Unit 5-PSYC 255- pt1

what is the chemical part of electrochemical communication?

neurotransmitters

what are neurotransmitters

Chemical released by a neuron onto a target that has either an excitatory inhibitory effect (or other more complex effects)

what is the target for sensory and interneuron transmitters

another neuron

what is the target of a motor neuron transmitter

a muscle fiber

what are the chemicals that circulate in the bloodstream called

hormones1

what kind of targets do hormones have

distant ones

what kind of targets do transmitters have

close ones

what are hormones released from

glands

what distinguishes the difference between neurotransmitters and hormones

where the chemical is acting not necessarily the structure

what do both hormones and transmitters do

change the brain and body to modulate behaviour

where do neurotransmitters get released?

presynaptic membrane

-output side of synapse

where are neurotransmitters received

postsynaptic membrane

-input side of mebrane

what is usually the presynaptic membrane

the axon terminal

for an excitatory message of the sensory or interneurons what is normally the postsynaptic mebrane

the dendrites or dendritic spines

if the message is inhibitory for interneurons where will the postsynaptic gap usually be

the soma

for motor neurons where will the postsynaptic gap be

the end plate of the muscle fiber

synaptic vesicles

• A membrane structure that contains a neurotransmitter

  • Little sacks where neurotransmitters are housed

how much neurotransmitter is housed in the vesicle

There is just enough inside that can produce a graded potential but not an action potential

what other function do the vesicles allow for

Also makes sure that the neurotransmitter is not broken down prematurely before it needs to be used

what puts neurotransmitters into the vesicles

golgi bodies

are all neurotransmitters stored in the vesicles

no some are not

what is the synaptic cleft

• Gap that separates the presynaptic membrane from the postsynaptic membrane

• Where neurotransmitters are released when stimulated by an action potential

what are receptors

the stuff that the transmitter binds to in order to create an affect

what happens if there is no transmitter

can't communicate with the receiving side so receptor is needed for communication

what are the steps of neurotransmission

synthesis, packaging and storage, release of NT, receptor activation, deactivation of NT

how many categories of neurotransmitters

5

where are small molecule transmitters synthesized

in axon terminal with chemical precursors from food pumped into the cell via transporters proteins

do the gates and pumps allow the precursors in

Not the gates and pumps letting the precursors in because those only allow ions in so different proteins

what converts precursors into neurotransmitters

enzymes

are small molecule transmitters put into vesicles

yes

where are peptide transmitters synthesized

in the soma using the DNA code and transported on microtubules

where do peptide transmitters wait to get activated?

terminal bouton

where are vesicles attached

microfilaments

lipid transmitters are made where?

postsynaptic membrane

what does it mean that lipid transmitters are retrograde

bind to receptors in the presynaptic membrane

are lipid transmitters stored?

no because Made in response to stimulation and are not actually stored so right after they're made they are used

what are gas transmitters made from

Made from precursors in our diet and from gases like oxygen that are combined together to make the transmitter

are gas transmitter stored

no made in response to stimulation

ion transmitters include

zinc, calcium, and magnesium

where do ion transmitters come from

inner body already

are ion transmitters stored

yes they go to vesicles and they have other neurotransmitters in these vesicles as well

is exocytosis limited to NT

no its anything that exits the cell

what open the voltage sensitive calcium channels

the AP at the terminal

what forms the complex

incoming Ca influx binds to calmodulin

what does the complex cause the vesicle to do

causes it to empty or get readywh

what determines the amount of neurotransmitter released?

depends on the amount of calcium and the amount of vesicles

what is the activation of the receptor site specific to

small molecule, peptide, and ion transmitter onlu

what happens to the NT after it is released

diffuses across the synapse and activates the postsynaptic receptors

what are transmitter-activated receptors

are proteins embedded in the membrane and have a binding site for a specific NT

how do receptors and transmitters work

in a key and lock fashion

• Meaning certain transmitters only activate certain receptors

• Some master keys that unlock multiple locks

activation of the receptor site depolarization

• Depolarize the postsynaptic membrane causing an EPSP (open Na ion channels)

