CHAPTER TWO: BIOLOGY AND BEHAVIOR

CHAPTER TWO: BIOLOGY AND BEHAVIOR

Biopsychology

  • Definition: The scientific study of the links between biological and psychological processes

  • Related Fields:

    • Neuropsychologists

    • Behavior geneticists

    • Biopsychologists

Neural Communication

Neurons

  • Neuron: A nerve cell; the basic building block of the nervous system

    • Components of a Neuron:

    • Dendrites:

      • Description: Often bushy, branching extensions that receive and integrate messages

      • Characteristics: Short and do not have myelin sheath

    • Cell Body (Soma):

      • Description: The integral "life support" component of a neuron; contains nucleus and other supporting structures. If damaged, the nerve dies.

    • Axon:

      • Description: Passes messages away from the cell body to other neurons, muscles, or glands; has terminal branches that form junctions with other cells

      • Characteristics: Segmented extension, myelinated, long

    • Myelin Sheath:

      • Description: Fatty tissue layer segmentally encasing the axons of some neurons; helps speed neural impulses by allowing the impulse to hop from one node to the next

    • Neural Impulse:

      • Description: Electrical signal traveling down the axon

Conduction of Neural Impulses

  • Resting Potential:

    • Definition: Positive charge outside the axon; negative charge inside the axon

  • Action Potential:

    • Definition: A neural impulse generated by the movement of positively charged atoms in and out of channels in the axon’s membrane

  • Refractory Period:

    • Definition: A brief resting pause that occurs after a neuron has fired

  • Threshold:

    • Definition: The level of stimulation required to trigger a neural impulse

    • Equations:

    • (Excitatory) - (Inhibitory) > Threshold: an action potential

How Neurons Communicate

  • Synapse:

    • Definition: The junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron

  • Synaptic Vesicle:

    • Description: Vesicle containing neurotransmitters that fuse with the axon terminal

  • Synaptic Gap:

    • Definition: The tiny junction across which neurotransmitter molecules travel

Steps in Neural Communication

  1. Impulse Transmission:

    • Electrical impulses (action potentials) travel from one neuron to another across the synapse

  2. Neurotransmitter Release:

    • When an action potential reaches the axon terminal, it stimulates the release of neurotransmitter molecules from vesicles

  3. Reuptake:

    • The sending neuron reabsorbs excess neurotransmitter molecules

Neurotransmitters

  • Definition: Chemical messengers that cross the synaptic gap between neurons

  • Types:

    • Agonist: Enhances the effect of neurotransmitters

    • Antagonist: Blocks the effect of neurotransmitters

  • Functions and Examples of Malfunctions:

    • Acetylcholine (ACh): Enables muscle action, learning, and memory; malfunction linked with Alzheimer's disease

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

    • Serotonin: Affects mood, hunger, and sleep; linked to depression with undersupply

    • Norepinephrine: Controls alertness and arousal; undersupply can depress mood

    • GABA (gamma-aminobutyric acid): A major inhibitory neurotransmitter; undersupply linked to seizures and insomnia

    • Glutamate: A major excitatory neurotransmitter; oversupply can overstimulate the brain

    • Endorphins: Influences pain and pleasure perception; oversupply with opiate drugs can suppress natural endorphin supply

Nervous System

  • Definition: The body’s speedy, electrochemical communication system

    • Central Nervous System (CNS): Composed of the brain and spinal cord

    • Peripheral Nervous System: Sensory and motor neurons that connect the CNS to the rest of the body

    • Somatic Nervous System: Controls voluntary movements of skeletal muscles

    • Autonomic Nervous System: Controls self-regulated action of internal organs and glands

      • Sympathetic Nervous System: Arousing; activates fight or flight response

      • Parasympathetic Nervous System: Calming; conserves energy

Central Nervous System

  • Spinal Cord: Connects the peripheral nervous system to the brain and is responsible for reflex actions

Endocrine System

  • Definition: The body's slow chemical communication system consisting of glands that secrete hormones into the bloodstream

  • Hormones: Chemical messengers produced in one tissue that affect another

  • Key Glands:

    • Hypothalamus: Controls the pituitary gland; directs maintenance activities

    • Pituitary Gland: The master gland of the endocrine system

    • Thyroid Gland: Regulates metabolism

    • Adrenal Glands: Triggers fight or flight response

    • Pancreas: Regulates blood sugar levels

    • Gonads: Secrete sexual hormones

Older Brain Structures

  • Brainstem: Central core of the brain; responsible for automatic survival functions

    • Medulla: Controls breathing, blood pressure, and heart rate

    • Reticular Formation: Regulates the sleep/wake cycle and arousal

    • Thalamus: The sensory switchboard; directs messages to sensory areas

    • Cerebellum: Coordinates movement output and balance

Limbic System

  • Definition: Collection of structures involved in processing emotion and memory

  • Key Structures:

    • Hippocampus: Associated with learning and memory

    • Amygdala: Involved in emotional processing and memory association

    • Hypothalamus: Directs maintenance activities and governs the endocrine system

Cerebral Cortex

  • Definition: Surface of the brain associated with higher mental capacities

  • Four Regions (Lobes):

    • Frontal Lobe: Speech, muscle movements, planning, judgment, personality

    • Parietal Lobe: Sensory cortex and spatial reasoning

    • Occipital Lobe: Visual processing areas

    • Temporal Lobe: Auditory processing and face recognition

Functions of the Cortex

  • Motor Cortex: Involved in planning and coordinating movement; each side controls the opposite side of the body

  • Somatosensory Cortex: Processes sensory information from the body; each side controls opposite body side

  • Visual Cortex: Processes visual input; located at the back of the brain

  • Auditory Cortex: Processes auditory input; located above the ear

  • Association Areas: Involved in higher mental functions like learning, thinking, and integrating information

Corpus Callosum

  • Definition: Band of neural fibers connecting the two brain hemispheres

  • Split Brain: A condition where the two hemispheres are isolated by cutting connecting fibers

Imaging Techniques

  • EEG (Electroencephalogram): Measures electrical activity of the brain

  • CT Scan (Computed Tomography): Imaging method using a series of X-rays

  • PET Scan (Positron Emission Tomography): Imaging test that helps reveal how tissues and organs function

  • MRI (Magnetic Resonance Imaging): Imaging technique that uses magnetic fields to visualize internal structures

  • fMRI (Functional MRI): Measures brain activity by detecting changes associated with blood flow

Human Genetics

  • The Genetic Code:

    • DNA (Deoxyribonucleic Acid): Complex molecule containing genetic information

    • Chromosome: Threadlike structures made of DNA containing genes

    • Gene: Biochemical units of heredity

    • Allele: Specific version of a gene

  • Genotype and Phenotype:

    • Genotype: Genetic makeup

    • Phenotype: Physical characteristics

  • Patterns of Genetic Transmission:

    • Homozygous vs. Heterozygous

    • Dominant vs. Recessive

    • Polygenic traits: Traits controlled by multiple genes

    • Multifactorial traits: Traits influenced by multiple factors, including genetics and environment

    • Additive traits: Traits that result from additive effects of multiple alleles