Block 1: CNS Overview Flashcards
What is the function of frontal lobe, in general?
Executive area; responsible for initiating motor/behavioral responses to information collected
What is the function of the precentral gyrus and anterior paracentral lobule?
Primary motor cortex – controls fine, highly skilled “voluntary” movements
What is the function of the prefrontal cortex: superior, middle, and inferior gyri?
Attention, motivation, planning, abstraction or problem solving, planned (cognition) behavior, subjective judgment, social skills, emotional behavior/personality,
“working memory” or short-term memory (intermediate memory)
What is the function of the superior frontal gyrus?
Premotor area (motor programming or indirect motor movement control); supplementary motor cortex
What is the function of the supplementary motor area?
Motor movement, initiation/planning, cortical micturition control center
What is the function of the middle frontal gyrus?
Frontal eye fields (voluntary eye movements); part of premotor cortex
What is the function of the inferior frontal gyrus?
Three portions: orbital, triangular, and opercular
Critical for motor aspects of speech
What is the function and location of Broca’s area?
Fxn: Formulation of speech
Lxn: Left inferior frontal gyrus
What is the function of the right inferior frontal gyrus?
Language expression (prosody of speech)
What is the function of the postcentral gyrus and the posterior paracentral lobule?
Primary somatosensory cortex
What is the function of the superior parietal lobule and the precuneus?
Somatosensory association cortex
What is the function of the inferior parietal lobule?
Multimodal association cortex (integration)
What is the function of the posterior parietal lobule on the left hemisphere?
Analytical skills
What is the function of the posterior parietal lobule on the right hemisphere?
Visuospatial orientation
What is the general function of the parietal/occipital lobe?
“Where” lobe; shape, form, texture, color, moving or not moving – connects prefrontal cortex and temporal/occipital cortex to tell events that are occurring
What is the function of the cuneus gyrus?
Visual input from lower visual fields
What is the function of the lingual gyrus?
Visual input from upper visual fields
What is the function of the lateral occipital gyri?
Involuntary cortical eye fields (scanning movements)
What is the general function of the temporal/occipital lobe?
“What” lobe; connects to prefrontal cortex, parietal/occipital cortex, orbitofrontal cortex, hippocampus (memory) and amygdala (emotion) to tell what is occurring
What is the function of the transverse temporal gyri and what is another name for this section of cerebrum?
Fxn: Primary auditory cortex (hearing)
AKA: Heschl’s convolutions
What is the function of the superior temporal gyrus and what is another name for the area located in the posterior superior temporal gyrus?
Fxn: Auditory association; language comprehension (Wernicke’s area)
What is the function of the middle temporal gyrus?
Language and semantic (generic – meaning, basic-concepts) memory
What is the function of the inferior temporal gyrus?
Visual association cortex
What is the function of the parahippocampal formation?
Learning/memory consolidation (long-term memory)
What is the function of the cuneus?
Herniates through the tentorial notch with increased intracranial pressure; covers amygdala (emotion of fear)
What is the function of the anterior portion of the limbic system?
Emotional behavior and homeostasis
What is the function of the posterior portion of the limbic system?
Cortical processes of learning and memory consolidation (declarative)
What is another name for the “limbic lobe”?
Cingulate gyrus
What is the function of the rostral parahippocampal gyrus, uncus, temporal pole, limen insulae?
Primary olfactory cortex
What is the general function of the insula?
Integrates visceral input (olfactory, gustatory, pain and thermal information)
Define agnosia.
Inability to understand or recognize the significance of sensory stimuli even though the sensory pathways and primary sensory cortex are intact
What deficits do patients with tactile agnosia experience?
It is impossible to correlate surface texture, shape, size, and weight of an object and compare it to a previous experience; occurs with lesions involving the parietal association cortex (left or right)
What deficits do patients with visual agnosia experience?
The inability to recognize objects that cannot be attributed to defect of visual acuity or to intellectual impairment; cannot relate present to past visual experiences – cannot appreciate significance
- Occurs with lesions involving the visual association cortex (left or right)
What deficits do patients with auditory agnosia experience?
Patient with unimpaired hearing fails to recognize or appreciate a meaning with a perceived sound; occurs with lesions involving the auditory association cortex
What deficits do patients with anoagnosia experience?
A loss of disease awareness; occurs with lesions involving the parietal lobule (right)
Define apraxia. What cerebral hemisphere is this condition associated with?
