BIPN 152 Exam 1

covers LE 1-5 (up to material covered Tuesday 4/14), DI week 2-3 slides

(mainly know the degrees of magnitude)

• # of neurons in adult human brain

• average # of synapses made by a neuron

• # of synapses in child vs. adult brain

• the brain is % of our body weight, but it uses % of our energy

80-85 billion neurons in adult human brain (10¹¹)

average of ~7,000 synapses made by a neuron

~10¹⁵ synapses in child brain, ~10¹⁴ synapses in adult brain

brain is 2% of our body weight, but it uses 20% of our energy

parts of CNS (general ←2) (specific ← 5)

parts of PNS (general ←2) (specific ← 2 that are described)

CNS: spinal cord & brain

• cerebral hemispheres

• diencephalon

• cerebellum

• brainstem

• spinal cord

PNS: cranial nerves & spinal nerves

• sensory

  • (internal and external environment →) sensory nerves, ganglia, and receptors

• motor

  • visceral motor/autonomic nerves → smooth and cardiac muscle, glands

  • somatic motor nerves → skeletal muscles

state 3 ways biomedical research is funded

• Alexander Graham Bell developed the telephone with funding from wealthy parent of his student

• lots of government funding (for research) after WW2, but decreased since

• NIH (national institute of health) is the largest funder

model organisms commonly used in neuroscience research (8)

• c. elegans

• aplysia californica

• drosophila melanogaster

• mouse

• rat

• rhesus monkey/macaque

• human

• iPS cells / iPSCs

(^ all are listed in order of simple to complex neural circuits in terms of # of neurons, except for the iPSCs)

__

C. elegans (302 neurons)

Aplysia californica (15,000)

monkey (50 billion)

^^ this latter part is simple to complex neural circuits

state the 2 building blocks of the NS

__

the cell is the fundamental unit of living organisms, whereas

the neuron was discovered to be the fundamental unit of the (1)

• describe the 2 theories/models

  • which is wrong

who first used the term “synapse”

neurons & glia

__

the cell is the fundamental unit of living organisms, whereas

the neuron was discovered to be the fundamental unit of the nervous system

• reticular theory (Golgi): neurons are not discrete/distinct cells, but are fused together into ONE continuous/interconnected network (“continuum of protoplasmic links”)

  • where axons and dendrites branch into one another

  • BUT is wrong b/c there are synapses/tiny gaps between neurons, so it is NOT a continuous interconnected network

• neuron doctrine (Cajal): neurons are discrete entities/cells that communicate at specialized contacts/synapses (“protoplasmic kisses”)

_

Sherrington first used “synapse”

describe what Cajal discovered the __ __ of neuronal signal flow (2)

dynamic polarization of neuronal signal flow (aka directionality aka functional polarity) (aka that signals flow in ONE direction in neurons)

• inferred that in sensory systems, info should generally flow from sensory organs → to the brain

• found that dendrites are at the receiving end of a connection, axons deliver that info to the next neuron

  • ex. of neuron-to-neuron in vertebrate retina: photoR cells → bipolar cells → RG cells

name the 3 types of glia in CNS, 1 type in PNS

__

describe glia (3)

• its general functions (~6)

CNS: astrocytes (support), microglia (immune), oligodendrocytes (myelin)

PNS: Schwann cells (myelin)

__________

• more glia than neurons

• don’t directly participate in signaling, but are still important in neuronal signaling

• NOT excitable, BUT have ion channels

__

• supportive roles (3): trophic factors, remove debris, regulate synapse

-

• maintain extracellular ionic concentration

• speed up signal propagation (by forming myelin) ← b/c glia cells like oligodendrocytes & Schwann cells

• NT uptake ← NT uptake from synaptic cleft into astrocytes b/c astrocytes are part of the tripartite synapse

• help with structure during development

neurons are __

• includes 3 parts (not referring to dendrites, soma, or axon) (glia only have soma, usually no dendrites or axons)

• function (4)

neurons are cells

• membrane, cytoplasm, nucleus

__

functions (done w/in the parts mentioned above)

• cellular metabolism

• protein synthesis

• protein modification

• transport

for the functional polarity of neurons in a circuit

despite __, most neurons have a basic common structure

• describe the 3 parts involved & what they do

  • degrees of order of magnitude of axon

__

t/f: for many neurons, axons are VERY long compared to the dendrites

neurons have __ axon that can be highly __

state and def. 2 ways of branching of neurons

t/f: the directional flow of signals/info also occurs at the subcellular level, aka at synapses

despite heterogeneity/diversity, most neurons have a basic common structure

• dendrites & soma receive inputs

• soma integrate inputs

• axon makes & transmits the signal/nerve impulse to its targets (some of these axons are myelinated, so some have faster transmission of signals/nerve impulses)

  • axon is 6 orders of magnitude (few micrometers - tens of cm)

__

true

_

neurons have ONE axon that can be HIGHLY BRANCHED

• divergence: 1 axon → 10,000 different post- neurons (one to many)

  • 1 pre- branches/diverges to affect many post-

• convergence: multiple highly branched dendrites that receive multiple connections (from multiple neurons’ axons) (many to one)

