Lecture 10 & 11: Synapses Flashcards
What are Synapses connection
Between two neurons or a neuron and another cell that is specialized for the transfer of information
Synapses is delivered from the _____ cell to the __________ cell
presynaptic cell to the postsynaptic cell
What are the two main ways we classify Synapses
1) Functional
2) Location
Define Electrical functionality for neurons
Passes directly between 2 cells, carried by the movement of ions between cells
Common in cardiac and smooth muscle
Depolarization or hyperpolarization
Fast
How does the relationship work between synapses and intelligence
more synapses = more intelligent
Define Chemical functionality for neurons
Specilized form of exocytosis
Electrical signals from one neuron is converted to a chemical signal to cross the synaptic cleft then is converted back to an electrical signal
Is chemical or electrical functionality more common for neurons
Chemical
Define Axodendritic synapses
Axon directly to dendrites (almost no reactions)
Define Axosomatic synapses
Axon directly to Soma
(more of an influence
Define Axoaxonic (initial segment)
Axon to either initial segment (trigger zone)
Most powerful
If synaptic activity leads to Depolarization of the postsynaptic cell it is considered
EPSP
IF ssynaptic activity leads to hyperpolarization of postsynaptic cell it is considered
IPSP
True or False; The grand Sum of EPSPs and IPSPs acting on a cell will determine whether the cell will reach threshold and fire an AP
True
Where must a threshold be reached to fire an AP
Axon Hillock
Define Excitatory postsynaptic potential (EPSP)
A depolarizing synaptic potential
Define Inhibitory postsynaptic potential
A hyperpolarizing synaptic potential
Cells with GAP junctions are said to be connected by what
Cytoplasm
Define Axoaxonic (pre synaptic)
If excitatory, depolarizes Ca+ in, causes a release of a neurotransmitter
If inhibitory- hyperpolarizes less Ca+ in, inhibits neurotransmitter
What are norepinephrine, dopamine, histamine, serotonin examples of
Amines neurotransmitters
Give an example of two novel neurotransmitters
Peptides and purines
Define synaptic delay
Time it takes for a substance to diffuse across and cause a postsynaptic response
What is Acetylcholine used by and causes what
Motor neurons to cause an excitation of skeletal muscles
How many different receptors are there for ACh and what are they and which one is fastest
1) Nicotinic receptor (FAST)
2) GPCR - Muscarinic receptor (SLOW)
Describe what happens when ACh binds to Nicotinic receptrs
Causes an Entry of Na+ causing a depolarization of the cell resulting in an EPSP
Describe what happens when ACh binds to muscarinic receptor
Creates 2nd messenger Kinase which phosphorylates K+ leakage channels causes K+ channels to close resulting in a depolarization stopping the leakage of positive charge (EPSP)
Where is Norepinephrine used, how many channels and types of channels, describe receptors
CNS
All use GPCR NO ion channels
Alpha and beta receptors
Glutamate is a main _____ in the ____
excitatory in CNS
What are the two types of Receptor channels for Glutamate and describe each
Iontoropic receptor channels
a) NMDA - Allows Na+ and Ca+ to enter (some K+ leaks out) causing depolarization of the cell. Typically blocked by Mg+ ions that get ejected when cell is depolarized by binding glutamate
b) AMPA - Binds glutamate causing an influx of Na+ causing a depolarization
Describe GABA and its receptor channels
Main inhibitory neurotransmitter used throughout the CNS
1) GABA A - Binds ligand causing the influx of Cl-causing a hyperpolarization of the cell. IPSP
2) Metabotropic GABA B - Binds a ligand and generates 2nd messengers kinases
Which GABA receptor is faster and why
GABA A is faster cause it does not need a 2nd messenger to create an effect
What synapse is is Acetylcholine located at
Cholinergic
True or False (GONNA BE A QUESTION ON EXAM) When given a 2nd messenger it is very easy to tell the effect of it
FALSE; Need lots of information
True or False; Not all GPCP Will cause closure of K+ channels
True
Which synaptic receptors, a receptor channel or GPCR causes a faster postsynaptic response
Lingand-gated ion channel
because it doesn’t require a 2nd messenger
AChR receptor channels do what
Na+ and a little K+
Depol
NMDA receptor channels do what
Na+, Ca2+, k+
Depol
AMPA receptor channels do what
Na+, little K+
Depol
GABA A receptor channels do what
Cl-
Hyperpol
Define Divergence and Convergence
Divergent pathways, one presynaptic neuron branches to affect a larger number of postsynaptic neurons
Convergent pathways many presynaptic neurons provide input to influence a smaller number of postsynaptic neurons
If two subthreshold potentials arrive at the trigger zone within a short period of time they may ____
Sum together and initiate an AP
Synaptic plasticity is the ability of neurons to do what
change synaptic strength
The best studied neurons that exhibit long-term potentiation in mammalian brains are located where
in the hippocampus
the cell must be ____ in order to gate NMDA-R open
Depolarized
Loong Term maintenance of synaptic potentiation does what 3 things
changes in gene expression
creation of new synapses
co-ordinated pre and post- synaptic effects
LTP (long-term potentiation) is seen as what and requires what
A long lasting potentiation of the EPSP
Requires: NMDA and AMPA receptors
