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Neuro Endocrine 2 > General Neurophysiology > Flashcards

General Neurophysiology Flashcards

1
Q

is Cerebrospinal fluid recirculated?

A

no

always about 150 ml at any given moment

make about 550 a day

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2
Q

What are the 4 ventricles in the brain?

A

2 lateral ventricles

third ventricle

fourth ventricle (over medulla, and under the cerebellum)

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3
Q

What are the 4 connections of the ventricles

A

Intraventricular foramen: lateral ventricles to the third ventricle

Cerebral aqueduct: 3rd ventricle to the 4th ventricle

Median Aperture: 4th ventricle to Cisterna magna

Lateral apertures: 4th ventricle to arachnoid space

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4
Q

What produces 50-70 percent of the CSF

A

Choroid plexus

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5
Q

what makes 30 percent of the CSF

A

made by the tissue that lines the ventricles and blood vessels

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6
Q

What is the first step of the process of making CSF, and how is this possible

A

Have passive filtration of plasma from the blood vessels into the ventricles

Hydrostatic pressure

  • large capillary “bloodpressure”
  • small tissue hydrostatic pressure
  • – push fluid into capillary

Oncotic pressure or Osmotic pressure

  • this is the pull pressure
  • Identical at the choroid plexus
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7
Q

What is the second step in the formation of the CSF

A

modification of Ion composition

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8
Q

What ion concentrations are controlled by channels of epithelial cells

A

HCO3
Cl
K

aquaporin 1 allows H2O

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9
Q

if intracranial pressures change what happens to the production of CSF

A

Production of CSF is constant over a wide range of intracranial pressures, even high or low pressures

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10
Q

What ion concentrations stay equal between both the plasma and the CSF

A

Na+

and HCO3

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11
Q

What ions are concentrated more in CSF than in plasma

A

Mg++

Cl-

CO2 (brain produces lots of CO2

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12
Q

What ions are more concentrated in plasma than CSF

A

K+ (therefore CSF can tolerate the efflux of K+ from action potentials)

Ca++

Protein (affects pressure and pH)

Glucose

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13
Q

where is the CSF absorbed

A

Arachnoid villi

flows into the venous sinus

some pinocytosis occurs

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14
Q

What plays a factor in the amount of CSF absorbed

A

absorption of CSF is proportional to intracranial pressure

at pressures below 68mm CSF = no absorption

normal pressure is 112 mm CSF

increased pressure can damage neurons

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15
Q

what is the role of the CSF

A

protect the brain, in CSF the brain only weighs 50 g

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16
Q

what are the two components that limit exchange in the blood brain barrier

A

tight junctions between endothelial cells

glial endfeet come in close contact with blood vessel

17
Q

what substances can cross the BBB via passive diffusion

A

H20 via AQP -4

CO2

O2

free steroid hormones

18
Q

how does glucose cross the blood brain barrier, and what are the two forms of this protein

A

Glut 1 transporter

not insulin dependant

55k for capillaries

45k on astrogila

Neurons use Glut -3 to move glucose in

19
Q

what plays an important role in keeping the lower concentration of K+ in the CSF

A

Na/K/2Cl transporter

moves these ions from the CSF to the blood

these transporters are expressed via the endothelin 1 and 3 from the endothelial cells of the blood vessels

20
Q

some drugs are able to cross the BBB but how are they pumped back to the blood

A

P-glycoprotein (pump glycoprotein)

glycoprotein binds to variety of substances and then will be pumped back to the blood from the CSF

21
Q

what is the function of the BBB

A

protects the chemical composition of the CSF from blood borne agents

particularly the K+

and the maintenance of Vm

22
Q

what are the four circumventricular organs and what does this mean

A

several places in the brain where the brain is exposed to blood, and their are no tight junctions

Posterior pituitary : for releasing hormones into the blood

Area postrema: chemotactic trigger zone to induce vomitting

Organum casculosum of the lamina terminalis (OVLT)

Subfornical organ

(both are involved in control of the body water/thirst/blood volume control)

23
Q

Despite the apperance of having an anstamoses of the circle of willis what is the clinical relevence of this anastamoses

A

disruption of one of the inputs produces localized (discrete) ares of ischemia because the brain would rather lose one part of the brain than divert blood from other areas to help that area

24
Q

What is the sympathetic innervation of the Cerebral circulation

A

Neurotransmitter: Norepi and Neuropeptide Y (NPY)

Receptors: Alpha adrenergics

leads to constriction when systematic cardiac output/blood pressure increases

25
Q

what is the parasympathetic innervation of the Cerebral cirulation

A

innervation of larger vessels

Ach

Vasoactive intestinal polypeptide

PHM-27

all three of these cause vasodilation

26
Q

what are the three neurotransmitters released and act on the blood vessels from its own sensory innervation

A

Substance P (dilation)

Neurokinin A (dilation)

CGRP (dilation)

27
Q

when do the sensory fibers render the blood vessels of the brain

A

extremely sensitive to torsion and manipulation (lead to pain)

in the presence of decreased CSF the brain is heavier and a simple motion can cause pain

this ill then activate the afferents that will cause the vasodilation and increase blood flow (to try and return total intracranial volume closer to normal)

28
Q

how is cerebral blood flow controlled

A

local control

oxygen consumption dictates where in the brain the blood will go

29
Q

how is the cerebral blood flow regulated

A

it is autoregulated and is held at a constant over a wide range of systematic (mean arterial) blood pressures

therefore even at high and low blood pressures the brain will get the same amount of blood flow

30
Q

What happens in the face of high systematic blood pressure

A

the sympathetics will take over and VASOCONSTRICT the vasculature

even though this will increase the systematic vascular resistance it protects the capillaries in the brain and the blood brain barrier from damage

31
Q

how does intracranial pressure influence the cerebral blood flow

A

as intracranial pressure goes up, venous outflow is obstructed leading to reduced arterial blood flow

a decrease in brain perfusion will activate the cardiovascular control centers in the medulla and increase systematic BP, sometimes dramatically

32
Q

What are some common causes that increase intracranial pressure

A

hydrocephalus of any variety

Cerebral edema

Intracranial bleeding

Neuro Endocrine 2 (24 decks)

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