Biology of Mind Study Notes

Chapter 2: The Biology of the Mind

This chapter explores the biological foundation of behavior, integrating psychology and biology.

Introduction to Biological Basis of Mind

• Case Study of a Teacher: In 2000, a teacher exhibited uncontrollable sexual impulses linked to a brain tumor located behind his right temple. After the tumor was surgically removed, his sexual urges receded but returned with tumor regrowth. This case exemplifies the relationship between biological factors and psychological behavior.

• Philosophical Context: The chapter asserts that one cannot have a mind without a brain, emphasizing the connection between biological processes and psychological phenomena. It reflects on historical beliefs about the mind’s location, contrasting Plato's and Aristotle's views with contemporary science.

Why Psychology is Concerned with Human Biology

• Biological Influence: Every idea, mood, and impulse is a biological event influenced by genes, the brain, and physical state.

• Understanding the Mind: Insights into the biology of the mind have advanced significantly, illustrating the interplay of biological events and psychological states.

• Phrenology and Localization of Function: Initially proposed by Franz Gall, phrenology focused on skull bumps to determine mental abilities, leading to the concept of localized brain functions. Phrenology is now outdated but sparked interest in how various brain regions serve multiple functions.

Neural Communication

Neurons: Building Blocks of the Nervous System

• Definition of Neuron: Neurons are the basic cellular units of the nervous system. They have:

  • Dendrites: Receive messages

  • Axon: Transmits messages away from the cell body

  • Myelin Sheath: Insulates the axon to speed impulse transmission.

Action Potential

• Description: An action potential is a brief electrical charge that travels down an axon, enabling the neuron to communicate. Its speed can vary, but generally, neuron impulses travel much slower than electricity through a wire.

• Mechanics of Action Potential:

  • Resting Potential: The state of readiness with a negative ionic charge inside the neuron.

  • Depolarization: When stimulated, sodium ions rush in, causing the neuron to fire.

  • Refractory Period: The time it takes for the neuron to return to a resting state before it can fire again.

Communication Between Neurons

Synapses

• Synaptic Gap: The junction between the axon terminal of one neuron and the dendrite of another.

• Neurotransmitters: Chemical messengers released during synaptic transmission that bind to receptor sites on neighboring neurons, influencing their likelihood to fire.

Neurotransmitters and Behavior

• Key Neurotransmitters:

  • Acetylcholine (ACh): Involved in muscle movement and memory.

  • Dopamine: Linked to movement, emotion, and pleasure.

  • Serotonin: Influences mood and sleep.

  • Norepinephrine: Controls alertness and energy levels.

• Implications of Neurotransmitter Activity: Certain neurotransmitters can affect our mental states and are linked to various psychological disorders. Drugs can either enhance or inhibit neurotransmitter activity.

The Nervous System

Structure Overview

• Components:

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

  • Peripheral Nervous System (PNS): Sensory and motor neurons that branch out to the rest of the body.

• Neurons in the PNS: Sensory neurons (carry messages to the CNS), motor neurons (carry messages from the CNS), and interneurons (process information within the CNS).

Divisions of the Nervous System

• Somatic Nervous System: Controls voluntary muscle movements.

• Autonomic Nervous System (ANS): Regulates involuntary functions. Divided into sympathetic (activating) and parasympathetic (calming) systems.

The Endocrine System

• Functionality: The endocrine system is slower than the nervous system, using hormones to communicate effects that may last longer than neural messages.

• Glands: Major glands include the pituitary (master gland), adrenal glands, thyroid, and reproductive glands.

• Interactions with CNS: Hormones released can significantly influence emotions, motivations, and behaviors, showing the interdependence of the nervous and endocrine systems.

The Brain Structures

Brainstem and Basic Functions

• Brainstem: Responsible for autonomic life functions (breathing, heartbeat).

• Thalamus and Cerebellum: Thalamus relays sensory information; cerebellum coordinates voluntary movement and balance.

Limbic System: Emotion and Drives

• Structures:

  • Amygdala: Plays a role in fear and aggression.

  • Hippocampus: Important for memory processing.

  • Hypothalamus: Governs bodily maintenance activities and links the nervous and endocrine systems.

The Cerebral Cortex

Structure and Function

• Cerebrum: Consists of two hemispheres and four lobes (frontal, parietal, occipital, and temporal).

• Motor and Sensory Cortices: Areas dedicated to producing movement and receiving sensory input, respectively.

