snail model system - courses.cit.cornell.edu...5.1 snail brain ganglia pedal (to foot) (tube through...

Snail Model System!

Intro to snails as a model system in neurobiology!

Our lab snail!

Pond snail brains!

ventral dorsal

Identified neurons in pond snail brains!

Snail Buccal Ganglia

Buccal ganglia neurons!

Smail Week 1. Firing properties of snail neurons!

Responses to current injection!

Firing Accomondation!

Post-inhibitory rebound!

Burster neurons!

Snail week 2. Ionic mechanisms of excitability!

Reduced Na! Reduced Ca!

K+ Channel block with TEA!

K+ Channel block with TEA/Cs!

TEA/CS block progressing over time (5 minutes)!

K+ Channel block with barium!

Excitability mechanisms: Voltage Clamp!Describing the ionic conductances underlying the AP!

Voltage clamp technique to examine ionic currents!

Problems analyzing conductances underlying AP!

! 1. ICm obscured IRm!

! 2. Conductances changed during AP!

Current across membrane!

Im = I Rm + ICm!

Ohm’s law for V-Clamp!

Ionic driving forces at rest!

Ionic driving forces at rest!

Current across membrane with

hyperpolarizations!

Im = I Rm + ICm!

Current across membrane with

weak depolarizations!

Current across membrane with

strong depolarizations!

INa!

IK!

Measure I!