Nervous Neuron Functional unit of the nervous system

Nervous

Neuron Functional unit of the nervous system. Contains 2 components Nerve Cell Body (Soma) ● Nucleus ● Nucleolus ● Perikaryon ● Organelles Cell Processes ● Axon ● Dendrites

Histological Types of Neurons Classification is based on function, location and polarity Unipolar neuron One process with axonal/dendritic properties Pseudounipolar neuron Both axon and dendrites arise from the NCB Bipolar neuron One axon and one dendrite Multipolar neuron One axon and multiple dendrites

Supporting Nervous Cells Neuroglial cells provide mechanical or metabolic support to neurons Peripheral Nervous System, PNS ● Schwann cells – produce/maintain myelin (Fig 1) ● Satellite cells - metabolic cells in the periphery of neurons (Fig 2) Central Nervous System, CNS ● Astrocytes – blood/brain barrier (Fig 3) ● Oligodendrocytes – produce/maintain myelin for CNS (Fig 4) ● Microglia – CNS phagocytes (Fig 5) ● Ependymal cells – secrete CSF (Fig 6)

Nerves

Nerve Cross Section C A: Epineurium B: Perineurium C: Endoneurium B A A

A B

Nerve Longitudinal Section A: Nerve axons B: Nodes of Ranvier A B

A

Neuron 3 C A: Nerve cell body B: Satellite cells B C: Epineurium A D: Endoneurium D

Central Nervous System

Spinal Cord E C 4. Spinal Cord A: White matter B: Grey matter C: Dorsal horn of grey matter. B A D: Ventral horn of grey matter. E: Posterior median sulcus. F: Anterior median fissure. D F

A C F D B E

Practice C A E B D A: Dorsal Horn B: Ventral Horn C: Posterior Median Sulcus D: Anterior Median Fissure E: Central Canal

Cerebrum A: White matter. B: Polymorphous or Multiform layer E D C C: Inner (Pyramidal) ganglionic layer B D: Inner granular A E: Outer pyramidal cell layer F: Outer granular G: Plexiform (Molecular) layer G F

Practice Name the layers from deep to superficial

Cerebellum A: White matter. B: Granular layer C C: Purkinje cell layer D D: Molecular layer B A

A B C

Practice D C B A A: White matter B: Granular Layer C: Purkinje Cell Layer D: Molecular Layer

Meninges The meninges comprise three layers of dense collagenous connective tissue regularly arranged which have protective and progenitor functions Dura Mater (DCCTRA) ● Outermost layer ● Forms a tough, inelastic bag that surrounds the brain and spinal cord Arachnoid Mater (DCCTRA) ● Resembles a spider ● Deep to the layer is the subarachnoid space and CSF Pia Mater (DCCTRA w/LCT) ● Innermost layer ● Highly vascular and adheres to surface of brain and spinal cord

Meninges A: Pia mater A B: Subarachnoid space C: Arachnoid mater C B

Clinical Connections

Meningitis • • Inflammation of the meninges caused by viruses, bacteria and other microorganisms Diagnosed via lumbar puncture and examination of CSF Can be life-threatening Treated using antibiotics and antiviral drugs Source: http: //neuropathologyweb. org/chapter 5 a. Suppurative. html

Cerebral hematoma • Observable brain contusion • Can be extradural, subdural, or intracerebral

Choroid Plexus B A A: Ependymal Cells B: Cerebellum.

Review Assuming that Professor Reynolds is “middle aged, ” describe his ependymal cells histologically. Sparsely ciliated simple cuboidal

Review Where do you find cells that produce CSF? Choroid plexus in the ventricles Spinal canal

Miscellaneous

Associated Nervous Tissue A: Auerbach’s Plexus (page 57). B: Meissner’s plexus (page 57). B A C: Intrafusal Fiber (page 35). D: Purkinje Fiber (page 41). D C

Multipolar Neuron A A: Dendrites B: Nerve cell body. B

Special Senses

Vision Photoreception ● Eye focuses light onto a special layer of cells ● Light is refracted as it passes through the cornea, pupil, and lens ● The cornea and lens project an inverted image onto the retina Retina ● Contains a large number of photoreceptor cells (rods and cones) ● Rods are active when the level of light is low ● Cones are specialized to absorb three different wavelengths of light (red, blue, and green)

Extra Info: Physics of the Eye

Retina A A: Inner limiting membrane. B: Optic nerve fiber layer. C: Ganglionic cell layer. B D: Inner plexiform. C E: Inner nuclear. F D G F: Outer plexiform. E G: Outer nuclear. H: Outer limiting membrane. I: Rods and cones (bipolar neurons). H I

A B F G E D C

Practice

Taste Chemoreception ● Allows perception of food and poisons ● Coupled with the sense of smell ● Taste sensations include saltiness, bitterness, sweetness, sourness, and umami ● Taste receptors located on the tongue, soft palate, pharynx, and epiglottis

Taste Bud A A: Stratified squamous epithelium B: Sustentacular cells B C C: Taste bud D: Taste pore D

Practice D A B C A: Stratified squamous B: Taste bud C: Skeletal muscle irregular D: Von ebners

Hearing Mechanosensation ● Allows perception of sound through external vibrations ● Vibrations are detected by the ear and transformed into nerve impulses ● Vibrations vary in both amplitude and frequency ● Hearing impairment is the inability to detect some frequencies and low amplitude

Cochlea D A: Hair cells with stereocilia A B: Tectorial Membrane C: Vestibular membrane. D: Basilar membrane. B E E: Scala Media. C

Practice

Smell ● Uses specialized sensory cells in the nasal cavity to detect odors ● Another form of chemoreception ● Chemicals pass into the nasal passage and dissolve in mucus lining the superior section of the cavity ● Chemicals are then detected by olfactory receptors on olfactory cells (Fig 4)

Olfactory A A: Bowman’s Gland. B: Olfactory receptor cells C: Ciliated pseudostratified columnar epithelium C B

Review What exocrine gland is associated with this tissue? Bowman’s Gland - SMBT

Clinical Connections

Teratoma • • Encapsulated tumor that results from abnormal development of pluripotent cells Tissue of a teratoma may be normal in itself, but differ from surrounding tissues They usually don’t contain organs, but have been found to contain hair, teeth, bone and complex organs including eyes The above image depicts a teratoma with tissue from all 3 germ layers Source: http: //en. wikipedia. org/wiki/Teratoma