cell bio 5c

6000 ions

charge distribution

the electrical potential required to balance the flux of an ion through a selective channel driven by its concentration gradient

sodium moves in, potassium moves out for nerve impulses through sodium and potassium channels

• ion channels control the membrane potential
• membrane potential is determined by unequal distribution of charge on two sides of the membrne (capacitor-like)
• b/c of potassium leak channels, resting membrane potentials are near the K+ equilibrium potential

• dendrites (receive signals)
• cell bodies (synthetic center)
• axons (relay signal and can be myelinated)
• synapse (release new signal)

neuromuscular junction: stimulates an action potential in the muscle plasma membrane

long axons in PNS and white matter in brain

ER, golgi, make synaptical vesicles (neurotransmitters)

sodium channels open

voltage gated Na channels open, which changes membrane potential; K channels open based on electrochemical gradient (voltage gated) Na goes into cell, K goes out. K leaks

• due to opening of voltage gated sodium channels
• closed sodium channel=membrane polarized
• open sodium channel (membrane depolarized)
• channels close to inactivated state that is refractory to activation of 1msec

• have six helices (S5 and S6 line pore)
• charged S4 helix acts as a voltage sensor
• nonhelical segments ling pore provide selectivity filter

Raw3-IP on the cytoplasmic side

Na channel inactivation and opening of voltage gated K channels

volrage channel trigger some Na channels to open which make other Na channels open

• action potentials involve a coordinated series of channel openings 
• small depolarizations trigger self-reinforcing openings of voltage gated sodium and potassium channels
• peak of action potential approaches Na equilibrium potential

• binds voltage gated sodium channels
• first isolated from fish of the order tetraodontidae (fish with 4 strong teeth); has a high dissociation constant (binds really tightly to sodium channels, blocks sodium channels from working

• electrical stimulation
• ions entering the cells in response to an excitatory neurotransmitter (Ache)

to open voltage gated channels; opening and closing of ion channels produces electrical signals that can be sent rapidly down

• Ca is outside cell, rushes in when voltage changes, through gated channels, Ca release causes synaptic vesicles to fuse with membrane, releasing neurotransmitter into synaptic cleft, which binds to receptors
• sodium channels leaks, propagates and stimulates voltage gated Na channels next to it to propagate signal
• K channels activated, goes out of cell, convert ligand gated channel to potential change, initiate new action potential on other side

connection between domain signaling nerve to responding nerve cell

• enzyme that degrades it
• endocytosized
• can be reused

Na entry depolarizes adjacent membrane, but inactivation prevents action potential from spreading in reverse?

put in electrodes, shows the shift of electrical signal

receive, conduct, and transmit signal through action potential without weakening; ensure that signal is reamplified

Na channels that further depolarize

electrical impulse

6 pass transmembrane protein, domain of channel that will block channel

in wider and myelinated axons

proprioception, touch, pan and temperature

spaces between glial cells, uninsulated segments of axonal membrane located at 1mm intervals

either inside brain glial cells or outside brain peripheral nervous system (schwann cells)

saltatory conduction

myelin sheath

inactivation of Na channels and continued entry of K ions through voltage gated K channels

binding of neurotransmitter to ligand gated channels in postsynaptic membrane initiates

if the membrane potential at the axon hillock reaches threshold

locally

• ligand gated cation channels-excitatory
• ligand gated Cl-channels -inhibitory

targets dopamine transporter (prevent dopamine from being transported back to signaling neuron, keep sending signal in the synaptic cleft

target norepinphrine or serotonin uptake (block the reuptake)

10^15

mRNA processing maturation of snRNP particles

cajal bodies, PML bodies, speckles

clusters of interchromatin granules, involved in RNA processing, not transcription sites

transcription factors

grounding cells up and doing differential centrifugation, in vitro look at function--no organelles found in nucleus

mutagenesis in yeasts, look for secretion mutants in ER, Golgi pathway; identify proteins in the secretory pathway by doing mutagenesis

use antibodies that are made to differnt components of nucleus and see that idff component within nucleus are localized differently

genes that encode ribosomes are concentrated there; these genes are most likely duplicated; different copies of ribosomal genes whose job is to make ribosomal RNA

1-5 per nucleus; transcriptionally active rRNA gene clusters; nearly 700 proteins in involved in rRNA synthesis