session 2: Cellular physiology of the brain

Question 1

what r the Components of the CNS?

Answer 1

Network of neurones with supporting glia

Question 2

what r the types of glial cells (neuroglia) ?

Answer 2

• Astrocytes
• Oligodendrocytes
• Microglia
• Ependymal cells

Question 3

role of astrocytes ? (5)

Answer 3

Question 4

how do neurones get their energy? which glia is responsible for this?

Answer 4

astrocytes can store glucose as glycogen and then break it down into pyruvate–>lactate

lactate moves into interstitial space>>into neurons

in neurons, converted to pyruvate> broken down to form ATP to supply neuron with energy

THIS STORE in ASTROCYTE IS LIMITED!

it will only keep neurons supplied with lacatte for 10-15 mins!

Question 5

how is the neurotransmitter Glutamate removed from neuron terminal? why should it be removed?

Answer 5

glutamate is then broken down into Glutamine then can be transferred back into Glutamate to be taken back into the presynaptic terminal

Question 6

describe the Astrocyte mechanism of taking up K⁺ in the brain? why is this important?

Answer 6

increased K+ causes depolarization and may lead to epilepsy

astrocytes have a very negative resting membrane potential

movement if K+ via

1. channels
2. Na-K-2Cl^- transporter
3. Na-K⁺ atpase

Question 7

role of Oligodendrocytes

Answer 7

Question 8

role of Microglia

Answer 8

• Immunocompetent cells
• Recognise foreign material - activated
• Phagocytosis to remove debris and foreign material

• Brain’s main defence system, acts as APC to t cells

Question 9

why do we have a BBB? explain its strucutre

Answer 9

Limits diffusion of substances from the blood to the brain’s ECF, bc blood does not make a good environment in the brain.

Question 10

what sort of things r transported across the BBB? which GLucose transporter is in the brain?

Answer 10

Question 11

draw the typical neuronal structure

Answer 11

Question 12

explain Neurotransmitter release: The synapse

Answer 12

Question 13

types of Neurotransmitters in the CNS

Answer 13

Question 14

over 70% of the all CNS synapses are _________

Answer 14

glutamatergic

Question 15

what is the major excitatory neurotransmitter? inhibitory aa neurotrasmitter?

Answer 15

– mainly glutamate

– GABA

– Glycine

Question 16

how r Glutamate receptors divided?

Answer 16

• inotropic
• metabotropic

Question 17

what r the main Ionotropic ligand gated recepters?

Answer 17

AMPA>> Na+/K+

NMDA>> receptors Na+/K+ & Ca2+

Question 18

function of Excitatory neurotransmitters ?

Answer 18

cause depolarisation of the postsynaptic cell by acting on ligand-gated ion channels.

• excitatory postsynaptic potential (EPSP)
• depolarisation causes more AP

Question 19

function of AMPA receptors?

Answer 19

• AMPA receptors mediate the initial fast depolarisation

Question 20

function of NMDA receptor, how does it work?

Answer 20

blocked by Mg+

permeable to Ca2+

NMDA receptors need glutamate to bind and the cell to be depolarised to allow ion flow through the channel

– Also glycine acts as a co-agonist

Question 21

role of Glutamate receptors?

Answer 21

important role in learning and memory

Question 22

what is long term potentiation?

Answer 22

is a persistent increase in synaptic strength & high-frequency stimulation of a chemical synapse.

Question 23

what is important for induction of LTP?

Answer 23

Ca²⁺ entry through NMDA receptors

(nadia likes milk)

Question 24

what causes excitotoxicity? give ex.

Answer 24

Too much Ca²⁺ entry through NMDA receptors causes excitotoxicity – Too much glutamate - excitotoxicity

ex: if someone suffered stroke> damaged area releases K+ ions, which will diffuse in the surrouding area> depolarizes cells in the surrounding area> firing increases> Glutamate released wayd> & start killing neurons

Question 25

main inhibitory transmitter in the **brain? brainstem & spinal cord?**

Answer 25

GA**B**A\>\> **B**RAIN Glycine \> brainstem & spinal cord gaba ygoo BAS!

Question 26

how do GABA and glycine receptors work?

Answer 26

* GABA_A and glycine receptors have **integral Cl- channels** * Opening the Cl- channel causes **_hyperpolarisation_** – Inhibitory post-synaptic potential (**IPSP**) • Decreased AP firing

Question 27

which drugs ***_enhance_*** the response to GABA? what r their effects?

Answer 27

– **Barbiturates** - anxiolytic and sedative actions, *but not used for this now* * risk of fatal overdose also dependence and tolerance * **BUT** sometimes used as anti-epileptic drugs – **Benzodiazepines** have sedative and anxiolytic effects used to treat anxiety, insomnia and epilepsy

Question 28

where is glycine released in the knee relfex?

Answer 28

Inhibitory **interneurones** in the spinal cord release glycine

Question 29

function of nucleus basalis?

Answer 29

***aslo known as 'nucleus basalis of meynert"*** is a group of neurons in the substantia innominata of the basal forebrain which has wide projections to the neocortex and is rich in *_Ach and choline acetyltransferase_* *_I_*nvolved in arousal, learning & memory, motor control

Question 30

what disease is associated w/ degeneration of cholinergic neurones in the nucleus basalis? how is this treated?

Answer 30

**Alzheimer’s disease** * (these r the first neurons to die off)* * Cholinesterase inhibitors are used to alleviate symptoms*

Question 31

what r the Dopaminergic pathways in the CNS?

Answer 31

**MNM** make me happy and dope * *Nigrostriatal* \>\> involved in motor control * *Mesocortical/mesolimbic pathway* \>\> involved in mood, arousal and reward

Question 32

which areas in the brain r rich in dopamine

Answer 32

Question 33

Conditions associated with dopamine dysfunction

Answer 33

* Parkinson’s * Schizophrenia

Question 34

antipsychotic drug actions on dopamine?

Answer 34

antipsychotic drugs are antagonists at dopamine D2 receptors

Question 35

Dopamine therapy

Answer 35

**L-dopa** can pass pass through the BBB and be converted to dopamine by AADC. this AADC is also present in the periphery, but u dont want too much dopamine being made in the periphery so we give **carbidopa** which cant cross the BBB

Question 36

increased levels of dopamine in the periphery can cause side effect, what r they, and how do we prevent this?

Answer 36

Gi side effects, we give CARBIDOPA that inhibits AADC

Question 37

what level of the brain is this? arrow?

Answer 37

if u see **mickey mouse**\>\> 3ala 6ool think **MIDBRAIN!** mickey mouse's eyebrows\>\> Substania Nigra