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Neurology > Introduction to Neurones, Excitatory and Inhibitory Neurotransmission in the CNS > Flashcards

Introduction to Neurones, Excitatory and Inhibitory Neurotransmission in the CNS Flashcards

1
Q

What is the role of the dendrite?

A

Receive inputs from other neurones and convey graded electrical signals passively to the soma

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2
Q

What is the role of the cell body (soma)?

A

Synthetic and metabolic centre. Integrates incoming electrical signals that are conducted passively to the axon hillock.

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3
Q

What is the role of the axon hillock and initial segment?

A

Site of initiation of the ‘all or none’ action potential

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4
Q

What is the role of the axon ?

A

Conducts output signals as action potentials to the presynaptic terminal. Mediates the transport of materials between the soma and presynaptic terminal and vice versa

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5
Q

What is the role of the synapse?

A

Point of chemical (usually) communication between neurones (or other cells)

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6
Q

Define unipolar, pseudo unipolar, bipolar and multipolar neurones?

A

Unipolar: one neurite
Pseudounipolar: one neurite that bifurcates ‘splits’
Bipolar: two neurites
Multipolar: three or more neurites

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7
Q

Where would you find a unipolar neurone?

A

Peripheral autonomic neurone

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8
Q

Where would you find a pseudo unipolar neurone?

A

Dorsal root ganglion

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9
Q

Where would you find a bipolar neurone?

A

Retinal bipolar neurone

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10
Q

Where would you find a multipolar neurone?

A

Lower motor neurone (LMN)

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11
Q

What are the four functional regions of a neurone?

A

Input
Integrative
Conductile
Output

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12
Q

What is overshoot?

A

When polarity is reveres to inside positive

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13
Q

Why do passive signals not spread far from their site of origin?

A

Due to current loss across the membrane accompanied by a reduced change in potential

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14
Q

How can the passive current spread and action potential velocity be increased?

A 
Decrease ri (by increasing axon diameter)
Increase rm (adding myelin)
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15
Q

What is saltatory conduction?

A

When action potential jumps from one node of ranvier to the next

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16
Q

What is found in the chemical synapse?

A

A matrix of fibrous extracellular protein

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17
Q

Describe the differentiators of pre-synaptic vs post-synaptic membranes?

A

Presynaptically- active zones around which vesicles cluster

Postsynaptically- the postsynaptic density containing neurotransmitter receptors

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18
Q

What are the three types of synapse?

A

Axodendritic
Axosomatic
Axoaxonic

19
Q

Wha tis the commonest type of synapse?

A

Axodendritic

20
Q

How can synapses be classified functionally?

A

Excitatory or inhibitory

21
Q

What is the most frequent excitatory neurotransmitter?

A

Glutamate

22
Q

What is the most frequent inhibitory neurotransmitter?

A

y-aminobutyric acid (GABA) or glycine

23
Q

Describe the action of glutamate

A

Activates postsynaptic, cation selective, inotropic glutamate receptors generating a local, graded, excitatory (depolarising) response: the excitatory postsynaptic potential

24
Q

Describe the action of GABA or glycine?

A

Activates postsynaptic, anion selective, inotropic, GABAa or glycine receptors, generating a local, graded inhibitory hyperpolarising response: the inhibitory postsynaptic potential

25
Q

Which cation receptors are activated in excitatory synaptic transmission?

A

Na+ receptors

26
Q

Which anion receptors are activated in excitatory inhibitory transmission?

A

Cl-

27
Q

What types of synaptic integration are there?

A

Spatial and temporal integration

28
Q

What is spatial summation?

A

Many inputs converge upon a neurone to determine its output

29
Q

What is temporal summation?

A

A single input may modulate output by variation in action potential frequency of that output

30
Q

What substances are released from synaptic vesicles?

A

Acetylcholine, amino acids and amines

31
Q

What substances are released from secretory vesicles?

A

Peptides

32
Q

What substances can mediate fast neurotransmission?

A

Glutamate, GABA, glycine, acetylcholine, 5-HT can activate inotropic ligand-gated ion channels (LGICs), which mediate fast transmission

33
Q

What substances can mediate slow neurotransmission?

A

All but glycine can activate metabotropic G-protein-coupled receptors. these mediate relatively slow neurotransmission

34
Q

What are the two modes of action of neurotransmitters on ion channels?

A

Direct or indirect

35
Q

Describe direct gating?

A

done by inotropic receptors. The receptor is an integral component of the molecule that forms the channel it controls. Gating of channel is rapid

36
Q

Describe indirect gating?

A

Mediated by activation of metabotropic receptors. receptor and the channel it controls are distinct. Gating of channel is slower (10ms)

37
Q

Cholinergic synaptic transmission in autonomic ganglia display both ____ and ________ transmitter actions

A

Cholinergic synaptic transmission in autonomic ganglia display both direct and indirect transmitter actions

38
Q

In autonomic ganglia fast EPSP is due to activation of ______ (________) ACh receptors. Channels conduct ___ and ___.

A

In autonomic ganglia fast EPSP is due to activation of nicotinic (ionotropic) ACh receptors. Channels conduct Na and K.

39
Q

In autonomic ganglia slow EPSP is follows activation of ______ (________) ACh receptors. ACh closes a K channel (______)

A

In autonomic ganglia slow EPSP is follows activation of muscarinic (G protein-coupled) ACh receptors. ACh closes a K channel (M-type)

40
Q

How does glutamate have an inhibitory effect?

A

Via its response at metabotropic glutamate receptors

41
Q

What are the types of inotropic glutamate receptors?

A

non-NMDA (bind agonists kainate or AMPA- controlling a channel permeable to Na and K)

NMDA controls a channel permeable to Na, Ca, K

42
Q

Non-NMDA inotropic receptors mediate _____ ________ ______ in the CNS whereas NMDA contributes a _____ ______ to the excitatory synaptic potential

A

Non-NMDA inotropic receptors mediate fast excitatory synaptic transmission in the CNS whereas NMDA contributes a slow component to the excitatory synaptic potential

43
Q

What are phencyclidine and ketamine blockers of?

A

Selective blockers of NMDA operated channels

44
Q

What is the role of metabotropic glutamate receptors?

A

To modulate neurotransmission- presynaptic inhibition of Ca2+ channels

Neurology (41 decks)

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