Neuroscience 2 - Cells of the Nervous System

Question 1

Describe the internal structure of the neurone.

Answer 1

• Large nucleus
• Prominent nucleolus
• Abundant rough ER
• Well developed golgi
• Many mitochondria
• Highly organised cytoskeleton

Question 2

Describe the structure of the dendrites of neurones.

Answer 2

• They spread from the cell body and branch frequently
• Covered in protrusions called spines
• Spines recieve the majority of synapses
• Primary dendrites split into secondary dendrites and then these split into tertiary dendrites.

Question 3

Describe the structure and function of axons of neurones.

Answer 3

• These conduct impulses away from the cell body
• Emerge from the axon hillock
• One per cell
• May branch after leaving the cell body and at the target
• Has prominent microtubules and neurofilaments (for structural support)
• Myelinated or unmyelinated

Question 4

Describe the structure of axon terminals

Answer 4

• Axons branch extensively close to the target, forming a synaptic terminal
• Boutons are right at the end of the axon
• Varicosities are swellings on the axon containing neurotransmitters

Question 5

Describe the structure of the synapse

Answer 5

• Synaptic vesicles are packaged in the golgi

- Many mitochondria, required for ion pumping.

Question 6

List the types of synapse

Answer 6

• Axo-dendritic (excitatory)
• Axo-somatic (inibitory)
• Axo-axonic (modulatory)

Question 7

Which part of the neurone do the axo-dendritic synapses communicate with?

Answer 7

The axon communicates with the dendrites

Question 8

Which part of the neurone do the axo-somatic synapses communicate with?

Answer 8

They communicate with the cell body (soma)

Question 9

Which part of the neurone do the axo-axonic synapses communicate with?

Answer 9

They reduce the action potential on the axon of another neurone, preventing stimulation of the following neurone.

Question 10

Describe the process of transport across the axon.

Answer 10

• Vesicles are transported up or down the neurone via motor proteins on microtubules.
• The microtubules have different ends. One end is positive, and the other is negative. The positive end is at the bottom of the axon.
• Different constituents are used for retrograde transport (from + to -) and anterograte transport (from - to +)

Question 11

Where are pseudounipolar neurones found?

Answer 11

Sensory neurones, they have one axon that splits into two

Question 12

Where are bipolar neurones fond?

Answer 12

They are retinal, in the cerebral cortex white matter.

Question 13

Describe the structure and function of golgi type 1 multipolar neurones.

Answer 13

• Highly branched dendritic trees
• Axons extend long distances
• Pyramidal cells of the cerebral cortex
• Purkinje cells of the cerebellum (15 mill)
• Anterior horn cells of the spinal cord
• Retinal ganglion cells

Question 14

Describe the structure and function of golgi type 2 multipolar neurones.

Answer 14

• Highly branched dendritic trees
• Short axons
• Axons terminate quite close to cell body
  of origin
• Stellate cells of the cerebral cortex
  and cerebellum

Question 15

Describe the structure of astroglia

Answer 15

• Multiprocessed starlike shape
• Most numerous cell
  type
• Numerous
  intermediate
  filament bundles in
  cytoplasm of fibrous
  astroglia (GFAP)
• Gap junctions
  suggest astroglia-astroglia signalling

Question 16

Describe the functions of astroglia

Answer 16

1. Scaffold for neuronal migration and axon growth
   during development.
2. Formation of blood-brain barrier.
3. Transport of substances from blood to neurons.
4. Segregation of neuronal processes (synapses).
5. Removal of neurotransmitters.
6. Synthesis of neurotrophic factors.
7. Neuronal-glial and glial neuronal signalling
8. Potassium ion buffering
9. Glial scar formation

Question 17

Describe the process by which astrocytes remove neurotransmitters.

Answer 17

• The end foot of astrocytes interfere with neurotransmitters in the synapse.
• They transport the neurotransmitters into the cell, alongside potassium and water.

Question 18

Describe the structure of oligodendroglia.

Answer 18

• Small spherical nuclei
• Few thin processes
• Prominent ER and Golgi
• Metabolically highly
  active

Question 19

Describe the functions of oligodendroglia .

Answer 19

- Production and
maintenance of the
myelin sheath
- Each cell produces
multiple sheaths

Question 20

Describe the structure of myelin.

Answer 20

- A lipid rich insulating
membrane
- Up to 50 lamellae (thin membranes)
- Dark and light bands
seen at EM level

Question 21

Describe the function of microglia.

Answer 21

• Resident macrophage population of the CNS
• Involved in immune surveillance
• Present antigens to invading immune cells
• First cells to react to infection or damage
• Role in tissue modelling
• Synaptic stripping

Question 22

Where are microglia derived from?

Answer 22

Bone marrow

Question 23

Describe the structure of schwann cells.

Answer 23

• Schwann cells perform the function of the astrocytes and the oligodendrocytes
• They myelinate a single axon.
• They promote axon regeneration

Question 24

Why cant axons be myelinated by single cells in the CNS as occurs in the PNS?

Answer 24

This would take up more space; the brain would need to be considerably bigger.