Neuroanatomy by Matthias Heyner 2008 Neuroanatomy



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Neuroanatomy © by Matthias Heyner 2008





Neuroanatomy

The four Parts of the diencephalon



Part

Boundary line

Structure

Function

Epithalamus




  • Pineal gland

  • Habenulae

Regulation of circadian rhythms, linking of olfactory system to brainstem




Dorsal diencephalic sulcus







Thalamus




  • Thalamus

Relay of sensory information; assistance in regulation of motor function




Middle diencephalic sulcus







Subthalamus




  • Subthalamic nucleus

  • Zona incerta

  • Globus Pallidus

Relay of sensory information (somatomotor zone of diencephalon




Ventral diencephalic sulcus (=hypothalamic sulcus







Hypothalamus




  • Optic chiasm, optic tract

  • Tuber cinereum, neurohypophysis

  • Mammillary bodies

Coordination of autonomic nervous system with endocrine system; participation in visual pathway

Nomenclature of the thalamic nuclei

Name

Alternative Name

Properties

Specific thalamic nuclei (cortically dependent)

Palliothalamus

Project to the cerebral cortex (pallium)

Nonspecific thalamic nuclei (cortically independent)

Truncothalamus

Project to brainstem, diencephalon and corpus striatum

Integration nuclei




Project to other nuclei within the thalamus (classified as nonspecific thalamic nuclei)

Intralaminar nuclei




Nuclei in the white matter of the internal medullary lamina (classified as nonspecific thalamic nuclei)

Synopsis of some clinically important connections of specific thalamic nuclei

Thalamic afferents (structures that project to the thalamus)

Thalamic nucleus (abbreviation)

Thalamic efferents (structure to which the thalamus projects)

Mammillary Body (mammillothalamic fasciculus)

Anterior nucleus (NA)

Cingulate gyrus (limbic system)

Cerebellum, red nucleus

Ventral lateral nucleus (VL)

Premotor cortex (areas 6aα and 6aβ)


Posterior funiculus, lateral funiculus (somatosensory input, limbs, trunk)

Ventral posterolateral nucleus (VPL)

Postcentral gyrus (sensory cortex) = somatosensory cortex

Trigeminothalamic tract (somatosensory input, head)

Ventral posteromedial nucleus (VPM)

Postcentral gyrus (sensory cortex) = somatosensory cortex

Inferior brachium (part of the auditory pathway)

Medial geniculate nucleus (body) (MGB)

Transverse temporal gyri (auditory cortex)

Optic tract (part of the visual pathway

Lateral geniculate nucleus (body) (LGB)

Striate area (visual cortex)

Functions of the hypothalamus

Region or Nucleus

Function

Anterior preoptic region

Maintain constant body temperature; Lesion: central hypothermia

Posterior region

Respond to temperature changes, e.g., sweating; Lesion: hypothermia

Midanterior and posterior regions

Activate sympathetic nervous system

Paraventricular and anterior regions

Activate parasympathetic nervous system

Supraoptic and paraventricular nuclei

Regulate water balance; Lesion: Diabetes insipidus, also lack of thirst response resulting in hyponatremia

Anterior nuclei:

Regulate the appetite and food intake:

  • Medial part

  • Lesion: Obesity

  • Lateral part

  • Lesion: Anorexia and emaciation

Hormones of the anterior pituitary lobe (adrenohypophysis)

Hormones and synonyms

Cell designation*

Hormone actions

Somatotropin (STH)

Growth hormone (GH)

Somatotropic hormone


Somatotropic (a)

Stimulates longitudinal growth; acts on carbohydrate and lipid mechanism

Prolactin (PRL o LTH)

Mammotropic (a)

Stimulates lactation and proliferation of glandular breast tissue

Follitropin (FSH)
Follicle-stimulating hormone

Gonadotropic (b)

Acts on the gonads; stimulates follicular maturation, spermatogenesis, estrogen production, expression of lutropin receptors and proliferation of granulose cells.

