MULTIPOLAR CELLS

Purkinje Cells

pyramidal Cells

Cells with rich and extensive dendrite networks for "enormous" synaptic input.

1 axon, 1 apical dendrite

Oligodendrocytes - can form a myelin sheeths and support. Central Nervous system, turned on in the presence of astrocytes

Schwann Cells - is the myelin sheet. Peripheral Nervous system, turned on in the presence of axons

Astrocytes - blood-brain barrier, clean

miroglai - responsible for searching to clean

pressure on muscle -> singal down afferent fiber -> Dorsal Root ganglion -> spinal chord

-> muscle neuron

-> inhibitory neuron-> muscle neuron

->Medulla -> Thalamus -> Motor Cortex

Most of spinal pathway circuits

includes one or more interneurons

Hyperpolarization

Depolarization

Hyper = -65mV to -75mV or ihibitory

Depo = -65mV to -55mV or excitatory

Types of Signals

Receptor Potential

Synaptic Potential

Action Potential

Receptor Potential - local, small amplitude, 5-100ms, Graded release

Synaptic Potential - local, small amplitude, 5-20MIN, Graded release

Action Potential - Propagated, 70 - 110mV, 1-10ms, All or None = amount of release determined by freq.

 - AP triggered by sodium inflow in hillock where most Na channels are located and lowest threshold

recieving end is a muscle spindle sensitive to stretch

axon aka fermoral nerve

axon is 14-18um thick

myelin sheet is 10um thick

nodes of ranvier about .5um long

connects to DRG in lumbosacral region of spinal chord

Motor Neurons

2 types

located

# of denrties

cell body thickness

axon splits, thickness

 synaptic boutons

2 types one that innervate the same muscle as the sensory input and one that innervates coopertive muscles

located in anterior horn of spinal chord, leaves through ventral root

cell body 80um thick

has 7 - 18 dendrites that have extensive branching

avg dendrite length is 20 x cell body(80um)

axons split to from recurrent branches that innervate ihibitory neurons

axon is 20um thick

synaptic boutons - synaptic terminals on the hillock

synaptic boutons

sensory vs motor neuron

sensory - few, if any

motor- has tons, most located on denrties only 5% on cell body

When each motor branches onto a muscle losing its myelin sheeth and then makes contact with the muscle

transmitter is acetylcholine

70% lipid and 30% protein

concentric layers of lipid bilayers

for myelination

schwann cells form a trough in which the nerve lays

Schwan cell then surround the axon and forms a double membrane structure called the MESAXON whcih the elongates and forms a spiral layers around

the cytoplasm is squeezed out forming the lamellae which is a mature sheeth

 produces MAG for cell recognition

action potential voltage

ions per second

500 volts/s

100,000,000 ions/s

voltage gated

ligand gated (chemical)

mechanically gated (stretch)

*each channel is typically sensitive to only one type of stimulation

ions in solution

large vs. small

Large ions have more delocalized electric fields and smaller ions have less thus smaller ions are more attracted to water.

this slows them down because it acts bigger than it actually is due to attached water molecules

membrane spanning protein that is always every 3rd position on the alpha helix

positive charge

passive - requires no energy

-direction determined by electrostatic and diffusional force

cation-selective channels do not distinguish between cations +

anion-selective channels only Cl-

typical ion stays bound for 1 microsecond

gating

4-types

The conformational change on an ion channel

transmitter,phosphorylation,voltage gated, stretch of pressure gated

transmitter and voltage gated enter a refractory state.

trans = desensitization

a) inhibitorychemicals can block binding location

 volt = inactivation

 a) chnage in membrane potential

b) Ca2+ binding, when concentration in extracellular fluid is great enough, Ca2+ binds wth channel and deativates it

 c) dephosphorylation - Ca2+ binds with the phosphorous open the channel which then becomes closed and removed from channel

Voltage inside the cell (V_in) minus Voltage outside the cell (V_out)

note* current = net movement of positive charge

Electrotonic Potential

Threshold

Hyperpolarization (more negative) or depolarization (less negative) cell membrane change that don't elicit an active response

threshold = polarization that does active response

In: mostly K+ and organic anions

out: mostly Na+ and Cl-

Glial cells are only permiable to K+

K+ is in higher concentration inside the cell

K+ flows out of glial cell making outer surface of the membrane + charged which prevents more K+ from leaving

resting membrane pot of glial = -75mV

Na+ Resting Potential = +55mV

 K+ in cell causes the + charge out of cell and - charge in cell. Na+ flows in attempting to elminate - charge but since K+ channels out number Na+ channels thi does not happen because the depolarization causes K+ to flow out to keep inner membrane - and out membrane +.

*Cell wants inner bilayer - and out to be + so if Na+ is flowing in then K+ needs to flow out. Otherwise inner mem. becomes +

moves ions against gradient

 2 K+ in and 3 Na+ out

40 x 10^-9 S

40nS

RT * ln(K+out)

 ZF        (K+in)

R=gas constant

T=temperature

Z=Valence

F=Faradays constant

K+ out/in = concentrations

 *Cl- is in/out

*Note use this equation instead

58 log(out)

Z        (in)

Rin= Rm

         4Πr²

Rm=Membrane Resistance

*Cell with a higher Rin expirience a higher change in membrane voltage

ΔV=ΔQ/C

ΔV= Ic * Δt

       C

Ic= current flow

Neurofilaments,

microfilaments made of actin,

microtubules of of tubulin, act as railway

non-activated

Ramified

Actived

Hypertrophied

Amoeboid

Passive currents = flat or o response

•GFAP+(astromarker)

•Gap junctions•GPCRs(metabo.)

•“GluT”cells

•Stimulated by NT“spillover”

•Complex current curved

•NG2+(oligomarker)

•Not coupled•GPCRs(metabo.)

•“GluR”cells

•Form “ectopic”synapsesNow

Selectively permeable to K+

Rest near EK (-90 mV)

Role in K+buffering

Culture: Ca2+ indicator shows a release of Ca2+ by Astro causes the release in other Astro

Poke -> activates enzyme PLC -> Convets PP2 to IP3 -> IP3 binds to receptors in ER -> Ca2+ flood from ER into cytosol -> release glia transmitter ATP -> Binds to PY2 receptors on other Astro ->activates PLC

Slice Method: No Ca2+ release

Culture: Electically stimulated neuron -> stimulated astrocyte

Slice: Same

Stim neuron -> release glutamate -> binds to mGluR on astro processes -> Activates PLC

Culture: Poke Astrocyte -> Glumate current in neuron

Slice: No affect on neurons

gated by glutamate

NMDA Receptor

-permiable to Ca2+, K+, Na+

-Activated by Glu and NMDA

-Blocked by D-APV, Mg2+, PCP

non-NMDA Receptor

 -bind to glutamate agonists, Kainate, quisqualate, AMPA

Slide 10 .O {font-size:149%;}

Glu binds to receptor activating PLC->formation of 2 PI -> inositol IP3 and DAG

What takes over?

depolarized vm

Hyperpolarized Vm

Depolarized = more positive = concentration

hyper = more negative = electro gradient