Local Control

The Control Systems of the Body

Long Distance Control

Autocrine -

Paracrine -

Endocrine System

Nervous System

Slower Response, Broad, Long Lasting

Faster Response, Specific, Brief

• Overview

• Neurophysiology

• Central Nervous System

• Peripheral Nervous System– Autonomic N.S.– Somatic N.S.

The Nervous System

Overview of the Nervous System

Sensory Pathway

Motor Pathway

Interneuron(Integration)

CNSPNS

Receptors

EffectorTissue

• Dentrites

• Cell Body

• Axon

• Axon Terminal

with End Bulb

A Typical Neuron

incoming info.

integration of info.

outgoing info.

release of neurotransmitter

Nodes ofRanvier

Graded Potentials

Action Potentials

Localized change in membrane potential that varies in magnitudeand is decremental.

Rapid reversal in membrane potential (due to changes in ionpermeability), with constant magnitude and is non-decremental.

• "All or none" event

• Signal does not diminish over distance

1. Threshold

2. Depolarization

3. Repolarization

4. Hyperpolarization

Action Potentials

There are 4 Phases in an Action Potential:

Refractory Periods

• Absolute Refractory Period:

• Relative Refractory Period:

Summation of Graded Potentials

• Temporal Summation:

• Spatial Summation:

As the frequency of a single stimuli increases, the changes in membrane potential can be added and its magnitude can increase.

As multiple simultaneous stimuli occur at different places on the neuron, the changes in membrane potential can be added and its magnitude increased or decreased.

Graded vs. Action Potentials

2. Decremental (passive spread)

2. Non-decremental

(self-regenerating)

3. No Refractory Periods

in Graded Potentials

4. Summation is possible 4. No Summation possible

5. Trigger: NT's, hormones 5. Trigger: Threshold

1. Magnitude varies 1. No variation - All or None

6. Occurs at cell body

(direction can vary)

6. Occurs at axon hillock (one way direction)

3. Two Refractory periods:

Absolute and Relative

How fast can a signal travel down an axon?

Speed of Conduction of Signal

• Small Diameter • Large Diameter

Speed of Conduction of Signal

• Small Diameter • Large Diameter

• Temperature

• Axon Myelination

The Biochemistry of the Synapse

Stopping Signal Transmission

• Stop the Impulse (Pre-Synaptic AP)

• Clear Away the Synaptic Cleft

– 3. Re-uptake of NT by Pre-Synaptic cell.

– 1. Diffusion away from Receptors.

– 2. Enzymatic Degradation of NT.

• Ionotropic Effect

• Metabotropic Effect

Post-Synaptic Cell Responses

• Divergent:

Neuronal Pathways

• Convergent:

Neuronal Pathways

The Presynaptic terminalInhibitory neuron(s) – less NT releasedExcitatory neuron(s) – more NT released

The Postsynaptic membrane and receptors- Receptor numbers- Degradation rates- Permeability

Pre- and Postsynaptic Inhibition and Facilitation

The Different Glial Cells