Do Now 1/9/15 1.Name 3 glial cells and describe their function and location. 2.Which neural pathway transmits a signal when the internal body temperature is too high? 3.What is the difference between the somatic and the autonomic branches of the nervous system? 4.What is resting membrane potential?

Resting Membrane Potential

Neuron has an overall -70 mV charge K+ ion concentration is higher INSIDE the neuron K+ will want to leave the neuron if it can Na+ ion concentration is higher OUTSIDE the neuron Na+ will want to enter the neuron if it can Channels are closed so the ions cannot diffuse… yet…

How does a neuron go from resting to firing? The resting membrane potential of a neuron is -70 mV In order for a neuron to fire a signal, the membrane potential must reach a certain threshold, around -55 mV. This happens when another neuron stimulates it and allows a few Na+ channels to open and a few Na+ ions enter the axon

Action Potential When neurons FIRE! Caused by the rapid opening and closing of voltage-gated channels Transfer information from one place to another in the nervous system

How do action potentials start? A neuron is electrically stimulated in some way From a sensory experience (sensory neurons) Accumulated electrical potentials in the dendrites From an outside electrical signal The result of any of these electrical stimulations is the opening of Na+ ion channels Which direction will the Na+ ions want to go? What effect will the diffusion of Na+ ions have on the overall charge of the neuron?

Membrane Potential Graph 1.Resting Na+ channels closed

Membrane Potential Graph 2.Threshold When the membrane potential reaches the threshold, the Na+ channels open, allowing more Na+ to enter the neuron

Membrane Potential Graph 3.Depolarization The Na+ channels are open and Na+ is rapidly flowing into the neuron, causing the membrane potential to become more positive

Membrane Potential Graph 4.Peak The Na+ channels are closed 5.Repolarization The extra K+ channels are opened. K+ ions rush out of the neuron, causing the membrane potential to become more negative

Membrane Potential Graph 6.Hyperpolarization and return to Resting K+ channels continue to be open until the membrane potential reaches the voltage of resting membrane potential. K+ close and resting membrane potential is maintained

How does the action potential work?

1.Describe the movement of potassium and sodium ions during an action potential. 2.What must happen before sodium can rush into the axon? 3.Why does potassium leave the neuron during repolarization? 4.Summarize the process of an action potential.

Jumpin the (Synaptic) Gap 1. What structure is responsible for “recycling” neurotransmitters back into the axon terminal once they have done their job? 2. How do the vesicles “know” when to move to the membrane to dump their contents into the synapse? 3. How does the message continue past the post-synaptic membrane?

Excitatory Post-Synaptic Potential (EPSPs) & Inhibitory Post-Synaptic Potentials (IPSPs) Neurotransmitters released into the synaptic gap can either be excitatory or inhibitory Excitatory – makes the next neuron more likely to fire (more +) Inhibitory – makes the next neuron less likely to fire (more -) Post-synaptic potentials are graded potentials They have an additive effect When multiple PSPs occur at the same place, the combined effect is the sum of all of them The combination of EPSPs and IPSPs must reach threshold in order for the next neuron to fire ations05.02.html