Neurophysiology Exam 1

Cytoarchitecture definition

How cells are arranged in tissues

Nissl stain characteristics

lacks true morphology

Golgi stain characteristics

Shows better morphology than golgi stain

uses a silver chromate solution

Reticular theory

the nervous system is a single continuous physical network rather than a collection of separate cells

Neuron doctrine

the nervous system is composed of discrete, individual cells rather than a continuous network

____ supported the reticular theory

____ supported the neuron doctrine

Golgi

Cajal

What is the MAP implicated in Alzheimer’s disease?

Tau

Tau role in Alzheimer’s

stabilizes cellular tracks called microtubules in healthy brain neurons, but it becomes hyperphosphorylated and forms toxic tangles in Alzheimer’s disease.

What technique was used to learn about Tau

Immunohistochemistry staining

Use primary antibody specific to target, then use secondary antibody specific to primary antibody

secondary antibody had a fluorescent tag

Axoplasmic transport

move molecules down the axon (usually proteins)

what specifically carries molecules down the axon?

motor proteins (require ATP)

Define anterograde transport

Transport from the soma → axon terminal

Define retrograde transport

Transport from the axon terminal → soma

What protein facilitates anterograde transport

kinesin

What protein facilitates retrograde transport

dynein

What methods are used to trace neuronal tracts in the brain?

anterograde + retrograde transport

Application of Horse Raddish Peroxidase (HRP)

selectively taken up by axon terminals and then transported retrogradely to the soma. A chemical reaction can then be initiated to visualize the location of the HRP in slices of brain tissue after the experimental animal is euthanized.

What happens if you kill neurons in the CNS?

they do not come back

Disruption of dendrite structure/function can lead to

mental disorders

dendrites in a healthy vs intellectually disabled patient differences

In intellectually disabled patients, the dendrites tend to be thinner and longer

Neurite definition

Projection coming off the soma (axons/dendrites)

Multipolar neuron def

multiple neurites coming off the soma

ex- motor neurons, interneurons

bipolar neuron def

two neurites coming off the soma

ex- visual system, audio system

pseudo-unipolar neuron def

one neurite splits into 2 right away

ex- general senses: touch, temp, etc

Golgi type 1 neurons

long axon length

go from one part of the brain to another

long-distance

Golgi type 2 neurons

short axon length

do not reach much beyond the vicinity of the cell body

short-distance

“local circuit neurons”

primary sensory neurons function

bring sensory information (from skin, eyes, ears, etc) into the CNS

Motor neurons function

connect with muscles and cause movement

interneurons function

neurons connecting with other neurons

(most of the neurons in the brain)

cholinergic def

neurons that release acetylcholine

glutamatergic def

neurons that release glutamate

glia main role

support cells for neurons

without glia, neurons would not function properly

Astrocytes features

most abundant glial cell

smaller than neurons

end feet

Astrocytes functions

fill in space between neurons

process of spatial buffering - controls chemical composition of CSF

myelinating glia

glial cells that produce myelin

myelin sheath

collection of myelin → collective larger structure that surrounds many axons

Oligodendrocytes main role

myelin in the CNS

Schwann cells main role

myelin in the PNS

Because neurons have high metabolic needs, neurons have many…

mitochondria

What cells produce CSF

Ependymal cells

What makes one cell different from another

The proteins expressed

Voltage (V) def

The difference in electrical potential between 2 spots

How is voltage created in cells?

The different ion concentrations inside vs outside the cell

What is the driving force for electrical current?

Voltage

Resistance (R) def

Relative inability of current to flow

Inverse of conductance

Rm =

resistance at membrane

Ri =

resistance inside the cell

Conductance (g) definition

Relative ability for current to flow

inverse of resistance

What does conductance rely on in the cell?

open and permeable ion channels

g and R relationship

g = 1/R

Current (I) def

The movement of a charged particle

current application in nervous system

focuses on the movement of ions

Ohm’s law

I = V/R

I = Vg

ion channel physical properties

4-6 subunits with a pore in the middle

subunit composition determines different/other properties

What is ion gating

ion channels open/close only under specific conditions

Mechanically gated ion channels open/close in response to…

a physical force

voltage gated ion channels open/close in response to…

changes in voltage

ligand gated ion channels open/close in response to…

ligand binding

leak channels definition

channels that are not gated and always open

all cells have

they determine the resting membrane potential

Vm rest is maintained when…

neurons are not firing action potentials

Vm sign and magnitude are critical for…

normal neuronal function

Vm rest normal value

-65 - -70 mV

equilibrium potential def

Voltage across the membrane where the concentration and electrical gradient are balanced

equilibrium potential sign

Eion

In what way do ions move

in such a way to make Vm=Eion

What does it mean if Vm = Eion

There will be no net movement of that ion at that point

The Nernst Equation limitations

1. membrane is permeable to more than one ion - equation only takes one ion into account

2. Ions have different relative permeabilities - ex membrane is ~40X more permeable to K+ than Na+

When do you use the Goldman equation?

To determine Vm rest

What two important factors does the Goldman equation take into account?

1. The ration of [ion]out and [ion]in

2. their different relative membrane permeabilities

Key determining factor for Vm

K+

K+ channel structure

4 subunits, barrel shape, pore loop

K+ channel describe the pore loop

aa that line the pore

shape creates a selectivity filter (K+ can pass thru, other ions can not)

Describe the disorder experienced by weaver mice

single aa mutation in pore loop of K+ channel in cerebellum → Channels are less specific to K+ → Na+ permeability in channel → Vm less negative → neuronal disfunction → neuronal death → abnormal movements, cannot maintain posture

Depolarization def

V becomes less negative

Hyperpolarization def

V becomes more negative

What happens to Vm when the concentration of K+ outside the cell increases

depolarizes

Where does the blood-brain barrier come from?

Astrocyte feet - surround capillaries in CNS so K+ can NOT cross BBB

Extracellular K+ concentration is…

tightly regulated

Extracellular K+ concentration will still rise during normal activity because…

Action Potentials put K+ outside neurons

What helps clear extracellular K+

astrocytes

Define K+ spatial buffering

astrocytes take up extra K+ and diffuse it away

How do neurons increase or decrease their action potential strength?

changing frequency and/or firing pattern

AP rising phase

Rapid membrane depolarization

AP resting phase

(-65) - (-70) mV

Peak value Vm

40 MV

AP Overshoot phase

Part of the AP where the inside of the neuron is positively charged w respect to the outside

AP falling phase → undershoot

rapid repolarization until inside of membrane is more negative than resting potential

Describe AP generation beginnings

initial depolarization arises different ways in different neurons

Activation of mechanically gated ion channels in the skin are activated by physical force

Electrophysiology def

The study of electrical properties of bio cells or tissues

Describe a typical electrophysiology experiment

stimulate a cell and record its response

What reflects stimulus magnitude

firing frequency

The AP firing rate increases as the depolarizing current…

increases

IDF =

V_m - E_ion

G-dom at rest

K+

G-dom during rising phase

Na+

g-dom in falling phase + undershoot

K+

Time of total AP

2 ms

Label

Time of absolute refractory period

1 ms

Relative refractory period time

½ ms