  • many pre- converge to affect 1 post-

_

true

state 3 main parts of the brain (draw and label where each is)

def. meninges (name the 3 parts from outer to inner ← aka bone—3layers—brain)

• def. sulci vs. gyrus

_

the brain contains a rich __ (def.)

def. phrenology

cerebrum, cerebellum, brainstem

_

meninges: 3 layers of tissue that cover & protect the brain

• dura mater, arachnoid, pia mater

sulci - the folds (“suck”)

gyri - the ridges (“rise”)

__

the brain contains a rich vasculature (← arteries & veins)

phrenology: different brain regions have different functions

• (old study & was proven wrong)

the neocortex is organized into regions that specialize in specific tasks/behavior

name the 4 lobes & location relative to e/o

• what lobe are these in:

  • primary motor cortex (for mouth and lips)

  • auditory cortex

  • Broca’s area

  • Wernicke’s area

  • AND primary somatosensory cortex

__

state the 3 types of evidence to study/look at the specialized function and region of Broca’s and Wernicke’s area

• def./describe each, where 1 of them explains Broca’s & Wernicke’s aphasia

frontal lobe — anterior

• primary motor cortex

• Broca’s area (“fb”) ← speech production

parietal lobe — superior to temporal

• primary somatosensory cortex

temporal lobe — inferior to parietal

• auditory cortex

• Wernicke’s area (“tw”) ← speech comprehension

occipital lobe — posterior

__

• fMRI

  • looks at/gives information about brain structure & brain activity, where highlighted regions show higher activity

• brain stimulation during epilepsy surgery

  • stimulation via electrodes

• brain lesions (Broca’s/Wernicke’s aphasia)

  • Broca’s aphasia: bad at language production, but good at language comprehension

  • Wernicke’s aphasia: good at language production, but is meaningless speech & bad at language comprehension

for brain stimulation during epilepsy surgery

def. topographic map

• name 2 types of visualizations of this

__

parts of the body that are more densely __ occupy greater regions of the brain

_

t/f: different species organize their brain differently depending on what’s important to the organism, like the “whisker barrels” in rodents’ somatosensory cortex

_

t/f: certain sensory & motor systems have “crossed” innervation (contralateral) and also ipsilateral innervation

(^ aka crossing over or not of innervations/pathways that travel towards the primary motor cortex & primary somatosensory cortex)

topographic map:

• where adjacent regions of the periphery map (body) map onto adjacent regions of the brain, visualized w/ the:

  • motor homunculus (primary motor cortex)

  • sensory homunculus (primary somatosensory cortex)

^^ homunculus is a distorted map of body parts to the cortex

__

parts of the body that are more densely innervated occupy greater regions of the brain

_

true

_

true

def. the directions:

• lateral, medial

• anterior, posterior

• rostral, caudal

• dorsal, ventral

• superior, inferior

^^ how do some of these differ below the midbrain?

_

name and def. the 3 planes

• medial (towards middle), lateral (away from middle/center line)

• anterior(front), posterior (back)

  • rostral (nose), caudal (tail)

• dorsal (back/up), ventral (belly/down) ← like for rats

  • superior (up), inferior (down)

^^ below the midbrain:

• dorsal is posterior

• ventral is anterior

__

coronal / frontal / transverse plane

• into front and back

sagittal plane

• into R and L

axial / horizontal plane

• into up and down

white matter vs. gray matter (2 each)

_

fill in blanks

• the directions are either dorsal/ventral or rostral/caudal

white matter

• has the axon tracts (the communication pathways)

• is mostly myelinated axons

gray matter

• everything else (soma, dendrites, synapses, glia)

• is mostly unmyelinated axons

---

(hippocampus is “C” shaped)

when neurons are excited, they create nerve impulses (← def. term)

__

describe the 2 basic principles of somatosensory nerve responses/impulses

nerve impulses - transient/short-term changes in membrane potential that propagate down/along the nerve

__

basic principles:

• nerve impulses have a uniform size & shape (“elementary unit” ←→ unitary EPP/smallest mEPP)

• increasing stimulus strength will increase the frequency of nerve impulses, but does NOT change the impulses’ magnitude

  • aka nerve impulse frequency is encoded by stimulus strength

  • (stronger stim. → more APs released/higher frequency BUT has “quantal release”/same magnitude)

__ __ are the basis for membrane potential (name the 3 that determine Vm/membrane potential)

• where cell’s interior/intra- is __ relative to the exterior/extra- (describe in terms of the 3 ions)

__

neurons are electrically polarized cells

• name 3 types of potentials (describe each ← 1)

ion gradients ← Na+, K+, Cl- (not Ca2+)

• intra- is more negative than extra-

  • (at RMP, more intra- K+, while more extra- Na+ and Cl-)

__

• RMP

• action potentials

• graded potentials:

  • synaptic potentials

    • when external stimuli, like light, are transduced into electrical signals (from inside post- neuron)

  • receptor potentials

    • caused by NTs in the synapse binding to the post- cell/neuron (used by sensory neurons, from sensory receptor)

neurons exhibit 2 types of membrane potential changes: APs and graded potentials

• describe each (AP ← 4, graded ← 2)

