neuro midterm

Neuron doctrine

Neuron doctrine

• developed by Ramon y Cajal

• the brain is made of separate neurons and other cells that are independent structurally and functionally

• info is transmitted through gaps/synapses

Golgi stain

stain used to study brain cells that specifically takes neurons but not all neurons take it

Nissl stain

stain used to study brain anatomy that stains whole cells and is not limited to neurons

neurons

make up 10% of cells in the brain and function in computation

glia

• make up 90% of cells in brain function in support

• provide nutrients to neurons and regulate/buffer extra cell space

• structural framework for other type of cell in the brain

• make myelin

• guide other cells during development

• capable of regeneration at high rate

schwann cell

• type of glial cell

• make myelin in the PNS (peripheral nervous system) (travels through entire body)

• found in axon

oligodendrocyte

• type of glial cell

• make myelin in CNS (brain and spinal cord) (central nervous system)

• connects to myelinated portion of axons

astrocyte

• type of glial cell

• regulate extracellular space and blood/brain barrier (system the protects / keeps things out of the brain)

microglia

• type of glial cell

• phagocytose

• removes/ engulfs debris and dying/dead nerons

synapse

• where neurons connect to communicate

synaptic vesicles

contain chemicals that can be released into the synapse

axon

• sends info to other neurons

• has myelinated portions (w nodes of Ranvier)

• inside is negative with respect to the outside

• can be recorded from

• where voltage - gated ion channels are found

• AP’s move down it

resting membrane potential

• difference in charge between inside and outside of cell

• Vm

• uses Goldman equation to be calculated

  • takes into account that membrane is permeable to more than one ion

depolarization

• membrane potential becomes closer to zero

cathodes

attract cations (-) are positive

anodes

attract cations (+) are negative

electrical current

• the movement of a positive charge

• determined by voltage and electrical conductance

  • driving force + conductance

• when positive + there is movement out of the cell

• when negative - there is movement into the cell

Equilibrium potential

• when the force of diffusion = electrical force

• Eion

• unique to each ion

• Nernst equation used to determine its value

-80mV

equilibrium potential (Eion) of potassium K+

62mV

equilibrium potential (Eion) of sodium Na+

driving force

• net available force available to move across the membrane

• 0 when the equilibrium potential is 0

capacitor

• planes that separate negative and positive charges

• ex. membrane

action potential

• can be generated by

  • injecting + current

  • synaptic activity that releases transmitter that activates chemically activated channels

threshold

• value of membrane potential that elicits an action potential

step 1

Na+ channels open Na+ rushes in

step 2

• depolarization/rising phase

• K+ channels open, K begins to leave the cell

• gNa > gK

step 3

• Na channels inactivate

• Na influx stops

step 4

• K continues to leave the cell

• causes membrane potential to return to resting potential

step 5

• after falling phase

  • where gNa < gK

• K channels close

• Na channels deinactivate

step 6

• undershoot

  • hyperpolarization

• under membrane potential

sodium potassium pump

• maintain sodium/potassium gradient

• kicks out 3 Na+, brings in 2 K+

• brain used 70% ATP with these

absolute refractory period

• period after AP where it is impossible to shoot another AP

• this happens because of inactivation of sodium gated ion channels after AP

• 1-2 ms

• during peak and downfall

relative refractory period

• period of time after an AP where another AP can be fired

• second initiation requires stronger stimulus than before

  • needed to reopen inactivated sodium channels

• right after other type of refractory period

• during undershoot/hyperpolarization

neurogenesis

• stem cells residing in the adult brain divide and differentiate into neurons

tetrodotoxin

• TX

• binds and blocks Na+ channels which can block AP’s (chart would be little bump but no AP)

• makes eating pufferfish wrong lethal

• fast acting poison, no antidote

internal resistance

• ri

• current that flows along the axon

membrane resistance

• rm

• how easily current flows in and out of the membrane

saltatory conduction

• involved in passive propagation

• when current flows from node to node in the myelinated portion of the axon

  • AP’s happen in this node

active propagation

• how AP’s move down the axon

• unmyelinated portion

• slower due to constant firing of AP’s

passive propagation

• how currents AP’s move down the axon

• myelinated portion of the axon

• faster because AP’s happen at nodes

  • saltatory conduction

gap junction

• electrical synapses

• ions flow from cell to cell

chemical synapse

• uses vesicles to release NT’s through a complex system

pre synaptic

1. vesicles store NT

2. AP arrives at terminal button

3. Voltage gated Ca++ channels open

4. Ca++ enters terminal

5. Vesicles fuse with membrane

6. exocytosis

post synaptic

• ions flow in and out

transmitter gated ion channel receptors

• elicit EPSP’s

• ionotropic receptors

• bind to receptors that open Na+ channels

  • not voltage gated

• hyperpolarizes when it elicits and IPSP

G protein coupled receptors

• metabotropic receptors

• can open ion channels

• can activate second messengers

spatial summation

records multiple axons and adds EPSP’s

temporal summation

records multiple AP’s on the same axon and adds EPSP’s

animal research

• good model for behaviors in humans

• controllable conditions

• organizational similarities in brain structures

• simpler and easier to focus on certain aspects of neural behavior

scientific laws

• fact of the physical universe

• exist until disproven

theory

• explanation that is broad in scope and supported by evidence

• can include laws

hypothesis

• proposed explanation from an observed phenomenon

• testable and falsifiable

negative control

group in an experiment where no effect is found from a given placebo

positive control

group in an experiment where an effect is expected from a known substance

lesions

• when a part of the brain is taken out/destroyed to learn its effects

• ablation - destruction

• one technique used to do this is lasers (RF) that can cause electrical destruction of certain parts of the brain

