Lecture on Glial Cells and Sensory Structures

Glial Cells

  • Definition: Non-neuronal cells in the nervous system that support and protect neurons.
  • Types:
    • CNS Glial Cells:
    • Astrocytes – regulate nutrients, blood-brain barrier, structural support
    • Microglia – immune cells, phagocytes
    • Ependymal cells – make CSF
    • Oligodendrocytes – form myelin in CNS
    • PNS Glial Cells:
    • Schwann cells – make myelin in PNS
    • Satellite cells – support neuron cell bodies in ganglia

Neural Fibers

  • Myelinated Nerves: Nerve fibers that are coated with myelin, enhancing the speed of electrical signals through saltatory conduction.
  • Unmyelinated Nerves: Nerve fibers that lack a myelin sheath, resulting in slower signal transmission.

Ganglia

  • Definition: Clusters of neuronal cell bodies located in the peripheral nervous system. They act as relay points for signals traveling to and from the CNS.

Divisions of the Nervous System

  • Understand Divisions: It is important to know the structural organization of the nervous system:
    • CNS = brain + spinal cord
    • PNS = nerves + ganglia
  • Control Centers: Critical components of the brain like the medulla oblongata which controls autonomic functions such as breathing, heart rate, and blood pressure.

Anatomy of the Spinal Cord

  • Three Layers of Meninges:
    • Dura Mater: The outermost tough protective layer.
    • Arachnoid Mater: The middle layer that provides a cushioning effect.
    • Pia Mater: The innermost layer that closely adheres to the surface of the spinal cord.
  • Fissures: Deep grooves that divide the spinal cord into left and right sections (e.g., anterior median fissure).
  • Gyri and Sulci: These are terms used in practical anatomy for the brain, not the spinal cord; gyri are ridges on the brain’s surface while sulci are the grooves separating them.

Dura Mater in the Spinal Nerve

  • Function: The dura mater surrounds and protects the spinal cord as part of the meninges.

Autonomic Nervous System (ANS)

  • Divisions:
    • Sympathetic Nervous System: Responsible for the 'fight or flight' response, preparing the body for stressful situations.
    • Parasympathetic Nervous System: Responsible for the 'rest and digest' state, promoting maintenance activities and conserving energy.

Special Senses

  • Distinguish between the senses that have dedicated organs:
    • Vision (eye)
    • Hearing (ear)
    • Equilibrium (inner ear)
    • Taste (tongue)
    • Smell (nose)

General Senses

  • Definition: Refers to sensations that are spread throughout the body and do not have dedicated sensory organs, including touch, pressure, temperature, pain, and proprioception.

Sensory Adaptation

  • Definition: The process by which sensitivity to a constant stimulus diminishes over time as receptors stop responding.

Receptor Types

  • Various sensory receptors that respond to specific stimuli in the environment include mechanoreceptors, chemoreceptors, thermoreceptors, nociceptors, and photoreceptors.

Taste Sensations

  • Five Basic Taste Sensations:
    1. Sweet
    2. Sour
    3. Salty
    4. Bitter
    5. Umami
  • Producers: Various compounds or food items that elicit these taste sensations.

Eye Structure and Functions

  • Photoreceptors: Different types of cells in the retina responsible for sensing light.
    • Rods: Responsible for vision in low light conditions.
    • Cones: Responsible for color vision and function well in bright light.
  • Basic Eye Conditions:
    • Cataracts: Clouding of the lens affecting vision.
    • Glaucoma: A condition which damages the optic nerve, often related to high intraocular pressure.

Ear Structures and Functions

  • Vestibular Apparatus: A complex structure in the inner ear that helps maintain balance and spatial orientation, including the semicircular canals and the vestibule (utricle & saccule).

Conclusion: The notes created provide an exhaustive outline covering neurological structures, senses, various nerve types, and common sensory conditions. These notes serve as a comprehensive guide for studying anatomy and physiology related to the nervous system and sensory organs.