Week 6.1 Flashcards
Why is ammonia used to test CN I?
because it is a chemical irritant, doesn’t rely on olfaction to be noxious, and therefore serves as an excellent control
What are the afferent and efferent innervations for the corneal reflex?
- afferent: CN V
- efferent: CN VII
If both corneal reflexes are slow, it indicates what?
- ipsilateral CN V damage
- or bilateral CN VII damage
What is the Weber test and which is the Rinne yes?
- Weber: fork is held at the vertex of the head
- Rinne: fork is held on the mastoid process
The gag reflex is a test of which cranial nerve?
CN IX
How can you test the vagus nerve?
- listen for hoarseness
- test swallow
Tongue deviation is a sign of damage to what cranial nerve?
hypoglossal
If there is damage to the hypoglossal nerve, the tongue will deviate to which side?
the ipsilateral
What is the key difference between a penetrating head injury caused by a knife or bullet?
the bullet has a higher velocity and doubling velocity quadruples tissue damage
What are the five kinds of primary brain injury?
- concussion
- diffuse axonal injury
- cranial nerve injury
- contusion
- laceration
What parts of the brain are most affected by the shearing stresses of angular acceleration?
- high brainstem
- grey-white junction
What causes a person to lose consciousness when they experience head trauma?
fibers form the RAS are disrupted by the shearing stress of angular acceleration
Angular acceleration is a key feature of which kinds of primary brain injury?
concussion and diffuse axonal injury
What is the difference between a concussion and diffuse axonal injury?
- both involve angular acceleration and shearing stress
- if the axons are stretched but don’t tear, that’s a concussion
- if the axons tear, that’s a diffuse axonal injury
How do we define concussion?
as a reversible traumatic paralysis of nervous function induced by biomechanics forces and defined by any change in neurologic functioning
What are the two most common changes in neurologic functioning associated with concussion?
retrograde or anterograde amnesia
The severity of head injury and likelihood of long-term sequelae following concussion are correlated with what?
- duration of LOC
- presence of amnesia
What symptoms are likely to persist longest after a concussion?
- headache
- difficulty concentrating
What are some physiologic changes that often occur at the time of a concussion?
- LOC
- loss of body tone
- transient arrest of respiration
- bradycardia and hypotension
- concussive convulsion
Diffuse axonal injury primarily affects which brain regions?
- midbrain
- diencephalon
- corona radiata
- gray-white junction
Which cranial nerves are most susceptible to injury?
CN I, VII, VIII
Cranial nerve injury is most often associated with what sort of trauma/injury?
basilar skull fractures
CN VII injury is most strongly associated with what sort of basilar fracture?
one involving the transverse petrous
CN VII injury is most strongly associated with what sort of basilar fracture?
one involving the petrous pyramid
CN XII injury is most strongly associated with what sort of basilar fracture?
one involving the hypoglossal canal
Which ocular motor nerve is most susceptible to cranial nerve injury?
CN IV because it is thin and has a long course
The most severe sort of brain trauma is what?
contusion
Which parts of the brain are most commonly affected by contusion?
those that contact the rough anterior fossa and petrous pyramid
What are six possible secondary brain injuries?
- edema
- CSF disturbances
- bleeding
- herniation
- seizures
- infection
What is the Monroe-Kellie Doctrine?
the idea that there are three compartments in the cranium and the sum of these volumes is constant
What is considered normal intracranial pressure?
15 cm H2O
How do we calculate cerebral perfusion pressure?
CPP = MAP - ICP
What is the elastance of the cranium?
the idea that the cranium has lots of reserve volume and initial increases in volume are met by only small changes in pressure
What is considered normal cerebral blood flow?
50 cc/100g/min
How is cerebral blood flow auto-regulated?
- changes in BP elicit changes in arteriolar diameter
- changes in pCO2 elicit changes in arteriolar diameter
Cerebral arterioles auto-dilate in response to what two things?
- diminishing BP
- increasing pCO2
How can we decrease ICP in a patient using just blood gas?
hyperventilate the patient to reduce pCO2 and constrict arterioles
TBI is usually followed by what type of edema?
cytotoxic
Edema is typically seen in what time period following TBI?
24-72 hours
Which kind of intracranial bleed is best tolerated?
epidural
Subdural hematomas have a mortality rate of what?
30-90 percent
Subdural hematomas are the result of damage to which vessels?
bridging veins
Epidural hematomas are most commonly the result of damage to which vessels?
the middle meningeal artery following a pterion fracture
In which populations are the incidence of epidural hematomas very low?
infants and the elderly
What are the signs and symptoms of chronic subdural hematoma?
- headache
- progressive alteration in mental status
- focal neurologic signs
Subarachnoid hemorrhage is due to rupture of which vessels?
pial vessels
Traumatic subarachnoid hemorrhages are usually located where?
in the basilar cisterns
Traumatic subarachnoid hemorrhage has what time course?
a rapid one, minutes to hours
How can you tell central herniation syndrome from lateral herniation syndrome?
- central: bilaterally mid-size, non-reactive pupils
- lateral: unilaterally dilated, non-reactive pupil
What is the difference between communicating and non-communicating hydrocephalus?
communicating involves a disruption of CSF flow somewhere outside the brain or ventricular system
What is the primary symptom of CSF leak?
headache
The primary complication of CSF leak is what?
infection
What is a tension pneumocephalus?
a complication of CSF leak in which air is trapped in the cranium
How are post-traumatic seizures treated?
with acute prophylactic anti-seizure medications for no longer than one week
What is a subdural empyema?
a collection of pus in the subdural space
What three abilities are assessed by the Glasgow coma scale?
- best eye response
- best verbal response
- best motor response
We begin monitoring someone’s ICP directly when what is true about their Glasgow coma score?
it falls below eight
Treatment of TBI relies on what three goals?
- prevent infection
- treat seizures
- control ICP
How can we pharmacologically reduce ICP in a patient?
osmotic diuresis with mannitol
What is external ventricular drainage?
an intraventricular catheter that drains CSF and monitors ICP
What is mannitol?
a hyper osmotic saline solution
What is the ecological perspective on learning?
the consideration of how behavior and learning function for survival
What is behaviorism?
the attempt to understand behavior in terms of relationships between observable stimuli and observable responses
What is the only example of one-trial learning?
food aversion
What is operant condition?
a process whereby the consequences of a response increase or decrease the likelihood that the response will occur again
What is Thorndike’s Law of Effect?
responses that produce a satisfying effect become more likely to occur in that same situation while responses that produce a discomforting effect become less likely
What is the difference between positive and negative reinforcement?
positive means to add some reinforcement while negative means to remove something as reinforcement
What is the difference between reinforcement an punishment?
reinforcement is used to increase the response while punishment is used to decrease the response
What is the most effective reinforcement schedule?
variable interval
What is a fixed ratio reinforcement schedule?
reinforcement every nth response
What is the partial reinforcement effect?
the idea that resistance to extinction is greater following acquisition where some, but not all, response are reinforced
What kind of reinforcement schedule is most effective in the first stages of training?
continuous
What is “shaping” in the context of learning?
the reinforcement of successive steps toward an end goal behavior
The opposite of generalization in conditioning is what?
discrimination
What is an “extinction burst”?
the phenomenon whereby a behavior will increase just before it tapers off
What is a good real life example of operant conditioning?
avoidance of trauma-related cues by PTSD patients
Avoidance of trauma-related cues by PTSD patients is an example of (positive/negative) (reinforcement/punishment).
negative reinforcement (diminished anxiety)