Chapter 13: Brain and Nervous System

Major Brain Regions

  • Four Major Regions
    1. Cerebrum
    2. Cerebellum
    3. Diencephalon
    4. Brainstem

Cerebrum

  • Hemispheres:

    • Left & Right cerebral hemispheres, separated by fissures.
    • Surface features include gyri (ridges) and sulci (grooves).

  • Cerebral Cortex:

    • Thin outer layer of gray matter.
    • Major Functions:
    • Conscious thought
    • Memory storage and processing
    • Sensory processing
    • Control of skeletal muscles

Cerebellum

  • Functions:
    • Coordinates complex movements
    • Maintains normal muscle tone
    • Regulates posture and balance

Diencephalon

  • Connects cerebral hemispheres to the rest of the CNS.
  • Components:
    1. Thalamus:
    • Sensory relay and processing
    1. Hypothalamus:
    • Emotions, autonomic functions, hormone production

Brainstem

  • Contains three parts:
    1. Midbrain: Visual and auditory processing
    2. Pons: Tracts and relay centers
    3. Medulla Oblongata: Relays sensory information and controls vital autonomic functions

Ventricles of the Brain

  • Function:

    • Protect brain and spinal cord, provide mechanical protection, homeostasis, and circulation.

  • Components:

    • Lateral ventricles, third ventricle, fourth ventricle.

  • Cerebrospinal Fluid (CSF):

    • Produced by choroid plexus in ventricles.
    • Functions include supporting brain weight, cushioning from trauma, and transporting nutrients and wastes.

Protection of the Brain

  • Cranial Meninges: Three protective layers.
    1. Dura mater
    2. Arachnoid mater
    3. Pia mater
  • Dural Folds:
    • Include falx cerebri, tentorium cerebelli
  • Cerebrospinal Fluid (CSF): As above.

Medulla Oblongata

  • Contains all ascending/descending tracts.

  • Centers:

    • Cardiovascular
    • Respiratory
    • Reflexes (e.g., vomiting, coughing)

  • Structural Features:

    • Pyramids (motor fibers) where fibers decussate (cross over).

Pons

  • Contains structures for relay and processing information.
  • Coordinates respiration and contains several cranial nerve nuclei.

Cerebellum Anatomy

  • Divided into anterior and posterior lobes.
  • Folia: Folds on the surface for increased surface area.
  • Cerebellar cortex: Contains thin gray matter.

Midbrain

  • Directs complex motor patterns at a subconscious level.
  • Functions:
    • Tracking moving objects
    • Reflexive movements in response to sound, influencing muscle control and arousal states.

Cranial Nerves

  • Identification and Functions:
    • Cranial nerves named and numbered. Functions include motor control, sensory input, and autonomic control.
  • Examples:
    • Olfactory (CN I): Smell
    • Optic (CN II): Vision
    • Oculomotor (CN III): Eye movement and pupil control
    • Vagus (CN X): Controls organs of thorax and abdomen

Sensory Pathways and Receptors

  • Receptors classified by modality:
    • General (somatic and visceral), special (taste, smell, vision, balance, hearing).
  • Sensory Pathway Function:
    • Sensation (information carried) vs. perception (awareness of sensation).

Nervous System Disorders

  • Common Disorders:
    • Referred Pain: Pain perceived from one area felt in another (e.g., heart attack pain in left arm).
    • Parkinson’s Disease: Involves damage to neurons, resulting in muscle rigidity.
    • Cerebral Palsy: Affects voluntary movement due to non-progressive motor dysfunction.
    • ALS: Affects motor neurons, leading to atrophy of associated muscles.
    • Alzheimer's Disease: Causes loss of higher-order cerebral functions.
    • Multiple Sclerosis: Demyelination affecting CNS, leading to a variety of impairments.

Functional Areas of the Cerebral Cortex

  • Motor Areas:
    • Primary motor cortex (movement initiation) and premotor cortex (learned movements).
  • Sensory Areas:
    • Primary and somatosensory association areas. Functional mapping through sensory homunculus.
  • Integrative Centers:
    • Handle complex functions, such as language and communication.

White Matter of Cerebral Hemispheres

  • Composition:
    • Connects regions within hemispheres and between hemispheres.
  • Types:
    • Association fibers (same hemisphere), commissural fibers (between hemispheres), and projection fibers (to/from brain).

Conclusion

  • Understanding the anatomy & functions of the brain is crucial for recognizing various disorders and their impacts on the nervous system. Each part of the brain has specialized functions that contribute to overall behavior and homeostasis.