Neurohistology Flashcards
Where are the location of neuronal cell bodies in the CNS? PNS?
CNS - Gray matter, deep nuclei
PNS - ganglia
Where are the locations of axons in the CNS? PNS?
CNS - white matter
PNS - nerves
What is the are dendritic spines?
Transient membrane protrusions that increase the surface area for synapses on dendrites
Important in neural plasticity
What are the features of the neuronal soma?
Large nucleus with prominent nucleolus
Presence of Nissl bodies
Typical organelles
Lipofuscin
What are Nissl bodies?
RER and polyribosomes
grainy apprearance
What is the axon hillock?
Location of action potential initiation
Describe anterograde transport
Movement forward from the soma to the axon terminal
Uses kinesin
Transport of cytoskeletal proteins occurs more slowly
Describe retrograde transport
Movement backward from the axon terminal to the soma
Uses dynein
Describe multipolar neurons
Multiple dendritic processes
Characteristic of motor neurons and interneurons
Describe bipolar neurons
One main dendrite and one axon
Characteristic of special sensory neurons (e.g. vision, olfaction, hearing)
Describe pseudounipolar neurons
Single bidirectional axon-peripheral process and a central process
Characteristic of sensory neurons in the dorsal root ganglia
What are the four glial cells of the CNS?
Astrocyte
Oligodendrocyte
Ependymal cell
Microglia
What are the functions of astrocytes?
Formation of the Blood-brain barrier
Nutritional support
Uptake of neurotransmitters
Regulation of extracellular ionic concentrations
What is the function of ependymal cells?
Line the ventricles of brain and central canal of spinal cord
Produce cerebrospinal fluid
Apical ends have cilia and microvilli
What are microglial cells?
Small cells with mobile processes that sense the environment
Change shape when activated and begin to phagocytose damaged/foreign cells
Derived from monocytes
Important for immune surveillance
What is the function of oligodendrocytes?
Myelinates axons in the CNS
One cell can myelinate multiple internodes of one or more neurons
What are the supportive cells of the PNS?
Schwann cells
Satellite cells
What is the function of Schwann cells?
Meylinates internodes in the PNS
One schwann cell wraps one internode of one neuron
Also envelop small diameter neurons and provide support, but don’t myelinate them
How is gray and white matter oriented in the brain?
Gray matter on the outside (cerebral cortex)
White matter on the inside
How is gray and white matter oriented in the spinal cord?
Gray matter on the inside
White matter on the outside
What are meninges?
Connective tissue membranes that wrap the brain and spinal cord
What is the Dura mater and what two layers make it up?
The outermost and toughest CT membrane
Periosteal layer
Meningeal layer
What is the periosteal layer?
Layer of the dura mater attached to the bone of the sull
Trauma may cause bleeding between bone and dura
–epidural hematoma
What is the meningeal layer?
Will separate to form the walls of a dural sinus and rejoin to form a dural fold
What is the arachnoid mater?
Layer between the dura mater and pia mater
Contains spider web-like extensions that cross the subarachnoid space
Where is the subarachnoid space and what does it contain?
Located between the arachnoid and pia mater
Contains cerebrospinal fluid
What is the Pia mater?
A delicate, highly vascularized layer that is intimately applied to the surface of the brain and spinal cord
Describe the cerebral cortex
Gray matter in the cerebrum that is organized into 6 layers
Pyramidal cells are located here, major output comes from layer V
What are the layers of the cerebellum?
Molecular layer
Granular layer
Medulla (white matter)
What are the layers of the cerebellar cortex?
Molecular layer
Purkinje cell layer
Granular layer
What does the dorsal horn contain?
Terminal portion of somatosensory neurons
What does the ventral horn contain?
Somatomotor neurons
What connective tissue layers cover nerves in the PNS?
Epineurium - surrounds entire nerve
Perineurium - surrounds nerve fibers bundled in fascicles
Endoneurium - surrounds individual axon
What are tactile (Meissner’s) corpuscles?
Encapsulated sensory receptor located in the dermal papillae of thick skin
Modality - light touch, texture
What are Lamellar (Pacinian) corpuscles?
Encapsulated sensory receptor located deep in the dermis
Modality - deep pressure, vibration, stretch
What sensory receptors are responsible for propioception?
Muscle spindles
Tendon organ
What are the two unencapsulated sensory receptors?
Free nerve endings - pain, heat, cold
Hair receptors - light touch, movement of hair
Describe filiform papillae of the tongue
Smallest and most numerous
Keratinized tips
Sense texture of food
No taste buds
Describe fungiform papillae
Mushroom shaped
Scattered widely over the tongue
Taste buds
Describe circumvallate papillae
Located towards the back of the tongue
Taste buds are embedded on the lateral aspects
Describe folaite papillae
Located on the posterolateral aspect of the tonuge
Associated with taste buds, but not well developed in humans
What three types of cells do taste buds contain?
Taste receptor cells
Supporting cells (sustentacular cells)
Basal cells
Where is the olfactory epithelium located?
Upper 1/3 of the nasal cavity
What type of neurons are located in the olfactory epithelium?
Bipolar neurons
How do the olfactory sensory neurons synapse with the olfactory bulb?
The travel through the holes in the cribriform plate of the ethmoid bone
