Biol 2010 Chapter 12 Part 1

Chapter 1: Introduction to the Central Nervous System

  • Central Nervous System (CNS) Overview

    • Comprised of the brain and spinal cord.

  • Brain Composition

    • Approximately 100 billion neurons.

    • Male brain weight: ~1.6 kg; Female brain weight: ~1.45 kg.

    • Brain size proportional to body size, larger in males.

    • Brain weight or neuron count does NOT determine intelligence.

      • Example: Elephants have more neurons but are not considered more intelligent than humans.

    • Intelligence linked to the number and complexity of synaptic connections between neurons.

  • Brain Structure

    • Divided into hemispheres and lobes.

    • Cerebral Hemispheres (Cerebrum)

      • Two hemispheres, right and left.

    • Diencephalon

      • Made up of:

        • Thalamus

        • Hypothalamus

        • Epithalamus

    • Brainstem: Composed of:

      • Midbrain

      • Pons

      • Medulla Oblongata

    • Cerebellum: Beneath the cerebrum and behind the brainstem.

  • Gray and White Matter

    • Gray Matter: Cell bodies, unmyelinated processes (dendrites, axons).

    • White Matter: Myelinated axons.

      • Distribution varies throughout the brain:

        • Cerebral cortex: Gray matter superficial (outer layer), white matter deep.

        • Brainstem: Gray and white matter throughout.

        • Spinal cord: Gray matter in center, white matter on outer edge.

  • Cerebrospinal Fluid (CSF)

    • Found in fluid-filled cavities called ventricles.

    • Ventricles include:

      • Lateral ventricles (C-shaped)

      • 3rd ventricle (vertical)

      • Cerebral aqueduct (connects 3rd and 4th ventricles)

      • 4th ventricle and subsequent apertures for CSF circulation.

Chapter 2: Lobes of the Brain

  • Cerebral Hemispheres Structure

    • Make up ~80% of brain mass, featuring folds (gyri) and grooves (sulci).

    • Key Sulci:

      • Central sulcus: Divides frontal and parietal lobes.

      • Lateral sulcus: Divides temporal lobe from frontal and parietal lobes.

      • Parieto-occipital sulcus: Separates parietal lobe from occipital lobe.

    • Major Lobes of the Brain:

      1. Frontal Lobe

      2. Parietal Lobe

      3. Temporal Lobe

      4. Occipital Lobe

      5. Insula (located within the lateral sulcus).

  • Cerebral Cortex

    • Thin layer (2-4 mm) of gray matter responsible for consciousness, thoughts, and sensory processing.

    • Increased surface area due to folds allows for more neurons and complexity.

Chapter 3: Areas of the Brain

  • Types of Brain Areas:

    • Motor Areas: Control voluntary movements.

      • Primary Motor Cortex: Located in precentral gyrus, crucial for skeletal muscle contraction.

        • Contains a homunculus map correlating neuron density to muscle control.

        • Right side of the primary motor cortex controls the left side of the body (contralateral control).

      • Premotor Cortex: Anterior to primary motor cortex, involved in learned, patterned movements, and planning.

  • Sensory Areas:

    • Primary Somatosensory Area: Located in postcentral gyrus; processes sensory information from the opposite side of the body (touch recognition).

      • Associated with a homunculus like the motor cortex.

    • Sensory Integration: Handled by the somatosensory association area, processing texture, memories, and stimulating recognition.

    • Visual Area: Located in the occipital lobe; receives input from eyes, processes visual stimuli, and lacks typical lateralization.

      • Visual information crosses at the optic chiasm.

    • Auditory Area: Located in temporal lobe, responsible for sound perception.

Chapter 4: Areas of the Brain Continued

  • Additional Motor Areas:

    • Broca's Area: Involved in speech production (often in the left hemisphere).

    • Frontal Eye Field: Manages voluntary eye movements.

  • Sensory Processing:

    • Auditory Association Area: Identifies sounds and their meanings.

    • Olfactory Cortex: Located in the temporal lobe, processes smell.

    • Multimodal Association Areas: Integrate sensory information for a holistic understanding of experiences.

      • Anterior Association Area (Prefrontal Cortex): Involved in intellect, learning, personality, and decision-making; slowly matures, affecting judgment.

      • Posterior Association Area: Recognizes patterns and localization.

Chapter 5: Auditory Association Area

  • Auditory Processing: Primary auditory cortex in temporal lobe detects volume and pitch, while auditory association area identifies sounds.

  • Limbic Association Area: Involves hippocampus and related structures for emotional and memory processing.

Chapter 6: Conclusion

  • Brain Lateralization:

    • Left hemisphere: Dominant for language, math, and logic in ~90% of people.

    • Right hemisphere: Dominates in creative skills, spatial orientation, emotions, and music appreciation.

    • Ambidextrous individuals may have atypical brain lateralization; dyslexia can occur through lateralization errors.

  • Types of White Matter Connections:

    • Commissural Fibers: Connect different hemispheres (e.g., corpus callosum).

    • Association Fibers: Connect regions within the same hemisphere.

    • Projection Fibers: Connect cortex to other CNS parts.

  • Final Note: Both hemispheres engage in activities, but one typically leads depending on task type. Questions and clarifications encouraged.