1
Q
Central nervous system (CNS)
A
All parts of the nervous system within bone; spinal cord, brainstem, thalamus, cortex, etc.
2
Q
Peripheral Nervous System (PNS)
A
All parts not within bone; peripheral nerves (nerves in limbs)
3
Q
Brainstem
A
Connects the cerebrum to the spinal cord. Made of midbrain, pons, and medulla
4
Q
What are the 4 regions of the spinal cord (rostral to caudal)
A
Cervical (C1-C5) Thoracic (T1- T12) Lumbar (L1-L7) Sacral (S1-S4)
5
Q
Axons vs Dendrites
A
Axons transmit neural signals while dendrites receive them
6
Q
What are the most common type of cells in the nervous system?
A
Glial cells
7
Q
What are the types of glial cells?
A
Astrocytes - maintain ionic environment Oligodendrocyte- myelinates neurons to help them transmit signals faster Microglia - respond to injury and help clean up cellular debris
8
Q
What is a Nissl stain?
A
- A technique invented by Korbinian Broadmann that uses dyes to stain the cell bodies of neurons in a segment of cerebral cortex to see the distribution/density of neurons in that segment - Nissl stain has a stripped appearance since there are 6 layers of cells - Shows the cytoarchitecture of each area examined (each area of the brain has different)
9
Q
What is cerebrospinal fluid (CSF)?
A
aqueous, saline solution that surrounds neurons. It contains many ions including Na+, K+, and Cl-
10
Q
What are the 2 ways the ions can pass through the impermeable neuronal membrane?
A
- Ion transporters: transport ions via active transport (use of ATP) against their concentration gradients 2. Ion channels: Passive (no energy required). Allow ions to diffuse down the concentration gradient. both are selectively permeable to specific ions
11
Q
The Sodium potassium pump
A
- used ATP to move 3 Na+ ions out of the neuron and 2 K+ ions in - conc. K+ high inside and conc. Na+ higher outside
12
Q
Why is the resting potential of a neuron negative?
A
The concentration of K+ is greater inside than outside of the neuron (Na-K+ pump) and since the membrane is partially permeable to K+ due to K+ leak channels, K+ constantly diffuses out of the neuron which causes the inside to become more negative
13
Q
What is electrochemical equilibrium?
A
- When the net flow of a particular ion is 0. Flow in=flow out - The voltage at which this occurs is called the equilibrium potential
14
Q
What 2 processes establish an equilibrium potential?
A
- DIFFUSION: K+ diffuses out of the cell, down its concentration gradient 2. ELECTROSTATIC FORCE: as K+ diffuses out, the inside becomes more negative. K+ is attracted to the inside since opposite charges attract these processes work against each other to establish net flow of 0
15
Q
What does the Nernst equation calculate?
A
equilibrium potential of a single ion. (Numerator = 58)
16
Q
Positional terms of the nervous system
A
Rostral- Upwards Caudal- Downward Dorsal- Towards the back Ventral- Toward the front
17
Q
What are dermatomes?
A
a specific segment of skin supplied by neurons that correspond to a specific spinal level
18
Q
Midline
A
Line separating the left and right sides of the body
19
Q
Ipsilateral vs contralateral
A
same side vs opposite side
20
Q
Decussate
A
cross the midline. When an axon goes from left to right (vice versa)
21
Q
Efferent vs Afferent
A
Projecting away from reference vs projecting towards reference
22
Q
planes of sectioning
A
Sagittal- left/right Coronal (frontal)- front/back Horizontal- Top/bottom Parasagittal- off the midline
23
Q
Rules (approximations) of neuroscience
A
- Symmetry- nervous system is bilaterally symmetrical through the midline 2. Localization of function - Each part of the brain has its own function (Ex. the 4 lobes). Neurons in different areas perform different tasks. Function of different parts discovered by loss of function due to brain damage 3. Contralaterality- motion and sensation in the body is processed in the opposite sides of the body 4. Topography- finer scale localization of function. Neighboring parts of the body are controlled by neighboring neurons. More sensitive neurons + more motor control have more neurons/larger surface area in the cortex
24
Q
How do we know that events in the brain cause sensation?
A
- Local anesthesia: prevents APs and therefore you won’t feel 2. Electrical brain stimulation: Stimulate the brain and feel in other parts of the body 3. Stroke- if hand neurons are damaged, won’t feel sensation in the hand
25
How is an action potential started?
