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Foundations of Neuroscience > Neurones, synapses and transmitters > Flashcards

Neurones, synapses and transmitters Flashcards

1
Q

How many neurons are in the brain?

A

100 billion

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2
Q

How many neurons in the neocortex?

A

22.8 billion in men, 19.3 billion in women

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3
Q

How long are all the nerve fibres in our brain?

A

150,000-180,000km

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4
Q

How many synapses in the cortex

A

150,000 billion

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5
Q

At what rate are neurones lost?

A

1 a second or 86,000 a day

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6
Q

What is the ratio of glia to neurones?

A

10 glia for each neurone

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7
Q

What do glia offer neurones?

A

Physical support
Metabolic support
Electrical insulation
Guiding connections (in development)

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8
Q

Do glial cells send signals?

A

Yes

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9
Q

What is the central nervous system?

A

The brain and spinal cord

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10
Q

What is the peripheral nervous system made up of?

A

Sensory nervous system
Motor system
Autonomic nervous system

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11
Q

What is the autonomic nervous system made up of?

A

Sympathetic
Parasympathetic
Enteric

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12
Q

What is the opposite of the autonomic nervous system?

A

The somatic nervous system

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13
Q

What is the definition of the peripheral nervous system?

A

Neurones that extend from the CNS

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14
Q

How are neurones specialised for communication?

A

Dendrites - receive input from other neurones
Axon - impulse conduction
Synaptic bouton - release of neurotransmitter

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15
Q

How are neurons classified?

A

Number of processes coming off the cell body: uni-, bi-, multi-polar
Dendrites: shape, spines
Connections: motor, interneurons
Axon length: golgi type I or II
Neurotransmitter (can’t be seen on microscope)

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16
Q

What is a unipolar neurone?

A

Single axonal process

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17
Q

What is a bipolar neurone?

A

Two axonal processes

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18
Q

What is a multipolar neurone?

A

Multiple axonal processes

19
Q

What is a pseudo-unipolar neurone?

A

Single axonal processes, cell body is on a stem

20
Q

What is an electrical synapse?

A

(also known as gap junction)
Fastest and most primitive means of communication
Bi-directional transfer of information

21
Q

How do gap junctions work?

A

A pore between two cells, it allows ions to move between two cells

22
Q

What does a gap junction do?

A

Allow synchronous activity between neurons
Relatively rare (present in development)
Present in glia-neuron, glia-glia communication (cardiac myocytes)

23
Q

What is a chemical synapse?

A

A uni-directional transfer of information

24
Q

What is a synaptic cleft?

A

The gap between the pre and postsynaptic elements

25
Q

What is an efferent neuron?

A

Information going out

26
Q

What is an afferent neuron?

A

Information coming in

27
Q

Explain what happens in a chemical synapse

A

Action potential invades nerve terminal
Depolarisation triggers Ca2+ channel opening
Ca2+ influx (chemical gradient)
Vesicle containing neurotransmitter moves to cell membrane and fuses
Neurotransmitter leaves cell
Diffuses across the synaptic cleft
Binds to receptor

28
Q

How can a signal be terminated in a chemical synapse?

A

By re-uptake or enzymes in the synaptic cleft

29
Q

Explain how re-uptake occurs

A

Presynaptic neurone takes up neurotransmitter and either repackages it or breaks it down with enzymes

30
Q

Explain how enzymatic breakdown occurs

A

Enzymes present in the synaptic cleft breakdown the neurotransmitter

31
Q

What are the 4 categories of neurotransmitters?

A

Amino acids: glutamate, GABA
Monoamines: noradrenaline, 5-HT
Acetylcholine
Neuroactive peptides

32
Q

What are the two classifications of neurotransmitters?

A

Inhibitory

Excitatory

33
Q

What are the receptors in synapses?

A

Membrane spanning protein molecules

Specific to a neurotransmitter

34
Q

How do the receptors cause a signal?

A

Transmitter binding causes structural change, structural change = signal

35
Q

How many receptors does a neurotransmitter have?

A

Several subtypes

36
Q

How do we classify receptors?

A

Localisation: post or pre synaptic

What it responds to: autoreceptor, heteroreceptor

37
Q

How do we name multiple receptor sub-types?

A

Based on most potent, selective agonist

e.g. for glutamatergic receptors we have: AMPA, NMDA, Kainate

38
Q

Name the receptor signalling mechanisms

A

Ionotropic

Metabotropic

39
Q

How does an ionotropic receptor work?

A

Ionotropic is receptor operated (ligand gated channels)

Transmitter binds: conformational change, channel opening, ion movement (Na+ in excitatory or Cl- in inhibitory)

40
Q

How quick is an ionotropic receptor?

A

Fast

41
Q

How does a metabotropic receptor work?

A 
"G-coupled protein receptors"
Transmitter binds
Conformational change
Activates G-protein
Activates effector systems
Has an indirect effect on excitability
42
Q

How quick is a metabotropic receptor?

A

Slow, but its effect lasts longer

43
Q

What can activated G-proteins do?

A

Open or close ion channels

Stimulate or inhibit enzymes/ secondary messenger systems

Foundations of Neuroscience (15 decks)

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