Biology 1012  General Biology II

Chapter 45 Electrical Signals in Animals

I. Principles of Electrical Signaling

A. Information Flow in the Human Nervous System

1. Central Nervous System (CNS)

 

2. Peripheral Nervos System (PNS)

 

3. Information Pathways

a. reflex arcs

 

 

 

b. circuits through the brain

 

A. The Anatomy of a Neuron

1. Structure (draw and label a neuron)

 

B. An Introduction to Membrane Potentials

1. Membrane potential = electrical charge difference between inside and outside a cell.

a. potential energy (electric current created when ions move across the membrane)

 

b. Measuring membrane potentials

1. voltmeter with microelectrodes

2. measured in millivolts (mv)

 

c.

 

C. The Resting Potential

1. ion distribution

a. what ions are inside a neuron?

 

 

b. what ions are outside a neuron?

 

c. selectively permeable membrane

1. ion channels

 

potassium "leak" channels (which direction does it diffuse?)

 

 

2. Sodium/Potassium Pump (Na+/K+-ATPase)

restores high [K+] inside;  high [Na+] outside

 

d. How does the equilibrium potential set up?

 

Note: you can skip over the section on "Using the Nernst and Goldman Equations"

D. What Is an Action Potential?

Action Potential Definition:

 

Terms to understand:

depolarization

threshhold potential (-55mv)

repolarization

hyperpolarization

 

 

 

II. Dissecting the Action Potential

A. Depolarization -  Na+ ions in

B. Repolarization - K+ ions out

C. How do the ions move?

Voltage-Gated Channels

 

Patch Clamping to study electrical current flow caused by specifc ions through channels

D. Using Neurotoxins to Identify Channels and Dissect Currents

Puffer Fish

Black Mamba

E. The Role of the Sodium-Potassium Pump

F. How Is the Action Potential Propagated?

refractory period - prevents action potential from going backwards

 

the role of myelinated axons

Schwann cells

Nodes of Ranvier

saltatory conduction

Importance of myelination

III. The Synapse

A.  What happens when an action potential hits the end of an axon?

B.  Synapses

B. Neurotransmitters

Otto Loewi experiments

 

How do neurotransmitters work?

Presynaptic neuron

Action potential arrives

Calcium channels open; Ca++ diffuses in

Synaptic Vesicles fuse with presynaptic membrane

Neurotransmitter released by exocytosis

Neurotransmitter diffuses across synaptic cleft

Neurotransmitter binds with post-synaptic receptor

Opens post-synaptic ion channels

B. Postsynaptic Potentials and Summation

Excitatory postsynaptic potentials (EPSPs)

 

Inhibitory postsynaptic potentials (IPSPs)

 

Neurons communicate with many other neurons

 

Summation determines whether a new action potential is generated

IV. The Vertebrate Nervous System

A. A Closer Look at the Peripheral Nervous System

Afferent division

 

Efferent Division

 

Somatic system

 

Autonomic System

 

Parasympathetic Division

 

Sympathetic Division

B. Functional Anatomy of the CNS

Cerebrum

 

Diencephalon (mid-brain)

 

Cerebellum

 

Brain Stem

C. What do different areas do: 

1. Lesion Studies

Broca's area

 

Temporal Lobe

 

2. Electrical Stimulation of Conscious Patients

Penfield's epileptic studies

E. How Does Memory Work?

Recording from Single Neurons during Memory Tasks

 

Documenting Changes in Synapses