- when receptors are triggered by a stimuli (ex., pressure on skin), voltage gated ion channels open and allow sodium to flow in - Ion flow causes depolarization of the cell - if the depolarization is enough to bring the neuron to the threshold, an AP will be fired.
26
What are the stages of an action potential?
1. Polarized membrane is depolarized by a receptor or synaptic potential 2. VG-sodium channels open in positive feedback loop causing *RISING PHASE* 3. Na channels inactivate ending the rising phase, initiating the refractory period. (Top of the rising phase) 4. VG-potassium channels open, causing the falling phase and undershoot (Afterhyperpolarization- AHP) 5. Na channels close, ending refractory 6. K channels close ending the undershoot, cell is now (-), membrane is restored to resting potential
27
What does the GHK equation calculate?
Calculates membrane potential (in mV) that results from the contribution of ALL ions that can cross the membrane. Potential at any point in time. (use 58)
28
Why is the resting potential -65mV not -84mV (membrane potential of K)
Since there is always some permeability to Na+ even at rest. Some Na+ is continuously entering the neuron as K+ leaves
29
How do the VG- Na+ channels open?
The channels have a (+) gating charge, when the cell is polarized, it keeps the channels shut since the force of attraction between the positive and negative. As the cell becomes depolarized, the force of attraction weakens allowing the channels to open. This causes a positive feedback loop. As more Na+ channels open, more Na+ rushes in further depolarizing the membrane which causes more Na+ to rush in.
30
How is the rising phase stopped?
The voltage gated sodium channels have 2 gates, the activation and inactivation gate, both are positively charged. When the membrane becomes too positive, it repels the (+) charges inactivation gate causing it to be shut.
31
What happens during the falling phase/how does it start?
- The depolarization of the cell during the rising phase causes the VG-K channels to slowly open - K+ starts to leave the cell (concentration gradient and electrostatic repulsion), slowly repolarizing it.
32
How is the falling phase stopped?
As K+ exits the cell and becomes hyperpolarized, the electrostatic attraction between the negative interior and the (+) VG-K channel causes the gates to be slowly shut.
33
Transduction
Physical stimulus (Energy) transformed to electrical impulses
34
How does the action potential propagate through the neuron?
- moves like a wave - As Na+ enters the cell, it spreads and when it 'hits' the region of other closed channels, those regions become depolarized and the channels open
35
What are the 2 kinds of refractory period?
1) absolute refractory period - impossible for an AP to fire 2) Relative refractory period - harder to elicit an AP due to hyperpolarization
36
What are the pros and cons of the refractory period?
Pro: - Ensures unidirectional action potential conduction, away from point of origin Con: - Places upper limit on max firing rate of a neuron (can't have AP < 1ms after another)
37
What causes the absolute refractory period?
- this inactivation of Na+ channels. - When new sodium enters the cell, the channel cannot reopen if the channel is in the 'inactive' state. Only if it's in the 'closed' state.
38
What is the voltage clamp?
- A technique invented by Alan Hodgkin and Andrew Huxley that allows you to artificially 'set'/clamp the voltage of a membrane to measure the current flowing across the membrane
39
How is the voltage clamp conducted?
1) An electrode is inserted into a large diameter axon that is submerged in saline solution (mimics CSF), and another is placed into the solution 2) the electrodes are connected to the voltage clamp amplifier which measures the membrane potential 3) The voltage clamp amplifier is connected to another amplifier that compares the membrane potential to a desired (command) potential 4) when the membrane potential is different from the command potential, the voltage clamp amplifier injects or removes current from the axon via another electrode until they are equal 5) The current (ion flow) can then be measured at this particular voltage *this technique tells us a lot about how the ion channels work*
40
What are local anesthetics?
- Ex. Lidocaine, novocain, etc - block the VG Na+ channel where injected - blocks sensation by preventing Na+ from entering through the channel and therefore there are no action potentials (prevents rising phase from occurring) - The anesthetic will eventually 'pop out' of the channel
41
Tetrodotoxin (TTX)
- produced by bacteria found in the ovaries and liver of pufferfish - Blocks Na+ channels like lidocaine but has much higher affinity to the channel (lower chance that it will pop out) - Ingesting TTX can cause death since it paralyses the respiratory muscles
42
What factors cause an action potential to move slowly?
