Lecture Notes on Neuron Function and Communication

Key Components of Neuron Structure and Function

Somas and Dendrites

• Gates: Ligand-gated channels.
• Potential Types: Graded potentials (GPs) occur here.

Axons

• Gates: Sodium and potassium voltage-gated channels.
• Potential Types: Action potentials occur along axons.

Synaptic End Bulbs

• Part of the axon with different voltage gates.
• Potential Types: Action potentials.

Quizzes and Key Discussion Points

• Emphasis on understanding where different potentials occur in neurons.
• Importance of reading questions thoroughly during exams.
• Understanding potentials and gates in neurons aids in test preparation.

Neuron Potential Events

1. Summation of Graded Potentials - Occurs at the soma and dendrites.
2. Depolarization - Occurs when sodium ions rush in.
3. Repolarization - Potassium ions exit the neuron.
4. Hyperpolarization - Occurs if potassium gates slow to close.
5. Return to Resting Potential - Achieved via the sodium-potassium pump.

Neuron Communication

Between Neurons

• Synapse: Junction where two neurons communicate without touching; involves synaptic cleft/gap.
• Presynaptic Neuron: Releases neurotransmitters like ACH and GABA.
• Postsynaptic Neuron: Receives neurotransmitters at ligand-gated channels.

Neuromuscular Junction (NMJ)

• Similar steps as neuron-to-neuron communication.
  • AP: Action potential travels to end bulb.
  • Calcium VGs: Open due to depolarization.
  • Exocytosis: Release of neurotransmitters.
  • Ligand-gated channel: Binding causes sodium influx and potential action potential initiation.

Inhibitory and Excitatory Potentials

• IPSP (Inhibitory Postsynaptic Potential) - Caused by negative ions like chloride entering the neuron.
• EPSP (Excitatory Postsynaptic Potential) - Caused by positive ions like sodium entering the neuron.

Spinal Cord Anatomy and Physiology

• Structure: Consists of gray matter (lacking myelin) and white matter (containing myelin).
• Roots:
  • Sensory (Posterior/Dorsal): Unipolar neurons bringing info into the spinal cord.
  • Motor (Anterior/Ventral): Motor neurons leaving the spinal cord.
  • Ganglia: Bundles of somas in sensory roots, forming swellings.
• Interneurons: Perform integration and reside in gray matter.
  • Always multipolar.

Spinal Cord Internal Anatomy

• Columns (White Matter): Composed of myelinated axons.
  • Posterior Columns: Mostly sensory.
  • Anterior Columns: Mostly motor.
  • Lateral Columns: Mixed sensory and motor.
• Horns (Gray Matter): Areas of integration.
  • Posterior Horns: Sensory integration.
  • Anterior Horns: Motor output.
  • Lateral Horns: Present in thoracic and lumbar regions.
• Central Canal: Circulates cerebrospinal fluid (CSF).

Communication Pathways

• Right/Left Communication:
  • Gray Commissure: Allows for gray matter communication.
  • White Commissure: Allows for white matter communication.

Feedback Cycle in Nervous System

• Input: Detected by sensory neurons, entering via dorsal roots.
• Control Center: Gray matter for analysis.
• Output: Carried by motor neurons to effectors.
  • Somatic: Targets skeletal muscle.
  • Autonomic: Targets cardiac, smooth muscle, and glands.

Miscellaneous

• Tetanus Effect: Blocks calcium voltage gates affecting neurotransmitter release.
• Exam Information: Test preparation focuses on chapters 10 and 12; practice with clicker questions.