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72 Cards in this Set

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What are the neuronal substrates of consciousness?
1. Cortical Content
- the sum of all mental (cortical) activities
- There is not a single site but rather this involves all cortical areas
- Includes memories, perception, attention, language, ability to calculate, etc
2. Arousal system
- This switches the cortex to make content available
- Anatomically this system includes widespread cortical projections from parts of the reticular formation and from the thalamic nuclei
What are the three components in sensory perception?
1. The specific sensory system
2. The association system
3. The non-specific system
Describe the components and functions of cranial nerve XI (accessory nerve)
1. Branchial motor – cranial root (SVE); Innervates muscles of larynx and pharynx.
2. Branchial motor – spinal root (SVE); Innervates the trapezius and sternocleido-mastoid muscles.
Describe the components and functions of cranial nerve X (vagus nerve)
1. Branchial motor (SVE); Supplies the voluntary muscles of the pharynx and most of the larynx, as well as one extrinsic muscle of the tongue.
2. Visceral motor (GVE); Parasympathetic innervation of the smooth muscle and glands of the pharynx, larynx, and viscera of the thorax and abdomen.
3. Visceral sensory (GVA); Provides visceral sensory info. from the larynx, esophagus, trachea, and abdominal and thoracic viscera, as well as the stretch receptors of the aortic arch and chemoreceptors of the aortic bodies.
4. General sensory (GSA); Provides general sensory information from the skin of the back of the ear and external auditory meatus, parts of the external surface of the tympanic membrane, and the pharynx.
5. Special sensory (SA); A very minor component of CN X provides taste sensation from the epiglottic region.
Describe the components and functions of cranial nerve IX (Glossopharyngeal nerve)
1. Branchial motor (SVE); Supplies the stylopharyngeus muscle.
2. Visceral motor (GVE); Parasympathetic innervation of the smooth muscle and glands of the pharynx, larynx, and viscera of the thorax and abdomen.
3. Visceral sensory (GVA); Visceral sensory information from the carotid sinus and body
4. General sensory (GSA);Provides general sensory information from the skin of the external ear, internal surface of the tympanic membrane, upper pharynx, and the posterior 1/3 of the tongue.
5. Special sensory (SVA); Provides taste sensation from the posterior 1/3 of the tongue.
What are the structural causes of unconsciousness?
mnemonic TIPS
- Trauma/Tumour/Temperature,
- Infection,
- Psychogenic,
- Subdural hematoma/Subarachnoid hemorrhage/Stroke/Seizure.
How do tumors cause impaired consciousness?
1) mass effect from the tumour, edema, or hemorrhage;
2) strategic location;
3) meningeal spread;
4) complication of therapy;
5) seizures
What is general anesthesia?
- Altered physical state characterized by the following components
1. Hypnosis (loc)
2. Analgesia
3. Amnesia**
4. Immobility**
5. Inhibition of autonomic
6. Sensory reflexes
7. Muscle relaxation
When is anesthesia induced?
When a critical concentration reaches the brain. For gases this is expressed as the partial pressure of brain (Pbr)
The rate of uptake of an inhaled anesthesia can be assessed by what ratio?
The ratio of alveolar anesthetic concentration (Fa) to the inspired anesthetic concentration (Fi) over time
or Fa/Fi
What determines the the inhaled anesthetic concentration over time?
1. the solubility of the agent in the blood
2. the partial pressure difference between alveoli and pulmonary venous blood
3. Alveolar ventilation
What are the theories for anesthetic MOA?
1. Lipid theory
2. Protein theory
How do inhaled anesthetics suppress excitable tissues?
1. Facilitation of inhibition
- Increase GABA-A receptor-mediated transmission
- increase background (leak) K+ conductance
2. Inhibition of excitation
- decreased glutamate and ACh receptor mediated transmission
What does MAC stand for?
Minimal Alveolar Concentration
What is MAC?