1) Axon has low membrane resistance, Rm. (Axon is leaky) - Easy for ions to enter/exit the membrane 2) Axon has a high membrane capacitance, Cm. (Axon is sticky) - has the ability to store charge - since opposite charges attract, (+) ions on the inside stick to (-) ions on the outside 3) Axon has high axial resistance, Ra. (axon is thin) - the smaller the diameter, the harder for ions to flow through
43
What was the invertebrate solution to slow action potential conduction?
- They evolved very wide axons that reduced axial resistance - downside is that there is not enough space in the organism for a bunch of large axons
44
What was the vertebrate solution to slow conduction of action potentials?
- They evolved myelin on some neurons - Fatty lipid bilayer membrane - Increases membrane resistance, and decreases membrane capacitance - Myelin insulates the axons
45
What are the nodes of Ranvier?
- Gaps in the myelin sheath where VG Na+ and K+ channels are located - increases the conduction speed of AP through *saltatory conduction* since AP can jump from node to node
46
What cells are responsible for making myelin?
In the CNS myeloin comes from glial cells (ologodendrocyte). Each branch of the oligodendrocyte binds to an axon and wraps around it. In the PNS myelin comes from schwann cells. Each cell binds to an axon and wraps around it.
47
What is the synaptic cleft?
The very small space between neurons. Neurotransmitters diffuse across the synaptic cleft to transmit a signal.
48
Quantal Transmission
Neurotransmitters are released in quantal packages called synaptic vessiles (Pouches of lipid bilayer membrane). Release of the neurotransmitters from neurons is called quantal release.
49
How does quantal release occur?
When an AP comes and the cell becomes depolarized (+) the VG-Ca++ channel (+ gating charge) is repelled and opened. Ca++ rushes into the cell down the concentration gradient and binds to synaptic vessicles. The synaptic vessicle then releases it's contents by exocytosis.
50
What happens after exocytosis of neurotransmitters occur?
Neurotransmitters will bind with special receptors on the post synaptic neuron. When the neurotransmitter binds to the receptor, the ligand-gated ion channels open. the ions in the CSF enter the post-synaptic cell (this is how the voltage changes in the post-synaptic cell).
51
How is the Ca++ concentration gradient maintained?
1) Ca++ pump- Uses ATP to pump out Ca++. 2) Na+/Ca++ ion exchanger- Uses the energy created from Na+ passivley entering the cell to expell Ca++ (Like a water wheel).
52
What are the molecular mechanisms of transmitter exocytosis?
1) Vesicle docks- 2) SNARE complexes form to pull the vessicle down towards to membrane presynaptic membrane. 3) Entering Ca++ binds to *synaptotagmin*. 4) Ca++ bound synaptotagmin catalyzes membrane fusion.
53
What are examples of small molecule amino acid neurotransmitters
Glutamate: most common excitatory neurotransmitter. GABA: most common inhibitory neurotransmitter in cerebral cortex. Glycine: common inhibitory neurotransmitter in brainstem/spinal cord.
54
Driving force equation
Used to calculate the current of an ion.
55
What is an EPSP
a local depolarization. When the excitory neurotransmitter (glutamate) binds to the receptor channel, which then opens and allows Na+ into the cell, depolarizing it, pusing it towards threshold making it easy for an AP to fire.
56
What is an IPSP
A local hyperpolarizaion. When inhibitory neruotransmitter (ex. GABA) binds to a receptor channel, the channel opens and becomes permeable to Cl-, which hyperpolarizes it, moving it further from threshold making it harder for an AP to fire.
57
What is spatial intergration (Summation) of EPSPs
When many different EPSPs occur simultaneously from many different presynaptic neurons. The further away the EPSP is from the axon hillick the smaller it is since Na+ ions can stick and leak.
58
What is temporal integration (summation) of EPSPs
Many EPSPs from 1 singular synapse add together overtime.
59
What is spatiotemporal integration (summation) of EPSPs and IPSPs
When you have simultaneous spatial and temporal EPSP and IPSP. if total EPSP - total IPSP > 50mV then an AP will be fired.
60
What is the patch clamp?
Techneique that allows for the direct recording of ionic currents from cell surface ion channels. Invented by Erwin Neher and Bert Sakmann.
61
What are the types of patch clamp recording?