• also describe RMP (4)

_

t/f: all APs are transient

• explain

APs (aka “spike”): elementary unit of nerve impulses ← transient (b/c delayed activation of VG-K+ channels reverse the de-)

• used for long-distance transmission

• is “all-or-none”

• first made at the axon initial segment (AIS) aka axon hillock, when Na+ influx → causes neuron to depolarize to ~ +30 mV

• need to reach the minimum threshold depolarization to trigger it (~ -55 mV)

graded potentials: ← transient

• used over short distance

• is a gradient in the magnitude of the response (is not all-or-none)

RMP:

• made by different ion concentrations across the membrane & the different permeabilities of these ions

• ~ -70 mV

• 3 major ions: Na+, K+, Cl-

• is maintained at around -70 mV by the Na+/K+ ATPase (against concentration gradient: 3 Na+ out, 2 K+ in)

__

true

• all APs are transient b/c VG Na+ channels will inactivate (at the peak) & VG K+ channels will open to repolarize the membrane potential back to its resting membrane potential

---

(picture)

• VGSC / VG-Na+ channels open during de-

• at peak, VG-Na+ are open & in inactivated state

• VG-K+ channels open during re-/hyper-

what happens if you block voltage-sensitive K+ channels?

AP is prolonged

describe 3 states of VGSCs

_

ion channels are typically multimeric transmembrane proteins (describe ← 1)

• closed - inactivation gate open, activation gate closed

  • (resting state)

• open - both gates open

  • (depolarization)

• inactivated - inactivation gate closed, activation gate open

  • (hyperpolarization IF also have open VG K+ channels)

__

part of the ion channel forms a voltage sensor that causes a conformational change when opening the pore

what happens if you block VGSC inactivation gate?

(blocking the VGSC inactivation gate means that it will stay open / inactivation gate is prevented from binding + closing)

AP is prolonged

• (in dep-, both inactivation and activation VGSC gates are open)

• the VGSC inactivation gate will stay open at & past the peak, which allows for more Na+ influx

• K+ influx cannot perfectly counter this effect, so there is slower re- and hyperpolarization → which is seen as a prolonged AP

t/f: oligodendrocytes (CNS) & Schwann cells (PNS) create a myelin sheath around some axons

_

rate AP conduction velocity for unmyelinated “C” fibers (peripheral nerve fibers) vs. myelinated fibers

• in PNS and/or CNS?

relevance of speed of AP conduction (1)

__

def. nodes of Ranvier

• what type of conduction?

true

_

unmyelinated “C” fibers (peripheral nerve fibers) ← PNS

• ~ 1 m/s

myelinated fibers ←- PNS or CNS

• ~ 100 m/s

the speed of AP conduction/propagation determines how somatosensory signals are perceived (ex: heat vs. cold, immediate sharp pain vs. dull throbbing pain)

__

nodes of Ranvier:

• gaps b/w myelin sheaths, where the current jumps from node to node which increases the speed of impulse travel along the axon

^ does saltatory conduction

what would failure of myelination (i.e. defect in oligodendrocytes or Schwann cells) do to circuit function? (1)

• name and def. 1 type of disease that could result from this (w/ 4 symptoms)

• is there a cure?

• slowed or failed conduction (which can lead to sensory and/or motor deficits)

_

multiple sclerosis (MS): an autoimmune demyelinating disease of the CNS (spec. demyelination of oligodendrocytes)

• symptoms:

  • motor weakness

  • pain

  • vision loss

  • cognitive dysfunction

(^ no cure; degree of axon and soma damage deter. the disease severity)

what specific neural circuit do nerve impulses (aka propagating APs) flow through? (1)

• describe the pathway of these signals

__

def. excitatory vs. inhibitory neurons (& each release what 2 specific NTs)

def. projection neurons vs. interneurons

__

describe the pathway (~1/2) of how a tap on the patellar ligament simultaneously causes the quadriceps to suddenly stretch/extend AND the hamstrings to suddenly flex/bend

via the sensory-motor circuit b/w the SC and brain

• from sensory neuron → DRG → spinal cord → brain stem → thalamus → primary somatosensory cortex → primary motor cortex → spinal cord → motor neuron (in muscles)

__

excitatory neurons

• release excitatory NTs (glutamate, ACh) to make target neurons MORE likely to dep- and fire APs

inhibitory neurons

• release inhibitory NTs (GABA, glycine) to make target neurons LESS likely to dep- and less likely to fire APs

__

projection neurons — axons extend long distance to targets

• (i.e. in green)

interneurons — axons connect to local targets / axons that connect sensory neurons to motor neurons

• (i.e. in red)

________

• tap on patellar ligament activates muscle spindles w/in the quadricep (← the extensor muscle) (muscle spindles — sensory organ that detects change in muscle length)

• the excitatory sensory neuron will send signals to SC

• directly triggers/activates the extensor motor neuron

• SO quads will contract→ causing knee to extend

  • (the sensory neuron activates the extensor motor neuron, so the quad stretches/knee extends)

