Nervous Tissue II (Lecture 9) Flashcards
what is the main difference between axons and dendrites?
axons have supporting cells and frequently have myelin covering
dendrites are always naked and have no supporting glial cells
what directions does axonal transport go and what are the speeds?
directions: anterograde and retrograde
speeds: fast and slow
define anterograde axon transport
what speed does it travel?
-AWAY from cell body; transport synaptic vesicle protein down the axon for potential exocytotic release
FAST OR SLOW
define retrograde axon transport
what speed does it go?
-TOWARD cell body; cell membranes returned to cell body for reuse or degradation
JUST FASt
what are the four basic types of synapses?
1) axodendritic
2) axoaxonic
3) axosomatic
4) neuromuscular
how can you tell if it is a bouton or a dendrite?
dendrite end of the synapse will have vesicle like structures, but will not be as dense as in synaptic vesicles/boutons
what is a neuromuscular synapse?
axon connects to muscle tissue
release of ACh from the motor neuron propagates an action potential within the muscle fiber
where are pseudounipolar neurons found?
found in sensory ganglia
confined to spinal nerve sensory ganglia and some cranial nerves
what are ganglia?
clusters of cell bodies
what are satellite cells?
glia that form a complete ring around pseudounipolar neuron cell bodies
in determining if you are looking at CNS or PNS, what clue can you be looking for?
histology slide will have blue stained structures
the blue indicates that they are connective tissue capsule containing the cell bodies
THERE IS NO CT IN CNS SO THIS IS IMMEDIATE CLUE
name the 4 types of glia cells/where they are found
1) astrocytes
2) microglia
3) schwann cells –> PNS ONLY
4) oligodendrocytes –> CNS ONLY
what do microglia do?
-10-15% can be found in CNS
-remove damaged neurons and infectious agents
-RULE OF THUMB: form the primary immune defense of CNS
what do astrocytes do?
have feet that support the blood brain barrier and the glia limitans (barrier between pia mater and CNS)
LOOK LIKE STARS
what are schwann cells?
-myelinate PNS axons!!!
-single internodal segment
-basal lamina guides regenerating axons
what are oligodendrocytes?
can myelinate more than one axon and more than one internodal segment per axon
CNS ONLY!!
what is the saltatory conduction?
where the action potential jumps from node to node
what do the pink dots represent?
how about the pale circles around the pink dot?
pink dots: axons
circle: myelin
are unmyelinated axons truly “naked?”
no, they are not truly without schwann cells
still partially covered and can be found where conduction speed along axon is not entirely important
why does the peripheral nerve in this picture appear wavy?
because peripheral tissue contains connective tissue
what are the three types of connective tissue?
epineurium, perineurium, endoneurium
define epineurium
fibrous coat around whole nerve
also fills space between nerve fibers
define perineurium
surrounds each bundle of nerve fibers
define endoneurium
envelops the myelin sheaths of individual axons
composed of reticular fibers
produced by the Schwann cells
