9. Neurophysiology Flashcards
Whats CSF
Bathe brain and spinal cord
contain centrcile and subarach space
Transecelular fluid
Fxn CSF
1 Protective water bath effect
Cushion - change pos
1.4kg wt effect weight - 50g (archimedes principle)
- Protective role buffer rise ICP - CSF tlocation to excran SAH
Tlocat csf vault to excran comp min rise pressure -
limited - Return IS protein to circ
abosrp csf across arach villi
Waste productes
nutritive role
?neuropept tport by it
What total vo csf adult
150
Dail prod - 500-600
turnover 3-4 times day
Formed
1 Choroid plexus - 67%
later third 4th vent
Direc ependyma - walls ventr 33%
Thin membrane glial cell lining ventricle brain
Flow foramens magendie luschka
to Sub arac space
Abs - arach villi 90% - arach proj into ven sinus
or
direct into veunles
Acitve tport Na into CSF _ apical memrane epdnymal cell
cont carrb anyhdrase - prod HCO3
also tport into CSF - provide buffer
Primary secretion high [bic] - after buffer conc csf ~~ plasma
Normal range for ICP - formation + aborption CSF relate to CSF pressure
ICP 5-15
Rate form not affect icp
rate abosrp constat - low
increase lineary as rise above 6.8
certrain pressure rate formation and rate absopr =
- equilibrium csf pressure
Blood flow to chorid plex - determ rate csf prod - affected factors affect cerbral flow
change in cerbral flow alter blood vol
What way composition CSF diff to plasma
- PCo2 higher 6.66 - lower ph 7.33
- Protein content - normally very low
- leads low a-b buffer - Chemical component
Addut - enzymatic degratin endothel cell - sub
chem barrier - prevent entrering ECF brain
MAOi - Dopa decarb - prevent entry some amine
What substances easily cross barrier
O2
CO2
All lipid soluble
Water rel easy - lower than most other cap
Gluc - hexose tport syst
AA
Electro must be able cross - may not occur rapidly
Na - active CSF - choroid
How was presence BBB discovered
Water soluble acidic dye - infused - nearly all tissue stain
brain exception - trypn blue
What the circumventricular organ
SMall areas outside BBB
1 Post Pit
2 CTZ
3 Subfornical organs
4 Organum vasculosum of lamina terminalis
Pineal gland high perm capo
Fxn 0 require access circulation
neuroendo reason
CTZ - stim chem cant cross
secr horm
resp horm
Propagation of AP
Draw AP single peripehral myelinated axon
What are the processes result in development and propagation of nerve AP
Periphera nerve cell membrane - stable RMP 70 (inside negative_
Know as RMP -
Exposed current - membrane pot decrease
reach certain level = threshold potential -> rapidly depol
Sudden open Na chanell
RMP overshot to 30-35+Mv
Electraical gradient move Na reverse - Na chanell close
K open - K moves out
Slower - more sustain - repol + rest of RMP
BRief - local depol affect surround
CUrent sin = potentia surrounding to decrease
decrease - throshold - surround depol - repeat net porpagation down axtion
= ACTION POTENTIAL
Na and K channel - voltage gated channel - open and close response to spec Membrane potential
channel open and close repsonse to chem - ligand gated channel
What diffce myelinated and unmyelinated
Myelinated - layer melin - schwann cell - cover except at nodes of ranvier
- Depol jump node to node in myelindated axon
= AP travels faster than in unmyelin
Saltatory conduction
Occulocardiac relex
Whats the OCR - How precip
Trigemino vagal reflex -
initiated within orbit -
causes vagal effects on heart
Factors precip reflex 1 Traction exoc muscle 2 Acute globe pressure 3 Traction Iris 4 Eye trauma 5 Retrobulbar haematoma 6 Retrobulbar injection
What nervous pathway involved in reflex
1 Aff limb ophthalmic branch of trigeminal nerve
via ciliary ganglion + nasociliary nerve
Sensory nucels trigeminal nerve
Linked to motor Nucles vagus
Eff - Vagus -> Heart
inhib SA node
Adverse conseq stim OCR
SInus brady - can be more severe
SInnus arrest
AV block
arrest
death
How to respond OCR
Tel surgeon stop
IV atropine 7mcg.kg
rpeeat necc
can be used immed veofe to prevent
high dose can cause marked tachy
TOtal vagal block - 3mg atropine in adult
IM not effective
Retrobulbar can work
Other factors - adequacy ventilation - hypercap - increased incidence OCR
