Cellular Physiology Of The Brain Flashcards
What are the three types of glial cells?
Astrocytes,
Oligodendrocytes,
Microglia.
What is the role of astrocytes?
Provide nutrition to neurones via the glucose-lactate shuttle,
Remove neurotransmitters,
Buffer changes in K+.
What property of astrocytes allows them to take up large amounts of potassium ions?
Very negative resting embrace potential.
What is the role of oligodendrocytes?
Myelination of axons in the CNS. Able to myelinated multiple neurones.
What is the role of microglial cells?
Phagocytosis of foreign material,
Antigen presentation.
What structures help create the blood brain barrier?
Tight junctions between endothelial cells,
Basement membranes surrounding the capillary,
End feet of astrocytes processes.
How is the CNS “immune privileged”?
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.
What three types of neurotransmitter are seen in the CNS?
Amino acids - glutamate, GABA, glycine.
Biogenic Amines - acetylcholine, noradrenaline, dopamine, serotonin, histamine.
Peptides - somatostatin, cholecystokinin, dynorphin.
What is the major excitatory neurotransmitter?
Glutamate. It is also toxic in larger concentrations.
What types of glutamate receptors are there in the CNS?
Ionotropic - ion channels that are activated to cause depolarisation and increased activity.
Metabotropic - G protein coupled receptors Gaq or Gi
which receptors are present on glutamatergic synapses?
AMPA and NDMA receptors.
What is special about NMDA receptors?
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.
What is the major physiological role of glutamate receptors?
Formation of memories and learning.
NMDA receptors up-regulate AMPA receptors causing strengthening of the neurone.
What is the main inhibitory neurone in the CNS?
Where does glycine act?
GABA.
Brainstem and spinal cord.
How do inhibitory receptors act?
Opening of integral Cl- channels to cause hyperpolarisation and a reduced frequency of action potentials.
Which drugs bind to GABA receptors to bring about their effect (by enhancing the response to GABA).
Barbiturates and benzodiazepines. Both have sedative effects and are used to treat epilepsy.
Which receptors does acetylcholine act upon in the CNS?
Both nicotinic and muscarinic receptors with excitatory effect. Also enhances the release of other neurotransmitters.
Which pathways is acetylcholine involved in?
What disease is symptomatically treated by cholinesterase inhibitors?
Memory, arousal, learning, motor control.
Alzheimer’s disease.
What are the different dopaminergic pathways in the CNS?
Nigrostriatal - motor control.
Mesocortical and Mesolimbic pathways - mood, arousal and reward.
What disease is commonly associated with the loss of dopaminergic neurones?
How can it be treated?
Parkinson’s disease.
Treated with levadopa - converted to dopamine by DOPA decarboxylase.
What disease likely results due to a release of too much dopamine?
How is it treated?
Schizophrenia.
Antipsychotic antagonists at dopamine D2 receptors.
How does the administration of Carbidopa ensure that levadopa only acts on pathways within the brain?
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.
Which area of the brain does most noradrenaline come from?
Locus coeruleus. Active during behavioural arousal and inactive during sleep.
Which neurotransmitters have associations with depression?
Noradrenaline and serotonin. These also have very similar, diffuse release throughout the brain