• Association Areas: Involved in higher cognitive functions—interpreting information, planning, decision-making.

Brain Plasticity and Neurogenesis

• Plasticity: The brain's capacity to reorganize and adapt when damaged, particularly pronounced in young individuals.

• Neurogenesis: The process of forming new neurons, which may become crucial for recovery from brain injuries.

Divided Brain: Functions of Hemispheres

Split Brain Studies

• Importance: Research on split brain patients (those who underwent corpus callosotomy) reveals lateralization of function, leading to insights about the specializations of each hemisphere.

• Left Hemisphere: Handles language processing, logical reasoning.

• Right Hemisphere: Better at visual-spatial tasks, creativity and holistic thought.

Conclusion

• Mind-Brain Relationship: Everything psychological is simultaneously biological. As neuroscience progresses, understanding the links between brain structures, neurotransmitters, and psychological processes is vital to psychology.

Key Terms and Concepts

• Neuron

• Dendrites

• Axon

• Synapse

• Neurotransmitter

• Endocrine

• Hemispheric Specialization

• Brain Plasticity

• Neurogenesis

• Lateralization

Chapter 2: The Biology of the Mind

This chapter explores the biological foundation of behavior, integrating psychology and biology through the lens of biopsychology.

Introduction to Biological Basis of Mind

• The Biopsychosocial Approach: To understand behavior, psychologists study how biological, psychological, and social-cultural factors interact. This chapter focuses on the biological component—everything psychological is simultaneously biological.

• Case Study of a Teacher: In 2000, a teacher exhibited uncontrollable sexual impulses linked to a brain tumor located behind his right temple. After the tumor was surgically removed, his sexual urges receded but returned with tumor regrowth. This case illustrates that brain structure directly influences personality and behavior.

• Philosophical Context:

  • Plato: Located the mind in the spherical head.

  • Aristotle: Believed the mind was in the heart.

  • Contemporary Science: Affirms the mind is what the brain does.

Why Psychology is Concerned with Human Biology

• Biological Influence: Every idea, mood, and impulse is a biological event influenced by genes, the brain, and physical state.

• Phrenology and Localization of Function: Proposed by Franz Gall, phrenology suggested bumps on the skull represented mental abilities. While the methodology was flawed, it correctly anticipated the concept of localization of function—the idea that various brain regions have particular functions.

Neural Communication

Neurons: Building Blocks of the Nervous System

• Structure of a Neuron:

  • Cell Body (Soma): The cell's life-support center.

  • Dendrites: Fibers that receive messages from other cells.

  • Axon: Passes messages away from the cell body to other neurons, muscles, or glands.

  • Myelin Sheath: A fatty tissue layer segmentally encasing the axons; it increases transmission speed. Damage to this leads to Multiple Sclerosis ($MS$).

  • Terminal Branches: Form junctions with other cells.

Action Potential

• Description: A neural impulse; a brief electrical charge that travels down an axon. The speed ranges from $2$ to $180$ mph.

• Mechanics of Action Potential:

  • Resting Potential: The fluid outside an axon’s membrane has mostly positively charged sodium ($Na^+$) ions; a resting axon’s fluid interior has mostly negatively charged ions. This state is called polarization.

  • Threshold: The level of stimulation required to trigger a neural impulse. Neurons follow an all-or-none response; they either fire or they don't.

  • Depolarization: When a neuron fires, the first section of the axon opens, and positively charged sodium ions flood through the membrane.

  • Refractory Period: A period of inactivity after a neuron has fired, during which the neuron pumps the positively charged sodium ions back outside.

Communication Between Neurons

Synapses

• Synaptic Gap: The tiny gap ($less than 1$ millionth of an inch wide) at the junction between neurons.

• Neurotransmitters: Chemical messengers that cross the synaptic gaps. When released by the sending neuron, they travel across the synapse and bind to receptor sites on the receiving neuron, like a lock and key.

• Reuptake: The sending neuron reabsorbs the excess neurotransmitter molecules.

Neurotransmitters and Behavior

• Key Neurotransmitters:

  • Acetylcholine (ACh): Enables muscle action, learning, and memory. With Alzheimer’s disease, $ACh$-producing neurons deteriorate.

  • Dopamine: Influences movement, learning, attention, and emotion. Oversupply linked to schizophrenia; undersupply linked to Parkinson’s disease.

  • Serotonin: Affects mood, hunger, sleep, and arousal. Undersupply linked to depression.

