Nervous System Flashcards
Describe the functions of the four major lobes of the brain.
Frontal **motor functions, behavior, emotions, higher intellect.
Parietal **sensory functions.
Occipital* visual center. *
Temporal **hearing and smelling.
Compare the functions of the midbrain, pons, and medulla oblongata with that of the cerebellum.
midbrain, pons, MO = myelinated nerve bundles connecting brain to SC
visual and auditory reflex, cardiac, vasomotor, respiratory centers
cerebellum = sensory input from SC and inner ear to cortex
balance, muscle tone, mvmt coordination
Describe the function of the spinal cord.
anterior horn >> peripheral nerves
- extensions of cortical and subcortical brain neurons
- carry motor impulses
posterior horn >> spinal ganglia
- carry sensory input
Describe the circulation of the cerebral spinal fluid.
Produced by choroid plexus in 3rd ventricles. Flows at low pressure lateral ventricles >> 3rd V >> 4th V >> lateral openings + median opening >>* central canal of SC*
List the main cells of the nervous system.
Glial cells (support) = astrocytes, oligodendroglia, microlia, ependymal
Neurons
What are the most important diseases of the nervous system.
- Developmental and genetic diseases
- Diseases caused by trauma
- Circulatory disorders
- Infectious diseases
- Autoimmune diseases
- Metabolic and nutritional diseases
- Neurodegenerative diseases
- Brain tumors
What are the sites of brain herniation caused by intracranial hypertension?
Subfalcine herniation: cingulate gyrus protrudes beneath the falx cerebri
Transtentorial herniation: uncus protrudes tentorium cerebelli
Tonsillar hernation: cerebellar tonsils protruding into the foramen magnum
List the main dysraphic disorders of the CNS and describe their pathogenesis.
Incomplete fusion of the neural tube >> dysraphic disorders
anencephaly **calvaria not formed
meningocele **meninges protrude through defect
myelomeningocele **protrusion of meninges + SC
spina bifida absence of vertebral arches
List the most important intracranial hemorrhages and describe their causes
**Epidural hematoma **usually from fracture, rupture of middle meningeal artery, lethal
**Subdural hematoma **tearing of thin-walled veins, accumulation over lateral hemispheres
**Subarachnoid hemorrhages **ruptured aneurysms, typically at the base of the brain, may be preceded by HTN
Intracerebral head trauma, stroke, hematologic disease
What is stroke?
Ischemic (85%)
or hemorrhagic (15%)
What is global cerebral ischemia, and what are its consequences?
Widespread atherosclerotic narrowing over entire cerebrovascular system
small lacunar infarcts >> multi-infarct dementia
What is the pathogenesis of “watershed infarcts” and laminar necrosis of the brain?
Watershed infarcts: hypoperfusion of the marginal zones between arteries (carotid and basilar)
Laminar necrosis: hypoperfusion of deeper zones of gray matter that receive blood from penetrating arteries
Describe the pathology of cerebral infarcts.
Thrombotic occlusion >> infarct
ischmic brain = liquefactive necrosis = encephalomalacia
- pale or hemorrhagic (more common with arterial thrombi)
infarct becomes pseudocyst
Correlate the pathology of intracerebral hemorrhage with the clinical features of the disease.
Most common site: basal ganglia
infarct >> pseudocysts with wall of hemosider laden macrophages
Basal ganglia: hemiplegia, hemiparesis
Cerebellar: nausea, vomiting, loss of balance, HA
Pontine: death
What are the main pathologic findings after brain injury?
**Concussion: **transient LOC, NO significant brain changes
**Contusion: **bruise, hemorrhagic coup and contercoup lesion
Laceration: open trauma, neurologic deficit
Compare hyperextension and hyperflexion injuries of the cervical spine.
hyperextension - rupture of anterior spinal ligaments, compression of posterior SC
hyperflexion - compression of anterior SC
Compare bacterial and viral infections of the CNS
Bacterial
Spread: sepsis, bacteremia, septic emboli, open wounds, sinus infection, inner ear infection
*Strep pneumoniae causes most cases of bacterial meningitis in adults
Viral
Spread: hematogenous spread
*herpes = most common viral cause of localized encephalitis in the US
What are prions?
Prions = small infectious particles composed of proteins
*do not contain dna/rna
List the most important protozoal and fungal causes of opportunistic diseases of the CNS.
Protozoal: toxoplasmosis (neonates, AIDs)
Fungal: candida, aspergillus, cryptococcus (AIDs)
Compare the pathology of encephalitis and meningitis.
encephalitis = localized or diffuse inflammation of brain parenchyma
usually virus invades neural or glial cells
meningitis = inflammation of the meninges
Describe the features of neurosyphilis.
- usually presents as chronic meningitis
- meninges: infiltrated with lymphocytes and plasma cells (small BV)
- perivascular inflammation >> cortical ischemia
- tabes dorsalis = atrophy of dorsal (sensory columns)
What are the most important AIDS-related CNS lesions?
HIV infects macrophages and T lymphocytes, and these cells “import” the virus to the CNS
toxoplasma, cryptococcus
What is MS?
An autoimmune demyelinating disease
W > M, 20-45 y/o
Correlate the pathologic features of MS with the clinical signs and symptoms of this disease.
Presence of IgG oligoclonal bands >> responding to antigen?
- Typically involves white matter >> both sensory and motor abnormalities
- Periventricular plaques (lateral hemispheres)
- early lesions = lymphocytes and foamy macrophages
- late lesions = demyelinated axons and reactive astrocytes (gliosis)