Minimal Alveolar Concentration of an inhaled anesthetic in the alveoli at 1 atm that prevents movement in response to a painful stimulus in 50% of patients
- means of expressing the dose of an inhaled anesthetic
- for inhaled anesthetics, MAC represents the ED50
Approximately 1.2 MAC will prevent movement in 95% of patients
Factors that decrease an agent's MAC
- Increased age
- Decreased temp
- Pregnancy
- Opioids
- Other anesthetics & CNS drugs
What is the Meyer-Overton Rule?
The more lipid soluble an anesthetic agent, the more potent it is
What are the effects of inhaled anesthetics on the CNS?
1. Decrease in cerebral metabolic rate
2. Cerebral vasodilation - bld flow increases
What are the effects of inhaled anesthetics on the CVS?
1. Decrease in arterial BP - reduced cardiac output, lower peripheral resistance
2. Ventricular arrhythmias
What are the effects of inhaled anesthetics on the Resp system?
1. Respiratory depression - increased tidal volume
2. Decreased airway resistance
What are the effects of inhaled anesthetics on the MSK?
Muscle relaxation
What is meant by "balanced anesthesia"?
Combination of agents to maximize advantages and minimize adverse effects
Features of the Anterior nucleus of the thalamus
Part of the papez circuit of emotion of the limbic system
What role does the mediodorsal nucleus of the thalamus play?
plays a role in the expression of affect, emotion and behavior (limbic function)
What happens when the mediodorsal nucleus of the thalamus is destroyed?
Memory loss occurs (Wernicke-Korsakoff syndrome)
What role does the pulvinar of the thalamus play?
The pulvinar plays a role in the integration of visual, auditory and somesthetic input.
What happens when the pulvinar nucleus of the thalamus is destroyed?
Can result in sensory dysphasia (a speech disorder in which there is an impairment of speech and of comprehension of speech)
The blood supply of the thalamus is done by what three arteries?
1. P Comm A
2. PCA
3. Anterior choroidal artery
What does consciousness consist of?
1. Cortical content
2. Arousal system
What evidence is there pertaining to the sensory pathways?
1. Bilateral lesions of intralaminar nuclei
- lethargic, somnolent
2. PET studies
- indicate localized increases in blood flow (neuronal activity) in midbrain RF and IL thalamic nuclei during attention demanding tasks
3. Stimulation of midbrain RF
- gives rise to prolonged enhancement of thalamic and cortical activity
- associated with aroused EEG pattern
What is the major input of the prefrontal cortex?
The major input is from the DM thalamic nucleus.
What is sleep?
Can be thought of as a rhythmic modulation of the ARAS thalamocortical arousal system
Where is the sleep generator?
In the brainstem
What is THIOPENTAL?
barbiturate derivative
What is the clinical use of THIOPENTAL?
Rapid induction of hypnosis with NO (that's right none) analgesic properties
What is the MOA of THIOPENTAL?
Facilitation of inhibitory neurotransmission via GABA-A receptors
What are the pharmokinetics of THIOPENTAL?
Rapid induction <20sec
When tissues are saturated it is the elimination rate and not redistribution that determines time of emergence
What are the adverse effects of THIOPENTAL?
hypo-tension
Rep depression
Histamine release
Arterial occlusion is possible
What is the clinical use of PROPOFOL?
Useful for sedation, induction and maintenance of anesthesia
What is the MOA of PROPOFOL?
Facilitation of inhibitory neurotransmission via GABA-A receptors
What are the adverse effects of PROPOFOL?
Pronounced hypotension (greater than thiopental)
Respiratory depression
injection pain
Potential for sepsis
What are the properties of KETAMINE?
PCP derivative which produces a state of dissociative anesthesia (i.e. patients appear conscious but are unable to respond to sensory input
What is the clinical use of ketamine?
Induction of anesthesia in trauma or shock
Analgesia in burn patients
i.m induction in children
What is the MOA of KETAMINE?
Anatagonist at NMDA receptors
What are the causes of acute seizures in infancy and childhood?
- Prenatal / Birth injury
- Inborn error of metabolism
- Congenital malformation
What are the causes of acute seizures in childhood and adolescence?