It is the inability to carry out a motor action in response to verbal or written request even though patient does not have paresis/paralysis, sensory abnormality, comprehension deficit, or disturbance of coordination (ataxia).
- Dominant hemisphere (left)
Define aphasia.
It is a defect in language processing caused by brain lesions; develops as a consequence of lesions in the dominant cerebral hemisphere and most cases are caused by stroke, head injury, cerebral tumors, or degenerative dementia such as Alzheimer disease
What is expressive aphasia, aka Broca’s aphasia?
problem in formulation of ‘articulated’ speech
What is receptive aphasia, aka Wernicke’s aphasia?
It is a form of auditory agnosia in which the patient fails to recognize or comprehend the meaning of known words, aka ‘word deafness’
What structures do neural crest cells give rise to in the human body?
Spinal and autonomic ganglia, Schwann cells, meninges, adrenal medulla, pseudounipolar cells of the DRG, and melanocytes
Describe the development of the pituitary gland.
The pituitary gland has two different parts: anterior and posterior. The anterior portion is derived from oral ectoderm that forms from Rathke’s pouch and becomes the glandular portion of the pituitary gland. The posterior portion is derived from neural ectoderm which originated as the infundibulum (an outgrowth of the hypothalamus). The posterior lobe is considered the neural portion of the pituitary gland. Both parts fused and sit within the sella turcica which is made up of fused sphenoid bone.
What cell types make up the choroid plexus?
Choroidal epithelium and pia mater
What are the different components of a neurologic exam?
- Mental status, cranial nerve exam, motor and sensory exams, reflexes, coordination, and gait & station checks
What is checked during the mental status portion of the neurological exam?
o Level of consciousness: likely to determine without formal testing
o Orientation: time, person, place
o Attention/concentration: spell “world” or name months of the year backwards, serial 7s
o Calculation: getting change when buying something
o Language: naming, repetition, comprehension, fluency
o Speech: quality, clarity
o Memory: state 3 words; ask immediately afterward and after distraction
o Fund of knowledge: ask questions
How does one check cranial nerves I - IV and VI?
CN I: pass odors under nose with pt’s eyes closed
CN II: visual acuity, pupils; fundoscopic exam
CN III: extraocular movements and pupils
CN IV: extraocular movements (SO muscle)
CN VI: extraocular movements (LR muscle)
How does one check CN V?
Test facial sensation, corneal response, muscles of mastication
- Facial: use a cotton ball, pin, or tuning fork to compare side-to-side activity level
- Corneal: brush cornea to see if patient is a coma blinks
- Mastication: bite down, open jaw
How does one test CN VIII?
- Vestibular branch: test for dizziness/vertigo, abnormal nystagmus, or coma
- Cochlear branch:
• See if patient can hear fine finger rubbing or watch ticking
• Weber test – place tuning fork on patients frontal bone and see if hearing is better on one side; normal if sound is equal
• Rinne test – place tuning fork on mastoid, then in front of ear and have patient say which was louder; normal is air > bone
How does one test CN X?
palate elevation (not uvula), gag (usually only in coma), swallow, listen for horseness or “breathiness”
How does one test CN XI?
Have patient turn head against resistance at chin; head to right tests left SCM/CN XI
How does one test CN XII?
Tests motor function to the tongue.
- Listen for slurring with lingual sounds (la-la-la)
- Observe at rest for fasciculations
- Observe tongue protrusion and movement for deviation and slowness – if deviates, it will be to the weak side/CN XII
What do you look for in the motor exam portion of the neurological exam?
- Bulk: observe for atrophy
- Tone: observe passive movement about a joint
- Strength: compare side-to-side, proximal to distal
What is a positive arm drift test and what does it test?
It tests upper motor neurons for weakness, which is commonly seen in stroke victims.
Positive results include: fingers flex, arm pronates and drifts downward
During the sensory exam, what senses do you test and how?
o Pain and temperature: use a pinprick or cool tuning fork applied to different limbs; tests spinothalamic tract (small fibers)
o Vibration and proprioception: apply tuning fork to distal joint (often great toe); tests dorsal columns (large fibers)
o Light touch: use cotton ball to touch limbs
What is the Romberg test?
Patient stands up, feet together, close eyes – if patient moves then this test is positive (usually occurs in people with neuropathy)
What condition might a patient have if he or she is hypo/hyperreflexive?
