Pathophysiology

Question 1

What does pathophysiology mean?

Answer 1

studying the physiology of a pathological organ (in our case: the brain)

Question 2

How have brain lesion’s contributed to our knowledge of the pathophysiology of the brain?

Answer 2

Brain lesions = a window to the brain. Large amount of knowledge comes from lesion studies

Question 3

What does a lesion to the frontal lobe cause?

Answer 3

Difficulty with executive functions: hard to manage daily plans, decision making, not organized, etc…
Change in personality and behaviour: more aggressive, less compassion, social isolation

Question 4

What allowed them to study lesions to the frontal lobe?

Answer 4

Thanks to Phineas Gage who had a work accident where a bar blew straight through his head and damaged his frontal lobe. He somehow lived

Question 5

What are the characteristics of an upper motor neuron lesion?

Answer 5

Site of lesion: cortex, brainstem, spinal cord
Muscle weakness: yes (plegia)
Muscle tone: increased (spastic)
Muscle atrophy : disuse atrophy
Muscle twitching: no
Tendon reflex: hyperreflexia
Plantar reflex: positive babinski sign

Question 6

What are the characteristics of a lower motor neuron lesion?

Answer 6

Site of lesion: anterior horn, roots, nerves, neuromuscular junction
Muscle weakness: yes (myopathy)
Muscle tone: decreased (hypotonia)
Muscle atrophy : denervation atrophy
Muscle twitching: yes
Tendon reflex: hyporeflexia
Plantar reflex: negative babinski sign

Question 7

What are hyporeflexia and hyperreflexia?

Answer 7

Lower motor neuron lesion ==> hyporeflexia: weak flexion of leg
Upper motor neuron lesion ==> hyperreflexia: strong flexion of leg

Question 8

Why does a lesion to the upper motor neuron causes a lack of control on the reflex circuit?

Answer 8

it has an inhibitory control on the stretch reflex if a lesion occurs there is no more inhibition

Question 9

What does an injury to the primary motor cortex cause?

Answer 9

a weakness of the contralateral inferior facial muscles (UMN in primary motor cortex is lost)

Question 10

What does an injury to the corticobulbar tract cause?

Answer 10

weakness of the contralateral inferior facial muscles (UMN in primary motor cortex is lost)

Question 11

What does an injury to the facial motor nucleus or its nerve cause?

Answer 11

a weakness of all muscles of facial expression on the same side of the lesion (LMN is lost)

Question 12

What is aphasia?

Answer 12

Disorder in comprehension and/or expression of language

Question 13

What is Broca’s aphasia?

Answer 13

loss of the ability to produce language

Question 14

What is Wernicke’s aphasia?

Answer 14

Difficulty understanding speech

Question 15

Where is a lesion in the Broca’s area located and what can cause these lesions?

Answer 15

in the posterior inferior frontal gyrus (called motor aphasia)
Mostly caused by a stroke

Question 16

What is multiple sclerosis?

Answer 16

an immune-mediated inflammatory disease that causes the demyelination of the nerves of central nervous system resulting in:
muscle weakness
Loss of sensation
visual disturbances

Question 17

What is Myasthenia gravis?

Answer 17

a neuromuscular disease that causes weakness in the muscles (drooping of eyelids, difficulty swallowing, etc…)

Question 18

How does myasthenia gravis cause muscle weakness?

Answer 18

Ach receptors blocked by antibodies ==> reduced transmission of Ach in muscle ==> impaire muscle contraction

Question 19

What is the treatment of Myasthenia gravis?

Answer 19

Cholinesterase inhibitors inhibit metabolism of Ach by cholinesterase enzyme which boosts signals between nerves and muscles to improve muscle strength

Question 20

What is Parkinson’s disease?

Answer 20

Degeneration of the substantia nigra’s neurons (loss of dopaminergic neurons) that causes rigidity, tremor and akinesia

Question 21

What happens to the pathways when someone has Parkinson’s?

Answer 21

the dopaminergic inputs provided by substantia nigra pars compacta to the caudate and putamen that are diminished
Direct pathway: transient inhibition from caudate/putamen to globus pallidus internal is diminished
Indirect pathway: transient inhibition from caudate/putamen to the globus pallidus external is increased

Question 22

What are the treatment options for Parkinson’s disease?

Answer 22

Dopamine-based medication : L-Dopa
Deep brain stimulation

Question 23

What is Huntington’s disease?

Answer 23

degeneration of caudate and putamen neurons. the size of the caudate and putamen is dramatically reduced which causes hyperkinesia

Question 24

What happens in the brain to cause Huntington’s disease?

Answer 24

the inhibitory input from the caudate/putamen to the globus pallidus external is diminished

Question 25

What is Ataxia?

Answer 25

lack of voluntary coordination of muscle movements: dysfunction of the cerebrocerebellum
Loss of balance and gait difficulty: dysfunction of the vestibulocerebellum
genetic disease