Neurones, synapses and transmitters Flashcards Preview

Foundations of Neuroscience > Neurones, synapses and transmitters > Flashcards

Flashcards in Neurones, synapses and transmitters Deck (43):
1

How many neurons are in the brain?

100 billion

2

How many neurons in the neocortex?

22.8 billion in men, 19.3 billion in women

3

How long are all the nerve fibres in our brain?

150,000-180,000km

4

How many synapses in the cortex

150,000 billion

5

At what rate are neurones lost?

1 a second or 86,000 a day

6

What is the ratio of glia to neurones?

10 glia for each neurone

7

What do glia offer neurones?

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

8

Do glial cells send signals?

Yes

9

What is the central nervous system?

The brain and spinal cord

10

What is the peripheral nervous system made up of?

Sensory nervous system
Motor system
Autonomic nervous system

11

What is the autonomic nervous system made up of?

Sympathetic
Parasympathetic
Enteric

12

What is the opposite of the autonomic nervous system?

The somatic nervous system

13

What is the definition of the peripheral nervous system?

Neurones that extend from the CNS

14

How are neurones specialised for communication?

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

15

How are neurons classified?

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)

16

What is a unipolar neurone?

Single axonal process

17

What is a bipolar neurone?

Two axonal processes

18

What is a multipolar neurone?

Multiple axonal processes

19

What is a pseudo-unipolar neurone?

Single axonal processes, cell body is on a stem

20

What is an electrical synapse?

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

21

How do gap junctions work?

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

22

What does a gap junction do?

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

23

What is a chemical synapse?

A uni-directional transfer of information

24

What is a synaptic cleft?

The gap between the pre and postsynaptic elements

25

What is an efferent neuron?

Information going out

26

What is an afferent neuron?

Information coming in

27

Explain what happens in a chemical synapse

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

How can a signal be terminated in a chemical synapse?

By re-uptake or enzymes in the synaptic cleft

29

Explain how re-uptake occurs

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

30

Explain how enzymatic breakdown occurs

Enzymes present in the synaptic cleft breakdown the neurotransmitter

31

What are the 4 categories of neurotransmitters?

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

32

What are the two classifications of neurotransmitters?

Inhibitory
Excitatory

33

What are the receptors in synapses?

Membrane spanning protein molecules
Specific to a neurotransmitter

34

How do the receptors cause a signal?

Transmitter binding causes structural change, structural change = signal

35

How many receptors does a neurotransmitter have?

Several subtypes

36

How do we classify receptors?

Localisation: post or pre synaptic
What it responds to: autoreceptor, heteroreceptor

37

How do we name multiple receptor sub-types?

Based on most potent, selective agonist
e.g. for glutamatergic receptors we have: AMPA, NMDA, Kainate

38

Name the receptor signalling mechanisms

Ionotropic
Metabotropic

39

How does an ionotropic receptor work?

Ionotropic is receptor operated (ligand gated channels)
Transmitter binds: conformational change, channel opening, ion movement (Na+ in excitatory or Cl- in inhibitory)

40

How quick is an ionotropic receptor?

Fast

41

How does a metabotropic receptor work?

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

42

How quick is a metabotropic receptor?

Slow, but its effect lasts longer

43

What can activated G-proteins do?

Open or close ion channels
Stimulate or inhibit enzymes/ secondary messenger systems