L119 Histology of the Nervous System

Question 1

What are glial cells?

Answer 1

Supportive cells to neurons. Include Astrocytes, Oligodendrocytes, Schwann Cells, Ependymal cells, Satellite cells of ganglia

Question 2

Which cells provide immune function in the CNS?

Answer 2

Microglial cells are similar to macrophages.

Question 3

What is the structure/function of ependymal cells?

Answer 3

Low columnar or cuboidal cells. These cells have no basement membrane! Sometimes are ciliated to aid with CSF flow.
Line the spinal cord and the choroid plexus of ventricular system.

Question 4

True/False. Neurons have high metabolic and protein synethesis activity in general.

Answer 4

False. Neurons have high protein synthesis but low metabolic activity in general.

Question 5

Which histological stain is best used to visualize sometimes and dendrites?

Answer 5

Silver stain (ex. golgi stain).

Question 6

Which 3 components of neurons contribute to their morphologic appearance?

Answer 6

Intermediate filaments (permanent), Actin (dynamic, shape change), and Microtubules (dynamic, axon transport)

Question 7

Explain what it means for the neuron to be polarized?

Answer 7

Signals are received by dendrites (projections/processes extending from the soma) and transmitted to other neurons via axons.

Question 8

How does neuron cell receive and output signals?

Answer 8

The neuron receives input via passive electrotonic spread to its dendrites.
It delivers output via action potentials through the axon (taking advantage of Na/K pump driven membrane potential).

Question 9

What neuron characteristics are visible on H&E?

Answer 9

Nissl bodies are protein synthezing machinery (rough er, ribosomes, etc). They stain darkly blue in neurons.

Neurons synthesize ++ protein to build cytoskeleton, ion channels, receptors, etc.

Question 10

What are the passive and active support functions of astrocytes?

Answer 10

Passive:
Neurotransmitter uptake & degradation.
K++ homeostasis
Maintenance of BBB
Neuronal energy supply
Injury response and recovery

Active:
Modulation of neuronal function
Modulation of blood flow

Question 11

What type of stimuli may activate glial cells (astrocytes)?

Answer 11

Via modulations of intracellular calcium, initiated by neurotransmitters (ex. glutamate), trauma, spontaneous, or inflammatory mediators.

Question 12

Describe the relationship of glutamate and GABA to neuron transmission?

Answer 12

Glutamate is an excitatory amino acid neurotransmitter, there are glutamate transporters on glial cells.
GABA is an inhibitory amino acid neurotransmitter.

Question 13

How do glial cells communicate with each other?

Answer 13

Like neuron’s, glial cells also have synaptic vesicles and also conduct exocytosis.

Question 14

How do glial cells actively regulate neural function?

Answer 14

Release of ATP from glia and subsequent calcium wave causes of chemicals from glial cells, inhibiting neuron activity.
Neurons become hyperpolarized in the presence of Calcium wave.

Question 15

Describe the relationship of astrocytes with blood vessels?

Answer 15

Astrocytes wrap around blood vessels, close interaction–> integral to the Blood Brain Barrier.

Calcium release by astrocytes will cause vasoconstriction or vasodilation in adjacent blood vessels.

Question 16

What is the function of oligodendrocytes and schwann cells? Describe their interaction with neurons?

Answer 16

These cells provide myelination of axons. Oligodendrocytes are present in the CNS and schwann cells are in the PNS.
Provide electrical insulation for axons to speed up conduction of impulses (same achieved through increasing axon diameter).

Oligodendrocytes wrap around several different axons. Schwann cells only interact with one axon.

Question 17

What are nodes of ranvier?

Answer 17

Small gaps in between myelin sheath sections. They contain ion channels, allowing the impulse to jump accross to the next myelin sheath.

Question 18

What is the role of microglia in the CNS?

Answer 18

The immune cells of the CNS. They are derived from bone morrow, and phagocytic but distinct from macrophages.

In response to injury or insult they will up-regulate growth factors and cytokines.

Question 19

Structure of peripheral nerves?

Organize structure of PN from inside to outside.

Answer 19

These are composed of one or more bundles of nerve fibres, called Fascicles.

Each of these fascicles is surrounded by collagenous layer of perineurium.

If there is many fascicles, they will be surrounded by a larger collagenous tissue layer of Epineurium.

Within each fascicle/nerve bundle is a nerve cell and schwann cell sorrounded by loose vascular supporting tissue called Endoneurium.

Epineurium–>Perineurium–>Fascicles(nerve bundle)
—>Endoneurium–>Nerve fibre + schwann cell (b/c PNS)

Question 20

What are Ganglia?

Answer 20

Collection of cell bodies, ex dorsal root ganglion; as well as nerve fibres and satellite cells (supporting cells, glial-like)

Two types of Ganglia:

1. Sensory
   - house the cell bodies of sensory ganglion
2. Autonomic ganglia
   - house the cell bodies of post-ganglionic neurons