Biological Psychology: Chapter 3 Study Notes

Biological Psychology: Chapter 3

Lecture Overview

This chapter explores the biological foundations of behavior, focusing on nerve cells, the brain-behavior network, the endocrine system, brain mapping techniques, and the interplay between nature and nurture in psychological traits.

• Nerve Cells

• The Brain-Behavior Network

• The Endocrine System

• Mapping the Mind

• Nature and Nurture

Nerve Cells

Structure and Function of Neurons

Neurons are the fundamental units of the nervous system, specialized for communication. They transmit information via electrical and chemical signals.

• Neurons: Nerve cells that communicate through electrical impulses and neurotransmitters.

• Glial Cells: Support cells that form myelin, maintain the blood-brain barrier, respond to injury, remove debris, and influence learning and memory.

• Key Parts of a Neuron:

  • Dendrites: Receive signals from other neurons.

  • Cell Body (Soma): Contains the nucleus and organelles.

  • Axon: Transmits electrical impulses away from the cell body.

  • Axon Terminals: Release neurotransmitters into the synapse.

  • Myelin Sheath: Insulating layer that speeds up signal transmission.

  • Nodes of Ranvier: Gaps in myelin that facilitate rapid conduction.

Example: Multiple sclerosis is a disease where the myelin sheath is damaged, leading to impaired neural communication.

The Action Potential

Neurons communicate via action potentials, which are rapid changes in electrical charge that travel down the axon.

• Resting Potential: The baseline electrical charge of a neuron ($-70$ mV).

• Action Potential: A sudden positive shift in charge that propagates along the axon.

• Refractory Period: A brief time after an action potential when the neuron cannot fire again.

Equation:

$\text{Resting Potential} \approx -70\ \text{mV}$

Neurotransmitters and Synaptic Transmission

Communication between neurons at synapses is chemical, involving neurotransmitters (NTs).

• Neurotransmitters: Chemical messengers released from axon terminals that bind to receptors on the next neuron.

• Reuptake: The process by which NTs are reabsorbed into the axon terminal.

• Excitatory NTs: Increase the likelihood of the next neuron firing (e.g., glutamate).

• Inhibitory NTs: Decrease the likelihood of firing (e.g., GABA).

Example: Acetylcholine (ACh) is involved in muscle contraction and memory; dopamine is linked to reward and movement.

Drugs and Neurotransmitter Activity

• Agonists: Increase NT activity (e.g., opioids mimic endorphins).

• Antagonists: Decrease NT activity (e.g., antipsychotics block dopamine receptors).

Example: Prozac blocks serotonin reuptake, increasing serotonin levels in the synapse.

Neural Plasticity

The brain's ability to change and adapt in response to experience.

• Synaptogenesis: Formation of new synapses.

• Pruning: Elimination of unused synapses.

• Myelination: Formation of myelin sheath around axons.

• Long-Term Potentiation: Strengthening of synapses based on recent patterns of activity.

Example: Learning a new skill increases synaptic connections in relevant brain areas.

The Brain-Behavior Network

Central and Peripheral Nervous Systems

The nervous system is divided into the central nervous system (CNS) and the peripheral nervous system (PNS).

• CNS: Composed of the brain and spinal cord; processes sensory information and issues commands.

• PNS: Consists of nerves outside the CNS; subdivided into the somatic and autonomic nervous systems.

• Somatic Nervous System: Controls voluntary movements.

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

Divisions of the Autonomic Nervous System

• Sympathetic Division: Activates during stress or emergencies ("fight or flight").

• Parasympathetic Division: Promotes rest and digestion.

Major Brain Structures and Their Functions

• Cerebral Cortex: The outermost layer, responsible for higher-order functions like reasoning, language, and perception.

• Corpus Callosum: Connects the two cerebral hemispheres, allowing communication between them.

• Lobes of the Cortex:

  • Frontal Lobe: Executive functions, planning, movement (motor cortex), speech (Broca's area).

  • Parietal Lobe: Sensory processing (somatosensory cortex), spatial awareness.

  • Temporal Lobe: Auditory processing, language comprehension (Wernicke's area), memory.

  • Occipital Lobe: Visual processing.

• Basal Ganglia: Movement control and reward processing; dysfunction linked to Parkinson's disease.

• Limbic System: Emotional processing, motivation, and memory (includes amygdala, hippocampus).

• Brain Stem: Basic life functions (breathing, heartbeat); includes midbrain, pons, medulla.

• Cerebellum: Balance, coordination, and motor learning.

• Spinal Cord: Transmits signals between brain and body; mediates reflexes.

Hemispheric Specialization

Each hemisphere of the brain is specialized for certain functions, but both work together for most tasks.

Left Hemisphere	Right Hemisphere
Fine-tuned language skills (speech, writing, reading)	Coarse language skills (simple speech, tone, perceptual grouping)
Actions (making facial expressions, motion detection)	Face perception, spatial skills

Example: Damage to Broca's area (left hemisphere) impairs speech production.

Mapping the Mind

Brain Imaging and Mapping Techniques

Modern neuroscience uses various techniques to study brain structure and function.

• Electroencephalograph (EEG): Measures electrical activity via electrodes on the scalp; useful for identifying active brain regions during tasks.

• Computed Tomography (CT): Uses X-rays to create 3D images of brain structure.

• Magnetic Resonance Imaging (MRI): Uses magnetic fields to visualize brain anatomy.

• Positron Emission Tomography (PET): Measures consumption of radioactive molecules to assess neural activity.

• Functional MRI (fMRI): Visualizes brain activity by detecting changes in blood flow.

• Transcranial Magnetic Stimulation (TMS): Applies magnetic fields to stimulate or disrupt brain function, allowing causal inference.

• Magnetoencephalography (MEG): Measures magnetic fields generated by neural activity.

Example: fMRI can show which brain areas are active during language tasks.

The Endocrine System

Hormones and Behavior

The endocrine system is a network of glands that secrete hormones, which regulate various bodily functions and influence behavior.

• Hormones: Chemical messengers released into the bloodstream, affecting organs and tissues.

• Pituitary Gland: The "master gland" that controls other glands and releases hormones influencing growth, blood pressure, and reproduction (e.g., oxytocin).

• Adrenal Glands: Release adrenaline and cortisol during stress; adrenaline increases energy, cortisol regulates metabolism and stress response.

Example: Oxytocin is involved in maternal bonding and romantic attachment.

Nature and Nurture

Genetics and Behavior

Both genetic and environmental factors shape psychological traits and behaviors.

• Chromosomes: Structures in cells that carry genes; humans have 46 chromosomes (23 pairs).

• Genotype: The genetic makeup of an individual.

• Phenotype: Observable traits resulting from genotype and environment.

• Dominant and Recessive Genes: Dominant genes express their traits even if only one copy is present; recessive genes require two copies.

Evolution and Adaptation

• Adaptations: Traits that increase an organism's survival and reproductive success.

• Natural Selection: The process by which advantageous traits become more common in a population.

• Human Evolution: Human brains have tripled in size since diverging from apes, especially in the cerebral cortex, supporting advanced cognition.

Heritability and Research Designs

• Heritability: The proportion of variation in a trait attributable to genetic factors.

• Research Designs: Family studies, twin studies, and adoption studies help estimate genetic and environmental contributions to traits.

Example: Height is highly heritable, while religious affiliation is not.

Additional info: These notes synthesize and expand upon the provided lecture slides and notes, offering definitions, examples, and context for key concepts in biological psychology.