chap 23 - nervous system Flashcards
neurons
send signals
glia
supporting cells
- astrocytes, oligodendrocytes, ependymal, microglia, schwann cells
astrocytes
help to form the blood brain barrier
oligodendrocytes
wrap their “arms” around the axons and neurons to myelinate neurons (which speeds up transmission)
ependymal cells
found in ventricles of the brain
microglia
type of white blood cells that decrease bacteria in the brain
schwann cells
similar to oligodendrocytes but located in PNS
components of the brain
cerebrum, cerebellum brain stem
- sensory and motor contralateral
- one side dominant
vascular supply of CNS
Interconnections at base of brain
Lack of interconnections elsewhere
Structure of brain capillaries
Blood brain barrier
Only small, fat soluble molecules move across
meninges
dura mater, arachnoid mater, subarachnoid space, and pia mater
cerebrospinal fluid
Made by choroid plexus
Arachnoid granulations - CSF exit to blood
Components
Clear
Small amount protein
Glucose 50-80 mg/dl
Gives buoyancy to the brain, shock absorber for the brain as well, chemical buffer to large changes in the chemicals circulating
Needs to be able to circulate
most frequent and serious problems
Headaches
Cerebrovascular accidents - brain attack
Traumatic injuries
Infections
Degenerative disease
Neoplasms
common signs and symptoms
Headaches
Weakness - one sided → hemiparesis
Nausea and vomiting
Motor disturbances, stiff neck or back, rigid muscles, seizures, convulsions, paralysis
Sensory disturbances, especially vision or speech
Drowsiness, stupor, or coma
Mood swings
Intellectual disturbances - loss of critical thinking skills
Memory capabilities
common tests
Analysis of cerebrospinal fluid
- Examined for presence of leukocytes (indication of infection in brain), red blood cells, neoplastic cells, and microorganisms
Electroencephalogram (EEG) - brain activity
Radiologic procedures
- Skull x-rays to detect fractures
- Angiography is used to: (looks at blood vessels)
- Look for abnormal distribution or distortion of vessels in the region of a lesion
-Demonstrate vessel occlusion in patients with CVA and to find the site of rupture of an intracranial aneurysm
Neurologic examination includes:
-Examination of motor and sensory systems
-Observing gait, posture, and symmetry of muscle mass
-Testing muscle strength, coordination, and reflexes
Testing of cognitive function
-Eliciting a careful history of abnormal sensations
-Testing for diminished or absent sensory perception
- Knee-jerk reflex
genetics/developmental disease
Deleterious forces acting within first half of gestation
Due to
Genetics
Infection
Traumatic insult to brain
Examples
Down syndrome - trisomy 21
Neural tube defects
neural tube defects
Incomplete development of brain, spinal cord, and/or meninges
Neural tube is the precursor to the spinal cord
Common = 2 per 1,000 births in U.S
Types
Spina bifida - affects spinal cord
Anencephaly = without brain
Many related to deficiency in what vitamin? Folate or folic acid (a B vitamin)
Diagnosis
Ultrasound
Amniocentesis
hydrocephalus
Accumulation of excess CSF
Result from:
Obstruction to flow of CSF
Over production of CSF
Inability of arachnoid granulations to restore water of CSF back into circulation
Children vs. adults
Children, enlargement of skull
signs and symptoms of hydroencephalus
Dilated pupils
Increased blood pressure
Headache
nausea/vomiting
Seizures
drowsiness/altered consciousness
treatment of encephalus
Eliminate the cause
Reduce the pressure
Hydrocephalus = intracranial shunts
Edema = osmotic agents
Craniotomy
Steroid therapy
Medially induced coma
Hypothermia = slow brain metabolism
inflammatory diseases
Numerous infectious diseases involve the brain preferentially:
Meningitis
Encephalitis
polio
meningitis
Inflammation of the meninges
Most often caused by bacteria
Bacteria gains access to brain and spinal cord via the blood
Onset is usually abrupt
Major signs and symptoms
Fever
Headache
Neck rigidity
Diagnosis
treatment
encephalitis
Enceph = the brain
Diffuse inflammation of the brain
Usually caused by viral infections
Many are mosquito-borne
West nile encephalitis
Symptoms and signs are generalized - lots of parts of the brain are affected
