Brain Regions and Structures Study Guide
Divisions of the Vertebrate Brain
The vertebrate brain is structurally categorized into three main divisions:
Hindbrain:
Composed of the medulla, pons, and cerebellum.
Directs essential survival functions, including breathing, sleeping, and wakefulness.
Manages motor coordination and physical balance.
Midbrain:
Positioned directly atop the brainstem.
Serves as a connective bridge between the hindbrain and forebrain.
Controls specific motor movements and transmits auditory and visual information.
Forebrain:
Composed of the cerebral cortex, thalamus, and hypothalamus.
Manages complex cognitive activities, sensory processing, associative functions, and voluntary motor activities.
The Brainstem and Subcortical Structures
Brainstem:
The oldest part and central structural core of the brain.
Controls automatic survival functions.
Acts as a crossover point where most nerves connecting to and from each side of the brain cross over to connect with the body's opposite side.
Medulla:
Located at the base of the brainstem.
Controls vital autonomic functions, specifically heartbeat and breathing.
Pons:
Located directly above the medulla within the brainstem.
Coordinates movement and plays a critical role in controlling sleep.
Thalamus:
Central sensory control center situated at the top of the brainstem.
Directs incoming sensory messages to sensory receiving areas in the cerebral cortex.
Transmits reply messages back to the cerebellum and medulla.
Reticular Formation:
A complex nerve network extending through the brainstem into the thalamus.
Plays a central role in controlling arousal and alertness.
Cerebellum:
Known as the "little brain," positioned at the rear of the brainstem.
Processes sensory input, coordinates voluntary movement output and balance, and enables nonverbal learning and procedural memory.
The Limbic System
The limbic system comprises neural structures associated with emotions, bodily drives, and memory processing:
Amygdala:
Consists of two bean-sized neural clusters.
Linked directly to emotional processing, particularly fear and aggression.
Hypothalamus:
Located directly below the thalamus.
Directs vital bodily maintenance activities, including eating, drinking, and body temperature regulation.
Helps govern the endocrine system via control of the pituitary gland (the master endocrine gland).
Plays a major role in emotional states and reward processing.
Hippocampus:
A seahorse-shaped neural structure.
Critical for processing explicit, conscious memories for storage.
Structural Organization of the Cerebral Cortex
Cerebral Cortex Overview:
Serves as the ultimate control and information-processing center of the body.
Contains approximately nerve cells and synaptic connections.
Consists of paired left and right cerebral hemispheres, connected by the axon fibers of the corpus callosum and covered by an intricate fabric of interconnected neural cells.
Divided into four distinct lobes per hemisphere, separated by structural fissures.
The Four Anatomical Lobes:
Frontal Lobe: Positioned at the front of the brain; involved in muscle movement, speaking, planning, and judgment.
Parietal Lobe: Positioned at the top rear of the head; receives sensory input for touch and body position.
Occipital Lobe: Positioned at the back of the head; processes visual information.
Temporal Lobe: Positioned roughly above the ears; processes auditory information.
Motor and Sensory Functions of the Cortex
Motor Functions & Motor Cortex:
Located at the rear of the frontal lobes.
Controls voluntary movements.
Cortical Mapping: Investigations by Otfrid Foerster and Wilder Penfield demonstrated that body areas requiring precise control (such as the fingers, thumb, and lips) occupy the largest proportion of cortical space.
The motor cortex section in the right hemisphere controls movement on the body's left side, while the left hemisphere section controls the right side.
Brain-Machine Interfaces: Implants designed to detect motor cortex activity allow individuals to control external equipment, enabling recipients to move robotic arms using thought processing alone.
Somatosensory Cortex:
Located at the front of the parietal lobes, parallel to and directly behind the motor cortex.
Receives incoming messages from skin senses and body part movements.
The sensitivity of a body region dictates the amount of somatosensory cortex space allocated to it (e.g., lips and fingers occupy significantly larger cortical areas than the torso or legs).
The somatosensory cortex section in the left hemisphere receives sensory input from the right side of the body.
Visual Cortex:
Located in the occipital lobes at the back of the head.
Receives sensory input directly from the eyes.
Relays visual information to specialized regions responsible for complex tasks, such as face identification, emotion detection, and face recognition.
Auditory Cortex:
Located within the temporal lobes above the ears.
Receives information from the ears via a circuitous pathway leading from one ear to the auditory receiving area situated above the opposite ear.
Association Areas and Higher Mental Functions
Definition and Features:
Areas of the cerebral cortex that are not dedicated to primary motor or sensory functions.
Distributed across all four cerebral lobes.
Direct higher mental operations, including learning, remembering, thinking, reasoning, and speaking.
Prefrontal Cortex:
Located in the forward portion of the frontal lobes.
Enables complex executive functions such as judgment, planning, social interaction skills, and processing new memories.
Damage to the prefrontal cortex can severely alter personality, remove behavioral inhibitions, and disconnect moral reasoning from actual physical conduct.