Lutropin (LH)
Interstitial cell stimulating hormone – ICSH
luteinizing hormone

Gonadotropic (b)

Triggers ovulation; stimulates proliferation of follicular epithelial cells, production of testosterone in interstitial Leydig cells of the testis, and synthesis of progesterone, has general anabolic activity

Thyrotropin (TSH)
Thyroid stimulating hormone
Thyrotropic hormone

Thyrotropic (b)

Stimulates thyroid gland activity; increases O2 consumption and protein synthesis; influences carbohydrate and lipid metabolism

Corticotropin (ACTH)

Adrenocorticotropic hormone



Adrenotropic (b)

Stimulates hormone production in adrenal cortex; influences water and electrolyte balance; acts on carbohydrate formation in liver

Alpha/beta Melanotropin (MSH)

Melanotropic (b)

Aids in melanin formation and skin pigmentation; protects against UV radiation**

*Cells are classified as either acidophilic (a) or basophilic (b)

**In human, melanotropin serves as a neurotransmitter in various brain regions.



Overview of the nuclei of cranial nerves III-XII

Motor nuclei: give rise to efferent (motor) fibers

Sensory nuclei: where afferent (sensory) fibers terminate

Somatic efferent or somatic motor nuclei:

  • Nucleus of oculomotor nerve (CN III)

  • Nucleus of trochlear nerve (CN IV)

  • Nucleus of abducent nerve (CN VI)

  • Nucleus of accessory nerve (CN XI)

  • Nucleus of hypoglossal nerve (CN XII)

Somatic afferent (somatic sensory) and vesibulocochlear nuclei:

Sensory nuclei associated with the trigeminal nerve (CN V):



  • Mesencephalic nucleus of trigeminal nerve (special feature: pseudounipolar ganglion cells (“displaced sensory ganglion”), provide direct sensory innervation for muscles of mastication)

  • Principal (pontine) sensory nucleus of trigeminal nerve

  • Spinal nucleus of trigeminal nerve

Visceral efferent (visceral motor) nuclei:

Nuclei associated with the parasympathetic nervous system:



  • Visceral oculomotor (Edinger – Westphal) nucleus (CN III)

  • Superior salivatory nucleus (facial nerve, CN VII)

  • Inferior salivatory nucleus (glossopharyngeal nerve, CN IX)

  • Dorsal vagal nucleus (CN X)

Nuclei of the vestibulocochlear nerve (CN VIII):

  • Vestibular part:

    • Medial vestibular nucleus

    • Superior vestibular nucleus

    • Lateral vestibular nucleus

    • Inferior vestibular nucleus

  • Cochlear part:

    • Anterior cochlear nucleus

    • Posterior cochlear nucleus

Visceral afferent (visceral sensory) nuclei:

  • Nucleus of the solitary tract (nuclear complex):

    • Superior part:

      • Special visceral afferents (taste) from facial (CN VII), glossopharyngeal (CN XI), and vagus (CN X) nerves

    • Inferior part:

      • General visceral afferents from glossopharyngeal (CN IX) and vagus (CN X) nerves

Nuclei f the branchial arch nerves:

  • Trigeminal motor nucleus (CN V)

  • Facial nucleus (CN VIII)

  • Nucleus ambiguous (glossopharyngeal nerve, CN IX; vagus nerve, CN X; accessory nerve, CN XI, cranial root)

Synopsis of cerebellar classifications

Phylogenetic classification

Anatomical classification

Functional classification based on the origin of afferents

  • Archicerebellum

  • Flocculonodular lobe

  • Vestibulocerebellum: maintenance of equilibrium

  • Paleocerebellum

  • Anterior lobe of cerebellum

  • Portions of the vermis

  • Median portions of the posterior lobe

  • Spinocerebellum: Regulation of muscle tone

  • Neocerebellum

  • Lateral portions of the posterior lobe

  • Pontocerebellum (= cerebrocerebellum): skilled movements

Cerebellar Nuclei and the regions of the cortex from which they receive projections

Cerebellar Nucleus

Synonyms

Region of the cerebellar cortex that send axons to the nucleus

Dentate nucleus

Lateral cerebellar nucleus

Lateral part (lateral portions of the cerebellar hemispheres)

