Psych neurons Flashcards
1
Q
What is the neuron doctrine and who came up with it
A
The nervous system consists of discrete individual cells
Santiago Ramon y Cajal (1888)
2
Q
who came up with the term neuron
A
Heinrich Wilhelm Waldeyer
3
Q
function of neuron
A
information processing and transmission
4
Q
How many dendrites/axons can there be
A
lots of dendrites, 1 axon
5
Q
Where does integration take place
A
axon hillock
6
Q
where does the input come in
A
dendrites
7
Q
where does the output leave from
A
Synapse, terminal bouton
8
Q
3 types of synapses
A
Axosomatic synapses
Axodendritic synapses:
Axo-axonic synapses:
9
Q
What is the difference in charge useful for
A
stored energy
10
Q
What is the charge distribution at rest
A
more negative inside and more positive outside
11
Q
What is the resting potential and what does it mean
A
-70 mV
means that the inside of the neuron is 70 mV less than the outside.
12
Q
high electrical potential meaning
A
where a positive charge would have the highest possible potential energy
13
Q
What do ion channels transport and what are their characteristsics
A
Na+, K+, Ca2+, Cl-
Can be gated
Passive
14
Q
What do ion pumps transport and what are their characteristsics
A
Na+/K+, Ca2+
Active –> requires energy
15
Q
Are there more non-gated potassium or sodium channels
A
more potassium
16
Q
Electrochemical and concentration gradient for potassium
A
Concentration gradient going out of the cell
Electrical gradient going into the cell
17
Q
Electrochemical and concentration gradient for sodium
A
Concentration gradient goes into the cell
Electrical gradient going into the cell
18
Q
Where is the electrical potential the highest
A
Outside the cell –> more positive
19
Q
How are sodium and potassium distributed across the membrane
A
More sodium outside and more potassium inside
20
Q
What does the Nernst equation let us calculate.
and what does it take into account vs not
A
Lets us calculate the difference in electrical potential across a membrane for a single type of ion
doesn’t take into account other ions
takes into account: charge, temperate, gas constant
21
Q
What is the main driving force of the resting membrane potential
A
Potassium
equilibrium potential for just potassium is about -70 mV
22
Q
How many ions does the sodium potassium pump move
A
For 1 molecule of ATP:
2 K+ in
3 Na+ out
23
Q
4 neurosignalling steps (loop)
A
Initiation of axon potential (axon hillock)
Propagation of action potential (axon)
synaptic transmission (synapse)
Synaptic integration (axon hillock)
24
Q
When does hyper polarization occur
A
when cell receives IPSPs –> pushes potentials lower
25
what are IPSPs and EPSPs
Inhibitory Postsynaptic potentials --> more negative charge
Excitatory Postsynaptic Potentials --> more positive charge
26
when does depolarization occur
when the cell receives EPSPs --> pushes potential up
27
Threshold potential
-55mV
28
characteristics of an AP
Rapid depolarization and repolarization
All or none → same way every time
29
What is constant in AP
Constant time course (1ms)
Constant amplitude (100 mV) above resting
30
How long is the refractory period
~5 ms
31
Voltage gated ion channels characteristics for Na and K
Passive transport
Sodium channels have activation and inactivation gate
32
Action potential events
1. At threshold, voltage-gated Na+ channels open, and positive Na+ ions flow into the cell
2. As depolarization continues, even more voltage gated Na+ channels open, increasing depolarization
3. Voltage-gated K+ channels open, and K+ ions flow out of the cell
4. Voltage-gated Na+ channels close, while voltage-gated K+ channels are still open → leading to hyperpolarization --> absolute refractory period
5. Voltage-gated K+ channels close when the membrane is hyperpolarized (below resting potential), and the membrane potential returns to a steady state at the resting potential --> relative refractory period
33
Absolute refractory period
During hyperpolarization, another action potential cannot be generated
34
Relative refractory period
Occurs when membrane is returning to resting
During the relative refractory period an action potential could fire but it would need stronger input
35
Hodgkin-Huxley model:
Mathematical model of action potentials → described in terms of an electrical circuit
36
Electronic conduction characteristics
Passive
Relatively fast
Travel short distances
Exponentially attenuating --> weakens quickly
37
Propagation of an AP characteristics (Self-regenerating propagation)
Each AP in a certain location causes an AP in the adjacent side
Active
Relatively slow
Self-regenerating
Travel long distances
In only one direction
38
Saltatory conduction characteristics
Relatively fast
Self-regenerating
Travel long distance
Active process
Conserves energy
39
How saltatory conduction works
It combines electrotonic conduction and AP
There is electronic conduction and it dissipates (but has enough signal to still fire an AP) then is boosted by the firing of an AP so it can travel to the next node.
Myelin speeds up the electrotonic conduction so it can reach the next gap and trigger another AP
The electrotonic conduction triggers the opening of voltage gated ion channels in the gaps --> an action potential is fired
40
In saltatory conduction, where do the APs occur and where does the electrotonic conduction occur
AP: in gaps --> Nodes of Ranvier
electrotonic: in myelin sections
41
Speed of propagation of an AP and what it depends on
As fast as more than 120 m/s and as slow as 1 m/s
Depends on:
axon diameter --> fatter is faster
Temperature
myelination
42
What does the neural coding consist of for an AP
pattern of firing
Rate → how frequently they fire
Duration → for how long thy fire
Timing → firing together or out of phase
43
What is synaptic transmission
passing signal from the presynaptic terminal to the post synaptic terminal
44
Synaptic transmission steps
1. Transmitter is synthesized then stored in vesicles
2. An AP invades the presynaptic terminal
3. Depolarization causes opening of voltage gated Ca2 + channels
4. Ca2+ enters through channels
5. Ca2+ causes vesicles to fuse with presynaptic membrane
6. Transmitter is released into synaptic cleft via exocytosis
7. Neurotransmitter binds to receptor molecules in postsynaptic membrane → causes ion channels to open or close → usually Na+ channels in postsynaptic cell
8. Postsynaptic channels open or close → causes changes in postsynaptic potenital
9. Postsynaptic current causes excitatory or inhibitory postsynaptic potential that changes the excitability of the postsynaptic cell
10. Vesicular membrane is received from the plasma membrane → forms another vesicle
45
What kind of channels are usually on the post synaptic cell
sodium
46
What ion causes the vesicles to fuse with the membrane
Ca2+
47
What do postsynaptic potentials depend on
Neurotransmitters (from the presynaptic cell)
Receptors (on the postsynaptic membrane)
48
What can postsynaptic potentials be (or how can they differ from each other?