• Pros: Provides strong evidence for the necessity of a brain structure for a process

• Cons: does not actually investigate the function of the brain region, just what everything else can do without it

intraperitoneal

• ip

• drugs administered through the abdominal cavity

subcutaneous

• sc

• drugs administered under the skin

intravenous

• iv

• drugs administered into vein

intracerebral

• ic

• drugs administered into brain tissue

intracerebroventricular

• icv

• drugs administered into the ventricle

implant

• drugs administered by something placed into skin/ body

transdermal

• drugs administered through the skin

• ex. nicotine or testosterone patch

oral

• drugs administered through the mouth

  • ex. pills

stereotaxic surgery

• uses a stereotaxic atlas to input certain coordinates on the brain and target certain areas using electrodes

  • stereotaxic apparatus - used to place electrodes into brain

  • bregma - juncture of coronal and sagittal suture (point 0)

  • cannula - rods placed into brain (cannot be felt by patient)

• pros:

• cons:

electrophysiology

• measures brain activity in animals using electrodes

  • macroelectrodes - records many neurons

  • microelectrodes- records only one neuron

• pros:

• cons:

immediate early genes

• uses antibodies to label proteins in the brain in response to stimuli

• c-fos

• pros:

• cons:

MRI

• snapshot of the brain at a certain point in time

• pros: noninvasive can be used on humans

• cons: only gives a snapshot of the brain and doesn’t study brain activity

EEG

• electroencephalogram

• measures real time brain activity

• macroelectrodes on the skull

• pros: real time measurements, very mobile

• cons: restricted to outermost layer of the cortex

FMRI

• looks for increase in blood oxygen level to study brain function

• pros: can look at entire brain, non invasive

• cons: complete immobilization and delay

in situ hybridization

• used to detect MRNA at a cellular level one gene at a time

• brain section exposed to radioactively labeled RNA probe

• pros: cellular resolution

• cons: time consuming, one gene at a time

siRNA

• Create a piece of RNA and inject it into the brain; the siRNA recognizes the strand of mRNA of interest, and destroys it such that it cannot be translated for protein expression

• cons: potential off-target effects

microarrays

• grind up tissue; extract RNA; reverse transcribe to become DNA; fluorescently label; add to microarray chip; DNA binds to complementary strand on chip; ratio of different samples shows ratio of gene expression

• pros: can assay of 1000’s of genes

• cons: no cellular resolution, expensive

imunocytochemistry

• studying cellular proteins

• in tissue slices, antibodies recognize the protein they are targeted against; label fluorescently to see under confocal

• pros: cellular resolution, double label proteins

• cons: time consuming, not as quantitative

ligands

activate receptors

agonists

drug that activated receptors

antagonists

drug that blocks receptors

knock out mice

• removes a gene to be studied

• Knockout the gene in the mice embryo; no mRNA and therefore no protein products are made from

• cons: May Interacts with other processes we want to control for

conditional knock outs

• specific times (age) and specific tissue (area) where gene is knocked out

• pros: doesn’t disrupt as much the developmental process

optogenetics

• uses light to activate/ inhibit neurons

• Use virus to inject a channel (eg. Rhodopsin 2/halorhodopsin); simulate with blue/yellow light to activate/inhibit neurons via ion flow

• pros: Allows for bidirectional control of the neural activities simultaneously / allows for real-time investigation of function of neurons in behavior

twin studies

• monozygotic - same egg (identical)

• dizygotic - (fraternal)

• concordant - when both twins have the same disorder

• used to study genetic effect on certain diseases

• pros: Allows for the disentanglement of shared genetic and environmental factors for the trait of interest

• cons: many confounding variables

adoption studies

• used to study the effect of environmental factors

• pros: Allows for the disentanglement of shared genetic and environmental factors for the trait of interest

• cons: information about biological parents isn’t always available

neurotransmitter

• localized in neurons

• synthesized by neurons

• released by neurons

acetylcholine

• NT of neuromuscular junctions

• motor neuron synapses

• Ach

ach agonists

• physostigmine

• black widow spider venom

ach antagonists

• botulinum toxin

• myasthenia gravis

dopamine

• NT that assists in movement, attention, learning, addiction, and reward

• cocaine is an agonist

• methylphenyl (Ritalin) is an agonist

• chlorpromazine is an antagonist

• amphetamine both increases activity and release of this NT

catecholamines

• type of NT

  • dopamine (DA)

  • norepinephrine (NE) - assists in attention

  • epinephrine (Epi) - adrenaline

• bind to alpha and beta renergic receptors

indolamides

• serotonin (5-HT)

serotonin

• NT involved in mood, eating, sleeping, and arousal

• antagonist is fluoxetine (Prozac)

• agonists: LSD, Ecstasy/Molly (stimulates release, inhibits uptake), Psilocybin (mushrooms) >> Psilocin (binds to receptors

amino acid neurotransmitters

• small

• allylglycine

  • inactivates GAD

  • used to make experimental animal models for epilepsy

• Glutamate - often excitatory

• GABA (gamma-aminobutyric acid) - often inhibitory

Neuropeptides

• bind to opioid receptors: opium, morphine, heroin

• endogenous opioids

  • enkephalins (involved in reward pathway and pain reduction [analgesia])

reward pathway

• projection of (in this case) dopamine neurons from VTA to NA