___ WHILE THIS HAPPENS, there is also simultaneously-occurring reciprocal inhibition in order to have coordinated movement / to prevent opposing muscles from working against e/o ——

• tap on patellar ligament activates muscle spindles w/in the quadricep (← the extensor muscle) (muscle spindles — sensory organ that detects change in muscle length)

• the excitatory sensory neuron will send signals to SC

• that excitatory sensory neuron will activate an inhibitory interneuron

• that inhibitory interneuron will activate the excitatory flexor motor neuron

• SO hamstrings will contract → causing knee to flex/bend

• reciprocal inhibition causes flexor to relax

  • (the sensory neurons activates the inhibitory neuron, which inhibits the flexor motor neuron, so it does not stretch BUT relaxes instead)

imagine each

describe E, H, I, and J

recurrent lateral excitation: acts on the same neuron that just fired

_

recurrent cross inhibition AND lateral inhibition: acts on the next neuron

disinhibition: inhibits an inhibitory neuron

---

don’t have to memorize any of these, but just understand the basic concepts in this diagram

(MB can think of “lateral …” as the neurons in the same stage/step being equally affected)

what is made if a stimulus is too weak to produce an AP? (1)

t/f: even when MP reaches the AP threshold, some pulses can elicit an AP, but some still fail to do so

graded potentials

_

true

name the 3 types of mechanosensation

_

name the specialized nerve endings for the 2 of the 3 types of mechanosensation, pain, and temp

^ they all produce what type of potential?

mechanosensation (touch, pressure, vibrations)

_

Meissner’s corpuscle — senses touch

Pacinian corpuscle — sense pressure

nociceptor — senses pain

thermoreceptor — senses temp (heat or cold)

.

^^ all located w/in the dermis AND produce receptor potentials

a neuron’s decision to fire or not is determined by the SPATIAL and TEMPORAL summation of __ __ potentials at the (1)

• def. the 2 types of summations

_

t/f: inhibitory and excitatory pre- neurons (aka at different locations) that fire at the same time can cancel e/o out, and perhaps cause hyper-

_

t/f: AP is propelled forward, not backwards, due to (serial activation of VGSCs and) the afterhyperpolarization

a neuron’s decision to fire or not is determined by the SPATIAL and TEMPORAL summation of graded, synaptic potentials at the AIS (axon initial segment)/axon hillock (which has a high density of VSSCs aka VGSCs & other proteins)

• temporal: 1 pre- neuron firing in close in time (aka same neuron at different times) → compound EPSP

• spatial: multiple pre- neurons at different locations firing simultaneously (aka same time at different locations) → larger peak EPSP

__

true (IPSPs can cancel out EPSPs to prevent firing)

_

true

the neuron doctrine raises a key Q:

how does the nerve impulse cross from a neuron to its target? (1)

• which is characterized by (3)

__

chemical synaptic transmission at NMJ shows that ACh mimics nerve stimulation

• is this correlation or causation

by chemical synaptic transmission, characterized by:

• synaptic delay

• one-way signaling

• depletion of vesicles/NTs

__

correlation; need more evidence to prove causation

what molecules block VG-K+ channels, VGSC inactivation gate, VGSCs (1 each)

• its effect on APs

t/f: ACh works even when APs are blocked by TTX, which shows causation that ACh is needed to activate the muscle

__

mEPPs demonstrate the quantal nature of NT release (meaning?)

dofetilide blocks VG-K+ ———→ prolonged AP

veratridine blocks VGSC inactivation gate ———→ prolonged AP

TTX (tetrodotoxin) blocks VGSC ———→ no APs

• by binding to VGSC pore so that no Na+ can go into the post-, so no APs BUT there can still be depolarization

• (small molecule derived from puffer fish)

__

true

• b/c ACh still binds to ACh receptors on the post- and can still cause dep-

__

NTs are released in discrete packets aka quanta (shown w/ mEPPs)

(the amplitude of a mEPP determines the size of ONE quanta, in which the # of vesicles releasing NTs occur in this discrete quanta)

what is the key trigger that signals the vesicles to fuse w/ the plasma membrane? (1)

• where are its channels located? why?

___

def. the SNARE complex

• name SNARE proteins in vesicle membrane (~1/2) vs. plasma membrane (2)

name the 4 protein/parts of synaptic vesicles

Ca2+ influx (via VSCCs aka VG-Ca2+ channels ← which have multiple pore-forming & accessory subunits)

• VSCCs are clustered next to the docked vesicles at the “active zone” (aka clustered closer to the synapse)

  • b/c for fast NT release by the AP (aka once the AP reaches the pre- terminal)

___

SNARE complex — regulates fusion b/w the vesicle membrane & plasma membrane, that will form a fusion pore when fused into a single, fused membrane

-vesicle membrane:

• synaptobrevin (VAMP)

• synaptotagmin

-plasma membrane:

• SNAP-25

• syntaxin

_

synaptic vesicles consist of:

• synaptotagmin

• synaptobrevin

• V-ATPase

• vesicular NT transporter

state steps of (chemical) synaptic transmission (~6/7)

• AP reaches axon terminal

• VSCCs open

• Ca2+ influx causes vesicles to release NTs into synapse / exocytosis

• NTs cross the synapse

• NTs bind to neuroreceptors on post-

• triggers signal in post- (aka evoked post- current / EPSC)

  • (summation of EPSCs can trigger a post- AP)

what would happen to synaptic transmission if proteins of the SNARE complex were disabled? (1 w/ 4)

__

effect of botulinum (botox) and tetanus toxins on the SNARE complex?

