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Neuro I Exam 2 - Pathways > Lecture 14: General Neurophysiology > Flashcards

Lecture 14: General Neurophysiology Flashcards

1
Q

What is the two-stage process in the formation of CSF; conncentrations of what ions are controlled and how does water cross?

A

Step 1: Passive filtration of serum

Step 2: HCO3, Cl-, and K+ concentrations are controlled by channels on epithelial cells. Aquaporin 1 allows H2O to cross

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2
Q

How does the production of CSF change over a wide range of intracranial pressures?

A

Production of CSF is constant, regardless of ICP

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3
Q

What is found in equal concentrations between the CSF and plasma?

A

HCO3-

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4
Q

What is found in higher concentration in the CSF then in plasma?

A
  • Mg
  • Cl-
  • CO2
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5
Q

What is found in higher concentration in the plasma than in the CSF?

A
  • K+
  • Ca2+
  • Protein
  • Glucose
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6
Q

Absoprtion of CSF is proportional to ICP; at what pressure is there no absorption?

A

Pressures below 68 mm CSF

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7
Q

Capillaries in brain have 2 components that limit exhange, what are they?

A
  1. Tight junctions between endothelial cells
  2. Glial endfeet come in close contact w/ BV
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8
Q

Which molecules are able to passively diffuse across the BBB; what channel for water?

A
  • H2O via AQP-4
  • CO2
  • O2
  • Free steroid hormones (not protein bound)
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9
Q

What is the major energy source for neurons and how are they able to acquire it; does this process depend on insulin?

A
  • Glucose
  • Glut 1 transporter to cross BBB

- Two forms: 55K on capillaries and 45K on astroglia

  • NOT insulin dependent!
  • Neurons use Glut-3 to move glucose in
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10
Q

What is the purpose of the Na/K/2Cl transporter on the BBB; expression of this transporter is tied to?

A
  • Move all of these ions from CSF —> Blood
  • When thinking hard, the [K+] of your CSF will increase and needs to be removed to maintain the RMP of the neurons
  • Expression tied to endothelin 1 and 3
  • ET production tied to signal from astrocytes
  • May be related to [K+]CSF
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11
Q

Many drugs do cross the BBB but many of which are quickly moved back to blood by what?

A

P-glycoprotein

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12
Q

What are the 3 major functions of the BBB?

A
  1. Maintain electrolyte composition, particularly K+ and Vm (membrane potential)
  2. Protection from toxins
  3. Prevent escape of NTs
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13
Q

In the nueronal areas where we don’t want a BBB, what strucutral piece is missing?

A

Tight junctions

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14
Q

What is the name of the organs that are neural tissue not protected by the BBB; how many regions?

A
  • Circumventricular organs
  • There are 4 regions
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15
Q

What are the 4 circumventricular areas that lack BBB

A
  1. Posterior Pituitary: releases hormones into blood
  2. Area Postrema: trigger zone for vomiting
  3. Organum Vasculosum of the lamina terminalis (OVLT): involved in control of body water/thirst/blood volume
  4. Subfornical organ: involved in control of body water/thirst/blood volume
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16
Q

What are the NT’s, receptor, and function of the sympathetic innervation of cerebral circulation?

A
  • NT’s: Norepi and NPY
  • Receptor: α-adrenergic
  • Function: leads to constriction when systemic cardiac output/BP increases
17
Q

What are the parasympathetic NT’s and function for cerebral circulation?

A
  • ACh, VIP, PHM-27 (derived from pre-pro-VIP)
  • Cause vasodilation
18
Q

Which vessels of the cerebral circulation have sensory innervation?

A

Distal blood vessels

19
Q

What 3 NT’s are released at the blood vessels in cerebral circulation and cause vasodilation?

A
  1. Substance P
  2. Neurokinin A
  3. CGRP
20
Q

The sensory fibers of the vasculature of cerebral circulation render the vessels extremely sensitive to what?

A

Torsion/manipulation - lead to pain

21
Q

What is the role of sensory innervation of the cerebral circulation in the presence of reduced CSF volume?

A
  • Brain is effectively heavier w/ reduced CSF and simple motion can cause pain due to torsion of the BV’s
  • Causes activation of the afferent fibers, which will cause vasodilation and increase blood flow
22
Q

Cerebral blood flow is under local control; what dictates where in brain blood will go?

A

Oxgen consumption

23
Q

Cerebral blood flow is under what kind of regulation?

A
  • Auto-regulation
  • Held constant over a wide range of system (mean arterial) BP’s
24
Q

In the face of high BP (>140 mmHg) the auto-regulation mechanisms of the brain will not be able to maintain constant blood flow, what system will come into play?

A
  • Sympathetics in brain will VASOCONSTRICT (Norepi and NPY) the vasculature
  • This will increase the systemic vascular resistance, but it protects the capillaries in the brain and the blood brain barrier from damage
  • Damage may occur within systemic vasculature/organs, but at the end of the day the brain takes precedent
25
Q

Cerebral blood flow is strongly influenced by ICP, what occurs as the ICP goes up?

A
  • Venous outflow is obstructed
  • Leading to reduced arterial flow
26
Q

As ICP increases, venous outflow is obstructed, and arterial flow/perfusion of the brain will be decreased, what does this lead to?

A
  • Activation of vasomotor centers and increase systemic BP - sometimes DRASTICALLY (>300 mmHg)
  • Brain will do everything it takes to get blood perfusion
27
Q

Which aquaporin is most important in controlling brain-water balance?

A

AQP4

Neuro I Exam 2 - Pathways (18 decks)

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