surgical tech
Adeq depth anaes
Peripheral nerves
Draw compound erve AP - mixed perip nerve follow supermax stim
Compound - sum AP all axon in peripheral nerve
Large nubmber nerve axons - held CT sheath
C layers
Epinerum
perineurium
endoneurium
Time on X
Potetnial on Y
Aa Ab AyAd B C
Stim supramax -
all nerves fire
AP travel diff rate – arrive different time
Multi peak shape -
Nerve axon in perip nerve
severeal group w/ sim fxn and diam
Sim condction velocity
Classify function nerve fibre
Erkanger and Gasser - common class system - perphral nerve
Fiber Diam Velocity Maj fxn
Aa 12-20 80-120 Motor ant horn, sens - prop
Ab 5-12 30-70 Sensory - touch + Pressure
Ay 3-6 15-30 Motor to muscle spindle yeff
B <3 3-15 Autonoic - preganglionic
C .4 - 1.3 .5-2.5 Autonomic - post gang symp,
sens - pain and temo
What is saltatory conduction
How many adj nodes ranvier - block LA - before AP block
Rapid cond myelinated - d.t insulation - prevent depol - exposed depol node ranv - Na clsuter - jump node to node
LA block ~ 3 adj node
Further - advant salt - min ion flow req prop AP
Ion flux would be much higher if had to cross
Dosal colum
Spinocerbral
COtricospinal
Rubrosinal
Vestibuloarspianl
Reticulospinal
Autonomic
Dosal column - Proprio, vibration, discrim
Spinocerebellar - Subconci mm position tone
COticospinal voluntary mm
Rubrosinal Flex m tone
Vestibuloarspianl reflex + MM tone
Reticulospinal vol mve head post
Autonomic descending tract
Main functions of hypothalamus
- Water balance
- Temperature
3 Ant pit hormone control
4 Production of posterior pituitary hormones
5 Appetite Satiety
6 Behaviour emotions
Water balance control hypothalamus
Central coordinator control water balance
Receive input sensor - integrate input + initiate effector response
integrate input and initiates efector response
1 Osmoreceptors located ant hypothal
2 Thirst initiate hypothal
3 Volurecptor neural input to hypotahl - stim inhib thirst + adh
4 Ang II - act subfornical organ + organum vasculosum of lamina terminalis - provide neural input stim thirst + ADH release
5 ADH prod supraoptic and paraventric nuclei in hypothalamus - hormone travel axons post pit
How does hypothalamus regulate hormones in ant pit
Secretion or inhibit stim neurohormone - travel hypothal -> pituitary by hypothal hypophyseal portal circ
Neurohormones - mech - brain exert dynamic control over endocrine system
All hormones ant pituitary are trophic (stim another gland)
= growth promoting effects on target gland
TSH FSH LH GH ACTH increase secretion specific target gland hormone
The post pit has beural connection w. hypot
ant pit vascular connection
Post pit - part brain develops neural pathway connecting to hypothal
Ant pit - ectodermal outpouch (rathkes) from roof oral cava - a/w develop post pit - develops vascular connections w/ hypothal
What are the neurohormoes from hypothal which reg ant pit
CRH - Corticotrophin RH
TRH - Thyrotopin RH
GRH - Gh RH
LHRH - Luet hrom RH ( also GnRH - gonadotrop RH)
PRH - Prolactin RH
GIH - GH inhib hormone - somatostatin
PIH - Prolactin inhib hormone - dopamine
Apart Dopa - all hormone neuropept - short t1/2 in circ - dont an effect on any other organ
RMP
What is it
whats the value typical myelinated periph nerve axon
What is RMP -
Steady state potential - exists across cell membrane
About 70mV - inside membrane negative respect to outisde
How Does RMP develop
1- Na K ATpse - pump Na out - For K intracell
Conc diff -
2 Membrane Perma Na K - ted leak - own conc grad
3 100x more perm K vs Na
Leaking - more K lost cell than Na enter
Net resul - larger pos chrage left than entered
Inside - net neg charge comp outside
4
Other fact small effect on RMP
Na pump 0 electrogenic More Na pump out than K in
3 Na 2 K
Small net itracell loss - pos charge - few mv of RMP
Gibbs donnan limits K efflux
SUmmary
Na pump set init conc diff
Differential perm membrane - respons diff leak
unequel charge sep
Pump leak hypoth
Goldman eqn Ion contrib most RMP High conc present large tmembr conc grad larg membran perm K - all major contrib RMP
Actual RMP in nerve cell - not much diff equi ppotetna K - determ enrest eqn
