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) 1. Sensory Neuron Interneuron (Integration) 2. Interneuron 3. Motor Neuron Motor Pathway Effector Tissue

3 Types of Functional Neurons: 1) Sensory (in) 2) Interneurons (processing) 3) Motor (out) Which neuron is the most numerous?

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

Equilibrium Potentials: - Na+ - K+ Resting Membrane Potential (RMP) for cells

Graded Potentials Action 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 Large Diameter Vs. 2. Temperature 3. Axon Myelination

The Biochemistry of the Synapse

2 ways the Post-Synaptic cell Responds

Post-Synaptic Cell Responses Ionotropic Effect Metabotropic Effect

Stopping Signal Transmission Stop the Impulse (Stop 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.

Clearing up the synaptic cleft

Degrading NT’s into non-stimulating fragments and Recycling into pre-synaptic neuron.

Agonists: Signal molecules that bind the receptor and induce the post-receptor events that lead to a biological effect. They act like the normal or true ligand (signal molecule), though potency may vary. Antagonists: Signal molecules that bind the receptor and block binding of the true ligand or agonist, and fail to trigger intracellular signaling events.

Agonists Antagonists

Benzodiazepines are tranquilizers. e.g. Valium (diazepam) and Xanax (alprazolam), etc. for anxiety, insomnia…

Yum Yum Foods that Stimulate GABA Production in CNS: Almonds Bananas Beef Liver Broccoli Brown Rice Green Tea Halibut Lentils Oats, whole grain Oranges, citrus fruits Rice bran Spinach Walnuts Yum Yum

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 6 Different Glial Cells

2 Glial Cells of the PNS 1. Schwann cells – create the myelin sheath for axons in the PNS. Many Schwann cells help to myelinate axon. 2. Satellite cells - small cells that surround neurons ganglia in PNS. Act to protecting and repair ganglia.

4 Glial Cells of the CNS 3. Oligodendrocytes - create the myelin sheaths of axons in CNS, providing insulation, allowing signals to propagate faster. 4. Astrocytes – help create the restrictive blood-brain barrier (BBB), to protect delicate nervous tissue. 5. Microglia - phagocytic (like macrophages), acting as defense cells in CNS. Cells multiply if CNS is damaged or infected. 6. Ependymal cells - line fluid cavities of the CNS (e.g. ventricles and central canal). They help create and secrete cerebrospinal fluid (CSF).