Comprehensive Study Notes: Nervous System, Brain Structures, Neurons, Perception, and Heredity

Nervous System Overview

• Sensory inputs and motor outputs comprise the nervous system

• Senses include nose (olfaction), mouth (gustation), ears (audition), eyes (vision), skin and other senses

• Skeletal (somatic) muscles connect to the skeleton and support voluntary movement; autonomic functions regulate involuntary processes (e.g., heartbeat, digestion, sweating)

• Autonomic division splits into two complementary branches:

  • Sympathetic nervous system (fight or flight): mobilizes body resources during threat or challenge

  • Effects include pupil dilation to take in more light, reduced salivation, bronchodilation/increased lung capacity, increased heart rate, increased sweating, goosebumps, some bladder relaxation, and hormone release

  • Parasympathetic nervous system (calming, conserving resources): calms the body after threat

  • Effects include pupil constriction, increased salivation, reduced lung size requirements, decreased heart rate, digestion of stomach contents, bladder function restoration

• Key contrast: SNS = mobilize/fight or flight; PNS = conserve/safe calming of bodily resources

• Two big-picture divisions of nervous system:

  • Central nervous system (CNS): brain and spinal cord

  • Peripheral nervous system (PNS): autonomic and somatic branches that connect CNS to the body

• Somatic nervous system = voluntary movements; Autonomic nervous system = involuntary functions (digestion, heart rate, etc.)

• This course often revisits the CNS vs PNS and the autonomic subdivisions (SNS vs PNS) to explain brain–body regulation and responses to environment

Brain and its Major Divisions

• Brain can be divided by structure (hindbrain, midbrain, forebrain) and by surface anatomy (hemispheres, lobes)

• Hemispheres: right and left cerebral hemispheres; cognitive and motor functions can be lateralized but most tasks use multiple areas

• Forebrain, midbrain, hindbrain (from bottom to top):

  • Hindbrain (closest to the neck): essential for automatic/basic life-sustaining functions

  • Midbrain: central core of brainstem; regulates sleep/wake, integrates senses, houses dopamine system, contains reticular formation (involved in reflexes, pain perception, sleep/arousal, circadian rhythms)

  • Forebrain: largest/most complex; supports higher-order thought and decision making

• Hindbrain components:

  • Cerebellum: balance, movement, coordination; learning motor skills; historically linked to balance, but now recognized for broader motor and some cognitive roles

  • Pons: bridge between medulla and cerebellum; cell bodies linked to sleep and arousal; part of brainstem

  • Medulla: controls autonomic, life-sustaining functions (breathing, muscle tone, circulation)

• Midbrain components:

  • Central core of brainstem; regulates sleep/wakefulness; integrates senses (vision, hearing, touch); contains dopamine system (involved in voluntary movement and reward processes)

  • Reticular formation: involved in reflexes, sleep/wake cycles, arousal, and pain perception; contributes to circadian rhythm regulation

• Forebrain components:

  • Thalamus: central relay station for senses (vision, hearing, touch, taste); all senses except smell pass through here before cortical processing

  • Hypothalamus: regulates biological drives (fighting, foraging, fleeing, mating) – the four F drives; also involved in eating and sexual behaviors

  • Limbic system: memory and emotions; key emotion/memory interactions (e.g., amygdala; hippocampus involved in memory formation)

  • Cerebrum: large, gray-matter outer layer; executive functions; divided into two hemispheres via corpus callosum; contains frontal, parietal, occipital, temporal lobes

• Cerebral hemispheres and functional specialization:

  • Left hemisphere: often associated with language, reading, writing, logical/problem-solving tasks

  • Right hemisphere: often associated with creativity, spatial tasks, music, art, and spatial manipulation

  • Note: the idea of “left-brain vs right-brain” is a simplification; many tasks recruit both hemispheres depending on context

• Important structures in the forebrain:

  • Hypothalamus and limbic system locations and roles

  • Hippocampus: crucial for forming long-term memories

  • Corpus callosum: large bundle of nerve fibers connecting the two hemispheres; crucial for interhemispheric communication

• Visualizing the forebrain/cortex: four lobes

  • Frontal lobe: higher-order thinking, planning, decision making; motor cortex handles fine motor control (mouth, hands) and planning

  • Parietal lobe: somatosensory processing; bodily sensation and integration

  • Occipital lobe: primary visual cortex; vision processing

  • Temporal lobe: primary auditory cortex; processing sounds; memory processing sites nearby (e.g., hippocampus in limbic system)

• Cortex and brain plasticity:

  • Brain is plastic: can reorganize after damage; experience-dependent changes occur with practice (e.g., sports, driving video games, juggling, ballet)