- Hyporeflexive: radiculopathy, neuropathy (typically seen in diabetic patients)
- Hyperreflexive: brain lesion, spinal cord lesion (typically seen in stroke victims)
What part of the brain is being tested during the coordination portion of the neurological exam and what tests are used?
Tests the cerebellum.
Tests include:
o Finger nose finger test
o Heel knee shin test (heel of one foot traces line from knee up the leg of opposite limb)
o Rapid alternating movements (clap different hand surfaces together; tests frontal lobe)
o Fine finger and toe tapping (if slow, there is a problem; test frontal lobe and cortical functions)
What is the function of the basal ganglia?
- coordinates choice of mutually exclusive skeletal muscle actions
- operational learning
o links to limbic system to associate emotions, goals, motivations with movements - dysfunction leads to movement disorders
What is the function of the thalamus?
- Interpret/modulate sensory input to cortex
- Change input to cortex based on arousal, sleep, vigilance, etc.
- Role in attention to parts or features of sensory environment
When modulated, this causes chronic pain.
What are the functions of the midbrain?
Vertical eye movements, pupil control, posture & locomotion, non-rapid eye movement, temperature regulation, level of arousal
What are the functions of the pons?
conjugate horizontal eye movements, posture, rapid eye movements, facial expressions
What are the functions of the medulla?
autonomic functions (respiratory, cardiac, vomiting, vasomotor); blood pressure, breathing, GI motility, ingestion, equilibrium
Define consciousness.
o Has two components:
- Wakefulness: open eyes, motor arousal; level of consciousness
- Awareness: experience of thoughts, memories and emotions
If a patient has a stroke located within the anterior cerebral artery, what deficits can be expected?
Contralateral paralysis and sensory deficits in lower body and extremity.
If a patient has a stroke located within the middle cerebral artery, what deficits can be expected?
Contralateral paralysis and sensory deficits in head, arm and upper body.
If a patient has a stroke located within the posterior cerebral artery, what deficits can be expected?
Blindness in the contralateral visual field.
Define a linear skull fracture.
straight crack, usually not serious; most common fracture
Define a depressed fracture.
bone displaced inward, comminuted (in pieces), can damage the brain
Define a diastatic fracture.
occurs across the suture line, suture widens, usually seen in children
Define a basal fracture.
caused due to more force, results in distant hematomas (not at site of impact – typically seen behind the ear), CSF drainage; clinical sign of fracture = battle sign (mastoid hematoma), raccoon eyes (symmetric bruising around both eyes)
What is a coup injury and what is a contrecoup injury?
o Coup injury (contusion at point of contact)
o Contrecoup injury (contusion on opposite side)
What is a diffuse axonal injury?
Injury of axons in deep white matter of brain usually due to twisting/shearing the axons from rotational force applied to the brain. Typically occurs in boxing or “shaken baby” syndrome.
What artery is most commonly damaged in patients with an epidural hematoma? What does a CT scan of this injury look like?
- Middle meningeal artery (branch of external carotid artery)
- Smooth contours since blood is contained behind the dura
What vein(s) is/are most commonly damaged in patients with an subdural hematoma? What does a CT scan of this injury look like?
- Dipolic and emissary veins
- Ragged contours since the blood is able to flow on top of, but throughout the gyri and sulci.
What most commonly causes subarachnoid hematomas in patients?
- Contusions, ruptured berry aneurysms (often at branch points within the Circle of Willis)
What happens to neurons after an acute injury?
The neurons become “red neurons” which means they are dying. The red color results due to the production of different proteins which causes them to stain differently.
What happens to create axonal spheroids in neurons?
Collection of different proteins within the axon that stain red; not specific for a certain type of injury
What happens in axonal reaction to neurons?
Occurs in the cell body when its axon is cut and causes the cell body to swell
What disease/infection is related to the following inclusion body in neurons: Cowdry body?
Herpes
What disease/infection is related to the following inclusion body in neurons: Negri body?
Rabies
What disease/infection is related to the following inclusion body in neurons: neurofibrillary tangles?
Alzheimer disease
What disease/infection is related to the following inclusion body in neurons: Lewy body?
Parkinson disease
What causes vasogenic cerebral edema and how is it treated?
