Week 1 Flashcards
(117 cards)
1
Q
Simple VS facilitated diffusion
A
Simple: Directly pass through membrane bilayer/ pores, down [] gradient, without ATP
Facilitated: Diffuse through membrane, with the assistance of carrier protein
No ATP, down []
2
Q
Is carrier protein a channel?
A
No
There’s conformational change that opens the protein, and one end is always closed
3
Q
What is ATPase
A
Pump that hydrolyze ATP as energy, use to active transport stuff against []
4
Q
What is secondary active transport
A
Energy from one substance going down [] is used to power another substance to move against [], so no ATP hydrolysis
5
Q
What is channel?
A
Membrane spanning protein forming a pore, that only specific molecules can pass through
6
Q
What is gated channel
A
Channel that is usually closed, and open only in certain situation
can be ligand gated (open upon binding) or voltage gated ( open under certain membrane potential)
7
Q
What is responsible for opening a voltage gated channel
A
S4 segment, which is positively charged
Under resting membrane potential, which is -7o mV, S4 is attracted to the -ve charge, at the downward position, and the gate is closed
When membrane is depolarized to -50 mV or above, the S4 moves back up as there’s not enough -ve charge holding it downward, so the gate is opened
8
Q
What is exocytosis 1 VS 2
A
Exocytosis 1: kiss and run, more rapid mechanism
Vesicles dock and fuse plasma membrane at fusion pore, releasing part of the contents (neurotransmitters)
This connect and disconnect action occur serval times until all contents are emptied
Use for low levels signalling
Exocytosis 2: full exocytosis
Complete fusion of vesicles with membrane, emptying all contents at once, vesicles become part of the membrane
Use for delivering membrane protein/ high level signalling
Must be counterbalance by endocytosis, or else the membrane become too loose
9
Q
What are the 2 conditions needed for generating membrane potential
A
1: concentration gradient, using ion pump
2: semi-permeable membrane, some some ion diffuse out more than other
10
Q
Where is sodium potassium pump found?
A
All cell membranes of all living cells
11
Q
For each ATP broken down, what is the action of Na+/K+ pump
A
Pump 3 Na+ out, pump 2 K+ in
Inside is more -ve relative to outside, as more cation outside
12
Q
What is the resting membrane potential?
A
-70mV
13
Q
What is the cell membrane more permeable to? in term of ions
A
K+ ion, which diffuse out of the cell, down concentration gradient, hyper-polarizing the cell (-ve inside)
14
Q
When does K+ efflux stop
A
When there are a build up of +ve charge outside the cell-, repel K+-> reach equilibrium ( equal electrical work VS chemical work)
15
Q
Why is membrane potential -70mV, even if K+ equilibrium potential is -90 mV
A
Na+ and Cl- are also involved to alter the actual mP
16
Q
What is the Na+ equilibrium membrane potential
A
+ 60 mV
17
Q
How is Cl- moved out of the cell
A
Repel by large -ve charged protein inside the cell
18
Q
How is voltage gated Na+ channel opened?
A
When membrane is depolarized to a threshold potential of -55mV
S4 move up and open the gate
19
Q
Wha is vicious cycle
A
More depolarization–> more Na+ channel open==> Na+ influx–> even further depolarization –> open even more channel
20
Q
How is Na+ closed
A
Inactivation gate will close the channel, half a milli second after the opening of activation gate
Block the Na+ influx
21
Q
How to remove inactivation of Na+ channel
A
MP need to fall back below threshold, by hyper-polarization
22
Q
What is Action Potential
A
AP is an impulse, a short lived change in MP, used as signal
23
Q
Where can you produce AP
A
Only in membrane that contain Na+ channel
24
Q
How is resting potential restored after firing AP
A
Na+ channel is inactivated, and K+ leakage brings the membrane potential back down
25
What are the 3 things needed for AP
1: high density of Na+ channel
2: Depolarize mP to threshold -55mv
3: K+ permeability (leakage of K+)
25
What is subthreshold stimulus?
Open some Na+ channel, but not enough to fire AP
26
What is supra-threshold stimulus
More then enough depolarization, which fire AP. But the magnitude of AP stays the same
27
How to increase intensity of stimulus?
