lecture 5-10

Neuroimaging structural

CT, MRI, DTI

Neuroimaging: Functional

EEG, MEG, PET, fMRI

CT/CAT scan (structural) mechanism

\-3D x-rays @ diff angles

\-detect diff tissue density; bone-white; csf-dark

CT/CAT scan (structural) advantages

fast, not expensive

CT/CAT scan (structural) disadvantages

radiation, can't do too much

CT/CAT scan (structural) uses

diagnose: stroke, tumor, lesions, vascular malformations

MRI (magnetic resonance imaging), structural mechanism

1) radio frequency electromagnetic pulse knocks proton out of alignment

2) rate of proton in phase & realignment w/ one another make energy signal

\-rate depends on tissue (cerebral spinal fluid, white or gray matter)=diff realign=diff signal machine detects

MRI (magnetic resonance imaging), structural advantages

good spatial resolution, no radiation, differentiates tissues

MRI (magnetic resonance imaging), structural, disadvantages

expensive to use/run, no metal (pacemaker), longer than CT scan

MRI (magnetic resonance imaging), structural uses

detect tumor, bleeding degenerative diseases, evaluate treatment, guidance for neurosurgery

DTI (diffusion tensor imaging) structural mechanism

MRI technique detects flow of H20 along axon (like a straw); measure diffusion rate & direction

DTI (diffusion tensor imaging) structural advantages

high resolution & structural detail

DTI (diffusion tensor imaging) structural disadvantages

can't trace to or from of fibers that bond/intersect (about 75% lost)

DTI (diffusion tensor imaging) structural uses

observe white matter (axons)

EEG (EEG (electroencephalogram) mechanism

\-functional, direct

record electric energy (neuron fire) of brain from scalp, measures group of neurons firing

EEG (electroencephalogram) advantages

\-functional, direct

good temporal resolution (m/s), not invasive (no radiation), behavioral response unnecessary (can use on baby)

EEG (electroencephalogram) disadvantages

\-functional, direct

poor spatial resolution; only a general area

EEG (electroencephalogram) uses

\-functional, direct

research: event-related potential (ERP), time locked stimuli to measure brain response

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hospital diagnostics: seizure, stages of sleep & awake, stimuli response

MEG (magnetoencephalography) mechanism

\-functional direct

measure electrical activity from large group of neurons firing synchronously using a magnet

MEG (magnetoencephalography) advantages

\-functional direct

good temporal resolution (m/s), better spatial resolution than EEG, magnetic field less distorted than electric fields, combined w/ fMRI=>very strong localization

MEG (magnetoencephalography) disadvantages

\-functional direct

only surface image, can't have metal

MEG (magnetoencephalography) uses

\-functional direct

only research

PET (positron emission tomography) scan mechanism

\-functional indirect

radiotracer (radioactive form of glucose) injected into bloodstream, bind to target, accumulate @ highest target concentration, detector ring detects gamma rays radiotracer emits

PET (positron emission tomography) scan advantages

\-functional indirect

measure function, baseline (body function=blood flow, oxygen use)

PET (positron emission tomography) scan disadvantages

\-functional indirect

radiation=invasive, poor resolution, expensive

PET (positron emission tomography) scan uses

\-functional indirect

oncology, diagnose diffuse brain disease, research examining brain activity during tasks

fMRI (functional MRI) mechanism

\-functional indirect

measure BOLD (blood oxygenation level dependent), neural activity increases=increase blood oxygenate (blood flow)=increase MR signal

fMRI (functional MRI) advantages

\-functional indirect

no radiation, increase spatial resolution

fMRI (functional MRI) disadvantages

\-functional indirect

ethics; not used well (ex: no lie MRI)

fMRI (functional MRI) uses

\-functional indirect

neuropsychology

Define neurophysiology

the study of life processes w/in neurons

electric signal (neuron fire) communication w/in or between neuron?

w/in neuron

chemical signal (neurotransmitter) communication w/in or between neuron?

between neurons

Define ions, cations, and anions.

ions- two oppositely charged atoms

Cations- positive charged ions (+)