1) Cell-attached recording: - micro-pipette placed over a singular ion channel - current of that single ion channel is measured with an amplifier (shows when the channel is open vs closed) - used to compare responce character in different channels 2) Whole-cell recording: - a strong pulse of suctio is used to rupture the membrane such that the cytoplasm becomes continuous with the interior of the pipette - allows for the measurement of electrical currents from the entrie cell 3) Inside-out recording: - when the seal is formed around the membrane, its removed from the cell yet still attatched to the pipette - allows for the measurement of single channel currents while also changing the medium that the intracellular surface is exposed to 4) Outside-out recording: -If the pipette is retracted in whole cell recording the ruptured membrane is removed and the ends will anneal with each other leaving the extracellular surface exposed - allows us to see how channel activity is influences chemical activity.
62
grey matter vs white matter
Grey matter- area of spinal segment made of cell bodies and dendrites. White matter- area of the spinal cord segments comprised of myelinated axons.
63
primary afferents
sensory neurons that convey impulses from the skin to the spinal cord.
64
dorsal root ganglion
nodule just outside of the spinal cord. contains all of the cell bodies.
65
What are the different types of somatosensory axons?
1) Mechanoreceptors - respond to touh and pressure - A-Beta axons - Merkle, Meissner, Pacinian, and Ruffini cells are the reveptor types - Large in diameter - High conduction velocity 2) Thermo- and Nociceptive - respond to pain and temperature - A-Delta and C-fibres - free neve endings are the receptors - small in diameter - slow conduction speed.
66
What is the first and second pain?
when you touch something hot the A-delta axons and C-fibres repond - since the A-deltas travel faster, you forst feel the sharp first pain - a while after you feel tha duller second pain when the c-fibres eventually synapse in the cortex.
67
Describe the Dorsal Column Medial Lenniscus pathway (DCML)
Pathway for the A-Beta axons to relay sensations of touch and pressure - When the A-beta signal comes in, it assends rostrally in the dorsal white matter (dorsal column) - When the axons reach the dorsal column nuclei (grey matter) they release glutamate onto the cell bodies of the secondary neurons in the nucleus - The action potentials of the secondary neurons cross midline since the axons decussate in the medulla - The secondary axons continue ascending rostrally until they reach the Venteroposterior lateral (VPL) nucleus - The neurons in this nucleus receive glutamate from the secondary axons and then extend to and synapse in the thalamus - As the axons enter the spinal cord, they stay as close as they can to the midline. The more rostral you are in the body, the more lateral the neurons are.
68
Describe the spinothalamic tract (STT)
Pathway for A-delta and C axons - When these axons come into the dorsal horn, they synaose immediately, releasing glutamate onto secondary neurons which decussates at each spinal level and travel rostrally all the way up to the thalamus - In the thalamus, the second-order neurons release glutamate onto the cell bodies of neurons in the VPL nucleus when then extend to the thalamus - In the STT, when the second order axons decussate, they go as far lateral as they can, therefore, the more rostral, the more medial.
69
Totography of Somatosensory tracts
The most caudal spinal levels will not have axons that respond to rostral body parts.
70
What are the types of Somatosensory receptors?
Pain and temperature: - Free nerve endings Touch: - Meissner -Merkle cells - Ruffini - Pacinian *each receptor has a different feature of touch*.
71
Microneurography
A technique used to find the receptive feild of an axon - a needle is inserted into the skin, and lightly tapped to find the area of the skin that cause action potentials in a specific neuron.
72
For each mechanoreceptor, what is the size of their receptive feild and the stimuli it best responds to?
1) Meissner - Small, and low frequncy vibration 2) Merkle - Small, and static indentation 3) Ruffini - Large, and skin stretch 4) Pacinian- Large, ad high frequency vibration.
73
What mechnoreceptors are slowly adapting?
Merkle and Ruffini - When a stimulus is applied there is a dynamic phase (lots of APs) but when the pressure is maintained, the number of action potentials is reduced.
74
What mecahnoreceptors are quickly adapting?
Meissner and Pacinian - if you press down of the skin and hold, it will only responds to the innital pressure.
75
How do merkle cells contribute to mechanotransduction?
