Epilepsy, back pain, depression

Question 1

What are the types of receptor in the somatosensory system?

Answer 1

Mechanoreceptors
Proprioreceptors
Thermoreceptor
Nociceptors

Question 2

What is at the heart of every mechanoreceptor?

Answer 2

An unmyelinated axon branch, with mechanosensitive ion channels; their gating depends on stretching/ changes in the membrane.

Question 3

Give examples of mechanoreceptors?

Answer 3

Meissner’s corpuscles: found in the ridges of glabrous skin between the dermis and epidermis

Pacinian corpuscle: the largest and best studied mechanoreceptor. These are found deep in the dermis.

Ruffini’s endings: these are slightly smaller than Pacinian corpuscles, and are found in both hairy and glabrous skin

Merkel’s disks: these are found in the epidermis, and have a nerve terminal and a flattened, non-neural epithelial cell. The epithelial cell may be the mechanically sensitive part.

Krause end bulbs: these are bulbous endings in the skin, with nerve terminals that look like knotted balls of string.

Question 4

What is an SSRI drug and what is it used for? Give 3 examples.

Answer 4

Selective Serotonin Reuptake Inhibitors - increase the stimulation of 5-HT receptors by preventing the reuptake of the monoamine neurotransmitter serotonin at chemical synapses. SSRIs are used in treating depression.
Examples are Fluoxetine, Sertraline & Citalopram.

Question 5

What is a TCA drug and what is it used for? Give 2 examples.

Answer 5

TCAs are tri-cyclic antidepressants, which act by preventing the reuptake of serotonin and norepinephrine by the serotonin transporter (SERT) and the norepinephrine transporter (NET). They have largely been replaced by newer drugs (SSRIs and SNRIs).

Examples are Amitryptaline and Imipramine.

Question 6

What are SNRIs and what are they used for? Give 2 examples.

Answer 6

SNRIs are serotonin-norepinephrine reuptake inhibitors. They act at chemical synapses, and are less potent inhibitors of dopamine reuptake. SNRIs are used to treat depression.
Examples are Duloxetine and Venlafaxine.

Question 7

What are MAOIs and what are they used for? Give 1 example.

Answer 7

MAOIS are monoamine oxidase inhibitors, which were the first class of antidepressants. They fell out of favur because of concerns about interactions with certain foods, and numerous drug interactions.

They prevent the enzyme monoamine oxidase from breaking down serotonin, norepinephrine and dopamine.

Examples are Phenelzine.
You can’t drink alcohol or eat food that contains tyramine (Cheese, yoghurts, liver) when taking MAOIs.

Question 8

Name the main categories of drugs used for Parkinson’s disease.

Answer 8

1. Dopamine precursor- L-dopa (levodopa)
2. Dopamine agonists- Pramipexole & Ropinirole
3. Monoamine oxidase B inhibitors- Selegiline & Rasagiline
4. Catechol-O-methyltransferase Inhibitors (COMT inhibitors)- Entacapone & Tolcapone
5. Glutamate antagonist- Amantadine
6. Anticholinergics
7. Carbidopa- prevents peripheral metabolism of L-dopa?

Question 9

What symptoms have to be present to diagnose a Total Anterior Circulation stroke? (Oxford Classification)

Answer 9

A total anterior circulation stroke is a large cortical stroke in the middle or anterior cerebral artery. To diagnose. patient must have all 3 of:

1. Contralateral weakness
2. Homonymous hemianopia
3. Higher cortical dysfunction (dysphasia, visuospatial disorder)

Question 10

What symptoms have to be present to diagnose a Posterior Circulation stroke? (Oxford Classification)

Answer 10

Any 1 of:

1. Cerebellar / brainstem syndromes (breathing, HR, BP, pharynx, larynx, speech or swallowing affected)
2. Isolated homonymous hemianopia
3. Cerebellar ataxia/ loss of consciousness

Question 11

What would be the signs and symptoms of an anterior cerebral artery stroke?

Answer 11

Contralateral face, leg, arm weakness, ataxia and absence of willpower.

Question 12

What would be the signs and symptoms of a middle cerebral artery stroke?

Answer 12

The parietal, temporal and posterior frontal lobe would be affected.
Contralateral face, leg and arm weakness. Sensory loss to all modalities. Visuospatial neglect.
If the dominant side is affected:
-aphasia (language)
-agraphia (write)
-alexia (reading)
-acalculia (maths)

Question 13

What would be the signs and symptoms of a posterior cerebral artery stroke?

