brain

Complexity of the Human Brain

• The human brain has evolved significantly over time.

• Comparative mammalian brain collections provide insight into brain structure and evolution.

• Relevant collections available from the University of Wisconsin and the National Museum of Health and Medicine.

Protection of the Brain

• The brain is part of the central nervous system, protected by the skull.

• The spinal cord is also protected by vertebrae.

• Meninges: a multilayered tissue covering the brain and spinal cord for further protection.

• Cerebrospinal fluid (CSF) is found around the brain and vertebrae, acting as a cushion to prevent injury during trauma.

Ventricles of the Brain

• The brain contains a network of cavities called ventricles, filled with CSF.

• Components of the ventricular system:

  • Two lateral ventricles (one for each hemisphere).

  • Third ventricle.

  • Cerebral aqueduct.

  • Fourth ventricle.

• These ventricles allow for the circulation of cerebrospinal fluid, aiding in protection against head injuries.

Evolution of the Nervous System

• Earliest ancestors had a simple central nervous system focused on reflexive responses.

• Complexity increased with evolution, seen in modern fishes.

• Different regions evolved for specific functions:

  • Hindbrain: movement and balance.

  • Midbrain: vision and hearing.

  • Forebrain: olfactory function (smell).

• The human brain retains these fundamental structures, with advanced functions especially in the cerebral cortex.

Brain Structure and Function

• The brain mainly consists of neurons organized for function.

• Three main parts:

  • Hindbrain:

    • Medulla oblongata: regulates vital functions (respiration, heartbeat, muscle tone).

    • Pons: connects medulla and cerebellum, involved in respiration and sleep.

    • Cerebellum: coordinates movement and balance, implicating learning low-level sensory-motor relationships.

    • Reticular formation: regulates consciousness and arousal levels, integrating sensory information.

  • Midbrain:

    • Divided into tectum (visual/auditory processing) and tegmentum (movement, arousal, learning).

  • Forebrain:

    • Divided into cerebral cortex and subcortical structures.

    • Functions include sensory processing, emotional regulation, and cognitive behaviors.

Forebrain Structures

• Hypothalamus: regulates hunger, sleep, emotions, and sexual activity.

• Thalamus: processes sensory input and organizes it for higher brain areas.

• Cerebrum: has two hemispheres connected by the corpus callosum, includes subcortical structures.

• Basal Ganglia: controls movement and automatic responses.

• Limbic System: center for pleasure and fear; plays a role in emotional memory, mainly composed of:

  • Amygdala: key role in fear detection and emotional memory.

  • Hippocampus: crucial for memory consolidation; affected by Alzheimer's disease due to neurodegeneration.

Limbing System Components

• Septal Area: linked to pleasure and emotional responses.

• Hippocampus: important for memory; consists of two structures corresponding to each hemisphere, resembles a seahorse.