*Apex- Brain Flashcards
Match each glial cell with its physiologic function:
Oligodendrocytes
Microglia
ependymal cells
Astrocytes
Phagocytosis
CSF production
Metabolic support to neurons
Increase neuronal conduction velocity
Oligodendrocytes
>increase neuronal conduction velocity
Microglia: Phagocytosis
ependymal cells: CSF production
Astrocytes: Metabolic support to neurons
What type of glial cells form the myelin sheath in the CNS?
Which cells form the myelin sheath in peripheral nerves?
Oligodendrocytes -CNS
*Schwann cells -PNS
What is a neuron and what is its primary role?
It’s the functional unit of the nervous system and it’s primary role is to receive and send information
What’s a collection of nerve cell bodies in the CNS called?
a nucleus
What kind of cells act like nerve glue to support neuronal function?
Glial cells: astrocytes, ependymal cells, oligodendrocytes, and microglia
Most brain tumors arise from what kind of cells?
glial cells
What part of the neuron forms the grey matter vs white matter
Cell bodies - gray
Axons - white (myelinated)
What type of neurons make up most of the CNS neurons?
Multipolar
Where are pseudounipolar nerves found? (2)
dorsal root ganglion
cranial ganglion
Where are bipolar neurons found (2)?
Retina & Ear
(crazy people see shit and hear shit, eyes and ears)
Match each brain lobe with its function:
Parietal
Temporal
Occipital
Frontal
Motor cortex
Vision
Sensation
Audition
Parietal - sensation
Temporal - auditory
Occipital- vision
Frontal - motor cortex
The brain can be divided into what 4 areas?
- Cerebral hemispheres
- Diencephalon
- Brainstem
- Cerebellum
The cerebral hemispheres contain (4)
Diencephalon (2)
Brainstem (4)
CH: cerebral cortex, hippocampus, amygdala, basal ganglia (cerebral cortex + limbic system)
D: thalamus and hypothalamus
BS: midbrain, pons, medulla, RAS
What does the corpus callosum do?
connects the 2 cerebral hemispheres
What lobe contains the motor cortex?
Frontal
What lobe contains the somatic sensory cortex
Parietal
(PARIETAL = SENSORY)
Which lobe contains the speech centers?
Temporal
Wernicke’s vs Broca’s area functions
Wernicke’s = understanding speech (Receptive aphasia)
Broca’s = motor control of speech (Expressive aphasia)
Wernicke’s vs Broca’s location?
Wernicke’s = temporal lobe
Broca’s = frontal (think motor control) - but it’s connected to Wernicke’s area via neural pathways.
What is responsible for fine motor control?
The basal ganglia
What is responsible for memory and learning?
Hippocampus
What is responsible for emotions, appetite, responses to pain and stressors?
Amygdala
What is the primary neurohumoral organ?
I have no idea what that means but the hypothalamus
What part of the brainstem has auditory and visual tracts?
Midbrain
Which part of the brainstem is responsible for autonomic integration
PONS & Medulla
What controls consciousness, arousal, and sleep?
(defective in your brain)
RAS
Match each part of the cerebellum with the function:
Archicerebellum
Paleocerebellum
Neocerebellum
- Regulates muscle tone
- maintains equilibrium
- coordinates voluntary muscle movement
Archicerebellum
>Regulates muscle tone
“need muscle tone to build architecture”
Paleocerebellum
>maintains equilibrium
“Dinosaurs maintain equilibrium”
Neocerebellum
>coordinates voluntary muscle movement
“new muscle movement”
Which cranial nerve is MOST likely to be compressed by a pituitary tumor?
CN2 - optic nerve
What cranial nerve is associated with Tic doulourex and what does it do?
trigeminal nerve (CN5) -generates excruciating neuropathic pain in the face
Bells palsy results from injury to which facial nerve? What does it result in?
CN 7 (Facial)
-ipsilateral facial paralysis
Parasympathetic output is carried by which cranial nerves?
