Lecture 3- Neurotransmission Flashcards
1
Q
NT 1
A
Within a neuron
2
Q
NT 2
A
Between neurons
3
Q
Dendrites
A
Recipient of information from other neurons, large receptive field
4
Q
Soma
A
Contains the tools that control processing in the cell and integrates info
5
Q
Axon
A
- Uses action potential to pass info from the soma to the terminal boutons
- Can contact multiple neurons
6
Q
Terminal boutons
A
- Found at the end of the axon
- Communication point with other neuron
7
Q
Neural membrane
A
- Boundary of soma, dendrites, axon and terminal boutons
- Lipid bilayer
- Separates extracellular and intracellular
8
Q
1930s Hodgkin and Huxley
A
- Used squids giant axon in sea water
- Measured electrical voltage
- Placed microelectrodes inside and outside membrane
9
Q
Membrane potential
A
Electrical charge across the membrane
10
Q
At rest difference between inside and outside of neurons is
A
Approximately 65-70 mV (millivolts)
11
Q
At rest inside of neurons is more
A
Negatively charged than the outside
12
Q
What causes there to be a membrane potential
A
Force of diffusion
Force of electrostatic pressure (particles moving to opposite charge Na+ -> negatively charged)
13
Q
Equilibrium potential
A
Outward movement = inward movement
14
Q
Resting membrane potential results from
A
The separation of charge across the membrane
15
Q
What are Organic anions
A
- Big and heavy
- Influence the neuron charge
16
Q
At rest which channels are more open
A
K+ channels open more than Na+
17
Q
At rest high concentration of
A
- Na+ outside neuron
- High concentration of K+ inside neuron
18
Q
What’s the Nernst Equation
A
The equilibrium potential can be calculated for any ion using this
19
Q
If you have a bigger ion concentration outside than inside what is the equilibrium potential
A
Positive equilibrium potential
20
Q
Sodium-Potassium pump maintains
A
Ionic concentration gradients across the membrane and therefore membrane potential
21
Q
If potassium was the only ion moving the potential would stabilise at
A
-90 mV
However, positively charged sodium ions leak into the neuron, raising it to -70
22
Q
Where is action potential generated
A
Axon hillock
23
Q
Action potentials are generated by
A
- The summation of converging inputs from the dendrites or
- Electrical stimulation (experimentally)
24
Q
Hyperpolerisation is a membrane potential that’s
A
More negative than resting membrane potential (RMP)
25
Ways of achieving hyperpolarisation
- Injection of small negative current
- Positive ions move out
- Negative ions move in
26
Depolarisation is membrane potential that’s
More positive than Resting membrane potential (RMP)
27
Ways of achieving depolarisation
- Injection of small positive current
| - Positive ions move in
28
What is conductance
Small depolarisation to a neuron
29
Conductance affects what part of the axon the most
Positivity is bigger towards the injection site than away
30
What is decremental conductance
As you go along the axon conductance is decaying
31
What is an action potential in relation to depolarisation
Increase the size of the stimulation and therefore the degree of depolarisation
32
What is the threshold of an action potential
-50mV
33
What does the term voltage gated channels mean
Opened when the membrane becomes depolarised
34
Voltage clamp experiments use injecting a current into the axon to create
A steady membrane potential
35
Voltage clamp experiments record
The membrane current
36
What does Sodium look like with Voltage clamp experiments
Fast movement of ions into the neuron through the Na+ channels, looks like a spike then flatline
37
What does a Potassium current look like with Voltage clamp experiments
Movement of ions out of the neuron through the K+ channels, Curve up
38
What is conductance rate
The rate of ion travel through channel
39
What is a refractory period
Voltage gated channels are no longer working
40
Which gate is in use in rest of Voltage gated channels
Activation gate
41
Which gate is in use in open Voltage gated channels
Neither, gates open
42
Which gate is in use when refractory Voltage gated channels
Inactivation gate
43
What is enough depolarisation to open K+ channels
Close to -10,-20
44
At resting membrane potential most channels are
Closed
45
Small depolarisation opens
A few Na+ channels leading to further depolarisation
46
If stimulation (action potential) is large enough what channels will open
Na+ channels, more Na+ moves into the neuron
47
As the neuron continues to depolarise, what channels start to open
Some K+ channels, allowing K+ to leave the neuron
48
After the peak of the action potential what begins to happen to channels