Irritability, drowsiness and headache
Diagnosis
Depends on culture and identification of viral infections
Spinal tap
No specific treatment
Patients die, recover fully, or recover with variable neurologic deficit
poliomyelitis
Caused by poliovirus, type of enterovirus (intestinal)
Pathogenesis
Transmitted by fecal-hand-oral contamination
Infects the spinal horn of the vertebrae which is where motor neurons and spinal nerves are located which is why some cases result in paralysis
Outcomes
95% asymptomatic
4-8% minor specific illness
Malaise or headache
1-2% nonparalytic aseptic meningitis
Less than 1% paralytic
cerebrovascular accident
Sudden neurologic deficit caused by vascular occlusion
Leads to infarcts
The brain can only last 5 minutes without oxygen, the lowest of any organ
Fourth leading cause of death in U.S
Types of stroke
Cerebral thrombosis: most common, thrombosis of cerebral artery narrowed by atherosclerosis
Abnormal blood clot
Cerebral embolus: occurs less frequently; blockage of cerebral artery by fragment of blood clot from an arteriosclerotic plaque or from heart
Traveling blood clot
Cerebral hemorrhage: most serious type of stroke; usually from rupture of a cerebral artery in person with hypertension
Burst aneurysm → severe bleeding in the brain
May also be due to ruptured blood vessel, ruptured aneurysm
Risk factors
Hypertension
Weakened vessel
cerebral thrombus
Vascular occlusions results in infarcts in brain tissue supplied by affected vessel
Damaged brain tissue
Loses function within minutes
Becomes soft and necrotic within a few days
Tissue is lost from the area
CVAs caused by brain hemorrhage
Signs and symptoms depend on location and size
Up to half of patients die within hours because accumulation of blood:
Displaces adjacent tissue
Rapidly elevates intracranial pressure - because the brain is enclosed in the skull swelling has no where to go
Strokes may occur suddenly or preceded by
transient ischemic attacks (TIA)
transient ischemic attacks
Temporary often recurrent episodes of impaired neurological activity resulting from insufficient blood flow to a part of the brain
Mini stroke
Warning for impending stroke
speed is important for treatment
CVA signs and symptoms
Impaired speech or consciousness
Hemiparesis
Poor coordination
Confusion
CVA outcomes
⅓ die within first two weeks
⅓ recover with neurological deficit
⅓ recover with no deficit
Dissolve embolus
Largely dependent on area of brain affected and size
When the brain is damaged by ischemia following a cerebrovascular accident
Neurons and oligodendroglia readily die
Neurons cannot regenerate themselves - scar tissue is formed in place
Astrocytes proliferate rapidly and repair the injury structurally by forming a scar
traumatic brain injury
Serious public health concern
Occurs when the brain collides with the inside of the skull - basically bruising the brain
Causes bleeding, bruising, and tearing of nerve fibers
A traumatic insult to the brain possibly producing physical, intellectual and emotional changes
May be due to
Transportation accidents
Falls
Sports-related event
Violence
Range in severity
Mild
serious
CNS trauma
Direct or indirect
Coup - where the actual impact occurred
Contrecoup - rebound of the brain and shifting in the skull
Results
Fracture
Intraparenchymal injury - within the brian
Vascular injury
Consequences depend on location and size of lesion
cerebral concussion
Description
Most common head injury
Immediate loss of consciousness for seconds to minutes - but not noticeable in all cases, especially in a mild concussion
Etiology
Blunt force impact to head
Brain strikes and rebounds from skull
Disrupts normal brain activity
types of hemorrhages in the brain
epidural, subdural, and subarachnoid
epidural hemmorhage
artery
- fatal within 24 hours
- forms quickly
subdural hemorrhage
slow venous bleeding
subarachnoid hemorrhage
Not as commonly due to trauma, but may be
Arterial bleeding
Typically from circle of willis
Blood in subarachnoid space
- most likely to be due to an aneurysm
treatment for TBI
Mild TBI = bed rest and analgesic - want to limit brain activity - no reading, school, work, etc.
