Neurophysiology - Behavioral Neuroscience

neurophysiology

examination of electrical and chemical signaling processes within and between neurons

action potentials (AP)

electrical signal conveyed down the axon

axon hillock

part of the body where AP is initiated

when the AP arrives to the ?, it triggers the release of neurotransmitter ? across the ?

axon terminal/bouton, vesicles, synapse

the membrane of a neuron maintains a(n)

electrical gradient

electrical gradient

difference in the electrical charge between the inside and outside of the cell

resting potential (RP)

electrical gradient maintained by neurons

plasma membrane

allows small uncharged chemicals (not ions) to flow into and out of the cells

ions

anions (-) and cations (+)

lipids

hydrophobic

polar molecules and ions

hydrophilic

the plasma membrane is

hydrophobic, a lipid bilayer

voltage

measure of the stored or potential electrical energy (ex. ion buildup across the membrane)

current

measure of the rate of flow of electrical energy, movement of ions

potential difference

amount of energy required to move an ion from one point to another in space

potassium (K+)

membrane is permeable to this, more concentrated inside of neuron

sodium (Na+)

membrane is impermeable to this, more concentrated outside of the neuron

proteins

i travel lunar space is filled with this; they have a net negative charge; cannot diffuse out of the cell due to their very large size

three major players in resting potential

potassium (K+), sodium (Na+), proteins

chloride (Cl-) and calcium (Ca++)

minor players in RP, membrane is partially permeable

equilibrium potential (EP)

concentration gradient = electrical gradient

polarized neuron

potential across the cell membrane

hyperpolarization

increasing the difference b/t the electrical charge of two places, cell becomes more negative (-70 mV)

depolarization

decreasing the difference b/t the electrical charge b/t two places toward 0, cell becomes more positive/less negative (-50 mV)

excitation threshold

levels above which any stimulation produces a massive depolarization action potential

action potential (AP)

rapid depolarization of the neuron

voltage-sensitive ion channels

membrane protein-forming channels whose permeability depends upon the voltage difference across the membrane, Na+ channels and K+ channels

Na+ channels

open rapidly at depolarization potential of about -40 mV, inducing the action potential

K+ channels

open more slowly, repolarize the membrane

refractory period

time during which the neuron resists the production of another action potential

absolute refractory period

first part of the period in which th membrane cannot produce an action potential (i.e. when Na+ channels are open)

relative refractory period

second part in which it takes a stronger than usual stimulus to trigger an action potential (can sometimes happen when K+ channels are open)

lidocaine, novocaine

local anesthetics

local anesthetics block

Na+ channels

tetrodotoxin

Na+ channel blocker

all or none law

states that the amplitude and velocity of an action potential are independent of the intensity of the stimulus that initiated it

larger neuron diameters =

faster conduction velocity

myelination =

faster conduction velocity, produces saltatory conduction

nodes of Ranvier

interruptions in the myelin sheath, AP is regenerated by a chain of positively charged ions pushed along by the previous myelin segment

saltatory conduction

“jumping” of the action potential from node to node, provides rapid conduction and conserves energy for the cell

multiple sclerosis (MS)

disease in which the myelin sheath is destroyed and leads to loss of muscle coordination and motor control

local neurons/interneuronsn have

short axons, exchange info only with close neighbors

graded potentials

potentials that vary in magnitude and decay over time (contrast with all or none law)