• which toxins act on which SNARE complex proteins?

NS disorders, like:

• Alzheimer’s

• schizophrenia

• depression

• ADHD

__

botulinum/botox & tetanus toxins cleave the SNARE complex proteins (synaptobrevin/VAMP, SNAP-25, syntaxin), which prevent vesicle-membrane fusion SO no NT release (like no ACh release into NMJ)

• BoNT A,C,E — SNAP-25

• BoNT B,D,F,G — synaptobrevin

• BoNT C — syntaxin

fast neurotransmission w/ ionotropic Rs vs. slow neurotransmission w/ metabotropic Rs (2 each w/ time)

__

ligand-gated ion channels can be __ or __, depending on if they de- or hyper- the post- cell SO post- potentials are either that or that

• describe EPSP vs. IPSP (← involves NTs & NT binding open “-” channels)

  • for EPSP, which NT is in CNS vs. PNS

_

what deter. if it is fast or slow neurotransmission?

fast neurotransmission w/ ionotropic Rs ← ~1 ms

• involves ligand-gated ion channels

• NT binds → channel opens → ions flow across membrane

slow neurotransmission w/ metabotropic Rs

• involves G-protein-coupled Rs ← ~10-10,000 ms

• NT binds to GPCR → activates G-protein → subunits / intra- messengers indirectly modulate ion channels (→ ion channel opens → ions flow across membrane)

__

either excitatory (de-, EPSPs) or inhibitory (hyper-, IPSPs)

• EPSP

  • by glutamine (CNS) or ACh (PNS)

  • NT binding opens cation channels (Na+, K+, Ca2+ channels)

• IPSP

  • by GABA or glycine

  • NT binding opens anion channels (Cl- channels)

__

the receptor type (not the NT) deter. if it’s fast or slow neurotransmission

name NTs that act fast (ion-) vs. slow (metabo-) (4 each)

_

t/f: some NTs can operate in both fast and slow neurotransmission

• name them (5)

• which NT mediates only fast neurotransmission (1)

fast:

• ACh

• glutamate

• GABA

• glycine

slow ← neuromodulators

• dopamine (DA)

• norepinephrine (NE)

• serotonin

• neuropeptides

__

true

• ACh, glutamate, GABA, serotonin, ATP (← not glycine) can act in either iono- or metabo- neurotransmission

• glycine mediate only fast neurotransmission

name 3 sub-classes of glutamate Rs

• what do NMDARs require to bind to it? (2)

• what are NMDARs blocked by? (~1)

• what 2 enzymes are involved with mGluRs?

__

why does opening of glutamate R channels cause de- if both Na+ and K+ enter the cell?

__

where does glutamate neurotransmission in mammalian brain most often occur at?

• t/f: once formed, dendritic spines are morphologically dynamic

• t/f: abnormal dendritic spines are observed in neurodevelopmental disorders & are lost early in many neurodegenerative diseases

• AMDARs / kainate Rs (aka non-NMDA receptors)

• NMDARs ← w/ Mg2+ block

  • require glycine co-agonist (glycine & glutamate have to bind to NMDAR to open the ligand-gated ion channel pore)

  • is blocked by PCP (a psychoactive drug)

• mGluRs

  • involves AC (adenylyl cyclase) & PLC

__

b/c concentration gradient for Na+ is much greater than that for K+ (aka the greater Na+ driving force)

__

glutamate neurotransmission in mammalian brain most often occurs at dendritic spines

• aka dendritic spines often receive excitatory signals from glutamate

^ dendritic spines have thin neck & bulbous head, where glutamate synapses form at

_

true

true

def. connectome

_

name & describe 3 types of dye that help visualize neurons (3/4, 4, 3)

connectome: a complete map of all the connections/synapses in a neural circuit

• ^ is not limited to connections b/w neurons

__

Golgi stain

• the first technique to view neurons

• fixed/dead tissue is submerged in potassium dichromate & then silver nitrate

• seen as black

• labels only 1% of neurons

_

Nissl stain

• labels RNA in soma (mostly labels RNA in the rough ER)

• the dye is “+” & binds to “-” charged structures, like RNA

• labels most or all cells

• helps view cell densities and boundaries of brain areas

_

DAPI

• the dye binds to DNA

• labels nuclei

• helps view cell densities and boundaries of brain areas

describe direct vs. indirect immunofluorescence assay (2 each)

__

said don’t have to memorize the below

given the proteins/markers, what type of cells do they label?

