Rucete ✏ Campbell Biology In a Nutshell
Unit 7 ANIMAL FORM AND FUNCTION — Concept 49.2 The Vertebrate Brain Is Regionally Specialized
The vertebrate brain consists of specialized regions—forebrain, midbrain, and hindbrain—that carry out distinct functions. Evolutionary adaptations across species have modified the size and function of these regions, shaping cognition, movement, and homeostasis.
1. Major Brain Regions and Their Functions
- Forebrain: olfactory bulb and cerebrum — smell, learning, sleep, cognition
- Midbrain: routes and integrates sensory input
- Hindbrain: includes cerebellum — involuntary functions, movement coordination
2. Evolutionary Adaptations in Brain Size
- Brain region sizes reflect species’ lifestyle and sensory reliance
- Ray-finned fishes: large olfactory bulbs and midbrain, small cerebrum
- Tuna: large cerebellum for 3D motion
- Lamprey: small cerebellum due to low mobility
- Birds and mammals: enlarged cerebrum, higher brain-to-body ratio, enhanced cognition
3. Human Brain Structure and Development
- Embryonic brain: forebrain, midbrain, hindbrain bulges
- Forebrain → telencephalon (cerebrum), diencephalon (thalamus, hypothalamus)
- Hindbrain → metencephalon (pons, cerebellum), myelencephalon (medulla)
4. Brainstem and Cerebellum
- Brainstem: midbrain, pons, medulla — relays info, controls basic functions
- Cerebellum: coordinates movement, integrates sensory input, motor learning
5. Diencephalon Functions
- Thalamus: relay station for sensory input
- Hypothalamus: regulates homeostasis, emotions, and endocrine function via pituitary
- Epithalamus: includes pineal gland, which produces melatonin
6. Cerebrum and Higher Functions
- Largest brain part; left/right hemispheres
- Cerebral cortex: perception, voluntary movement, memory, learning
- Corpus callosum: connects hemispheres
- Basal nuclei: plan/learn movements; damage may lead to cerebral palsy
7. Sleep, Arousal, and the Reticular Formation
- Arousal = alertness; Sleep = reduced consciousness
- Controlled by reticular formation and cerebrum
- EEG shows brain wave changes during sleep
- Dolphins sleep with one brain hemisphere at a time
- Sleep aids in memory consolidation
8. Biological Clock and the SCN
- SCN (suprachiasmatic nucleus) controls circadian rhythms
- Receives light input from retina
- Transplant experiments show SCN determines rhythm length
9. Emotions and the Limbic System
- Limbic system: amygdala, hippocampus, thalamus, hypothalamus
- Processes emotion and memory
- Amygdala: key for fear learning and emotional memory
- Interacts with forebrain to connect emotion and behavior
10. Functional Imaging of the Brain
- fMRI: measures brain activity via blood flow
- Different emotions activate specific areas (e.g., nucleus accumbens, amygdala)
- Used in stroke recovery, psychiatric research, and surgery planning
In a Nutshell
The vertebrate brain is highly specialized, with distinct regions for sensing, movement, emotion, and higher-order thought. Evolution has shaped the size and complexity of brain structures to meet species-specific needs. In humans, the cerebral cortex, brainstem, and limbic system integrate to support cognition, emotion, and homeostasis—functions now observable with powerful imaging tools.