Topic 1a

Neuroanatomy and Neurophysiology of Sensory Pathways

  • Touch

    • Mechanoreceptors in the skin detect pressure, vibration, texture.

    • Sensory signals travel via peripheral nerves ➔ spinal cord ➔ dorsal column-medial lemniscal pathway ➔ processed in primary somatosensory cortex (parietal lobe).

  • Kinesthesia

    • Sense of body position/movement; mediated by proprioceptors in muscles, tendons, joints.

    • Signals travel through the spinocerebellar tract to the cerebellum for coordination and balance.

Neuroanatomy and Neurophysiology of Vision

  • Visual Pathway

    • Light ➔ retina ➔ photoreceptors (rods and cones) convert light to electrical signals.

    • Transmitted via the optic nerve ➔ lateral geniculate nucleus (LGN, thalamus) ➔ primary visual cortex (V1, occipital lobe) for processing.

    • Higher-order processing occurs in the visual association areas.

Neuroanatomy and Neurophysiology of Balance

  • Vestibular System

    • Located in inner ear; detects head position/motion via semicircular canals & otolith organs.

    • Signals sent to vestibular nuclei in the brainstem; integrated with visual/proprioceptive inputs.

    • Cerebellum coordinates feedback for stability and posture maintenance.

Nervous System Cells and Communication

  • Morphology

    • Neurons: Main signaling cells.

    • Parts:

      • Cell Body (Soma): Maintains cell health.

      • Dendrites: Receive signals.

      • Axon: Transmits impulses.

    • Glial Cells: Support neurons; include astrocytes, oligodendrocytes (CNS myelin), Schwann cells (PNS myelin), microglia.

  • Synaptic Structure

    • Presynaptic Terminal ➔ Synaptic Cleft ➔ Postsynaptic Membrane

  • Communication Process:

    1. Action Potential Generation

    2. Neurotransmitter Release

    3. Receptor Binding

    4. Signal Termination (reuptake, degradation, diffusion).

Degrees of Freedom in Movement

  • Overview of Motor Control Theory

    • Explains how the nervous system coordinates movement.

    • Focuses on degrees of freedom (df) and coordination.

  • Degrees of Freedom Problem

    • Managing multiple independent elements; crucial for executing complex actions (e.g., helicopter flight).

Sensorimotor Integration

  • Definition

    • Combination of sensory information and motor commands for coordinated movements.

  • Key Components:

    • Perception (detection)

    • Action (movement regulation).

  • Importance

    • Joint Stability: Coordinates muscle activity to prevent injuries.

    • Postural Control: Adjusts based on sensory input.

Neural Hierarchy in Movement

  • Voluntary Movement Control

    • Hierarchical organization from higher to lower CNS levels.

    • Levels:

    • Highest: Higher centers

    • Middle: Sensorimotor cortex, Basal nuclei, Thalamus

    • Local: Brainstem, Cerebellum, Spinal cord.

Motor Control and Brain Structures

  • Cortical Structures

    • Involved in voluntary movements, planning, executing motor commands.

  • Subcortical Structures

    • Basal ganglia: Movement organization, initiation.

    • Cerebellum: Balance, coordination, timing.

Motor Behaviour Complexity

  • Overview

    • Recognizes challenges in coordinating systems for effective movement.

    • Involves neural pathways, sensory feedback, and motor planning.

  • Application

    • Relevant to sports performance, rehabilitation, driverless vehicles.