model systems

Question 1

why experiment on chickens? (galls domestics)

Answer 1

They can be used for chimeric transplantation experiments

Chickens are used primarily because of their ease of performing transplantation experiments and following the results in a live embryo. This makes them a very important model for studying nervous system development They can also be used for behavioural experiments such as investigating imprinting and passive avoidance learning.
‘higher’ animals such as chickens, mice etc have NOT had their nervous systems mapped to anywhere near the same depth as fruit flies and worms. The ability to map and manipulate neural circuits in flies and worms has proved to be an invaluable tool in uncovering how circuits etc can lead to particular neural activities.
Mice are an example of a ‘higher’ animal with a very complex nervous system that can be genetically manipulated using transgenics to understand how genes influence nervous system development and function.

Question 2

trepanning

Answer 2

7000 BC

making a hole in the skull

Question 3

view of brain in ancient greece

Answer 3

clear correlation between structures and function
hands and feet etc
believed the head to hold the senses
therefore brain = organ of sensation

Question 4

hippocrates

Answer 4

brain= sensation + intelligence

Question 5

Aristotle

Answer 5

brain = radiator

Question 6

view of the brain at the time of the Roman Empire

Answer 6

Galen (130-200 CE) said:

• cerebrum: squidgy
• cerebellum: hard

‘form= function’

cerebrum= sensations (memories)
cerebellum= commands muslces

more or less correct!

Question 7

Galen- on nerves

Answer 7

ventricles are hollow therefore nerves transmit humours to limbs etc

Question 8

Galvani, du Bois- Reymond - on nerves

Answer 8

muscles twitch when electrically stimulated

Question 9

Bell, Magendie

Answer 9

cut dorsal and ventral roots- ventral - paralysis

Question 10

Magendie

Answer 10

nerves are mixtures of wires

Question 11

Flourens

Answer 11

regional ablation in birds– cerebellum controls movement

so different cerebral regions control different fucntions

Question 12

Fritsch, Hitzig

Answer 12

electrical stimulation in dogs

Question 13

Ferrer

Answer 13

electrical stimulation in monkeys

Question 14

Munk

Answer 14

ablation of occipital lobe (vision)

Question 15

invertebrate models

Answer 15

for the questions of how nerves transmit electrically

squid - giant axon (J Z Young)

<1mm
easy dissection and support
external and internal perfusion with varying salines
allowed determination of ion flows in action potential

Question 16

Hodkin and Huxley

Answer 16

used Lollgo Vulgaris squid’s axon to discover the action potential

Question 17

Caenorhabditis elegans (c. elegans)

Answer 17

fully mapped genome and nervous system

model system for developmental cell death- apoptosis

Question 18

drosophilia melanogaster

Answer 18

e.g. identification of genes regulating nervous system development role of pax-6 in eye development /evolution

Question 19

Frogs- Galvani

Answer 19

electrical stimulation

Question 20

Frogs- Helmholtz

Answer 20

nerve conduction velocity

Question 21

Frgs- Katz and Miledi-

Answer 21

Ca2+ and release

Question 22

Frogs- harrison

Answer 22

how axons grow

Question 23

Frogs- Sperry

Answer 23

how nerve path find

Question 24

Birds-development Gallus domesticus

Answer 24

allows easy embryonic manipulation and study
transplantation
nerve growth factor

Question 25

Hitzig and Fritsch

Answer 25

mapped motor cortex of dogs