When the skin is pressed: 1) Mechanically-gated ion channels n the A-beta membrane open letting in ions (Na+) 2) The courses the first dynamic phase of action potentials 3) Mechanically-gated ion channels in the merkle cell membrane also open letting in ions (Na+) 4) This depolarizes the merkle cell which results in opening of Ca++ channels 5) as a result, a neurotransmitter is released onto the A-beta axon which contains transmitter receptors 5) this causes the second static phase of action potentials.
76
Where is the primary somatosensory cortex located?
- postcentral gyrus of parietal lobe - Caudal from the centre sulcus.
77
What are the divisions of the primary somatosensory cortex?
3a - mainly proprioceptive (body position) 3b - light thoch, very small RFs 1 - light touch, large multi-digit receptive feilds 2 - proprioceptive and light touch.
78
What is somatosensory plasticity?
- For neurons that respond to a limb that is lost, the somatosensory map will eventually change and neurons that used to respond to lost limb will start detecting form other digits around it - the cortical representation will change do to deafferentation (lack of afferent input).
79
phantom limb
- still feel as if the limb is there even though there is no limb there - will continue until cortical area shrinks.
80
How does heat transduction work?
-there are some A-Delta axons that respond to the cold and some the respond to heat - when the skin is heated, there is an increase in action potentials from the hot receptors and a decrease from the cold receptors - when the skin is cooled we see the opposite.
81
How do heat transducers work?
- TRPV1 -they are heat gated and permeable to Na+ and Ca++ - when heat is sensed the channel opens and action potentials fire.
82
What is capasaicin?
- Is a protein that causes food to be spicy - Capasaicin can bind to the TRPV1 receptor which causes it to open, triggering action potentials.
83
Why does menthol taste 'cold'?
Menthol brings to TRPM8 allowing AP to start giving sensation of cold.
84
What is referred pain?
- pain felt in parts of the the body when internal organs hurt - the A-delta and C axons of internal organs synapse on decorating 2nd order neurons which also respond to other parts of the skin - They converge.
85
Why do you rub an area on the skin when you're hurt
- The A-beta axons responding to the rubbing will synapse onto the an inhibitory inter neuron in the dorsal horn - the inhibitory neuron will will release GABA onto the neruon recieving the pain - This causes hyper polarization and few action potentials will occur, thur reducing pain.
86
What are the benefits of adaptation?
1) helps us to ignore constant, harmless stimuli, reducing distractions 2) Helps us to avoid saturation of neuronal firing rage, allowing us to detect the changes in stimuli intensity over a larger range of intensities.
87
The retina
Sensory membrane that lines the back of the eye.
88
What are the focusing parts of the eye?
The parts of the eye that help focus light onto the retina are: 1) The corena - Transparent membrane lining the front of the eye 2) Pupil - A hole in the cornea tht controls the amount of light that enter the eye 3) Lens- A transparent membranes that works with the cornea to focus light (behing the aqueous humor).
89
What are the refracitve errors?
Emmetropia (normal vison) - correct focusing of light onto the retina. Myopia (Near sightedness)- The focal plane is in front of the retinal because the eyeball is too long or the cornea is too curved. *light comes into focus before hitting the retina causing a bulrt image when it finally does*. Hypertropia (Farsightedness) - The focal plane is behind the retina because the eyeball is too short of the cornea is insufficiently curved. *light does not converge before it hits the retina, meaning its unfocused when it hits it*.
90
Snells law
91
how is the retina inside out?
- The light needs to pass through other cells to reach the photorecetors that process the light and create electircal signals - these signals must then pass pack through the retina to the retinal canglion cells wich will send on AP to the thalamus via the optic nerve.
92
What is the blind spot?
- the point at which the optic nerve leaves the eye (optic disc), creating a "blind" spot because no receptor cells are located there - It is located in the nasal retina.
93
Descride the structure of the retina
Pigment epithelium - Most inner layer, where photoreceptors are embedded Photoreceptors- Contain discs with light absorbing pigment in them. They absorb the light and convert it to a signal, this causes the release of neruotransmitters onto efferent axons Horizontal and bipolar cells Ganglion cells.
94
Shedding of photoreceptor discs
- Overtime, the discs containting the pigment move to the back of the eye towards the pigment epitherlial cells - Theses discs are shed and phagocytosed - New discs are always added to protect fron too much harmful UV rays.
95
Phagocytosis of photoreceptor discs
- Discs begin to curl - the tip becomes spherical - the tip (old discs separates from the rod) - tip in engulfed byt pigment epithelium.
