Pathophysiology Flashcards
What does pathophysiology mean?
studying the physiology of a pathological organ (in our case: the brain)
How have brain lesion’s contributed to our knowledge of the pathophysiology of the brain?
Brain lesions = a window to the brain. Large amount of knowledge comes from lesion studies
What does a lesion to the frontal lobe cause?
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
What allowed them to study lesions to the frontal lobe?
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
What are the characteristics of an upper motor neuron lesion?
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
What are the characteristics of a lower motor neuron lesion?
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
What are hyporeflexia and hyperreflexia?
Lower motor neuron lesion ==> hyporeflexia: weak flexion of leg
Upper motor neuron lesion ==> hyperreflexia: strong flexion of leg
Why does a lesion to the upper motor neuron causes a lack of control on the reflex circuit?
it has an inhibitory control on the stretch reflex if a lesion occurs there is no more inhibition
What does an injury to the primary motor cortex cause?
a weakness of the contralateral inferior facial muscles (UMN in primary motor cortex is lost)
What does an injury to the corticobulbar tract cause?
weakness of the contralateral inferior facial muscles (UMN in primary motor cortex is lost)
What does an injury to the facial motor nucleus or its nerve cause?
a weakness of all muscles of facial expression on the same side of the lesion (LMN is lost)
What is aphasia?
Disorder in comprehension and/or expression of language
What is Broca’s aphasia?
loss of the ability to produce language
What is Wernicke’s aphasia?
Difficulty understanding speech
Where is a lesion in the Broca’s area located and what can cause these lesions?
in the posterior inferior frontal gyrus (called motor aphasia)
Mostly caused by a stroke
What is multiple sclerosis?
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
What is Myasthenia gravis?
a neuromuscular disease that causes weakness in the muscles (drooping of eyelids, difficulty swallowing, etc…)
How does myasthenia gravis cause muscle weakness?
Ach receptors blocked by antibodies ==> reduced transmission of Ach in muscle ==> impaire muscle contraction
What is the treatment of Myasthenia gravis?
Cholinesterase inhibitors inhibit metabolism of Ach by cholinesterase enzyme which boosts signals between nerves and muscles to improve muscle strength
What is Parkinson’s disease?
Degeneration of the substantia nigra’s neurons (loss of dopaminergic neurons) that causes rigidity, tremor and akinesia
What happens to the pathways when someone has Parkinson’s?
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
What are the treatment options for Parkinson’s disease?
Dopamine-based medication : L-Dopa
Deep brain stimulation
What is Huntington’s disease?
degeneration of caudate and putamen neurons. the size of the caudate and putamen is dramatically reduced which causes hyperkinesia
What happens in the brain to cause Huntington’s disease?
the inhibitory input from the caudate/putamen to the globus pallidus external is diminished
What is Ataxia?
lack of voluntary coordination of muscle movements: dysfunction of the cerebrocerebellum
Loss of balance and gait difficulty: dysfunction of the vestibulocerebellum
genetic disease
