Neurons and Neural Communication

Behavioral Neuroscience Overview

• Introduction to behavioral neuroscience focusing on the cellular level of the nervous system.

• Key topic: Neurons - the fundamental units of the nervous system.

Neuron Structure

• There are five primary structural elements of a neuron:

  • Axon:

  • Usually singular (one per neuron) but can fork.

  • Function: Sends messages away from the cell body.

  • Dendrites:

  • Multiple per neuron (thousands may branch out).

  • Function: Receive incoming information (information collectors).

  • Soma (Cell Body):

  • Acts as the hub of the neuron.

  • Function: Keeps neuron alive and coordinates cell processes (nutrient transport, waste disposal).

  • Axon Terminals (Terminal Boutons):

  • Branches at the end of an axon.

  • Function: Communicate with other neurons (neurotransmitter release).

  • Myelin Sheath:

  • Insulating layer around the axon.

  • Composed of glial cells, speeds up neuronal communication.

Neural Communication Within Neurons

• Communication is often described as an electrical process.

• Involves the movement of ions (charged particles) across the neuron's membrane.

• Resting Potential:

  • Neuron's voltage when at rest, typically around $-70 ext{mV}$.

  • More negatively charged ions inside than outside.

• Neuron can undergo depolarization (movement closer to zero, upwards movement) and hyperpolarization (increased negativity, downward movement).

• An action potential occurs when sufficient depolarization happens, flipping the neuron's charge.

  • Threshold for action potential: between $-60$ and $-65 ext{mV}$.

  • Characteristics:

  • Rapid reversal of charges, peaking at about $+30 ext{mV}$.

  • Follows an all-or-none law: neuron either fires completely or not at all.

Communication Among Neurons: Synapses

• Synapses are the junctions between neurons, filled with a small gap.

• Process of Synaptic Transmission:

  1. Action potential reaches the axon terminal.

  2. Release of neurotransmitters from vesicles into the synaptic cleft.

  3. Neurotransmitters bind to receptors on the postsynaptic neuron (dendrites).

  • Can either depolarize (excitatory) or hyperpolarize (inhibitory) the postsynaptic neuron.

• Excitatory Neurotransmitters: Promote depolarization, encourage the firing of the postsynaptic neuron (e.g., glutamate).

• Inhibitory Neurotransmitters: Promote hyperpolarization, discourage firing of the postsynaptic neuron (e.g., GABA).

• Example of neurotransmitter release:

  • When an action potential arrives:

  • Vesicles containing neurotransmitters move to the membrane, release into the synapse.

Synaptic Cleansing

• After neurotransmitter action, they are often sucked back up into the presynaptic neuron, a process known as reuptake.

• Ensures neurotransmitters are recycled properly and prevents overstimulation of receptors.

Importance of Neural Communication

• All sensory processes (vision, hearing, etc.) rely on neuronal communication.

• Motor function and voluntary muscle activation depend on effective neurotransmission.

• Disruption of neurotransmission can lead to conditions such as paralysis or sensory deprivation.

Implications for Health

• Psychological medications work by affecting neurotransmitter levels and receptor activity.

• Example: Excess excitation or inhibition can lead to mental health disorders.

• Understanding neurotransmission may also lead to therapeutic advancements (e.g., treatment for depression, anxiety).

Conclusion

• The interplay between neuronal structure and function underlies all behaviors, thoughts, and emotional responses.

• Further study in this field can illuminate the complexities of human behavior and potential treatment strategies for mental and physical disorders.