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76 Cards in this Set
- Front
- Back
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Nervous system divisions:
based on function |
*somatic: sensory, motor
*autonomic: sympathetic, parasympathetic |
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Nervous system divisions:
based on structure |
*Central Nervous System (CNS)
-encased in bone -cerebrum -brain stem -spinal cord *Peripheral Nervous System (PNS) -includes all parts not encased in cranium or vertebral column |
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Gray matter
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*primarily cell bodies
*ganglion (ganglia) *nucleus (nuclei) |
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White matter
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*primarily axons with myelin covering
-tract -lemniscus -fasciculus -column -peduncle -capsule (bundles of fibers that are carrying information from one location to another) |
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CNS:
Cerebrum |
*Cerebral hemispheres:
-cerebral cortex = surface gray matter -gyrus (mounds) -sulcus (groove) -fissure (deeper groove) -longitudinal fissure: long groove/division between the two lobes of the brain -basal ganglia (within hemispheres) *paired lobes (fig 1-13) -frontal -parietal -temporal -occipital -limbic -insula |
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Cerebrum:
Frontal Lobe Boundaries |
*frontal pole (tip of brain) to central sulcus (large groove from coronal plane)
*lateral sulcus separates it from temporal lobe *cingulate sulcus is the medial boundary *note relationship with olfactory tract and optic nerve (below frontal lobe) |
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Cerebrum:
Frontal Lobe Functional Areas |
*Primary motor cortex (fig 16-12)
-voluntary movement -located in precentral gyrus (gyrus just in front of central sulcus) *Broca's area (fig 16-13) -usually in left hemisphere alone -language output, written and spoken *Prefrontal cortex (corresponding to Broca's area) -personality, insight and foresight -Broca's does verbal communication, prefrontal does nonverbal communication *Motor homunculus (fig 9-24) -precentral gyrus in frontal lobe -distorted body representation where size of body parts indicates size of cortex associated with that part -larger area to hand than lower limbs |
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Cerebrum:
Parietal Lobe Boundaries |
*extends from central sulcus to...
-parieto-occipital sulcus on the medial -line joining parieto-occipital sulcus to preoccipital notch on lateral |
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Cerebrum:
Parietal Lobe Function |
(fig 6-12)
*primary somatosensory cortex -in postcentral gyrus -sensory homunculus -tactile and proprioception -similar to motor, but different areas of emphasis |
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Cerebrum:
Temporal Lobe Boundaries |
*located on lateral side
*extends from lateral sulcus to parietal and occipital lobes |
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Cerebrum:
Temporal Lobe Functions |
*Primary auditory cortex
*Wernicke's area -superior gyrus -usually left lobe -language comprehension (interpretation of language) (area corresponding to Wernicke's in other hemisphere is responsible for interpreting nonverbal communication) **associative areas of brain interpret information** |
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Cerebrum:
Occipital Lobe Boundaries |
*extends from posterior pole to parietal and temporal lobes
*medial surface contains primary visual cortex -calcarine fissure separates: -cuneus gyrus (upper gyrus) -lingual gyrus (lower gyrus) *visual association cortex extends onto lateral surface -surrounds visual cortex and extends to lateral surface |
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Cerebrum:
Occipital Lobe Function |
*visual cortex = SIGHT
*visual association areas = PERCEPTION (visual memory and understanding what is seen) |
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Cerebrum:
Limbic Lobe |
*ON medial aspect between corpus callosum and frontal, parietal, and occipital lobes
*limbic system functiosn in emotional responses and some memory processing (a number of other structures make up the limbic system) |
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Cerebrum:
Insula |
*deep within lateral sulcus
*opercula (lips) of frontal, parietal, and temporal lobes pulled apart |
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Cerebrum:
Diencephalon |
(fig 1-12)
*thalamus *hypothalamus *epithalamus = pineal body (paired, one on each side, except pineal body) |
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Diencephalon:
Thalamus |
*control system: information coming and and out of brain is first relayed and processed in thalamus (relay = synapse)
*paired bodies that contain nuclear groups *integrates information from the body and other CNS structures *some nuclei have reciprocal connections to cerebral cortex (reciprocal = going back to same direction/place) *Lateral Geniculate Nucleus (LGN) -fig 16-2 -located on dorsal aspects of thalamus -termination of the retinal ganglion cell axons (optic nerve terminates here) -visual information is processed -fibers then proceed to visual cortex in occipital lobe LGN = vision MGN = hearing (medial, next to LGN) |
