PBL 6

Question 1

What are the 4 main neuronal types and where are they most likely to be found?

Answer 1

Anaxonic - special sense organs
Bipolar - special sense organs (eye, nose, ear)
Unipolar - sensory neurons
Multipolar - motor neurons

Question 2

What are the types of neuroglia present in the CNS and what are their functions?

Answer 2

Ependymal cells - secrete CSF
Astrocytes - provide structural framework
Oligodendrocytes - wrap neurons in myelin
Microglia - phagocytic immune cells

Question 3

What are the types of neuroglia present in the PNS and what are their functions?

Answer 3

Satellite cells - provide structural framework and regulate environment

Schwann cells - wrap myelin around single axon

Question 4

What is the difference between an absolute refractory period and a relative refractory period?

Answer 4

Absolute refractory period - where no stimulus can excite the nerve
Relative refractory period - where a stronger than normal stimulus can excite the nerve

Question 5

What is the difference between a graded potential and an action potential?

Answer 5

Graded potential - weak and don’t reach threshold

Action potential - reach threshold and depolarise cell

Question 6

What is saltatory conduction?

Answer 6

Where due to the presence of myelin on axons, the action potential “jumps” from one node of ranveir to the next, skipping the myelinated internodes

Question 7

What is the difference between an ionotropic and a metabotropic receptor?

Answer 7

Ionotropic - forms ion channels

Metabotropic - G protein coupled receptor

Question 8

What are the different types of glutamate receptor and what does binding of glutamate result in?

Answer 8

AMPA: binding allows sodium ion entry into cell

NMDA: binding allows dissociation of mg so sodium and calcium to enter cell

Question 9

In relation to synaptic integration, what is the difference between spacial summation and temporal summation?

Answer 9

Spacial summation - addition of EPSPs generated simultaneously by multiple synaptic inputs

Temporal summation - addition of EPSPs generated in quick succession at the same synapse

Question 10

What is the difference between tonic and phasic firing of a neuron?

Answer 10

Tonic - where firing is constantly occurring (background noise)
Phasic - where you get a burst of action potentials due to a stimulus

Question 11

What is the ratio of MS in women to men?

Answer 11

3:1
Women:men

Question 12

What genetic factors have been linked to MS?

Answer 12

Human leukocyte antigen (HLA) - genes associated with self recognition

Question 13

What are the different types of MS?

Answer 13

Relapsing-remitting
Primary progressive
Secondary progressive
Progressive-relapsing

Question 14

Which self proteins do immune cells attack in MS?

Answer 14

Myelin proteins:

• myelin basic protein (MBP)
• myelin oligodendrocyte glycoprotein (MOG)
• myelin associated glycoprotein (MAG)

Question 15

What are the clinical manifestations of the relapsing and remitting stages in MS

Answer 15

Relapsing - where demyelination occurs

Remitting - where remyelination occurs

Question 16

What are lesions/plaques in MS?

Answer 16

Scars that form due to repeated attacks on oligodendrocytes, so that they are unable to completely rebuild the myelin

Question 17

What is the difference between an active and inactive plaque in MS?

What type of MS are they commonly seen?

Answer 17

Active: characterised by a slowly expanding rim of activated immune cells. Microglia contain myelin degradation products around inactive centre
- seen in relapsing-remitting
Inactive: little to no myelin present, and reduced number of oligodendrocytes
- seen in progressive MS

Question 18

What are the main symptoms of MS?

Answer 18

Optic neuritis - leads to blurring of vision or colour vision loss
Nystagmus 
Dysarthria (slurred speech)
Dysphasia (difficultly swallowing)
Upper and/or lower limb weakness
Bladder, bowels and sexual dysfunction

Question 19

What is Uhtoff’s phenomenon?

What condition is it commonly seen in?

Answer 19

Worsening of vision occurring during a fever, hot weather or exercise. Due to irritation of scar in optic neuritis

Multiple sclerosis

Question 20

What is Lhermitte’s phenomenon?

What condition is it commonly seen in?

Answer 20

Pain/shock that extends down the spine when bending over

Multiple sclerosis

Question 21

What is Gillian Burre Syndrome?

Answer 21

A lower motor neuron demyelinating disease

Question 22

What is clonus ?

Answer 22

Shaking of the foot when you dorsiflex the ankle rapidly

Question 23

What are the diagnostic tests used to confirm MS?

Answer 23

MRI - looking for lesions or brain shrinkage
CSF (lumbar puncture) - looking for presence of antibodies in the CSF but not in the serum
Evoked potentials (EP) test - delayed transmission of optic nerve

Question 24

What drugs are given to help manage MS?

Answer 24

Corticosteroids

Disease modifying agents - keep the immune system from attacking myelin

Question 25

What is anhedonia?

Answer 25

Lack of pleasure in doing things

Question 26

How is depression diagnosed?

Answer 26

Using a pHQ-9 questionnaire - 5 or more depressive symptoms in 2 week period - 1 of which must be depressed mood or anhedonia (lack of pleasure in doing things)

Question 27

What are the two types of monoamines? Give examples. Which amino acid are they produced from?

Answer 27

``` Catecholamines - produced from tyrosine - dopamine - noradrenaline Indolamines - produced from tryptophan - serotonin ```

Question 28

What enzymes are responsible for noradrenaline degradation?

Answer 28

``` Monoamine oxidase (MAO-A) Catechol-O-methyl transferase (COMT) ```

Question 29

What are the different noradrenergic receptors? Are they stimulatory or inhibitory?

Answer 29

``` Alpha 1 (stimulatory) Alpha 2 (inhibitory) Beta (stimulatory) ```

Question 30

What kind of receptor are most of 5-HT receptors? Which is the exception?

Answer 30

G Protein coupled receptors 5-HT3: this is a cation receptor

Question 31

Which serotonin receptors are inhibitory and which are stimulatory?

Answer 31

Inhibitory: 5HT1 and 5HT5 Stimulatory: 5HT2, 5HT3, 5HT4, 5HT6, 5HT7

Question 32

How does noradrenaline control serotonin release?

Answer 32

Binds to a1 receptors on 5HT neuron cell body - increases serotonin release Binds to a2 receptors on 5HT terminal - inhibits serotonin release

Question 33

What is a major side effect with MAO-Is

Answer 33

Hypertensive crisis - MAOs are needed to metabolise dietary tyramine (round in red wine, cheese, marmite). By blocking them you get a build up of tyramine resulting in hypertension

Question 34

What is the kindling hypothesis?

Answer 34

Where depressive episodes become more easily triggered over time (the threshold is lowered)

Question 35

What are the two main systems in the brain responsible for regulating mood? What are the main structures within them?

Answer 35

``` Ventral neural system: - ventral anterior cingulate - amygdala Dorsal neural system - dorsal anterior cingulate - hippocampus ```

Question 36

What is electroconvulsive therapy? What are its disadvantages?

Answer 36

Electrical stimulation of the temporal lobes resulting in seizure discharges, helps to treat depression. Memory loss due to hippocampus presence in temporal lobe