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Sem3 > Case 7 > Flashcards

Case 7 Flashcards

1
Q

What is the main efferent neurotransmitter of PNS?

A

Acetylcholine

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2
Q

What is the acetylcholine precursor?

A

Acetyl coenzyme A and choline

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3
Q

What is the catalyst in the synthesis of Acetylcholine?

A

Choline acetyltransferase (CAT)

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4
Q

What is the enzyme that hydrolyses Acetylcholine?

A

Acetylcholinesterase (AChE)

Broken down into acetate and choline (choline is reabsorbed via sodium-choline transporter)

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5
Q

What is Nicotinic ACh receptors?

A

Non-selective cation channels that generate excitatory postsynpatic responses

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6
Q

Where are nAChR found?

A

Ganglion between pre and postganglionic nerve

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7
Q

What are Muscatinic ACh receptors?

A

Metabotropic and mediate most of the effects of ACh in the brain

They are highly expressed in the striatum

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8
Q

What is the main excitatory transmitter in the CNS?

A

Glutamate

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9
Q

What are the precursors of Glutamate?

A

Glucose or glutamine

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10
Q

What releases glutamine?

A

Glial cells

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11
Q

What is the enzyme that converts glutamine into glutamate?

A

Mitochondrial enzyme glutaminase

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12
Q

What enzyme converts glutamate into glutamine in glial cells?

A

Glutamine synthetase

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13
Q

What is the ionotropic receptors of Glutamate?

A

NMDA, AMPA, and Kainate

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14
Q

Which Glutamate receptor can increase calcium concentration in postsynaptic neurons?

A

NMDA - leading to activation of intracellulaire signalling cascades

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15
Q

Which cation blocks the NMDA pote during hyperpolarisation?

A

Magnesium

Depolarisation pushes it out to allow flow of cations (requires glycine)

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16
Q

What is the difference between NMDA and AMPA synaptic currents?

A

NMDA are slower and longer-lasting than those produced by AMPA/Kainate receptors

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17
Q

What do metabotropic glutamate receptors do?

A

They cause an inhibition of postsynaptic calcium and sodium channels decreasing the excitability of postsynaptic cells

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18
Q

What is the major inhibiting neurotransmitter in CNS?

A

GABA or Glycine

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19
Q

What forms GABA?

A

Glutamate via reaction catalysed by glutamic acid decarboxylase (GAD) - found one GABAergic neurons

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20
Q

Where is GABA abundant?

A

Nigrostriatal system

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21
Q

What converts GABA to succinate?

A

GABA transaminase

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22
Q

What are the two groups of GABA postsynaptic receptors?

A

Ionotropic - GABA(A) and GABA(C) > causes hyperpolarisation via increase of Chloride ion permeability

Metabotropic - GABA(B) > cause hyperpolarisation via activation of Potassium channels and inhibition of calcium channels

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23
Q

Where is glycine abundant?

A

Spinal cord grey matter of ventral horn

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24
Q

What produces Dopamine?

A

L-DOPa via reaction catalysed by DOPA decarboxylase

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25
Q

What is a DAT?

A

Sodium dependent Dopamine transporter in glial cell membranes used to re-uptake dopamine from synaptic cleft

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26
Q

Which enzymes are involved in dopamine breakdown?

A

Monoamine oxidase (MAO)

Catechism-O-methyltransferase (COMT)

27
Q

How does cocaine produce its psychotropic effects?

A

Blocking DAT hence increasing synaptic cleft concentration of Dopamine

28
Q

Where does the dopaminergic system arise?

A

Midbrain

29
Q

What makes the substantia Nigra appear dark?

A

Neuromelanin in dopaminergic receptors

30
Q

Where does the nigrostriatal pathway mainly arise from?

A

substantia nigra pars compacta and projects to striatum (caudate and putamen)

This is the primary input into basal ganglia system

31
Q

What does dysfunction of nigrostriatal pathway cause?

A

Movement disorders such as Parkinson’s Disease

32
Q

Which dopamine pathways arise from ventral tegmental area?

A

Mesolimbic - VTA to limbic structures (pathway for reward and addiction)

Mesocortical - VTA to prefrontal cortex (pathway for working memory and attentional aspects of motor imitation)

33
Q

What are dopamine receptors?

A

G-protein coupled receptors

Subtypes activate or inhibit adenylyl cyclase

Dopamine also acts on adrenoreceptors

34
Q

How is movement modulated?

A

By a group of nuclei deep in the cerebral hemispheres known as Basal ganglia

35
Q

What does basal ganglia do?

A

Facilitate initiation of motor program that express movement and suppress competing motor program that interferes with expression of sensory-drive or goal directed behaviour

36
Q

What are the nucleus of the basal ganglia called?

A

Caudate and Putamen (Corpus Striatum)

Globus pallidus

37
Q

How does the basal ganglia influence movement?

