Nerve Structure

Question 1

What is the perikaryon?

Answer 1

The cell body of the nerve

Question 2

Give two other terms synonymous with terminal bouton.

Answer 2

Presynaptic neurone and axon terminal

Question 3

Describe some distinguishing features of synaptic junctions under an electron microscope.

Answer 3

. Electron dense layer on postsynaptic side

. Neurotransmitter vesicles on presynaptic side

Question 4

Describe the surface area: cytoplasm ratio of neurones.

Answer 4

Very large surface area: cytoplasm ratio

Question 5

Why do neurones need lots of rough endoplasmic reticulum?

Answer 5

Neurones have a very large surface area of membrane, so need lots of RER to produce lots of proteins to maintain the membrane.

Question 6

What are Nissl bodies? How do these appear on electron micrographs?

Answer 6

Nissl bodies are clumps of RER. They appear as dark dots.

Question 7

What is a pseudounipolar neurone? Why is this structure sometimes beneficial?

Answer 7

. Neurone with perikaryon pushed to one side

. Means that the path along dendrites and axon is as uninterrupted as possible for maximal transduction speed

Question 8

Very long axons utilise an efficient transport system to aid transduction. Describe this system.

Answer 8

. Microtubuli and neurofilaments used as rails, kinesin and dynein used as vehicles to move ions

Question 9

Why are the majority of brain tumours of glial origin?

Answer 9

Glial cells are capable of mitosis, so have the potential to divide uncontrollably, but neurones are post-mitotic therefore can’t divide uncontrollably.

Question 10

Name the three main glial cells.

Answer 10

Astrocytes, oligodendrocytes, microglia

Question 11

What are astrocytes?

Answer 11

. Glial cells whose ‘feet’ touch neurones, other glial cells, and capillaries
. Take nutrients from capillaries and transfer them to neurones
. Form blood brain barrier and seal on CNS surface

Question 12

What are oligodendrocytes?

Answer 12

Glial cells that make myelin

Question 13

What forms the myelin sheaths in the central nervous system and peripheral nervous system?

Answer 13

. CNS- oligodendrocytes from myelin sheath

. PNS- Schwann cells form myelin sheath

Question 14

What are microglia cells?

Answer 14

. Immune cells in CNS
. Can release cytokines to attract other immune cells, can phagocytose pathogens and act as local APCs
. Also involved in maintenance and remodelling of CNS, e.g. removing underused synapses

Question 15

How do you identify astrocytes, oligodendrocytes, and microglia under the microscope?

Answer 15

. Astrocytes- larger lighter oval nuclei
. Oligodendrocytes- compact round dark nucleus, sometimes with granulation
. Microglia- bean-shaped, more elongated

Question 16

What is epineurium?

Answer 16

Connective tissue surrounding fascicles of axons

Question 17

What is perineurium?

Answer 17

Connective tissue that bundles axons into fascicles

Question 18

What is endoneurium?

Answer 18

Connective tissue between axons within a fascicle

Question 19

How many myelin sheaths does one Schwann cell produce?

Answer 19

One Schwann cell produces one myelin sheath (in PNS)

Question 20

Why do axons have slack?

Answer 20

So that if they are stretched they don’t snap

Question 21

Name the type of cell which covers perikarya in peripheral nervous system ganglia

Answer 21

Satellite cells

Question 22

What does the central nervous system consist of?

Answer 22

The brain and spinal cord, surrounded by cerebrospinal fluid

Question 23

What does the peripheral nervous system consist of?

Answer 23

Peripheral nerves and ganglia, surrounded by interstitial tissue and interstitial fluid

Question 24

Where is the location of the perikarya and axons of afferent and efferent neurones?

Answer 24

. Afferent neurones have their perikarya in the PNS and their axons in the CNS
. Efferent neurones have their perikarya in the CNS and their axons in their CNS

Question 25

What are ganglia?

Answer 25

Clusters of PNS perikarya

Question 26

What are nuclei? (in terms of nerves)

Answer 26

Clusters of CNS perikarya