• parvalbumin

• CamKII

• GAD

• GFAP

• NeuN

• c-fos

direct

• uses 1 antibody (labeled primary)

• is faster BUT more expensive & lower sensitivity

indirect

• uses 2 antibodies (unlabeled primary & labeled secondary)

• is more common & has higher sensitivity & is cheaper BUT slower

__

• parvalbumin — PV inhibitory neurons

• CamKII — pyramidal cells of sensory cortex

• GAD — GABA expressing neurons (“capital G word”)

• GFAP — astrocytes

• NeuN — neurons

• c-fos — active neurons

describe anterograde vs. retrograde tracing (2 each) AND 1 for both

• it travels along __

---

just be familiar w/ the names of these:

antero- tracers

• lectin peptides - uses PHA-L

  • (“LP” - “PL”)

• WGA (wheat germ agglutinin) - can cross synapses

retro- tracers

• CTB (choleratoxin B) - labels peptides

• fluorogold - seen as green fluorescence

• retrobeads - enter synapse via vesicle reuptake & then move to soma

anterograde tracing — identify where axons project to

(aka the post- of this neuron)

• tracer into soma & moves along the axon to the distal region/terminal

• labels the axon + terminal

retrograde tracing — identify the neurons that give input to this cell

(aka the pre- of this neuron)

• tracer into terminal or fiber tract & moves to soma

• labels the soma

^^ both require waiting ~5 days for the results

_

it travels along microtubules (used for long-distance transport)

def. promoter

• describe (2)

_

name & def. 2 examples of reporter genes (that track gene expression)

• describe result of cases where:

  • reporter is inserted downstream of the gene

  • reporter is inserted downstream of promoter/replacing the gene

is a sequence of DNA needed to either turn a gene on or off

• transcription starts at the promoter

• the promoter has a binding site for the enzyme that makes mRNA

__

reporter genes

• GFP (green fluorescent protein)

• LacZ (identify enzymes w/ different colors)

_

if reporter is inserted downstream of the gene:

• the reporter is also made whenever the gene is expressed

if reporter is inserted downstream of promoter/replacing the gene:

• the promoter only expresses the reporter

def. Cre-loxP system

• def. Cre

• 2 functions of this system (1 of them more than the other)

is a conditional gene expression system (aka can control gene expression)

• Cre — a recombinase enzyme that recombines DNA at specific LoxP sequences

_

functions:

• mainly used for reporter expression (aka where the reporter gene is expressed as a result)

• also used to delete a gene

def. Cre-ER system

• describe (2)

is an inducible gene expression system (aka gene expression changes depending on the conditions of place, time, type of stimulus, etc.)

• Cre fused w/ an estrogen receptor (ER) (aka Cre-ER) WITHOUT tamoxifen ligand will transport the complex outside the nucleus — INACTIVE (so no gene expression)

• Cre-ER with bound tamoxifen will transport the complex into the nucleus → to become ACTIVE (so induce gene expression)

for tetracycline inducible system

def. tTA

• function (1)

what happens if tetracycline or doxicycline is present

tTA — a yeast transcription factor (aka yeast TF)

• binds to the TRE sequence to either turn on or off downstream gene expression

_

if tetracycline or doxicycline is present, then gene expression is blocked (SO tetracycline is NOT expressed)

(don’t think about v.v.)

using synaptophysin (vesicle protein) & GFP together lets you view what?

• is it antero- or retro- tracing

allows you to see the axon terminals, but not the axons

• is anterograde tracing

rabies travel antero- or retrogradely?

modified rabies can only jump __ synapse (aka used for __ __ grade tracing)

what does using modified rabies allow you to view?

rabies travel retrogradely

modified rabies can only jump ONE synapse (monosynaptic retrograde tracing)

used to view neurons that are synaptically connected to a specific neuron

• (aka view the pre- neurons in green that are synaptically connected to the starter cell in red)

calcium imaging is a method to measure/record neuronal activity ← describe (1)

calcium imaging

• when neurons fire APs, Ca2+ influx is detected by GCaMP (a fluorescent Ca2+ sensor)

2 ways to manipulate brain activity in order to test for CAUSALITY b/w brain activity and function ← name & def.

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for classic approaches

• name 2 ways to silence brain areas (LoF)

• name 1 way to activate brain areas (GoF)

^ what’s the problem with classic approaches?

SO what do we use instead? (1 w/ 2)

• loss of function — take something away in order to see if it’s required for something to work

  • deter. if it is required aka NECESSARY

• gain of function — add something in to see if it causes some effect

  • deter. if it is able to cause an effect aka if it’s SUFFICIENT

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classic approaches have little specificity

silence brain areas w/:

• lesions (through chemical, electrical, or surgical removal)

• drugs

  • (muscimol, GABA_A agonists — inhibit neurons)

  • (NBQX glutamate antagonists — block excitation)

activate brain areas w/:

• electrical stimulation

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SO use modern approaches of chemogenetics and optogenetics

def. optogenetics

• describe (2)

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describe the TMS method (transcranial magnetic stimulation) (3) ← is neither opto- or chemogenetics

opto-: manipulate neuronal activity w/ light

• by activating w/ Channel Rhodopsin (ChR2) → dep-

• by silencing w/ Halo Rhodopsin (eNpHR) → hyper-

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TMS

• uses a magnetic field to cause current flow in target brain areas

• either activate w/ brief pulses OR inactivate w/ high frequency pulses

• lacks specific cell-type manipulation, SO instead acts broadly/over a large area of different cell types

