Nervous System Flashcards
Nucleus vs. Ganglion
Nucleus: neurons in CNS
Ganglion: neurons in PNS
White Matter vs. Grey Matter
White matter has high density myelin, few neurons, not metabolic, not much ATP, not too vascularized
Grey matter has high density of neurons and dendrites, highly vascularized, lots of ATP needed, highly metabolic (therefore gets more cerebral blood flow than white matter)
Spinal Cord functions
sensory input, reflex circuits, somatic and autonomic motor outputs
Reticular Formation, function and damage leads to what?
receives info entering brain stem and spinal cord, filters it
regulates arousal, wakefulness
when damaged, pt in vegetative state
Medulla: function, which cranial nerves, damage causes what?
Function: subconscious CV and respiratory, brainstem reflexes, early processing of information such as auditory, gustation, and balance
CN: 8-12
damage: pt unable to regulate vitals
Pons: function, cranial nerve #’s?
function: respiratory, urinary, and some CV control, motor of eye, motor/sensory of face (ventral: relay info to cortex, dorsal: taste, sleep, resp)
CN: 5-8
Midbrain: function, CN #
function: pain, pupil reflex, eye movement, acoustics, motor coordination (contains substantia nigra)
CN 3-4
What are the two pain centers in the brain?
Midbrain and thalamus
Cerebellum: function, CN #
function: coordination and equilibrium (input from spinal cord, cortex, inner ear), motor learning, sensory association of language
CN: 8
Thalamus: function, CN #
function: relays sensory information to the cortex, attention and consciousness (wakefulness), pain
CN: 2
diancephalon
hypothalamus and thalamus
hypothalamus
pleasure center of the brain, addiction is a huge problem here
autonomic, endocrine functioning, motivated behavior, circadian rhythms
what part of the brain has the superchiasmic nucleus, and what is this responsible for?
superchiasmic nucleus in the hypothalamus is responsible for circadian rhythms
basal ganglia functions?
thalamocortical motor inhibition patterns, controlling fine motor movements
amygdala
social behavior and emotion
hippocampus
memory
cerebral cortex: function and CN#
function: in order to work, it is dependent on lower brain to work, personality, learning, language, planning
CN: 1
4 lobes of cerebral cortex and functions
Frontal: personality, speech (Broca’s area), planning motor behavior, area that is important with pain tolerance
Parietal: sensory, spacial, Wernicke’s area
Temporal: sound, facial recognition, regulates ANS, emotions (limbic)
Occipital: vision, pupil constriction and accommodation
What part of the Circle of Willis, if occluded, has no collateral flow
Middle Cerebral Artery (if this is blocked on left side, Wernicke’s area/ speech comprehension is blocked)
Why is the Artery of Adamkiewicz important?
It supplies the lower 2/3 of the cord, it is a reticular artery branch of the aorta, in some procedures, the aorta is clamped, since this artery has no collateral flow, it can damage/paralyze the lower 2/3 of the spinal cord!
In spinal cord blood supply, what is the difference between the anterior and posterior arteries?
Posterior arteries have two branches of supply, ventral/anterior only has one, so it is a huge problem if this artery becomes occluded, motor control may be lost (bc ventral=motor and dorsal=sensory)
How much cerebral blood volume do we have (compared to brain tissue)?
0.5 mL/ 100 g brain tissue
What can impact blood flow to the brain
Artery blockages
Venous blockages, ex: positioning (head on one side, steep trendelemberg, positive flow ventilation, high peaks)
Where is ICP measured and what is the normal value?
In the lateral ventricles in the supratentorium space, between occipital lobe and cerebellum
Normal 8-12
Intracranial volume (ICP measurements) is made up of 3 things, and what are the percentages?
Brain tissue/ICF 80%
Blood 12%
CSF 8%
Risk of herniation is increased when ICP is increased, what does this do to CPP, and how is MAP involved?
CPP decreases, unless you have a high enough MAP to compensate
CPP=MAP-ICP
What is intracranial elastance?
