Biological Psychology

Early Conceptualizations of Neurology

• Franz Gall and Phrenology:

  • An early, albeit erroneous, attempt to link personality, behavior, and functioning to specific brain regions.

  • Proposed 31 personality "areas" based on bumps, contours, and general surface locations on the cranium.

  • Believed these surface features reflected underlying brain development and, consequently, individual traits.

Fundamentals of the Nervous System

• The nervous system is composed of specialized cells called neurons.

• Key components of a neuron:

  • Soma (Cell Body): The main part of the neuron, containing the nucleus.

  • Dendrites: Branch-like extensions that act as receivers, gathering incoming signals from other neurons.

  • Axon: A long, slender fiber that functions as the conducting fiber, transmitting electrical impulses away from the cell body.

  • Myelin Sheath: An insulating fatty layer that covers the axon, significantly speeding up the transmission of electrical signals.

    • Produced by Schwann's Cells.

  • Nodes of Ranvier: Gaps in the myelin sheath, where the electrical signal is regenerated.

  • Terminal Buttons (Axon Terminals): The very end of the axon, which function as transmitters by releasing neurotransmitters.

• Nerve: A bundle of nerve fibers (axons).

The Synapse

• The point of communication between two neurons.

• Components of a Synapse:

  • Axon Terminal (Presynaptic Neuron): The end of the transmitting neuron.

    • Contains Synaptic Vesicles which store neurotransmitters.

    • Mitochondrion provide ATP (energy) for processes like neurotransmitter synthesis and release.

  • Presynaptic Membrane: The membrane of the axon terminal where neurotransmitters are released by exocytosis.

  • Synaptic Cleft/Gap: The small space between the presynaptic and postsynaptic neurons.

  • Postsynaptic Membrane: The membrane of the dendrite (or cell body) of the receiving neuron.

    • Contains receptors specifically designed to bind with neurotransmitters.

Neurotransmitters

• Chemical messengers that transmit signals across the synaptic cleft.

• Key Neurotransmitters and their functions:

  • Acetylcholine:

    • Functions between neurons and muscles.

    • Involved in actions like walking and talking.

  • Monoamines:

    • Dopamine: Crucial for voluntary movement and processing pleasurable emotions.

    • Norepinephrine: Influences mood and arousal.

    • Serotonin: Regulates sleep, wakefulness, eating, and aggression.

Agonists and Antagonists

• Agonist:

  • A chemical substance that mimics the action of a neurotransmitter by binding to its receptors and producing a similar effect.

  • Example: Methadone acts as an agonist for opioid receptors, used in treating Opioid Use Disorder.

• Antagonist:

  • A chemical substance that blocks or opposes the action of a neurotransmitter by binding to its receptors without activating them, thus preventing the natural neurotransmitter from binding.

  • Example: Naltrexone (commercial name "Narcan") acts as an antagonist for opioid receptors, used to reverse opioid overdose.

Neurotransmitter Process Overview

1. Neurotransmitters are stored in vesicles within the axon terminal.

2. Upon an electrical signal, neurotransmitters are released into the synapse.

3. They attach to receptors on the dendrite of the postsynaptic neuron.

4. After transmitting the signal, neurotransmitters are either destroyed by enzymes in the synapse or reabsorbed by the presynaptic neuron (reuptake) to clear the synaptic cleft.

The Nervous System: Divisions

• Central Nervous System (CNS):

  • Consists of the Brain and Spinal Cord.

  • The command center of the body.

• Peripheral Nervous System (PNS):

  • Compromises all nerves outside the CNS.

  • Divided into:

    • Somatic Motor Nervous System: Responsible for voluntary movements, connecting the CNS to skeletal muscles.

    • Autonomic Nervous System: Regulates involuntary functions (e.g., heart rate, digestion, breathing).

Brain Anatomy: Major Regions and Functions

• Hindbrain: The oldest part of the brain, at the base.

  • Reticular Formation: Involved in sleep and arousal.

  • Cerebellum: Critical for balance and fine muscle movement.

  • Medulla and Pons (lower brain stem): Primarily controls unconscious functions such as breathing and circulation.

• Midbrain: A segment situated between the hindbrain and forebrain.

  • Includes a portion of the Reticular Formation.

• Forebrain: The largest and most complex part of the brain, responsible for higher-order functions.

  • Thalamus: Serves as a relay center for most sensory information (except smell) to the cerebral cortex.

  • Hypothalamus: Regulates crucial biological needs like hunger, thirst, and body temperature.

  • Cerebrum: The largest part of the brain, responsible for higher order functions including sensing, thinking, learning, emotion, and consciousness.

  • Corpus Callosum: A thick band of nerve fibers that acts as a relay center for the two "sides" (hemispheres) of the brain, allowing them to communicate.

• Limbic System: A group of structures typically associated with emotion, motivation, and memory (not explicitly detailed, but labeled in diagram).

Cerebral Lobes and Cortices

• Frontal Lobe: Involved in planning, decision-making, voluntary movement, and personality.

  • Motor Cortex (Motor Strip): Controls voluntary movements.

  • Broca’s Area: Located in the left hemisphere, essential for speech production.

• Parietal Lobe: Processes sensory information, including touch, temperature, pain, and spatial awareness.

  • Sensory Cortex (Sensory Strip): Receives and processes tactile information from the body.

• Temporal Lobe: Involved in processing auditory information, memory, and language comprehension.

  • Primary Auditory Cortex: Processes sound.

  • Wernicke’s Area: Located in the left hemisphere, crucial for language comprehension.

• Occipital Lobe: Primarily responsible for processing visual information.

Hemispheric Lateralization

• The specialization of certain cognitive functions to one side of the brain, although capabilities can be affected by various factors.

• Left Hemisphere (typically associated with):

  • Verbal processing and skills.

  • Speech, reading, and writing.

• Right Hemisphere (typically associated with):

  • Spatial abilities.

  • Musicality.

  • Visual recognition.

Bisection of the Corpus Callosum

• A medical procedure performed to reduce severe epileptic seizures.

• Can interfere with visual and mental processing due to impaired communication between the two hemispheres.

Examples of Organic Brain Damage ("Organicity")

• Damage to the brain caused by physical, chemical, or physiological factors.

• Causes include:

  • Closed head injury: Trauma where the skull is not penetrated.

  • Severe head trauma: Accidents or other misadventures leading to significant brain injury.

  • Severe alcohol damage: Can lead to conditions like Korsakoff’s syndrome.

  • "Neuro-toxic" drugs: Substances like Methamphetamine that cause damage to brain cells.

Korsakoff’s Syndrome

• A severe neurological disorder resulting from a gross lack of thiamine (Vitamin B1).

• Primary Cause: Typically, severe, chronic, and heavy use of alcohol, which impairs thiamine absorption and leads to malnutrition.

• Symptoms include:

  • Ataxia: Loss of muscle coordination and extra-pyramidal control (involuntary movements).

  • Extra-pyramidal motor tremors: Involuntary shaking or trembling movements.

  • Paralysis of eye muscles.

  • Profound memory loss, particularly for new information (anterograde amnesia).

  • Confabulation: The creation of false or distorted memories without the intention to deceive, often to fill in memory gaps.

  • Apathy: A lack of interest, enthusiasm, or concern.

  • Lack of insight during conversations.

  • Can progress to a coma in severe cases.