9. Neurophysiology

Question 1

Whats CSF

Answer 1

Bathe brain and spinal cord

contain centrcile and subarach space

Transecelular fluid

Question 2

Fxn CSF

Answer 2

1 Protective water bath effect
Cushion - change pos
1.4kg wt effect weight - 50g (archimedes principle)

2. Protective role buffer rise ICP - CSF tlocation to excran SAH
   Tlocat csf vault to excran comp min rise pressure -
   limited
3. Return IS protein to circ
   abosrp csf across arach villi

Waste productes
nutritive role
?neuropept tport by it

Question 3

What total vo csf adult

Answer 3

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

Question 4

Normal range for ICP - formation + aborption CSF relate to CSF pressure

Answer 4

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

Question 5

What way composition CSF diff to plasma

Answer 5

1. PCo2 higher 6.66 - lower ph 7.33
2. Protein content - normally very low
   - leads low a-b buffer
3. Chemical component
   Addut - enzymatic degratin endothel cell - sub
   chem barrier - prevent entrering ECF brain
   MAOi - Dopa decarb - prevent entry some amine

Question 6

What substances easily cross barrier

Answer 6

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

Question 7

How was presence BBB discovered

Answer 7

Water soluble acidic dye - infused - nearly all tissue stain

brain exception - trypn blue

Question 8

What the circumventricular organ

Answer 8

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

Question 9

Propagation of AP
Draw AP single peripehral myelinated axon

What are the processes result in development and propagation of nerve AP

Answer 9

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

Question 10

What diffce myelinated and unmyelinated

Answer 10

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

Question 11

Occulocardiac relex

Whats the OCR - How precip

Answer 11

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

Question 12

What nervous pathway involved in reflex

Answer 12

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

Question 13

Adverse conseq stim OCR

Answer 13

SInus brady - can be more severe

SInnus arrest
AV block
arrest
death

Question 14

How to respond OCR

Answer 14

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

Question 15

Peripheral nerves

Draw compound erve AP - mixed perip nerve follow supermax stim

Answer 15

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

Question 16

Classify function nerve fibre

Answer 16

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

Question 17

What is saltatory conduction

How many adj nodes ranvier - block LA - before AP block

Answer 17

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

Question 18

Dosal colum

Spinocerbral

COtricospinal

Rubrosinal

Vestibuloarspianl

Reticulospinal

Autonomic

Answer 18

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

Question 19

Main functions of hypothalamus

Answer 19

1. Water balance
2. Temperature

3 Ant pit hormone control

4 Production of posterior pituitary hormones

5 Appetite Satiety

6 Behaviour emotions

Question 20

Water balance control hypothalamus

Answer 20

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

Question 21

How does hypothalamus regulate hormones in ant pit

Answer 21

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

Question 22

The post pit has beural connection w. hypot

ant pit vascular connection

Answer 22

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

Question 23

What are the neurohormoes from hypothal which reg ant pit

Answer 23

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

Question 24

RMP

What is it

whats the value typical myelinated periph nerve axon

Answer 24

What is RMP -
Steady state potential - exists across cell membrane

About 70mV - inside membrane negative respect to outisde

Question 25

How Does RMP develop

Answer 25

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