Functions and Anatomy of the Brain

ANATOMY OF THE BRAIN

• Major Structures
  • Cortex
  • Cranium
  • Lobes:
  • Occipital Lobe
  • Parietal Lobe
  • Frontal Lobe
  • Temporal Lobe
  • Basal Ganglia
  • Brain Stem
  • Cerebellum
  • Dura Mater
  • Spinal Cord

FUNCTIONS OF THE BRAIN

• Recognizing and Integrating Sensations:
  • Process incoming sensations and store them (memory).
• Making Decisions
• Initiating Actions:
  • Involves behavior and emotions.
• Memory
• Center of Intellect

BLOOD SUPPLY

• Cerebral Arterial Circle (Circle of Willis):
  • Ring of blood vessels on the inferior surface.
  • Supplies arterial blood rich in oxygen and nutrients.
  • Vessels branch out and penetrate brain tissue.

OXYGEN AND GLUCOSE NEEDS

• The brain consumes 20% of the body's oxygen and glucose.
• Blood supply increases with neuronal activity.
• Without oxygen:
  • Neuronal function impaired after 1-2 minutes.
  • Cells die after 4 minutes.
• The brain stores little carbohydrate; continuous glucose supply is essential.
• Glucose deficiency:
  • Symptoms: confusion, dizziness, convulsions, unconsciousness.

BLOOD BRAIN BARRIER (BBB)

• Selective barrier that protects brain cells from pathogens and harmful substances.
• Brain injuries can compromise the BBB:
  • May prevent therapeutic substances from reaching brain cells.

MENINGES

• Protective Coverings:
  • Continuous with the spinal cord's meninges.
  • Layers:
  • Dura Mater
    • Superficial, tightly bound to internal cranium.
  • Arachnoid Mater
    • Intermediate layer with cerebrospinal fluid (CSF) absorption.
  • Pia Mater
    • Delicate layer closely applied to brain tissue.

CEREBROSPINAL FLUID (CSF)

• Clear liquid (80-150 mL) produced and reabsorbed at 20 mL/h.
• Components:
  • Contains glucose, proteins, ions.
• Functions:
  • Mechanical protection (brain floats in CSF).
  • Chemical protection (correct ionic concentrations).
  • Circulation (provides nutrients, removes waste).

VENTRICLES OF THE BRAIN

• Four CSF-filled cavities:
  • Two Lateral Ventricles
  • Third Ventricle (superior to hypothalamus).
  • Fourth Ventricle (between brain stem and cerebellum).
• Flow of CSF:
  • From lateral ventricles -> third ventricle -> fourth ventricle.
• Apertures open into subarachnoid space for nutrient flow.

HYDROCEPHALUS

• Condition known as "water on the brain".
• Blocked CSF reabsorption can lead to pressure on brain tissue.
• Treatment may involve neurosurgical drains.

BRAIN INJURIES

• Causes: displacement, intracranial pressure, infections, free radical damage.
• Types of injuries:
  • Concussion: temporary loss of consciousness.
  • Contusion: bruising of the brain.
  • Laceration: tearing with hematoma.

MAJOR PARTS OF THE BRAIN

• Cerebrum: Responsible for conscious thought, memory, and muscle contractions.
• Diencephalon: Contains thalamus (sensory relay) and hypothalamus (homeostasis).
• Brainstem: Includes medulla oblongata (visceral functions) and pons (relays sensory info).
• Cerebellum: Coordinates complex motor patterns and adjusts motor output.

THALAMUS & HYPOTHALAMUS

• Thalamus:
  • Relay station for sensory information.
  • Involved in emotions and cognition.
• Hypothalamus:
  • Regulates autonomic functions, emotion, hormone production, and circadian rhythms.

CEREBELLUM

• Compares intended movements to actual movements.
• Senses equilibrium.

CEREBRUM AND ITS LOBES

• Largest Brain Part:
  • Right and left hemispheres connected by corpus callosum.
  • Contains gray matter cortex and basal ganglia.
• Lobes:
  • Frontal, Parietal, Temporal, Occipital.

WHITE MATTER AND FIBER TRACTS

• Association Fibers: Connect gyri in the same hemisphere.
• Commissural Fibers: Connect corresponding gyri in opposite hemispheres.
• Projection Fibers: Ascending and descending tracts to/from other brain regions.

BASAL GANGLIA

• Control automatic movements.
• Damage can result in tremors or rigidity; linked to Parkinson’s disease.

LIMBIC SYSTEM

• Involved in emotional behavior and memory.
• Plays a role in pleasure and pain responses.

FUNCTIONAL AREAS OF THE CEREBRAL CORTEX

• Sensory Areas: Interpret sensory impulses.
• Motor Areas: Govern muscular movements.
• Association Areas: Integrative functions (memory, reasoning, etc.).

APHASIA

• Nonfluent Aphasia: Difficulty forming words (Broca’s area damage).
• Fluent Aphasia: Difficulty understanding or forming coherent speech (Wernicke’s area damage).

HEMISPHERIC LATERALIZATION

• Left hemisphere: crucial for speech, right-handed control.
• Right hemisphere: manages left-handed control; emotional expressions.

ELECTROENCEPHALOGRAM (EEG)

• Measures brain waves:
  • Alpha Waves: Resting, eyes closed.
  • Beta Waves: Intense mental activity.
  • Theta Waves: Stress/emotional events.
  • Delta Waves: Deep sleep.

CRANIAL NERVES

• A summary of cranial nerves, functions, and innervations is essential for understanding brain interactions and sensory/motor functions.

Example Overview of Some Cranial Nerves:

• Cranial Nerve I (Olfactory): Sense of smell.

• Cranial Nerve II (Optic): Vision.

• Cranial Nerve VIII (Vestibulocochlear): Hearing and balance.

• Cranial Nerve Summary:

  • Function: sensory, motor, or mixed.
  • Location: specific openings where they exit the skull to innervate respective areas.