Anions- negatively charged ions (-)

cations in neurons

K+, Na+, Ca +2

anions in neurons

Cl-, anions (large neg proteins)

outside of neuron

positively charged

salty milk: Na+, Cl-, Ca 2+

inside of neuron

negatively charged

negative banana: K+, Al-

Cell membrane (plasma membrane)

phospholipid bilayer that surrounds all cells and regulates what enters and leaves the cell

\-semipermeable: hydrophobic & small uncharges polar molecules shall pass

plamsa membrane

outer wall of cell

Phospholipids

molecule that forms the bilayer of the cell's membranes

hydrophobic tail: water hater, nonpolar

hydrophilic head: water lover, polar

membrane potential (Vm)

diff in distribution of charged ions across cell membrane

\-2 passive & 1 active processes

membrane resting potential

\-50 to -80 mV

2 passive processes in membrane potential

1) concentration gradient

2) electrostatic force

1) concentration gradient

high to low concentration across membrane

2) electrostatic force

like charge repel & opposites attract

equilibrium potential

concentration gradient (K+ out) and electrostatic force (K+ in) balance/act against each other; -60mv K+

why is resting potential (between -50 & -80 mv) so similar to equilibrium potential for K+ (-60 mv)?

cuz cell membrane is mostly permeable to K+

active process for membrane potential is? & how?

energy dependent pump (sodium-potassium pump)

\-3Na+ out for every 2+ pumped in

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\-help distribution of ions (electrical chemical gradient) revert back to normal

action potential

the change in electrical potential associated with the passage of an impulse along the membrane of a muscle cell or nerve cell.

action potential steps

1 - Stimulus disturbs the plasma membrane

2 - Sodium Na+ channels open, allowing Na+ to flow into the cell, lessening the polarization/difference in charge at that location

3 - This change causes nearby voltage-gated sodium channels to open, allowing more Na+ to flow into cell

4 - That area of the inside of the cell is now slightly more positive, and the outside, slightly more negative

5 - This affects other nearby voltage-gated Na+ channels and depolarization moves down the membrane = action potential

6 - These channels close and voltage-gated potassium K+ channels open, potassium flows out of the cell repolarizing the membrane

7 - Sodium-potassium pumps then restore resting potential and reestablish proper concentrations of Na+ and K+

all-or-none property of action potentials

the neuron fires at full amplitude or not at all-does not reflect increased stimulus strength (no variation)

permeability changes

1) Na+ depolarize

2) K+ repolarize

depolarization (+) and repolarization (-)

For an action potential to occur, the neuron will first experience local __________ when sodium rushes into the cell, and then __________ as potassium leaves the cell and the impulse continues down the axon.

absolute refractory period

The minimum length of time after an action potential during which another action potential cannot begin, completely insensitive to further stimulation

relative refractory period

A period after firing when a neuron is returning to its normal polarized state and will fire again only if the incoming message is much stronger than usual; reduced sensitivity to further stimulation

1) electrotonic conduction

passive current flow through neurons that accompanies activated electrical currents, passive decays w/ time distance from initiation site (smaller over time)

2) active conduction

repeated renewal of a long-range electrical signal along the axon, action potential from axon hillock to axon terminal, not lessen over length of axon, opening Na+ voltage gate channels depolarizes

3) saltatory conduction

Potential moves from electric field to field between nodes of Ranvier

= much faster than as it doesn't require inducing changes all along, Na + currents faster & farther, need less regeneration

synaptic transmission

The relaying of information across the synapse by means of chemical neurotransmitters. presynaptic axon terminal to postsynaptic dendrites

synaptic transmission steps

1\. action potential arrives at the axon terminal

2\. voltage gated Ca 2+ channels open

3\. Ca 2+ enters the cell

4\. Ca 2+ signals to vesicles

5\. vesicles move to the membrane

6\. docked vesicles release neurotransmitter by exocytosis

7\. neurotransmitter diffuses across the synapse and binds to receptors

8) EPSP or IPSP

9) enzyme breaks down excess NT

10) reuptake & recycle of NT slows synaptic action

11) NT binds to autoreceptors of presynaptic membrane

12) spatial or temporal summation

excitatory postsynaptic potential (EPSP)

