BiologicalHierarchyFull

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Full Biological Hierarchy
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Divisions of Nervous System

Classical Divisions

Classical biological divisions are:

  • anatomically is divided into
    • central nervous system (CNS)
      • brain
      • spinal cord
    • peripheral nervous system (PNS) - convey neural messages from sense organs and sensory receptors to CNS and from CNS to muscles and glands
      • cranial nerves - nerves emerging from brain
      • spinal nerves - nerves emerging from spinal cord
  • functionally is divided into
    • somatic nervous system
      • conveying and processing conscious and unconscious sensory (afferent) information, vision, pain, touch, unconscious muscle sense from head, body wall, and extremities to CNS
      • motor (efferent) control of voluntary (striated) muscles
    • autonomic (visceral) nervous system
      • conveying and processing sensory input from visceral organs
      • motor control of involuntary (smooth) and cardiac musculature, and of glands of viscera

aHuman Divisions

For the purpose of modeling, to limit number of top-level items and simplify their names, to prevent from ambiguity related to different biological groupings, aHuman divisions are defined:

  • Sensors and effectors
    • HSA (head sensors area)
    • BEA (body effectors area)
  • Mind
    • PCA (posterior cortex area)
    • ACA (anterior cortex area)
    • THA (thalamus area)
    • HCA (hippocampus area)
    • BGA (basal ganglia area)
    • BSA (brain stem area)
    • SCA (spinal cord area)

Brain Development and Embryo Vesicles

In the embryon CNS/brain is represented by 5 vesicles:

  • telencephalon
  • diencephalon
  • mesencephalon
  • metencephalon
  • myelencephalon

After further development vesicles are transformed to below brain structures (linked to aHuman areas in capitals):

  • cerebrum
    • telencephalon -> cerebral hemispheres
      • cerebral cortex (gray matter)
        • ACA (anterior cortex area)
          • frontal lobe
        • PCA (posterior cortex area)
          • parietal lobe
          • occipital lobe
          • temporal lobe
          • central lobe (insula),
        • limbic lobe (split between PCA, ACA, HCA)
      • underlying white matter (split between PCA, ACA)
      • BGA (basal ganglia area)
        • corpus striatum (gray matter)
          • caudate nucleus
          • lenticular nucleus
            • putamen
            • globus pallidus (pallidum)
      • corpus callosum (required for left/right cooperation/coordination, not a source of intelligence)
      • anterior commissure (required for left/right cooperation/coordination, not a source of intelligence)
      • HCA (hippocampus area)
        • hippocampal formation
        • amygdala
    • THA (thalamus area)
      • diencephalon -> diencephalon
        • epithalamus
          • pineal gland (modified photoreceptor cells, day/night cycle, respond to circadian differences in sympathetic nervous system activity, critical trigger for hibernation and sexual maturation)
          • habenular nuclei (pathway by which limbic structures may influence brain stem/reticular formation function)
        • thalamus (dorsal thalamus)
        • hypothalamus
          • mamillary bodies
          • hypophysis (pituitary gland)
        • ventral thalamus (subthalamus)
  • BSA (brain stem area)
    • brainstem
      • mesencephalon -> midbrain
      • metencephalon -> pons
      • myelencephalon -> medulla
    • cerebellum
      • metencephalon -> cerebellum

Basal Ganglia

Several subcortical nuclei together with nucleus of diencephalon and couple in midbrain:

  • corpus striatum (putamen and caudate nucleus are called striatum)
  • subthalamic nucleus (within ventral thalamus)
  • substantia nigra (within midbrain)

Internal Capsule

Fibers projecting from subcortical nuclei to cerebral cortex and from cerebral cortex to subcortical structures in the cerebrum, brainstem, and spinal cord:

  • anterior limb
  • genu
  • posterior limb

Full Biological Components Overview

  • neocortex
    • frontal lobe
      • prefrontal cortex (personality, judgement, complex planning, inhibition, morality, executive memory, preparatory set, organize actions in time domain)
        • lateral prefrontal cortex - (executive function, evaluation of self-referential stimuli)
          • dorsolateral prefrontal cortex - (executive function, evaluation of self-referential stimuli)
          • ventrolateral prefrontal cortex - (executive function, evaluation of self-referential stimuli)
        • orbitomedial prefrontal cortex (emotional processing, prepresentaion of self-referential stimuli), another name is orbitofrontal cortex
          • ventromedial prefrontal cortex (humanity)
          • lie area - (ability to lie)
      • premotor cortex (patterned motor movements and planning)
      • primary motor cortex (moves individual muscles)
        • frontal eye fields (move muscles of the eye)
        • broka's area (muscles for speech)
    • parietal lobe
      • primary somatosensory cortex (anterior, basic sensations of the body)
      • superior parietal lobule (posterior)
        • somatosensory association (posterior, Brodmann #5, size, texture and relationship)
        • brodmann area 7 (posterior, involved in locating objects in space, convergence between vision and proprioception)
      • inferior parietal lobule (posterior)
        • brodmann area #39 (semantics)
        • werniche's area (brodmann area #40, involved in reading both in regards to meaning and phonology, sound and words)
      • intraparietal sulcus (posterior, essential in guidance of limb and eye movement)
        • lateral intraparietal (representing the saliency of spatial locations, and attention to these spatial locations, targeting eye movements)
        • ventral intraparietal (receives input from a number of senses - visual, somatosensory, auditory, and vestibular)
        • medial intraparietal (encode the location of a reach target in eye-centered coordinates)
        • anterior intraparietal (responsive to shape, size, and orientation of objects to be grasped)
      • gustatory (taste)
      • general interpretation area (opinions)
    • occipital lobe
      • primary visual cortex (simple lines and shapes)
      • visual associations (color, form and movement)
      • fusiform gyris (recognise faces)
    • temporal lobe
      • olfactory cortex (sense of smell)
      • insula (habits, visceral sensations)
      • primary auditory cortex (basic hearing - pitch, rhythm, loudness)
      • auditory association cortex (actual perception of sound)
      • parahippocampal gyrus (formation of spatial memory, encoding and recognition of scenes)
        • anterior parahippocampal gyrus
          • perirhinal cortex (visual perception and memory, facilitates recognition and identification of environmental stimuli)
          • entorhinal cortex (hub in a widespread network for memory and navigation, autobiographical/declarative/episodic memories, memory formation, memory consolidation, and memory optimization in sleep)
        • posterior parahippocampal gyrus (spatial declarative memory)
    • corpus callosum
      • splenium (integrate sensory and cognitive activity between the left and right hemispheres)
      • genu (integrate motor activity between the left and right hemispheres)
  • limbic system
    • cingulate cortex (regulating heart rate, blood pressure, cognitive and attentional processing)
      • anterior cingulate cortex (error and conflict detection processes)
      • posterior cingulate cortex (episodic memory, emotion, navigation , resting)
    • amygdala (signaling cortex of motivationally significant stimuli, left reacts top direction of gaze, right reacts to eye-to-eye contact)
    • hippocampus (detection of novel events, places and stimuli, spatial coding)
      • dentate gyrus (formation of memories, distinguishing multiple instances of similar events or multiple visits to the same location, stress and depression)
      • subiculum (spatial relations, working memory, drug addiction)
    • fornix (carries signals from the hippocampus)
    • septal nuclei (controller of theta rhythm, main source of cholinergic projections to the hippocampus)
    • basal ganglia (primitive motor system)
      • striatum (planning and modulation of movement pathways)
        • caudate nucleus (part of the learning and memory system)
        • putamen (regulate movements and influence various types of learning)
        • nucleus accumbens (reward, pleasure, laughter, addiction, aggression, fear, and the placebo effect)
          • nucleus accumbens core (acquisition and maintenance of a new strategy)
          • nucleus accumbens shell (mediate learning about irrelevant stimuli)
      • pallidum (reward and incentive motivation)
        • globus pallidus externa (main regulator of the basal ganglia system)
        • substantia nigra (reward, addiction, and movement)
      • subthalamic nucleus (action selection)
  • diencephalon (relay system between sensory input neurons and other parts of the brain)
    • thalamus (relaying sensation, spatial sense and motor signals to the cerebral cortex, regulation of consciousness, sleep and alertness)
      • specific relay nuclei (project to/from specific functional area of neocortex)
        • medial geniculate body (inferior colliculi -> auditory cortex)
        • lateral geniculate body (optic tract -> calcarine cortex of the occipital lobe)
        • ventral posterior nucleus
          • ventral posterior lateral nucleus (pain, temperature, touch, pressure, vibration, and conscious proprioception -> primary somesthetic area)
          • ventral posterior medial nucleus (face and head area via the 5th cranial nerve -> primary somesthetic area)
          • ventral medial nucleus (sense of taste -> primary taste area)
