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Neuro-Unit 1 > Thursday, 3-24-General Neurophysiology (Karius) > Flashcards

Thursday, 3-24-General Neurophysiology (Karius) Flashcards

1
Q

Describe the 2-stage process of CSF formation:

A

Step 1: Passive filtration of plasma across the choroidal capillary endothelium
Step 2: Modification of the composition by the choroid plexus: HCO3, Cl, and K concentrations controlled by channels on epithelial cells. Aquaporins also exist

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2
Q

Which ions exist in equal (or nearly so) concentrations in both the plasma and the CSF?

A
  • Na
  • Cl
  • HCO3
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3
Q

Which ions/molecules have a greater concentration in the CSF compared to the plasma?

A
  • Mg2+ (KNOW THIS)

- CO2

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4
Q

Which ions/compounds exist in greater concentration in the plasma compared to the CSF?

A
  • K+ (KNOW THIS)
  • Ca2+
  • Protein
  • Glucose (KNOW THIS)
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5
Q

CSF flows through the ventricular system. However, the flow is one way and the CSF must be ___ at the end

A

Reabsorbed

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6
Q

Absorption of CSF is done by the ___

A

Arachnoid villi

  • Endothelium of sinus and the membrane on the villi have fused
  • bulk flow of CSF into venous sinus is primary
  • pinocytosis also documented
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7
Q

Absorption of CSF is proportional to intracranial pressure. At pressures below ___ mm CSF, no absorption. Normal pressure is about __ mm CSF

A

68

112

Increased pressure causes damage to neurons

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8
Q

During circulation of CSF, from the arachnoid villi, the CSF enters the ___ by bulk flow

A

Venous sinuses

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9
Q

Regarding the BBB, capillaries in the brain have these 2 components that limit exchange:

A
  • Tight junctions between endothelial cells

- Glial endfeet come in close contact with BV

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10
Q

Passive diffusion of these substances cross the BBB:

A
  • H2O
  • CO2
  • O2
  • Free steroid hormones
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11
Q

What is the major energy source for neurons?

A

Glucose–> which does NOT cross the BBB readily

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12
Q

How does glucose cross the BBB?

A

GLUT1 transporter–> NOT insulin-dependent

  • 55k on capillaries
  • 45k on astroglia
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13
Q

___ transporter moves ions from the CSF to the blood. Its expression is tied to endothelin 1 and 3

A

Na/K/2Cl

  • Endothelin production tied to a signal from the astrocytes
  • May be related to [K+] csf
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14
Q

Many drugs do in fact cross the BBB but are moved back to the blood via ___

A

P-glycoprotein

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15
Q

What are functions of the BBB?

A
  • Maintain electrolyte composition –> particularly related to K+, maintenance of Vm
  • Protection from toxins
  • Prevent escape of NT’s
  • Protect composition of CSF
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16
Q

There are several places in the brain where we want the brain exposed to the blood. In these regions, the capillaries do not have ___ between endothelial cells

A

Tight junctions

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17
Q

The ___ are neural tissue that is “outside” or not as well protected by the BBB as other neural tissue.

A

Circumventricular organs

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18
Q

What are the 4 regions of circumventricular organs that are not as well protected by the BBB as other neural tissue?

A
  • Posterior pituitary
  • Area postrema
  • OVLT
  • Subfornical organ
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19
Q

The ___ is involved in vomiting

A

Area postrema

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20
Q

The __ and __ are both involved in control of body water/thirst/blood volume control (angiotensin)

A

OVLT and subfornical organ

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21
Q

What percentage of CO does cerebral circulation receive?

A

14% of CO (750 ml/min required)

22
Q

The ___ and __ join to form the circle of willis

A

2 internal carotids and basilar artery

-There is little mixing of blood from the 2 different sources

23
Q

What is the impact of the non-mixing of blood in the circle of willis?

A

Disruption of 1 of the inputs produces localized (discrete) areas of ischemia

24
Q

Regarding sympathetic innervation, list the neurotransmitters and receptors involved in cerebral circulation:

A

NT’s: Norepi and NPY

Receptors: alpha-adrenergics

25
Q

What is the outcome of sympathetic innervation to cerebral cicrulation?

A

Leads to constriction when systemic CO/BP increases

26
Q

Regarding parasympathetic innervation of cerebral circulation, describe the BVs, list the NTs, and the outcome of parasympathetic innervation:

A
  • Larger BV’s
  • NTs: Ach, VIP, PMH-27 (derived from pre-pro-VIP)
  • Causes vasodilation
27
Q

What are the NT’s involved in sensory innervation of the distal BVs (cerebral circulation)?

