#4

Question 1

What is a synapse?

Answer 1

a presynaptic terminal of one neuron makes junctions with the post synaptic neuron and most can be found on dendrites

Question 2

what are the 3 types of synapses?

Answer 2

Axodendritic : an axon is making a synapse with dendrites.
spine synapse: most of the axodendritic synapses happens at protrusions of dendrites called spines.

Axosomatic: axon is making a synapse with a soma

Axoaxonic: a presynaptic terminal of one axon makes a synapse with another presynaptic terminal on another axon.

remeber that one neuron through its branching axon may make synapses with many other neurons

Question 3

what is a presynaptic terminal?

Answer 3

filled with spheres called synaptic vesicles which are filled up by small molecules called neurotransmitters ( released by the presynaptic terminals)

Question 4

2 types of neurotransmitters

Answer 4

Back-up vesicles: randomly “floating” around in terminals, vesicles that are not used immediately

Docked vesicles: lined up in the active zone, facing the postsynaptic spine.

Question 5

What is the active zone?

Answer 5

a specialized region that hold a subset of presynaptic vesicles in presynaptic vesicles facing the postsynaptic spine

also the place where vesicles will release neurotransmitters into synaptic cleft, a narrow space between the presynaptic terminal and the postsynaptic spine, and interact with the postsynaptic spine,

Question 6

what happens in the postsynaptic spine ?

Answer 6

there os a postsynaptic density which is a special region designed to respond to neurotransmitters released from the presynaptic terminal

Question 7

what happens after AP’s invade the presynaptic terminal?

Answer 7

AP invades the presynaptic terminal, resulting in the voltage gated Ca2+ opening, and a Ca2+ influx into the terminal

Question 8

how do voltage gated Ca2+ channels work?

Answer 8

they work just like any other voltage-gated ion channels (where they open when the membrane depolarises). Activation of voltage-gated calcium channels triggers neurotransmitter release

Question 9

excitatory postsynaptic potential (EPSP)

Answer 9

An excitatory response to a neurotransmitter

typically at spine synapses
causes small, transient depolarisation of the postsynaptic membrane (going from -60mV to -58mV for instance)

Question 10

Inhibitory postsynaptic potential (IPSP)

Answer 10

An inhibitory response to a neurotransmitter

typically at shaft synapses
causes hyperpolarization of the postsynaptic membrane (ex: -60 to -65 mV)

Question 11

describe the signaling order

Answer 11

electrical signaling (action potential) —> chemical signaling (neurotransmitters) —> electric signaling (continuation of the action potential

Question 12

Glutamate

Answer 12

an amino acid that is main excitatory neurotransmitter in the brain

Question 13

Rapid excitatory transmission at synapses is primarily due to ?

Answer 13

due to the actions of glutamate on two types of ionotropic glutamate receptors: AMAPA AND NMDA receptors which both tend to be present in the postsynaptic spine

Question 14

Ionotropic receptors

Answer 14

ion channels that open in response to binding of small molecules (neurotransmitters in this case) to receptor sites on the external surface

Question 15

AMPA receptors

Answer 15

responsible for the fast EPSP at excitatory synapses.
opens when glutamate binds to it and is also permeable to Na+ ions, depolarizing the postsynaptic spine
AT -70 mV almost all synaptic current at an excitatory glutamate synapse is carried by Na+ through AMPA receptors, but depolarization of the postsynaptic membrane causes a large flow of Ca2+ through NMDA receptors.