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Diencephalon:
Hypothalamus |
(fig 1-12)
*tissue below thalamus and surrounding third ventricle *optic chiasm is located below (optic chiasm = all visual fibers from left eye and right eye) *significant control over basic survival -reproduction, growth, temperature control -pituitary gland, ANS |
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Diencephalon:
Epithalamus |
*has to do with circadian rhythm (night/day cycle)
*contains pineal gland |
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Cerebrum:
Basal Ganglia |
(fig 1-14)
*many cell bodies make up basal ganglia = gray matter *deep gray matter *located lateral to thalamus *have a role in coordinating and sequencing movement *surrounded by lobes of cerebral hemisphere (**big deal**) *composed of: -caudate nucleus -lenticular nucleus -Putamen and Globus pallidus -subthalamic nucleus -substantia nigra |
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Cerebrum:
Internal Capsule |
(fig 1-4, 16-4)
*white matter *located between lentiform nucleus and caudate nucleus and thalamus *fiber tract connecting: -thalamus and cortex -cortex and thalamus, brainstem, and spinal cord *consists of: -anterior limb -Kneeor genu -posterior limb -corticospinal tract (CST) -descend tract from brain down -role in voluntary movement to muscles -right side of brain controls left side of body (crosses in internal capsule) **#7 of fig 16-4 is optic radiations: off posterior limb, fibers from the LGN carries info from retina and ends in primary visual cortex** |
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Cerebrum:
Fiber Types |
1) Commissures (fig A-2, 16-5)
-fiber bundles joining the cerebral hemispheres -corpus callosum -anterior commissure -posterior commissure (carries pupillary fibers) 2) Projection fibers -either goes down or goes up -connects cerebral hemispheres with lower structures (ie. spinal cord) 3) Association fibers -connect one part of a single hemisphere to another part -stays on same side of brain **commissures - between hemispheres **projections - up and down **association - within hemisphere |
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Central Nervous System:
Brain Stem |
(fig 1-12)
*connects cerebral hemispheres with spinal cord *composed of: -midbrain -pons -medulla |
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Brain Stem:
Midbrain |
*orients body to auditory and visual stimuli
*integrates seeing and hearing with vestibular system *composed of: -Tectum (fig 14-3) -Tegmentum -Cerebral Peduncles (fig 14-1) |
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Midbrain Components
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1) Tectum (fig 14-3)
-just posterior to cerebral aquaduct (canal that contains cerebral spinal fluid and connects ventricles) -contains superior colliculi (associated with vision) and inferior colliculi (associated with hearing) 2) Tegmentum -contains cell bodies of cranial nerves III and IV (moves the eye balls; contains 5 of the 6 extraoculuar muscles) 3) Cerebral Peduncles (fig 14-1) -contains fiber tracts joining cerebral hemispheres and lower CNS -Optic tract (fibers leaving chaism) wraps around peduncles enroute to LGN |
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Brain Stem:
Pons |
*contains nuclei of cranial nerves V, VI, VII, and VIII
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Brain Stem:
Medulla |
*continuous with spinal cord
*outer center for life functions (ie. respiration) *prominences on anterior surface on both sides of midline -pyramids -olives ***brainstem contains important tracts carrying information between brain and body*** |
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CNS:
Cerebellum |
(fig 1-11)
*consists of paired structures -cerebellar hemispheres -cerebellar peduncles (fiber tracts from midbrains, pons and medulla to cerebellum) *plans, coordinates, and adjusts voluntary movements *role in saccadic (looking at one thing and then another) and pursuit (following something) eye movement and associated postural adjustments |
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CNS:
Spinal Cord |
(fig 1-6)
*extends from inferior medulla to lumbar region *has 31 segments with paired spinal nerves from each conducts information between CNS and PSC *some processing occurs within the spinal cord (ie. reflexes) *composed of white matter and gray matter -gray matter: dorsal, lateral and ventral horns -white matter: dorsal, lateral and ventral columns |
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CNS Nutritional Sources
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CNS nutrition is derived from two sources:
1) blood 2) cerebrospinal fluid |
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Ventricles
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(fig 16-1)
*cavities filled with cerebrospinal fluid -lateral ventricle (2): within cerebral hemispheres -third ventricle: surrounded by thalamus and hypothalamus -fourth ventricle: between pons and cerebellum *all are joined by cerebral aquaduct |
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Wiring Basics
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1) "body sense" information:
