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BMS249 DEVELOPMENTAL NEUROBIOLOGY > MECHANISMS OF AXON GUIDANCE 1 > Flashcards

MECHANISMS OF AXON GUIDANCE 1 Flashcards

1
Q

WHAT ARE THE TWO HYPOTHESIS FOR SPECIFIC NEURONAL CONNECTIONS

A
  1. WEISS RESONANCE THEORY

2. SPERRY CHEMOAFFINITY

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2
Q

WHAT WAS WEISS THEORY

A

RANDOM AND DIFFUSE NEURONAL OUTGROWTH OCCURS TO ALL TARGET FOLLOWED BY ELIMINATION OF NON FUNCTIONAL CONNECTIONS

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3
Q

WHAT WAS SPERRY THEORY

A

DIRECT SPECIFIC OUTGROWTH OCCURS THROUGH AXONS FOLLOW IDENTIFICATION TAGS CARRIED BY THE CELLS AND FIBRES IN THE EMBRYO

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4
Q

HOW DID THEY TEST WHETHER THE SPERRY OR WEISS TEST WAS CORRECT

A
  1. CUT THE OPTIC NERVE (AMPHIBIAN) AND REMOVED THE TEMPORAL RETINA ALLOWING JUST NASAL AXONS TO GROW BACK
  2. IF WEISS WAS RIGHT THE AXONS WOULD GROW ALL ALONG THE PATHWAY AND THEN BE ELIMINATION
  3. IF SPERRY WAS RIGHT THE MOTOR AXONS ARE GUIDED SPECIFICALLY TO THEIR TARGET
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5
Q

WAS THE WEISS RESONANCE THEORY OR THE SPERRY CHEMOAFFINITY THEORY CORRECT

A

THE SPERRY

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6
Q

IN THE EARLY CHICK EMBRYO, IF THE NERUAL TUBE IS CUTE AND REPLACED OR REVERSE BEFORE MOTOR AXONS GROW OUT, WHAT IS THE RESULT

A

DESPITE THIS NORMAL INNERVATION OCCURS AND MOTOR AXONS STILL FIND THEIR TARGETS

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7
Q

WHAT COULD BE CONCLUDED FROM THE CHICK NEURAL TUBE EXPERIMENT

A

THIS SUGGESTS THE AXONS ARE ACTIVELY NAVIGATED

ENVIRONMENT CONTAINS GUIDANCE CUES THAT AXONS CAN USE TO FIND THE CORRECT TARGETS

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8
Q

WHY DO WE DO EXPERIMENTS ON INSECTS

A
  1. SIMPLE NS
  2. EASY TO MANIPULATE
  3. LARGE INSECT CELLS EASY TO ABLATE

EG GRASSHOPPER

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9
Q

UPON EXPERIMENTS ON INSECTS SUCH AS GRASSHOPPER WHAT HAS BEEN FOUND IN RELATION TO AXON PATHWAYS

A

ALL PATHWAYS ARE STEREOTYPED EMBRYO TO EMBRYO, SEGMENT TO SEGMENT.
THIS HAS ALLOWED A MAP TO BE MADE - COREY GOODMAN

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10
Q

WHAT DOES REPRODUCIBILITY OF AXON BEHAVIOUR SUGGESTS WHAT

A

GROWTH CONES ARE RESPONDING TO CUES IN THE ENVIRONMENT

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11
Q

PATHWAYS SEEM TO CHANGE UPON ENCOUNTERING SPECIFIC …………………..

A

AXONS

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12
Q

IN ABLATING CELLS, FOUND THAT MOST AXONS ……………… TO BEHAVE NORMALLY BUT OTHER AXONS …………….. IT MUST BE THAT SOME GROWTH CONES ARE LOOKING FOR ……………….. CUES FROM THE ……………….. AXON.

