#4.3 Sequence of Events of Chemical Synapse

release of neurotransmitter

1st sequence of events

activating postsynaptic receptors

2nd sequence of events

termination of chemical signal

3rd sequence of events

graded potential

4th sequence of events

exocytosis

process of SYNAPTIC VESICLES fuse with the membrane of the AXON TERMINAL and release NEUROTRANSMITTER molecules in the synaptic gap

ca2+ voltage-gated channel

channels mostly located in the AXON TERMINAL MEMBRANE

synaptic vesicles

where neurotransmitters are stored prior to exocytosis

higher

before the release of neurotransmitter: Ca2+ have ________ concentration OUTSIDE the cell

kiss and run

PARTIAL release that the exocytosis has

partial & full release

exocytosis < (2&) release

exocytosis

action potential triggered -> Ca2+ voltage-gated channel open -> Ca2+ gets in the cell -> __________

negative feedback

presynaptic neuron's autoreceptors inhibits BOTH synthesis & release of neurotransmitter of the presynaptic neuron

autoreceptors

special protein structures in presynaptic membrane

autoreceptors

part of the presynaptic neuron that provides NEGATIVE FEEDBACK about neuron's level of activity

negative feedback

feedback that inhibits release of neurotransmitter of the presynaptic neuron

negative feedback

postsynaptic neurons release chemicals that travel back to presynaptic terminal to inhibit further release of transmitter

autoreceptors / postsynaptic neuron's chemicals

2 ways to give negative feedback < (2/)

ionotropic or metabotropic

exocytosis -> neurotransmitter binds to postsynaptic receptor -> (2or)

receptors

protein structures embedded in neural membrane that responds to neurotransmitters

neurotransmitter

can influence ONLY those cells that have its (answer) respective receptors

ionotropic receptor

TYPES OF RECEPTORS:

receptor's recognition site is located in the same structure as the ligand-gated channel

ionotropic effect

receptor's effect has a very fast reaction to neurotransmitter

ionotropic effect

receptor's effect that affects a small, local part of the cell

metabotropic receptor

TYPES OF RECEPTORS:

contains a recognition site and a G protein

metabotropic receptor

TYPES OF RECEPTORS:

releases G protein

G protein

METABOTROPIC RECEPTOR:

attaches to an ion channel which lets charged ions in the cell

G protein

METABOTROPIC RECEPTOR:

triggers synthesis of second messenger

second messenger

METABOTROPIC RECEPTOR:

diffuses and influence the activities of the neuron in a variety of ways

second messenger

METABOTROPIC RECEPTOR:

warns/triggers other channels to open

G protein

METABOTROPIC RECEPTOR:

protein coupled to GUANOSINE TRIPHOSPHATE (GTP)

G protein

METABOTROPIC RECEPTOR:

energy storing molecule

G protein

METABOTROPIC RECEPTOR:

found on the INTRACELLULAR SIDE of the metabotropic receptor

G protein

METABOTROPIC RECEPTOR:

released when a neurotransmitter binding to a metabotropic receptor

second messenger

METABOTROPIC RECEPTOR:

indirectly activated by synaptic activity

second messenger

METABOTROPIC RECEPTOR:

interacts with different parts of the cell

metabotropic effect

receptor's effect that can last much longer than the effect by ionotropic receptors' activation

metabotropic effect

receptor's effect that have wide ranging and multiple influences within the cell

termination of chemical signs

ways for neurotransmitters to be removed from the synapse AKA

diffusion / deactivating enzyme / reuptake

TERMINATION OF CHEMICAL SIGNALS < (3/)

diffusion

TERMINATION OF CHEMICAL SIGNALS:

neurotransmitter goes away from the high concentration area and goes to a low concentration area (or other neurons)

deactivating enzyme

TERMINATION OF CHEMICAL SIGNALS:

neurotransmitters are killed in the synapse by an enzyme

reuptake

TERMINATION OF CHEMICAL SIGNALS:

transporters from the presynaptic membrane goes out and collects the remaining neurotransmitters in the synapse and puts them back in the axon terminal

EPSP & IPSP

neurotransmitter -> binds to receptors -> open ion channels -> graded potential (2&)

EPSP & IPSP

graded potential < (2&)

excitatory postsynaptic potential (EPSP)

GRADED POTENTIAL:

open ion channels -> Na+ gets in the cell ->

inhibitory postsynaptic potential (IPSP)

GRADED POTENTIAL:

open ion channels -> Cl gets in, K+ gets out

graded depolarization

graded potential caused by Na+ getting in the cell once the ion channels open

graded depolarization

slight depolarization

graded hyperpolarization

graded potential caused by Cl getting in and the K+ getting out of the cell once the ion channels open

graded hyperpolarization

temporary hyperpolarization

excitatory postsynaptic potential (EPSP)

GRADED POTENTIAL:

can trigger action potential

excitatory input

TYPE OF INPUT:

mostly found in dendrites and dendrites spines

inhibitory input

TYPE OF INPUT:

occurs at the synapse of the cell

passively

EPSPs and IPSPs will spread ______ but rapidly until reaching the axon hillock

action potential

triggered if the threshold is reached when EPSP/IPSP (graded potential) reaches the AXON HILLOCK

temporal & spatial summation

How to reach action potential through EPSP? (2&)

temporal summation

ACTION POTENTIAL VIA EPSP:

repeated excitation from one active synapse = CUMULATIVE effect

temporal summation

ACTION POTENTIAL VIA EPSP:

summation over time

spatial summation

ACTION POTENTIAL VIA EPSP:

repeated excitation from combined inputs from many synapses coverage = cumulative effect

spatial summation

ACTION POTENTIAL VIA EPSP:

summation over space