- Na+ channels become deactivated
| - Remaining K+ channels open and K+ continues to leave the neuron
49
K+ leaving the neuron through diffusion is
Repolarisation
50
What is hyperpolarisation
- K+ channels begin to close
- Na+ channels return to closed state (resting)
- Membrane potential drops below RMP
51
What happens after hyperpolarisation
K+ channels close and external K+ is diffused away
| Membrane returns to RMP due to ATP pumps
52
Action potential is how big along the axon
The same size along the axon
53
What is bioelectric medicine
Application of understanding about neuronal circuits and electrical impulses
54
What are oligodendrocytes
- Asymmetrical
| - Forms myelin around axons in brain and spinal cord
55
What are Schwann cells
- Asymmetrical
| - Wraps around peripheral nerves to form myelin
56
At myelinated axons where can axons only occur
Nodes of ranvier as that’s the only time Na+ and K+ can release
57
Advantages of myelinated axons
-Less action potentials needed
58
What is multiple sclerosis
- Damage to myelin sheath
| - Loss of sensitivity, muscle weakness, difficulty with coordination and balance
59
What’s tetrodotoxin
- From puffer fish
- Blocks voltage gated Na+ channels
- No cure
- Paralysis, conscious while you die
60
What is alpha-dendrotoxin
- From green mamba
- Blocks voltage gated K+ channels
- Leads to convulsions
61
What effects do cocaine, benzocaine and lidocaine have
- Voltage gated Na+ channel blockers
| - Used as anaesthetics
62
What are the types of synapses
- Electrical
| - Chemical
63
Electrical synapse
- Very rare in adult mammalian neuron’s
- Junction between neurons is very small
- Ions can move freely resulting in fast electrical transmission
64
Chemical synapses
- Common in adult mammalian neurons
| - Neurotransmitters are released from presynaptic to post
65
What are the three types of synapses
- Axodendritic, axon to dendrite (most)
- Axosomatic, axon to soma
- Axoaxonic, axon to axon
66
Why does it matter where the location of the synapse is
- The closer the synapse is to the soma the greater it’s influence on production of an action potential
- Due to decremental decay
67
When action potential gets to the synapse depolarisation
Opens voltage gated calcium
68
Criteria for neurotransmitters
- Chemical synthesised presynaptically
- Electrical stimulation leads to the release of the chemical
- Chemical produces physiological effect
- Terminal activity
69
What’s Dales Law
If a Neurotransmitters released by one of a neurons synaptic endings, the same chemical is released at all synaptic endings of the neuron
70
Calcium influx allows for
Vesicles to fuse with the synaptic membrane
71
What do metabotropic receptors do
- Activate an internal second messenger system that goes on to affect the functioning of postsynaptic cells
- Amplified response
72
What do ionotropic receptors do
Open an ionic channel (typically)
73
What is an excitatory transmission
- Movement of positive ions into the neuron
- Depolarisation
- Excitatory post synaptic potential
74
Inhibitory fast transmission
- Movement of negative ions into the neuron
- Hyperpolarisation
- Inhibitory post synaptic potential
75
What is the metabotropic receptor
- G protein coupled receptors
| - GPCR
76
What are the stages of GPCR
- Neurotransmitter binds to receptor causing GDP to be exchanged for GTP
- G protein splits and activates other enzymes
- Breakdown of GTP turns off G protein activity
- Chemical reactions lead to amplified signal
77
What are the ways of neurotransmitter deactivation
- Deactivatating enzyme
| - Reuptake
78
What does Glutamate do
- Causes major fast excitatory neurotransmitter in the CNS
- Very widespread through the CNS
- Activates different types of receptors
79
What is normal neuronal transmission of glutamate used for
Involved in learning and memory processing
80
What types of neural integration are there
- Spatial, three inputs coming in at once from different axons
- Temporal, multiple action potentials coming from the same axon
81
What does GABA do
- Major inhibitory neurotransmitter
| - Activates an iontropic receptor which leads to hyper-polarisation
82
GABA receptor is enhanced by
- Ethanol
- Benzodiazepines
- Barbiturates
- Neurosteroids
83
EPSP can be decreased or abolished by
IPSPs from inhibitory neurons that are active at the same time
84
Autoreceptors
- Located on the presynaptic cleft
- Respond to neurotransmitters in the synaptic cleft
- Regulate internal process controlling synthesis and release of neurotransmitter
- Generally g-protein coupled
- Don’t cause depolarisation
- Negative feedback receptors
85
Autoreceptors are not the same as
Reuptake sites
