THE BRAIN – COMPARATIVE NEUROANATOMY

(Brain and nervous system)

Structure and organization

WHAT IS THE BRAIN?

The central organ of the Nervous System.

Cells Tissues Organs Systems

Neurons NervousTissue Brain Nervous

System

WHAT DOES THE BRAIN DO? Controls all organs of the body, and is at

work all the time. Helps an animal make sense of the all the

information it receives through its senses, and generates appropriate responses.

WHAT IS THE BRAIN MADE OF? Special types of cells

called NEURONS. These can send

signals throughout the body similarly to electricity through a wire.

NEURONS NEED ENERGY

Neurons require more energy than most other cells because they need to constantly maintain an electrical gradient across their membrane in order to send and receive signals.

The brain, therefore needs a HUGE amount of energy compared to other organs.

In humans, the brain accounts for about 2.5% of our body weight, but uses about 20-25% of our energy.

ENERGY USE = HIGH ACTIVITY

Energy usage by certain areas of the brain can be visualized using imaging techniques like PET scans and fMRIs. A tracer (something that emits light and can

create a picture on a computer) is attached to sugar and given to a person.

Neurons use more sugar when they are more active, so active parts of the brain will show up a different color.

This can be used to show what regions of the brain are primarily used for different tasks, so we can gain more information about brain function.

PET Scan

DOES BRAIN SIZE MATTER? Brain size tends to increase with body size

Larger animals generally need larger brains just to cope with the additionally sensory information of their larger bodies.

Species Simple brain-to body ratio (E:S)[1]

small ants 1:7[2]

small birds 1:12

human 1:40

mouse 1:40

cat 1:110

dog 1:125

frog 1:172

lion 1:550

elephant 1:560

horse 1:600

shark 1:2496

hippopotamus 1:2789

Proportion of brain size and body size is more important.

Are mice as smart as humans?

DOES BRAIN SIZE MATTER?

Predators tend to have larger brains than prey species.

Mammals tend to have larger brains, and primates even more so.

BUT big brains are energetically costly. Changes in diet quality during evolution are thus linked with changes in brain size.

AND there is more to consider. What about sizes of particular regions? What other characteristics of a brain might be important?

COMMON BRAIN ANATOMY

All vertebrate brains share a common form, which at its simplest consists of the forebrain, midbrain, and hindbrain.

3 COMMON COMPONENTS

The hindbrain is responsible for “nonthinking” functions like breathing, heart rate, and sleep The hindbrain contains the cerebellum, which is

important in balance and coordination The midbrain is associated with vision,

hearing and arousal.

Together, the hindbrain and midbrain (without the cerebellum) are called the brainstem.

THE FOREBRAIN

The forebrain contains the cerebrum, which is involved in complex functions.

The outer layer of the cerebrum is called the cerebral cortex. This is involved in higher level processes like

memory, perception, language, learning, and consciousness

***Across vertebrates, the brainstem is generally similar, but differences appear in the forebrain, where it is greatly enlarged in mammals, with the cortex containing many more folds, or gyri. These folds help to pack more neurons in

and give the brain more power

CEREBRAL CORTEX

What is the function of each of these areas?

ACTIVITY 2: BRAIN ACTIVITY AND ENERGY USE

LET’S LOOK AT A TYPICAL BRAIN DURING THE SOME EVERYDAY ACTIVITIES. Think about:

What might be the functions of each of the lobes?

High activityLow Activity

a

b

c

d

TOP VIEW BOTTOM VIEW

ACTIVITY 1 RESTING

a c

b d

ACTIVITY 2LISTENING TO MUSIC

a c

b d

ACTIVITY 1 RESTING

a c

b d

ACTIVITY 3LOOKING AT A PICTURE

a c

b d

ACTIVITY 1 RESTING

a c

b d

ACTIVITY 4SOLVING A PROBLEM

a c

b d

ACTIVITY 1 RESTING

a c

b d

ACTIVITY 5HOPPING UP AND DOWN ON ONE FOOT

a c

b d

CEREBRAL CORTEX

Frontal – Primary motor cortex (movement) and problem solving, language

Temporal – Primary Auditory and Olfactory Cortex (hearing and smell)

Occipital – Primary Visual Cortex (sight) Parietal – Primary Sensory Cortex (touch)