3, 7, 9, 10
(think not 2 bc 2 is CNS but next one)
Mnemonic for cranial nerve names
On Occasion, Our Trusty Truck Acts Funny, Very Good Vehicle Any How
Mnemonic for cranial nerve functions
Some Say Marry Money But My Brother Says Bad Business to Marry Money
CN for somatic sensation and taste to posterior 1/3 of the tongue
Glossopharyngeal (9)
(think 1/3rd bc it’s such a small part all the way in the back)
CN for swallowing
Vagus
CN for pupil constriction
CN3 - occulomotor
CN for sensation to the face
Trigeminal (5)
V1- ophthalmic
CN for sensation to the anterior 2/3 of the tongue
what about taste to the anterior 2/3 of the tongue
CN 5- trigeminal
V2 - Maxillary
(think tongue in cheek, 2 structures, V2) - i SENSE that my tongue is in my cheek
(taste on anterior 2/3 is facial nerve-7)
>think Monica and her 7 orgasms, tasting things
CN for facial movement except mastication (what is the one for mastication)
facial movement = CN 7- facial
mastication = Trigeminal - CN 5, V3 (mandibular) - 3 M’s:
Mandibular, Muscles, Mastication
CN for hearing and balance
8- Vestibulocochlear
Which cranial nerve is responsible for eye:
adduction
abduction
adduction: CN3 (medial rectus)
abduction: CN 6 (lateral rectus)
Which cranial nerve is responsible for eye:
intorsion (depression)
extorsion (elevation)
intorsion (staying IN bc your Depressed) - CN 4 (superior oblique)
extorsion (extroverts are always elevated) - CN 3 (inferior oblique)
-introverts are superior and extroverts are inferior ; introverts let the extroverts go first so CN 3 = elevation followed by CN 4- depression
Which CN is responsible for infraduction of the eye and what is that
looking down and out - CN3 (inferior rectus)
Which cranial nerve?
3- Occulomotor
Inferior oblique
Superior rectus
Medial rectus
Inferior rectus
Which CN?
4- Trochlear (superior oblique)
(What you would be doing with your eyes to look at trochars in your stomach/superior obliques)
Which CN?
CN 6 - Abducens
Lateral rectus
(looking out the corner of your eyes for the devil - 6)
Match the corresponding items:
Site of CSF resorption
Pathway between 3rd and 4th ventricle
Site of CSF production
Pathway between lateral and 3rd ventricle
Choroid Plexus
Arachnoid villi
Foramen of Monro
Aqueduct of Sylvius
Site of CSF production - Choroid plexus
Pathway between lateral and 3rd ventricle - Foramen of Monro
Pathway between 3rd and 4th ventricle - Aqueduct of Sylvius (So Sly, it just sneaks between 3 and 4)
Site of CSF resorption- Arachnoid villi
Total CSF volume
150mls
Rate of CSF production and what is it produced by?
30mls/hr
produced by the choroid plexus
What separates the CSF from the plasma?
The BBB
T/F - the BBB is present at the chemoreceptor trigger zone
False - it’s not - which explains how some drugs that can’t pass through the BBB can elicit N/V
Specific Gravity of CSF
1.002 - 1.009
CSF presure
5-15mmHg
Mnemonic for CSF flow in the brain
Love My 3 Sums 4 Life, Man!
Lateral ventricles
Monro (Foramen)
3rd ventricle
Sylvius (aqueduct)
4th ventricle
Luschka
Magendie
Where is the arachnoid villi and what is it the site for?
CSF absorption / Superior sagittal sinus
What is hydrocephalus?
the excessive amount of CSF accumulation in the brain that can increase ICP
2 types of hydrocephalus. Which is more common?
- Obstructive - an obstruction to CSF flow in the ventricular system (most common)
- Communicating hydrocephalus (decreased absorption by the arachnoid villi - ie. ICH; or overproduction of CSF (very rare)
Treatment options for hydrocephalus (3)
- Placing a catheter in the cerebral ventricles to drain CSF (ventric drain)
- Placing a ventriculoatrial shunt (brain to heart)
- Placing a ventriculoperitoneal shunt (brain to belly)
Normal ICP
5-15 mmHg
(AKA: CSF Pressure)
What 5 Places is the BBB NOT Present?
CCPPH
Chemoreceptor trigger zone (why you get nauseous centrally)
Choroid plexus
Posterior Pitutiary (puts shit directly into blood)
Pineal gland
Hypothalamus
Identify areas on the cerebral blood flow graph:
PaCO2
Cerebral Perfusion Pressure
Intracranial Pressure
PaO2
A- ICP
B- PaCO2
C- CPP
D- PaO2
Cerebral blood flow is coupled to CMRO2 - what does that mean?
It means the greater the need for oxygen, the more blood flow there will be to satisfy that need
5 Things CMRO2 is decreased by
4 Things CMRO2 is increased by
Decreased by:
Hypothermia
Halogenated anesthetics
Propofol
Etomidate
Barbituates
Increased by:
Hyperthermia
Seizures
Ketamine
Nitrous oxide
Cerebral blood flow autoregulates between a CPP of what or MAP of what?
