Histology of the nervous system

Question 1

intercellular neuron

Answer 1

communication within the cell - chemical

Question 2

intracellular neuron

Answer 2

communication between cells through gap junctions - electrical

Question 3

sensory information flow

Answer 3

from sensory receptors to the CNS (somatic and visceral)

Question 4

motor information flow

Answer 4

from CNS to effector tissues/organs (somatic and visceral)

Question 5

interneurons

Answer 5

form communication and integration network between sensory and motor neurons

Question 6

dendrites

Answer 6

part of a neuron, involved in input (afferent communication)

• Nissl body
• cytoskeleton
• mitochondria

Question 7

axon

Answer 7

part of a neuron, involved in output (efferent communication)

• hillock - site of origin of axon
• initial segment - between hillock and start of myelin, site of action potential generation
• terminal - site of synapses
• no Nissl body

Question 8

soma (cell body)

Answer 8

integrate electrical signals, synthesize macromolecules

• prominent nucleolus
• large golgi apparatus
• NIssl body (composed of RER and ribosomes)
• cytoskeleton
• mitochondria

Question 9

neuron structure

Answer 9

1) dendrite
2) soma (cell body)
3) axon

Question 10

chemical synapse

Answer 10

conduction of impulse achieved by release of chemical substance (neurotransmitter)

neurotransmitter diffuses across synaptic cleft to stimulate post synaptic cell

Question 11

electrical synapse

Answer 11

gap junctions, ions diffuse between cells

occurs in cardiac and smooth muscle, crystalline lens

Question 12

chemical synapse structure

Answer 12

1) presynaptic membrane (axon) - vesicles contain neurotransmitters
2) postsynaptic membrane (dendrite) - receptors on plasma membrane
- asymmetric = excitatory
- symmetric = inhibitory

Question 13

axonal transport

Answer 13

materials move along microtubules and neurofilaments in a bidirectiona manner

Question 14

kinesin

Answer 14

anterograde transport - carries material from nerve cell body to periphery (towards synpase)

Question 15

dynein

Answer 15

retrograde transport - carries material from axons and dendrites to nerve cell body (away from synapse)

Question 16

differences between axons and dendrites

Answer 16

• dendrites are shorter with larger diameter
• dendrites are unmyelinated
• dendrites have larger surface area for synaptic input due to extensive branching and dendritic spines (knob-like projections)

Question 17

bouton terminal (nerve to nerve)

Answer 17

single synapse from axon

Question 18

boutons en passant (nerve to nerve)

Answer 18

multiple synapses from a single axon

Question 19

neuromuscular junction (nerve to muscle)

Answer 19

en plaque motor end plate

Question 20

multipolar neurons

Answer 20

single axon, two or more dendrites

• pyramidal cells (golgi type I neurons)
• purkinje cells
• stellate cells (golgi type II neurons)
• granule cells

Question 21

pseudo-unipolar neurons

Answer 21

axon/dendrite are fused

Question 22

bipolar neuron

Answer 22

single axon, single dendrite

Question 23

pyramidal cells (multipolar)

Answer 23

golgi type I neurons
- soma is pyramid-shaped
- in cerebral cortex
- long axons, leave grey matter

Question 24

purkine cells (multipolar)

Answer 24

• flask-shaped soma
• in cerebellar cortex
• lots of dendrites

Question 25

stellate cells (multipolar)

Answer 25

golgi type II neurons
- start-shaped soma
- in cerebral and cerebellar cortex
- axons stay in grey matter

Question 26

granule cells (multipolar)

Answer 26

• small stellate cells
• in cerebellum
• like grains of sand

Question 27

pseudo-unipolar neurons

Answer 27

primary sensory neurons, pseudo because they don’t only go in one direction, one axon, one dendrite

Question 28

bipolar neurons

Answer 28

associated with special senses

• retina
• ear and olfactory epithelium

Question 29

glial cells

Answer 29

found in CNS and PNS, non-neuronal (not involved in signalling), involved in metabolic function

Question 30

schwann cells

Answer 30

glial cells in PNS
- electrochemical insulation
- myelinate axons
- envelope and nurture unmyelinated axons

Question 31

satellite cells

Answer 31

glial cells in PNS
- electrical insulation
- surround cell bodies of neurons
- metabolic exchanges

Question 32

myelin sheath

Answer 32

insulator that directly surrounds an axon
- neurilemma is continuous with myelin sheath, includes nucleus and cytoplasm of Schwann cell
- basal lamina is external to neurilemma

Question 33

myelin sheath development

Answer 33

1) membranes fuse together
2) portions not squeezed = clefts of Schmidt-Lanterman
3) myelin protein in major dense lines (cytoplasm)

Question 34

segmentation of myelin sheath

Answer 34

one axon, many schwann cells

Question 35

oligodendrocytes

Answer 35

neuroglia of the CNS
- produce and maintain myelin sheath
- small cells with a few processes, each process forms an internode
- no basal lamina or neurilemma

Question 36

astrocytes

Answer 36

neurglia of CNS
- start-shaped
- largest of neuroglial cells
- fibrous: white matter, few long processes, many intermediate filaments
- protoplasmic: grey matter, numerous short processes, few intermediate filaments

Question 37

microglia

Answer 37

neuroglia of CNS
- phagocytic

Question 38

ependymal cells

Answer 38

neuroglia of CNS
- line fluid-filled cavities of CNS (ventricles and central canal of spinal cord)
- produce CSF (choroid plexus)