Neurology- study of the nervous system
ANATOMY
Nervous system= central nervous system, peripheral nervous system, autonomic nervous system
All working together to coordinate body activities, permit assimilation of experiences &
program behavior
Central nervous system- CNS; brain & spinal cord
Peripheral nervous system- PNS; cranial/spinal nerves that control voluntary movement of
skeletal muscles
Autonomic nervous system- ANS; functional division of nervous system that is then divided
into sympathetic/parasympathetic divisions
Nerve- collection of nerve fibers outside CNS; held together & strengthened by loose connective
tissue; enclosed in endoneurium sheath & a group of nerves are surrounded by perineurium
sheath
Most nerves are mixed- contain both motor/sensory neurons in them
Ganglion- collection of neuron cell bodies located outside CNS
Nervous system composed of two principle categories of cells
Neuroglia- glial cells
Supportive cells that aid neurons; 5x more abundant
Types of neuroglia
Neurolemmocytes- Schwann cells which form myelin layers around axons
in PNS
Oligodendrocytes- Schwann cells which form myelin layers around axons in CNS
Microglia- migrate through CNS removing foreign/degenerated material
Astrocytes- regulate passage of molecules from blood to brain; most abundant
type in CNS; have vascular processes that surround outer surface of
brain capillaries & act as a barrier to decide which molecules can enter
brain & which cannot; form blood-brain barrier
Ependymal cells- line ventricles of brain & central canal of spinal cord
Ganglionic gliocytes- support neuron cell bodies of PNS
Neuron- basic structural/function unit; specialized to respond to stimuli, conduct impulses &
release specific chemical regulators; can’t divide mitotically but some can sprout new
branches under certain conditions
Parts : Cell body- enlarged portion that resembles other cells (contain
nucleus/cytoplasm); also contains chromatophilic substances that are
specialized ER for protein synthesis & neurofibrils which may be used to
transport materials
Dendrite- branched processes used to receive stimuli from neighboring neurons
& carry them to the cell body; covered by spicules to increase surface
area to provide lots of contact points for other neurons
Axon- relatively long process that conducts impulses away from cell body
Functional Classification
Sensory (afferent) neurons
Conduct impulses to CNS from receptors both internally/externally
Exteroceptors- receive stimuli from external environment
Interoceptors- receive stimuli from internal environment
Propriocentpros- receptors in muscles, tendons & joints
Motor (efferent) neurons
Conduct impulses from CNS to effectors (muscles or glands)
Associative (association) neurons
Interneurons
Connection between sensory/motor neurons
Found in spinal cord & brain
Structural Classification
Bipolar- spindle shaped neuron with processes at both ends
Pseudounipolar- has single process that divides into 2; most sensory neurons
are this type
Multipolar- most common type; several dendrites & 1 axon; motor neurons
Neurons can be either myelinated or nonmyelinated
Myelination- process in which a Schwann cell surround an axon or dendrite to
provide support & aid in impulse conduction
Myelinated neurons make up “white matter”
Outer surface of sheath is encased in neurolemmal sheath that promotes
neuron regeneration
Gaps in sheath are called neurofibril nodes or nodes of Ranvier which help to
move impulse along neuron
CNS contains both gray/white matter
Gray matter- made of either nerve cell bodies/dendrites or bundles of unmyelinated axons/neuroglia
Found as the outer convoluted cortex layer of the brain or the middle of the spinal cord
White matter- aggregations of dendrites & myelinated axons & associated neuroglia
Found as the center of the brain or the outer columns of the spinal cord
Brain is enclosed by cranium (bones) & membranes (meninges) as well as being bathed in
cerebrospinal fluid
Meninges- connective tissue encasements that form protective membranes between bone & CNS tissue
3 layers
Dura mater- in contact with bone; made of dense connective tissue; double layered
around brain but not around spinal cord; spinal dura mater forms a dural sheath
around the spinal cord
Arachnoid layer- middle layer; delicate netlike membrane whose space contains
cerebrospinal fluid
Pia mater- thin membrane; tightly bound to surface of brain/spinal cord; made of
modified loose connective tissue; highly vascular & nourishes cells of
brain/spinal cord
Cerebrospinal fluid
Circulates within hollow ventricles of brain, central canal of spinal cord & subarachnoid space
around CNS
