Synaptic Transmission Flashcards
Ca2+ entering voltage gated channels in the presynaptic neuron causes what during muscle neurotransmission
- acetylcholine release and binding to receptor
what happens in an excitatory response
- Vm depolarizes
- increases probability of firing an action potential
what kind of gap occurs between cells in electrical synapses
- narrow gap
chemical synapse between neuron and non-neural effector cell is called
- neuroeffector junction
spatial summation
- from different regions of the cell that collide and can be added together
two types of graded responses
- excitatory
- inhibitory
site of initiation on axon of action potential
- first node of Ranvier
- axon hillock
electrical synapses occurs between
- neuron
- another cell
how does Ca2+ get back into the intracellular organelle?
- SERCA pumps
what is the principle route of Ca2+ removal from cytosol
- SERCA pump
inhibitory graded response called
- inhibitory post synaptic potential (IPSP)
when graded potentials exceed threshold
- an action potential is generated
most common name for synapse between two neurons
- neuronal synapse
local current between depolarized end plate and adjacent muscle plasma membrane causes
- muscle fiber action potential initiation
- propagated action potential in muscle plasma membrane
graded potentials at the NMJ
- always excitatory
loops in connexons
- cytoplasmic
- extracellular
what happens after action potential arrives at presynaptic terminal
- voltage gated Ca2+ channels open and Ca2+ enters the cell
how Ca2+ ATPase works
- brings H+ into cytosol
- pumps Ca2+ out into ECF
what activates post synaptic cell
- bound neurotransmitters
what happens to concentrations of Na+/K+ and Ca2+ if NA+/K+ ATPase is poisoned
- intracellular K+ will decrease
- cytosolic Ca2+ will increase
- intracellular Na+ will increase
- you won’t be able to pump K+ into the cell or Na+ out of the cell
- buildup of Na+ in the cell via it’s concentration gradient will allow you to shunt Ca2+ out into cytosol
whether the post synaptic response is IPSP or EPSP is determined by
- neurotransmitter released
- receptor at post-synaptic cell
- whether ion channels open or close
what is present in the membrane of each cell of gap junctions in electric synapse
- connexons
size of gap junction in electrical synapse
- 3.5 nm
what determines whether ion channels open or close
- selectivity properties of channels
- ions present and their gradients across the membrane
where does the action potential arrive at start of synaptic transmission
- presynaptic terminal
which type of synapse is most common in the nervous system?
- chemical
EPSPs action on membrane potential
- move membrane potential toward threshold for action potential
voltage gated sodium channels are located where in neuromuscular junction
- bottoms of junctional folds
- longitudinal surfaces
types of summation in graded potentials
- spatial summation
- temporal summation
cytoplasmic loops in connexons important for
- regulation
what calcium channels are there in the plasma membrane?
- voltage gated
- ligand gated
- Ca2+ gated
ACh receptors are located where in neuromuscular junction
- top of junctional folds of sarcolemma
where does additional Ca2+ come from mainly
- voltage-gated Ca2+ channels
pre synaptic features
- axon swelling
- synaptic vesicles
- mitochondria
- pre-synaptic density
extracellular loops in connexons important for
- hemophilic interactions
site of initiation on axon of graded potential
- post synaptic membrane
organelles that store Ca2+
- SER
- ER
- mitochondria
a rise in intracellular Ca2+ triggers what
- fusion of synaptic vesicle with presynaptic membrane
what happens in an inhibitory response
- Vm hyper polarizes or stabilizes
- decrease probably of firing an action potential
cytosolic free Ca2+ can bind to
- calcium-binding proteins
- protein kinases
- other proteins to mediate cell’s response
chemical synapses can occur between
- two neurons
- a neuron and a non-neuronal effector
synaptic cleft size between two neurons
- 25 nm
fate of neurotransmitter after activation of post synaptic cell
- breaks down
- taken up by presynaptic terminal
- diffuse away from synapse
what are connexons formed by
- 6 connexins
can action potentials summate?
- no!
gap junctions allow for
- rapid communication between linked cells
synapses between neurons can occur where?
- on the cell body (axosomatic)
- axons (axo-axonal)
- dendrites (axodendritic)
ways calcium enters cytosol
- through channel
- through intracellular stores of Ca2+ within organelles
graded potentials and distance
- decays over distance
cytosolic calcium levels compared to extracellular concentrations
- very low
- so calcium enters cytosol
synaptic cleft composed of
- glycocalyx
changes in permeability evoke what kind of response
- graded response
electron density in post synaptic cell located
- adjacent to synaptic cleft
how CA2+/Na+ exchanger works
- brings Na+ into cytosol
- pumps Ca2+ out into ECF
temporal summation
- from same neuron over different time to build on amplitude of response
what kind of junctions occur within the electrical synapse
what does it do?
- gap junction
- link cells
chemical synapse between neuron and skeletal muscle is called
- neuromuscular junction
how does Ca2+ get back out of the cell?
- Ca2+/Na+ exchanger in plasma membrane
- plasma membrane Ca2+ ATPase
two types of synapses
- electrical
- chemical
how SERCA pump works
- brings H+ into cytosol
- pumps Ca2+ back into organelle
neurotransmitter molecules are synthesized and packaged in what
- vesicles
acetylcholine release and binding to receptor causes what during muscle neurotransmission
- Na+ entry
- ## local current between depolarized end plate and adjacent muscle plasma membrane
what type of receptor is an acetylcholine receptor
- nicotinic cholinergic receptor
where do neurotransmitter molecules go
- diffuse across synaptic cleft
- bind to specific receptors on post synaptic cell
what neurotransmitter is always at the neuromuscular junction
- acetylcholine
what happens to acetylcholine at end of muscle neurotransmission?
- degraded by acetylcholinesterase
what can pass between cells in gap junctions in electrical synapse
- ions, sugars, solutes
excitatory graded response called
- as NMJ
- excitatory post synaptic potential (EPSP)
- end plate potential (EPP)
graded potentials are ____ changes in membrane potential
- transient changes in membrane potential
IPSPs action on membrane potential
- stabilize or move membrane potential away from threshold for an action potential
start of pre-synaptic events during neurotransmission with motor cell
- motor neuron action potential
- Ca2+ enters voltage gated channels
binding of a neurotransmitter to its receptor results in
- ion permeability changes in post synaptic cell
