The Control Systems of the Body Local Control

The Control Systems of the Body Local Control Autocrine Paracrine Long Distance Control Endocrine System Slower Response, Broad, Long Lasting Nervous System Faster Response, Specific, Brief

The Nervous System • Overview • Neurophysiology • Central Nervous System • Peripheral Nervous System – Autonomic N. S. – Somatic N. S.

Overview of the Nervous System

PNS CNS Sensory Pathway Receptors Interneuron (Integration) Motor Pathway Effector Tissue

A Typical Neuron • Dentrites incoming info. • Cell Body integration of info. • Axon outgoing info. • Axon Terminal with End Bulb release of neurotransmitter Nodes of Ranvier

Graded Potentials Localized change in membrane potential that varies in magnitude and is decremental. Action Potentials Rapid reversal in membrane potential (due to changes in ion permeability), with constant magnitude and is non-decremental.

Action Potentials • "All or none" event • Signal does not diminish over distance There are 4 Phases in an Action Potential: 1. Threshold 2. Depolarization 3. Repolarization 4. Hyperpolarization

Refractory Periods • Absolute Refractory Period: • Relative Refractory Period:

Summation of Graded Potentials • Temporal Summation: As the frequency of a single stimuli increases, the changes in membrane potential can be added and its magnitude can increase. • Spatial Summation: 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 1. Magnitude varies 1. No variation - All or None 2. Decremental (passive spread) 2. Non-decremental (self-regenerating) 3. No Refractory Periods in Graded Potentials 3. Two Refractory periods: Absolute and Relative 4. Summation is possible 4. No Summation possible 5. Trigger: NT's, hormones 5. Trigger: Threshold 6. Occurs at cell body (direction can vary) 6. Occurs at axon hillock (one way direction)

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 • Temperature • Axon Myelination • Large Diameter

The Biochemistry of the Synapse

Stopping Signal Transmission • Stop the Impulse (Pre-Synaptic AP) • Clear Away the Synaptic Cleft – 1. Diffusion away from Receptors. – 2. Enzymatic Degradation of NT. – 3. Re-uptake of NT by Pre-Synaptic cell.

Post-Synaptic Cell Responses • Ionotropic Effect • Metabotropic Effect

Neuronal Pathways • Divergent:

Neuronal Pathways • Convergent:

Pre- and Postsynaptic Inhibition and Facilitation The Presynaptic terminal Inhibitory neuron(s) – less NT released Excitatory neuron(s) – more NT released The Postsynaptic membrane and receptors - Receptor numbers - Degradation rates - Permeability

The Different Glial Cells