What are the three main structures involved in a synapse?
The three main structures are the presynaptic neuron , the postsynaptic neuron , and the synaptic cleft (the gap between them).
What is the primary function of synaptic vesicles?
They store and release neurotransmitters.
Where are ligand-gated channels located, and what do they bind?
They are located on the postsynaptic neuron and have receptors for neurotransmitters
What is a key difference between chemical and electrical synapses?
Chemical synapses use neurotransmitters and are more precisely controlled , while electrical synapses occur where cells join directly and are less common.
What ion is stimulated for release when an action potential reaches the synaptic terminal?
Calcium ions
What stimulates the merging of synaptic vesicles and the release of neurotransmitters?
The calcium ions.
What is the ultimate effect of the released neurotransmitter on the postsynaptic cell?
The neurotransmitter is released to impact the polarity (membrane potential) of the postsynaptic cell.
What is a membrane potential?
A negative charge on the inside of the cell versus the outside, establishing an electrical gradient in excitable cells.
What is an EPSP, and what ion movement causes it?
An Excitatory Postsynaptic Potential (EPSP) is a depolarization caused by sodium flooding into the cell
What is an IPSP, and what ion movement typically causes it?
An Inhibitory Postsynaptic Potential (IPSP) is a hyperpolarization that increases the negative charge within the cell, usually by pulling in chlorine
Define temporal summation.
Summation that comes from repeated stimulation of a postsynaptic neuron by a single presynaptic neuron
Define spatial summation
Summation from multiple presynaptic neurons acting on multiple dendrites of the same postsynaptic neuron at the same time.
What two factors determine whether a neurotransmitter has an excitatory or inhibitory effect?
The type of neurotransmitter and the type of receptor.
Give an example of a single neurotransmitter having different effects on different cells.
Norepinephrine stimulates contraction in the heart, but inhibits contraction in the intestines
List a common excitatory and a common inhibitory neurotransmitter derived from amino acids.
Glutamate (as glutamic acid) is an excitatory neurotransmitter, and GABA (aminobutyric acid, made from glutamate) is an inhibitory neurotransmitte
What are the two main ways that neurotransmitter activity is terminated at a synapse?
Degradation by an enzyme or reuptake into the presynaptic neuron.
How is Acetylcholine (ACh) activity terminated?
It is broken down in the synapse by the enzyme acetylcholinesterase (AChE)
How are Serotonin, Dopamine, and Norepinephrine activity terminated?
They are taken back up into the presynaptic neuron by transporters.
Quiz question: Acetylcholine is LEAST likely to be the neurotransmitter acting at synapses at:
Sympathetic nervous system effector cells
Quiz question: True or False If a post-synaptic cell receives predominantly GABA signals at its dendrites, it will most likely respond by transmitting an action potential down its axon
False
Quiz question: Acetylcholine binds primarily to:
Cholinergic nicotinic and muscarinic receptors