-pain, temperature, touch, proprioception -comes from environment, through nerves and into brain 2) crosses the midline to cerebral cortex -pain and temperature cross at different levels than touch, which is useful in diagnostic testing 3) Somatosensory cortex in parietal lobe communicates (via association fibers) with motor cortex in frontal lobe 4) fibers descend (via projection fibers) in corticospinal tract and cross **left side of brain gets information from right side of body** **left side of brain controls right side of body** |
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Visual Pathway
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1) Retina
2) Optic Nerve: made of axons and ganglia cells in retina -passes inferior to frontal lobe 3) Optic Chiasm: all the visual fibers from both eyes -below hypothalamus and third ventricle 4) Optic Tract -courses around cerebral peduncles of midbrain 5) LGN (lateral geniculate nucleus) -dorsal lateral thalamus 6) Optic Radiations -courses through parietal and temporal lobes 7) Visual Cortex -located in occipital lobe -provides information to temporal and parietal lobes (associated visual cortex/area) |
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Neuro-Imaging: A Primer
Why bother? |
*improves communications
*understand reports *study anatomy and structural relationships *direct studies of neuro sections not often done *double check conclusions *understand limitations |
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Types of Imaging
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*Plain films (standard x-ray)
*CT/CAT (computed axial tomography) *MRI (Magnetic Resonance Imaging) *Angiography (being replaced by MRI due to slight dangers) |
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Terminology:
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"bright signal" something that is bright on a scan
CT: hyper/hypo density MR: hyper/hypo intensity "enhancement" means a contrast agent was infused and caused a bright signal |
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Plain Films:
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*fast and inexpensive
*set up as though looking at a patient *good for bone and metal/dense objects *air shows as black (rays go right through and penetrates film, thus making it black) *air where you don't expect to see it around orbit may indicate a fracture *air tends to become round in soft tissue |
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Contrast Enhancement
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*based on different attenuation of x-ray beam by various tissues
-increase density, atomic number and electron per gram = increased attenuation -more attenuation = lighter image *"softer" areas may be visualized by use of contrast media (ie. barium for GI studies to increase density) |
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"Alleged" Utility of Plain Films
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*R/O (removal of) foreign bodies before MRI
*acute sinusitis *characteristic bony lesions *cervical spine fractures *gross fractures on facial trauma |
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Questions About Plain Films
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*abnormalities on skull radiographs don't correlate well with intracranial abnormalities
-rarely used in ED, except to... -R/O foregin body -document child abuse *x-ray of paranasal sinuses largely supplanted by coronal CT |
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CAT/CT Uses
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*good for bone/calcium
-fractures *good for blood -especially recent trauma -acute sub-dural, sub-arachnoid hemorrhage *good for meningiomas (tumor of meninges) *superior for fat and orbital muscle (important for optometrist) |
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CT Parameters
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*Uses radiation
-avoid with children and preggers *available in emergency rooms -fast, no danger from metallic objects *relatively low cost *different window widths used (can manipulate contrast between tissues) *no direct sagittal views possible (newer technology is able to piece pictures together to give sagittal view) |
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Orbital Imaging
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*Must specify cuts for centers that do not specialize in orbital studies
-need coronal cuts - finely spaced (otherwise you get horizontal cuts 5cm apart and miss whole thing) |
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Use of Contrast in CT
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*iodine based (makes blood vessels opacified)
-avoid if allergy to iodine or shellfish *cross blood-brain barrier only if disruption *metabolized in kidneys -avoid if abnormal kidney function -extra care with diabetics **CT can be used for a noninvasive autopsy** |
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MRI Uses
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*good for anatomy studies
-soft tissue *uses magnetic field affecting hydrogen atom alignment -no radiation -followed by radiofrequency pule (realign atoms) *axial, coronal and sagittal sections available |
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CT vs MRI
