How the Brain Works The Facts Visually Explained by DK (z-lib.org)

26

THE PHYSICAL BRAIN

Networks in the Brain 27

Small-world networks

Brain cells are not connected in a regular

pattern, nor are they in a random network.

Instead, many of them exhibit a form of

small-world network, where cells are seldom

connected to their immediate neighbors but

to nearby ones. This way of networking

allows each cell to, on average, connect to

any other in the smallest number of steps.

Channel open

With the channel open, calcium ions are

now able to move from the synaptic cleft into the

dendrite. In response, the dendrite adds more

glutamate receptors to the surface of the dendrite.

More receptors

With more receptors active, the dendrite

is able to pick up more neurotransmitters, and

so any signal sent from the neighboring axon

is received much more strongly.

2 3

Random

A random network

is good at making

long-distance

connections but poor

at linking nearby cells.

Small-world

Small-world networks

have good local and

distance connections.

Every cell is more

closely linked than in

the other two systems.

Lattice

By connecting every

cell to its neighbors,

this network has

reduced scope to

make long-distance

connections.

Calcium ions

pass freely

Magnesium

ion removed

from channel

More

neurotransmitters

received

Extra glutamate

receptors

introduced

IT IS ESTIMATED THAT

THE HUMAN BRAIN

CONTAINS 100 TRILLION

CONNECTIONS BETWEEN

ITS 86 BILLION NEURONS

US_026-027_Networks_in_the_Brain.indd 27 20/09/2019 12:31