CNS Flashcards
Gray matter
Contains the cell bodies of neurons (and some fibers)
Cortex and deep grey matter
White matter
Contains myelinated axons
Below the cortex and running along tracts in the brain
Corpus callosum
Connects two hemispheres
Diencephalon (3)
Structures deep in cerebral hemisphere
- Hypothalamus
- Thalamus
- Basal ganglia
Basal ganglia
Has three structures
Involved in motor control - skeletal muscle contraction
Brainstem (3)
- Midbrain
- Pons
- Medulla
Cerebrum
4 lobes (frontal, parietal, temporal, occipital)
Frontal lobe
Controls movement, behaviour, emotions, higher intellectual functions
Parietal lobe
Integrates sensory inputs like touch and controls language
Temporal lobe
Hearing, smelling, memory and expression
Hippocampus
In control of memory
Occipital lobe
Controls vision
Thalamus
Integrates sensory stimuli like pain and touch
Controls consciousness
Hypothalamus
Connects many different parts of the brain and regulates many body functions (appetite, thirst, temperature)
Midbrain
Visual, auditory reflex centers
Medulla oblongata
Cardiac, vasomotor, respiratory centers
Pons
Bundles of axons carrying information to and from the brain
Cerebellum
Little brain
Coordinates voluntary movement
Controls the ability to stand upright without falling over
Controls muscle tone
Inputs include sensory information carried by spinal cord, vestibular organ and motor impulses form cerebral cortex
White matter of the spinal cord
Dorsal, lateral and ventral columns
Descending motor tracts
Corticospinal tracts in lateral and anterior columns
Downward extension of upper motor neurons in the brain
Contact lower motor neurons in anterior horn which stimulate contraction of skeletal muscle
Ascending sensory tracts
Carry sensory information through posterior columns
Contain axons coming from neurons in the spinal ganglia which receive sensory information from the body
Meninges (3)
Membranous cover bathing the brain \+BBB prevent ionization in the brain 1. Dura 2. Arachnoidea 3. Pia
Dura
Outermost meninges
Very thick
Arachnoidea
Middle layer of meninges
Subarachnoid space
Contains CSF
Bathes the brain
Pia
Innermost layer of meninges
Very molded to sulci
Neuron
Perikaryon (body, dendrites, axon Postmitotic cells that do not divide or multiply Cannot be replaced Huge nucleus Nissle substance
Support cells in the brain (4)
- Astrocytes
- Oligodendroglia
- Microglia
- Ependymal cells
Brain herniation
Caused by raised intracranial pressure
Cingulate gyrus, cerebral tonsil, cerebral uncus
Treatment by drilling in skull
Developmental disorders
Cause is usually known
Genetic diseases, chromosomal abnormalities, intrauterine infections (TORCH syndrome)
TORCH syndrome
To: toxoplasmosis
R: rubella
C: cytomegalovirus
H: hepatitis, HIV
Anencephaly
Upper part of neural tube fails to develop - no brain
Meningecele
Vertebrae surrounding spinal cord fails to grow
Myelomeningocele
Spinal cord does not form
Born with significant paralysis
Spina bifida
Spinal cord fails to close properly, vertebrae do not fuse around it
Intracranial hemorrhages (4)
Defined by location
- Epidural
- Subdural
- Subarachnoid
- Intracerebral
Epidural hematomas
Between skull and dura Rupture of middle meningeal artery Takes hours to developed and localized Can be lethal Coma
Subdural hematomas
Located between dura and arachnoid Caused by blunt trauma Ruptured bridging veins Venous bleeding occurs slowly, so many be asymptomatic Can produce headache, coma, death
Subarachnoid hemorrhages
Located between arachnoid and pia layer of meninges
Caused by traumatic contusion of brain, rupture of congenital aneurysms
High mortality
Intracerebral hemorrhages
Rupture of intracerebral vessels
Common complication of head trauma, gunshot wounds
Non-traumatic forms include stroke
Common with poor clotting
Caused by arterial hypertension, or vascular malformations