CPP of 50-150mmHg
MAP of 60-160
(remember CPP = MAP - ICP or CVP)
Whats the risk when CPP is < 50 or above >150
<50 - risk of hypoperfusion
>150 - risk of cerebral edema and hemorrhage
What does it mean when it’s said there is a linear relationship between PaCO2 and CBF?
For every 1mmHg increase in PaCO2, CBF will increase by 1-2ml/100g brain tissue/min
& Vice versa
(increase PaCO2 = increase CBF (to get rid of the toxic byproducts)
For every 1mmHg decrease in PaCO2, CBF will (increase/decrease) by _____ml/100g/brain tissue/min
decrease by 1-2ml
Max cerebral vasoconstriction occurs at what PaCO2?
CO2 -25mmHg
Maximum cerebral vasodilation occurs at an PaCO2 of what?
CO2 of 80-100mmHg
A PaO2 below what level causes cerebral vasodilation and increases CBF?
PaO2 below 50-60mmHg
CPP =
MAP - ICP
-a high venous pressure (going into the IVC >RA reduces the amount of venous drainage that can drain into the SVC>RA which results in increased cerebral volume, creating back pressure on the brain that reduces arterial/venous pressure gradient [not as much arterial blood can drop of nutrients with the venous pressure being high])
CBF =
CPP/CVR
CMRO2 =
3.8ml/O2/100g brain tissue/min
oxygen usage in the brain is 60% for _______ and 40% for _______
60% for electrical activity
40% for cellular integrity
*even if the brain is electrically silenced, it still has to consume oxygen to support cellular integrity
CMRO2 decreased ___% for every 1 degree C decrease in temp
7%
EEG suppression occurs between what temps?
18-20 degrees C
Hyperthermia beyond ____degrees C denatures proteins and destroys neurons and CBF decreases
> 42 degrees C
at temps > 42 degees C, does CBF increase or decrease
decrease, gives up. no hope .
How do Resp Acidosis/Alkalosis and Metabolic Acidosis/Alkalosis affect CBF?
Resp Acidosis > decreased pH (increased CO2) > decreases CVR (cerebral vasodilation) > increased CBF
Resp alkalosis > increased pH (decreased CO2) > increased CVR (cerebral vasoconstriction) > decreased CBF
*Metabolic acidosis does not directly affect CBF This is because H+ ions in the blood do not pass through the BBB
…..mmmk.
To ensure a normal CPP of 50mmHg, Map must be between what, assuming an ICP in the normal range of 5-15mmHg.
What if someone has elevated ICP? do you need MAPs lower or higher to maintain CPP
MAP 55-65mmHg to ensure CPP of 50
*If ICP is elevated, a higher MAP is required to maintain CPP
(think extra pressure in the cranial vault is going to compress the vasculature in the brain and you will need a higher MAP to maintain perfusion to the vessels in the brain)
What is cerebral steal?
When there are ischemic or atherosclerotic regions in the brain, the vessels that supply those regions maximally dilate to try and increase o2 to those areas.
Situations that cause cerebral vasodilation (hypercapnia, hypoventilation, vasodilators) - vasodilate the vessels that supply the healthy brain tissue and “steal” flow from ischemic areas.
Cerebral vasodilation or constriction:
hypercapnia
vasodilation
Cerebral vasodilation or constriction:
hypoventilation
vasodilation (hypoventilation = increased PaCO2)
What is “inverse steal” or the “Robinhood effect” the concept of?
The concept of using hyperventilation (decreasing CO2) to constrict the cerebral vessels that supply healthy brain tissue.
- Thought process being that the flow will redistribute to the ischemic regions - but the vessels supplying those regions are already maximally dilated and hypocapnia as not been shown to provide clinical benefit.
- It can actually cause harm from cerebral ischemia (not enough CBF) - oxyhemoglobin dissociation curve shifts to the left - left/love - less O2 released to the tissues (body thinks low co2, low metabolic state, don’t need as much o2 to go to cells that aren’t working hard)
Cerebral vasodilation or constriction:
Hyperventillation
cerebral vasoconstriction (decreased CO2)
CBF is unaffected by PaO2 when the PaO2 level is above what?