- Idiopathic
- genetic syndrome
- CNS Infxn
- Trauma
What are the causes of acute seizures in young adults?
- Head trauma
- Drug intoxification and withdrawal
What are the causes of acute seizures in older adults?
- Stroke
- Brain tumor
- Acute metabolic disturbances
- Neurodegenerative
What are the basic mechanisms underlying seizures?
The clinical manifestation of an abnormal and excessive excitation and synchronization of a population of cortical neurons
What are the cellular mechanisms of seizure generation?
1. Too much excitation
- Ionic: inward Na+, Ca++ currents
- NT: Glu, Asp
2. Too little inhibition
- Ionic: Inward Cl-; Outward K+ currents
- NT: GABA
What is an anti-epileptic drug?
- A drug which decreases the frequency and / or severity of seizures in people with epilepsy
- Treats the Sx of seizures, not the underlying condition
- Goal: maximize quality of life by minimizing seizures and adverse drug effects
What is the MOA for Phenytoin and carbamazepine?
Block the voltage dependent sodium channels at high firing frequencies
What is the MOA for barbiturates (as an AED)?
- Prolong GABA-mediate chloride channel openings
- Some blockade of voltage dependent sodium channels
What is the MOA for Benzodiazepines?
Increase frequency of GABA-mediated chloride channel openings
What is the MOA for ethosuximide?
- Blocks low threshold, "transient" (T-type) calcium channels in thalamic neurons
What is the MOA for Valproate?
- May enhance GABA transmission in specific circuits
- Blocks voltage-dependent sodium channels
What is the MOA for Gabapentin?
- Increases neuronal GABA concentration
_ Enhances GABA mediated inhibition
What is the MOA for Lamotrigine?
- Blocks voltage dependent sodium channels at high firing frequencies
- May interfere with pathologic glutamate release
What is the MOA for topiramate?
Few SE / Multiple MOA / one of the better Rx
- Blocks voltage dependent sodium channels at high firing frequencies
- Increases frequency at which GABA opens Cl- channels
Antagonizes glutamate action at AMPA / kainate receptor subtype
What is the MOA for Levetiracetum?
- Attached to specific binding site
- reduces high voltage activated Ca++ currents
- Reverses inhibition of GABA and glycine gated currents
What is the MOA for oxcabazepine?
- Blocks voltage dependent sodium channels at high firing frequencies
- Exerts effect on K+ channels
What AEDs have shown efficacy for absence seizures?
- Ethosuximide
- Valproate
describe gliomas
- comprise the largest group of primary intracranial tumors
- Consist of astrocytoma, oligodendroglioma, ependymoma and mixed glioma
70% are supratentorial
30% supratentoral
Give the most common locations of Gliomas
70% are supratentorial
30% are infratentorial
What are the most common CNS tumors in children?
medullobalstoma
astrocytoma
ependymoma
craniopharyngioma
glioblastoma
What two categories of astrocytomas are there?
1. Diffuse (astrocytomas, oligodendroglioma and mixed oligo-astrocytoma)
2. Circumscribed (Pilocytic)
What are the molecular / diagnostic tests used to influence treatment decisions for gliomas?
1. The analysis of chromsomes 1p and 19q in oligodendroglial tumors show better prognosis and greater response to tx
2. MGMT has been shown to be associated with longer survival times for glioblastoma patients treated with alkylating agents
Describe the features of meningiomas
more common in women
tend to intracranial (nasopharynx or periortibal)
85% are benign, 10% atypical and 5% are malignant
What is PNET?
Primative neuroectodermal tumor is a term applied to tumors that show characteristics of "small blue cell" occuring in different locations
What are the most common sites for a schwannoma?
the most common intracranial locations are 8th (vestibulocochlear) followed by 5th (Trigeminal) cranial nerves.
Describe the features of haemangiopericytomas
make up 1 to 5% of tumors within the meninges
occur within meninges
Aggressive, highly recurrent
occur in 40s and 50s most common in men
Where are the most common origins of metastatic cancer to the CNS
respiratory system
breast
GI
GU