1. Chapter 48

2.  Short distance communication ◦ Synapses between cells  Neurotransmitters

3.  Detection of a stimulus ◦ Internal or external  Transmit and integrate information  Generate a response

7.  The gap between the axon of one neuron and the dendrites or cell body of the next neuron.  When the impulse reaches the end of the axon, chemicals called neurotransmitters are released and carry the impulse to the next neuron.

10.  Action Potential ◦ Electrical signal that travels on the membrane of a neuron ◦ Based on movements of ions between the outside and inside of the cell

11.  Na + and K + channels closed Inside membrane is slightly – Outside membrane is slightly + Most membrane channels are closed, there is some normal diffusion of K + or Na + between cell and the environment through the sodium/potassium pump (active transport)

12.  Stimulus causes some sodium channels to open Sodium (Na+) channels open allowing Na+ to diffuse into the cell quickly This causes the inside to become + (outside -) If depolarization reaches threshold, action potential triggered

13.  Depolarization continues, opening most sodium channels  Potassium channels remain closed Inside membrane now + with respect to the outside

14.  Sodium channels become inactivated, blocking Na+ inflow.  Potassium channels open, permitting K+ outflow  Inside membrane now - again

15.  Sodium channels remain closed, some potassium channels open allowing potassium to flow out  K+ gates open in order to allow K+ to diffuse out of the cell – this restores the membrane (+ outside, - inside)  Refractory period – “downtime” when neuron cannot fire if stimulated

16. Action potential Threshold Resting potential Time Membrane potential (mV)  50  100  50 0 123451

17.  http://video.google.com/videoplay?docid=- 6890770586678681705&ei=3qb9SqPxO5_ar QKQp-inBA&hl=en# http://video.google.com/videoplay?docid=- 6890770586678681705&ei=3qb9SqPxO5_ar QKQp-inBA&hl=en#  http://outreach.mcb.harvard.edu/animations /actionpotential.swf http://outreach.mcb.harvard.edu/animations /actionpotential.swf  http://video.google.com/videoplay?docid=- 6890770586678681705&ei=3qb9SqPxO5_ar QKQp-inBA&hl=en#docid=- 4821246047499143591 http://video.google.com/videoplay?docid=- 6890770586678681705&ei=3qb9SqPxO5_ar QKQp-inBA&hl=en#docid=- 4821246047499143591

18.  Impulses are able to cross the synapse to another nerve ◦ Neurotransmitter is released from a presynaptic nerve’s axon terminal ◦ The dendrite of the next neuron has receptors that are stimulated by the neurotransmitter ◦ An action potential is started in the post-synaptic dendrite ◦ http://highered.mcgraw- hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/007243 7316/120068/bio02.swf::Endocytosis%20and%20Exocytosis http://highered.mcgraw- hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/007243 7316/120068/bio02.swf::Endocytosis%20and%20Exocytosis