Brain Structures and Functions – Study Notes

I. Major Divisions of the Brain

1. Forebrain (Prosencephalon) – Responsible for higher cognitive functions, sensory processing, and regulation of body functions.

   • Cerebrum

   • Diencephalon (Thalamus, Hypothalamus, Epithalamus)

2. Midbrain (Mesencephalon) – Involved in motor control, vision, and auditory processing.

3. Hindbrain (Rhombencephalon) – Controls basic survival functions and motor coordination.

   • Cerebellum

   • Brainstem (Pons & Medulla Oblongata)

II. Forebrain: Cerebrum

• Largest part of the brain, divided into two hemispheres.

• Responsible for thinking, reasoning, voluntary movement, and perception.

Cerebral Cortex (Outer Layer of the Cerebrum)

• Made up of gray matter (neuron cell bodies).

• Divided into four lobes, each with distinct functions:

1. Frontal Lobe (Higher Cognitive Functions)

• Functions:

  • Voluntary movement (Primary Motor Cortex in the Precentral Gyrus)

  • Problem-solving, reasoning, and decision-making

  • Personality and emotions

  • Speech production (Broca’s Area – left hemisphere)

2. Parietal Lobe (Sensory Processing)

• Functions:

  • Processes touch, pain, pressure, and temperature (Primary Somatosensory Cortex in the Postcentral Gyrus)

  • Spatial awareness and body orientation

3. Temporal Lobe (Hearing and Memory)

• Functions:

  • Auditory processing (Primary Auditory Cortex)

  • Language comprehension (Wernicke’s Area – left hemisphere)

  • Memory formation (Hippocampus is located here)

4. Occipital Lobe (Vision)

• Functions:

  • Processing visual information (Primary Visual Cortex)

Key Cerebral Features

• Longitudinal Fissure – Separates the left and right hemispheres.

• Corpus Callosum – Connects both hemispheres for communication.

• Central Sulcus – Separates frontal and parietal lobes.

• Lateral Sulcus – Separates the frontal and temporal lobes.

III. Forebrain: Diencephalon

Located beneath the cerebrum, responsible for sensory processing and autonomic functions.

1. Thalamus

• Acts as a relay station for sensory information (except smell) to the cerebral cortex.

2. Hypothalamus

• Maintains homeostasis (body temperature, hunger, thirst).

• Controls the autonomic nervous system and endocrine system (via the pituitary gland).

• Regulates the sleep-wake cycle (circadian rhythm).

3. Mammillary Bodies

• Involved in memory processing and part of the limbic system.

4. Infundibulum

• Connects the hypothalamus to the pituitary gland, playing a role in hormone release.

IV. Midbrain (Mesencephalon)

• Located between the forebrain and hindbrain.

• Plays a role in motor control, vision, hearing, and alertness.

Key Structures:

1. Pineal Gland – Secretes melatonin, regulates sleep cycles.

2. Corpora Quadrigemina (Four rounded structures)

   • Superior Colliculi – Controls visual reflexes (e.g., tracking moving objects).

   • Inferior Colliculi – Controls auditory reflexes (e.g., turning head toward sound).

3. Cerebral Peduncles – Large bundles of nerve fibers carrying motor commands from the cerebrum to the spinal cord.

V. Hindbrain (Rhombencephalon)

Controls involuntary functions and motor coordination.

1. Cerebellum ("Little Brain")

• Coordinates balance, posture, and fine motor control.

• Contains the Arbor Vitae ("tree of life") – white matter that helps with coordination.

• Connected by the Vermis.

2. Brainstem (Essential for Survival)

• Connects the brain to the spinal cord and controls autonomic functions.

a) Pons

• Connects different brain regions.

• Assists with breathing control, sleep, and facial movements.

b) Medulla Oblongata

• Controls vital autonomic functions:

  • Heart rate, breathing, blood pressure

  • Reflexes: Swallowing, coughing, sneezing, vomiting

• Contains cranial nerve nuclei (IX - XII).

VI. Cranial Nerves Overview

• 12 pairs of cranial nerves originate from the brain and brainstem.

• Important ones related to the brainstem:

  • IX (Glossopharyngeal) – Swallowing, taste, saliva production.

  • X (Vagus) – Parasympathetic control of heart, lungs, digestion.

  • XI (Accessory) – Controls neck and shoulder muscles.

  • XII (Hypoglossal) – Controls tongue movements.

VII. Functional Brain Systems

1. Limbic System (Emotion & Memory)

   • Includes hippocampus, amygdala, and mammillary bodies.

   • Controls emotions, learning, and memory formation.

2. Reticular Formation (Awareness & Alertness)

   • Network of neurons in the brainstem.

   • Controls wakefulness, attention, and consciousness.

VIII. Summary Table: Major Brain Structures & Functions