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THE BRAIN – COMPARATIVE NEUROANATOMY (Brain and nervous system) Structure and organization WHAT IS THE BRAIN? The central organ of the Nervous System. Cells Neurons Tissues Nervous Tissue Organs Brain Systems 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. Simple brain-to body Species ratio (E:S)[1] Proportion of brain 1:7[2] size and body size is small ants small birds 1:12 more important. Are mice as smart as humans? 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 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? a b c d Low Activity High activity TOP VIEW BOTTOM VIEW ACTIVITY 1 RESTING a c b d ACTIVITY 2 LISTENING TO MUSIC a c b d ACTIVITY 1 RESTING a c b d ACTIVITY 3 LOOKING AT A PICTURE a c b d ACTIVITY 1 RESTING a c b d ACTIVITY 4 SOLVING A PROBLEM a c b d ACTIVITY 1 RESTING a c b d ACTIVITY 5 HOPPING 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)