Can be Excitatory (EPSP) or inhibitory (IPSP)
Can be Fast ( 1ms to 10 ms) or slow (100 ms to minutes
49
Reasons why we have IPSPs
- Prevent runaway firing of APs
- control the energy consumption of the brain
- Contribute to important oscillatory patterns of neural activity
Provide the basis for “negation” or NOT, → not doing something is important to human functioning
50
How many neurotransmitters have been discovered and what can they be
over 100
ions to single amino acids to complex proteins
51
2 major CNS neurotransmitters
Glutamate --> primary excitatory
GABA --> primary inhibitory
52
Other important neurotransmitters
Acetylcholine
Serotonin
Dopamine
Norepinepherine
Histamine
53
Amino acids neurotransmitters
glutamate and GABA
54
Monoamines neurotransmitters
Dopamine, norepinephrine, histamine, serotonin
55
Peptides neurotransmitters
oxytocin, endorphin
56
gas neurotransmitters
CO2
57
Other neurotransmitters (exotic)
acetylcholine
58
Characteristics of neurotransmitters
Made and stored in the presynaptic neuron
59
Types of reuptake
Active reuptake: Neurotransmitter goes back into presynaptic neuron
Enzymatic breakdown
Diffusion: molecules diffuse to an area of lower concentration
Glia help with reuptake
60
Types of receptors and where they are found
Metabotropic or ionotropic
found on dendrites of postsynaptic cell
61
Ionotropic receptor facts and example
Ligand gated ion channels
Fast
Nicotinic ACh (acetylcholine) receptor channel
start in 1-2 ms and last 10s of milliseconds
62
Metabotropic receptors
Long chain of events (Second messenger cascade) leads to opening of channel
Slow
G-protein-coupled receptor
start in 100s of miliseconds and last seconds
63
Electrical transmission (gap junction) characteristics and where they are mostly found
Fast
Direct electrical and chemical conduction (no neurotransmitters)
Low plasticity --> not specific
No amplifcation --> can't get inhibition
Mostly in PNS
64
How does a PSP travel from the synapse to the axon hillock
electrotonic conduction
65
Strength of PSP at trigger zone depends on
Strength of PSP at the synapse
Distance from the synapse
Time since the AP
Time Course of PSP at the synapse (when it gets there)
66
Spatial summation
PSPs from different synapses (i.e different locations in space)
67
Temporal Summation
: PSPs from the same synapse (ie. different points in time)
68
Integrate and fire model using computation characteristics
At each point in time, the neuron sums all of its inputs, and fires or not
The inputs are graded (vary along a continuum/ can vary)
The output is all or none
69
Are inputs to the AP graded
yes
70
3 logical operations
AND, OR, NOT
71
What can we compute with the 3 logical operations
Everything that is computable
72
Church-Turing thesis:
effectively calculable function if a computable function
Anything that you can compute can be done using AND OR NOT
Helps us understand neurons
73
Computational universality:
All Turing complete systems are computationally equivalent in what they can compute → all systems will compute in the same way → even if they look every different (neurons vs silicon)
Helps us study brains using computers
74
Alan turing work
Universal Turing machine (computation)
Broke enigma code
Turing test (test is AI is intelligent
75
Does the leg reflex circuit go to the brain
NOPE only goes to spinal cord
76
Reflex circuit steps
When the leg gets hit with a hammer, the axon from sensory (afferent) neuron brings excitatory signal to spinal cord through the dorsal root
The excitatory signal is passed on to a motor (efferent neuron) and the axon leaves through the ventral root (excitatory signal) → this causes the extensor muscle (on top of leg) to contract
The signal from the sensory neuron causes an inhibitory interneuron in the spinal cord to fire which causes the motor neuron that is going to the flexor muscle (under the leg) not to fire → muscle relaxes
77
Artificial neural networks usefulness
understanding the mind and brain --> stimulation and prediction
Artificial intelligence --> to control robot
78
How does GFP work
The isolated gene for GFP is inserted into DNA (of another organism) near the gene for a target protein
When the target protein is expressed, so is GFP → glows green
79
What colours can a brainbow trans gene express
Red, cyan, yellow
80
how does the expression of rainbow trans genes occur when you have 1 trans gene
3 fluorescents are interested and only the first one is expressed
Some of the cell offsprings lose the red → only express blue
Some of the cell offspring lose the blue → only express green
only expresses back one
Lose them through replication
81
What happens if you have mutliple trans genes
more colours!! due to the loss during replication
82
Do you control which neuron is which color during brainbow
no
83
Example of receptor on postsynaptic cell and what flows through it
ACh receptor and Na+ goes through
84
Speed of ionotropic receptor
start in one or two milliseconds, last tens of milliseconds
85
Speed of metabotropic receptor
Metabotropic: start in hundreds of millisecond, last seconds
