Cells of the Nervous System

Question 1

Features of Neurons

Answer 1

• Large Nucleus
• Prominent Nucleolus
• Abundant rER
• Well developed Golgi (need to transport proteins long distances)
• Abundant mitochondria
• Highly organised cytoskeleton
• Highly organised metabolically active cell

Question 2

What are dendrites?

Answer 2

• spread from cell body, branch frequently
• dendrites have protusions (spines) these receive majority of synapses
• large pyramidal neurones can ahve 30-40,000 spines.
• primary dendrites come off pyramid vertices
• secondary branch of primary
• Purkinje cells (lpn) in the cerebellum.

Question 3

What are Axons?

Answer 3

• Emerge at the Axon Hillock, one per cell.
• can branch after leaving cell body (axon collaterals)
• maintains same diameter.
• contains intermediate filaments and microtubules.
• can b myelinated/unmyelinated.

Question 4

Types of Axon Terminals?

Answer 4

Boutons - typical synaptic bulb

Varicosities - axons synapse with many smooth muscle cells as it passes.

Question 5

What do Synpases contain?

Answer 5

Abundant Mitochondria - 45% of total energy used is for ion pumping and synaptic transmission.
Synapses receive excitatory and inhibitory input depending on the neurotransmitters used - neuronal integration.

Question 6

Types of Synaptic Organisation?

Answer 6

Axo-Dendritic = Excitatory
Axo-Somatic = Inhibitory
Axo-Axonic = Modulatory

Question 7

Describe the Neuronal Cytoskeleton?

Answer 7

Neurofilaments - role in determining axon caliber

Microtubules - abundant in the nervous system.

Question 8

Subtypes of Neurons

Answer 8

Pseudounipolar:

• sensory neurons
• 2 fused processes that are axonal
• signal passes to axon terminal without going to soma.

Bipolar:
- involved in the white matter of cerebral cortex

Multipolar:

• pyramidal cells = cerebral cortex
• purkinje cells = cerebellum
• anterior horn cells = spinal cord
• retinal ganglion cells
• Stellate cells = cerebral cortex + cerebellum

Question 9

Axonal damage in MS?

Answer 9

Restriction to axon ( Traumatic injury/Inflammatory disease) - leads to swellings.
Swellings = vesicles of neurotransmitter transported and accumulated down the axon.

Question 10

Neuroglia cell types?

Answer 10

Astroglia
Oligodendroglia
Microglia
Immature Progenitors
Ependymal cells
Schwann cells
Satellite glia

Question 11

What are Astroglia?

Answer 11

• Multi-processed (star shape)
• Most numerous cell type
• contain intermediate filament bundles in the cytoplasm
• contain gap junctions

Question 12

Functions of Astroglia

Answer 12

• Scaffold for neuronal migration and axon growth in development
• formation of blood-brain barrier
• transports substances from blood to neurons
• separates synapses
• removes neurotransmitter from synapse
• involved in glial scar formation
• k+ buffering

Question 13

What are Oligodendroglia?

Answer 13

Two types:

• interfascicular
• perineuronal
• small spherical nuclei
• few thin processes
• prominent ER and Golgi
• Metabolically highly active

Question 14

Function of the Oligodendroglia

Answer 14

Produce and maintain myelin sheath (1-40 per myelin sheaths per cell)

Question 15

What is Myelin?

What are some Myelin Disease States?

Answer 15

Lipid rich insulating material
- 50 layers

Multiple Sclerosis - loss of myelin due to autoimmune response

Adrenoleukodystrophy - –> progressive loss of myelin

Question 16

What are Microglia? Function?

Answer 16

Immune cells of the CNS

• developed in the bone marrow
• resident macrophage of the CNS
• involved in immune surveillance
• present antigens to invading immune cells
• first cells to react to infection or damage.
• Involved in synaptic stripping and tissue remodelling

Question 17

What are Schwann Cells?

Answer 17

• Myelin producing cells of the PNS
• Each cell produces one myelin sheath
• promotes axon regeneration
• wrap around the nerve axon