Emboliform nucleus

Anterior interpositus nucleus

Intermediate part (medial portions of the cerebellar hemispheres)

Globose nuclei

Posterior interpositus nucleus

Intermediate part (medial portions of the cerebellar hemispheres)

Fastigial nucleus

Medial cerebellar nucleus

Median part (cerebellar vermis)

Principal neurons and fiber types in the cerebellar cortex

Name

Definition

Climbing fibers

Axons of neurons of the inferior olive and its associated nuclei

Mossy fibers

Axons of neurons of the pontine nuclei, the spinal cord, and the vestibular nuclei (pontocerebellar, spinocerebellar, and vestibular tracts)

Parallel fibers

Axons of the granule cells

Granule cells

Interneurons of the cerebellar cortex

Purkinje cells

The only efferent cells of the cerebellar cortex; exert an inhibitory effect

Synopsis of the cerebellar peduncles and their tracts

Cerebellar peduncle and constituent parts*

Origin**

Site of Termination

Superior cerebellar peduncle: contains mostly efferent tracts from the cerebellar nuclei. Some tracts cross in the decussation of the superior peduncle, then divide into a descending limb (to the pons) and an ascending limb (to the midbrain and the thalamus).

Descending parts (e)

Fastigial and globose nuclei

Reticular formation and vestibular nuclei (projection is mostly contralateral)

Ascending parts (e)

Dentate nucleus

Red nucleus and thalamus (both contralateral)

Anterior Spinocerebellar tract (a)

Secondary neurons in intermediate gray matter, lumbosacral spinal cord. Relays proprioception (muscle spindles, tendon receptors, etc) from dorsal root (spinal) ganglion cells, lower limb and trunk. Fibers cross locally and then re-cross in the pons to return to the ipsilateral side.

Vermis and intermediate part of anterior lobe of cerebellum (ipsilateral; terminates as mossy fibers)

Middle cerebellar peduncle: contains only afferent tracts.

Pontocerebellar fibers (a)

Basal pontine nuclei. Relay cerebropontine to pontocerebellar projection (source of 90% of axons in middle peduncle)

Lateral regions of posterior and anterior lobes of cerebellum (contralateral; terminate as mossy fibers; branches to contralateral dentate nucleus)

Inferior cerebellar peduncle: contains both afferent and efferent tracts.

Posterior Spinocerebellar tract (a)

Posterior thoracic nucleus and thoracic spinal cord. Relays proprioception and cutaneous sensation from the lower limb. Contains large axons with high conduction velocity.

Vermis and nearby anterior lobe of cerebellum, pyramid and nearby posterior lobe of cerebellum. (ipsilateral; terminates as mossy fibers)

Cuneocerebellar tract (a)

Nucleus cuneatus and external cuneate nucleus. Relays proprioception (external cuneate nucleus) and cutaneous sensation (nucleus cuneatus) from the upper limb, with fast transmission, functionally corresponding to the posterior Spinocerebellar tract.

Posterior part of anterior lobe of cerebellum (ipsilateral; terminates as mossy fibers)

Olivocerebellar tract (a)

Inferior olivary nuclear complex. Inferior olive receives numerous inputs from sensory and motor systems, including a large contralateral projection from the cerebellum itself (dentate nucleus, see below)

Molecular layer of cerebellar cortex (contralateral, terminates as climbing fibers)

Vestibulocerebellar tract (a)

Semicircular canal (vestibular ganglion) and vestibular nuclei. Transmits balance and body position/motion information either directly (vestibular axons via vestibulocochlear nerve [CN VIII], ipsilateral) or via synaptic relay in vestibular nuclei (bilateral).

