Ionotropic and Metabotropic Neurotransmission Flashcards
Synaptic Transmission
chemical means by which neurons communicate with each other
A. Where are neurotransmitters released from?
B. What is the space between membranes involved in transmitter release called?
C. What do the receptors in postsynaptic membranes generate?
A. The vesicles in the presynaptic membrane
B. Snaptic cleft
C. Postsynaptic potentials
1In ionotropic gated transmission receptors are…
2 Ionotropic gated transmission is transient or lasting?
1transmitter/ligand gated channels
2. transient (10-20 milliseconds)
In ionotropic gated transmission binding with a neurotransmitter changes its configuration to increase or decrease its permeability to ions
increases
The net effect of EPSP is polarization or depolarization? Why? What ions are involved?
Increase in permeability of Na+ and K+. Na+ enters (depolarizes) cell and K+ exits (polarizes). Higher concentration of Na+ outside cell results in overall depolarization
What is an excitatory action?
The membrane depolarizes closer to threshold of action potential, this increasing the excitability
Where do excitatory synapses normally occur?
on dendrites
The net effect of an IPSP is polarization or depolatization? Why? What ions are involved?
Hyperpolarization is caused by influx of Cl- and efflux of K+ ions.
What is an inhibitory action?
THe membrane hyperpolarizes away from the threshold, decreasing excitability
Where are inhibitory synapses usually found?
on cell bodies
What is spatial summation of psp’s?
Simultaneous activation of EPSPs in different regions of the cell
What is temporal summation?
the summation of synaptic potentials from the same synapse can summate to create overall excitation or inhibition
Define excitation
The summated EPSPs can approach and exceed the threshold for action potentials
Define inhibition
Summated IPSPs can pull membrane away from the threshold, decreasing the likelihood that an action potential will be initiated
How many axons can synapse upon a single neuron
thousands
What does EEG measure?
The synchronization of PSPs among large populations of neurons
What type of information is processed in dendrites and cell bodies?
Postsynaptic potentials (analog” information… enough or not enough to create AP)”
What type of information is processed at the axon hillock?
AP initiation
What type of information is processed at the Axon?
AP conduction (digital” information)”
What type of information is processed at the axon terminals?
Synaptic release
Non-gated channels: What type of ions are involved and where are the channels located?
THey are K+ channels
Located along the whole cell, except initial segment and nodes of Ranvier
Voltage gated channels: What type of ions are involved and where are the channels located?
- Na+ and K+ channels- located at the initial segment and nodes of Ranvier (APs)
- and Ca++ channels- located at axon terminal (transmitter release)
Neurotransmitter/ligand gated: What type of ions are involved and where are the channels located?
- Na+/K+ channels- located at Postsynaptic dendrite membranes (EPSPs)
- Cl- channels- located at postsynaptic cell body membrane (IPSPs)
- Metabotropic gated transmission does or does not penetrate membrane?
- Its effect is lasting or transient?
- Does not
2. Lasting (minutes to hours)
What type of membrane receptors does Metabotropic gated transmission use?
What do they bind?
What effect does this have?
- membrane receptors
- liopophobic transmitters that don’t penetrate the membrane
- cascade effect- prolonged
In metabotropic systems, what does JAK do?
links with receptor and alters call activity by phosphorylating proteins
What do G proteins utilize?
GTP (Guanosine triphosphate)
What do beta and gamma portions of the G protein bind to and what do they do?
They bind directly onto ion channels and alter their permeability
How are G proteins used during heart deceleration?
vagus nerve stimulates SA node using Ach, releases G protein and opens K+ channels
What are two examples of second messengers?
cAMP and IP3/DAG- universal
What is cAMP synthesized from?
ATP
What determines how much cAMP is formed?
the balance between isoform of alpha portions of G protein ( stimulate or inhibit cAMP in their different forms)
cAMP induces or deters the PKA phosphorylation of contractile proteins, ions channels, enzymes of intermediary metabolism and other regulatory proteins?
induces
What effect does cAMP have on neuronal excitability?
Produes long term (hours) changes in neuronal excitability by altering permeability of non-gated” K+ channels”
How does cAMP regulate metabolic pathways?
It converts glycogen to glucose in the liver and muscle cells and releases fatty acids from adipose cells
G protein activates phospholipase C (PLC). What does this do?
PLC cleaves phophatidyl inositil (PIP) into second messengers: IP3 and DAG
IP3 releases Ca++ from where and what does Ca++ do?
Released from ER, regulates smooth muscle contraction
DAG activates which protein and what does it do?
Enxyme protein kinase C- promotes cell division and proliferation
What are CREB proteins?
Transcription factors that can produce long term changes in the functions of ion channels
How is cAMP involved in CREB activation?
cAMP activates Protein kinase A (PKA) which phosyphorylates CREB
(other pathways are responsible as well)
What is meant by up and down regulation?
The way cAMP-activated proteins interact with regulatory TF on DNA to up or down regulate gene expression- effects last for days
