BIOL 1911 Chapter Notes - Chapter 49.2: Hindbrain, Midbrain, Amygdala
49.2 – The vertebrate brain is regionally specialized
• Three major regions: forebrain, midbrain and hindbrain that are all specialized in function
• Forebrain
o Contains olfactory bulb and cerebrum
o Has activities that include processing of olfactory inputs, regulation of sleep, learning, and any complex
processing
• Midbrain
o Located centrally in the brain
o Coordinates routing of sensory input
• Hindbrain
o A part of it forms the cerebellum
o Controls involuntary activities, such as blood circulation
o Coordinates motor activities, such as locomotion
• Relative sizes of each particular brain region vary across species of vertebrates
o Size differences reflect differences in the importance of particular brain functions
o Evolution has thus resulted in a close match of structure to function, with the size of particular brain regions
correlating with their importance for that species in nervous system function, and hence, species survival and
reproduction
• Comparison of birds and mammals with groups that diverged from common vertebrate ancestor earlier in evolution
o Forebrain in birds and mammals is a large fraction of the brain than in amphibians, fishes and other vertebrates
o Birds and mammals have much larger brains relative to body size than do other groups
o The above two trends reflect the greater capacity of birds and mammals for cognition and higher-order
reasoning
• How are so many cells and links organized into circuits and networks that can perform highly sophisticated information
processing, storage, and retrieval?
o 100 billion neurons and 100 trillion connections in humans
Arousal and Sleep
• Transitions in attentiveness and mental alertness are regulated by the brainstem and cerebellum, which control arousal
and sleep
• Sleep is an active state, at least for the brain
o Recordings from the EEG reveal that brain wave frequencies change as the brain progresses through distinct
stages of sleep
o Sleep is essential for survival, but still little is known about its function
o Hypothesis: sleep and dreams are involved in consolidating learning and memory
• Arousal and sleep are controlled in part by the reticular formation, a diffuse network formed primarily by neurons in the
midbrain and pons
o Control the timing of sleep periods characterized by REM and by vivid dreams
o Sleep is also regulated by the biological clock and by regions of the forebrain that regulate sleep intensity and
duration
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