>60 PaO2 - CBF unaffected
<50-60 - vasodilation, increased CBF
4 conditions that impair venous drainage from the head (increasing CBV and requiring a higher map to maintain CPP)
- Jugular compression from improper head positioning (head flexion in the sitting position)
- Increased intrathoracic pressure second to coughing or PEEP
- Vena cava thrombosis
- Vena cava syndrome
What are the 5 determinants of cerebral blood flow
- CMRO2 (3.8)
- CPP ( MAP - ICP, 50-150)
- PaCO2 (<25, 80-100)
- PaO2 (<50-60, >60)
- Venous pressure
A fixed and dilated pupil suggests herniation of the:
A. cingulate gyrus
B. Choroid plexus
C. Temporal uncus
D. Cerebellar Tonsils
C. Temporal uncus
Intracranial HTN is defined as
ICP > 20mmHg
What does the Monro-Kellie hypothesis (or doctrine) have to deal with?
The pressure-volume equilibrium between the brain, blood, and CSF within constraints of the cranium.
-Increase in one of these components must be contracted with a decrease in one or both of the others
If not, then ICP within the cranium will rise .
What is Cushing’s triad and what is it a sign of?
It’s a sign of intracranial hypertension and it consists of:
Hypertension
Bradycardia
& Irregular respirations
What’s the most common site of transtentorial herniation? What does it lead to?
At the temporal uncus
-herniation applies pressure to the oculomotor nerve (3), making it ischemic. Manifests as fixed and dilated
What’s the gold standard for ICP measurement?
What are 2 other ways to measure it?
Gold standard = intraventricular catheter
- subdural bolt
- catheter placed over the convexity of the cerebral cortex (mmmk)
ICP measurement is indicated with a GCS of what
= 7
s/s intracranial HTN (other than cushing’s triad) - 7
- Headache
- N/V
- Papilledema (swelling of optic nerve- CN2)
- Pupil dilation and non-reactivity to light (CN3, temporal uncal)
- Focal neurologic deficit
- Seizure
- Coma
What is the condition where ICP increases for no apparent reason (2 names)
Pseudotumor cerebri
Idiopathic intracranial HTN
What’s the deal with hyperventilating a patient with increased ICP?
Mild hyperventilation (PaCO2 30-35) constricts cerebral vessels > decreased CBV > decreased ICP
T/F Decadron shrinks brain tumors
False, it reduces swelling around the tumor
Phenylephrine …. good or bad for increased ICP patients
Good- increased ICP leads to decreased CPP, need to increase MAP to maintain CPP
Why do you want to avoid D5LR in neuro patients?
D5LR contains glucose and when there is cerebral ischemia, excess glucose in the brain is converted to lactic acid and worsens outcomes
5 ways to reduce cerebral blood volume in the patient with intracranial HTN
- mild hyperventilation (PaCO2 30-35) - [vasocx > decrease cbv]
- Avoid hypoxia [PaO2 < 50-60 = vasodilate > increase cbv]
- Avoid vasodilators/Give pressors
- elevate HOB > 30 degrees and avoid neck flexion
- Decrease intrathoracic pressure (avoid peep)
2 ways to decrease cerebral edema in the intracranial HTN pt
- Diuretics (mannitol)
- Steroids (dexamethasone, methylprednisone)
2 ways to decrease CSF in someone with ICHTN
- Ventric drain or VP shunt
- Acetazolamide (Diamox) or Furosemide
Why does lowering the PaCO2 < 30mmHg increase the risk of cerebral ischemia?
Due to vasoconstriction and shifting of the oxyhemoglobin dissociation curve to the left (reduces oxygen offloading- holds on to O2)
T/F: Induction drugs that reduce CMRO2 are thought of as cerebral vasoconstrictor (thiopental, propofol)
True
Which diuretics can reduce CSF production (2)
Acetazolamide and furosemide
Goal of Mannitol vs goal of furosemide in the neuro patient
Mannitol reduces intracerebral mass (water mass)- pulls water out of brain tissue , decreasing ICP
Furosemide reduces CSF production, decreasing ICP
How do osmotic diuretics work in the ICHTN pt?
Dose?
they increase serum osmolarity and “pull” water across the BBB
0.25-1g/kg
Why would mannitol increase cerebral edema?
If the BBB is disrupted, mannitol enters the brain and increases cerebral edema
Caution with mannitol and the heart failure patient
It transiently increases blood volume which can stress the failing heart (and transiently increase ICP)
How does 3% NaCl reduce ICP?
high solute concentration (high tonicity) “pulls” water across the blood-brain barrier and into the vasculature