A
  • Substance P (dilation)
  • Neurokinin A (dilation)
  • CGRP (dilation)
28
Q

Describe the role of sensory innervation of cerebral circulation:

A
  • In the presence of reduced CSF volume, the brain is effectively heavier and simple motion can cause pain of the “torsion” of BV’s
  • The activation of those afferents will also cause vasodilation and increase blood flow (returns total intracranial volume closer to normal?)
29
Q

Cerebral blood flow is under ___ control; O2 consumption dictates where in the brain the blood will go

A

Local

30
Q

Cerebral blood flow is strongly influence by intracranial pressure: as intracranial pressure goes up, ___ is obstructed leading to reduced arterial flow

A

Venous outflow

31
Q

Cerebral blood flow is strongly ___ - that is, it is held constant over a wide range of systemic (mean arterial) blood pressures

A

Autoregulated

32
Q

In the face of high BP (which could damage the BBB), sympathetics in the brain will ___ the vasculature

A

Vasoconstrict –> Although this will increase the systemic vascular resistance, it protects the capillaries in the brain from damage

33
Q

Regarding cerebral circulation and the effects on mean arterial pressure, a decrease in brain perfusion will activate the ___ and increase systemic BP-sometimes drastically

A

Vasomotor centers

34
Q

What can increase the intracranial pressure?

A
  • hydrocephalus of any variety
  • edema
  • bleeding within the skull
35
Q

If blood flow is compromised, the brain will drive systemic BP __ to force blood to the brain

A

UP

Consequence: systemic BP can be driven to very high levels in order to perfuse the brain

36
Q

Most of the CSF (50-70%) is made by the specialized tissue of the ___

A

Choroid plexus

-The remaining CSF made by the tissue that lines the ventricles and blood vessels

37
Q

Where is the choroid plexus located?

A

Floor of the lateral, 3rd, and 4th ventricles

38
Q

Compare the CSF pH to the plasma pH (normally):

A

CSF pH=7.33

Plasma pH=7.4

39
Q

What is the pathway of CSF?

A

From ventricle –> through foramens of Magendie and Luschka (2 different paths) –> to subarachnoid space –> absorption of CSF into blood (absorption in arachnoide villi)

40
Q

Hydrocephalus can be caused by:

A
  • Decreased absorptive capacity of the arachnoid villi (external hydrocephalus or communicating hydrocephalus)
  • Blockage of either foramen or somewhere else in the ventricular system (internal hydrocephalus or noncommunicating)
41
Q

The Na/K/2Cl transporter moves these ions from the CSF to the blood and is stimulated by ___

A

Endothelin 1 and Endothelin 3

Likely helps keep [CSF] of K+ low

42
Q

This circumventricular organ is at the caudal portion of the 4th ventricle-the chemotactic trigger zone that initiates vomiting from blood-borne chemicals

A

Area postrema

43
Q

Describe the endothelial cells and capillaries of the circumventricular organs?

A

Endothelial cells do NOT have tight junctions between them

Capillaries are fenestrated

44
Q

Regarding innervation of cerebral vasculature, post-ganglionic sympathetic fibers have cell bodies in the ___ ganglia

A

Superior cervical

45
Q

___ nerve fibers are found on smaller arteries, are sensitive to vasodilation and torsion of blood vessels, and contain substance P, neurokinin A, and CGRP

A

Afferent

46
Q

As intracranial pressure increases, blood flow is ___ due to compression of the blood vessels

A

Reduced

47
Q

As systemic BP increases, the sympathetic innervation of the cerebral vasculature becomes ___

A

MORE active –> releases more norepi –> binds to alpha-adrenergic receptors –> causes VASOCONSTRICTION of cerebral vasculature

EFFECT=PROTECT THE BBB

48
Q

One sign of an increase in intracranial pressure (e.g., hemorrhage) is an increase in ___

A

Systemic BP

If blood flow to the brain is severely compromised, the systemic BP can go incredibly high

49
Q

___ is an enlargement of the ventricles (particularly lateral) in the brain. It is frequently a result of hydrocephalus of some form but there is a congenital form which is not related to increased intracranial pressure

A

Ventriculomegaly

50
Q

___ is an accumulation of excess CSF and results from a mismatch of production (which is constant) and reabsorption (which changes depending on CSF pressure)

A

Hydrocephalus

51
Q

What type of diet can be beneficial to children with a BBB GLUT-1 deficiency?

A

Ketogenic–> ketone bodies get across BBB through MCT-1 and used for energy for neurons

Neuro-Unit 1 (13 decks)

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