Clear lymph-like fluid made by filtering blood plasma through choroid plexuses
Contains proteins, glucose, ions, urea, WBC
Forms protective cushion around/within CNS; distributes nutrients & removes wastes
Serves as exchange medium between blood & nervous tissue
Ventricles of brain are connected together
1st & 2nd are in hemispheres of cerebrum; called lateral ventricles
3rd is in diencephalon
4th is in brain stem between pons/cerebellum; cerebrospinal fluid exits here & is returned to
blood
Central Nervous System
Brain 1.5 kg
100 billion neurons
Needs continuous supply of oxygen/nutrients as well as rapid removal of wastes
Receives about 20% of total resting cardiac output (750 mL blood/min)
Main regions: cerebrum, diencephalon, cerebellum, brain stem
Cerebrum
5 paired lobes within 2 convoluted hemispheres
largest part of brain
Important in higher brain functions, sensory perceptions, voluntary movement, memory
storage, thought/reasoning, emotional functions
Separate areas for controlling motor/sensory activities but no single area is entirely responsible
for total intellectual capacity since intelligence develops through storage of impressions
Right/left hemispheres separated by longitudinal cerebral fissure & connected internally by
corpus callosum
Each hemisphere contains a central lateral ventricle filled with cerebrospinal fluid
Women have more connections between hemispheres than males which may be due to
environmental differences & experiences growing up
Two layers
Cerebral cortex is about 3 dimes thick & made of gray matter with lots of convolutions
(gyres) which triple the area of gray matter
White matter is found underneath gray matter
Lobes
Frontal- anterior portion bordered on back by central sulcus & on sides by lateral sulcus
Used for initiating voluntary motor impulses for movement, analyzing sensory
experiences & providing responses relating to personality, related to
memory, emotions, reasoning, judgment, planning, imagining, verbal
communication
Parietal- behind frontal lobe; central gyrus is behind central sulcus & responds to stimuli
from skin/muscle receptors; precentral gyrus responsible for motor movement
Also used for understanding speech, articulating thoughts/emotions, reading,
arithmetic, interpreting textures/shapes
Temporal- below parietal lobe & behind frontal lobe; separated off by lateral sulcus
Contains auditory sensors & interprets/stores auditory & visual memories
Occipital- posterior portion of cerebrum; above cerebellum
Integrates eye movements (directs/focuses eyes), processes visual images &
stores visual memories
Insula- deep lobe not viewed on surface; not paired; lies below lateral sulcus
Thought to integrate cerebral activities & to function in memory
Diencephalon
Surrounded by cerebral hemispheres
Thalamus- large oval mass of gray matter
Relay center for all sensory impulses to cerebral cortex, used for sensory interpretations
& as clearinghouse for information from spinal cord to cerebrum
Hypothalamus- below thalamus
Acts to accelerate/decelerate body functions, secretes 8 hormones, regulates body
temperature, regulates water/electrolyte balance in blood, regulates
hunger/control of GI activity, regulates sleep/wakefulness, controls sexual
responses to tactile stimuli
Epithalamus- posterior part of diencephalon
Contains choroid plexus where cerebrospinal fluid is made as well as pineal gland
Pituitary gland- attached to hypothalamus by infundibulum
Cerebellum
2nd largest structure of brain
Occupies bottom back of cranial cavity
Separated from cerebrum by transverse fissure
Made of two hemispheres connected by vermis & connected to rest of brain through cerebellar
peduncles (3 paired bundles of nerve fibers)
Outer layer of gray matter & thick deeper layer of white matter (tracts of white matter called
arbor vitae)
Coordinates skeletal muscle contractions, responsible for learned rote movements (playing an
instrument), subconscious regulation of muscle activities for maintaining posture,
standing upright, walking/running, ensures smooth/coordinated muscle activity
Brain stem
Attaches to spinal cord
Relays information to/from cerebrum & plays role in controlling body actions
Midbrain
Corpora quadrigemina- concerned with visual/auditory reflexes
Cerebral peduncles- support/connect cerebrum to other parts of brain
Red nucleus- connects the cerebral hemispheres & the cerebellum
Substantia nigra- inhibits forced involuntary movements
Pons- round bulge on inferior surface of brain
White fiber tracts that connect cerebellum, midbrain, medulla oblongata & midbrain
Contains several nuclei associated with cranial nerves
Medulla oblongata- bulbous structure at bottom of brain stem
Composed of nerve bundles & white matter