Basal ganglia, cerebellum, pons
Cerebrovascular disease/stroke (3)
Third most common cause of death Most common crippling disease Atherosclerosis of arteries supplying the brain - plaques can rupture and occlude 1. Global ischemia 2. Cerebral infarct 3. Intracerebral hemorrhage
Stroke
Sudden persistent loss of brain function from a vascular cause
Risk factors of cerebrovascular disease/stroke
Hypertension, smoking, diabetes, elevated cholesterol
Global ischemia
If many vessels are narrowed: multiple infarcts
Over time can lead to dementia
Hypoperfusion from cardiac arrest or peripheral bleeding
Watershed infarcts
Laminar necrosis
Cerebral infarct
Caused by thrombotic occlusion, thromoboemboli
Pale or hemorhagic infarct (reperfusion)
Edematous: from surrounding brain tissue
Fluid filled cavity
Never heals
Clinical presentation depends on site of occlusion
Middle cerebral territory strokes
Contralateral hemiplegia and sensory loss
Global aphasia in the dominant hemisphere
Acute stroke edema
Can kill
Accumulation of fluid because BBB is disrupted
Raised intracranial pressure
Concussion
Transient loss of consciousness
Contusion
Crush brain, some bleeding
Laceration
Tear
Neck and spinal cord injuries (3)
- Hyperextenion
- Hyperflexion
May transect spinal cord leading to paralysis
Routes of infection of CNS (3)
- Direct extension
- Via blood
- Via nerves
Bacterial infection of CNS
Hematogenous route or from septic emboli
Meningitis, abcesses, myelitis, encephalitis, neurosyphilis, AIDs related CNS lesions
Meningitis in adults
Caused by streptococcus pneumoniae
Meningitis in babies
Caused by Group B streptococci, E. coli, Listeria monocytogenes
Meningitis in children/adolescents
Caused by Neisseria meningitidis
Brain abcesses
Staphylococcus aureus
Rare infections of the CNS
Tuberculosis, syphilis
Viral infections of CNS
Hematogenous route or along nerves
Measles, rubella, adenovirus, herpes, cytomegalovirus, rabies
Protozoal infections of the CNS
Hematogenous route
Toxoplasma gondii causes encephalitis in neonates and immunosuppressed patients
Fungal infections of the CNS
Hematogenous route
Cadida albicans, Aspergillus flavus, Cryptococcus neoformans
Early multiple sclerosis lesion
Macrophages phagocytose myelin
Exit lesion
Axons remain partially
Left with reactive astrocytes in lesions
Late multiple sclerosis lesion
Astrocytes react to damage in early lesion
Cells cannot come remyelinate the axon
Multiple sclerosis
Demyelinating disease, presumed autoimmune
Loss of neurons over time
Women x2 > men
Commonest neurological disease in young adults
High prevalence of certain major histocompatibility antigens
Oligoclonal T-cell population in the brain
IgG in CSF composed of oligoclonal bands
Episodes of exacerbation and remission - eventually becomes chronic
Sensory abnormalities in MS
Loss of sense of touch
Motor abnormalities in MS
Muscle weakness, unsteady gait, incoordination of movements, sphincter abnormalities
Diagnosis of MS
2 episodes separated in space and time
Remission between, different parts of the brain
Inborn errors of metabolism (2)
- Tay-Sachs disease
- Niemann-Pick disease
Enzymes that metabolize components of lipids are lost
Genetic
Nutritional disease
Acquired
Inadequate intate of vitamins
Vit B1, B12, nicotinic acid
Vitamin B1 deficiency
Wernicke-Korsakoff syndrome
Wernicke-Korsakoff syndrome
Caused by B1 deficiency
Two diseases rolled into one
Wernicke
Acute, abnormal eye movements
Korsakoff
Chronic, short-term memory loss
Vitamin B12 deficiency
Subacute combined degeneration of the cord, peripheral neuropathy
Leading to loss of sensation and motor function - demyelination of dorsal tracts
Uncoordinated movements and psychiatric symptoms
Nicotinic acid deficiency
Causes pellagra
Dermatitis, diarrhea, delirium (dementia)
Alcoholism
CNS depressant than can kill
