Nervous System - Quick Reference

Central Nervous System (CNS)

  • Definition: CNS consists of the brain and spinal cord; processes and integrates information.
  • CNS components: brain, spinal cord.

Peripheral Nervous System (PNS)

  • Definition: Spinal and cranial nerves; conveys messages to and from the CNS.

Autonomic Nervous System (ANS)

  • Regulates involuntary physiological processes (HR, BP, respiration, digestion).
  • Divisions: $\text{sympathetic}$, $\text{parasympathetic}$, $\text{enteric}$ ($3$ divisions).

Cellular Components of the Nervous System

  • Neurons: information processing & signaling; sensory & motor neurons reside in PNS & CNS; most neurons in CNS.
  • Glial cells:
    • Microglia: phagocytes.
    • Macroglia: oligodendrocytes (CNS) & Schwann cells (PNS).
    • Astrocytes.

SENSORY NEURONS

  • Proprioception: specialized sense from muscles, tendons, joints; vestibular sense is special.
  • Four classes of sensory neurons:
    • General somatic afferent: touch, pressure, pain, temperature.
    • General visceral afferent: stretch, pressure.
    • Special somatic afferent: vision, hearing.
    • Special visceral afferent: taste, smell.

MOTOR NEURONS

  • Upper motor neurons (UMN):
    • Cell bodies in cortex or brainstem nuclei; axons project to spinal cord and/or cranial nerve nuclei.
    • Initiate or modulate voluntary movement by innervating LMN and interneurons.
  • Lower motor neurons (LMN):
    • Cell bodies in anterior horn of spinal cord or cranial nerve nuclei; axons to muscles to produce contractions.
    • ACTION IS ALWAYS EXCITATORY.
  • Motor unit: the motor neuron and all muscle fibers it innervates.

GLIAL CELLS: OLIGODENDROCYTES & SCHWANN CELLS

  • Oligodendrocytes: produce myelin sheath for CNS axons; envelope several axons.
  • Schwann cells: produce myelin sheath for PNS axons; can envelope one or several axons.
  • Additional roles: structural support, phagocytosis, secretion of neurotrophins.

GLIAL CELLS: ASTROCYTES

  • Types: radial glia (developmental guidance), protoplasmic (gray matter) & fibrous (white matter).
  • Major roles: mechanical/metabolic support; response to CNS injury; gliotic scar formation.

GRAY MATTER & WHITE MATTER

  • Gray matter: cell bodies & dendrites; contains nuclei; cortex is a layered gray matter surface.
  • White matter: myelinated axons; tracts (fasciculus, funiculus, lemniscus, peduncle).

GROSS ANATOMY OF THE BRAIN

  • Divisions: Forebrain, Cerebellum, Brainstem.
  • Cerebral hemispheres; brainstem components (midbrain, pons, medulla); cerebellum; diencephalon.
  • Ventricular system present with connections to subcortical structures.

DIVISIONS OF THE BRAIN

  • Forebrain, Cerebellum, Brainstem.
  • Subdivisions include: cerebral hemispheres, diencephalon (thalamus & hypothalamus).
  • Brainstem includes: midbrain, pons, medulla.

TERMINOLOGY & PLANES

  • Planes: sagittal, parasagittal, coronal/frontal, transverse/axial/horizontal.
  • Orientation: anterior (rostral), posterior (caudal), superior, inferior.
  • Also used: rostral vs caudal terminology in brain anatomy.

FOREBRAIN

  • Diencephalon: thalamus, hypothalamus.
  • Two cerebral hemispheres connected by the corpus callosum.
  • Ventricular system structures: ventricles and related pathways.

CEREBRAL CORTEX

  • Highly folded (convoluted) surface to increase cortical area and neuron numbers.
  • Gyrus = ridge; Sulcus = groove; Fissure = deep groove.
  • Cortex organization varies between individuals.

LOBES & SULCI (major sulci)

  • Major lobes: Frontal, Parietal, Temporal, Occipital, Limbic.
  • Major sulci: central sulcus, lateral (Sylvian) fissure, parietooccipital sulcus, cingulate sulcus, calcarine sulcus, intraparietal sulcus, occipitotemporal sulcus, collateral sulcus.

GYRI: FRONTAL LOBE

  • Frontal gyri: superior, middle, inferior; precentral gyrus (location of primary motor cortex).
  • Precentral sulcus; postcentral gyrus is in the parietal lobe.
  • Orbital and other frontal gyri (orbital part; triangular/opercular parts).

FRONTAL LOBE FUNCTIONAL AREAS

  • Primary motor cortex: most of the precentral gyrus; initiation of voluntary movement.
  • Premotor & supplementary motor areas: posterior portions of superior, middle, inferior frontal gyri; planning/initiation of movement.
  • Broca's area (left hemisphere): motor aspect of language (speech production);
  • Prefrontal cortex: executive function (planning, decision-making, social behavior).

PARIETAL LOBE FUNCTION

  • Primary somatosensory cortex: postcentral gyrus; initial cortical processing of tactile and proprioceptive information.
  • Language comprehension (integration with language areas).
  • Spatial orientation and directing attention.

TEMPORAL & OCCIPITAL LOBES

  • Temporal lobe: primary auditory cortex.
  • Occipital lobe: primary visual cortex.

LIMBIC LOBE

  • Cortical component of limbic system; interconnected with hypothalamus, thalamus, amygdala, hippocampus.
  • Functions: emotion, drive-related behaviors, memory.

BRODMANN'S AREAS

  • Korbinian Brodmann identified $52$ cortical regions based on cytoarchitecture.
  • Used to map structure-function relationships across the cortex.

KEY STRUCTURES: Diencephalon, Limbic System, Basal Nuclei

  • Diencephalon components include thalamus and hypothalamus.
  • Limbic system: hypothalamus, thalamus, amygdala, hippocampus; functions in emotion, memory, drives.
  • Basal nuclei (basal ganglia): motor control circuits (not detailed in slides, noted as related).

REFERENCES / COMPREHENSIVE VIEW

  • Core concepts summarized from Nolte and Mosconi & Graham.