Contains centers for controlling vital visceral functions (cardiac, vasomotor, respiratory)
as well as centers for reflexes/vomiting
Reticular formation- network of nerve fibers within brain stem; located in spinal cord, pons,
midbrain, thalamus & hypothalamus
Functions to arouse the cerebrum & keep it in state of alert consciousness
Maintains muscle tone & coordinates contractions of skeletal muscles
Spinal cord
Flattened slightly to make it oval in cross section; enlarged in cervical/lumbar regions where
appendage nerves exit
Protected by meninges/cerebrospinal fluid
Made of centrally located gray matter & peripherally located ascending/descending tracts of
white matter
Gray matter is involved in reflexes; white matter conducts impulses to/from brain
Core of gray matter resembles letter H & has projections called horns (posterior/anterior) and
transverse bar (center of spinal cord) is the gray commissure with central canal
Central canal is continuous with ventricles of brain & is filled with cerebrospinal fluid
6 columns of white matter called funiculi (2 anterior, 2 posterior, 2 lateral) each made of both
ascending/descending tracts
Nerve fibers in tracts either remain on the same side of the brain/spinal cord or can cross over
within the medulla oblongata; crossing over referred to as decussion
Descending tracts grouped according to place of origin; corticospial descend without
interruption from cerebral cortex to lower motor neurons (85% cross over in MO & 15%
don’t cross over), this crossing over results in right hemisphere controlling muscles on
left side of body; extrapyramidal tracts originate in brain stem
There are no descending tracts from cerebellum since it can influence motor activity only
indirectly
Peripheral Nervous System
All nervous tissue outside CNS including sensory receptors, nerves & their ganglia/nerve
plexuses
Conveys impulses to/from brain to spinal cord
Important function in relaying impulses in reflex action
Somatic NS- cranial/spinal nerves that control voluntary movement of skeletal muscles
Autonomic NS- consists of nerves that control involuntary actions
Spinal nerves
31 pairs exit spinal cord through intervertebral foramina
8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal
Each is a mixed nerve- posterior (dorsal) root is sensory fibers, anterior (ventral) root is motor
Divide into several braches after it leaves the intervertebral formen & forms groups called
rami or ramus
Except in most thoracic nerves, the anterior rami split again into nerve plexuses
Cervical plexus- rami of C1-C4 & part of C5 nerves
Innervates skin/muscles of neck & part of head/shoulders
Fibers from C3-C5 unite to become phrenic nerve that innervates diaphragm
Brachial plexus- comes from C4-T2
Innervates entire arm as well as shoulder/neck muscles
Major nerves from this: axillary, musculocutaneous, radial, ulnar, median
Lumbar plexus- T12-L5 origins
Innervates structures of lower abdomen & lower extremity
Contains femoral nerve & obturator nerve
Sacral plexus- L4-S4
Innervates lower back, pelvis, leg & foot
Sciatic nerve is largest nerve of body & goes to leg where it divides into tibial
& common fibular nerves
Cranial nerves
12 pairs come from bottom surface of brain & innervate structures of head, neck & visceral
organs of trunk
2 come from forebrain, other 10 come from midbrain/brain stem
Designated by Roman numerals in order from front to back
I-Olfactory (smell)
Dendrites/cell bodies in mucosa of superior nasal conchae; axons go to
olfactory bulb
II-Optic (sight)
Estimated to be 1.25 million nerve fibers that converge at back of eye
At optic chiasma fibers from medial half of each retina cross to opposite side of
brain but lateral half fibers remain on same side of brain
III-Oculomotor (eyeball movement)
Mostly a motor nerve from midbrain that stimulates muscles of eye
IV-Trochlear
Mixed nerve from midbrain
Innervates superior oblique muscles of eye causing it to rotate
V-Trigeminal
Mixed nerve from pons, midbrain & medulla oblongata
Regulates chewing, sensory responses to touch, temperature & pain in face
Made of ophthalmic nerve (sensory nerve for anterior half of scalp)
maxillary nerve (sensory from lower eyelid to pharynx, teeth/gums)
mandibular nerve (sensory for lower jaw, tongue & lower part of face)
VI-Abducens
Mixed nerve from pons
Innervates lateral rectus of eye
VII-Facial
From pons & emerges near salivary glands
Mixed nerve that controls salivary glands, lacrimal glands & taste buds
VIII-Vestibulocochlear
Other names: auditory, acoustic or statoacoustic nerve
DOES NOT exit cranium but serves structures inside skull
Only sensory- helping with hearing & balance