Direct and indirect effect on CNS
Indirect affects of alcoholism
Damage to liver and nutritional deficiencies
Nutritional deficiencies caused by alcoholism (4)
- Thyamine deficiency
- Wernicke-Korsakoff
- Hepatic encephalopathy
- Pontine myelinolysis
Hepatic encephalopathy
Too much ammonia in liver
Pontine myelinolysis
Damage to myelin in pons
Direct affects of alcoholism (5)
- Loss of neurons
- Cerebellar atrophy
- Myelopathy
- Neuropathy
- Myopathy
Alzheimer’s disease
Sporadic
Increased levels of beta-amyloid - chronic ischemia in the brain
Atrophy greatest in frontal and temporal lobes
Age is factor
Dementia
Progressive loss of cognitive functions
Gross examination of Alzheimer’s
Brain appears atrophic
Narrowing of gyri
Widening of sulci
Histological changes in Alzheimer’s
Most prominent in cortex
Neuritic plaques with beta-amyloid core
Neurofibrillary tangles
Parkinson’s disease
Subcortical neurodegenerative disorder
Usually affects elferly
Causes unknown, damage to substantia nigra in brain - decreased dopaminergic neurons
Symptoms of Parkinson’s disease
TRAP
Tremor, rigidity, brady or akinesia, postural instability
Gross examination of Parkinson’s
Substantia nigra looks pale
Histological characteristics of Parkinson’s
Loss of neuromelanin-rich neurons
Present of Lewy-bodies
Huntington’s disease
Autosomal dominant
Disease only occurs when repeats reach a threshold
Involuntary, gyrating movements, progressive dementia
Atrophy of cortex, caudate, putamen
Loss of neurons, reactive gliosis
Amyotrophic lateral sclerosis
Neurodegenerative disease Sporadic 10% have mutations in SOD-1 gene Older men, women Incurable
Motor symptoms of Amyotrophic lateral sclerosis
Weakness, progressive wasting of muscles, fasciculations, slurred speech
Generalized epilepsy
Begins in childhood, idiopathic
Generalized electrical discharges leading to aura, tonic-clonic seizures and post-ictal drowsiness
Focal epilepsy
Secondary to a focus that can be detected using EEG or imaging
Causes include brain trauma, meningitis, stroke, brain tumor
May be controlled by drugs but may need surgery
Neoplasms of CNS
Rare - 2% of cancer
High mortality (rapid growth, intracranial pressure)
Usually younger
Primary CNS tumors (4)
- Glial cells
- Neural cell precursors
- Meninges
- Cranial and spinal nerves
Atrocytomas
Solid cerebral tumors in adults
Cystic cerebellar tumors in children
Well-differentiated astrocytes
Progress into lesions
Glioblastoma multiforme
Most common CNS tumor
65yo
Lateral hemispheres
Gross appearance of glioblastoma multiforme
Parts are necrotic, yellow Parts are hemorrhagic red Parts are white Irregularly shaped Poorly demarcated Butterfly-like appearance
Histological characteristics of glioblastoma multiforme
Highly anaplastic astrocytic cells
Fetal appearance to cells, enlarged, bizarre shaped, multinucleated cells with well-developed cytoplasms
Numerous mitotic figures
Proliferatie changes in blood vessels
Oligodendrogliomas
Occur in cerebral hemispheres
Middle-aged adults
Well circumscribed, partially cystic, calcified
Well-differentiated oligodendroglia
Possible progression to glioblastoma multiform
Ependymomas
Children: ventricles
Adults: spinal cord
Tumor cells line papillary structures or form rosettes
Medullablastoma
Cerebellum
Childhood
Uncertain origin - primite neurectodermal cells
May enter CSF and metastasize in other parts of CNS
Poor prognosis
Meningiomas
Arise from meninges
Dural baed
Mainly benign
Located near midline, base of brain, along spinal cord
Cause epileptic seizures or motor deficits
Excellent prognosis
Neuromas
Schwannomas
Neurofibromas
Neurofibromatosis type I
Produces multiple peripheral neurofibromas
Neurofibromatosis type II
Produces acoustic schwannomas as well as multiple meningiomas
Metastases to brain
50% of all tumors are metastases
Solitary or multiple
Lung, breast, melanoma
