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Chapter 3
The Synapse
Question | Answer |
---|---|
What is a chemical synapse? | A synapse where communication occurs by neurons sending neurotransmitters across the synaptic gap. |
What is an electrical synapse? | A synapse where communications occurs by neurons sending ions through gaps where the channels actually touch. |
What is the difference between how an electrical synapse functions vs the chemical synapse? | 1. The gap between pre- and postsynaptic cells are quite small: 3.5 nm vs 20 nm 2. The pre and postsynaptic cells are actually joined by protein channels that allow positive current from the presynaptic neuron to flow into the post one |
What are the advantages and disadvantages of electrical synapses?` | They are fast: transmission nearly instantaneous. However, they can only send excitatory or inhibitory messages. Also, it takes a very large presynaptic neuron to influence a tiny postsynaptic neuron as signal strength decreases in transmission. |
Where are electrical synapses found? | In the circuits responsible for escape behaviours. They also synchronise activity like the release of hormones in response to activity in the hypothalamus. |
What happens during signalling at chemical synapses? | 1. AP arrives at terminal; Ca2+ channels open 2. Ca2+ moves in during hyperpolarization and frees vesicles from microtubules 3. Vesicles move to release sites and release their contents 4. Ca2+ pumps pump Ca2+ out, vesicle recycled |
What is exocytosis? | The process by which vesicles release their contents. |
What are autoreceptors? | They are protein structures on the presynaptic membrane that bind some neurochemicals released and provide feedback to the neuron about its activity. |
What are EPSPs and IPSPs? | EPSPs increase the likelihood that the postsynaptic cell will fire. IPSPs decrease it. |
What are the similarities between EPSPs and IPSPs? | Both are graded potentials, meaning that they vary in size and shape. EPSPs result from the opening of ligand-gated sodium channels in the postsynaptic membrane, while IPSPs are produced by chloride or potassium ligand-gated channels. |
What is neural integration? | The process by which the neuron sum all of the input from other neurons in order to determine if it will generate an action potential. |
Where does the neuron receive excitatory and inhibitory input? | Excitatory input is received from dendrites and their spines. Inhibitory input is received from synapses on the cell body. |
What is spatial summation? | Input from all over the cell converges at the axon hillock. The neuron combines this input and if the axon hillock is depolarized to 5 mV the cell will fire. |
What is temporal summation? | At a very active synapse, EPSPs and IPSPs can build on one another at a very active synapse. This activity triggers the cell to fire. |