Neurophys 3-4 Flashcards
Ionotropic receptors
Produce electrical signal
- binding of transmitter directly opens or closes ion channels
- made of protein subunits forming a pore
- faster, short lived effect
- locally effective
Metabotropic receptors
Produces chemical signal
Binding can cause secondary mechanical action
Proteins w 7 transmembrane regions
Can indirectly opening or close ion channels
Slower, longer lasting effect
Can have modular effects through cell
G proteins
Guanine nucleotide binding proteins
Bind & hydrolyze GTP
- GTP= active
- GDP = inactive
Translate extra cell signal to intracell effects
Acetylcholine - neurotransmission
PNS (NMJ)
ANS
Interneurons in CNS
Types of acetylcholine receptors
Nicotinic
- ionotropic
- excitatory (Na & Ca)
Muscarinic
- metabotropic
- excitatory or inhibitory
Glutmate
Major excitatory neurotransmitter in CNS
Excitatory postsynaptic potential
Ionotropic receptors of glutmate
AMPA - Na & K
NMDA - Na, K, Ca
Kainate- Na & K
Metabotropic receptors of glutmate
At least 8
Excitatory or inhibitory
Causes CNS excitement, could be toxic
GABA
Gamma aminobutyric acid
Major inhibitory transmitter in CNS
Inhibitory postsynaptic potential
Allows chloride in (more neg) hyperpolarization = less likely to fire
Classes of GABA receptors
GABAa - ionotropic , Cl channel
GABAb - metabotropic
Catecholamines
Epinephrine and norepinephrine
- released from adrenal medulla
- CNS & sympathetic NS
Dopamine - CNS only
ONLY Metabotropic receptor
Epi and nor - adrenergic (alpha & beta w subtypes)
Dopaminergic receptors D1-D5
Serotonin
5HT
Regulation of behavior
Metabotropic & ionotropic receptors
Mainly CNS
Endogenous opioids
Made in cell body - produced mainly in pituitary
Endorphins, enkephalins
Neuro peptides
Block pain - act of CNS & PNS
Modulates transmitter release
Metabotropic opioid receptors
Mu (1, 2, 3)
Delta, norciceptin, zeta
Neurotransmitter synthesis 1
Neuro peptide neurotransmitter
- synthesized in cell body & transported to axon terminal
Most neurotransmitters
Synthesized locally in the axon terminal
Acetylcholine synthesis
Choline
- essential nutrient
- synthesized by liver
Acetyl coenzyme A
- Formed through oxidation of pyruvate (glycolysis)
Choline acetyltransferase
- enzyme that catalyzes formation of ACh
Glutamate synthesis
AA acquired through diet
Synthesized from glutamine
Synthesized from alpha ketoglutarate (TCA)
Catecholamine synthesis
Synthesized from phenylalanine
- all connected through enzymatic function
Serotonin synthesis
Synthesized from tryptophan
Endogenous opioid synthesis
Gene for neuropeptide is transcribed from mRNA
Moves out of nucleus to ribosome
mRNA determines sequence of AA by interacting with tRNA
Protein is formed
Step 2- transmitter packaging for Neuropeptides
(endogenous opioids)
Peptide is packaged in vesicle & transported down axon
Neurotransmitter packaging for most neurotrans
Synaptic vesicle is form in Golgi apparatus
Made of membrane phospholipids & proteins
Transported down the axon
Neurotransmitter packaging
Transmitters are packaged into vesicles by specific transporters
- Mem bound proteins (moves into vesicle)
- vesicular acetylcholine transporter (VAChT) endogenous opioids prepackaged w/ vesicle & transporter before going down axon)
Process requires calcium
Step 3 neurotransmitter release pt 1
Mediated by VG Ca channels
Vesicle move to synapse
Vesicle membrane fuses w plasma membrane
Neurotransmitter is released into synaptic cleft
Step 4 neurotransmitter release
Effects depends on type of transmitter
Could be more than one receptor type at each synapse
Can bind to presynaptic receptor “autoreceptor”
Usually terminate release of transmitter - neg feedback loop
Ionotropic or metabotropic
Step 5 neurotransmitter degraded
Synaptic vesicle membrane that fused w cell membrane can phagocytose & recycle transmitter
Specific enzyme degrade each
- acetylcholinesterase degrades ACh
Some also diffuses away from synapse
Astrocyte role
Can recycle glutamate & GABA in CNS
Acetylcholinesterase
Degrades acetylcholine in synaptic cleft
Choline is taken up by cell & recycled
Acetylcholinesterase inhibitors
Nerve agents
Insecticides
Drugs to treat Alzheimer’s
Active ingredient in marijuana
Monoamine - catecholamines + serotonin
Can treat depression, anxiety, PTSD, OCD
Anxiety in pets
- fluoxetine
- sertraline
- paroxetine
Tetrodotoxin
From puffer fish (snails, octopuses, toads, newts)
Produced symbiotic bacteria
Binds & blocks VG Na channels
Prevents AP generation / propagation