  • Neurogenesis: adult brains can generate new neurons; higher with exercise, lower under high stress

  • Brain damage may limit plasticity; age-related changes influence plasticity

• Quick summary points for reference:

  • Forebrain = planning/thought; Hindbrain = basic automatic functions; Midbrain = sensory integration and arousal; Limbic system = memory/emotion; Thalamus = sensory relay; Hypothalamus = drives; Cerebellum = balance/movement; Corpus callosum = interhemispheric communication

  • Lateralization is a tendency, not an absolute rule

  • Visual system: retina, optic nerve, optic chiasm, LGN, visual cortex; every eye sends information to both hemispheres with crossing depending on the visual field

Imaging, Lesioning, and Brain Research Methods

• Lesioning (animal studies): destroying a brain area with electrical current to study effects on behavior

• Electrical stimulation: stimulating a brain region to observe changes in behavior

• Structural imaging:

  • CT scan (computed tomography): enhanced X-ray imaging from multiple angles for detailed structural images

  • MRI (magnetic resonance imaging): magnets/magnetic fields provide high-resolution 3D images of brain structure; generally preferred to CT

• Functional imaging:

  • PET scan (positron emission tomography): uses radioactive tracers to measure metabolic activity; areas with higher activity light up

  • fMRI (functional MRI): measures blood flow to infer neural activity, based on oxygen use

• Contralateral functioning: brain areas control opposite sides of the body (e.g., right hemisphere controls left side)

• Split-brain research and corpus callosum:

  • Severing corpus callosum can reduce seizures in severe epilepsy; splits hemispheres to limit interhemispheric spread of abnormal activity

  • This research helps reveal how each hemisphere contributes to perception, language, and behavior

• Visual system pathway basics (overview for study):

  • Retina → optic nerve → optic chiasm → lateral geniculate nucleus (LGN) → visual cortex (occipital lobe)

  • Visual fields map to contralateral hemispheres; nasal retinal input crosses, temporal input stays on the same side before crossing later in the brain

The Four Lobes: Functions and Core Concepts

• Frontal Lobe:

  • Prefrontal cortex: planning, decision making, executive function

  • Motor cortex: fine motor control (e.g., hands, lips, tongue)

• Parietal Lobe:

  • Primary somatosensory cortex: processing touch and bodily sensation

• Occipital Lobe:

  • Primary visual cortex: processing visual information

• Temporal Lobe:

  • Primary auditory cortex: processing sounds

• Cerebral cortex: outer layer, associated with higher cognitive processes; left/right hemisphere specialization exists but is not absolute

Visual System: Eye, Retina, and Color Vision Basics

• Light characteristics (stimulus for vision):

  • Amplitude: brightness of a light wave

  • Wavelength: color hue (longer vs shorter wavelengths)

  • Purity: saturation of color (how pure/brilliant the color appears)

• Eye anatomy (front to back):

  • Cornea: the window through which light enters the eye

  • Iris: colored muscle ring; controls pupil size; color dependent on iris

  • Pupil: opening whose size changes with light and arousal; constricts with bright light, dilates in dim light

  • Lens: behind cornea; focuses light onto retina; curvature adjusts to focus (accommodation)

  • Retina: light-sensitive layer at the back of the eye; contains photoreceptors (rods and cones)

  • Optic nerve: transmits visual information from retina to brain

• Eye anatomy details:

  • Cataract: clouding of the lens; surgically treated in older individuals

  • Blind spot (optic disc): region on retina with no photoreceptors where optic nerve exits the eye

• Photoreceptors: rods and cones

  • Rods: night vision, peripheral vision; work well in low light; one type of receptor; not color-specific

  • Cones: daylight/color vision; three color receptors (red, green, blue) enable color vision

  • Fovea: central retina area with high visual acuity; contains densely packed cones

• Retinal processing:

  • Retina transforms light patterns into neural signals

  • Signals pass from rods/cones to bipolar and then ganglion cells before forming the optic nerve

  • The retina is a layered network of cells that preprocess visual information before it leaves the eye

• Visual adaptation/dark adaptation:

  • Dark adaptation takes about t ext{ approx } 30 ext{ minutes}; most rapid improvement in the first t ext{ ≈ } 10 ext{ minutes}

• Visual processing pathway (simplified):

  • Light pattern forms on retina → retina processes via layers of cells (rods/cones → bipolar → ganglion → optic nerve) → signals travel to visual cortex in occipital lobe

• Visual field processing and pathways:

  • Each eye sends information to both hemispheres; the right visual field is processed by the left hemisphere and vice versa; some visual field data cross at the optic chiasm, others stay on the same side depending on nasal vs temporal retina routing