- Cause: fluid accumulates between the endothelial cells which causes increased vascular permeability
- Tx: steroids (dexamethosone), osmotic diuretic (Mannitol)
What causes cytotoxic cerebral edema and how is it treated?
- Cause: fluid accumulates within the endothelial cells; increased intracellular fluid as a result of cell membrane injury
- Tx: resistant to any known medical treatment
What type of hydrocephalus is commonly misdiagnosed as Alzheimer disease? What are the clinical manifestations of this type of hydrocephalus? What is a possible treatment?
- Normal pressure hydrocephalus
- Patients present with gait disturbance (slow, unsteady, wide-base), urinary incontinence, and dementia. However, these symptoms may be reversible!!!
- Tx goal: reduce fluid volume and pressure
- Tx: furosemide (diuretic; Na K 2 Cl exchanger), acetazolamide (Carbonic Anhydrase Inhibitor)
What causes subfalcine (cingulate) herniation to occur and what are some side effects of this herniation?
- Caused by expansion of one cortical hemisphere is displaced under the falx cerebri and impinges on the cingulate gyrus.
- Results in compression of anterior cerebral artery branches which then manifests as weakness of limbs, aphasia, etc. (Frontal lobe)
What causes transtentorial (uncinate) herniation to occur and what are some side effects of this herniation?
- The temporal lobe is compressed against the tentorium cerebelli which affects:
o CN III - fixed, dilated pupil; impaired ocular movements
o Brainstem - duret hemorrhages; impaired consciousness
o Posterior cerebral artery - ischemia in primary visual cortex
o Contralateral cerebral peduncle - hemiparesis (watch for false localizing sign due to decussation of motor tracts in the peduncles)
What causes tonsillar herniation to occur and what are some side effects of this herniation?
ICP causes the displacement of the cerebellar tonsils through the foramen magnum which presses on the medulla which compresses vital respiratory and cardiac centers, etc.
- This is LIFE THREATENING!!!!
What proteins make up a tight junction found within the BBB?
- Claudin
- Occludin
- JAM (junctional adhesion molecule)
The following drugs work on different transporters found within the BBB to decrease CSF production. What transporters/enzymes do the following work on:
- Acetazolamide
- Furosemide
- Ouabain
- Acetazolamide: carbonic anhydrase, CA
- Furosemide: Na-K 2 Cl exchanger
- Ouabain: Na-K ATPase
Name and explain what the two novel drug transport systems are involving the BBB.
- Transcytosis: molecules bind to transporters and are transported through vesicles by endocytosis and released via exocytosis into the brain
- Immune Cell Migration (diapedesis): movement of whole cells through the endothelial cells
• Has potential for brain tumor chemotherapy
What is the glymphatic system and how does convective bulk flow act in its mechanism?
The glymphatic system involves interstitial solute and fluid clearance from the brain.
Mechanism:
o CSF enters the brain along para-arterial routes, whereas ISF is cleared from the brain along paravenous routes.
o Convective bulk ISF flow between these influx and clearance routes is facilitated by AQP4-dependent astroglial water flux and drives the clearance of interstitial solutes and fluid from the brain parenchyma.
o From here, solutes and fluid may be dispersed into the subarachnoid CSF, enter the bloodstream across the postcapillary vasculature, or follow the walls of the draining veins to reach the cervical lymphatics.
Glutamate is a(n) ______________ NT that has both ionotropic and metabotropic receptors. Name those receptors. Hint, there are three each.
Stimulatory
Ionotropic: AMPA, NMDA, Kainic acid
Metabotropic: I, II, & III
GABA is a(n) _______________ NT that has both ionotropic and metabotropic receptors. Name those receptors. Hint, there is one each.
Inhibitory
Ionotropic: GABAa (Cl- channel)
Metabotropic: GABAb
Both cause hyperpolarization of the cell membrane
Acetylcholine is both an inhibitory and stimulatory NT depending on which receptor it binds to. ACh has both ionotropic and metabotropic receptors. Name those receptors. Hint, there is one each.
Ionotropic: nicotinic (Na channel; stimulatory NT)
Metabotropic: muscarinic (reduce cAMP, increase Ca, increase K permeability; inhibitory NT)
Dopamine is a(n) ____________ NT. What are the DA receptors and what type of neuron do they act to suppress?
