The Brain

The Brain

Development Stages

• Begins as a neural tube.

• 4th week: Primary vesicles.

• 5th week: Formation of secondary vesicles.

Brain Divisions

• Telencephalon: Cortices and Basal Ganglia.

• Diencephalon: Thalamus.

• Mesencephalon: Midbrain.

• Metencephalon: Pons and Cerebellum.

• Myelencephalon: Medulla Oblongata.

Ventricles

• Purpose: Keep the brain afloat and cushioned.

• Includes:

  • Foramen of Monro

  • Aqueduct of Sylvius

Ventricle Problems

• Hydrocephalus: 1/2 in 1000 children in the U.S.

  • Treatment via shunts (50% success) and possible surgery.

  • Normal pressure hydrocephalus (NPH): Often misdiagnosed in older adults, treatable for full recovery.

Cerebrospinal Fluid (CSF)

• Characteristics: Clear fluid formed from blood.

• Formation Source: Choroid plexus.

• CSF Pathway: Formed, circulates, and is reabsorbed via arachnoid villi to return to bloodstream.

• Additional function: Waste removal.

CSF Problems

• Causes include connective tissue disorders (Marfan's, Ehlers-Danlos) and intracranial hypertension.

Blood-Brain Barrier (BBB)

• Tight regulation of ion/molecule movement necessary for stable brain environment.

• Passed Substances: Glucose, O2, H2O, CO2, amino acids, lipid-soluble substances.

• Banned Substances: Creatinine, urea, Na+, Cl-, K+, proteins, some toxins.

Chemicals Affecting the BBB

• Toxic Elements: Lead (28-30days), mercury (30-60 days), aluminum (with varying half-lives).

Blood Supply to the Brain

• Key arteries include:

  • Anterior Cerebral, Internal Carotid, Middle Cerebral, Basilar, and Vertebral arteries.

Stroke Types

• Hemorrhagic Stroke: Rupture of blood vessel.

• Ischemic Stroke: Obstruction due to clot.

Brain Structures by Lobe

• Frontal Lobe: Reasoning, planning, speech production, executive functions.

• Parietal Lobe: Sensory processing, reading, arithmetic.

• Temporal Lobe: Hearing, memory processing.

• Occipital Lobe: Visual processing.

Critical Areas

• Wernicke’s Area: Speech comprehension; damage leads to aphasia.

• Broca’s Area: Speech production; damage causes Broca’s aphasia.

Cerebrum Composition

• Comprised of white matter for transmission, includes:

  • Projection Tracts, Commissural Tracts, Association Tracts.

Brain Stem Components

• Parts: Midbrain, Pons, Medulla Oblongata.

  • Midbrain:

  • Pons: sensation of pain from anywhere in your body below your neck

  • Oblongata: respiration, heart rate, and blood vessels diameter

Cerebellum Function

• Regulates muscle tone, posture, balance; dysfunction leads to gait disorders.

  • What kind of gait would be seen?

Meninges

• Three protective layers surrounding CNS:

  • Dura Mater: Tough outer layer.

  • Arachnoid Mater: Web-like middle layer.

  • Pia Mater: Innermost layer closely attached to the brain.

Meningitis

• Serious inflammation usually due to infection; symptoms include fever, headache, stiffness.

  • Starts with invasion of the nose either by bacteria or a virus (herepes, HIV,

Subdural Hematoma

Intracranial Hemorrhages

• Include subdural, epidural, and subarachnoid types; potentially fatal.

• 40%-50% mortality rate

Brain Tumors

• Types include primary (originating in the brain) and metastatic (spreading from other areas).

Concussion Details

• Types of traumatic brain injury:

  • Direct impact, acceleration-deceleration, blast injury.

• Recovery: 80% resolve, average 10 days.