neurones and all that

Question 1

when are neurons formed

Answer 1

• Mainly, but not exclusively, formed during brain development

Question 2

what do dendrites do

Answer 2

receive inputs (dendritic spines), transmit to cell body (soma)

Question 3

what are the 2 different types of synapse

Answer 3

• Chemical – majority

* Electrical – less, enable synchronised electrical activity

Question 4

where are synapses concentrated

Answer 4

dendritic spines

Question 5

types of Glia

Answer 5

Oligodendrocytes
Microglia
astrocytes

Question 6

oligodendrocytes

Answer 6

• Myelinating cells of CNS
• Unique to vertebrates
• Myelin insulates axon segments, enables rapid nerve conduction
• Myelin sheath segments interrupted by nodes of Ranvier – saltatory conduction
• Provide metabolic support for axons
• Can provide support for multiple axons

Question 7

what are Microglia

Answer 7

• Resident immune cells of the CNS
• Originate from yolk sac progenitors that migrate into CNS
• “Resting” state, highly ramified, motile processes survey environment (2-3 µm/min)
• Upon activation (e.g. by ATP), retract processes, become “amoeboid” & motile
• Proliferate at sites of injury - phagocytic

Question 8

functions of microglia

Answer 8

• Immune surveillance
• Phagocytosis – debris/microbes
• Synaptic plasticity – pruning

Question 9

what are astrocytes

Answer 9

• Star-like cells
• Most numerous glial cells in the CNS
• Highly heterogeneous – not all star-shaped
• Common ‘marker’ glial fibrillary acidic protein (GFAP)

Question 10

astrocyte morphology

Answer 10

• Fibrous – white matter, contact blood vessels, pia & nodes of ranvier
• Protoplasmic – grey matter, contact blood vessels and pia
Astrocytes contribute to blood-brain barrier – aquaporin 4

Question 11

astrocyte functions

Answer 11

• Developmental – radial glia
• Structural - define brain micro-architecture
• Envelope synapses – “tripartite synapse”
• Homeostatic – buffer K+, glutamate, etc.
• Metabolic support - Glutamate-Glutamine shuttle
• Neurovascular coupling (basis of fMRI)
• Proliferate in disease – gliosis/astrocytosis

Question 12

ependymal cells

Answer 12

• Epithelial-like, line ventricles & central canal of spinal cord
• CSF production, flow & absorption
• Ciliated – facilitates flow
• Allow solute exchange between nervous tissue & CSF

Question 13

choroid plexus

Answer 13

• Frond-like projections in ventricles
• Formed from modified ependymal cells, villi form around network of capillaries → highly vascularised & large surface area
• Main site CSF production by plasma filtration (driven by solute secretion)
• Gap junctions between cells form blood-CSF barrier