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Physiology 1 > Exam 2: Neurophysiology Part 3 - CSF, BBB, EEG > Flashcards

Exam 2: Neurophysiology Part 3 - CSF, BBB, EEG Flashcards

1
Q

Three layers that brain and spinal cord enveloped by

A

Dura mater - outermost layer

Arachnoid mater - middle layer

Pia mater - innermost layer

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2
Q

Dura mater

A

Thick layer of fibroblasts

Fuses with bone inner surface of skull bones

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3
Q

Arachnoid mater

A

Spider web like

thin layer of fibroblasts that trap CSF between it and pia mater

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4
Q

Pia mater

A

Single layer of fibroblasts

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5
Q

what is cerebrospinal fluid

A

clear fluid present in ventricles of brain, central canal of spinal cord, and subarachnoid space (brain and spinal cord)

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6
Q

CSF functions (4)

A

Cushion brain

Maintain consistent extracellular microenvironment for neurons and glial cells (homeostasis)

Waste control system for removal of potentially harmful cellular metabolites

Distribution medium for peptide hormones and growth factors that are secreted into the CSF

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7
Q

Where is CSF formed

A

most of CSF is formed by choroid plexuses located in each of the 4 ventricles at a constant rate

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8
Q

CSF flow

A

Lateral ventricles
Interventricular foramen (of Monroe)
Third ventricle
Cerebral aqueduct (of Sylvius) of midbrain
Fourth ventricle
Subarachnoid space through foramen of Luschka

Then on to the central canal of spinal cord or lateral aperture of fourth ventricle (foramen of Luschka)

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9
Q

What are the choroid plexuses

A

cauliflower like growth of capillaries covered by thin layer of ependymal cells that form a selective, tight junction barrier to the secretions of the leaky capillaries and to other surrounding fluids

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10
Q

What surrounds each choroid plexus

A

single layer of ependymal cells that have microvilli and tight junctions

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11
Q

relevant processes with CSF

A

Transport of Na (active), chloride, and bicarbonate into the ventricles via carriers and NaKATPase as primary active transporter

Water follows NaCl passively into the ventricle
Water leaves by osmosis

Metabolization of some potentially harmful waste products

Cl uses chlorine channels, HC3O uses bicarbonate channels

Na - H exchange is secondary active transport

Cl-Na exchange is secondary active transport

HC3O - Cl exchange is tertiary active transport

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12
Q

Hydration reaction

A

CO2 + H2O < — > H2CO3 < — > HCO3 + H

H2CO3 - carbonic acid
HCO3 - bicarbonate

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13
Q

Why does CSF need bicarbonate

A

Because it works as a buffer

Bicarb can accept 1 proton (H) to make carbonic acid and then convert it to CO2 and H2O

(Hydration reaction in reverse)

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14
Q

What causes CSF flow

A

CSF flows down a pressure gradient from site of formation at choroid plexuses through ventricular system and subarachnoid space into the venous system

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15
Q

What are the only organs that do not contain lymphatic vessels

A

Brain and spinal cord

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16
Q

What do brain and spinal cord use instead of lymphatic vessels

A

Glymphatic system

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17
Q

Glymphatic system

A

Countercurrent exchange system

Arteries and veins in the subarachnoid space have countercurrent flow, the CSF around those capillaries follow in same direction

CSF flows in same direction as artery in arterial perivascular space then goes into neural tissue via aquaporins then goes into venous perivascular space via aquaporins and follows veins away

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18
Q

where does CSF absorption into venous system take place

A

dura-lined venous sinuses within the skull

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19
Q

what happens when CSF reaches venous sinuses

A

leaves system - no backflow

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20
Q

process of CSF absorption

A

Most of fluid absorbed from subarachnoid space into dural sinuses through arachnoid villi

Absorption is pressure dependent an unidirectional

Constant absorption is important to remove waste and maintain pressure

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21
Q

Hydrocephalus

A

Increased CSF volume in skull

Often associated with increased ventricular volume and increased intracranial pressure

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22
Q

Non-communicating hydrocephalus

A

Normally caused by obstruction to CSF flow (narrow cerebral aqueduct or blocked exits from 4th ventricle)

Causes ventricular regions inside brain to expand at expense of surrounding brain tissue