Inhibitory
D1 - acts to enhance GABA release, increase cAMP
D2 - suppress cAMP, inhibits GABA release
GABA neuron
Serotonin (5HT) interacts with both ionotropic and metabotropic receptors and has two different actions. What are the receptors and the associated actions of serotonin?
Ionotropic: 5HT3 - serotonin is excitatory
Metabotropic: 5HT2 - serotonin is inhibitory
- Antagonists of 5HT2 improve schizophrenia and bipolar disorder; SSRIs create an anti-depressant effect
Norepinephrine interacts with three different receptors. What are the three receptors and their associated functions?
- Alpha1: increase K conductance - inhibitory, causes hyperpolarization
- Alpha2, beta: attention and arousal
Opioids are a(n) _____________ NT and suppress pain by interacting with what receptor. What is the associated result of this interaction?
Inhibitory
Suppress pain by interacting with a µ receptor which decreases Ca and cAMP levels
What NTs are associated with treating the following conditions: motor stimulation, motor inhibition, motor stimulation via inhibition of inhibition, memory, psychoses, and pain.
o Motor stimulation: glutamate
o Motor inhibition: GABA, glycine, norepinephrine
o Motor stimulation via inhibition of inhibition: dopamine
o Memory: ACh
o Psychoses: dopamine D2 receptor, 5HT2 receptor
o Pain: opioids
How does excitotoxic cell death occur?
Typically, excitatory NTs are cleared from the synaptic cleft after their release; however, in excitotoxic cell death these excitatory NTs (such as glutamate) remain within the synapse and opens its receptors (AMPA, NMDA) resulting in a sharp increase in Ca2+. This increase in Ca2+ activates the principal death-signaling pathways of necrosis and apoptosis.
Mild elevation of Ca2+ activates apoptosis, profound elevation of Ca2+ activates necrosis.
Which bones in the skull have a neural crest origin of mesenchyme?
Frontal, ethmoid, nasal, lacrimal, zygomatic, mandible, sphenoid, squamous portion of temporal, styloid, hyoid
Which bones in the skull have a paraxial mesoderm origin of mesenchyme?
Parietal, occipital, petrous portion of temporal, mastoid portion of temporal
What bones have endochondral formation in the neurocranium and viscerocranium?
Neurocranium: ethmoid, sphenoid, occipital base, petrous portion of temporal, mastoid portion of temporal
Viscerocranium: malleus, incus, stapes, hyoid, styloid process of temporal
What bones have intramembranous formation in the neurocranium and viscerocranium?
Neurocranium: flat bones - parietal, frontal, squamous portion of temporal
Viscerocranium: premaxilla, maxilla, zygomatic, squamous portion of temporal, mandible
Define craniosynostosis.
Craniosynostosis = premature closure of one or more sutures that produces a misshapen skull.
Define brachycephaly.
Brachycephaly = fusion of coronal suture produces a shortened front-to-back diameter of skull (“flat-head”) that is wide
Define oxycephaly/turricephaly/acrocephaly.
Oxycephaly, turricephaly or acrocephaly = fusion of coronal & lambdoidal sutures produces a “tower skull”.
Define plagiocephaly.
Plagiocephaly = fusion of coronal & lambdoidal sutures unilaterally produces an asymmetrical skull.
Define scaphocephaly.
Scaphocephaly = fusion of the sagittal suture produces a long front-to-back diameter skull.
Define microcephaly.
Microcephaly = small head due to a brain that fails to grow.
May be caused by a NTD, genetic factors, obstructed blood supply to the brain, prenatal exposure to alcohol or drugs, or maternal rubella or chicken pox. Severity and quality of life vary greatly.
Define cranioschisis.
Cranioschisis = skull defect through which the meninges and/or brain herniate (NTD)
Severity ranges:
• Meningocele – meninges only
• Meningoencephalocele – meninges plus brain
• Meningohydroencephalocele – meninges, brain, and ventricles
Define apert, crouzon, and pfeiffer syndromes. All of these are caused by a mutation in ___________.
o Apert Syndrome - autosomal dominant genetic disorder characterized by craniosynostosis and other congenital abnormalities (i.e. syndactyly of hands/feet, mental retardation)
o Crouzon syndrome – closely related to Apert syndrome but lacks syndactyly
o Pfeiffer syndrome – eyes bulge out (due to lack of cranial space), great toes and thumbs are wide and deviated
Mutation in fibroblast growth factor receptor (FGFR) 1 and 2.
