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

18

THE PHYSICAL BRAIN

Fueling the Brain 19

The human brain makes up just 2

percent of the body’s total weight, but it

consumes 20 percent of its energy. The

large human brain is an expensive organ

to run, but the benefits of a big, smart

brain make it a good investment.

GLUCOSE FUEL

BRAIN

SIZE: 2%

BRAIN’S ENERGY

NEEDS: 20%

Protein transporters

Glucose and other

essential molecules are

actively moved across the

barrier through channels and

gates in the membrane.

Receptors

Hormones and similar

substances are picked up by

receptors. They are enclosed

in a vesicle (sac) of membrane

for passage through the cell.

Transcytosis

Large proteins, which are

too big to pass through channels,

are absorbed by the membrane

and enclosed in a vesicle for its

journey through the cell.

Active efflux

When unwanted materials

diffuse through the blood-brain

barrier, they are removed by a

biochemical pumping system

called efflux transporters.

Vesicle merges with

membrane to

release contents

Hormone reaches

receptor and enters

vesicle

Protein molecule

enclosed in vesicle

Glucose

Internal

carotid artery

THE BODY’S ENTIRE

SUPPLY OF BLOOD IS

PUMPED THROUGH THE

BRAIN EVERY 7 MINUTES

CI

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IS

UNDERSIDE

OF BRAIN

Basilar

artery Cerebellar

artery supplies

cerebellum

Vertebral

artery

The Circle of Willis

The carotid and vertebral supplies connect at the

base of the brain, via communicating arteries, to

create a vascular loop called the Circle of Willis.

This feature ensures cerebral blood flow is

maintained, even if one of the arteries is blocked.

Posterior cerebral

artery supplies

back of brain

Direction of

blood flow

Anterior

cerebral artery

supplies front

of brain

Median

cerebral artery

supplies side

of brain

Arteries encircle

stalk of pituitary

gland, optic

tracts, and basal

hypothalamus

Waste pumped

into blood vessel

Unwanted

waste

products

Gates made

from protein

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