Increase the frequency of AP--> more AP in the same time period
28
What is absolute VS relative refractory period
After inactivation of Na+ channel, the channel remain inactivated until membrane potential drop below threshold
Absolute: none of the channel are reconfigured (all are inactivated), absolutely no AP/ excitation no matter what
Relative: some, but not all channels are reconfigured. Need a stronger stimulus to generate AP, and the AP is smaller
29
Why is potassium chloride injection lethal?
Excess K+ destroy the [] gradient, so no K+ efflux
Without efflux, the membrane potential cannot be brought down (stay depolarized)
All Na+ channel will be permanently inactivated, no AP can be generated
All action, icnluding heartbeat, require AP
30
What is hyperpolarization
There's voltage gated K+ channel, that open when membrane is depolarized
This helps bringing down mP in a faster manner, and have a greater leakage of K+. This cause the mP to be more polarized than normal, which is hyper-polarization
31
What is impulse conduction
When AP is fire in one cell, influx of Na+ cause local reversal in potential ( depolarize from -ve to +ve)
This local reversal serve as a source of depolarizing current, so adjacent membrane ma also reach thrshold and fire AP
This repeat and pass along until reaching the axon
32
What cells are excitable?
Cell with voltage gated Na+ channel only
33
What cells can conduct passive current
Both excitable and not excitable cells
Not excitable cells however cannot generate AP
34
What is axon
Long extension of cell body that carry AP away to some other location, like a wire
35
What is lamda length constant
Measure how far a signal can be carried , to the point where the voltage dropped to 37% of original value
Greater length constant is better for conduction
36
How to increase length constant in nervous system?
1; increase diamater, so less internal resistance (from organelles), less voltage loss due to resistance
2: Increase membrane resistance, so less current leaking out
37
How to increase membrane resistance?
Myelination
38
What cell is used for myelination
Glial cells
39
What are the two specialized glial cells that create myelin sheath
Schwann cell of PNS
Oligodendrocytes of CNS
40
Is all axon myelinated?
No, myelination is adding bulk and taking up spaces, so only 20% of myelination
41
What is the gap between myelin sheath? What is its significance
Node of ravier
It is where AP generated, where Na+ channel is located
42
What is multiple sclerosis
Nervous system disease, caused by losing myelination
Affect brain and spinal chord function, slow down and blockage of signals
43
What is salfactory conduction
Only nodes are excitable
So it is bascially the jump of AP from one nodes to the next nodes
AP at one nodes bring the next 10 nodes to threshold, generating AP
The furtherest node (10th) depolarize the next 10 nodes, etc
44
Why is salfactory conduction safe?
Even if some of the nodes doesn't work, the depolarizing current can still skip through the bad nodes and move onto the healthy nodes, so AP is dafely conducted
45
What is remark bundle?
Unmyelinated axons is engulfed by schwan cell/ oligodendrocyte, without winding
This somewhat imporve the insulation
46
What's the velocity of conduction between myelinated VS unmyelinated axon
Unmyelinated axon has a lot of leakage, so conductance is much slower
47
Why can't AP turn around and repropagate in the direction of where it comes from?
The membrane before it will be in refractory period, so cannot fire new AP
48
What is electrical synapses
Adjacent membranes are connected through gap junction, and the connexins allow small ions to cross
Electrical signals (AP) is rapidly and directly transmitted from one cells to another, without releasing neurotransmitters
49
What is chemical synapse
After AP reach the axon terminal, the arrival of AP depolarizing current cause the release of neurotransmitter into the extracellular space between adjacent cells
50
What is the presynaptic surface and postsynaptic membrane
Pre: contain the vesicles of neurotransmitter, release through exocytosis
Post: contain specific membrane receptor that can bind to transmitter molecules
51
What trigger exocytosis of neurotransmitter vesicles
Ca2+ ion, which enter through voltage gated calcium channel, which reach threshold and open upon the arrival of depolarizing AP current
Ca2+ trigger cascade that result in exocytosis
52
Why is chemical synapses a "processing station"
This is because vesicle release is probabilistic, never 100% certain
AP does not guarantee vesicles release
This allow the complex emotion and behaviour of human, instead of acting like a simple machine
53
For transmitters binding to receptors on postsynaptic, what determines the actual effect that will occur?
The receptor determines the effect
54
What are the 2 postsynaptic receptors
Ionotropic, metabotrobic
55
What is the effect of ionotorpic receptor binding
Open ion channel, resulting in change of post synaptic potential (PSP)
56
What is the effect of cation specific receptor and anion specific receptor?