Answer 13

Occipital lobe affected.

Visual and sensory deficits. The thalamus would be affected; numbness, tingling and chronic pain.

Question 14

What would be the signs and symptoms of an anterior inferior cerebellar artery stroke?

Answer 14

This would result in lateral pontine syndrome.
Contralateral sensory loss: pain and temp.
Ipsilateral limb ataxia, and ipsilateral Horner’s syndrome.

Question 15

What would be the signs and symptoms of a posterior inferior cerebellar artery stroke?

Answer 15

This would affect the lateral medulla (Wallenburg syndrome).
Contralateral sensory loss (pain and temp)
Ipsilateral sensory loss, Horner’s syndrome, pharyngeal and laryngeal paralysis.
Vertigo, nausea, vomitting, hiccups.

Question 16

What would be the signs and symptoms of a basilar arterty/ paramedian perforating vessel stroke?

Answer 16

This would affect the Pons- “locked in syndrome”:
Complete paralysis of nearly all muscles, except vertical eye movements and blinking, gaze palsies.
Quadriplegia
Patient is aware.

Question 17

What would be the signs and symptoms of a vertebral artery stroke?

Answer 17

This would affect the medial or lateral medulla.
Medial medulla- Ipsilateral tongue weakness and atrophy, contralateral weakness, loss of vibration and propriception.
Lateral medulla: Wallenberg syndrome.

Question 18

What is the immediate drug treatment for ischemic stroke?

Answer 18

Thrombolysis- injections of alteplase, which contains recombinant Tissue Plasminogen Activator. This is most effective when given within 4.5 hours, and the patient must have a scan to rule out haemorhagic stroke before giving.
TPA is a serine protease, found in endothelial cells. It catalyses the conversion of plasminogen -> plasmin. Plasmin is an enzyme which breaks down the fibrin mesh of clots.

Question 19

What is the immediate treatment for haemorrhagic stroke?

Answer 19

If the patient is on an anticoagulant, the effects of this need to be reversed. This involves giving Factor VIIa or transfusions of blood clotting factors.
A ventriculostomy tube can be used to measure the pressure within the brain. This is placed through the skull into the ventricles- if pressure is elevated, a small amount of CSF can be removed.

Question 20

Which gene is thought to be involved in the acquisition of language?

Answer 20

FOXP2- appears to affect development of the motor cortex, cerebellum and striatum, and musculature control of the lower face. It is a TF, influencing hundreds of potential language genes.

Question 21

What is the significance of Broca’s area?

Answer 21

It is in the frontal lobe of the dominant hemisphere (usually left), and is linked to speech production, generating articulate speech. It is anatomically lateral to the premotor cortex, and anterior to the primary motor cortex. IT is linked to other brain areas, including Wernicke’s area, by the arcuate fasciculus. It is also involved in language comprehension and motor activities associated with hand movements.

Question 22

What happens in Broca’s aphasia?

Answer 22

Speech produced with great effort, poor articulation, patient pauses to search for the right word. Content words (nouns, verbs, adjectives) are used, but function words such as connectives are left out.
Inability to construct grammatically correct sentences. Comprehension is generally quite good.

Question 23

What is the significance of Wernicke’s area?

Answer 23

In the temporal lobe in the dominant hemisphere, and it encircles the auditory cortex. It is involved in the comprehension of speech and written language.

Question 24

What happens in Wernicke’s aphasia?

Answer 24

Speech is fluent but the content does not make sense. Comprehension is poor. There is use of both content words and function words.

Question 25

What are the two main hypotheses for the cause of schizophrenia?

Answer 25

Dopamine hypothesis- that schizophrenia is due to an excess of dopamine. The typical anty-psychotic Chlorpromazine works by blocking D2 receptors in the mesocorticolimbic system. The doses of antipsychotics needed correlate well with their D2 binding ability.

BUT- an overactive dopamine system cant be the only cause of schizophrenia, as newer antipsychotics such as Clozapine have little effect on D2 receptors.

The glutamate hypothesis- noticed that drugs ketamine and PCP both cause many of the positive and negative symptoms of schizophrenia. These do NOT act on dopamine, they act on glutamate, by inhibiting NMDA receptors. This hypothesis is hence that schizophrenia is due to LOWER activation of NMDA receptors in the brain. Both PCP and ketamine do not prevent the binding of glutamate, instead they block Ca2+ and Na+ from passing through the channel protein by blocking the pore.