• The left and right eye inputs converge to create a single perception of a scene; visual processing continues in the occipital lobe and involves higher-order areas for perception and recognition

Visual Processing in the Brain and Visual Agnosia (Case Example)

• Visual agnosia: inability to recognize objects through sight despite having intact vision (as in Oliver Sacks’ case)

  • Patient could see shapes and features (e.g., a geometric solid with color), but could not identify the object by sight alone

  • Demonstrates dissociation between sensation (detection of light) and perception (interpretation/recognition)

• Sensation vs Perception:

  • Sensation: stimulation of sense organs and energy absorption (e.g., light waves, sound waves)

  • Perception: brain’s organization and interpretation of sensory input to give it meaning (e.g., recognizing a performance and clapping)

Sensation vs Perception: Core Distinctions

• Sensation is the input side of perception; perception is the interpretation side

• Example: watching a performance involves sensory input (seeing, hearing) and perceptual processing (recognizing a performance, appreciating it, and responding)

Perceptual Processing: Summary Concepts

• Vision basics: critical to know for exams

• The brain’s handling of sensory information occurs in multiple stages, from receptors to thalamus to cortex

• Perception depends on interpretation, experience, context, and higher-order processing in the cortex

Neurotransmission and Synapses (Neurons and Support Cells)

• Neuron structure:

  • Soma (cell body): contains nucleus; integrates signals

  • Dendrites: branch-like extensions receiving signals from other neurons

  • Axon: long fiber sending signals away from the soma; can branch to communicate with multiple cells

  • Myelin sheath: insulating layer around axons; enables faster signal transmission via saltatory conduction (signal jumps from node to node)

  • Nodes of Ranvier: gaps in the myelin sheath enabling saltatory conduction

  • Terminal buttons: end of axon terminals; site of neurotransmitter release

  • Synapse: gap between presynaptic and postsynaptic cells where neurotransmission occurs

• Glial cells: support cells that provide structural support and nutrients; insulate neurons; not primarily involved in signal transmission (glia are the “glue” of the nervous system)

• Electrical signaling in neurons:

  • Resting potential: neurons are ready to fire; typical value is V_{rest} = -70 ext{ mV}

  • Action potential: brief, rapid neural impulse; typical peak is V_{AP} = +40 ext{ mV}

  • All-or-none principle: an action potential occurs fully or not at all; amplitude is consistent

  • Refractory period: short time after an action potential during which another action potential cannot fire

  • Graded (gradient) potentials: small, localized changes in membrane potential that can summate to trigger an action potential

• Synaptic transmission (chemical communication between neurons):

  • Neurotransmitters stored in synaptic vesicles within the presynaptic terminal

  • Release of neurotransmitters into the synaptic cleft

  • Neurotransmitters bind to receptor sites on the postsynaptic membrane

  • Unbound neurotransmitters are removed through enzymatic inactivation, diffusion, or reuptake into the presynaptic neuron

  • Reuptake returns unused neurotransmitters to the presynaptic neuron for reuse

• Conceptual takeaways:

  • Signal transmission in neurons is electrochemical

  • Different neurotransmitters produce different effects; table of neurotransmitters exists in slides (not memorized in this course, but useful for reference)

Heredity, Epigenetics, and Evolutionary Perspectives on Behavior

• Heritability: the extent to which behavioral traits are influenced by genetics

• Diathesis-stress model:

  • Diathesis = predisposition to a disorder

  • Stressful experiences can activate or reveal symptoms

  • Example: schizophrenia shows higher likelihood when predisposition plus stressors occur

• Chromosomes and genes:

  • Humans have 23 pairs of chromosomes; genes are DNA segments that code for traits

  • Polygenic traits: behavioral traits often influenced by multiple genes rather than a single gene

• Research approaches to behavioral heredity:

  • Family studies: examine traits in relatives to infer genetic influence

  • Twin studies: compare identical twins (100% shared DNA) with fraternal twins (approximately 50% shared DNA)

  • Adoption studies: compare biological vs adoptive parents to separate genetics from environment

  • Genetic mapping: locate genes on chromosomes; emerging with the Human Genome Project; ongoing work on mapping behavioral traits

• Epigenetics:

  • Study of how environmental factors can affect gene expression without changing the DNA sequence

  • Epigenetic changes can be caused by prenatal development, diet, stress, toxins, and other environmental factors

  • Epigenetics helps explain how environment interacts with genetics to influence psychological traits and disorders

• Evolution and natural selection (behavioral traits):

  • Traits that increase reproductive success and survival can spread through populations over generations

  • Adaptation describes inherited traits that solved evolutionary problems and were favored by selection