(picture is of TMS)

summary

name & def. 3 types of experiments to test if a mechanism is BOTH “necessary” and “sufficient”

^ for 1 of the above, name 2 general ways to test if something is required/necessary OR able/sufficient through manipulation of brain area(s) (← aka 1 each)

test if BOTH necessary AND sufficient w/:

• anatomy: antero- and retrograde tracers

• functional activity: recording neural activity

• manipulation: turning on and off activity in specific neurons to test causality via Loss of Function & Gain of Function

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silence it to test if required/necessary for something to work

activate it to test if able/sufficient to cause a specific effect

def. neural plasticity / neuroplasticity

• explains __ and __

• also explains __ __ after brain damage

• caused from/results from interactions b/w (2 aka 2)

__

name 4 key features that a learning mechanism must be/have

are long-lasting/long-term changes to the brain throughout a person’s life (i.e. during development and into adulthood)

• explains learning & memory

• explain cortical remapping after brain damage

• caused from interactions b/w genes & environment (aka nature & nurture)

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a learning mechanism must be/show:

• long-lasting

• caused by brief events

  • (aka able to encode something very quickly)

  • (brief events mean short/brief, high frequency bursts) ← tetanic stimulation

• have synapse specificity

• have associativity

  • (aka able to associate b/w 2 or more different events)

name the 2 different types of learning (1 of them has 2) & def. each

• also name 2 types of non-associative learning

• give ex. of associative learning

^ what 1 is hippocampus-dependent, what 1 isn’t

• declarative (memory for facts)

• procedural (memory for habits, skills, motor responses)

  • non-associative (change in response that occurs over time)

    • habituation — decreased response w/ repetitive stim.

    • sensitization — increased response w/ repetitive stim.

  • associative (associations form b/w 2 events)

    • ex: classical conditioning

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declarative is hippocampus-dependent

procedural is NOT hippocampal-dependent

name & describe the pathway of this major hippocampal circuit

• all the synapses use __ as their NT

^ this is a type of __ excitation

^^ DRAW THIS MAJOR HIPPOCAMPAL CIRCUIT

__

electrophysiological studies of rodent hippocampus led to discovery of __ (def. term)

• we observed extra- _PSP

• describe the simple vs. complex setup used in hippocampal recording to study LTP

trisynaptic prime circuit (all 3 synapses use glutamate as their NT)

• perforant path (from the entorhinal cortex) → dentate gyrus → CA3 pyramidal cell → CA1 pyramidal cell

^ is a type of feedforward excitation (can refer to a previous flashcard if needed for picture)

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discovery of LTP (long-term potentiation) — is enhancement/increase of the post- response ← cellular and molecular mechanism for learning & memory

• observed extra- EPSP (b/c all 3 synapses release & use glutamate)

• simple setup: 1 stimulating & 1 recording electrode

• complex setup: 2 stimulators/stim. electrodes AND take both intra- & extra- recordings

def. tetanus

• can a tetanus induce a LTP/enhancement of the post- response?

(what is fEPSP?)

tetanus — a brief, high frequency (tetanic) stimulation

• yes, a tetanus can induce a LTP/enhancement of the post- response

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fEPSP is a field EPSP (aka collective synaptic strength of multiple neurons)

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(arrows point to where tetanus occurs)

diff. b/w stable & unstable potentiation

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brief sleep deprivation will impair the maintenance/stability of (1) in the hippocampal __ region

stable potentiation is long-lasting (LTP)

unstable potentiation is short-term/lasting potentiation

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brief sleep deprivation will impair the maintenance/stability of cAMP-PKA signaling-depending LTP in the hippocampal CA1 region

for LTP at the CA3-CA1 synapse via (two) Schaeffer collateral axons

describe the experiment that observes LTP in CA1 hippocampal neurons if one stimulus on each of the Schaeffer collateral axons (← 1 w/ 2)

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what is the EPSP amplitude?

you apply a stimulus to both axons, but one has tetanic stimulation (brief, high frequency stim.) while the other is the control

• want to see if the pathway w/ tetanic stim. on CA3 induces a LTP on CA1 (seen if that pathway’s response increases)

• if the control pathway doesn’t change, then the LTP is input-specific

  • (aka ONLY the tetanized pathway shows enhancement/increased response)

  • (aka strong stimulation is specific to that synapse/pathway)

__

EPSP amplitude is usually the slope of the EPSP

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(picture shows pathway 1 w/ tetanic stim. & pathway 2 as control)

• tetanized of ~100 Hz (aka activation pulses per sec.)

pathway 1 has time to recover b/w stimuli SO no habituation occurs

def. synapse specificity/input-specificity & associativity of LTP

_

what are the coincidence detection conditions needed for LTP?

what is the coincidence detectors?

specificity:

• only the synapses that get the tetanized activation get potentiated/strengthened

  • (independent from e/o)

associativity:

• when a weak stimulus is paired w/ a strong one (tetanic stim.), then BOTH synapses gets potentiated/strengthened

^^ doesn’t matter which pathway has which type of stim. b/c the concept still applies

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LTP only occurs if there is simultaneous pairing/coincidence of pre- glutamate release & post- depolarization

• coincidence detectors are NMDARs (meaning that NMDARs only open when both conditions are met simultaneously)

def. Hebb’s postulate

• what is Hebbian’s rule of plasticity

__

pre- release of glutamate binds to what? post- dep- is driven by what?

