Signal Circuits and Coding

microelectrode

A ______________ measures the voltage inside the cell.

defined as zero

A ground wire measures the voltage outside the cell (this value is ___________________)

amplifier

An _________ reports the difference to an oscilloscope or computer for display.

membrane potential (Vm)

The general term for the voltage difference across the plasma membrane is ______________________.

penetrates neuron

what does the blue box represent?

Signals

what does the green box represent?

information

what does the yellow box represent?

Depolarization

What does the orange box represent

Hyperpolarization

what does the purple box represent?

Resting Membrane Potential (RMP)

what does the pink box represent

Graded

what does the pink question mark represent?

Action

what does the yellow question mark represent?

Graded Potential

1. often small (less than 10mV change in Vm)

2. Hyperpolarization or Depolarization

3. Graded in amplitude

   1. amplitude coding of stimulus intensity

4. Graded in Duration

   1. code for stimulation with their duration

5. local - decay with distance from the site of initiation - dissipate within about 1mm

6. triggered by external energy or chemicals

7. Occur in:

   1. Sensory nerve endings - Receptor potential Transduced from external energy [light (vision), pressure (touch), vibration (hearing), or chemicals (smell and taste)]

   2. Dendrites, soma, or axons - synaptic potential induced by a chemical neurotransmitter

Action Potentials (Impulses or spikes)

1. A large change in Vm

   1. peak depolarization overshoots 0mV

2. Peak is depolarizing only

3. Fixed amplitude (all-or-none)

   1. frequency coding of stimulus intensity

4. Fixed duration (1-3msec)

   1. Code for stimulus duration with burst duration -how long was the cell firing?

5. Propagated (do not decay with distance) along the axon

6. Triggered by depolarizing graded potentials that cross a Vm threshold

7. Sodium-based spikes occur primarily in axons

8. Calcium-based spikes can occur in some dendrites