl- cotransport.
NETs are also regulated by phosphorylation
two place dopaminergic neurons are concentrated in midbrain
- The substantia nigra pars compacta that projects to the dorsal striatum via the nigrostraiatal pathway - part of basal ganglia loop and involved in motor control
- Ventral tegmental area (VTA) that projects the prefrontal cortex and basal forebrain via mescorticolimbic pathway.
pathway of D1 and D5 (D1 like) receptors
activate their target cells = increasing levels of cyclic adenosine monophosphate (cAMP) = targets of the mesocorticolimbic pathway
pathway of D2,3,4 (D2 like) receptors
inhibit their target cells = reducing the levels of cAMP = dominate the nigrostriatal pathway
where is dopamine converted to noradrenaline
By dopamine-b-hydroxylates in noradrenergic cells
concentrated in the pigment Pontine nucleus locus coerleus (LC))
what does the locus coerleus regulate
working memory, attention, perception, motivation, pain and autonomic reflexes
what receptors does noradrenaline act through
alpha1, alpha2, beta adrenoreceptors
alpha 1 and beta adrenoreceptors
postsynaptic sites = excitatory action
alpha 2 adrenoreceptors
distributed pre and post synaptically and they commonly exert inhibitory effects
how is noradrenaline transferred to adrenaline
by phenylethanolamine-N-methyltransferase
where is adrenaline produced
chromaffin cells in the medualla for the adrenal gland and a small number of medullary neurons
role of adrenaline
Adrenaline is mainly released into the circulation and acts as a hormones on distant targets - regulates - fight or flight response = increases blood flow to muscles - output of the heart - pupil dilation response - blood sugar level
Binds to alpha-AR and beta-AR
monoaminergic cells
CNS = attention, mood, cognition, memory
monoamines
essential components of ascending arousal system and modulate level of the behavioural arousal
corticospinal tract (pyramidal tract)
bundle of axons from the motor cortex of the cerebral cortex through the spinal cord to the skeletal muscle
motor neuron axons
what tracks is the corticospinal tract divided into
lateral cortical tract (pyramidal lateral tract)
anterior cortical tract (pyramidal anterior tract)
where does cerebral cortex flow through
cerebral cortex -> brain stem (pyramidal tracts)
Doesn’t pass through the pyramids of the medulla oblongata
Transmits signals from the cerebrum to the motor nuclei (nerve nuclei containing cell bodies of motor neurons) of the cranial nerves in the brainstem (NOT the spinal cord)
upper motor neurons
cell bodies of motoneurons in corticospinal tract are in the cortical motor cortex
axons of these neurons travel through the brainstem to the Spinal cord (upper motor neuron)
lower motor neurons
In the anterior horn of spinal cord
axons of the higher motor neurons connects to lower neurons (via interneurons and neuron synapses directly with lower motor neurons)
brainstem
cell bodies of subordinate motor neurons = in the motor nuclei of cranial nerves
cerebrum furrows
sulci
lateral sulcus (sulcus sylvianus) and the central sulcus (sulcus centralis) are particularly conspicuous and are important as a guide to the anatomical divisions.
cerebrum bulges
gyri
where is primary motor cortex
- above lateral sulcus and anterior to central sulcus between frontal and parietal
role of primary motor cortex
voluntary movements of specific body parts associated with the central gyrus.
frontal lobe role
voluntary movement, expressive language and for managing higher level executive functions.
parietal lobe location
Above the lateral sulcus, posterior to the central sulcus and anterior to the parieto-occipital sulcus to the angular gyrus
parietal lobe role
ntegrates sensory information from different sensory modalities.
· particularly responsible for spatial perception and instructional decisions.
parietal lobe role
ntegrates sensory information from different sensory modalities.
· particularly responsible for spatial perception and instructional decisions.
what does parietal lobe consist of
parietal lobes comprise the somatosensory cortex and the dorsal cortical visual pathways of the visual system.
temporal lobe location
Located inferior to the external lateral sulcus and anterior to the angular gyrus, the temporal lobe is one of the cerebral lobes
temporal lobe role
language, memory and hearing
auditory processing
occipital lobe role
language, memory and hearing.
occipital lobe role
visual information
visuospatial formation, colour discrimination and motion perception
proprioception vs spinothalamic tracts
proprioception (position and vibration) and the spinothalamic tract = warmth and pain ( temperature and pain)
roles of basal ganglia in movement
inhibits muscle tone throughout the body
supports useful activtity and suppress unwanted or useless patterns of activity
monitors and coordinates slow, sustained contractions = posture and support
striatum
caudate, putamen, and ventral striatum
Stratum and caudate nucleus = originally one structure (e.g in rodents) but seperated in evolution
The striatum is the input to the cerebral cortex and thalamus
subthalamic nucleus
inputs from cerebral Cortex
globus pallidus
· internal and external segment
· internal GP = considered to be a single structure with the substantia nigra reticularis and is an output to the thalamus
Outer GP = indirect pathway passes = nucleus accumbens is a combination of the putamen (striatum) and globus pallidus
substantia nigra
dense part and reticular part (midbrain)
embryologically and physiologically part of basal ganglia
Reticular area of substanitia nigra - output area
Dense substantia nigra contains many dopaminergic neurons and is a modulatory circuit element projecting to the striatum
explain the steps of the direct pathway
Neocortex [glutamate] → striatum [GABA] → globus pallidus internus/nigrostriatal area [GABA] → motor thalamic nucleus [glutamate] → motor neocortical area
direct pathway causes motor activity to be
increased
GABAergic neurons
inferior segment of the GP and SN
exit of the basal ganglia
fire at high fire and strongly inhibit the activity of neurons in the thalamus
steps of the indirect pathway
neocortex [glutamate] → striatum [GABA] → extrastriate pallidum [GABA] → subthalamic nucleus [glutamate] → intrastriate pallidum/nigrostriate [GABA] → motor thalamic nucleus [glutamate] → motor neocortical area
indirect pathway causes motor inhibition to be
reduced
what produced dopamine
substantia nigra
dopamine effect on direct pathway and indirect pathway
excited direct pathway via d1
inhibits indirect pathway via d2
where are cholinergic interneurons
in striatum
effect of cholinergic interneurons on direct and indirect pathways
inhibits striatal cells of direct
excite striatal cells of indirect
cholinergic neurons effect on striatum, nucleus accumbent, SN
motor function and motivation
cholinergic neurons effect on thalamus
arousal
Loss of dopaminergic influence results in (PARKINSONS)
- less excitation of direct pathway (normally turns up motor activity)
- less inhibition of indirect pathway ( normally turns down motor activity)
Parkinson’s disease
why do Parkinson’s patients have smaller substantial nigra
Plasticity of substantia nigra very strong - neurochemical level - slows down dopamine transport systems aallowing dopamine to remain longer at chemcial synapses in the striatum
Loss of GABAergic cells in striatum that project to the laterl palladium (HUNTINGTONS DISEASE) results in
indirect pathway (normally turns down motor activity) inhibited
striatal cholinergic cells = die - normally turn down motor activity
