L1 - Introduction to Neurophysiology

Question 1

Glia cover the surface of neurons with the exception of the ____?

Answer 1

Synapse

Question 2

What do ependymal cells do?

Answer 2

They give rise to the epithelial layer surround the choroid plexus and the epithelial lining of the ventricles. In the ventricles, they possess cilia on their surfaces facing the open space of the cavities they line which beat in a pattern to influence the direction of flow of CSF & NT.

Question 3

Where is the choroid plexus located?

Answer 3

Lateral ventricles (the two largest ventricles, which occur as a pair in the cerebral hemispheres)

Question 4

Blood-brain barrier

Answer 4

A semipermeable membrane separating the blood from the CSF, and constituting a barrier to the passage of cells, particles, and large molecule.

Question 5

The number of astrocytes per neurons increase with increasing ________

Answer 5

Complexity e.g. humans have more than cats who have more than rats

Question 6

T/F: Astrocytes have their own territory

Answer 6

True

Question 7

Gap junctions – how is K+ transferred b/n astrocytes?

Answer 7

The individual component is known as a connexin, where 6 connexin = 1 connexon. Each of the 6 connexins has 4 membrane-spanning regions. A channel is formed by the pores in each membrane, where there are many connexons present at one gap junction.

Question 8

What is spatial buffering?

Answer 8

Mechanism for the regulation of extracellular potassium concentration by astrocytes. Synaptic activity results in extravasation of K+ -> As K+ conc changes -> Inward current (due to increased ECF K+) induces local depol that will spread throughout the glial cell, and through gap junctions, to neighbouring glia (At other regions K+ is released to the ECF)

Question 9

What other ways do astrocyte maintain ECF ion homeostasis?

Answer 9

• They possess Na+/K+ ATPase, an anion pump and a Na+/K+ symporter to assist spatial buffering
• Neuronal activity also induces considerable changes in ECG pH (increase)
• Astrocytes possess: Na+/H+ exchanger, Na+/HCO3- cotransporter (bidirectional, electrogenic pump which is unique to glial cells in the NS), Cl/HCO3- exchanger, active H+ ion extrusion mechanisms

Question 10

Astrocytes respond to specific inputs via NT receptors

Answer 10

This response includes activation of intracellular Ca2+ via IP3 which is passed on via gap junctions

• Ability to release transmitters via vesicles (e.g. ATP) similar to a neuron
• In response to stimulation, glia release neuractive substances (gliotransmitters)

Question 11

Gliotransmitter release

Answer 11

• Exocytosis via synaptic-like micro vesicles (Glutamate- appear to have VGlut, cluster at release sites associated with exocytotic proteins such as SNAP, SNARE and VAMP)
• Dense core secretory granules are also present (nucleotides (ATP) & peptides)
• Process of exocytosis is slower than in neurons, triggered by IP3 induced changes in intracellular Ca2+

Question 12

Tripartite Synapse

Answer 12

It refers to the functional integration and physical proximity of the presynaptic membrane, postsynaptic membrane, and their intimate association with surrounding glia as well as the combined contributions of these three synaptic components to the production of activity at the chemical synapse