  • Na comes rushing in

activation of the receptor site hyperpolarization

• Hyperpolarize the postsynaptic membrane causing an IPDP (open K or Cl ion channels)

  • Influx of Cl or efflux of K

auto receptors

"self-receptor" in a neural membrane that responds to the transmitter that the neuron releases

-are metabotropic

where are auto receptors found

• Found on the presynaptic membrane

what do auto receptors do

• To monitor the usage of the neurotransmitter that the neuron produced and released

• Helps to mediate transmitter production

  • Ie need to produce more or less

how do you make sure that NT messages still carry meaning

need to be break between the nT

what are the 4 ways to deactivate a NT

• Diffuse away from synaptic gap

• Degraded by enzymes in gap

• Reuptake into the presynaptic neuron for subsequent re-use or recycled as well

• Taken up by nearby glial cells

what do NT not go through

Neurotransmitters don't go through the receptors to enter the cell they only activate

what do NT go through

• Neurotransmitters do go through transport proteins to enter the cell

  • Or the building blocks of the neurotransmitters

are auto-receptors responsible for reuptake?

NOOOO

axodendritic synapse

1. axon terminal of one neuron synapses on dendritic spine of another

   1. Predominantly excitatory

axosomatic synapse

1. axon terminal ends on cell body

   1. Predominantly inhibitory

axomuscular

motor neurons

type 1 synapse

• Excitatory

• Typically on dendrites

• Large active zone

• Wide cleft

  • Further to travel

  • Message needs to be stronger

  • So more sensitive

• Round vesicles

• Dense material on membranes

Type 2 Synapse

• Inhibatory

• Typically on cell body

• Small active zone

  • Few receptors and neurotransmitters

• Narrow cleft

  • So less diffusion

• Flat vesicles

• Sparse material on membranes

how many types of neurotransmitters

100+

are NT only excitatory or inhibitory

no can be one at one place and the other somewhere else

how many NT can be active at one synapse

multiple

us there a simple 1-1 relationship between a single NT and behaviour

no

4 criteria for identifying NT

• Must be synthesized and/or packaged in the neuron

• The chemical must produce a response in a target cell when released

  • Excitatory, inhibitory, or the other mysterious effect

• The same responses must be obtained when the chemical is experimentally placed on the target

  • To confirm that is what the chemical and not something else

• Must be a mechanism for removal after the chemical's work is done

which NT have the most widespread use

small molecule

where do small molecule NT bind

ionotropic and metabotropic

are small molecule fast or slow

quick acting

where are small molecule packaged

axon terminal

small molecule NT

acetylcholine, amines, amino acids

acetylcholine

• Acetate and choline

  • Multiple enzymes are needed to transfer into acetylcholine

amines

• Dopamine

• Norepinephrine

• Epinephrine

  • Serotonin

serotonin

Made from tryptophan gets converted to a precursor before getting created into serotonin

Norepinephrine

• is made from dopamine

  • Noradrenaline

    • Both hormone and transmitter

epinephrine

• is made from norepinephrine

  • Adrenaline

  • Hormone

amino acids include

glutamate and GABA

glutamate

• Excitatory

  • Made from both diet and stuff in the body

GABA

• Inhibitory

• Made from glutamate through enzymes

peptide transmitters

Are chains of amino acids synthesized from mRNA based on DNA code

where peptide transmitters synthesized

in soma and shipped to the terminal and packaged to vesicles through golgi bodies

how do peptide transmitters act

• Act slower and replaced slower than small molecule

  • Since made by DNA

  • Work at metabotropic receptors

  • Often act as hormones

how localized are peptide

more localized and specific in actions

peptide transmitter examples

Oxytocin, endorphins, vasopressin

where do lipid transmitters bind

Binds to receptor on presynaptic membrane, which decrease NT release (GABA, glutamate) from presynaptic membrane

what is the most common type of NT in the brain

lipid NT

types of lipid NT

• Anandamide 2-AG

  • Both derived from arachidonic acid