IX-Glossopharyngeal
Mixed nerve that innervates part of tongue/pharynx
Motor nerve helps stimulate swallowing & secretions of saliva
Sensory nerve helps regulate blood pressure
X-Vagus
Mixed nerve going to visceral organs of thoracic/abdominal cavities
Longest cranial nerve & branches reach pharynx, larynx, respiratory tract, lungs,
heart, esophagus & all of abdominal viscera except large intestine
XI-Accessory
Motor nerve arising from both brain & spinal cord
Innervates skeletal muscles of soft palate, pharynx, larynx as well as trapezius
& sternocleidomastoid
XII-Hypoglossal
Mixed nerve from medulla oblongata
Innervates muscles of tongue that allow for chewing, swallowing, speech
Autonomic Nervous System
Controls involuntary muscle movements (smooth, cardiac & glandular epithelial)
Concerned with maintaining homeostasis within body by increasing or decreasing activity of
organs in response to changing physiological conditions
Made of portions of CNS & PNS
Functions without your conscious control
Autonomic motor pathway involves 2 neurons in motor transmission of impulses
1st has cell body in gray matter of brain or spinal cord; synapses with autonomic ganglion;
1st is a preganglionic neuron from midbrain, hindbrain or spinal cord
nd
2 is postganglionic neuron since it extends from it & synapses with organ
Autonomic ganglia located in head, neck & abdomen
ANS divided into sympathetic/parasympathetic divisions
Sympathetic NS- controls stimulation of internal organs during conditions of high stress or
increased activity; “Fight or Flight” speeds action of heart, dilates blood vessels in
muscles but constricts vessels in skin so to divert blood to muscles & vital organs;
dilates eye pupils for maximum peripheral vision, quiets gastrointestinal tract &
stimulates production of epinephrine (adrenalin) from adrenal glands
Parasympathetic NS- controls internal organs during routine conditions; “rest & digest”
PHYSIOLOGY
Main functions
To provide communication between one body part & another
To interpret physical/chemical changes occurring in/out of body; monitors change
To coordinate/regulate body’s activities
To store information
To integrate impulses
To effect responses
Function properties of neurons
Irritability- ability to respond to stimuli & convert it into impulse
Conductivity- transmission of impulse along a single neuron
Integration- enables CNS to sort out impulses & interpret them so that instruction can then
be carried from brain to muscles
Nerve impulses travel in one direction & is an all-or-none response (responds by sending impulse
all the way down the neuron or not at all) & all action potentials have the same voltage
Threshold stimulus- impulse strong enough to activate neuron
Summation- adding together a series of subthreshold stimuli in quick succession so that total reaches
threshold & initiates impulse
Refractory period- period after initial stimulus when neuron is not sensitive to another stimulus
Nerve impulse- an electrochemical process; travels much slower than electricity; movement of ions
along a nerve fiber resulting in creation of a stimulus
Large myelinated fibers (sensory/motor neurons) conduct impulses 120 meters/sec
Thinner myelinated fibers conduct impulses 10 meters/sec
Unmyelinated fibers conduct impulses 2 meters/sec
Speed is determined by size of neuron & presence of myelin sheath not by intensity of impulse
Response time- amount of time required for an individual to respond voluntarily to a sensory stimulus
(average for visual stimulus is 200-250 milliseconds; for hearing 150-200 milliseconds & for
touch 130-170 milliseconds)
Increase from fatigue, medication & emotional states but ultimately limited by speed at
which impulse travels along neural pathways
Conduction
Movement of impulses from one end of a neuron to the other end of the SAME neuron
Impulse begins at cell’s dendrites & spreads across surface of cell to terminal branches of axon
Once initiated, the impulse is propagated along the cell without depending on a continuing
stimulus & the velocity of the impulse is not dependent on the strength of the stimulus
Resting neuron (not conducting an impulse)
Fluid bathing the outer membrane has more sodium ions than inside the cell & the
inside has more potassium ions than outside the cell (interior is negatively
charged & contains less sodium ions)
Makes the outside of cell positive compared to inside
Nerve fiber is polarized
Sodium & potassium ions are constantly diffusing across the membrane & the Na-K
pump keeps returning them to where they should be
When neuron is stimulated
Membrane becomes depolarized
Sodium ion gates in membrane open wide & let sodium ions through quickly to inside
