Anatomy & Physiology - Brain Structures

Brain Anatomy Overview

General Structure

• The brain is divided into distinct regions, each responsible for various functions.

• Major divisions include the Forebrain, Midbrain, and Hindbrain.

Forebrain

• Cerebrum (Cerebral Hemispheres): Largest part of the brain, consisting of two hemispheres.

  • Cerebral Cortex (Neocortex): Outer layer responsible for complex functions, divided into lobes.

  • Diencephalon: Contains key structures.

  • Thalamus: Acts as a relay station for sensory information from the body.

  • Hypothalamus: Regulates autonomic functions like hunger, thirst, sleep, and body temperature.

  • Mammillary Bodies: They are involved in memory processing, particularly in relation to the limbic system, rather than emotions directly.

  • Infundibulum: It is a stalk that connects the hypothalamus to the pituitary gland but does not function as a direct communication pathway for hormonal regulation (that’s done via the hypothalamic-hypophyseal portal system and neural connections).

Lobes of the Cerebrum

• Frontal Lobe:

  • Functions: Voluntary movement, memory, intelligence, personality.

  • Precentral Gyrus: Ridge in the frontal lobe that contains the primary motor cortex.

• Parietal Lobe:

  • Functions: Processes sensory information from the body, responsible for spatial awareness.

  • Postcentral Gyrus: Ridge that contains the primary somatosensory cortex.

• Temporal Lobe:

  • Functions: Associated with hearing, taste, and memory processing.

• Occipital Lobe:

  • Functions: Primarily responsible for vision.

Key Features of the Cerebrum

• Longitudinal (Sagittal) Fissure: Major groove separating the two hemispheres.

• Central Sulcus: Shallow groove separating frontal and parietal lobes.

• Lateral Sulcus: Separates the frontal lobe from the temporal lobe.

• Corpus Callosum: A commissure made of white matter, connecting the two hemispheres for communication.

Midbrain

• Contains several important structures:

  • Pineal Gland: Secretes melatonin, regulates sleep cycles.

  • Corpora Quadrigemina: Involved in visual and auditory reflexes.

  • Superior Colliculi: Visual reflexes.

  • Inferior Colliculi: Auditory reflexes.

  • Cerebral Peduncles: These are major nerve fiber tracts in the midbrain that carry motor information from the cerebrum to the brainstem and spinal cord.

Hindbrain

• Includes the Cerebellum and Brainstem:

  • Cerebellum: Coordinates balance and motor control (features: Arbor Vitae and Vermis).

  • Pons: Connects different brain regions and regulates reflexes.

  • Medulla Oblongata: Controls autonomic functions such as heart rate and respiration, and contains centers for sneezing and coughing.

• Cranial Nerves (9, 10, 11, 12) are connected in this area for vital functions.

• Cranial Nerves in the Medulla: The cranial nerves associated with the medulla are IX (Glossopharyngeal), X (Vagus), XI (Accessory), and XII (Hypoglossal)—correct as listed. They play crucial roles in autonomic and motor functions, including swallowing, speech, and parasympathetic control.