L6 - Disorders of Neural Transmission

Question 1

Define seizure?

Answer 1

Temporary disruption of brain function due to excessive discharge of cortical neurons.

Question 2

What is Epilepsy?

Answer 2

Brain disorder characterized by a enduring predisposition to generate epileptic seizures.

Question 3

State some different types of primary generalised seizures?

Answer 3

Absent seizures, tonic seizures, atonic seizures, clonic seizures, myoclonic seizures, tonic-clonic seizures

Question 4

Absence seizures

Answer 4

Often occur in kids.
Characterised by staring into space or by subtle body movements
- eye blinking
- lip smacking

Question 5

Tonic seizures

Answer 5

• Cause stiffening of muscles,
• Affect muscles in back, arms and legs.
• May cause you to fall to the ground.

Question 6

Atonic seizures

Answer 6

Drop seizures, loss of muscle control

Question 7

Clonic seizures

Answer 7

Repeated or rhythmic jerking muscle movements.

- neck, face and arms usually affected

Question 8

Myoclonic seizures

Answer 8

Sudden brief jerks or twitches of arms and legs

Question 9

Tonic-clonic seizures

Answer 9

Can cause abrupt loss of consciousness, body stiffening, shaking, loss of bladder control, biting tongue

Question 10

Briefly describe the pathophysiology of seizures?

Answer 10

Excessive excitation or loss of inhibition of neurons.

Key unit of neurotransmission is the synpase.
- seizures involve malfunction of ion channels.

Question 11

Main causes of epilepsy include:

Answer 11

Low oxygen during birth.
Head injuries. 
Brain tumours.
Infections e.g. meningitis or encephalitis
Stroke 
Abnormal levels of sodium or BG

Question 12

What are focal seizures?

Answer 12

• Abnormal discharge appears to start in one part of the brain
• may become generalised.
• With or without loss of awareness.

Question 13

Describe structural causes of epilepsy?

Answer 13

Epilepsy may occur if brain cells are damaged. 
Some causes are:
- damage to brain during development 
- bleeding in brain 
- infection in brain 
- head injury 
- stroke

Question 14

Describe some genetic causes of epilepsy?

Answer 14

Certain types of epilepsy are known to have a genetic cause:

• Benign rolandic epilepsy
• Temporal lobe epilepsy
• Juvenile myoclonic epilepsy

Question 15

Benign Rolandic Epilepsy

Answer 15

Common form of childhood epilepsy

- reffered to as benign as most children grow out of it

Question 16

Give examples of autoimmune diseases which cause epilepsy?

Answer 16

• Systemic lupus ertyhematosus (immune system mistakenly attacks healthy tissue)
• stiff man syndrome (progressive rigidity and stiffness)
• Hashimoto’s encephalopathy (associated with hashimoto’s thyroiditis) (HT common cause of hypothyroidism, affects brain and contributes to seizures, confusion or dementia)

Question 17

Describe how faulty ion channels contribute to epilepsy?

Answer 17

Genetic mutations, dysfunction in voltage and ligand gated ion channels.

• defective Na+ channels of inhibitory neurons
• defective GABAa receptors affecting pre/post synaptic GABAergic inhibition

Question 18

Describe briefly how anti-epileptic drugs work?

Answer 18

Targets of AEDs

• Sodium ion channels
• Calcium ion channels
• the GABA system and receptor agonists
• Glutamate receptors antagonist

Question 19

Describe examples of AEDs which target Sodium channels?

Answer 19

Phenytoin, Lamotrigine and carbamazepine

• AED binds/ attaches to Na+ channel
• Sodium channels responsbile for depolarisation of nerve cell membrane and conduction of AP.

Hence prevents signals from being passed on.

Question 20

Describe the role of voltage gated calcium channels in neurones?

Answer 20

Control neurotransmitter release at pre-synaptic nerve terminal.

Question 21

What is an important role of dopamine?

Answer 21

Neurons of the substantia nigra communicate with neurons of the basal ganglia by liberating the neurotransmitter dopamine.
- important for the fine tuning of an organisms movements.

Question 22

What is Parkinson’s disease?

Answer 22

Neurological disorder that affects movement control.

• substantia nigra neurones progressively degenerate.
• amount of dopamine available for neurotransmission in the corpus striatum is lowered.
• biochemical imbalance results in symptoms like - resting tremor, bradykinesia, rigidity. loss of postural reflexes etc.

Question 23

Where is dopamine produced?

Answer 23

Substantia nigra. ventral tegmental regions of brain, dopamine alterations are related to schizophreia.

Question 24

Dopaminergic projections are divided into…

Answer 24

Nigrostriatal

• substantia nigra
• control of voluntary movement

Mesolimbic

• ventral tegmental area
• interactive and reactive behaviours

Mesocortical systems.

Question 25

Excess dopamine may result in?

Answer 25

Schizophrenia

Symptoms: hallucinations and delusions as a result of increased subcortical release of dopamine.

Question 26

Describe Lambert Eaton syndrome?

Answer 26

Condition where immune system attacks neuromuscular junctions.

Question 27

Describe the mechanism of Lambert Eaton syndrome?

Answer 27

• antibodies against pre-synaptic calcium channels of the neuromuscular junction.
• decreased ACH release with neuronal transmission

Question 28

What is Botulism?

Answer 28

Caused by clostridium botulinum.

Paralysis, starting in face to limbs. If it reaches breathing muscles, resp can fail.