& potassium moves out
This reverses the polarity of the membrane (inside becomes more positive than outside)
Impulse (wave of depolarization or action potential) moves along neuron as electrons
flow from polarized to depolarized areas
Potassium ions diffuse outward & restores membrane’s original polarity
This cycle continues down the length of the neuron
Repolarization- diffusion of potassium ions out of cell so inside of cell becomes more
negative; this restores original resting membrane potential
Impulse does not decrease as it is being conducted down the length of the cell
Transmission
Passage of impulse from the axon endings of one neuron to the dendrite endings of ANOTHER
neuron
Chemical process that occurs at the synapse (gap that occurs between axon endings of one
neuron & dendrite endings of next)
When impulse arrives at axon ending, calcium ion gates widen to allow calcium ions to flow into
cell
Rise in calcium ions in cell activates enzymes to promote the fusion of neurotransmitter rich
synaptic vesicles with the plasma membrane
Neurotransmitter is released into synaptic cleft from synaptic vesicles
Peripheral NS neurotransmitters- acetylcholine, epinephrine, norepinephrine
Central NS neurotransmitters- glutamate, acetylcholine, dopamine, serotonin
Neurotransmitters must be broken down by enzymes & the pieces reabsorbed by presynaptic
neuron
Two major functions of spinal cord
Two way conducting pathway (sensory impulses from body to brain & motor impulses from
brain to muscles)
Center for reflex activity
Reflex
Involuntary (sometimes unconscious) neural response to a specific sensory stimulus that
threatens the survival of an organism
Receptor is stimulated & impulse is carried to cell body in CNS, axon of sensory neuron
contacts associative neuron to spinal cord, associative neuron contacts motor neuron
which sends impulse down axon to muscle
Brain is NOT used to complete reflex
Can be modified by learned behavior
Reflex arc- contains minimum of one sensory, one associative & one motor neuron with spinal
cord
Spinal reflexes- involve only the spinal cord & spinal nerves
Ex. Knee jerk reflex or postural reflex (head jerk as you drift off to sleep)
Receptor cells sense physical or chemical changes within body or near the body surface
Receptors are associated with dendritic nerve endings of sensory neurons
Sensory neurons become part of dorsal root ganglia of spinal nerve
In gray matter of spinal cord the axons of sensory nerve synapse with dendrite endings of
motor neurons
Motor neurons extend into muscles & axons stimulate muscle to move
Simple spinal reflexes have only two types of fibers- sensory & motor so are called monosynaptic with
a single type of synapse
Other reflexes
Ex. Removing hand from surface of hot object
Receptors stimulated & impulse conducted to gray matter of spinal cord
Impulse transmitted to associative neurons
Associative neurons then transmit impulse to motor neuron
Now brain has chance to override reflex by sending impulses down spinal cord to inhibit
transmission between associative & motor neurons
Gag reflex- occurs when objects touch sides or back of throat
Carotid sinus reflex- restores blood pressure to normal when receptors detect increase in blood
pressure
Some Disorders of Nervous System
My Foot’s Asleep!- nerves are pinched & when pinching stops the nerve signal goes through again;
pins/needles feeling is due to nerve getting the message flowing again; quickest way to get rid
of it is to move around
Ticklishness- when tickled small nerve fibers at skin surface are activated & the tickling impulses travel
slowly; tickling increases pulse, heart rate & blood pressure; it enhances brain alertness, may
also increase production of growth hormones
Headaches- most due to dilated blood vessels in meninges of brain; usually associated with stress,
eyestrain, food allergies, increased blood pressure or fatigue
Migraine- commonly preceded or accompanied by visual impairment & gastrointestinal unrest;
may be triggered by fatigue, food allergy or emotional stress; usually only affects one
side of head
Fainting- brief loss of consciousness due to rapid pooling of blood in lower extremities
Concussion- injury resulting from violent jarring of brain due to forceful blow to head; most common
brain injury; symptoms include headache, drowsiness, lack of concentration, confusion, amnesia
Coma- state of unconsciousness from which patient cannot be aroused; total unresponsiveness to
stimulus for a long period of time
Parkinson’s disease- deterioration of neurons within brain that synthesize dopamine; major cause of
neurological disability in people over 60; causes: medication reaction, illicit drug use, genetics,
