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Nervous System Cell Structure and Function

• Nervous system cells are called neurons
• Neurons communicate with each other via electrical signals
• Neurons have specific parts impacting communication

Neuron Parts and Structure

• Dendrites: Receive signals from other neurons
• Cell body (soma): Contains nucleus and other organelles
• Axon: Carries signals away from the cell body
• Myelin sheath: Insulates the axon, speeding signal transmission
• Nodes of Ranvier: Gaps in the myelin sheath
• Synaptic terminals (axon terminals): Release neurotransmitters to other neurons
• Synapse: The junction between neurons where neurotransmitters are passed

Communication Within a Neuron

• Action Potential: A rapid change in the electrical potential across the neuron membrane.
• Resting Potential: The electrical potential across the neuron membrane when it's not transmitting a signal. Typically around -70mV.
• Depolarization: The inside of the neuron becomes less negative, a shift towards zero, which leads to the action potential
• Repolarization: The inside returns to resting potential, becoming more negative
• Hyperpolarization: The inside of the neuron becomes more negative than the resting potential, a temporary dip in the potential below resting state.
• Threshold of excitation: The specific level of depolarization needed to trigger an action potential
• Ion channels: Protein channels that allow ions to pass through the membrane (ex: Na+, K+, Cl-) impacting polarization
• Sodium-Potassium pumps: Maintain the resting potential by moving Na+ out of the cell and K+ into the cell

Types of Neuron Communication

• Sensory neurons: Relay information from sensory receptors to the central nervous system.
• Motor neurons: Carry signals from the central nervous system to muscles or glands.
• Interneurons: Connect sensory and motor neurons within the central nervous system.

Reflex Arc & Withdrawal Reflex

• Reflex arc: A simple neural pathway that mediates a rapid, automatic response to a stimulus.
• Withdrawal reflex: A simple reflex in response to a painful stimulus to pull away the body part.

Conduction of Action Potential

• All-or-none law: An action potential either occurs or it doesn't. Strength does not differ.
• Rate Law: The level of stimulation will affect the frequency of action potentials
• Conduction/Propagation: Movement of the action potential along the neuron.
• Saltatory Conduction: Rapid signal transmission, specific to myelinated axons. Action potential jumps between Nodes of Ranvier, speeding up the propagation process

Summary of Action Potential

• The action potential is initiated when reaching a threshold of stimulation.
• The action potential has specific steps (depolarization, repolarization, hyperpolarization).
• Sodium ions flow into the axon which triggers an action potential.
• Following Sodium's influx, Potassium channels open to return back to normal potential.

Electrochemical Gradient

• Diffusion: Movement of ions from high to low concentration
• Electrostatic pressure: Opposite charges attract, same charges repel

Factors influencing membrane potential

• Sodium, potassium, and chloride ions are primary contributors