Chapter 4 - Neural Conduction and Synaptic Transmission

Stony Brook Univesity SBU PSY250 Biopsychology

membrane potential

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

microelectrodes

the intracellular electrodes used in detecting membrane potential

resting potential

the millivolts recorded when the neuron is at rest

polarized

having a membrane potential that isn’t 0

ions

positively and negatively charged particles

ion channels

specialized pores in the neural membrane that allow ions to go in and out

sodium-potassium pumps

mechanism in the cell membrane that continually exchange three Na+ ions inside the neuron for two K+ ions outside

transporters

mechanisms in the membrane of a cell that actively transport ions or molecules across the membrane

postsynaptic potentials (PSPs)

disturbances of the resting membrane potential as a result of input from cells that synapse on a neuron

depolarize

decrease the resting membrane potential

hyperpolarize

increase the resting membrane potential

excitatory postsynaptic potentials (EPSPs)

postsynaptic depolarizations that increase the likelihood that the neuron will fire

inhibitory postsynaptic potentials (IPSPs)

postsynaptic hyperpolarizations that decrease the likelihood that the neuron will fire

graded potentials

PSPs, EPSPs, and IPSPs

what was once believed to happen in the axon hillock?

action potentials were generated there

axon initial segment

where action potentials are generated

threshold of excitation

when the sum of the depolarizations and hyperpolarizations reaching the axon initial segment is sufficient to depolarize the membrane to a level around -65mV, AP is generated

action potential (AP), are they graded?

signal fired, no

all-or-none responses

magnitude is not to intensity of the stimuli that elicit them

spatial summation

EPSPs produced simultaneously on different parts of the receptive membrane form a greater EPSP, same for IPSPs

temporal summation

PSPs produced in rapid succession at the same synapse form a greater signal

voltage-gated ion channels

ion channels that open or close in response to changes in membrane potential

absolute refractory period

period of 1 to 2 milliseconds after an AP when it’s impossible to fire an AP

relative refractory period

possible to fire the neuron again only by applying higher levels of stimulation

antidromic conduction

the AP that travels along the axon back to the cell body if electrical stimulation of sufficient intensity is applied to a midpoint of an axon and 2 APs are formed

orthodromic conduction

the AP that travels along the axon towards the terminal buttons if electrical stimulation of sufficient intensity is applied to a midpoint of an axon and 2 APs are formed

nodes of ranvier

gaps between adjacent myelin segments where ions can pass through the axonal membrane

saltatory conduction

transmission of APs in myelinated axons is called

dendritic spines

nodules of various shapes that are located on the surfaces of many dendrites

tripartite synapse

synapse that involves two neurons and an astroglial cell

directed synapse

site of neurotransmitter release and the site of neurotransmitter reception are in close proximity

nondirected synapses

site of release is at some distance from the site of reception

neuropeptides

all large neurotransmitters, short proteins made of 3 to 36 amino acids

synaptic vesicles

packages of neurotransmitters

golgi complex

modifies/sorts/packages proteins and lipids

coexistence

many neurons contain two neurotransmitters

exocytosis

the process of neurotransmitter release

receptors

receive neurotransmitters

ligand

any molecule that binds to another, a neurotransmitter is the ligand of its receptor

receptor subtypes

different types of receptors that a particular neurotransmitter can bind to

ionotropic receptors

associated with ligand-activated ion channels

metabotropic receptors

associated with signal proteins and G proteins

g proteins

guanosine-triphosphate−sensitive proteins

second messenger

a chemical they may be synthesized when a part of a G protein breaks away

autoreceptors

metabotropic receptors that bind to their own neuron’s neurotransmitter molecules, they are located on the presynaptic membrane

reuptake

more common, neurotransmitters drawn back into the presynaptic buttons by transporter mechanisms

enzymatic degration

neurotransmitters broken apart in the synapse by enzymes

enzymes

proteins that stimulate or inhibit biochemical reactions without being affected by them

acetylcholinesterase

brakes down acetylcholine in enzymatic degradation

gap junctions

narow spaces between adjacent cells that are bridged by connexins

what are amino acid neurotransmitters? name the 4 common ones.

fast-acting directed synapses in the central nervous system
glutamate, ­ aspartate, glycine, and GABA

how are glutamate, aspartate, glycine, and GABA made?

first 3 are common proteins we eat
GABA is a modified glutamate

monoamine neurotransmitters

slightly larger than amino acid neurotransmitters who’s effects tend to be more diffuse

what are the 4 monoamine neurotransmitters?

dopamine, epinephrine, norepinephrine, serotonin

catecholamines

dopamine, epinephrine, norepinephrine,
synthesized from tyrosine

indolamines

serotonin
subtype of monoamine neurotransmitters

acetylcholine

small-molecule neurotransmitter at neuromuscular junctions, synapses in ANS and CNS

soluble-gas neurotransmitters

category of unconventional neurotransmitter
nitric oxide, carbon monoxide

endocannabinoids

category of unconventional neurotransmitter
anandamide

neuropeptide transmitters, what are the 5 kinds?

large-cell neurotransmitters
pituitary, hypothalamic, brain-gut, opioid, misc,

agonists

drugs that facilitate the effects of a particular neurotransmitter

antagonists

drugs that inhibit the effects of a particular neurotransmitter

receptor blockers

bind to postsynaptic receptors without activating them, blocks the access of neurotransmitters

atropine

receptor blocker, antagonist effect by binding to muscarinic receptors, thereby

blocks acetylcholine effects

botox

neurotoxin released by a bacteria in spoiled food, nicotinic antagonist, blocks release of acetylcholine at neuromuscular junctions

periaqueductoal gray (PAG)

microinjection of morphine induces strong analgesia

endogenous

occurring naturally in the body

name 2 families of endogenous opioids

enkephalins, endorphins