Nervous Tissue II (Lecture 9)

Question 1

what is the main difference between axons and dendrites?

Answer 1

axons have supporting cells and frequently have myelin covering

dendrites are always naked and have no supporting glial cells

Question 2

what directions does axonal transport go and what are the speeds?

Answer 2

directions: anterograde and retrograde

speeds: fast and slow

Question 3

define anterograde axon transport

what speed does it travel?

Answer 3

-AWAY from cell body; transport synaptic vesicle protein down the axon for potential exocytotic release

FAST OR SLOW

Question 4

define retrograde axon transport

what speed does it go?

Answer 4

-TOWARD cell body; cell membranes returned to cell body for reuse or degradation

JUST FASt

Question 5

what are the four basic types of synapses?

Answer 5

1) axodendritic
2) axoaxonic
3) axosomatic
4) neuromuscular

Question 6

how can you tell if it is a bouton or a dendrite?

Answer 6

dendrite end of the synapse will have vesicle like structures, but will not be as dense as in synaptic vesicles/boutons

Question 7

what is a neuromuscular synapse?

Answer 7

axon connects to muscle tissue

release of ACh from the motor neuron propagates an action potential within the muscle fiber

Question 8

where are pseudounipolar neurons found?

Answer 8

found in sensory ganglia

confined to spinal nerve sensory ganglia and some cranial nerves

Question 9

what are ganglia?

Answer 9

clusters of cell bodies

Question 10

what are satellite cells?

Answer 10

glia that form a complete ring around pseudounipolar neuron cell bodies

Question 11

in determining if you are looking at CNS or PNS, what clue can you be looking for?

Answer 11

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

Question 12

name the 4 types of glia cells/where they are found

Answer 12

1) astrocytes
2) microglia
3) schwann cells –> PNS ONLY
4) oligodendrocytes –> CNS ONLY

Question 13

what do microglia do?

Answer 13

-10-15% can be found in CNS

-remove damaged neurons and infectious agents
-RULE OF THUMB: form the primary immune defense of CNS

Question 14

what do astrocytes do?

Answer 14

have feet that support the blood brain barrier and the glia limitans (barrier between pia mater and CNS)

LOOK LIKE STARS

Question 15

what are schwann cells?

Answer 15

-myelinate PNS axons!!!

-single internodal segment
-basal lamina guides regenerating axons

Question 16

what are oligodendrocytes?

Answer 16

can myelinate more than one axon and more than one internodal segment per axon

CNS ONLY!!

Question 17

what is the saltatory conduction?

Answer 17

where the action potential jumps from node to node

Question 18

what do the pink dots represent?

how about the pale circles around the pink dot?

Answer 18

pink dots: axons

circle: myelin

Question 19

are unmyelinated axons truly “naked?”

Answer 19

no, they are not truly without schwann cells

still partially covered and can be found where conduction speed along axon is not entirely important

Question 20

why does the peripheral nerve in this picture appear wavy?

Answer 20

because peripheral tissue contains connective tissue

Question 21

what are the three types of connective tissue?

Answer 21

epineurium, perineurium, endoneurium

Question 22

define epineurium

Answer 22

fibrous coat around whole nerve

also fills space between nerve fibers

Question 23

define perineurium

Answer 23

surrounds each bundle of nerve fibers

Question 24

define endoneurium

Answer 24

envelops the myelin sheaths of individual axons

composed of reticular fibers

produced by the Schwann cells