Cation (Na+, K+)= EPSP, excitatory, more +ve, depolarizing
Anion ( Cl-, K+)= IPSP, inhibitory, more -ve, hyper-polarizing
57
What is nicotine receptor for acetylcholine
Ionotropic effect open Cation channel, EPSP
58
Does ligands for ionotropic effect only act on ionotropic receptors?
No, they can act on metabotropic receptor as well
59
What is metabotropic effect
Binding of ligand to post-synaptic metabotropic receptor activates G-protein coupled enzyme, result in alteration in 2nd messenger
60
What are the 3 2nd messenger
cAMP, cGMP IP3
61
What is the speed of action of ionotropic VS metabotropic effect
Ion: very rapid
Meta: slower, take longer time
62
What is Beta-adrenoreceptor
Metabolic receptor that binding to Noradrenaline (NA)
Binding activate adenylyl cyclase--> increase cAMP production --> activate protein kinase --> phosphorylate Ca2+ channel --> increase Ca2+ influx
Important heart muscle--> increase contraction
63
What is beta blocker
B-receptor antagonist, block receptor from binding to NA
Use to decrease heart contraction, prevent excess activity of heart
64
Can PSP generate AP?
No, since PSP are generated in inexcitable membrane (cell body and neuronal dendrites), so no AP is initiated
The potential is graded potential
65
Where is AP made?
Trigger zone -- the beginning of the axon
66
How does EPSP ends up in AP?
EPSP, which is graded potential, spread through passive conduction to get to the trigger zone, so AP can be fired
To reach the threshold for AP, a lot of EPSP works together to reach threshold
67
What is EPSP summation
A lot of EPSP add up and work together to reach threshold and first AP at trigger zone
68
Why we need EPSP summation
Biological tissue is poor conductor, so single EPSP signal is not strong enough to fire AP, since signal is lost during travel
69
What potential can be added up?
Graded potential
AP is all or none, so cannot be added up
70
What are the 2 types of PSP summation
Spatial summation
Temporal summation
71
What is spatial summation
A lot of EPSP work together at the same time, in synchrony, to initiate AP
72
What is temporal summation
Not a lot of synapses, but they have high frequency of EPSP input
New EPSP add on pre-existing EPSP, before the old one dyes out
Together result in a large EPSP that can initiate AP
73
Where is IPSP located
In the cell body, between EPSP site and trigger zone
74
What is the advantage of IPSP location
Since it is right in between EPSP and trigger zone, closer to trigger zone
It can shunt depolarizing current EPSP out of the cell, stop it from reaching trigger zone
75
What is the mechanism of IPSP
Opening of Cl- channel, so Cl- can influx and bring mP back down (from +ve to -ve), prevent excitation --> inhibitory effect
76
Which one is more important, IPSP or EPSP?
IPSP
It is very accurate and precise, and control and shape the information
EPSP is more general and less accurate
77
What happen to PSP when ur drunk
More EPSP firing, less IPSP regulation
78
What is a spike train
When a long lasting strong stimulus is input into the post synaptic, and the depolarization of trigger zone sustain for a long period of time
The input need to be translated to a continuous stream of AP
79
How to generate a spike train?
When an AP is generated, it will enter refractory period
So after each spike, the membrane need to be hyper-polarized to restore the Na+ channel, using hyperpolarization, voltage gated K+ channel can rapidly repolarize the membrane below threshold, so Na+ channel is reconfigured and new AP can be fired
80
What is receptor potenital
Change in MP due to signal/ energy from exterior cue, eg pressure from touching
81
What are the two action of receptor protein upon receiving signal
1: open ion channel
2; G-protein coupled enzyme activation
82
What is one advantage of metabotropic effect
It can cause amplification
One stimulus can produce a lot of 2nd messenger
83
How does olfactory receptor work
Receptor protein bind to specific odorant, activate G-protein, activate adenyl cyclase, make cAMP, bind to ion channel and open ion channel, depolarization, depolarizing current travel to trigger zone, fire AP and send message to brain
84
Is receptor potential AP?