  • Endorphins: ‘Morphine within’—natural, opiate-like neurotransmitters linked to pain control and to pleasure.

  • GABA (gamma-aminobutyric acid): A major inhibitory neurotransmitter.

  • Glutamate: A major excitatory neurotransmitter involved in memory.

• Drugs and Chemicals:

  • Agonists: Molecules that increase a neurotransmitter's action.

  • Antagonists: Molecules that inhibit or block a neurotransmitter's action.

The Nervous System

Structure Overview

• Central Nervous System (CNS): The brain and spinal cord; the body's decision maker.

• Peripheral Nervous System (PNS): Responsible for gathering information and for transmitting $CNS$ decisions to other body parts.

  • Sensory (Afferent) Neurons: Carry incoming information from sensory receptors to the $CNS$.

  • Motor (Efferent) Neurons: Carry outgoing information from the $CNS$ to muscles and glands.

  • Interneurons: Within the $CNS$; communicate internally and process information between sensory inputs and motor outputs.

Divisions of the Peripheral Nervous System

• Somatic Nervous System: Enables voluntary control of our skeletal muscles.

• Autonomic Nervous System (ANS): Controls our glands and internal organ muscles (involuntary).

  • Sympathetic Nervous System: Arouses the body, mobilizing its energy (Fight-or-Flight). Increases heart rate and blood pressure.

  • Parasympathetic Nervous System: Calms the body, conserving its energy (Rest-and-Digest).

The Endocrine System

• Functionality: The body’s ‘slow’ chemical communication system; a set of glands that secrete hormones into the bloodstream.

• Interactions: Hormones are chemically identical to neurotransmitters but travel through the bloodstream, making their effects longer-lasting.

• Key Glands:

  • Pituitary Gland: The most influential gland; regulated by the hypothalamus. It releases growth hormones and oxytocin.

  • Adrenal Glands: Release epinephrine and norepinephrine (adrenaline and noradrenaline) in response to stress.

The Brain Structures

The Brainstem and Older Brain Structures

• Medulla: Base of the brainstem; controls heartbeat and breathing.

• Pons: Helps coordinate movement and control sleep.

• Reticular Formation: A nerve network that travels through the brainstem into the thalamus; plays an important role in controlling arousal.

• Thalamus: The brain’s sensory control center; directs messages to the sensory receiving areas in the cortex.

• Cerebellum: The ‘little brain’ at the rear of the brainstem; processes sensory input, coordinates movement output and balance, and enables nonverbal learning and memory.

The Limbic System

• Amygdala: Two lima-bean-sized neural clusters; linked to aggression and fear.

• Hypothalamus: Directs several maintenance activities (eating, drinking, body temperature), helps govern the endocrine system via the pituitary gland, and is linked to emotion and reward.

• Hippocampus: A neural center located in the limbic system; helps process explicit (conscious) memories for storage.

The Cerebral Cortex

Structure

• The Lobes:

  • Frontal Lobes: Involved in speaking, muscle movements, and in making plans and judgments. Includes the Motor Cortex.

  • Parietal Lobes: Receives sensory input for touch and body position. Includes the Somatosensory Cortex.

  • Occipital Lobes: Includes areas that receive information from the visual fields.

  • Temporal Lobes: Includes the auditory areas, each receiving information primarily from the opposite ear.

• Association Areas: Areas of the cerebral cortex that are not involved in primary motor or sensory functions; rather, they are involved in higher mental functions such as learning, remembering, thinking, and speaking.

Brain Plasticity and Neurogenesis

• Plasticity: The brain’s ability to change, especially during childhood, by reorganizing after damage or by building new pathways based on experience.

• Neurogenesis: The formation of new neurons. Though the brain often attempts to self-repair by reorganizing existing tissue, it sometimes produces new brain cells.

Divided Brain: Functions of Hemispheres

• Corpus Callosum: The large band of neural fibers connecting the two brain hemispheres and carrying messages between them.

• Split Brain: A condition resulting from surgery that isolates the brain’s two hemispheres by cutting the corpus callosum.

• Lateralization:

  • Left Hemisphere: Superior at making quick, literal interpretations of language; logic; math.

  • Right Hemisphere: Excels in making inferences, modulating speech to make meaning clear, and facilitating self-awareness.

Key Terms and Concepts

• Action Potential

• All-or-None Response

• Reuptake

• Agonist/Antagonist

• Sympathetic vs. Parasympathetic

• Limbic System

• Cerebral Cortex

• Neurogenesis

• Corpus Callosum