Electrical signals in neurons
Cell-to-cell communication
Integration of neural information transfer

CNS

Afferent- Things moving toward
Efferent- Things moving away
Nerves that are firing towards (afferent) or away (efferent) from the CNS

Includes the brain and spinal cord
FUNCTIONS: Receives, processes, and transfers information

PNS

Includes:
Autonomic neurons
Automatic
Sympathetic and parasympathetic
Somatic motor neurons
Control of skeletal muscles

1. Central Nervous System
2. Peripheral Nervous System

Functions:
Rapid communication for homeostatic balance
Properties of intelligence, consciousness & emotion, and memory

PNS

The nerves and Ganglia outside of CNS

Includes:
Sensory neurons- carry info toward CNS
Motor neurons- carry info away from CNS
Nerves- Bundles of axons
Ganglia- Collections of nerve cell bodies; create swelling in nerves

Basic functional unit of nervous system
Cell body site of energy generation and synthesis
For communication in the NS
Includes a:
Cell body
Dendrites
Axon
Terminal
Myelin Sheath

Neurons- Transmit communication signals
Communication
Glial Cells- Support neurons
Support, protection, myelin formation
* the cells that become TUMORS

Found in CNS and PNS
Support neuron bodies, form myelin sheaths
Involved in cleaning up dead cells and fixing cell connections
barriers between compartments
Scavenger/defense and metabolic assistance
FIG 8.5 IN BOOK

A section of unmyelinated axon membrane between two schwann cells

Outnumber neurons 10-50X
do NOT conduct signals
provide physical support for neurons (direct growth and repair)
Form myelin sheaths
Acts as insulator
Increases speed

1. Schwan cells- Myelin production
Areas of non-insulated Nodes of Ranvier
2. satellite cells- Supporting cells around ganglia
no myelin

1. Oligodendrocytes- wrap around neurons, support, and insulate with myelin
2. Astrocytes- Contact neurons and blood vessels, transfer nutrients
3. Microglia- Specialized macrophages remove damaged cells

Ionic concentrations and potentials

For an ion to move it needs incentive and opportunity

EX: I want to leave and go to lunch during class (incentive), but I can't leave in the middle of class (no opportunity)

1. Gated Channels
2. Graded Potentials
3. Action Potentials

Channel opens in response to stimuli
Keeps things that aren't lipophillic away from fats
Controls permeability
Types:
1. Mechanically Gated- Physical factors stimulate opening, pressure, and stretch
2. Chemically Gated- Ligand stimulates (neurotransmitters, neuromodulators)
3. Voltage Gated- Membrane potential changes stimulate opening

Localized, variable in size, dissipates
Dissipates due to:
1. Positive charge leakage
2. Cytoplasmic resistance

Incoming (input) signals
vary in strength
decreased strength over distance
slower moving than action potentials (AP)
travel to trigger zone and integration occurs

Sub-threshold: too weak, no AP
Supra-threshold: Generation of AP

All or none
Spontaneous or graded potential initiates
START at trigger zone
Signal does NOT diminish with distance

Initiation
Depolarization
Signal Peak
Repolarization
Hyperpolarization

Compromised ability to stimulate AP's
Two Types:
1. Absolute Refractory Period
1/1000th of a second you are in this period
2. Relative RP
this period is larger

Na+ inactivation channel limits Na+ entry, K+ channel returns polarity to normal

Control of Speed
Can change the frequency with which we see the AP's
Firing rate- "wave of AP's"
Proportional neurotransmitter (NT) release
Stronger Graded Potential (GP)
aka stimulus= more AP's and more NT

Change the speed by diameter of the axon
larger is faster
axon myelination increases speed(creates saltatory conduction)
Voltage gated channels only in nodes of Ranvier