lesson10 - 10 Action Potentials and Synapses Key Terms and...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
10 Action Potentials and Synapses Key Terms and Concepts o Action potential propagation o Excitatory post- synaptic potential(EPSP) o Nodes of Ranvier o Inhibitory post- synaptic potential (IPSP) o Saltatory conduction o Temporal summation o Myelin o Spatial summation o Axon hillock o Neurotransmitter o Electrical synapse o Medulla oblongata o Connexon o Cerebellum o Gap junction o Hypothalamus o Chemical synapse o Cerebrum o Terminal button o Cerebral hemispheres o Pre- synaptic membrane o Cerebral cortex o Post- synaptic membrane o Frontal lobe o Synaptic gap/cleft o Parietal lobe o Vesicles o Temporal lobe o Graded potential o Occipital lobe Action Potential Propagation Action potentials spread along the neuronal membrane. This movement or propagation occurs because the polarity changes that occur at one point on the membrane are sufficient to open sodium channels of adjacent pieces of membrane. Return to your mental image of a neuron puffed up to the size of a balloon (Lesson 9). This neuron has a long axon and if you look closely you will see on the axon large numbers of red and white dots (the red dots represent voltage-gated sodium channels and the white dots represent voltage-gated potassium channels). If you looked closely enough at where the axon connects to the cell body (known as the axon hillock ) you would first see the red dots in the hillock open, followed shortly by the white dots in Lesson 10 123
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
the same area. As the first set of white dots begins to close you would see the red dots just down the axon begin to open, and so on down the entire length of the axon. Here’s another mental image. Imagine you are at a football game and half of the fans are wearing red shirts and half are wearing white. They are thoroughly intermixed. The game is lopsided and some fans in the student section decide to start the “wave.” As you know, the wave works because fans stand up just after the fans to their right stand up, then sit down again an instant later. The wave is a result of individual actions. Action potentials are like the wave at the football stadium in that the opening of sodium channels at one place triggers opening of sodium channels next to them in the “downstream” direction. But the action potential is a little more complicated because we also have potassium channels to consider. They are slightly delayed compared to the sodium channels, but essentially the red and white waves travel together from the axon hillock to the end of the axon. Later on we will cover the interesting events that transpire when the action potential reaches the end of the axon. In some axons, the opening and closing of ion channels occurs along the entire length of the axon because the sodium and potassium channels are “sprinkled” uniformly along the length of the axon. In other neurons, the action potential events recur periodically along the length of the axon, skipping places in between. In such axons an insulating material, myelin, is wrapped around the axon. (See the section on myelin, below).
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 05/27/2010 for the course BIOS 373 B02 taught by Professor Dr.danielleger during the Spring '10 term at UNL.

Page1 / 11

lesson10 - 10 Action Potentials and Synapses Key Terms and...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online