        • ventral lateral/anterior nucleus (motor control feedback from cerebellum and striatum -> primary motor cortex)
      • association nuclei (project to association areas)
        • anterior nucleus (mammillary bodies, hypothalamus, cingulate gyrus -> cingulate gyrus, hypothalamus, and hippocampus)
        • medial nucleus (somatic sensory input from hypothalamus, amygdala -> prefrontal cortex, hypothalamus, hippocampus, striatum)
        • lateral nucleus (hypothalamus, cingulate gyrus -> cingulate gyrus)
        • posterior group nuclei (pain from spinothalamic tract and 5th cranial nerve -> insula)
        • pulvinar nuclei (reciprocal connections with association areas)
      • non-specific nuclei
        • intralaminar nuclei (basal ganglia, reticular formation -> all parts of neocortex, motor control system, perceptions of various modalities)
        • reticular nuclei (from all fibers leaving and entering the thalamus -> all thalamic nuclei, cortical regulation of the thalamic activity)
    • hypothalamus (hormone production and release, affects and regulates blood pressure, heart rate, hunger, thirst, sexual arousal, and the sleep/wake cycle)
      • mammillary body (relay from the amygdala and hippocampus to thalamus, add smell to memory)
      • pituitary gland (hormone factory for growth, milk production and adrenalin)
  • brain stem (main motor and sensory innervation to the face and neck)
    • medulla oblongata (autonomic, involuntary functions, such as breathing, heart rate and blood pressure, relays nerve signals between the brain and spinal cord)
    • midbrain
      • tectum
        • superior colliculus (preliminary visual processing and control of eye movements)
        • inferior colliculus (auditory processing, receives input from various brain stem nuclei and relays auditory information to the primary auditory cortex)
      • cerebral peduncle
        • midbrain tegmentum (involved in many unconscious homeostatic and reflexive pathways)
        • crus cerebri (contains motor tracts)
        • pretectum (receives binocular sensory input from eyes)
        • substantia nigra (eye movement, motor planning, reward seeking, learning, and addiction)
    • locus coeruleus (mediating many of the sympathetic effects during stress - clinical depression, panic disorder, and anxiety) - alter cognitive function (through the prefrontal cortex), increase motivation (through nucleus accumbens), activate the hypothalamic-pituitary-adrenal axis, and increase the sympathetic discharge/inhibit parasympathetic tone (through the brainstem)
    • raphe nuclei (inhibit pain sensation)
    • pons (relay signals from the forebrain to the cerebellum, along with nuclei that deal primarily with sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation, and posture)
      • cranial nerves
        • 0 - cranial nerve zero (detection of pheromones)
        • 1 - olfactory nerve (transmits the sense of smell)
        • 2 - optic nerve (transmits visual information to the brain)
        • 3 - oculomotor nerve (perform most eye movements)
        • 4 - trochlear nerve (depresses, rotates laterally - around the optic axis, and intorts the eyeball)
        • 5 - trigeminal nerve (receives sensation from the face and innervates the muscles of mastication)
        • 6 - abducens nerve (abducts the eye)
        • 7 - facial nerve (motor innervation to the muscles of facial expression, receives the special sense of taste from anterior tongue, secretomotor innervation to the salivary glands and lacrimal gland)
        • 8 - vestibulocochlear nerve (senses sound, rotation and gravity, carries impulses for equilibrium)
        • 9 - glossopharyngeal nerve (receives taste from the posterior tongue)
        • 10 - vagus nerve (branchiomotor innervation to most laryngeal and all pharyngeal muscles, receives the special sense of taste from the epiglottis, controls muscles for voice and resonance and the soft palate)
        • 11 - accessory nerve (controls sternocleidomastoid and trapezius muscles, overlaps with functions of the vagus)
        • 12 - hypoglossal nerve (motor innervation to the muscles of the tongue, swallowing and speech articulation)
  • cerebellum (complex motion behavior, sequential thinking, attention and language, coordination, precision, and accurate timing)
    • peduncles
      • inferior cerebellar peduncle (to/from medulla/spinal cord)
      • middle cerebellar peduncle (from pons)
      • superior cerebellar peduncle (to midbrain)
      • arbor vitae (brings sensory/motor information to/from cerebellum)
    • vestibulocerebellum (involved in eye movements and maintain balance)
      • archicerebellum
      • flocculonodular lobe
        • flocculus
        • nodule
    • spinocerebellum (control of muscle tone and coordination of muscle movement on the same side of the body, sensomotory -> cerebellum -> musles, sensomotory -> cerebellum -> thalamus -> musles, sensomotory -> cerebellum -> motor cortex -> muscles)
      • paleocerebellum
      • vermis and intermediate zone
    • cerebrocerebellum (participates in planning movements, sensory/prefrontal -> cerebellum -> thalamus -> motor cortex -> muscles
      • neocerebellum
      • lateral zone
    • fourth ventricle (protects brain from trauma)
    • choroid plexus (inhibits neuronal maturation)
  • spinal cord
    • dorsal column-medial lemniscus tract (touch/proprioception/vibration sensory pathway)
    • anterolateral system (pain/temperature sensory pathway)
    • corticospinal tract (motor pathway for upper motor neuronal signals coming from the cerebral cortex and from primitive brainstem motor nuclei)
      • lateral corticospinal tract (distal limb control)
      • anterior cortical spinal tract (control the large, postural muscles of the axial skeleton)
    • ventral spinocerebellar tract (roprioceptive information travels up the spinal cord)
    • dorsal spinocerebellar tract (ascend into the cerebellum)
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