  • Example: taste for fats may reflect historical dietary adaptations; advantageous traits may become more common if they improve survival or reproduction

Putting It All Together: Key Takeaways for the Exam

• The nervous system comprises CNS and PNS; the PNS has somatic (voluntary) and autonomic (involuntary) divisions, with sympathetic (arousing) and parasympathetic (calming) components

• The brain is organized hierarchically: hindbrain (basic functions), midbrain (sensory integration and arousal), forebrain (cognition and emotion); lobes of the cortex support specialized functions

• Key brain structures and functions:

  • Thalamus: sensory relay (except smell)

  • Hypothalamus: drives (fighting, fleeing, feeding, mating)

  • Limbic system: emotion and memory; hippocampus (memory formation); amygdala (emotion processing)

  • Cerebrum: cortex with left/right hemispheres; frontal/parietal/occipital/temporal lobes

  • Corpus callosum: connects hemispheres; split-brain studies show interhemispheric processing differences

• Imaging and research methods provide both structural and functional insights; lesioning and stimulation reveal causal roles; CT/MRI provide structure; PET/fMRI provide function

• Neurons operate with resting potential and action potentials; signal transmission is chemical at synapses; neurotransmitters and reuptake regulate communication

• Sensation vs perception distinguishes input from interpretation; the visual system demonstrates complex processing from light to perception, including color, brightness, and spatial interpretation

• The eye and retina transform light into neural signals; rods confide to low light/peripheral vision; cones enable color and daylight vision; the fovea is where acuity is highest; the blind spot corresponds to the optic disc

• Visual field processing involves contralateral brain mapping; optic chiasm crossing leads to cross-hemisphere processing for most of the visual field

• The brain demonstrates remarkable plasticity and neurogenesis under certain conditions; damage can be compensated through reorganization, but age and extent of injury influence recovery

• Visual agnosia illustrates the separation between sensation and perception; recognizing objects requires intact perceptual processing beyond mere sensation

• Behavioral genetics and evolution provide frameworks to understand how genetics and environment shape behavior over time; diathesis-stress and epigenetics explain variability in psychological traits and disorders

Practical and Ethical Implications Mentioned in the Lecture

• Animal research involving lesioning and electrical stimulation poses ethical considerations; benefits include understanding brain function and potential medical advances, but must be weighed against animal welfare

• Brain plasticity and neurogenesis emphasize the importance of lifestyle factors (e.g., exercise) for cognitive health and recovery after injury

• Split-brain research has informed our understanding of hemispheric specialization and the consequences of disconnecting brain regions; it also informs treatment approaches for severe epilepsy

• Epigenetics highlights how environment and experiences can influence gene expression, informing interventions and prevention strategies for mental health

• Understanding visual pathways and perception helps in diagnosing perceptual disorders (e.g., visual agnosia) and informs rehabilitation approaches

Quick Reference: Key Terms and Concepts

• Resting potential: V_{rest} = -70 ext{ mV}

• Action potential: V_{AP} = +40 ext{ mV}; all-or-none nature

• Saltatory conduction and myelin sheath around axons

• Synapse: presynaptic to postsynaptic gap; neurotransmitter release and receptor binding

• Neurotransmitters and reuptake/inactivation

• Glial cells: support neurons

• Thalamus, hypothalamus, limbic system, hippocampus, amygdala, cerebellum, pons, medulla

• Visual system: cornea, pupil/iris, lens, retina (rods/cones), fovea, optic nerve, optic chiasm, LGN, visual cortex

• Visual fields and contralateral control

• Sensation vs perception; light properties (amplitude, wavelength, purity)

• Perceptual disorders: visual agnosia

• Heritability, diathesis-stress model, epigenetics, chromosomes, genes, polygenic traits

• Evolutionary psychology concepts: natural selection, adaptation, reproductive success

• Key imaging modalities: CT, MRI, PET, fMRI

• Research methods: lesioning, electrical stimulation, split-brain studies

• Color vision theory note: basic reference to trichromatic theory (often covered in color perception discussions)

Note on Exam Scope (as mentioned in the lecture)

• Chapter 1: history of psychology, major schools of thought, founders, nature vs nurture, modern psychology branches, how psychology is applied

• Chapter 2: scientific method, sampling, population, experimental vs correlational research, ethics and flaws in research

• Chapter 3: nervous system, CNS vs PNS, autonomic divisions, brain structures, left/right hemispheres, neuron basics, action potentials

• Chapter 4: sensation and perception, vision and hearing basics; focus on vision and the eye; not all color theory details, but core concepts of sensation and perception

• Exam format: 60 multiple-choice questions; materials on Canvas; study guide with updated content prior to the exam