Biological Basis of the Mind

Biological Basis of the Mind

Introduction to Biopsychology

  • "To be learning about the neurosciences now is like studying world geography while Magellan was exploring the seas. This truly is the golden age of brain science." (from textbook)

  • This section offers a foundational understanding of physiological psychology and neuroscience, a requirement for psychology majors.

  • Fundamental Biological Nature:

    • Every thought, emotion, action, and inspiration is fundamentally linked to electrical impulses—specifically, thousands or millions of coordinated neural firings.

    • Example: Love, at a biological level, is a complex sequence of coordinated neural firings across the body. If the underlying biological mechanisms fail, the experience of love cannot manifest.

  • Electrical Nature:

    • Neural firings are characterized as tiny blasts of electricity.

    • Billions of these electrical impulses are constantly occurring throughout the body.

    • Poetic summary: "Roses are red, Violets are blue, Love is just neurons, All firing through you."

Neural Systems: The Neuron

  • Neurons:

    • Basic building blocks of the nervous system, including the brain.

    • Form a vast and intricate communication system.

  • Structure of a Neuron:

    • Dendrites: Branch-like extensions that receive messages from other neurons and transmit them towards the cell nucleus.

    • Axon: A long, slender extension of the neuron that conducts messages away from the cell body to other neurons, muscles, or glands.

    • Myelin Sheath: Fatty cells that insulate and protect axon fibers, significantly increasing the speed at which messages are transmitted.

  • Action Potential:

    • An electrical impulse that travels down an axon.

    • Triggering an Action Potential: Signals from other nerves must push the cell past an "excitation threshold" for it to fire.

    • "All or None" Principle: Analogous to a gun; a neuron either fires completely or it does not fire at all. The strength of the electrical current produced during an action potential is always the same.

    • Intensity of Reaction: Since neurons fire at the same strength, the intensity of a reaction (e.g., a tear vs. a crying fit) is determined by two factors:

      1. The number of cells firing in a specific region.

      2. The frequency of firing of any given cell.

  • Neural Communication: Neurons do not physically touch each other.

Mechanisms of Neural Communication: Synapses and Neurotransmitters

  • Process:

    • Action potentials cause the release of chemical messengers called neurotransmitters.

    • These neurotransmitters travel across tiny gaps called synaptic gaps to specialized junctions called synapses.

    • After delivering their message, neurotransmitters are typically reabsorbed back into the axon terminal in a process called reuptake.

  • Key Neurotransmitters:

    • Endorphins:

      • Natural opiates produced by the body (meaning "endogenous morphine").

      • Released during activities such as sex, exercise, and in response to pain.

    • Serotonin: Linked to mood regulation; low levels are associated with depression.

    • Dopamine: Involved in emotions, motivation, and the brain's reward system.

    • Epinephrine (Adrenaline): Controls arousal and alertness; also known as "adrenaline."

    • Norepinephrine: Similar to epinephrine; plays a role in arousal and alertness.

    • Acetylcholine: Crucial for processes related to learning and memory.

Types of Neurons

  • Interneurons: Serve as relay stations, facilitating communication between sensory and motor neurons within the central nervous system.

  • Sensory Neurons (Afferent Neurons): Transmit sensory information (e.g., touch, sight, sound) from sensory receptors to the central nervous system.

  • Motor Neurons (Efferent Neurons): Carry information and commands from the central nervous system to muscles and glands, initiating movement and other physical responses.

The Nervous System

  • Central Nervous System (CNS): Comprises the brain and the spinal cord.

  • Peripheral Nervous System (PNS): Consists of all nerves extending throughout the rest of the body outside the CNS. It is divided into two main components:

    • Somatic System: Controls voluntary muscular movements (e.g., moving an arm).

    • Autonomic System: Regulates involuntary movements and functions (e.g., heartbeat, respiration, digestion, organ activity).

  • The peripheral nervous system communicates with the central nervous system through the spinal cord.

  • Speed of Communication: Electronic communication via neurons is fast, but it is considerably slower than electronic conduction through a wire.

Class Exercise: Investigating Neural Transmission Speed

  • Experiment Design: Participants formed a line and were instructed to squeeze the shoulder or ankle of the person next to them upon feeling a squeeze, with the last person raising their hand to indicate completion, allowing for timing.

  • Condition 1: Shoulder Squeeze:

    • Participants squeezed the shoulder.

    • Timed response.

  • Condition 2: Ankle Squeeze:

    • Participants squeezed the ankle.

    • Prediction: The ankle squeeze was predicted to be slower.

    • Result & Explanation: The ankle squeeze was indeed slower than the shoulder squeeze.

      • This difference in speed is due to the longer distance nerve impulses from the ankle must travel to reach the spinal cord and then the brain, compared to impulses from the shoulder.

  • Nervous System Areas Involved:

    • The exercise primarily involved the Peripheral Nervous System.

    • Specifically, the Somatic System of the PNS was invoked because it concerned voluntary motor actions.

Autonomic Nervous System Subdivision

  • The autonomic system is further divided into two functionally opposing systems:

    • Sympathetic Nervous System: Responsible for arousal, mobilizing the body for action, and preparing it for 'fight or flight' responses.

    • Parasympathetic Nervous System: Responsible for calming the body, conserving energy, and returning the body to a relaxed state ('rest and digest').

    • These two systems produce opposite effects to maintain physiological balance.

Reflexes

  • Definition: Automatic, involuntary responses to sensory stimuli that do not require conscious thought or brain processing for the initial reaction.

    • Examples: Blinking eyes when air blows on them, rapidly retracting a finger from a hot surface.

  • Mechanism: Sensory information travels to the spinal cord, and then immediately activates motor neurons. The brain is not necessary for the immediate reflexive action.

  • Brain's Role: While the immediate reflex occurs without brain involvement, the sensory information eventually reaches the brain, often after the reflexive action has already taken place (e.g., you move your finger before you consciously feel the pain).

Endocrine System

  • Interaction with Neural Systems: The endocrine system works in conjunction with neural systems and the brain to regulate various bodily functions.

  • Mechanism: It delivers hormones throughout the body via the bloodstream.

  • Similarities to Neurotransmitters:

    • Hormones are chemical messengers.

    • They bind to specific receptors, leading to physiological changes.

    • Some hormones are chemically identical to their neurotransmitter counterparts (e.g., epinephrine acts as both a neurotransmitter and a hormone).

  • Differences from Neurotransmitters:

    • Vehicle: Hormones travel through the bloodstream, whereas neurotransmitters communicate across neural synapses.

    • Speed and Duration: Hormones work more slowly and have a slower dissipation rate compared to neurotransmitters. For example, the lingering feelings of anger (flush to the face, increased heart rate) after the source of anger is gone are due to the slower action and dissipation of hormones.

  • Key Hormones:

    • Testosterone: Linked to aggression and dominance. Present in much higher amounts in men but also found in women.

    • Oxytocin: Known as the "social bonding hormone." Studies show that administering oxytocin can increase trust in others.

    • Cortisol: A primary stress hormone. Levels of stress can be determined by measuring cortisol in saliva or hair.

    • Epinephrine: Also a neurotransmitter. Plays a significant role in stress response and is part of triggering the sympathetic nervous system.

Learning Diary Prompt

  • Students are encouraged to consider a developmental or social problem and design a study utilizing biological markers and behavioral measures. This exercise aims to explore what biological markers add to understanding such problems and identify scenarios where their use might not be beneficial.