Physiology Chapter 2-Synapses and neuronal integration Flashcards
What three structures can a neuron terminate on?
A neuron, muscle or gland.
What happens when the action potential reaches the axon terminals?
The axon terminals release a chemical messenger that alters the sodium-potassium pump activity of the cells on which the neuron terminates.
When a neuron terminates on a muscle or gland, the neuron is said to ________ the structure.
Innervate
What are synapses?
Typically, involves a junction between an exon terminal of one neuron, known as the presynaptic neuron, and the dendrites or cell body of a second neuron, known as the postsynaptic neuron.
What is the synaptic knob?
A slight swelling at the end of the axon terminal of the presynaptic neuron.
The synaptic knob contains synaptic vesicles.
The synaptic knob comes into close proximity to, but does not actually directly touch the postsynaptic neuron.
What is the postsynaptic neuron?
The neuron whose action potentials are propagated away from the synapse.
What are synaptic vesicles?
Store a specific chemical messenger, a neurotransmitter that has been synthesized and packaged by the presynaptic neuron.
What is the synaptic cleft?
The space between the pre- and postsynaptic neuron;
Why does current not directly spread from the presynaptic membrane to the postsynaptic neuron?
No channels are present in the presynaptic membrane for passage for sodium and potassium.
How then, does an action potential propagate between neurons?
Instead, an action potential in the presynaptic neuron alters the postsynaptic neuron’s potential by chemical means.
What occurs when an action potential in a presynaptic neuron has been propagated along the axon to the axon terminal?
The local change in potential opens voltage-gated calcium channels in the synaptic knob.
What are voltage-gated calcium channels?
Class of trans-membrane ion channels tat are activated by changes in electrical potential.
Calcium channels are critical in neurons, and are common in other cell types.
When the voltage-gated calcium channels open, what occurs?
Calcium is much more concentrated in the ECF and the electrical gradient favours its movement into the cell through the channels.
Calcium induces the release of a neurotransmitter from the synaptic vesicles into the synaptic cleft by exocytosis.
Once the neurotransmitter is released, what happens?
It diffuses across the cleft and binds with specific protein receptors on the subsynaptic membrane.
What is the subsynaptic membrane?
Postsynaptic membrane directly below the synaptic knob.
