Recording-2025-03-12 NEUROPHYSIOLOGY

Acetylcholine and Synaptic Transmission

• Acetylcholine (ACh) is located in the synaptic cleft.

  • It diffuses across the synaptic cleft to facilitate communication between neurons.

Neuronal Action & Potassium Efflux

• Potassium (K+) Efflux:

  • When potassium exits the neuron, it leads to hyperpolarization (the cell becomes more negative).

  • This efflux moves the membrane potential away from the threshold needed for firing an action potential.

Postsynaptic and Presynaptic Interaction

• Postsynaptic Cell: Receives signals from multiple presynaptic neurons.

  • Visual Aid: Diagram showing one postsynaptic neuron receiving inputs from several presynaptic neurons (five in this example).

Summation of Potential

• Summation: Process by which multiple signals combine to determine the postsynaptic neuron's action.

  • Types of Summation:

    • Spatial Summation:

      • Defined by contributions from multiple neurons.

      • If multiple presynaptic neurons contribute to the postsynaptic potential simultaneously, it leads to spatial summation.

    • Temporal Summation:

      • Involves one neuron firing multiple times in rapid succession.

      • Enhances the postsynaptic potential if the neuron fires repeatedly enough to summate.

Choroid Plexus & CSF Production

• Choroid Plexus: Located in three ventricles (lateral, third, and fourth), where blood plasma is converted into cerebrospinal fluid (CSF).

Nervous System Pathways

• Sensory Pathway:

  • Sensory information enters the spinal cord via the dorsal root.

  • Ascends to the brain for processing and response generation.

• Motor Pathway:

  • After processing, a message is sent down via the motor descending tract to execute actions.

  • The ventral root is involved in transmitting motor commands.

Reflexive Actions

• Withdrawal Reflex: A rapid, automatic response to stimuli (e.g., touching something hot).

• Autonomic Reflexes:

  • Pupillary Reflex involving the iris muscle, leading to pupil constriction in response to light.

Primary Somatosensory Cortex & Sensory Processing

• Information related to touch and proprioception is directed to the primary somatosensory cortex via specific pathways:

  • Dorsal Column Pathway:

    • Responsible for transmitting touch and proprioception information.

  • Three Neuron System: Illustrates the pathway from sensory receptors to the cortex.

Neuron Names & Origination Locations

• Understanding the details of specific second-order neurons is crucial. For example:

  • Determine where each neuron begins its path and its relevant functions.

  • This facilitates comprehending the complete sensory pathways.