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explain the voltage “gate” of NMDARs

__

what happens if:

• only glutamate binds to NMDAR

• there’s both post- dep- from Na+ influx through AMPARs & glutamate bound to NMDARs

learning occurs when pre- activity is paired with post- activity

• rule: neurons that fire together, wire together

  • “wire together” means strengthened association/synapse OR grows more connections/synapses

^ ALSO “out of sync, fail to link”)

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pre- glutamate release, where glutamate binds to the NMDAR ligand binding site

AND

post- dep- caused by AMPARs’ Na+ influx

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voltage “gate” is due to the voltage-dependent Mg2+ block of NMDARs

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if only glutamate binds to NMDAR:

• then only Na+ influx (monovalent cations)

if both post- dep- from Na+ influx through AMPARs & glutamate bound to NMDARs:

• then Mg2+ block is removed → allow for BOTH Na+ and Ca2+ influx (divalent cations)

do dendritic spines grow or shrink when there is synapse strengthening vs. weakening? (← aka match them)

__

synapse strengthening during LTP (and morphological plasticity of spines) depends on __ __ cytoskeleton

• what do substances that block this "- -” cytoskeleton do?

dendritic spines:

• grow during synapse strengthening (LTP)

• shrink during synapse weakening (LTD)

^ identify by comparing the size (expansion/shrinking) and/or # of dendritic spines (new or no new spines)

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synapse strengthening during LTP (and morphological plasticity of spines) depends on dynamic actin cytoskeleton

• pharmalogically blocking actin filament dynamics cause LTP to be unstable

  • (aka still have LTP, but it in unstable / fades off more quickly ← b/c unstable is short-term potentiation)

name the 2 key features of NMDARs

• for NMDARs, what do you need to induce LTP? (1)

• blocked by Mg2+ ion, unless post- membrane dep-

• is Ca2+ (and Na+ and K+) permeable

_

CANNOT cause LTP w/o post- Ca2+ influx (aka NMDARs need Ca2+ influx in order to induce LTP

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(picture shows that the post- neuron is affected specifically at its dendritic spines)

describe the steps/cascade of molecular mechanisms that induce & maintain synapse strengthening (5)

• NMDARs allow Ca2+ influx

• activates calcium-dependent protein kinases: PKC & CaMKII

• inserts more AMPARs into the post- membrane

  • aka exocytosis of AMPARs from endosome’s reserve pool

• subsequent pre- glutamate release induces a stronger post- response (LTP)

  • b/c have stronger post- dep- due to more AMPARs in post- membrane

• potentiation of synapse strength is converted to a long-lasting form (days or more) via changes in gene expression (which is mediated by TFs, like CREB)

describe the 1 piece of evidence that support the idea that NMDARs are necessary for LTP

__

explain this:

initial activation of AMPAR can provide enough dep- to allow NMDAR to become activated quickly

_

what happens if the synapse has AMPAR, but no NMDAR?

• silencing (aka removal) of NMDARs prevents LTP induction

__

it means that AMPAR provide small depolarization (from Na+ influx) that is strong enough to remove the NMDAR Mg2+ block, SO if there’s pre- glutamate release, then NMDAR can immediately activate

_

if synapse has AMPAR but no NMDAR, then post- still depolarizes BUT no Ca2+ influx → so no LTP is induced

LTD (long-term depression) in hippocampal CA1 is caused from activation of __ __ AND removal of __ (__)

LTD is caused by __ frequency stimulation

LTD (long-term depression) in hippocampal CA1 is caused from activation of protein phosphatases AND removal of AMPARs (endocytosis)

LTD is caused by LOW FREQUENCY STIMULATION

for CORRELATION studies b/w LTP and memory

explain the Morris water maze experiment

conclusion?

used to test the memory of rats on where the hidden platform is (doesn’t like being wet)

• control rat: finds the hidden platform

• hippocampal-lesioned rat: has difficulty in finding the platform

also tests if control w/ NMDAR vs. AP5 that blocks NMDARs (which are important for LTP learning and memory) will affect performance

• control spends most time in the quadrant w/ the platform

• AP5 spends about the same amount of time in each quadrant (AP5 is a NMDA antagonist)

_

since NMDAR are necessary for LTP, then memory should be impaired if NMDAR are not functional

• so control group should take less time to find the platform compared to the NMDAR knockout group

is the fact that “activated calcium-dependent protein kinases are necessary for LTP” correlational or causation? why?

• give example relating to the Morris water maze experiment

more correlational than causal

• b/c protein kinases are active when LTP is induced, BUT this fact alone does NOT prove that active kinases induce LTP

ex: CaMKII mutant group spends more time to find the platform than the control group