MCAT Behavioral Science: Biology and Behavior (Chapter 1)

Overview

• Chapter Title: Biology and Behavior
• Based on: Kaplan book
• Objectives:
  1. History of Neuropsychology
  2. Organization of the Human Nervous System
  3. Organization of the Brain
  4. Focus on the Forebrain
  5. Influences on Behavior
  6. Development Process

Objective 1: History of Neuropsychology

• 19th Century: Shift from philosophical to empirical/scientific study of behavior.
• Key Figures:*
  • Franz Gall (1758-1828): Developed phrenology; debunked but spurred research.
  • Pierre Flourens: Studied brain functions via extirpation in animals; found specific brain parts had specific functions.
  • William James: Father of American psychology, pioneered functionalism.
  • John Dewey: Criticized reflex arc, advocated for studying the organism as a whole.
  • Paul Broca: Linked specific functional impairments to specific brain lesions; discovered Broca’s area.
  • Hermann von Helmholtz: Measured speed of nerve impulses; helped transition psychology to natural sciences.
  • Sir Charles Sherrington: Inferred existence of synapses; believed synaptic transmission was electrical, but it's chemical.

Objective 2: Organization of the Human Nervous System

• Nerve Cell Types:

  • Sensory Neurons (Afferent): Transmit sensory info to brain/spinal cord.
  • Motor Neurons (Efferent): Transmit motor info to muscles/glands.
  • Interneurons: Most numerous; link neurons, often involved in reflexive behavior.

• Example: Stepping on a Lego—reflexive arc (interneurons in spinal cord) causes immediate reaction before brain processes pain.

• Nervous System Divisions:

  • Central Nervous System (CNS): Brain and spinal cord.
  • Peripheral Nervous System (PNS): Nerve tissue and fibers outside CNS; includes 31 spinal and 10 of 12 cranial nerve pairs.
    • Somatic Nervous System: Sensory and motor neurons in skin, joints, muscles.
    • Autonomic Nervous System (ANS): Regulates involuntary functions (heartbeat, respiration, digestion, etc.).
      • Sympathetic Nervous System: Fight or flight; increases heart rate, dilates pupils, inhibits digestion, etc.
      • Parasympathetic Nervous System: Rest and digest; reduces heart rate, constricts bronchi, stimulates digestion, etc.

Objective 3: Organization of the Brain

• Brain Divisions: Hindbrain, midbrain, forebrain.
• Meninges: Protective connective tissue covering the brain.
  • Layers: Dura mater, arachnoid mater, pia mater.
  • Cerebrospinal Fluid: Cushions the brain, produced in ventricles.
• Functional Correlation: Basic survival functions = base of the brain; complex functions = higher regions.

Hindbrain (Rhombencephalon)

• Functions: Vital processes (breathing, digestion, motor coordination).
• Divisions during Development:
  • Myelencephalon: Forms medulla oblongata (vital functions).
  • Metencephalon: Forms pons (sensory/motor pathways) and cerebellum (posture, balance, movement).

Midbrain (Mesencephalon)

• Functions: Sensory/motor information, involuntary reflexes.
• Key Structures:
  • Superior Colliculi: Visual input.
  • Inferior Colliculi: Auditory input.

Forebrain (Prosencephalon)

• Functions: Complex behaviors, emotion, memory.
• Divisions during Development:
  • Telencephalon: Cerebral cortex, basal ganglia, limbic system.
  • Diencephalon: Thalamus, hypothalamus, posterior pituitary, pineal gland.

Methods of Mapping the Brain

• Lesion Studies: Study impaired brain regions in animals/humans.
• Electrical Stimulation: Create cortical maps, stimulate deeper brain regions (study corresponding responses).
• Recording Brain Activity:
  • Electrodes: Record electrical activity in individual neurons.
  • EEG: Noninvasive, records electrical patterns, widely used in sleep, seizure studies.

Next Steps

• Upcoming: Detailed exploration of the forebrain (Chapter 1, Objective 4).