Severe TBI = diuretics (want to decrease any extra pressure), anti seizure and coma-inducing medications, surgery to remove clots, repair fractures, or create an opening to provide space for the brain to swell
CNS degenerative disorders
Degeneration of cortical neurons
Alzheimer disease
Degeneration of basal ganglia neurons
Parkinson’s disease
Huntington’s disease
Degeneration of motor neurons
neurodegenerative disorders etiology
Several factors combined are implicated
Genetic predisposition
Environmental toxins
Oxidative stress
Aging
dementia
Global, irreversible deterioration of cerebral cortex
Not normal part of aging
Losses
Orientation
Memory
Language
Judgment
Decision making
alzheimer’s disease
Most common form of dementia
Irreversible, progressive, chronic
Unknown etiology
Atrophy of cortical parts of frontal and temporal parts of the brain
Characteristics
Dementia; progressive loss of cognitive functions, memory
Emotional disturbances
1 in 10 over age 65
Anatomic and biochemical features
Amyloid-beta protein-forming plaques - the brain can’t clear them and this disrupts communication between neurons
Neurofibrillary tangles
Decreased acetylcholine production
Risk factors
Age
Chronic hypertension
Head injury adults are three times more likely to develop alzheimer’s disease
multi-infarct vascular dementia
Cumulative brain damage from small strokes
Second most common cause of dementia
Treated by addressing underlying cause, such as hypertension
parkinson’s disease
Subcortical neurodegenerative disorder
- Basal ganglia: important for modifying movement
Cause unknown
Decreased number of dopaminergic neurons in substantia nigra
- these neurons make dopamine
Disturbances of movement, rigidity, bradykinesia, pill rolling tremor, postural instability
Treated with drugs that increase dopaminergic activity, with dopamine
amyotrophic lateral scelrosis
Rare age-associated neurodegenerative disease
Death of alpha motor neurons
Affects upper and lower motor neurons
Atrophy
Paralysis of muscles
Respiratory problems
No treatment or cure
Cause unknown
Two forms
Sporadic
Familial
neoplasia
Small, slow-growing tumors that would be benign elsewhere can readily disrupt vital functions in strategic locations and kill the patient
Other benign tumors may occur in inoperable locations
Metastatic tumors more common than primary tumors
Primary tumors
Glioma: Mostly poor prognosis with deep location in brain; surgery, radiation, chemotherapy
Astrocytoma
Oligodendroglioma
Lymphoma
Meningioma
brain neoplasms
Most common signs and symptoms:
Increased pressure because of mass lesion
Accompanying edema
Generalized symptoms such as headaches, vomiting, blurred vision, and seizures
- the brain has no where to swell
organ failure
Brain death
Patient often considered legally dead if two successive electroencephalograms taken 24 hours apart both show complete absence of electrical activity in the brain
seizures
sudden transient alteration or brain function caused by an abrupt, explosive, disorderly discharge of cerebral neurons
epilepsy
present when 2 or more unprovoked seizures occur at an interval greater than 24 hours apart
causes of provoked seizures
fever, electrolyte imbalances (hypocalcemia, alkalosis), hypoglycemia, hypoxia, arthemia, CNS infection or damage, head trauma
causes of unprovoked seizures
idiopathic
- strong genetic basis
types of seizures
partial seizures, simple, complex, generalized, convulsive, nonconvulsive, absence (petit mal), atonic, myoclonic, clonic, tonic, grand mal
simple seizure
without loss of consciousness
complex seizure
loss of consciousness
absence (petit mal) seizure
brief loss of consciousness
atonic seizure
loss of muscle tone
myoclonic seziure
muscles contract
clonic seizure
repetitive jerking movements
tonic seizure
muscle stiffness, rigidity
grand mal seizure
muscle contractions and loss of consciousness
diagnosis of seizures
electroencephalogram, MRI/CT
treatment of seizures
avoidance of precipitant, anticonvulsants (reduce electrical activity of the brain), surgery (removal of seizure focus
huntington’s disease
autosomal dominant neurodegenerative disease
- characterized by chorea = involuntary but conscious, gyrating movements, progressive dementia
- atrophy of cortex, subcortical nuclei, most prominently in caudate putamen
- late onset
- high rate of suicide
glioma
most poor prognosis with deep location in brain, surgery, radiation, chemotherpay
menigioma
arise from meninges, benign in a biological sense, but the location needs to be considered to determine the severity
diseases of peripheral nerves
axon vs schwann cells
motor vs sensory
types
- autoimmune, inflammatory
- toxic
- trauma
- vascular, especially diabetes - high blood glucose
tumors
neuropathy = loss of sensation
amyotrophic lateral scleorsis
aka lou gehrig’s
- rare age-associated neurodegenerative disease
- death of alpha motor neurons
- affects upper and lower motor neurons
- atrophy
- paralysis of muscles
- respiratory problems
no treatment or cure, cause is unknown
two forms: sporadic and familial
guillain-barre syndrome
polyneuropathy = many nerves in different parts of body
- rare: 1 in 100,000
symptoms
- weakness and tingling
autoimmune - immune system attacks peripheral nerves, leading to inflammation, progressive weakness from extremities towards trunk
- can become life-threatening due to breathing issues
- rare cases, death
- often preceded by viral or bacterial “flu-like” infection
- most recover, but some may have permanent nerve damage
bell palsy
idiopathic unilateral facial nerve paralysis
- temporary
symptoms
- inability to control facial muscles on affected side
- twitching, weakness, drooping eyelid, drooling
prognosis = good, symptoms recede within 2 weeks after initial onset, and complete recovery within 3-6 months
headache
Diffuse pain occurring in any portion of the head
Primary: tension, migraine, cluster headaches
Secondary: underlying structural problems
No pain receptors in brain
Result of vasodilation
Thus treatment may include vasoconstrictors
