Cellular Physiology Of The Brain

Question 1

What are the three types of glial cells?

Answer 1

Astrocytes,
Oligodendrocytes,
Microglia.

Question 2

What is the role of astrocytes?

Answer 2

Provide nutrition to neurones via the glucose-lactate shuttle,
Remove neurotransmitters,
Buffer changes in K+.

Question 3

What property of astrocytes allows them to take up large amounts of potassium ions?

Answer 3

Very negative resting embrace potential.

Question 4

What is the role of oligodendrocytes?

Answer 4

Myelination of axons in the CNS. Able to myelinated multiple neurones.

Question 5

What is the role of microglial cells?

Answer 5

Phagocytosis of foreign material,

Antigen presentation.

Question 6

What structures help create the blood brain barrier?

Answer 6

Tight junctions between endothelial cells,
Basement membranes surrounding the capillary,
End feet of astrocytes processes.

Question 7

How is the CNS “immune privileged”?

Answer 7

Inflammatory T cell responses are inhibited in the brain, however T cells can still enter the CNS. This avoids volume expansion and damage to the brain.

Question 8

What three types of neurotransmitter are seen in the CNS?

Answer 8

Amino acids - glutamate, GABA, glycine.
Biogenic Amines - acetylcholine, noradrenaline, dopamine, serotonin, histamine.
Peptides - somatostatin, cholecystokinin, dynorphin.

Question 9

What is the major excitatory neurotransmitter?

Answer 9

Glutamate. It is also toxic in larger concentrations.

Question 10

What types of glutamate receptors are there in the CNS?

Answer 10

Ionotropic - ion channels that are activated to cause depolarisation and increased activity.

Metabotropic - G protein coupled receptors Gaq or Gi

Question 11

which receptors are present on glutamatergic synapses?

Answer 11

AMPA and NDMA receptors.

Question 12

What is special about NMDA receptors?

Answer 12

Permeable to calcium ions. Require glutamate to bind and depolarise the cell to allow ions to flow through their channels as they are blocked by magnesium ions before this.

Question 13

What is the major physiological role of glutamate receptors?

Answer 13

Formation of memories and learning.

NMDA receptors up-regulate AMPA receptors causing strengthening of the neurone.

Question 14

What is the main inhibitory neurone in the CNS?

Where does glycine act?

Answer 14

GABA.

Brainstem and spinal cord.

Question 15

How do inhibitory receptors act?

Answer 15

Opening of integral Cl- channels to cause hyperpolarisation and a reduced frequency of action potentials.

Question 16

Which drugs bind to GABA receptors to bring about their effect (by enhancing the response to GABA).

Answer 16

Barbiturates and benzodiazepines. Both have sedative effects and are used to treat epilepsy.

Question 17

Which receptors does acetylcholine act upon in the CNS?

Answer 17

Both nicotinic and muscarinic receptors with excitatory effect. Also enhances the release of other neurotransmitters.

Question 18

Which pathways is acetylcholine involved in?

What disease is symptomatically treated by cholinesterase inhibitors?

Answer 18

Memory, arousal, learning, motor control.

Alzheimer’s disease.

Question 19

What are the different dopaminergic pathways in the CNS?

Answer 19

Nigrostriatal - motor control.

Mesocortical and Mesolimbic pathways - mood, arousal and reward.

Question 20

What disease is commonly associated with the loss of dopaminergic neurones?
How can it be treated?

Answer 20

Parkinson’s disease.

Treated with levadopa - converted to dopamine by DOPA decarboxylase.

Question 21

What disease likely results due to a release of too much dopamine?
How is it treated?

Answer 21

Schizophrenia.

Antipsychotic antagonists at dopamine D2 receptors.

Question 22

How does the administration of Carbidopa ensure that levadopa only acts on pathways within the brain?

Answer 22

Carbidopa inhibits aromatic amino acid decarboxylase which catalyses the reaction converting levadopa into dopamine. As Carbidopa cannot cross the blood brain barrier, any levadopa that crosses the blood brain barrier can be freely converted and have therapeutic effect.

Question 23

Which area of the brain does most noradrenaline come from?

Answer 23

Locus coeruleus. Active during behavioural arousal and inactive during sleep.

Question 24

Which neurotransmitters have associations with depression?

Answer 24

Noradrenaline and serotonin. These also have very similar, diffuse release throughout the brain