unit 3 - pt1. Neurons & synapses Flashcards
Electrical signals are within a neuron and include
- Local potentials (in dendrites and soma)
- Action potentials (down axon)
Chemical signals are located between neurons and include
neurotransmitters
A resting neuron is
polarized (difference in electrical charge ions inside vs outside of cell)
Ions are
electrically charged molecules
anions are
negatively charged
cations are
positively charged
The resting potential of a neuron is around
-70 millivolts (mV)
The resting potential (Ionic basis) is close to
the equilibrium potential for K+
Electrical pressure for potassium (K+) to enter cell, but
chemical pressure to leave cell
Electrical and chemical pressure for sodium (Na+) and
calcium (Ca++) to enter cell
Chemical pressure for chloride (CL-) to
enter cell
ion channels may be opened by several triggers, including (4)
- Ligand binding
- change in membrane potential
- phosphorylation
- G proteins
Inhibitory post-synaptic potential (IPSP) =
hyperpolarization from K+ or CL- channels opening
Excitatory post-synaptic potential (EPSP) =
depolarization from Na+ channels opening
threshold (about -40 mV), triggers a
brief action potential (or spike)
(During action potential) The membrane potential reverses, and the inside of the cell becomes
positive
The action potential is caused by a sudden rush of Na+ ions into the
axon
Voltage-gated Na+ channels conduct the
action potential down the axon
Local potentials (ESPS & IPSPS) are depolarization or hyperpolarization VS action potentials which are just
depolarization
Synapse (to clasp or join) is the site of
action for most psychoactive drugs
(presynaptic synapse)
The axon terminal contains synaptic vesicles that contain
neurotransmitter
(postsynaptic synapse)
What responds to the neurotransmitters?
Receptors
- Amino acids (Glu, GABA)
- Monoamines (DA, NE, 5-HT)
- Acetylcholine
- Purines
Classical neurotransmitters
- Neuropeptides (opioids)
- Lipids
- Gases
non-classical neurotransmitters (no vesicles)
3 steps in chemical synaptic transmission
- synthesis
- release
- inactivation
Classical NTs are synthesized from
dietary precursors
Enzymes in the ??? synthesize the NTs and then are transported into the small vesicles
axon terminals
Neuropeptides are synthesized in the ???, packaged into large vesicles, and then transported. What is this process called?
What else can they release?
- cell body
- protein-synthesis dependent
- classical transmitters
Classical NTs require
active transport
Vesicular transporters move transmitters into
vesicles
Vesicle fusion with cell membrane is mediated by
SNARE proteins
Botulinum toxin cleaves SNARE proteins involved in vesicle fusion
Botox
vesicle membrane is retrieved from the terminal membrane
endocytosis
New (empty) vesicles can be refilled with NT rapidly =
vesicle recycling
Neurotransmitter binds to receptors on the
postsynaptic side
These receptors can be what or what
ionotropic (ligand-gated ion channels)
or
metabotropic (G protein-coupled receptors)
Neurotransmitter also binds to autoreceptors on the what side
presynaptic
Autoreceptors are receptors on the same neuron releasing NT and they provide
feedback (usually negative)
What kind of autoreceptor modulates NT release?
What kind or autoreceptor modulates NT synthesis or firing?
- Terminal
- Somatodendritic
Nts are inactivated via
- Rapid ENZYMATIC DEGRADATION (metabolism via enzymes)
OR - PLASMA MEMBRANE TRANASPORTERS located in the nerve terminal , REUPTAKE, or glia
Are transporters in inactivation different than vesicular transporters?
YES
Retrograde transmission is signaling from
post-synaptic to pre-synaptic cell
(diff than anterograde transmission used in most signaling)
Gases and lipids pass through membranes and signal to the ? No what?
presynaptic terminal (NO VESICLES)
