Nervous System Flashcards
List 3 factors that, when altered, may change arousal. Give one example of how each could be altered.
Structure: through infections, neoplasms, trauma, etc.
Metabolism: through hypoxia, drugs, electrolyte disturbances
Psychogenic: uncommon, through psychiatric disorders
What is the Glasgow coma scale used for, and what 3 responses does it measure?
Widely accepted “Glasgow coma scale” – a method for assessing level of consciousness in a person with brain injury: numbered scores are given to responses of eye opening, verbal utterances and motor responses.
- What does the pattern of breathing depend upon when consciousness decreases and what information can this yield?
When consciousness decreases, lower brain stem centers respond only to levels of PCO2 . The pattern of breathing can yield information as to the location of brain damage.
- What is the normal oculomotor response in a comatose patient? What are two abnormal oculomotor responses?
may be purposeful, absent or inappropriate (e.g., associated with decreased consciousness are several reflexes: grasping, sucking.)
- Describe the 5 outcomes of alterations in arousal.
Brain death – no recovery possible and brain cannot maintain internal homeostasis
Cerebral death – irreversible coma. Brain stem may continue to maintain homeostasis, but the individual will never be able to respond in any significant way to the environment.
Persistent vegetative state – complete unawareness of self or surrounding environment. Sleep-wake cycles are present, brain stem reflexes are intact, but there is bowel and bladder incontinence.
Minimally conscious state – individuals may follow simple commands, manipulate objects, gesture, have intelligible speech.
Locked-in syndrome – complete paralysis of voluntary muscles with the exception of eye movement. Individual is fully conscious with intact cognitive function, but cannot communicate through speech or body movements
- What are 3 properties involved in awareness?
Selective attention – ability to select specific information to be processed (youtube video)
Memory – the ability to store and retrieve info
Executive attention deficits – ability to maintain sustained attention and remember instructions
- Define awareness in the context of neurological function.
Includes all cognitive functions (awareness of self and environment, moods, reasoning, judgement)
- Differentiate between a seizure and a convulsion.
Sudden temporary change in motor, sensory, autonomic or psychic clinical manifestations and a temporary altered level of arousal.
Convulsion – jerky, contract/relax movement associated with some seizures
Results from a sudden, explosive, disorderly discharge of cerebral neurons
Generally caused by cerebral lesions, biochemical disorder, cerebral trauma and epilepsy (which can result from many causes, including fever, brain tumors, genetic predispositions, etc.)
- Define agnosia, dysphasia, aphasia, acute confusional state, and dementia.
Agnosia – failure to recognize the form/nature of objects; usually only affects one sense (e.g., can recognize a safety pin by touching it, but not when looking at it). Caused by any damage to a specific part of the brain.
Dysphasia – understanding (receptive) and use (expressive) of symbols (written or verbal) is disturbed or lost (e.g., cannot find words, or uses words, but meaningless). Caused by dysfunction in left cerebral hemisphere (stroke, cancer, trauma, etc.)
(Aphasia = more severe form of dysphasia = inability to communicate (often used interchangeably with dysphasia))
Acute confusional states – highly distractible, unable to concentrate on incoming sensory information (e.g., delirium, hallucinations, seizures). Secondary to drug intoxication, nervous system disease, trauma, surgery, withdrawal from drug, etc.
Dementia - progressive failure of many cerebral functions, including orienting, memory, language, judgment and decision making. Because of declining intellectual ability, is accompanied by behavioural alterations. Caused by neuron degeneration, atherosclerosis, trauma, infection, etc.
- What is cerebral hemodynamics, and what determines its rate?
Cerebral blood flow is normally maintained at a rate that matches local metabolic needs of the brain.
Alterations in cerebral blood flow may be related to 3 injury states:
Inadequate cerebral perfusion
Normal cerebral perfusion with an elevated intracranial pressure
Excessive cerebral blood volume
- What does IICP stand for?
- What can cause IICP?
- What 3 things can be adjusted in order to compensate for changes in ICP? In what order are these adjusted, if needed?
Increased Intercranial Pressure
May result from anything that takes up volume in the brain, e.g., a tumour, edema, excess CSF or hemorrhage.
To adjust for increased pressure, there must be a reduction in some other cranial content. This can include blood volume, CSF volume, tissue volume.
The brain adjusts initially through loss of CSF, as it is most easily decreased in response to increased intracranial pressure.
If this does not remedy pressure, cerebral blood volume and flow are altered.
- Describe the 4 stages of intracranial hypertension.
Stage 1: Vasoconstriction and external compression of the venous system occur in order to decrease the ICP (may be asymptomatic).
Stage 2: When continuing swelling exceeds this compensatory mechanism, oxygenation is compromised (confusion, restlessness, drowsiness), and systemic vasoconstriction occurs to increase systemic blood pressure in order to overcome decreased flow in the brain.
Stage 3: With continued swelling, when ICP begins to equal arterial pressure, cerebral perfusion pressure falls, and hypoxia and hypercapnia of brain tissue occur (rapid deterioration: decreased level of arousal, small, sluggish pupils). At this point, all compensatory mechanisms have been used, so there can now be a dramatic rise in ICP over a very short period of time.
Stage 4: Brain tissue shifts (herniates) from the compartment of greater pressure to a compartment of lesser pressure. This increases pressure in the lower pressure compartment, as well, impairing its blood supply. This increases ICP markedly to where it equals systolic arterial pressure, at which point cerebral blood flow ceases
- Describe cerebral edema (definition, causes, effects)
An increase in the fluid content of brain tissue.
Occurs after trauma, infection, hemorrhage, tumour, ischemia, infarct or hypoxia.
Distorts blood vessels, displaces brain tissues, causes herniation.
What three events can lead to cerebral edema?
increased permeability of BBB (plasma proteins leak out of capillaries, drawing water to them = increased water content of tissue. Occurs mainly in the white matter – easily separated fibers)
Toxins cause failure of transport mechanism of cells = more sodium inside cell = more water inside cell. Occurs mainly in the gray matter.
Obstruction of circulation of CSF in ventricles = fluid leaks into surrounding brain tissue (usually seen in children)
- What is hydrocephalus and what two events can cause this? Give an example of each event.
Excess fluid in ventricles, subarachnoid space, or both
Caused by too high production of CSF (e.g., tumour in choroid plexus), obstructed flow through ventricles (e.g., aqueduct stenosis - more in children), too low reabsorption of CSF (interference with arachnoid villi - more in adults)
Usually develops slowly over time, but can occur rapidly as a result of brain injury (presents with signs of rapidly developing IICP)