A

CONTINUE
STALL
SPECIFIC
ABLATED

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13
Q

WHAT IS THE LABELLED PATHWAY HYPOTHESIS

A

AXONS SELECTIVELY BUNDLE WITH OTHER AXONS
AXON SURFACES CARRY LABELS/CUE
DIFFERENT AXON GROWTH CONES EXPRESS DIFFERENT SETS OF RECEPTORS FOR CUES
EARLY AXONS FOR AN AXON SCAFFOLD ON WHICH LATER AXONS CAN EXTEND

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14
Q

WHAT IS ANOTHER NAME FOR AN EARLY AXON

A

PIONEER

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15
Q

WHAT IS ANOTHER NAME FOR A LATE AXON

A

FOLLOWER

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16
Q

THE LABELLED PATHWAY HYPOTHESIS IS TRUE IN AMPHIBIANS, WHAT ABOUT MAMMALS

A

THIS IS TRUE FOR MAMMALS ASWELL

17
Q

GIVE AN EXAMPLE OF PIONEER AND FOLLOWER NEURONS IN MAMMALIANS

A

SUBPLATE NEURONS IN THE CORTEX PROJECT FROM THE CORTEX TO THE THALAMUS BEFORE INNERVATION OF THE CORTEX BY LATERAL GENICULATE NUCLEUS
ABLATION OF THE SUBPLATE = LGN FAILURE

18
Q

HOW DO THE PIONEER AXONS FIND THEIR WAY IF THERE ARE NO OTHER AXONS TO RESPOND TO

A

PIONEER AXONS ARE ALSO STEREOTYPED AND SEEM TO RESPOND TO SPECIFIC POINT IN THE PATHWAY

19
Q

HOW DO PIONEER AXONS GO ABOUT FINDING THEIR TARGET

A

CELLS IN THE PATHWAY ARE STEPPING STONES/GUIDE POST CELLS

20
Q

WHAT EXPERIMENT SHOWS PIONEER AXONS RESPOND TO ENVIRONMENTAL CUES

A

THE PIONEER TI1 GROWTH CONE MAKES A TURN AT THE LIMB BOUNDARY AND AGAIN AS IT APPROACHES A SPECIFIC CELL, CX1. ABLATION OF CX1 CAUSES STALLING OF THE GROWTH CONE

21
Q

WHAT ARE THE FOUR FORCES OF AXON GUIDANCE

A

CHEMOATTRACTION AND REPULSION

CONTACT ATTRACTION AND REPULSION

22
Q

NEURONS VARY GREATLY BUT ALL EXHIBIT ………………. IN TERMS OF SHAPE OR FUNCTION

A

POLARITY

23
Q

WHAT DO DENDRITES DO

A

RECEIVE INCOMING INFORMATION

24
Q

WHAT DO AXONS DO

A

CARRY INFORMATION AWAY FROM THE CELL BODY IN ACTION POTENTIALS

25
Q

AXONS HAVE HIGHLY POLARISED ………….. (+ END TOWARDS GROWTH CONE. DENDRITES ALSO HAVE MICROTUBULES BUT THESE ARE LESS ORDERED AND HAVE MIXED ……………………… THE DIFFERENCE IS DUE TO LOCALISATION OF DIFFERENT TYPES OF ………………………………… ……………………………….. ……………………… (MAP)WHICH DETERMINE HOW THEY ARE CROSS LINKED

A

MICROTUBULES
ORIENTATIONS
MICROTUBULE ASSOCIATED PROTEINS

26
Q

AXONS EXPRESS WHICH MAP

A

TAU

27
Q

DENDRITES EXPRESS WHICH MAP

A

MAP2

28
Q

WHAT IS A NEURITE

A

A NEURONAL PROJECTION - EITHER A DENTRITE OR AXON

29
Q

KINESINS ARE PART OF ………………………….. STRUCTURE. IT IS …………. END DIRECTED AND SO WILL BE GOUND TOWARDS THE …………………. CONE OF AXONS. GFP LABELLING SHOWS KINESIN MOVING AROUND TO SEE WHICH SHOULD BECOME AN ……………..

A

MICROTUBULE
PLUS
GROWTH
AXON

30
Q

WHAT UNDERLIES AXON CHOICE

A

NEW BORN NEURITES ARE TYROSINATED AND THEREFORE DYNAMIC MICROTUBULES
STABILISED ACETYLATED MICROTUBULES ARE PRESENT ONLY IN THE NEWLY POLARISED AXON

31
Q

WHAT DOES ARTIFICIAL STABILISATION (BY TAXOL) OF MICROTUBULES IN A NEURITE CAUSE

A

AXON FORMATION

32
Q

WHAT IS THE OUTCOME OF CUTTING OFF AN AXON

A

LEADS TO NEW AXON SELECTION IN A FEEDBACK LOOP

BMS249 DEVELOPMENTAL NEUROBIOLOGY (14 decks)

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