96
What happens when light is flashed on a photoreceptor?
- The cell hyperpolarized - the brighter the light, the more hyperpolarization - outward current (+).
97
What happens when the photoreceptor is in the dark?
- the cell is depolarized - There is a positive inward current of ions (dark current) - the mroe light, the less inward current.
98
What happens when the photoreceptor is in the dark?
- The cell depolarizes - ion channels are open, and Na+ and Ca++ can flow into the photoreceptor and K+ exits the cell - The channel The Na and Ca+ enter through are gated by intracellular ligand called cGMP (cyclic guanosine monophosphate) - due to the depolarization and Ca++ entering.
99
the cell is depolarized
There is a positive inward current of ions (dark current)
100
What happens when the photoreceptor is in the dark?
The cell depolarizes
101
ion channels are open, and Na+ and Ca++ can flow into the photoreceptor and K+ exits the cell
The channel The Na and Ca+ enter through are gated by intracellular ligand called cGMP (cyclic guanosine monophosphate)
102
What happens when the photoreceptor is in the light?
cGMP is degraded when the photoreceptor absorbs light (cGMP concentration reduces)
103
The channel then closes, and Ca++ or Na+ cannot enter into the cell
K+ still leaves though the leake channels and thus we have hyperpolarization
104
The brighter the light, the more cGMP is degraded
Since there is no Ca++ channels open, the neurotransmitters will not be released
105
this is a graded response; the brighter the light, the more cGMP broken down
photoisomerization
106
In rods and cones, there are protiens called opsin which contains retinal (the light absorbing molecule)
When retinal absorbs the light, the shape of the retinal changes (cis -> trans)
107
This inly happens fro certain wavelengths of light, retinal influences the wavelenght of light retinal absorbs
What happens when retinal absorbs light and undergoes photoisomerization?
108
The enzyme transducin is activated
Transducin activates phosphodiesterase (PDE)
109
PDE decrades cGMP into GMP
cGMP channels close
110
What is photoadaptation?
Adjustment to long term light exposure
111
how does photoadaptation work?
When the light is left on for a long period of time, the photoreceptors slowly start to depolarize again
112
When light comes on, it causes degargation of cGMP and closes the channels
When Ca+ is in the cell, it inhibits theenzyme guanylate cyclase, an enzyme that produces cGMP, thereforem when Ca+ is absent in the photoreceptors since the channels are closed, guanylate cyclase is not inhibited and can start producing cGMP again
113
this newly produced cGMP binds to the channels, opening them, allowing Na+ and thus Ca++ ions to enter and depolarizing the cell
how does the brain infer the coulour of an object?
114
from the relative cativation of the three cone types
the different coens will activate at different levels based on the light
115
What are the types of cones?
Bluse cones - respond ot short wavelengths
116
Green cones- respond to medium wavethengths
Red cones- respond to long wavelengths
117
Sensitivity in rods vs cones
rods are more sensitive than cones and therefore are better able to seen in the dark
118
rods are longer (have more discs and increase probability light will hit them) and have more photopigment
convergance in rods vs cones
119
many rods onverge onto the same bipolar cell
only one cone converges onto each bipolar cell
120
Amplification in rods vs cones
rods have greater amplification, closing more Na+ channels in response to the same abount of absorbed light
121
Spatial acuity in rods compared to cones
cones have better acuity than rods
122
cones are densely packed in the fovea which lacks overlying axons and blood vessels ( the avascular zone)
due to the less convergence, cone have better spatial acuity because you know exactly where the light came from
123
What are off-center bipolar cells
they have a normal glutamate receptor (ionontropic)
124
since cones hyperpolarize in light, they release less glutamate onto the off-center bi-polar cells
Causes bi-polar cell's Na+ channels to close and become hyperpolarized as well
125
Dark -> depolarizes
Light -> hyperpolarizes
126
What are on-centre bipolar cells
have a metabotropic glutamate receptor
127
When cones hyperpolarize in the light and release glutamate onto on-centre bipolar cells, the cell's Na+ channels opne
this causes the bipolar cell to be depolarized in response to light
128
How does the ionotropic glutamate receptor work?
It is a ligand gated channel
129
Glutamate will bind to them, causing them to open and let the ions through
How does the metabotropic glutamate receptor work?
