Brain Anatomy and Functions

Section Two: Overall Anatomy and Functions of the Brain

Main Structure and Functions of the Brain

  • The brain is composed of various structures, each responsible for multiple functions.
  • This section serves as a review of the main structures and their primary functions.
  • A deeper exploration of these structures will occur in section three.

Important Announcements

  • If feeling sick, students are advised to stay at home and inform the instructor via email to excuse their absence.
  • Lecture slides and readings must be kept up to date.
  • Personal circumstance: The instructor is assisting with their father's recovery from open-heart surgery and emphasizes the importance of health.

Overview of Brain Views

  • Sagittal View: Side view of the brain.
  • Mid-sagittal Cut: A cut along the midline to reveal inner brain structures.

Lobes of the Brain

  • Frontal Lobe: Located at the front of the brain, where the eyes would be.
  • Parietal Lobe: Located just behind the frontal lobe.
  • Occipital Lobe: Situated at the very back of the brain.
  • Temporal Lobe: Located near the temples.

Brain Divisions

  • Forebrain Structures: Include the cortex and subcortical structures.
  • Midbrain Structures: Located above the hindbrain, involved in various functions.
  • Hindbrain Structures: Includes the pons, medulla, and cerebellum.

Detailed Structures of the Brain

  • Hindbrain: Comprises the pons, medulla, and cerebellum.
  • Midbrain: Positioned above the hindbrain, includes various midbrain structures.
  • Forebrain: Most evolved part of the brain, enabling advanced human capabilities.
    • Cortex (Cerebral Cortex): Outermost layer responsible for many advanced functions.
    • Subcortical Structures: Located beneath the cortex, includes the thalamus, hypothalamus, amygdala, corpus callosum, and pituitary gland.

Brain Structure Orientation

Drawing the Brain

  • Draw the frontal lobe, occipital lobe, temporal lobe, and cerebellum along with the spinal cord for orientation purposes.

Brain Stem vs. Hindbrain and Midbrain

  • Brain Stem: Comprises the midbrain, pons, and medulla.
  • Hindbrain: Defined to include the cerebellum, pons, and medulla (overlap exists with the brain stem).

Brain Hemispheres

  • Two cerebral hemispheres: right and left, based on perceptual directions.
  • Bilateral symmetry allows for similar structures in both hemispheres.
  • The hemispheres differentiate greatly during evolution, unlike the relatively unchanged brainstem characterized by its basic functions across species.

Brain Size and Composition

  • The human brain is approximately the size of a fist and weighs around three pounds.
  • Contains 86 billion neurons, with the cerebral cortex having the highest density.

Human Brain Characteristics

  • A large human brain includes a longitudinal fissure, dividing the right and left hemispheres, and other protective layers (e.g., dura mater).
  • Examples of brain features: corpus callosum and blood-brain barrier.

Brain Anatomy: The Cortex

Overview of the Cortex

  • The cortex is the outer gray matter layer of the brain
  • Subcortical structures contain gray matter but are not classified as cortex.
  • White matter consists of myelinated axons form functional pathways known as tracts.

Importance of Brain Folds

  • Convolutions: The folded structure of the brain increases surface area, allowing for greater neuron density without increasing brain size drastically.
  • This design is essential for optimizing brain function within the skull's limits.
  • Metaphor: Similar to expanding a crumpled balloon or a raisin to increase its size and volume.

Neuron Density in the Brain

  • There are 16 billion neurons in the cortex, representing a significant proportion of the total neuron count in the brain.

Anatomical Terms and Features of the Brain

Gyri and Sulci

  • Gyrus (plural: Gyri): Ridges or protrusions in the brain.
  • Sulcus (plural: Sulci): Grooves or valleys between the gyri.
  • Fissure: A deep sulcus that separates major regions of the brain.

Key Fissures to Know

  1. Longitudinal Fissure

    • Separates the right and left hemispheres of the brain.
    • Extends down the midpoint, serving as an important anatomical landmark.

  2. Sylvian (Lateral) Fissure

    • Separates the frontal lobe from the temporal lobe.
    • Identifiable from different views of the brain, with distinct placements in various anatomical perspectives.

  3. Additional Fissures

    • More details to be provided regarding significant fissures within the cortex and their anatomical importance.

Brain Cutting Techniques

  • Various tools (e.g., scalpels, medical-grade appliances) are used in brain dissection, particularly in advanced courses such as neuroscience.