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23
Q

Communicating hydrocephalus

A

Impairment of absorption (can be secondary to meningitis or hemorrhage)

Can increase CSF volume in subarachnoid space which increases pressure on outside surface of brain

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24
Q

what kind of cells are in blood capillaries and do they contain clefts

A

Endothelial cells

Do not contain clefts

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25
Q

Passage through intercellular clefts in brain capillaries

A

Blocked by tight junctions between endothelial cells

Exchange of solutes is highly selective –> small uncharged lipid soluble substances

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26
Q

Characteristics of BBB (7)

A

Few or no fenestrations

Pinocytosis uncommon in BBB

Tight junctions

Abluminal side - from one tight junction to other on brain side

Luminal side - from one tight junction to another on blood side

Specific carrier systems for uptake of solutes

Endothelium surrounded by pericytes and astrocytes

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27
Q

Molecules that can easily pass across capillary endothelium of BBB

A

Small, uncharged, lipid soluble, unbound plasma proteins

Ex - O2, CO2, ethanol, nicotine

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28
Q

Molecules that need specific carrier mediated transport mechanisms

A

glucose, amino acids

Don’t fit profile of small, uncharged, lipid soluble, etc.

29
Q

Transport systems of BBB

A 
GLUT
MCT
Amino acid transporters
OATPs
OCTs
OATs

Pgd - MDRs (Multi drug resistance protein)

MRPs - multi drug resistance associated protein

30
Q

What does ABC mean

A

ATP binding cassette

Protein that can hydrolyze ATP

31
Q

Efflux pump Pgp

A

ABC

Membrane protein, ATP dependent

first identified in cancer cells as protein that provided resistance to anti cancer drugs

Luminal side of membrane

To prevent things from reaching brain

When bad things in blood go toward brain multi drug resistance protein sends it back to lumen of capillary

32
Q

MDR1

A

Multi drug resistance 1

Protective system against external harmful substances, poissons, and medicaments

33
Q

what happened when Pgp (MDR) knockout mice got ivermectin

A

Ivermectin was able to reach brain and killed the mice because MDR (Pgp) was not there to send it away

34
Q

what is an EEG

A

electrophysiological recording based on volume conduction theory (same as in ECG, electromyogram)

spread of ionic currents within extracellular fluid that can be measured using electrodes on skin

35
Q

EEG and BAER

A

EEG - record of spontaneous brain activity

Variation - sensory-evoked potentials

BAER - brainstem auditory evoked response –> record of artificially evoked activity in brainstem and auditory system after a click stimulus in ear

36
Q

Cell types found in cerebral cortex (5)

A 
Pyramidal cells
Stellate cells
Astrocytes
Oligodendrocytes
Microglia
37
Q

Pyramidal cells

A

Projection neurons

dendrites project up toward pial surface of cortex, some extend horizontally from cell body

Generally excitatory

Axons of pyramidal cells are efferent fibers

38
Q

Stellate cells

A

local circuit interneurons within cortex

either excitatory or inhibitory

39
Q

Cortical neurons and basket cells

A

Basket cells project horizontally and make synapses with cortical neurons in level II and III

40
Q

changes in voltage recordings

A

Positive direction - deflection is down

Negative direction - deflection is up

41
Q

Frequency and amplitude in EEG

A

Frequency - deflections per second (number of AP)

Amplitude - strength of AP

More AP = competition = weaker/shorter AP
Less AP = less competition = stronger/longer AP

42
Q

EEG of alert, relaxed, and sleeping dog

A

Alert - high frequency, low amplitude

Relaxed - low frequency, high amplitude

Sleeping - low frequency, very hig amplitude

43
Q

Sensory receptors (7)

A

Mechanoreceptors - inner ear, skin, muscle spindle, Golgi tendon organ

Chemoreceptors - mouth, nose, large blood vessels, brain

Thermoreceptors - skin

Photoreceptors - eye

Electroreceptors - lateral line organ in fish

Magnetoreceptors - birds (location unknown)

Nociceptors - pain detection (located in most parts of body)

44
Q

Mechanism of action - mechanoreceptors

A

Ion channel closed –> stretch –> ion channel open

45
Q

Mechanism of action - chemoreceptors

A

Ion channel closed –> chemical stimulus attaches to thing next to channel –> causes something to bind to ion channel on inside of cell –> ion channel open