a slight graded depolarization of a postsynaptic cell, bringing the membrane potential of that cell closer to the threshold for an action potential (+, cations), slower than action potential

inhibitory postsynaptic potential (IPSP)

graded hyperpolarization (-, anion) of postsynaptic membrane, lowers probability of action potential firing, slower than action potential

spatial summation

The sum of multiple synapses firing at different locations at one time to create a net effect, input across space, closer=better

temporal summation

Summation by a postsynaptic cell of input (EPSPs or IPSPs) from a single source over time, input across time, time closer together=better

receptor & neurotransmitter is analogous to...

lock=receptor

neurotransmitter=key

ionotropic receptors

receptors that are coupled to ion channels and affect the neuron by causing those channels to open

\-mediate fast EPSP (cation, depolar), IPSP (anion, hyperpolar)

Acetylcholine

quaternary

\-found in basal forebrain

\-project to cortex, amygdala, hippocampus

Acetylcholine role

sleep, attention, learning and memory

Acetylcholine disease

Alzheimer's disease

Acetylcholine broken down by

acetylcholinesterase (AChe) very fast

acetylcholine receptors

nicotinic (ionotropic) and muscarinic (metabotropic)

Dopamine (monoamine)

1) mesostrial system

2) mesostriatial system

1) from substantia nigria (midbrain) to striatum (part of basal ganglia)

2) central tegmental (midbrain to limbic system & cortex

Dopamine role

1) mesostrial system

2) mesostriatial system

1) motor control

2) reward & pleasure

Dopamine disease

1) mesostrial system

2) mesostriatial system

1) Parkinson's disease

2) schizophrenia, addictive behaviors

Dopamine reuptake

1) mesostrial system

2) mesostriatial system

dopamine transporter (DA), slow

Dopamine broken down

1) mesostrial system

2) mesostriatial system

monoamine oxidase (MAG) target of antidepressants

Dopamine receptors

1) mesostrial system

2) mesostriatial system

D1 (excitatory) and D2 (inhibitory)

both metabotrophic & G-protein

Norepinephrine monoamine

project from locus coerolous (midbrain) & lateral tengmental (pons) to thalamus, amygdala, cortex, cerebellum

Norepinephrine role

sleep, stress, mood, alertness, sexual behavior

Norepinephrine disease

depression, ADHD

Norepinephrine reuptake

norepinephrine transporter (NET) slow

Norepinephrine broken down

monoamine oxidase (MAO)

Norepinephrine receptor

alpha , beta

\-metabotrophic, G protein

Serotonin (monoamine)

project from raphe nuclei (brainstem) to hippocampus, basal ganglia

Serotonin role

sleep and mood

Serotonin disease

also depression & ADHD

Serotonin reuptake

serotonin transporter (SERT)

Serotonin receptors

5-HT 1-7=metabotrophic, G-protein

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5-HT2=ionotrophic

Glutamate (amino acid)

The principal excitatory neurotransmitter in limbic, basal ganglia circuits

Glutamate role

learning and memory some level all behavior

Glutamate diseases

glutamate excitotoxicity, Alzehimer's disease, Mild Cognitive disease (MCI), Impairment Amyotrophic (ALS)

Glutamate reuptake

Glutamate Transporters (excitatory amino acid transporters - EAAT1-5)

fast astrocytes contribute, recycled into vesicles for later

Glutamate receptors

AMPA and NMDA (inotropic), memory formation

GABA (amino acid)

a major inhibitory neurotransmitter found throughout brain, predominantly interneurons

GABA role

involved in all behavior at some level

GABA disease

drug increase GABA to treat anxiety, epilepsy, stress

GABA reuptake

GABA transporters on astrocytes and neurons

\- GABA transporters (GAT)

\- recycling breakdown

GABA receptors

GABAa (ionotropic) and GABAb (metabotropic)

Neuropeptides: Opioid Peptides

endogenous peptides (made form body naturally)mimic opiate drugs such as morphine and reduce the perception of pain, anxiety