26 September 2008Finish Chapter 6 Section B Membrane Potentials

Begin Section C: Synapses

Test # 1 Monday (includes to Ch. 6B)Start promptly at 8:30 am (Get here early!)Test Study Guide to be posted to Website.

Figure 6.22

Action Potential conduction in non-myelinated axons(0.5 m/sec in small diameter unmyelinated axons)

Axon diameter and AP CVEnergy Requirements

Changes in concentration of Na+ and K+ only with long lasting period of high frequency action potentials.

Initial experiments with squid giant axon (1mm diameter) lead to knowledge of APs.

Figure 6.23

AP CV (up to 100 m/s)Location of channelsEnergy RequirementsAxon diameter

Who Cares?Multiple sclerosis and episodic

degeneration of myelin by immune disorder.

Important Information

End of Material For Test # 1

Begin Material For Test # 2

Figure 6.24Two categories of Synapses: Electrical (rare in nervous system) & Chemical

Figure 6.25UnidirectionalRelease, diffusion, binding,Post-synaptic Receptor Types: Inotropic or Metabotropic

Classification:Excitatory (closer to threshold for AP)OrInhibitory (stabilizes or hyperpolarizes)

Inotropic receptor Metabotropic receptor

Some ion channels are permeable to both Na+ and K+

Preview of coming attraction: the nicotinic Acetylcholine receptor so named for its agonist.

Synapses named for NT used: -ergic

Examples:CholinergicAdrenergicSerotonergicPeptidergic

Figure 6.27 Vesicle release proportional to Ca++ influx

Fates of neurotransmitters:1) Diffusion away from synapse,2) Enzymatic degradation (e.g. AChE and MAO)3) Reuptake into presynaptic terminal (SSRI)

Tetanus toxin & Botulinum toxin disrupt SNARE function.

Figure 6.28

EPSPs :which ion moving in which direction?Duration of PSP vs APSynaptic delay

Ion Channels that allow flux of Na+ and K+ simultaneously.

Figure 6.29

IPSPs :which ion moving in which direction?

Some IPSPs result in no change in membrane potential by opening Chloride channels that stabilize membrane potential at resting value or in cells that actively transport Cl- out.

Figure 6.31

Summation and Synaptic Integration