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*MR is Premiere Means for Intracranial Pathology Evaluation because:
-radiation exposure with CT -increased soft tissue contrast with MR *CT relies on different attenuation of x-ray beams *MR relies on response of tissue to applied magnetic field |
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Sagittal Sections
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*sagittal sections are particularly useful for viewing:
-pituitary gland -corpus callosum -cervico-medullary junction -pineal gland |
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MRI Parameters
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*nor normally used in emergency room (too time consuming and danger of metal)
*several options of weighting and enhancing images *some weighted images may be used with contrast |
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TI Weighted Images
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"Time 1" - time to realign nuclei
*good for viewing anatomy *high H2O content are dark (ypointense) -vitreous and CSF *can be used with gadolinium for contrast -images compared with and without contrast to see in enhancement |
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Gadolinium
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*not iodine based
-less potential for allergic reaction *IV administration *abnormalities demonstrate areas of enhancement -alters magnetic field (higher signal intensity = brighter) -crosses disrupted blood-brain barrier *use for suspected mass, inflammation, infiltration |
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T2 Weighted Images
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"Time 2" - time for nuclei to realign
*used for pathology and edema *not used with contrast! *...because CSF and vitreous are already bright |
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Relative Advantages
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CT:
*1st day ischemic stroke *1st day cerebral or cerebellar hem *initial head injury *initial brain abcess *with ferrous metal *orbital bone fracture MRI: *infarcts > 1 day *cavernous sinus *brainstem/post fossa *demyelinating disease *chiasmal lesions *intracranial tumors |
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CT Disadvantages
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*exposure to radiation
*lower resolution *poorer visualization of more intracranial tissue -especially when surrounded by bone or other beam-hardening artifact |
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MRI Disadvantages
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*longer scan time
*50% more expensive *bone or calcium lesions not imaged well *metallic bodies (pacemakers, cochlear implants, stents) can't be done *claustrophobia *obesity *iron oxide in tattoos interferes OPEN MRI: *useful for obese and claustrophobic patients *questions if images are as refined *no sagittal view |
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Other Tests Using MRI
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MRI FLAIR:
"fluid attenuation inversion recovery" *like T2, but water is attenuated -CSF and vitreous are dark -better contrast range *good pathology, especially near CSF *very good for MS plaques *sagittal FLAIR MRI DWI *diffusion weighted imaging *good for acute infarcts *gradient echo MR also useful in stroke MRI STIR: *T2-like image with fat attenuated -easier to see orbital muscles |
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Orbital Studies
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*must specify if orbital study required
*need many fine cuts - coronal *if MRI, must do fat suppression, T2 or STIR -gadolinium usually needed |
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Angiography
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*at the moment, still gold standard
*can visualize small aneurysms and A-V (atrial-venous) malformations |
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MRA
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*allows imaging of both arteries and veins
*gadolinium is NOT required, although newer techniques are using it to enhance images *cannot detect aneurysms smaller than 3mm *vessel flow void is used for image *vessels normally dark due to rapid fluid movement *MRV useful for venous sinus thrombosis *patients with papilledema or headaches |
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CTA
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*IV contrast is injected
*high-speed spiral CT scanning and computer-assisted generation of images of large to medium-sized arteries *the patient is moved at a constant rate through the scanning field during a single breath-hold *exams are quick, less radiation and contrast are used, and patient with aneurysm clips or implanted stimulators can be scanned |
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CTA Disadvantages
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*sensitivity of CTA in aneurysm detection may be limited by surgical clips or clots from recent SAH
*aneurysms of PICA and cavernous sinus are more difficult to image *cannot resolve small vessels *patients may have adverse reactions to iodinated contrast |