No, it is graded potential
85
How does receptor potential lead to firing AP
Travel and generate summation at the branch point (trigger zone), reach threshold and fire AP
86
How does sensory cell generate AP without fire AP itself
When sensory cell is depolarized, Ca2+ influx, and it trigger the release of neurotransmitter to next cell ( post synaptic neuron), and the post synaptic cell fire AP
87
How does taste receptor work
Binding of chemical to receptor on taste bud produce depolarizing current, which travel through the membrane and reach other end of the cell, open Ca2+channel, and Ca2+ influx trigger release of neurotransmitter to neighbouring cell, and the neighbouring cell produces AP
88
What is adaptation
"adapting" to stimulus
Change in MP by stimulus will not last forever, as the MP can decay overtime, even if the stimulus is constant
89
What are the two types of adaptation
slow and rapid adaptation
90
What is slow adaptation
receptor potential is sustained for duration of stimulus, interested in overall magnitude of stimulus
--> some receptor potential as long as there's stimulus, a slow decay
91
What is rapid adaptation
When stimulus is constant, the receptor potential decay to zero
Interested in the velocity of stimulus delivery
92
What is habituation
Show weaker response to identical stimulus that is repeated
93
What limit the impulse frequency?
Refractory period
94
What happen if stimulus intensity increase and reach the ceiling?
Recruit sensory neuron with higher threshold, which require greater stimulus to generate receptor potential
95
What is population code?
It is insufficient to have single specific proteins for all the specific stimulus
qualities
Population code= specific stimulus is coded by the ratio of activity from a number of receptors
eg: the code for a stimulus is :strong on receptor C, weak on receptor A&B
96
What is receptive field
Each sensory neuron cover a territory that it can respond to, a territory where u can activate that neuron
97
Why can you tell if 1 or 2 pencil is poking your finger tip, but not when ur poking ur back?
Back neuron has larger receptor field, so it is the same neuron responding to stimulus
Finger tip has smaller receptor field, so more neurons
98
What is blood brain barrier
Barrier between the blood general circulation and the brain, protect the brain from stuff that your don't want your brain to be exposed to, eg: neurotransmitter
99
What is interstitial fluid
The fluid bathing the neurons, which is isolated from blood
100
What is CSF
cerebrospinal fluid
Fill the cavities of the brain (in ventricles)
also isolated from the blood
101
What is the barrier between interstitial fluid and CSF
"Non barrier"
chemical composition of CSF and interstitial fluid is near identical, so there's free diffusion of chemicals between them
102
how to treat parksinson disease based on the fact of BBB
Parkinson= lack of dopamine
Can't treat with dopamine injection, as it cannot cross the BBB
Need to use L DOPA, which is dopamine precursor that can pass the BBB, and covert to dopamine when it is in the brain
103
Why does large amount of MSG makes you thirsty/ stiff neck
MSG cannot cross BBB, but can activate glutamate receptor outside the brain & the peripheral system, which may makes your thirsty/ stiff neck
104
Is the whole brain continuously protected by BBB?
No
Some place needs to communicate with the blood stream, eg: hypothalamus, directly connected to pituitary gland, and BBB is broken to allow hormone release
BBB is broken in area that interact with endocrine system, or require sensitivity to metabolites in plasma
105
What is meninges
It encases the brain and spinal, protective layers
106
What are the 3 components of meninges
Dura mater
Arachnoid membrane
Pia mater
107
What is subarachnoid space
Space between arachnoid membrane and pia mater, filled with CSF, so brain is floating in liquid suspension, provide cushion support
108
What is reticular formation
Collection of nerve cells that sit between brain and spinal, deal with connecting brain to behaviour
It shock is applied on it you pass out
109
How are endothelial cells in brain connected, to consitiute the BBB
They are bound by tight junction, so no gap for molecules to pass
110
What is ventricles
A cavities deep inside the brain, filled with CSF
111
How is CSF circulated
CSF produced in ventricles drain through the ventricles of the central canal, moves to the outer part of the brain (subarachnoid space), and finally exit at the top of the brain into venous sinus, back to general circulation
112
What is arachnoid villi
A pouch of the arachnoid tissue that stick out through the dura matter into the veinous sinus, where half of the CSF drain through into the venous system
113
Where is CSF produced from/ by
Mostly produced by choroid plexus, which line the ventricles, using plasma
114
What is lumber puncture
A therapeutic procedure, which collect sample of cerebrospinal fluid (CSF) for sample and diagnose
115
What is astrocytes
A glial cell that provide bridge between blood vessels and neurons
116
What is a function of glial cell ( energy related)
Astrocytes is efficient at glycolysis
It gets glucose from capillary for glycolysis
It produce lactate as an end product, and the lactate can be used by neuron to produce ATP more efficiently
