Nervous System: Neurons, Receptors and Brain Development

• The structure of a neuron includes dendrites, a cell body, specific cellular organelles, and an axon.

Topographical Receptor Classification

• Receptors are classified into exteroreceptors, interoceptors and mechanoreceptors

Receptor functions

• Collection of information from the external environment
• Collection of information from the internal environment
• Generating nerve impulses
• Selection of collected information
• Conduction of response reactions

Functional Classification of Neurons

• Sensory or afferent
• Motor or efferent
• Interneurons
• Secretory
• Neuroimmune

Neuron Features

• Neurons may be star-shaped or pyramidal.
• Neurons are a morphofunctional unit of the nervous system.
• Neurons may have multiple processes.
• Neurons generate and conduct nerve impulses.
• Neurons are not only located inside the neurax

Brain Development

• The brain develops from five vesicles.
• Myelencephalon becomes the diencephalon.
• Metencephalon becomes the cerebellum and pons.
• Mesencephalon becomes the midbrain.
• Diencephalon turns into endbrain
• Telencephalon becomes the medulla oblongata

Rhombencephalon Includes

• The rhombencephalon includes the metencephalon and myelencephalon.

Metencephalon

• The metencephalon consists of the cerebellum and pons

Brain Stem

• The brain stem includes the quadrigeminal colliculi, Pons of Varoli, myelencephalon (medulla oblongata) and mesencephalon

• The boundary between the brain and spinal medulla is located at the inferior margin of the greater occipital foramen.

• Structures located in the lateral grooves of the spinal cord are the dorsal roots.

• The anterior roots of the spinal nerves leave the spinal cord through the anterolateral groove.

• Lateral horns of the spinal cord grey matter are better pronounced in the thoracic and lumbar regions.

Spinal Cord Motor Neurons

• Bodies of the somatic motor neurons of the spinal cord are located in the anterior horns.

Spinal Cord Sensory Neurons

• Bodies of the somatic sensory neurons of the spinal cord are located in the posterior horns.
• The 31 pairs of spinal nerves are classified into 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal.
• Spinal ganglia are located on the posterior root of the spinal nerve.
• Branches of the spinal nerves are distributed metamerically in the thorax.

Dorsal Horn Neurons

• Dorsal horn neurons have a laminar arrangement from the apex to the base of the Rexed lamellae.

Dural Sac

• The bottom of the dural sac ends at the level of the S2 vertebra

• The spinal nerve is formed by the anterior and posterior roots.

• White matter of the spinal cord is organized under the aspect of cords of nerve fibers.

• Grey matter of the spinal cord consists of bodies of the neurons.

• Grey matter of the anterior horns of the spinal cord forms motor nuclei.

• Denticulate ligament is an extension of the pia mater.

Adult Spinal Cord

• In adults, the spinal cord usually ends at the level of the lower margin of the body of the first lumbar vertebra.
• Has anterior median fissure and posterior median septum

Spinal Nerves

• Spinal nerves are formed by the fusion of ventral and dorsal roots.
• Named and numbered according to the vertebrae from which they emerge
• Spinal nerves receive a grey communicating branch from the paravertebral sympathetic chain.

Cauda Equina Roots

• Cauda equina consists of roots of the lumbar, sacral and filum terminale nerves.
• Spinal medulla presents cervical and lumbosacral intumescences.

Cauda Equina Components

• The cauda equina consists of the roots of the lower lumbar and sacral nerves.

Spinal Cord Components

• Cervical intumescence

• Terminal filum

• Medullary conus

• On the external surface of the spinal cord, the anterior, posterior and lateral columns are distinguished.

• Specific ascending pathways of the spinal cord consist of three neurons.

• The anterior funiculus of the spinal cord contains the anterior (ventral) spinothalamic tract.

• The gray matter of the spinal cord contains somatomotor, vegetative, and somatosensory neurons, as well as reticular nerve cells.

• Reticular formation of the spinal cord is located in white matter, between the posterior and anterior horns.

• Spinal nerves have roots located in the lateral grooves of the spinal cord.

• Spinal nerves contain somatomotor and sensory fibers.

• On the cross-section of the spinal cord grey matter, posterior and ventral horns are present.

Posterior Horn

• Contains marginal zone, substantia gelatinosa & thoracic nucleus

• Lateral horns of the spinal grey matter contain vegetative sympathetic nuclei.

• The lateral white column of the spinal cord consists of the ventral spinocerebellar tract, the rubrospinal tract, and the lateral spinothalamic tract.

Posterior White Column

• The posterior white column of the spinal cord consists of the dorsalspinocerebellar tract, the fascicle of Goll (gracilis), and the fascicle of Burdach (cuneatus).

• The thoracolumbar part of the spinal cord consists of segments T1-T12.

• The lateral column of the spinal cord contains the dorsal and ventral spinocerebellar tracts, as well as the rubrospinal cord

Spinal Meninges

• The spinal meninges consist of the pachymeninx, arachnoid mater, and pia mater.
• Leptomeninges includes the arachnoid mater and pia mater.
• Cerebrospinal fluid is contained in the subarachnoid and lumbar cistern
• The spinal cord is covered with the dura mater (pachymeninx), pia mater and the arachnoid mater.
• Intermeningeal spaces of the spinal cord are the epidural, subdural and arachnoid.
• The nuclei of the myelencephalon include the ambiguus, dorsal nucleus of X cranial nerve, gracilis and inferior salivatory nucleus
• The motor nucleus of the IX nerve is located in the medulla oblongata.
• One of the sensory nuclei of the V nerve is located inside the medulla oblongata.
• Pons is a part of the metencephalon.
• The limits of the medulla oblongata are the inferior margin of the pons and the greater occipital foramen

This lesson contains information about neurons, receptor classification and brain development. It covers neuron structure and function, receptor types, sensory and motor neurons. Also includes an overview of how the brain develops from vesicles.