46
Q

Mechanism of action - photoreceptors

A

Ion channel open when thin bound to it on inside of cell

Light –> goes through cell and hits photoreceptor –> things that were bound to ion channel on inside of cell now gone –> ion channel closed

47
Q

Thermoreceptors and what sensory nerve fibers they are associated with

A

perception of temperature

associated with sensory nerve fibers:
pain fibers
cold fibers
warmth fibers

48
Q

Mechanoreceptors of the skin (5)

A 
Hair follicle terminal -Whiskers (vibrassae)
Ruffini's corpuscle
Meissner's corpuscle
Merkel's corpuscle
Pacinian corpuscle
49
Q

Are nerve fibers of mechanoreceptors myelinated

A

Nerve fibers of mechanoreceptors are all myelinated

50
Q

Adaptation and stimulus: Meissner

A

Adaptation - rapidly

Stimulus - touch and vibration

51
Q

Adaptation and stimulus: Merkel

A

Adaptation - slowly

Stimulus - touch and pressure

52
Q

Adaptation and stimulus: Pacinian corpuscle

A

Adaptation - rapidly

Stimulus - pressure and vibration

53
Q

Adaptation and stimulus: hair follicle sensor (hairy skin)

A

Adaptation - rapidly

Stimulus - touch and vibration

54
Q

Adaptation and stimulus: Ruffini corpuscle

A

Adaptation - slowly

Stimulus - pressure

55
Q

Tonic receptors

A

Slow adapting receptors

Generator potential spikes at on stage and slowly goes down until off stage

AP (Sensory neuron) - lots at on stage, continue to have AP until off stage

56
Q

Phasic receptors

A

fast adapting receptors

Generator potential spikes at both on stage and off stage, nothing in between though

AP (sensory neuron) - only at on stage and off stage, none in between

57
Q

Viscerosensory receptors

A

Composed primarily of free nerve endings

Visceral organs are not sensitive to cutting, heat, or cold

58
Q

secondary vs primary neurons

A

Secondary neurons - second order neurons - entirely in CNS

Primary neurons - first order neurons - in periphery

59
Q

Spinothalamic tract

A

pain

fibers cross midline and travel to contralateral white matter and go to brain

60
Q

Spinomedullary tract

A

proprioception

61
Q

what are viscerosensory fibers carried by

A

sympathetic (nociception) and parasympathetic (physiological receptors) nerves

62
Q

Are viscerosensory fibers part of ANS

A

No, not considered part of ANS

Structural component of autonomic nerves

63
Q

Types of pain

A

Acute - fast, sharp, transmitted by A-delta fibers (fast conducting), low threshold

Chronic pain - slow, dull, transmitted by C fibers (slow conducting), high threshold

Referred pain - pain fibers from skin/internal organs have synapses on same neurons/segments of spinal cord (pain in one place causes pain in another place due to neurons being from same part of spinal cord)

Phantom pain - perception of pain in an amputated limb
Theories - ascending damage to peripheral nerves; increase in NT in spinal cord; reorganization of motor and sensory cortices

64
Q

what are pain fibers

A

free nerve endings

65
Q

withdrawal reflex

A

pain fibers on skin influence motor neurons in ventral horn of spinal cord via interneurons

66
Q

withdrawal reflex example

A

Rear paw placed on something hot

Stimulate motor neurons innervating muscles of rear of thigh - flexion of knee joint

Inhibit motor neurons innervating antagonistic muscles in front of thigh

Results in retraction of paw

67
Q

How is withdrawal reflex useful in assessing depth of anesthesia

A

use it to make sure animal won’t feel anything during surgery

Pinch between toes, if there is a “twitch” anesthesia not deep enough

68
Q

treatment of pain involves (4)

A

Drugs that inhibit activation of nociceptors
aspirin, ibuprofen, NSAIDs - block synthesis of prostaglandins

Drugs that block impulse conduction in pain fibers
local anesthetics - block voltage gated Na channels

Drugs that block signal transmission in pain pathways in CNS
morphine and related substances

Via activation of body’s own pain-modulating system
gate cells in spinal cord stimulated from skin through massage, touch, warm, and cold compresses

Physiology 1 (4 decks)

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