Change in ICP from a change in intracranial volume
What are some compensatory mechanisms involving intracranial elastance, when ICP increases?
- CSF moves from cranial to spinal compartment
- increased absorption of CSF (by arachnovilli)
- decreased CSF production
- decrease cerebral blood volume
What is normal CPP? Why is it important?
80-100 mmHg
(MAP-ICP)
This is how much O2 is reaching the brain
What is normal cerebral blood flow in ml/g/min and ml/min
50mL/100g/min
750mL/min
Relationship of neuronal activity (metabolism) and CBF
Increased metabolic by-products, increased blood flow
Relationship between H+ ions/ CO2 and CBF
Do H+ ions cross the blood brain barrier?
Increased CO2 will increase H+ ions (by increasing carbonic acid), and this will increase CBF, vasodilates (we hyperventilate, decrease PCO2, to decrease ICP, decrease CBF)
YES, H+ ions cross the blood brain barrier, this is why messing with a patient’s PCO2, changes pH quickly, but it doesn’t last long
When PCO2 changes by 1 mmHg, what is the EXACT change in CBF (ml/100g/min) and CBV (ml/100g)
Increased PCO2 will increase CBF
CBF changes 1-2ml/100g/min
CBV changes 0.05ml/100g of brain tissue
What is the average Cerebral Metabolic Rate (CMRO2)? How is it different in children?
3ml/100g/min
Children have twice the metabolic needs (5.2ml/100g/min)
Relationship of temperature and CBF?
Decreased temp decreases CBF/ EEG monitor shows less activity
Irreversible brain damage over 42 degrees C
The brain can’t store much glucose, what does this have to do with metabolism and CBF?
90% of brain tissue ONLY operates on AEROBIC conditions (34 ATP with O2/Krebs, 2 ATP without O2/glycolysis), within 3-8 minutes, the tissue will have irreversible damage with no oxygen (O2 coming from blood supply, so when vessels are occluded, “time is brain”)
What is the exact brain glucose consumption?
Brain glucose consumption: 5.5mg/100g/min
Relationship of PaO2 and CBF
When it drops to 50 mmHg (80-100 normal), it does a “hail mary” and CBF increases (makes sense: as we become hypoxic, we send more flow to the brain), this is not clinically useful
Autoregulation: What does intrinsic myogenic response of the arteries have to do with CBF?
They help maintain a constant CBF by adjusting based on pressures: when the vessels sense low pressures, vasodilation occurs, when they sense high pressures, vasoconstriction occurs
SNS role in CBF?
Autoregulation plays the main role in CBF, SNS only takes over in extreme BP rise (to prevent a stroke, it will constrict large vessels to keep from the small vessels receiving such a high pressure and occluding), therefore SNS works as a protective mechanism
Relationship of blood viscosity and CBF
decreased HCT will increase CBF, but decrease O2
Severe polycythemia will reduce CBF
(think: increased viscosity= increased HCT, means the blood is thicker, therefore the flow of blood will be slower)
What is the capacity of the brain and spinal cord? How much of that is filled with CSF? How much CSF is in the cerebral ventricles?
Capacity: 1600 mL
CSF: 150 mL
Cerebral ventricles: 30 mL
Remainder volume is brain and spinal cord
What forms CSF? How fast is it formed? How many times a day is it formed? What absorbs CSF?
forms: choroid plexus at 0.35mL/min, 3-4 times a day
absorbs: arachnoid villi
Where are the choroid plexuses? What do they do?
They are in lateral (not posterior horn), third, and fourth ventricles, they make CSF and use epedymal cells to transport the CSF
When looking at the difference of concentration of ions and constituents in the blood compared to lumbar CSF, what are the major difference? (hint: Na, K, Cl, glucose, protein, and pH)
Protein is much lower in CSF (30) than in blood (6,800)
K, glucose, and pH is a little LOWER in CSF than blood
Na and Cl are HIGHER in CSF than blood