Session 2 Flashcards
(25 cards)
What are the roles of astrocytes?
Structural support
Nutrition for neurones
Remove neurotransmitters
Maintain ionic environment
Describe the glucose-lactate shuttle.
Glucose enters the astrocytes via GLUT1.
This in converted to pyruvate and then to lactate.
Lactate crosses the ECF to the neuron, via MCT1 and MCT2 transporters.
Lactate is then converted to pyruvate and then to ATP within the neuron.
Do astrocytes re-uptake neurotransmitters?
Yes, e.g. Glutamate. This is then converted to glutamine which can then be recycles and sent back to the pre-synaptic terminal.
Why to astrocytes take up potassium ions?
As this would result in depolarisation of neurones in the brain’s ECF, resulting in unwanted action potential firing.
What are the roles of oligodendrocytes?
Myelination of axons in the CNS. Schwann cells myelinate those in the PNS.
Function of microglia?
Immunocompetent cells which recognise foreign material and become activated. Allowing them to phagocytose debris and foreign material, forming the Brain’s main defence system. They are also able to present antigens to T-cells.
What is allowed across the BBB and what is not?
Transporters present for substances such as glucose, amino acids and potassium.
Gaseous molecules and water can diffuse across freely.
Give examples of neurotransmitters which are:
1) Amino acids
2) Biogenic amines
3) Peptides
AAs = glutamate, GABA, glycine
Biogenic amines = ACh, NO, dopamine, serotonin, histamine
Peptides = enkephalins, somatostatin, cholecystokinin, substance P.
What are the 3 types of ionotropic glutamate receptors?
AMPA, Kainate and NMDA.
How do glutamatergic synapses work?
AMPA mediate the initial fast depolarisation, and NMDA receptors are permeable to calcium ions. NMDA receptors need glutamate to bind and the cell to be polarised to allow ion flow through the channel.
How is long term potentiation caused?
Due to strong, high frequency stimulation of glutamate receptors. Calcium entry through NMDA receptors is very important for this.
How does the GABA neurotransmitter work?
GABA receptors have integral Chlorine channels, whereby opening of these channels causes hyperpolarisation and an inhibitory post-synaptic potential. Hence, decreased action potential firing.
Give two classes of drugs that bind to GABA receptors
Barbiturates and benzodiazepines.
Give the role of dopaminergic neurones
Involved in motor control, mood, arousal and rewards. Loss of dopaminergic neurones is associated with Parkinson’s disease. Release of too much dopamine is associated with schizophrenia.
How do you treat Parkinson’s disease?
Give levodopa. This crosses the BBB, and is then converted to dopamine via AADC. In order to prevent conversion in the periphery, give carbidopa.
Where does most noradrenaline come from in the brain?
Group of neurones in the Locus Ceruleus. These neurones are inactive during sleep and activity increases during behavioural arousal.
Role of Serotonin (5-HT)?
Involved in sleep/wakefulness and mood.
What forms the pterion and the anterior cranial fossa?
Pterion = Junction between temporal, parietal, frontal and sphenoid bones.
Anterior cranial fossa = Depression of skull formed by frontal, ethmoid and sphenoid bones.
What forms the middle and posterior cranial fossa?
Middle = Depression formed by sphenoid, temporal and parietal bones.
Posterior = Depression formed by squamous and mastoid temporal bones, plus the
occipital bone.
What is the difference between a linear and a diastatic cranial fracture?
Linear = simple break in bone, traversing its full thickness. Radiating lines away from point of impact. Diastatic = occurs along a suture line, widening the suture.
Describe the two types of hydrocephalus.
1) Communicating = impaired CSF reabsorption in the absence of any CSF flow obstruction between the ventricles ad subarachnoid space.
2) Non-communicating = CSF flow obstruction.
What results following tearing of the middle meningeal artery?
Bleeding into the extradural space (extradural haematoma).
What are the layers of the scalp?
Skin Dense connective tissue Aponeurosis Loose connective tissue Periosteum
What is the name for additional bones that can be found within sutures?
Wormian bones
