Introduction to Neurones, Excitatory and Inhibitory Neurotransmission in the CNS

Question 1

What is the role of the dendrite?

Answer 1

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

Question 2

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

Answer 2

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

Question 3

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

Answer 3

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

Question 4

What is the role of the axon ?

Answer 4

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

Question 5

What is the role of the synapse?

Answer 5

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

Question 6

Define unipolar, pseudo unipolar, bipolar and multipolar neurones?

Answer 6

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

Question 7

Where would you find a unipolar neurone?

Answer 7

Peripheral autonomic neurone

Question 8

Where would you find a pseudo unipolar neurone?

Answer 8

Dorsal root ganglion

Question 9

Where would you find a bipolar neurone?

Answer 9

Retinal bipolar neurone

Question 10

Where would you find a multipolar neurone?

Answer 10

Lower motor neurone (LMN)

Question 11

What are the four functional regions of a neurone?

Answer 11

Input
Integrative
Conductile
Output

Question 12

What is overshoot?

Answer 12

When polarity is reveres to inside positive

Question 13

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

Answer 13

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

Question 14

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

Answer 14

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

Question 15

What is saltatory conduction?

Answer 15

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

Question 16

What is found in the chemical synapse?

Answer 16

A matrix of fibrous extracellular protein

Question 17

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

Answer 17

Presynaptically- active zones around which vesicles cluster

Postsynaptically- the postsynaptic density containing neurotransmitter receptors

Question 18

What are the three types of synapse?

Answer 18

Axodendritic
Axosomatic
Axoaxonic

Question 19

Wha tis the commonest type of synapse?

Answer 19

Axodendritic

Question 20

How can synapses be classified functionally?

Answer 20

Excitatory or inhibitory

Question 21

What is the most frequent excitatory neurotransmitter?

Answer 21

Glutamate

Question 22

What is the most frequent inhibitory neurotransmitter?

Answer 22

y-aminobutyric acid (GABA) or glycine

Question 23

Describe the action of glutamate

Answer 23

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

Question 24

Describe the action of GABA or glycine?

Answer 24

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

Question 25

Which cation receptors are activated in excitatory synaptic transmission?

Answer 25

Na+ receptors

Question 26

Which anion receptors are activated in excitatory inhibitory transmission?

Answer 26

Cl-

Question 27

What types of synaptic integration are there?

Answer 27

Spatial and temporal integration

Question 28

What is spatial summation?

Answer 28

Many inputs converge upon a neurone to determine its output

Question 29

What is temporal summation?

Answer 29

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

Question 30

What substances are released from synaptic vesicles?

Answer 30

Acetylcholine, amino acids and amines

Question 31

What substances are released from secretory vesicles?

Answer 31

Peptides

Question 32

What substances can mediate fast neurotransmission?

Answer 32

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

Question 33

What substances can mediate slow neurotransmission?

Answer 33

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

Question 34

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

Answer 34

Direct or indirect

Question 35

Describe direct gating?

Answer 35

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

Question 36

Describe indirect gating?

Answer 36

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

Question 37

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

Answer 37

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

Question 38

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

Answer 38

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

Question 39

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

Answer 39

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

Question 40

How does glutamate have an inhibitory effect?

Answer 40

Via its response at metabotropic glutamate receptors

Question 41

What are the types of inotropic glutamate receptors?

Answer 41

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

Question 42

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

Answer 42

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

Question 43

What are phencyclidine and ketamine blockers of?

Answer 43

Selective blockers of NMDA operated channels

Question 44

What is the role of metabotropic glutamate receptors?

Answer 44

To modulate neurotransmission- presynaptic inhibition of Ca2+ channels