A

It regulates the activity of the UMN

38
Q

What type of movement does the loop formed by basal ganglia, substantia nigra and subthalamic nucleus cause?

A

Voluntary

Problem in any part of the loop causes problems with smoothly switching between commands that start movements and those that end movements

39
Q

What are the largest input into basal ganglia?

A

Corticostriatal pathway - cortex to corpus striatum via internal capsule

40
Q

Which cortical areas do not project to corpus striatum?

A

primary visual and auditory cortices

41
Q

What is the destination of input from cortex?

A

Medium spiny neurons in corpus striatum

Most input is excitatory

42
Q

What is the main output of basal ganglia?

A

Globus pallidus and Substantia Nigra pars Reticulata

43
Q

Where do axons from the basal ganglia go?

A

Globus pallidus and substantia nigra reticulata

44
Q

What are the circuits formed in basal ganglia?

A

Cerebral cortex to medium spiny cells (Glu)

Interneurones to medium spiny cells (small IN are GABA; big IN are ACh)

Substantia nigra par compacta to medium spiny cells (dopamine)

45
Q

Why are medium spiny neurones usually silent?

A

Because they require excitatory inputs simultaneously from cortical and nigral neurones

46
Q

What does dopamine and glutamate do in the basal ganglia circuits?

A

Modulate synaptic strength

47
Q

What is the purpose of direct pathway of voluntary movement?

A

Stimulate muscle movement

48
Q

What is the direct pathway voluntary control of movement?

A

Primary motor cortex to putamen (Glu) > increase putamen to GPi (GABA) > decrease GPi to thalamus (GABA) > increase thalamus to primary motor cortex (Glu)

49
Q

What is the function of the indirect pathway for voluntary motor control?

A

Inhibits muscle movement

50
Q

What is the indirect pathway voluntary control of movement?

A

Primary motor cortex to putamen (Glu) > increase putamen to GPe (GABA) > decrease GPe to Subthalamic nucleus (GABA) and GPi (GABA) > increase subthalamic to GPi (Glu) > increase GPi to Thalamus (GABA) > decrease thalamus to primary motor cortex (Glu)

51
Q

How is muscle movement stimulated?

A

Primary motor cortex signals substantia nigra compacta which then simultaneously stimulates direct pathway and inhibits indirect pathway for muscle movement

52
Q

What normally happens at dopamine receptors?

A

D1R - activation causes increase in dynorphin and stimulates direct pathway [excites Adenylyl cyclase to form cAMP from ATP]

D2R - activation decreases enkephalin, causing inhibition of indirect pathway [inhibits adenylyl cyclase to prevent cAMP from ATP]

53
Q

How is eye movement controlled by basal ganglia?

A

Corpus striatum to substantia nigra pars reticulata to UMN in superior colliculus

54
Q

What is the ansa lenticularis and lenticular fasciculus?

A

Carries fibres from Globus Pallidus to thalamus

Join to form thalamic fasciculus

55
Q

What is the subthalamic fasciculus?

A

Carries fibres of indirect pathway from GPe to Subthalamic nucleus and Subthalamic nucleus to GPi

56
Q

What are the three lobes of the cerebellum?

A

Anterior, posterior and flocculonodular

57
Q

What are the three main tracts of the cerebellum?

A
  • Cerebrocerebellum - high skilled movement for extremities
  • Vestibulicerebellum - input from vestibular nuclei to regulate movement underlying posture and equilibrium
  • Spinocerebellum - input directly from spinal cord; lateral part = movement of distal muscles and vermis = movement of proximal muscles and eye movements (in response to vestibular input)
58
Q

What carries output from cerebellum?

A

Superior cerebellar peduncle (decussates In midbrain at the level of inferior colliculi)

59
Q

What does the middle and inferior cerebellar peduncle carry?

A

Inputs to cerebellar

60
Q

What are the deep cerebellar nuclei?

A

Dentate- input from lateral cerebellar hemispheres

Interposed - (emboliform and globose nucleus) Input from the intermediate cerebellar hemisphere

Fastigial - input from vermis and flocculus (fibres leaving inferior vermis and flocculi project to vestibular nuclei)

61
Q

What is the largest input to cerebellum?

A

Primary motor and premotor cortices (go to cerebrocerebellum)

62
Q

What are other inputs to cerebellum?

A

From cerebrum:
• Primary and secondary somatic sensory cortices, secondary visual regions

From periphery:
• CN VIII vestibular axons and axons from vestibular nuclei in medulla to vedtibulocerebellum

• dorsal nucleus of Clarke in spinal cord to spinocerebellum

Others:
• inferior olive and locus cerulean in brain stem (for learning and memory functions)

63
Q

Where do the cortical pathways relay before entering cerebellum?

A

Pontine nuclei >enter contralateral cerebellum hemisphere via middle peduncle

64
Q

What is the nucleus of Clarke?

A

Group of relay neurons innervated by proprioceptive scones from periphery

Sem3 (10 decks)

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