Synapses Flashcards
What are synapses
Connection between two neurons or a neuron and another cell that is specialized for the transfer of information
How can synapses be classified
Based on function
- electrical vs chemical
Based on location
- Axodendritic
- axosomatic
- axoaxonic
Synaptic activity causes ___ potentials in the postsynaptic cell
Graded
A depolarizing synaptic potential is called an ____
an excitatory postsynaptic potential
A hyperpolarizing synaptic potential is called
An inhibitory postsynaptic potential
The grand sum of EPSP and IPSP at the axon hillock will determine what
If the threshold potential is exceeded and an action potential is stimulated
What are electrical synapses
Electrical information passes directly between two cells carried by the movement of ions
Explain electrical synapses
Usually bidirectional
Depolarization or hyperpolarization
Fast
Small molecules can travel through GAP junctions
Allows cells to fire AP synchronously
Cells with gap junctions are said to be connected by what
Cytoplasm
What are chemical synapses
Specialized form of exocytosis
Release of neurotransmitter from presynaptic cells to influence electrical activity in postsynaptic cell
Neurons communicate with each other and post synaptic targets (muscles glands)
The electrical signal from one neuron is converted to a ___ signal to cross a synaptic cleft then it is often converted back to an electrical signal
Chemical signal
What are the classic types of neurotransmitters
Acetylcholine
Amines (norepinephrine dopamine histamine serotonin)
Amino acids (glutamate, GABA)
What are the novel neurotransmitters
Peptides (oxytocin and melanocortin)
Purines (ATP)
Gases (NO)
Lipids (eicosanoids)
What is the general mechanism of synapses
AP travels down axon and depolarization opens voltage gated Ca channels
Ca channels enter presynaptic terminals
Ca entry causes synaptic vesicles to fuse with presynaptic membrane and release their neurotransmitter contents into the synaptic cleft
Neurotransmitter binds to receptors
When neurotransmitters bind to postsynaptic receptors the response depends on what
The type of receptor
Some are ion channels
Some are GPCR
What is the synaptic delay
The time taken to diffuse across and cause postsynaptic response (2ms)
The neurotransmitter is removed from the cleft and
Destroyed in the synaptic cleft by a degradative enzyme or
Transported back into the terminal by active transport recycled and repackaged
Dishes away from synapse
Taken up into postsynaptic cell by endocytosis
Acetylcholine is a neurotransmitter where
At a cholinergic synapse
Acetylcholine is used by
Motor neurons to cause excitation of skeletal muscles
Used in every pathway of the autonomic nervous system
Used throughout the central nervous system as a neuromodulator
What are two main kinds of receptors for ACh
Receptor channels (NICOTINIC RECEPTOR) (fast=EPSP)
GPCR (MUSCARINIC RECEPTOR
Slow=ESPS)
Binding of ACh to receptor channels causes
Opening of channels
Entry of Na and exit of k
(EPSP) movement of + charge into cell causes what
Depolarization
Binding of ACh to GPCR causes
Generation of second messengers
Activation of kinase
Phosphorylation of proteins (can open or close gates depending)
The slow EPSP ACh means a common effect is
Closure of k leak channels
Norepinephrine is called a
Noradrenergic synapse
Norepinephrine is used when
Throughout the CNS and by sympathetic branch of ANS
Norepinephrine use what type of receptor
GPCR
Glutamate is called a
Glutamatergic synapse
What is glutamate used for
Main excitatory transmitter through the CNS
What are the two types of receptors glutamate uses
Receptor channels (ionotropic) -AMPA -NMDA -kinate
GPCR (metabotrophic glutamate)
NMDA allows for ___ and __ to enter
Na AND ca
