Neuroplasticity pt2 March 20 2013 Causes of Brain Damage Brain Tumors Cerebrovascular Disorders Strokes Cerebral Hemorrhage amp Ischemia ClosedHead Injuries Infections Bacterial amp Viral ID: 529137
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Slide1
Ch 10 Brain Damage & Neuroplasticity (pt2)
March 20, 2013Slide2
Causes of Brain Damage
Brain Tumors
Cerebrovascular
Disorders (Strokes)
Cerebral Hemorrhage & Ischemia
Closed-Head Injuries
Infections
Bacterial & Viral
Neurotoxins
Genetic Factors
Programmed Cell DeathSlide3
Genetic Factors
Normal human cells have 23 pairs of chromosomes
An extra chromosome 21 results in
Down syndrome
Occurs in 0.15% of births
Likelihood increases with maternal age
Flattened skull & nose, inner eye folds of skin, short fingers, intellectual impairment & medical complicationsSlide4
Programmed Cell Death
Apoptosis
: genetic self-destruct program for neurons (cell suicide)
Functions in early development by eliminating extra, unnecessary neurons
Also involved in brain damage
Passive cell death
(
necrosis
) occurs only when neurons are damaged severely
The majority is due to apoptosis
Neurons slowly shrivel, die & break down without inflammation or causing damage to nearby cellsSlide5
Neuropsychological Diseases
Epilepsy
Parkinson’s Disease
Huntington’s Disease
Multiple Sclerosis
Alzheimer’s DiseaseSlide6
Epilepsy
Main symptom is repeated
seizures
, caused by chronic brain dysfunction
Different types of seizures
Convulsions
Motor seizures; involve tremors (
clonus
), rigidity (tonus) & loss of balance and consciousness
Others happen with seemingly no change in behavior
All of the previously discussed causes of brain damage can cause epilepsy
Often associated with problems at inhibitory synapsesSlide7
Epilepsy
Diagnosed with scalp electroencephalography (EEG)
People often experience a weird psychological change before a convulsion (epileptic aura)
Ex: bad smell, déjà vu, hallucination
Can give a hint of brain area causing seizuresSlide8
Epilepsy
2 types
Partial
Partial seizure
does not involve the whole brain
Caused by synchronous burst of neuron firing
Generalized
Entire brain is involved
Grand mal
(“classic” seizure)
Petit mal
(no convulsions)Slide9
Parkinson’s Disease
Symptoms of a resting tremor, muscular rigidity, difficulty initiating movement, slow movement, masklike face
Associated with degeneration of the
substantia
nigra
in the midbrain
Primarily of
dopaminergic neurons
So symptoms can be alleviated by
L-
Dopa
injections (but not permanently)
Other treatments include
dopamine agonistsSlide10
Huntington’s Disease
Another progressive motor disorder
Late stages involve severe cognitive decline
Onset around age 40
No cure & usually death within 15 years
Rare
Has a strong genetic basis
If a parent has it, 50/50 chance child will have itSlide11
Multiple Sclerosis
MS is a progressive disease that attacks the myelin of axons in the CNS
Eventually causes dysfunction in the axons & scar tissue develops (
sclerosis
)
An autoimmune disorder
Symptoms include visual disturbances, muscular weakness, numbness, tremor & ataxia (loss of motor coordination)
Genetic & environmental influencesSlide12
Alzheimer’s Disease
The most common cause of dementia
Likelihood of having it increases with age
10% of age 65+; 35% of age 85+
Progressive disease
Early stage: memory decline, attention problems & personality changes
Mid stage: confusion, irritability, anxiety, problems with speech, swallowing & bladder control
Ultimately terminal
Can only be certain of diagnosis during autopsy
Presence of
neurofibrillary
tangles
&
amyloid
plaquesSlide13
Neuroplastic Responses
N
europlastic
responses to brain damage
Degeneration
Regeneration
Reorganization
Recovery of functionSlide14
Neural Degeneration
aka neural deterioration
2 types
Anterograde
degeneration
Degeneration of
distal segment
(Section of axon between the cut & the synaptic terminal)
Segment no longer gets energy from the cell body
Retrograde degeneration
Degeneration of
proximal segment
(Section of axon between the cut & the
soma)
If the axon cannot reestablish contact with a target, the neuron eventually diesSlide15
Neural Regeneration
Regrowth
of damaged neurons
Not as successful in mammals as in lower vertebrates & inverts
Almost
nonexistant
in CNS of adult mammals
Regrowth
from proximal stump 2-3 days after axonal damage
Does not necessarily mean that function will be returnedSlide16
Neural Reorganization
The brain can effectively reorganize itself in response to damage
Other areas can compensate for the damaged area’s function
Ex: blind individuals have little use for visual
cotex
, so the auditory &
somatosensory
cortex expands into this region, giving them heightened sensitivity to hearing & touch
Works by strengthening existing connections & making new onesSlide17
Neuroplasticity & the Treatment of Nervous System Damage
May be possible to reduce brain damage by blocking neural degeneration
Apoptosis inhibitor proteins
Nerve growth factor
Estrogren
Potentially explains why several brain disorders are less common in women
Molecules that limit degeneration also promote regenerationSlide18
Neuroplasticity & the Treatment of Nervous System Damage
Regeneration in mammalian CNS doesn’t normally happen, but in the lab it can be induced
Potential treatment with transplantation of fetal tissue into the brain or injection of embryonic stem cells
Rehabilitation training can help by encouraging brain reorganization
Ex: treadmill for spinal cord injuries
Physically & mentally active individuals are less likely to contract neurological disorders & if they do, their symptoms are more mild & they have
fuller recovery