130
These recepors are G-protien coupled
gutamate will bind to the G-protein to activate it
131
the G-protien sends intracellular messages to open the channel
What is biolistic transfection
132
The process of shooting DNA cloved gold-particles into the nucleus of the cell.
Once the DNA is in the nucleus, the cell will transcribe the DNA
133
this is used to show the morphology of the retinal ganglion cells and where their glutamate receptors are
In an on-center ganglion cell, what will cause the maximum firing rate?
134
When the centre is light and the surrounding is dark
Followed by when the center and surround are both light, and then when both are dark.
135
contrast in important
Explain the mechanism for why the max firing rate of an on-center ganglion cell is when just the center is light.
136
in the dark, surround cells depolarize, releasing glutamate to horizontal cells
The horizontal cells depolarizes and releases GABA onto the center cone, further hyper-polarizing it.
137
Since light hyperpolarizes cones, the extra polarization give the illusion of increased brightness.
What are colour opponent ganglion cells?
138
ganglion cells that respond to different colours
Ex. Red in the center, green on the outside
139
What are horizontal cells?
Laterally spreading cells that connect surround and center cones
140
What are the cortical layers and where do they send their axons
1 - not cell bodies, only axons. no projection to other areas
141
2 and 3 - Send axons to and receive axons from other cortical areas
4 - recieve axons from the thalamus
142
5 - send axons to the brainstem and spinal cord
6 - sends axons to the thalamus
143
What is the organization of the Primary Visual Cortex (V1)
- The primary visual cortex has contralaterallity and visuotopic organization
144
Contralaterality:
The left visual feild activates neurons in the right visual cortex, vise versa
145
Visuotopic Organization;
the neurons responding to an image activate the area of the brain that correspond to the area of that image
146
What number nerve is the optic nerve?
CN II
147
What is the retino-geniculo-striate pathway?
Involves the lower visual field being carried by optic radiations which travel up through the parietal lobe. This information is then represented at the upper part of the sulcus.
148
What is the LGN
- The lateral geniculate nucleus
149
Where the output from the retinal ganglion cells
Describe the receptive feilds of the neurons in the LGN
150
- Similar to the the retinal ganglion cells
- Circular (center-surround)
151
Describe the receptive feilds of neurons in the V1
- the receptive feild of the V1 cells are bars of light that are oreinted at a specific angle
152
- this is due to the converagnce of the LGN cells
What does it mean for a neuron to be orientation tuned
153
That specific neurons respond best to a bar or light in a particular angle
What are orientation columns
154
- The neurons in the same cortical column of the cortex respond to the same orientation.
What is the V1 population vector
155
- A method used by the brain to infer the orientation of the stimuls
- Add all of the vecors of each neuron that is firing to determine the direction that stimulas is moving
156
What are occular dominance columns?
- Each layer of the LGN responds to neurons from one eye or the other
157
- This pattern is reflection into the V1
- When you move up or down in a specific layer of the cortex, all of the neurons will respoond to the left or right eye preferentially
158
- within each occular dominance column, there is also orientation columns where each neuron will respond to stimuli at a specific orientation
- Created the ice cube model
159
How is depth interpreted?
- The fixation point falls on the fovea of both eyes
160
- The further the stimulus, the more nasally it will hit the retina
What is the result of bilateral damage to V5 (dorasl path)
161
- Cerebral akinetopsia
- "timelapse images"
162
- no continuous veiw of motion
What is the result of bilateral damage to V4 (ventral path)
163
- cerebral achromatopsia
- innability to see colour
164
How cam movement direction be inferred?
- Using the population vector (the direction is the neurons preffered motion direction and the magnitude is the firing rate)
165
- The vectors are added tip-to-tail
How can adaptaion in the foring rates of neurons cause illusions?
166
- ex. waterfall illusion
- When staing at the waterfall for a long time, the downwards cells in the MT adapt and begin to fire less
167
- When the motion stops, the adapted neurons fire even less and and have lower firing rates than the upwards neurons, making it look like the neuron is moving upwards
What is glutamate photo-uncaging?
168
- brian tissue is bathes in solution with caged glutamate in it
- Cages glutamate is unable to bond to recepto until a uv light un-cages glutamate
169
- A UV light is flashed on specific area of the brain tissue to activate neurons in that position
- A whole cell patch clamp is then used to measure the activation at other neurons to determine the connectivity
PNB 2XB3 - NEURO
flashcards
Decks in class (5)
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