L9 and 10 Unit 11

Synapse

The region of contact where a neuron transfers information (a nerve impulse) to another neuron or muscle.

Presynaptic Neuron

First neuron, axon terminal, transfers nerve impulse to next neuron.

Postsynaptic Neuron

Second neuron, dendrite, receives nerve impulse from presynaptic neuron

Synaptic Cleft

Space between pre and postsynaptic neuron,, filled with matrix, helps neurons adhere to each other.

Neurotransmitters

Chemical that an axon terminal releases to cause the transfer of a nerve impulse to another neuron or a muscle fiber, used to communicate with postsynaptic neuron.

Protein Channels

On postsynaptic membrane, allow ions to enter.

Calcium Protein Channels

On sides of axon terminal.

Calcium (Ca2+)

In extracellular fluid

Sodium (Na+)

Mainly in extracellular fluid (which is in the synaptic cleft)

Chlorine (Cl-)

In the extracellular fluid (which is in the synaptic cleft), is the negative ion

Excitatory neurotransmitters

Type of neurotransmitter that WILL continue the nerve impulse to the next neuron or muscle

Inhibitory neurotransmitters

Type of neurotransmitter that will NOT continue the nerve impulse to the next neuron or muscle

Synaptic Transmission

Process by which the nerve impulse in the presynaptic neuron signals the postsynaptic cell so the nerve impulse can continue.

Process of a synapse

Action potential travels down axon to axon terminal, causes calcium protein channels to open, Ca2+ rushes in from extracellular fluid, calcium rushing in triggers synaptic vesicles to fuse to presynaptic membrane, synaptic vesicles open and spill out neurotransmitters into synaptic cleft, neurotransmitters bind to proteins channels on postsynaptic neuron, stimulate protein channels to open to allow in Na+.

If neurotransmitter EXCITATORY(EPSP

Na+ goes into cell, it causes depolarization in the postsynaptic membrane, this causes the neuron to become positive and action potential continues - nerve impulse continues!

If neurotransmitter INHIBITORY (IPSD)

Causes chlorine to rush in, which causes hyperpolarization (away from threshold, opposite), change in membrane potential causes the membrane to be “inhibited”, no action potential triggered.

Reuptake of Neurotransmitter

After the neurotransmitter has done its job in the synaptic cleft, it is taken care of by one of three ways: diffuses into extracellular fluid, an enzyme comes in and decomposes it, or transported back into the synaptic vesicles of the axon terminal. Called REUPTAKE.

Electrical to Chemical to Electrical

The nerve impulse goes from an electrical signal down the axon, to a chemical signal in the synapse, back to an electrical signal down the next neuron.