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Ordering Studies
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*type of study
*body part *specific sequences required *areas to direct special attenuation *clinical finding suggesting localization *release films to patient? |
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Ventricular Network
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*four connected ventricles
-2 lateral, 1 third, 1 fourth *produces cerebrospinal fluid (CSF) in choroid plexus *brain floats in CSF *reference for structures in imaging |
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Cerebrospinal Fluid (CSF)
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*clear and colorless
*regulates extracellular environment *supplies water, amino acids, glucose and ions to extracellular fluid *protects CNS (shock absorber) *removes metabolites from brain |
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Choroid Plexus and Formation of CSF
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*network of capillaries embedded in connective tissue
-3 layers of cells: capillary wall, connevtive tissue, epithelium *formed by filtration, active transport (similar to plasma) |
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CSF Route
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*circulates in ventricles
*enters subarachnoid space *absorbed into venous circulation |
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Lateral Ventricles
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*a pair of C-shaped "horns"
-anterior (frontal lobe) -posterior (occipital lobe) -inferior (temporal lobe) *extends into each hemispheric lobe *below is thalamus *above is corpus callosum (connects two sides of brain) *outside wall is caudate nucleus *each side of lateral ventricles connects through third ventricle |
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Third Ventricle
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*in midline of diencephalon
*walls are thalamus and hypothalamus *connects to fourth ventricle through midbrain canal -cerebral aqueduct or Sylvian aqueduct |
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Fourth Ventricle
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*anteriorly: space between pons and medulla
*posteriorly: cerebellum *inferiorly continuous with central canal of spinal cord *drains into subarachnoid space via: -two lateral foramina (Luschka) -coats brain -think L-L -midline opening (Magendie) -flushes down -think M-M |
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CSF Fun Facts
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*adult produces about 1 pint daily (clinical implications)
*production: 0.5mL/min *volume: approx. 90mL in subarachnoid space, 30mL in lumbar sac *it takes.... -1-2 hours to basal cisterns -3-4 hours to sylvian fissure -10-12 hours to spread over cerebral subarachnoid -24 hours to clear into superior sagittal sinus |
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White Matter Compression
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causes hydrocephalus in child
-measure head circumference Symptoms: -vomitting -failure to thrive -delay of developmental milestones -irritability -"sunset eye sign": see sclera above irises, eye lids lifted |
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Causes of Hydrocephalus
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*excessive production of CSF
-tumors of choroidal plexus (rare) *blockage of CSF circulation *poor secretion of CSF into venous sinuses -scarring from meningitis or hemorrhage *structural issue (ie. Danny Walker cyst) *bleeding *infection *neoplasm *vascular *trauma |
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Treatment of Hydrocephalus
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Shunt: create a route from brain to gut to drain excess CSF
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CSF Leaving the Brainstem...
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*CSF continues into subarachnoid space
*through arachnoid villi *through dura to sagittal sinus (unidirectional flow) **normally no CSF in central spinal canal |
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CSF Blockage: Clinical Implications
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Hydrocephalus:
-dilation of ventricles, particularly lateral -increased intracranial pressure (ICP) -checked by CSF tap pressure -loss of spontaneous venous pulsation in eye Pseudotumor Cerebri: *aka "benign" Idiopathic Intracranial Hypertension -likely an meningeal absorption defect -slow, no dilation of ventricles |
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Lumbar Puncture/Spinal Tap
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*pt in lateral recumbent position
*syringe placed into lumbar cistern below spinal cord LS-5 *CSF exists results in movement on pressure gague -3-way stopcock and manometer attached to hub of needle -CSF flows into manometer until level steady -normal values<200 (250 for overweight) |
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Symptoms of Hydrocephalus
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*headache
*difficulty with vertical gaze *Paranaud's Syndrome (Sylvian Aquaduct Syndome) *problems with gait, balance and incontinent |
