S2 NEURONES AND GLIA

Question 1

What do neurones in the CNS do ?

Answer 1

Sense changes and communicate with other neurones

Question 2

What do glia do in the CNS ?

Answer 2

Glia support, nourish and insulate neurones an remove waste

Question 3

What are types of glia ?

Answer 3

Astrocytes
Oligodendrocytes
Microglia

Question 4

What are the functions of Astrocytes ?

Answer 4

Provide nutrition for neurones
Structural support
Most abundant
Remove neurotransmitters
Maintain ionic environment
Forms BBB - have tight junctions between endothelial cells

Question 5

What are functions of oligodendrocytes ?

Answer 5

Insulators - myelinate axons in CNS ( in PNS Schwann cells myelinate)
Multiple sclerosis causes damage of this

Question 6

What are the functions of Microglia ?

Answer 6

Immune response - immunocompetent cells which are activated when they recognise foreign material and can acts as APCs
Phagocytosis to remove foreign material

Question 7

How do neurones communicate with the synapse ?

Answer 7

Fast excitatory neurotransmission
Fast inhibitory neurotransmission
Modulatory responses

Question 8

Describe a neurone structure

Answer 8

Cell soma, dendrites, axon, terminals

Question 9

How are NT released ?

Answer 9

AP reaches terminal and causes depolarisation which opens voltage gated ion channels and Ca 2+ ions enter the terminal
Vesicles fuse and release transmitter
NT diffuses across the synaptic cleft and binds to receptors on the postsynaptic membrane - response depends on the nature of tramsiiter or receptor (GCPS)

Question 10

What are the NTs in the CNS ?

Answer 10

AA - excitatory - glutamate
Inhibitory - glycine or GABA
Biogenic amines (ACH)
Peptides ( somatostatin)

Question 11

What are the types of glutamate receptors ?

Answer 11

Ionotropic - LG ion channels - permeable to Na/K e.g AMPA, NMDA
Metabotrophic - GPCR which control Ca or adenylyl cyclase/cAMP

Question 12

Describe the fast excitatory response

Answer 12

Excitatory NT causes depol of the post-synaptic cell by acting on ligand - gated ion channels causing excitatory post synaptic potential and more action potentials

Question 13

Describe the nature of glutamatergic synapses

Answer 13

AMPA and NMDA receptors
AMPA mediate initial fast depol
NMDA receptors are permeable to Ca 2+
NMDA receptors need glutamate binding and cell depolarisation to allow ion flow through the channel

Question 14

How does NMDA receptors influence AMPA receptors ?

Answer 14

Activation of NMDA receptors can up-regulate AMPA receptors
Strong high frequency stimulation causes long term potentiation
Ca 2+ entry through NMDA receptors important for induction of LTP

Question 15

How does too much Ca 2+ receptors cause excitotoxicity ?

Answer 15

Too much Ca 2+ entry through NMDA receptors causes excitotoxicity so need to remove the glutamate

Question 16

What is the inhibitory NT in the brain ?

Answer 16

GABA

Question 17

What is the inhibitory in the brainstem and SC?

Answer 17

Glycine

Question 18

What binds to GABAa receptors ?

Answer 18

Barbiturates - have sedative actions

Benzodiazepines - to treat anxiety

Question 19

How does fast inhibitory neurotransmission work ?

Answer 19

GABAa and glycine receptors have integral CL- channels, opening the CL- Chanel causes hyperpolarisation and an inhibitory post-synaptic potential so decreased AP firing. GABAa GCPRS have a modulatory role

Question 20

How does the knee jerk reflex work ?

Answer 20

Glutamate is released to motor neurones to contract quads

Glycine is released by inhibitory interneurones in SC to relax hams

Question 21

What are examples of biogenic amines ?

Answer 21

ACH, dopamine , NA, serotonin

ACH is mainly excitatory, receptors often present on presynpatic terminals to enhance the release of other transmitters

Question 22

Describe cholinergic pathways in the CNS

Answer 22

Originate in basal forebrain and brainstem
Give diffuse projections to many parts of the cortex and hippocampus.
Involved in learning, memory , motor control

Question 23

How is Alzheimer’s disease related to the cholinergic pathway ?

Answer 23

Degeneration of cholinergic neurones in the nucleus basalis is associated with Alzheimer’s disease (treated with cholinesterase inhibitors)

Question 24

Describe dopaminergic pathways in the CNS

Answer 24

Involved in motor control(nigrostriatal pathway), mood and reward

Question 25

Examples of dopamine dysfunction

Answer 25

Parkinson’s - loss of dopaminergic neurones, treat with levodopa (increases dopa)
Schizophrenia - too much dopamine release, treat with antipsychotic drugs (dope receptor antagonists)

Question 26

Describe dopamine therapy and BBB

Answer 26

Carbidopa prevents L- DOPA - dopamine formation in the periphery by inhibiting AADC - amino acid decarboxylase - L - DOPA can the cross the BB and form dopamine in the brain

Question 27

Describe Noradernaline pathways in the CNS

Answer 27

Cell bodies of NA contain neurones located in the pons and medulla. There is diffuse release of NA throughout cortex, hypothalamus and Cerebellum
Most NA in the brain comes from neurones in the locus coeruleus, these inactivate during sleep. And increase in behavioural arousal

Question 28

Describe serotonergic pathways in the CNS

Answer 28

Involved in sleep and mood. SSRIs are used to treat depression and anxiety