Neuro205 Exam 1 Study Guide 5

Define synapse and what happens at a synapse

• a junction between neurons where impulses pass by neurotransmitter diffusion

Define the structure of an electrical synapse, how electrical synapses work, and where they are typically found in humans

• an electrical synapse is a connexon that is made up of 6 connexins

• They allow for the passive diffusion of ions and small molecules

• Common in early development

• Found in glial cells, inhibitory neurons, and some excitatory neurons

Describe the structure of a typical chemical synapse (include presynaptic terminal, synaptic vesicles, NT, active zone, postsynaptic membrane, NT receptors, extracellular matrix in the synaptic cleft)

Presynaptic terminal: sends signal

Synaptic vesicles: release neurotransmitters

NT: what pre synaptic cell sens to post synaptic cell

Active zone: the area where vesicles bind to the membrane

Post synaptic membrane: receives signal

NT receptors: NTs bind to them and they’re on the postsynaptic membrane

Extracellular matrix in synaptic cleft: in between the pre and post synaptic membranes

Explain the difference between axodendritic, dendrodendritic, axosomatic, and axoaxonic synapses

Axodendritic: axon→dendrite

Dendrodendritic: dendrite→dendrite

Axosomatic: axon→soma

Axoaxonic: axon→axon

Diagram and label the structures found at a neuromuscular junction (include presynaptic terminal, synaptic vesicles, acetylcholine, active zone, motor end-plate, junctional folds, acetylcholine receptors, extracellular matrix in the synaptic cleft, acetylcholine esterase)

Describe where these types of neurotransmitters are created and stored (amine/amino acid NT, and peptide NT)

Amine/amino acid NT are synthesized in the synaptic terminal and stored in synaptic vesicles

Peptide NT are synthesized in the rough ER (and modified in the Golgi) and stored in the secretory granules (carried down the microtubules)

Explain the trigger and basic mechanisms of neurotransmitter release

Describe the basic structure and action of transmitter-gated ion channels (These are neurotransmitter IONOTROPIC receptors)

1. neurotransmitter binds to the receptor

2. Channel opens

3. Ions flow across membrane

Explain the difference between excitatory and inhibitory synapses

• excitatory:

  • Tend to be on or around dendrites

  • Really powerful ones on the soma

  • EPSP: membrane depolarized; glutamate; influx of cations (excitatory postsynaptic potential - if enough add up it becomes an action potential in that neuron)

• Inhibitory:

  • Tend to be in the soma and axon hillock

  • They “shut down” the dendrite or cell

  • IPSP: membrane hyperpolarized; GABA; influx of anions/efflux of cations (Inhibitory postsynaptic potential)

Explain the functions of metabotropic receptors (G-protein-coupled receptors)

Not as direct as an ionotropic receptor (the ion neurotransmitter gated channels)- the neurotransmitter binds and then that activates the G protein, which can do one of 2 things

The shortcut approach (this is fast, and direct, but perhaps doesn’t have as widespread of reach) - the G protein directly goes and opens or closes an ion channel (exciting the neuron or inhibiting it)

Or the second messenger approach where the G protein activates enzymes which produce second messengers that amplify the signal and leads to longer lasting effects

Describe the function and location of autoreceptors

• Location: presynaptic neuron

• Function: modifies release of neurotransmitters based on how much there is in the cleft- sort of regulation