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Daily Warm-up
March 6th
What is the part of the neuron that receives
signals? Sends them?
HW:
-Read 37.3
Turn in:
-Nothing
Ions & Resting Potential
 Cell is negatively charged
compared to surroundings
 Difference is potential energy in
form of voltage
 Membrane potential= resting
potential when neuron is at rest
 Stimuli can change membrane
potential
Formation of Resting Potential
 Potassium ions (higher in the cell)
 Sodium ions (higher outside)
1. Sodium-potassium pump
 Active transport
 Transport Na+ out of cell and K+ into cell
 Three Na+ for two K+
 But only a few millivolts!!! So where is the charge coming
from?
2. Ion channels
What about the Ion Channels?
 Gradient favors outflow of K+
 Very few open sodium channels when at rest
 K+ outflow causes negative charge
When there is a stimulus…membrane
potential changes
 Action potential
 Changes occur because of gated ion channels
 Open or close in response to stimuli
 Hyperpolarization
 Cell becomes more negative
 Depolarization
 Cell becomes less negative
Two Types of Potential Change
1. Graded Potential- strength depends on
stimulus
2. Action Potential- all or nothing
-Constant magnitude
-Regenerate along neuron membrane
-Spread along axons
-Signaling
Action Potential
 Voltage-gated ion channels
 Open or close when membrane potential reaches threshold
 Depolarization of voltage-gated sodium channel?
 Positive feedback
 Potassium channel will open at end to return neuron to resting
state
Movement of the Signal
 Once area rises above
threshold have signal moving
Saltatory Conduction
Neuron-Neuron Communication
 Some can be electrical
signals, but most are
chemical
 Neurotransmitters
 Communication occurs at a
synapse