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

Nervous System

Comprises sensory inputs and motor outputs, divided into the Central Nervous System (CNS) and Peripheral Nervous System (PNS).

Skeletal (Somatic) Muscles

Connect to the skeleton and support voluntary movement.

Autonomic Nervous System

Regulates involuntary processes like heartbeat, digestion, and sweating.

Sympathetic Nervous System (SNS)

(Fight or Flight) Mobilizes body resources during threat or challenge, causing pupil dilation, increased heart rate, and bronchodilation.

Parasympathetic Nervous System (PNS)

(Calming, Conserving Resources) Calms the body after threat, causing pupil constriction, decreased heart rate, and increased salivation.

Central Nervous System (CNS)

Consists of the brain and spinal cord.

Peripheral Nervous System (PNS)

Includes autonomic and somatic branches that connect the CNS to the body.

Hindbrain

Essential for automatic/basic life-sustaining functions, located closest to the neck.

Midbrain

Central core of the brainstem; regulates sleep/wake, integrates senses, houses the dopamine system, and contains the reticular formation.

Forebrain

Largest and most complex part of the brain; supports higher-order thought and decision-making.

Cerebellum

Located in the hindbrain; involved in balance, movement, coordination, and learning motor skills.

Pons

Located in the hindbrain; a bridge between the medulla and cerebellum, with cell bodies linked to sleep and arousal.

Medulla

Located in the hindbrain; controls autonomic, life-sustaining functions like breathing, muscle tone, and circulation.

Reticular Formation

Part of the midbrain; involved in reflexes, sleep/wake cycles, arousal, pain perception, and circadian rhythm regulation.

Thalamus

Located in the forebrain; a central relay station for all senses except smell, before cortical processing.

Hypothalamus

Located in the forebrain; regulates biological drives (fighting, foraging, fleeing, mating) and eating/sexual behaviors.

Limbic System

Located in the forebrain; associated with memory and emotions, including structures like the amygdala (emotion) and hippocampus (memory formation).

Cerebrum

Largest, gray-matter outer layer of the forebrain; supports executive functions and is divided into two hemispheres connected by the corpus callosum.

Left Hemisphere

Often associated with language, reading, writing, and logical/problem-solving tasks.

Right Hemisphere

Often associated with creativity, spatial tasks, music, art, and spatial manipulation.

Corpus Callosum

A large bundle of nerve fibers connecting the two cerebral hemispheres, crucial for interhemispheric communication.

Frontal Lobe

Governs higher-order thinking, planning, decision-making, and fine motor control (via the motor cortex).

Parietal Lobe

Processes somatosensory information, including bodily sensation and integration.

Occipital Lobe

Houses the primary visual cortex, responsible for vision processing.

Temporal Lobe

Contains the primary auditory cortex for processing sounds, and memory processing sites nearby.

Brain Plasticity

The brain's ability to reorganize itself after damage, or to change structurally and functionally based on experience.

Neurogenesis

The process by which adult brains can generate new neurons.

Lesioning

A research method (primarily in animal studies) involving destroying a brain area with an electrical current to study effects on behavior.

CT Scan (Computed Tomography)

A structural imaging technique using enhanced X-ray imaging from multiple angles for detailed structural brain images.

MRI (Magnetic Resonance Imaging)

A structural imaging technique using magnets and magnetic fields to provide high-resolution 3D images of brain structure.

PET Scan (Positron Emission Tomography)

A functional imaging technique that uses radioactive tracers to measure metabolic activity in the brain.

fMRI (Functional MRI)

A functional imaging technique that measures blood flow to infer neural activity, based on oxygen use.

Contralateral Functioning

The principle that brain areas control opposite sides of the body (e.g., the right hemisphere controls the left side).

Split-Brain Research

Studies conducted on patients whose corpus callosum has been severed (often to reduce severe epilepsy), revealing hemispheric specialization.

Sensation

The stimulation of sense organs and the absorption of energy (e.g., light waves, sound waves).

Perception

The brain's organization and interpretation of sensory input to give it meaning (e.g., recognizing an object or performance).

Visual Agnosia

The inability to recognize objects through sight despite having intact vision, demonstrating dissociation between sensation and perception.

Amplitude (Light)

The brightness of a light wave.

Wavelength (Light)

Determines the color hue of light (longer vs. shorter wavelengths).

Purity (Light)

The saturation or brilliance of a color.

Cornea

The transparent outer window through which light enters the eye.

Pupil

The opening in the iris whose size changes with light levels and arousal, regulating the amount of light entering the eye.

Iris

The colored muscle ring that controls the size of the pupil.

Lens

Located behind the cornea; focuses light onto the retina by adjusting its curvature (accommodation).

Retina

The light-sensitive layer at the back of the eye containing photoreceptors (rods and cones).

Optic Nerve

Transmits visual information from the retina to the brain.

Rods

Photoreceptors specialized for night vision and peripheral vision; work well in low light, not color-specific.

Cones

Photoreceptors specialized for daylight and color vision; three types (red, green, blue) enable color perception.

Fovea

The central area of the retina with the highest visual acuity, containing densely packed cones.

Blind Spot (Optic Disc)

The region on the retina where the optic nerve exits the eye, lacking photoreceptors.

Dark Adaptation

The process by which the eyes become more sensitive to dim light, taking approximately 30 minutes, with the most rapid improvement in the first 10 minutes.

Neuron

The basic unit of the nervous system responsible for transmitting electrochemical signals.

Soma (Cell Body)

The part of the neuron containing the nucleus; integrates signals.

Dendrites

Branch-like extensions of a neuron that receive signals from other neurons.

Axon

A long fiber extending from the soma that sends signals away from the cell body.

Myelin Sheath

An insulating layer around axons that enables faster signal transmission via saltatory conduction.

Nodes of Ranvier

Gaps in the myelin sheath that allow the action potential to jump from node to node, speeding up conduction.

Terminal Buttons

The ends of axon terminals where neurotransmitters are released into the synapse.

Synapse

The microscopic gap between the presynaptic and postsynaptic cells where neurotransmission occurs.

Glial Cells

Support cells in the nervous system that provide structural support, nutrients, and insulation to neurons.

Resting Potential

The stable, negative electrical charge of a neuron when it is inactive, typically -70 ext{ mV}. An action potential cannot occur.

Action Potential

A brief, rapid neural impulse or electrical signal that travels down the axon, peaking at about +40 ext{ mV}. Also known as nerve impulse.

All-or-None Principle

The rule that an action potential either occurs fully with consistent amplitude or does not occur at all.

Refractory Period

A short time after an action potential during which another action potential cannot be fired.

Neurotransmitters

Chemical messengers stored in synaptic vesicles that transmit signals across the synaptic cleft by binding to receptor sites on the postsynaptic membrane.

Reuptake

The process by which unbound neurotransmitters are reabsorbed into the presynaptic neuron for reuse.

Heritability

The extent to which variation in behavioral traits within a population can be attributed to genetic influence.

Diathesis-Stress Model

A psychological theory suggesting that a predisposition (diathesis) to a disorder can be activated or revealed by stressful experiences.

Polygenic Traits

Behavioral traits that are influenced by multiple genes rather than a single gene.

Epigenetics

The study of how environmental factors can affect gene expression without changing the underlying DNA sequence.

Natural Selection

The process by which traits that increase reproductive success and survival become more common in a population over generations.

Adaptation

Inherited traits that solved evolutionary problems and were favored by natural selection, improving survival or reproduction.