T HE B RAIN – C OMPARATIVE N EUROANATOMY (Brain and nervous system)Structure and organization

W HAT IS THE B RAIN ? The central organ of the Nervous System. CellsTissuesOrgansSystems Neurons Nervous Tissue Brain Nervous System

W HAT 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. W HAT IS THE BRAIN MADE OF ? Special types of cells called NEURONS. These can send signals throughout the body similarly to electricity through a wire.

N EURONS N EED E NERGY 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.

E NERGY U SE = H IGH A CTIVITY 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

D OES 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] [1] small ants1:7 [2] [2] small birds1:12 human1:40 mouse1:40 cat1:110 dog1:125 frog1:172 lion1:550 elephant1:560 horse1:600 shark1:2496 hippopotamus1:2789 Proportion of brain size and body size is more important. Are mice as smart as humans?

D OES B RAIN S IZE M ATTER ? 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?

C OMMON B RAIN A NATOMY All vertebrate brains share a common form, which at its simplest consists of the forebrain, midbrain, and hindbrain.

3 C OMMON C OMPONENTS 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.

T HE F OREBRAIN 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

C EREBRAL C ORTEX What is the function of each of these areas?

A CTIVITY 2: B RAIN A CTIVITY AND ENERGY USE

L ET ’ 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 VIEWBOTTOM VIEW

A CTIVITY 1 R ESTING ac bd

A CTIVITY 2 L ISTENING TO M USIC ac bd

A CTIVITY 1 R ESTING ac bd

A CTIVITY 3 L OOKING AT A P ICTURE ac bd

A CTIVITY 1 R ESTING ac bd

A CTIVITY 4 S OLVING A P ROBLEM ac bd

A CTIVITY 1 R ESTING ac bd

A CTIVITY 5 H OPPING UP AND DOWN ON ONE FOOT ac bd

C EREBRAL C ORTEX 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)