Lecture 6 - Nervous Tissue Flashcards
What are the three basic components of a neuron?
Cell body, axon, dendrites
Type of neuron where a single process extends from the cell body and then divides into two branches.
Pseudounipolar
Type of neuron with irregularly shaped body & more than two cell process: an axon and multiple dendrites
Multipolar
What is a Nissl body/substance?
it is the highly developed and easily visible rER of neurons.
Where is the initial segment and what is the significance of the initial segment of an axon?
The initial segment of the axon follows the axon hillock and exists as a slight narrowing in the axon. It has the lowest threshold of excitability.
What allows orthograde transport down axons?
Kinesis: (+) end directed motor protein
Where is the axon hillock located and what does it look like?
It appears at the initial segment of the axon (as it leaves the cell body) and it images as clear area.
What allows retrograde transport up axons?
Dynein: (-) end directed motor protein
What is the function of dendritic spines?
Structures specialized for synaptic contact
What cytoskeletal elements exist in dendritic spines?
Actin, some microtubules, very few neurofilaments (which are 10nm intermediate filaments within neurons)
Name for synapse between:
1) axon and dendrites
2) axon and cell body
3) axon and axon
4) axon and dendritic spine
5) dendrite and dendrite
1) axodendritic
2) axosomatic
3) axoaxonic
4) axospinous
5) dendrodendritic
What induces fusion of synaptic vesicles with axon terminal membrane?
Depolarization (Ca2+ channels allow influx of Ca2+)
How wide is the synaptic cleft?
20nm
What structures characterize the presynaptic process?
40-60nm synaptic vesicles & mitochondria
List the types of neuroglia present in the CNS. (4 types)
Astrocytes, Oligodendrocytes, Microglia, Ependymal cells
What produce myelin sheaths in the CNS? PNS?
CNS: Oligodendroctyes
PNS: Schwann cells
Where are astrocytes located relative to mater layers of CNS?
under pia mater
What type of astrocytes have granular cytoplasm with short think branches?
Protoplasmic astrocytes (CNS gray matter)
What type of astrocytes have long slender, infrequently branches processes?
Fibrous astrocytes (CNS white matter)
What is the primary role of astrocytes?
Assist in maintenance of electrolyte balance in CNS & nutrient transport to neurons
What is unique about the nucleus of microglia?
It is condensed and elongated.
Phagocytic cells in CNS that are derived from monocytes.
Microglia
Where are ependymal cells located?
Line neural tubes and ventricles of brain.
What is the choroid plexus?
Ependymal cells & associated capillary loops that are modified to produce CSF.
From what type of cell do Schwann cells originate?
Neural crest cells
What are the three types of nerve fibers? Include speed of signal transduction with each.
Type A: large, myelinated, long internodes (space between nodes of Ranvier), high velocity 15-100 m/s
Type B: Smaller diameter, shorter internodes, medium conduction velocity 3-14 m/s
Type C: Thin, non-myelinated, slow velocity 0.5-2 m/s
What is the name for the connective tissue layer surrounding an entire nerve?
Epineurium
What is the name of the sheath surrounding a single neuron (Schwann cell sheath)?
Neurolemma
What is the name for the connective tissue layer that surrounds a nerve fiber bundle.
Perineurium
What is the name for a group of Schwann cell sheathed axons within the perineurium?
Endoneurium
Define ganglion.
Aggregation of nerve cell bodies outside of the CNS
What class of neurons typically makes up a DRG?
Pseudounipolar
What class of neurons typically makes up a sympathetic root ganglion?
Multipolar
What is the size/function of neurons make up the anterior horn?
Large motor neurons that terminate at muscle in motor end plates
What is the size/function of neurons make up the posterior horn?
Small nerve cells which receive afferent impulses from sensory nerve cells
What is the size/function of neurons make up the lateral horns?
Intermediate size nerve cells which send axons to autonomic ganglia
What is the function of Pacini’s corpuscles and where are they located? Also, what do they look like? (i.e. What is their general shape?)
Sense vibration, pressure, and tension. Located in subcutaneous tissue of finger pads, peritoneum, tendons and ligaments, around viscera. They are round. Look like an onion.
What is the function of Meissner’s corpuscles and where are they located?
Touch receptors (mechanoreceptors) that are numerous in dermal papillae of finger pads. Also found in lips, genital skin, edge of eyelids. These are involved in two point discrimination.
What makes up the blood-brain barrier?
Cells processes of astrocytes
Drugs with what property can cross the blood-brain barrier?
Lipid soluble (lipophilic)
What is the size cutoff for substances entering the blood-brain barrier?
> 500 daltons restricted