Nodule, flocculus, anterior lobe, and vermis of cerebellum (bilateral, see left; terminates as mossy fibers)

Trigeminocerebellar fibers (a)

Trigeminal sensory nuclei in the brainstem. Relay proprioception and cutaneous sensation from the head

Rostral part of posterior lobe of cerebellum (ipsilateral; terminate as mossy fibers)

Cerebello-olivary fibers (e)

Dentate nucleus

Inferior olive (contralateral)

*Subentries for constituent parts are classified as efferent (e) or afferent (a).
**In the case of afferents, the type of afferent is listed along with the site of origin

Synopsis of cerebellar classifications and their relationships to motor deficits

Functional classification

Phylogenetic classification

Anatomical classification

Deficit symptoms

Vestibulocerebellum

Archicerebellum

Flocculonodular lobe

  • Truncal, stance and gait ataxia

  • Vertigo

  • Nystagmus

  • Vomiting

Spinocerebellum

Paleocerebellum

Anterior lobe, parts of vermis; Posterior lobe, medial parts

  • Ataxia, chiefly affecting the lower limb

  • Oculomotor dysfunction

  • Speech disorder (asynergy of speech muscles)

Pontocerebellum (=cerebrocerebellum)

Neocerebellum

Posterior lobe, hemispheres

  • Dysmetria and hypermetria (positive rebound)

  • Intention tremor

  • Nystagmus

  • Decreased muscle tone

Synopsis of sensory Pathways

Name of Pathway

Sensory quality

Receptor

Course in the Spinal cord

Central course (above the Spinal cord)

Spinothalamic tracts

Anterior Spinothalamic tract

  • Crude touch

The perikaryon of the second neuron is located in the posterior horn and may be up to 15 segments above or 2 segments below the entry of the first neuron. Its axons crossing the anterior commissure.

The axons of the second neuron (spinal lemniscus) terminate in the ventral posterolateral nucleus of the thalamus. There they synapse onto the third neuron, whose axons project to the postcentral gyrus.

Lateral Spinothalamic tract

  • Pain and temperature

  • Mostly free nerve endings

The perikaryon of the second neuron is in the substantia gelatinosa. Its axon crosses at the same level in the anterior commissure.

The axons of the second neuron (spinal lemniscus) terminate in the ventral posterolateral nucleus of the thalamus. There they synapse onto the third neuron, whose axons project to the postcentral gyrus

Tracts of the posterior funiculus

Fasciculus gracilis

  • Fine touch

  • Conscious proprioception of lower limb

  • Vater-Pacini corpuscles

  • Muscle and tendon receptors

The axons of the first neuron pass to the nucleus gracilis in the lower medulla oblongata (second neuron)

The axons of the second neuron cross in the brainstem and traverse the medial lemniscus to the ventral posterolateral nucleus of the thalamus. There they synapse onto the third neuron whose axons project to the postcentral gyrus

Fasciculus cuneatus

  • Fine touch

  • Conscious proprioception of the upper limb

  • Vater-Pacini corpuscles

  • Muscle and tendon receptors

The axons of the first neuron pass to the nucleus cuneatus in the lower medulla oblongata (second neuron)

The axons of the second neuron cross in the brainstem and traverse the medial lemniscus to the ventral posterolateral nucleus of the thalamus. There they synapse onto the third neuron whose axons project to the postcentral gyrus

Spinocerebellar tracts

Anterior Spinocerebellar tract (of Gowers)

  • Unconscious crossed and uncrossed extero- and proprioception to the cerebellum

  • Muscle spindles

  • Tendon receptors

  • Joint receptors

  • Skin receptors

The second neuron is located in the dorsal column in the central part of the gray matter. The axons of the second neuron run directly to the cerebellum, both crossed and uncrossed without synapsing with a third neuron.

The axons of the second neuron pass through the superior cerebellar peduncle to the vermian part of the spinocerebellum (no third neuron

Posterior Spinocerebellar tract (of Flechsig)

  • Unconscious uncrossed extero- and proprioception to the cerebellum

  • Muscle spindles

  • Tendon receptors

  • Joint receptors

  • Skin receptors

The second neuron is located in the thoracic nucleus (Clarke column, Stilling nucleus) in the gray matter at the base of the posterior horn. The axons of the second neuron run directly to the cerebellum without crossing.

The axons of the second neuron pass through the inferior cerebellar peduncle to the vermian part of the spinocerebellum (no third nucleus)



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