Electrical Signals 1

BIOL 1407

Electrical Signals

• Changes in membrane potential currents

• Used by cells for quick communication

Chemical vs. Electrical Signaling

• Type of Signals– Chemical – Electrical + Chemical = Electrochemical

• Types of Chemicals Used– Hormones– Neurotransmitters

Chemical vs. Electrical Signaling

• Speed of Transmission– Slow– Fast

• Duration of Response– Long– Short

Functions of Nervous Systems

Neuron

• Cell body = Soma• Dendrites• Axon

– Axon Hillock– Axon Terminals =

Synaptic Knobs = Synaptic Terminals

Types of Neurons

Supporting Cells = Neuroglia

Schwann Cells

Neural Pathways Example

Membrane Potential

• Electrical Difference = Potential• Membrane at Rest = Resting Membrane Potential (RMP)

Membrane Proteins

• Sodium Potassium Pump– Maintains Resting Membrane Potential

• Leak Channels– Na+ and K + Leak Channels

• Chemically-Regulated (Gated) Channels– Also called Ligand-Gated Channels

• Voltage-Regulated (Gated) Channels– Na+ and K + Voltage-Regulated Channels

• Chemically-Regulated Channels

• Gated• On dendrites and cell

body• Responds to

chemicals• Graded potentials

• Voltage-Regulated Channels

• Gated• On axons• Respond to changes

in voltage• Action potentials

(APs)

Voltage-Regulated Na+ ChannelNa+ Channel is Closed and Activated

Na+ Channel is Open; Stays Open for Short Amount of Time

Na+ Channel is Closed and Inactivated

Voltage-Regulated K+ Channel

K+ Channel is Closed

K+ Channel is Open

Changes in Membrane Potential

• Resting Membrane Potential (RMP)• Depolarization

– Membrane becomes more + than RMP

• Hyperpolarization– Membrane becomes more – than RMP

• Action Potential: pattern of MP changes– Depolarization– Repolarization– Undershoot: Brief Hyperpolarization

Changes in Membrane Potentials

Graded Potentials

• Occur at dendrites and cell bodies

• Response to changes in chemically-regulated channels

• Strength diminishes over distance

• Vary in strength

Graded Potentials

• Can be depolarizing event or hyperpolarizing event

Action Potentials

• Occur only along axons

• Strength is always the same

• Strength of signal stays the same along the entire length

• All-or-none

Threshold Stimulus

• Threshold Stimulus – Enough depolarization to generate an AP – Usually -55 mV

• Subthreshold Stimulus – Insufficient depolarization to generate an AP

The End

Unless otherwise specified, all images in this presentation came from:

Campbell, et al. Biology, 7th ed. and 8th ed. Pearson Benjamin Cummings.