brain damage; progressive degeneration & loss of cells in part of the brain stem that produces
dopamine; symptoms include muscle tremors, muscular rigidity, speech defects, jerky hesitant
movements; can be treated orally with L-dopa which brain converts into dopamine
Meningitis- inflammation of meninges caused by bacterial or viral infection; usually affects the pia mater
or arachnoid layer; symptoms include high fever, severe headache, sensory impairment,
paralysis, mental retardation, coma & death; mortality rate varies; bacterial type can be treated
with antibiotics
Alzheimer’s disease- most common cause of dementia; not clinically apparent until after age 65; begins
in middle age & produces progressive mental deterioration; no known cause; symptoms include
loss of memory, verbal/reading skills as well as emotional control, have difficulty making
decisions, changes in mood/behavior; show decrease in the number of cortical neurons;
genetics/environment may play a role
Cerebrovascular accident- stroke or brain attack; clot forms in artery of brain or arteriosclerosis of
cerebral arteries; patients suffer partial paralysis & mental disorders
Cerebral palsy- motor nerve disorder characterized by partial paralysis & lack of muscular coordination;
may affect cerebral cortex, basal nuclei, or cerebellum; most have some degree of mental
retardation as well as partial blindness, deafness & speech problems; usually result from
damage to infant’s brain before, during or immediately after birth
Epilepsy- strong hereditary basis but can be caused by head injuries, tumors or childhood infectious
diseases; refers to 40 different conditions characterized by recurring seizures over extended
periods of time; neurons in brain fire unpredictably & without stimulus; person may periodically
experience seizures ranging from brief loss of contact with reality to severe seizure where
consciousness is lost; almost never affects intelligence & can be effectively treated with drugs
Amnesia
Retrograde amnesia- loss of memories of past events following head injury; memory gap for
20 minutes before event
Anterograde amnesia- unable to store additional memories but can access earlier memories;
the world is new each day to these people
Post-traumatic amnesia- combination of others that develops after head injury
Diptheria- bacterial infection of respiratory tract; bacteria produces toxin that damages Schwann cells &
destroys myelin sheaths; leads to sensory & motor problems that may cause total paralysis;
can affect cardiac muscle
Multiple sclerosis- MS; recurrent demyelination of axons in optic nerve, brain &/or spinal cord;
thought to be an autoimmune disease; impairs nerve impulse conduction; symptoms include
loss of vision, problems with speech/balance, problems with general muscle coordination; more
prevalent in whites than blacks; 1.5 times more common in women; age of first attack usually
30-40; eventually patient is bedridden & death occurs within 7-30 years; no cure but symptoms
can be treated with steroids or interferon
Huntington’s disease- inherited (dominant) disease marked by progressive deterioration of mental
abilities that begins in 40s or 50s; cerebral nuclei show degenerative changes, cause of
deterioration is unknown; no effect treatment; victim’s children have a 50% risk of receiving
gene & developing disease; fatal within 10-20 years; rapid, jerky involuntary movement
Shingles- Herpes zoster virus attacks neurons within dorsal roots of spinal nerves & sensory ganglia of
cranial nerves; reactivation of childhood chickenpox infection; contagious as long as there are
blisters; 10% of adults will get & most after age 50; produces painful but not itchy rash that
eventually heals; can be triggered by stress, infections, sunburn; treated with large doses of
anti-viral drugs
Leprosy- Hansen’s disease; infectious disease caused by bacteria; progresses slowly & symptoms may
not appear for up to 30 years after infection; bacteria invades peripheral nerves producing
sensory loss & motor paralysis; only 5% of exposed will develop symptoms; 2000 cases in US
& 12-20 million worldwide; can be treated successfully with drugs & treated individuals are
not infectious; have discontinued isolation of lepers
Hematoma- pooling of blood outside vessel
Epidural hematoma- forms in epidural space of brain caused by severe blow to side of head,
brain tissue can become distorted/compressed as hematoma grows in size; treatments
include drilling a hole in the skull, suctioning out blood & tying off blood vessel
Subdural hematoma- forms in between dura mater & arachnoid layer; results from fast or
violent rotation of head