Mcb 80 - Lecture 19

Front 1

What is the basis of functional specificity?

Back 1

The arrangement of synaptic connections is selective (not random and not indiscriminate)

Front 2

What are the 3 phases of axon outgrowth?

Back 2

1. "Pathway" selection
2. "Target" selection
3. ""Address" selection

Front 3

Give an example of "pathway" selection.

Back 3

Ipsi or contralateral at the optic chiams

Front 4

Give an example of "target" selection.

Back 4

Lateral geniculate or medial geniculate

Front 5

Give an example of "address" selection.

Back 5

Layers 2, 3, and 5; dendrites f geniculocortical cells

Front 6

What are the 3 effects of axon guidance cues?

Back 6

1. Permissive
2. Attractive
3. Repulsive

Front 7

What are 3 ctegories of axon guidance cues?

Back 7

1. Mechanical (such as "glial tubes"), chemical, and electrical

Front 8

What are the 4 sites of axon guidance cues?

Back 8

1. SUbstrate
2. Other axons (fasciculation; "pioneers")
3. Guidepost cells
4. Target cells

Front 9

What is the substrate axons usually advance along?

Back 9

The "extracellular matrix"

Front 10

What does the permissive substrate usually contain in vivo?

Back 10

The glycoprotein laminin, which integrins on the axon bind to.

Front 11

What happens when cells encouter a repulsive cue?

Back 11

Growth cone collapses

Front 12

Give an example of an attractive cue.

Back 12

Chemotropism or chemotaxis, which cuases a growth cone turning repsonse

Front 13

Describe the attactive and repulsive cues for axons crossing the midline.

Back 13

Netrin is secreted by ventral midline spinal cord cells; axons with netrin receptors "chemotax" to midline; ventral idline spinal cord cells also secrete slit; axons that approach the midline are induced to upregulate the slit receptor (Robo) on their membrane; axons expressing Robo are repelled by Slit, so Robo prevents axons that cross the midline from being attracted by Netrin to cross again.

Front 14

Who was Paul Weiss?

Back 14

A proponent of physical cues guiding axons and "functional molding" of random connections (radio model)

Front 15

WHat question did Roger Sperry test?

Back 15

Will regenerating axons make connections that are functionally appropriate (radio transmission model vs. telegraph wire model)

Front 16

What is the chemoaffinity hypothesis?

Back 16

The hypothesis that all cells have chemical labels on their surfaces.The cells from the retina and tectum are matched chemically and thus find each other. Posterior retinal axons project to anterior tectum; anterior retinal axons project to posterior tectum

Front 17

Describe Roger Sperry's eye rotation experiment.

Back 17

Cut the optic nerve and rotated the eye 180 in the socket so that what was up was now down an what was tanterior was now posterio; once the severed axons regrew, the frog saw the world upside down and did not adapt (when saw fly behind it, it would flick its tongue in front of it.

Front 18

What did Roger Sperry's eye rotation experiment show?

Back 18

Showed that retinal axons were seeking an address in the tectum that was related to some "identification tag" that allowed them to recognize their appropriate target region; he supposed that the tags were chemical in nature and thus "recognition" molecules (chemoaffinity hypothesis)

Front 19

What happened when scientsits tested the growth of posterior retinal ganglion cells on a substrate made of cell membranes in alternating stripes from the posterior and anterior poles of the tectum?

Back 19

The posterior retinal ganglion cell axons preferentially grew on membranes of anterior tectum and avoided posterior tectum membranes.

Front 20

How did the anterior ganglion cells respond when scientsits tested the growth of retinal ganglion cells on a substrate made of cell membranes in alternating stripes from the posterior and anterior poles of the tectum?

Back 20

The Anterior Retinal Ganglion cells showed not preference for anterior or posterior tectum; they must cross teh anterior tectum and to get to hte posterior tectum if they were twins

Front 21

Describe the Ephrin-A gradient.

Back 21

Low in the posterior, high in the anterior

Front 22

What did John Langley do?

Back 22

At the beginning of the 20th century, he noted that that sympathetic end organs in the head were selectively activated by preagnaglionic neurons in different levels.