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Lecture 17

Brain Structure Overview

  • The brain is divided into two large hemispheres: the left hemisphere and the right hemisphere.
  • The brain stem controls basic functions and connects the brain to the spinal cord.
  • The fissure is a distinct separation deep within the brain's structure.

Gray and White Matter

  • Gray matter: Refers to areas containing cell bodies of neurons (outermost portion, cerebral cortex).
  • White matter: Contains myelinated axons, acting as communication highways between different brain areas.
  • Significance of myelin: Insulates and speeds up action potentials.

Lobes of the Brain

  • Frontal Lobe: Most anterior, responsible for functions related to planning and movement (Motor Cortex).
  • Temporal Lobe: Located behind the frontal lobe, involved in hearing and smell processing.
  • Parietal Lobe: Integration of sensory information.
  • Occipital Lobe: Primarily responsible for vision.

Sensory and Motor Cortices

  • Anterior to the central sulcus: Motor Cortex controlling voluntary movements.
  • Posterior to the central sulcus: Sensory Cortex where sensory information is processed (smell, taste, etc.).
  • Each hemisphere controls the opposite side of the body (contralateral).

Left vs. Right Brain Functionality

  • Left hemisphere: Generally associated with logical tasks (math, language, logic).
  • Right hemisphere: Associated with creative tasks (art, music, emotional processing).
  • Brain communication: Both hemispheres communicate through interconnecting structures.

Basal Nuclei

  • Collections of gray matter within the brain responsible for processing and sorting sensory information.
  • Parkinson’s disease affects this region, causing difficulties in sensory processing and movement.

Thalamus and Hypothalamus

  • Thalamus: Acts as relay station for sensory signals and emotions.
  • Hypothalamus: Regulates autonomic functions and emotional responses.
    • Plays key role in body temperature, hunger, and hormones with its connection to the pituitary gland.

Cerebellum

  • Located at the back of the brain, controlling smooth and coordinated movements and also contributes to motor learning and memory.
  • Contains its own choroid plexus for CSF production.

Meninges

  • Three layers protecting the brain:
    • Dura Mater: Outer layer, thick and protective.
    • Arachnoid Mater: Middle layer, covering major blood vessels.
    • Pia Mater: Innermost layer that closely wraps the brain.
  • Subdural space and subarachnoid space: Fluid-filled areas critical for CSF circulation.

Cerebrospinal Fluid (CSF) Circulation

  • Formed in the choroid plexus, primarily in the diencephalon region.
  • Flows through left and right lateral ventricles, then to the third and fourth ventricles.
  • Enters subarachnoid space, circulates around the spinal cord and brain before being reabsorbed into blood.
  • Ciliated cells assist in the flow of CSF.

Brainstem

  • Made up of three regions: midbrain, pons, and medulla oblongata.
  • Controls basic autonomic functions such as breathing and heart rate.

Clinical Applications

  • Meningitis: Inflammation of the meninges, can be caused by bacterial or viral infections.
  • Hydrocephalus: Blockage in CSF flow leading to increased intracranial pressure.
  • Concussions: Brain jostled within the skull, risking damage to neurons.
  • Stroke: Can lead to brain damage by affecting blood flow.
  • Alzheimer's disease: Involves tau protein tangling, affecting neuronal function and health.