Biological Bases of Behavior and Sensation & Perception: Study Guide

Biological Bases of Behavior and Consciousness

Neurons and Neural Communication

The nervous system is composed of specialized cells called neurons that transmit information throughout the body. Understanding the structure and function of neurons is fundamental to the study of psychology and behavior.

• Parts of a Neuron:

  • Cell body (soma): Contains the nucleus and organelles; responsible for the neuron's metabolic activities.

  • Dendrites: Branch-like extensions that receive signals from other neurons.

  • Axon: Long, slender projection that transmits electrical impulses away from the cell body.

  • Myelin sheath: Fatty layer that insulates the axon, increasing the speed of signal transmission.

  • Terminal branches of axon: Endings that release neurotransmitters to communicate with other neurons.

• Synapses: The junctions (synaptic gaps) where neurons communicate with each other via neurotransmitters.

• Action Potentials: Electrical impulses that travel down the axon, enabling neural communication. Action potentials operate according to the "all-or-none" principle, meaning a neuron either fires completely or not at all.

Example: When you touch a hot surface, sensory neurons transmit the signal to your spinal cord and brain, which then send a response via motor neurons to move your hand away.

Neurotransmitters

Neurotransmitters are chemical messengers that transmit signals across synapses between neurons. They play a crucial role in regulating mood, behavior, and bodily functions.

• Dopamine: Involved in movement, motivation, and reward. Too little is associated with Parkinson's disease; too much with schizophrenia.

• Serotonin: Regulates mood, appetite, and sleep. Low levels are linked to depression.

• Endorphins: Natural painkillers that also promote feelings of pleasure.

Example: Selective serotonin reuptake inhibitors (SSRIs) are medications that increase serotonin levels to treat depression.

The Nervous System

The nervous system is divided into several subsystems, each with specific functions:

• Central Nervous System (CNS): Consists of the brain and spinal cord; processes information and coordinates activity.

• Peripheral Nervous System (PNS): Connects the CNS to the rest of the body.

• Somatic Nervous System: Controls voluntary movements of skeletal muscles.

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

  • Sympathetic Division: Prepares the body for "fight or flight" responses.

  • Parasympathetic Division: Promotes "rest and digest" activities.

Example: When startled, your sympathetic nervous system increases your heart rate and dilates your pupils.

Endocrine System

The endocrine system consists of glands that secrete hormones into the bloodstream, influencing various bodily functions.

• Pituitary gland: The "master gland" that regulates other endocrine glands.

• Adrenal gland: Produces hormones involved in stress responses (e.g., adrenaline).

Comparison: Neurotransmitters act quickly and locally, while hormones act more slowly and have widespread effects.

Brain Regions and Structures

The brain is organized into several regions, each with specialized functions:

• Cerebellum: Coordinates movement and balance.

• Brainstem: Controls basic life functions (e.g., breathing, heartbeat).

• Medulla: Regulates vital autonomic functions.

• Limbic System: Involved in emotion, motivation, and memory.

  • Basal ganglia

  • Hippocampus

  • Thalamus

  • Hypothalamus

  • Amygdala

Example: The hippocampus is essential for forming new memories.

Lobes and Cortices of the Brain

Different lobes and cortices of the brain are responsible for various cognitive and sensory functions:

• Corpus Callosum: Connects the two hemispheres of the brain.

• Cerebral Cortex: Outer layer involved in higher-order functions.

• Frontal Lobe: Associated with reasoning, planning, and movement.

• Pre-Frontal Cortex: Involved in decision-making and social behavior.

• Parietal Lobe: Processes sensory information.

• Occipital Lobe: Processes visual information.

• Temporal Lobe: Processes auditory information and memory.

• Somatosensory Cortex: Processes touch sensations.

• Motor Cortex: Controls voluntary movements.

• Auditory Cortex: Processes sound.

• Visual Cortex: Processes visual stimuli.

Neuropsychology

Neuropsychology explores the relationship between brain function and behavior.

• Neuroplasticity: The brain's ability to reorganize and adapt by forming new neural connections.

• Lateralization: The specialization of certain functions in either the left or right hemisphere of the brain.

• Broca's Area: Involved in speech production.

• Wernicke's Area: Involved in language comprehension.

Example: Damage to Broca's area can result in expressive aphasia, where speech production is impaired.

Sleep

Sleep is a vital biological process regulated by circadian rhythms and various brain structures.

• Circadian Rhythm: The body's internal clock that regulates sleep-wake cycles.

• Pineal Gland: Produces melatonin, a hormone that promotes sleep.

• Stages of Sleep:

  • Stage N1, N2, N3: Non-REM sleep stages, each with distinct brain wave patterns.

  • REM Sleep: Characterized by rapid eye movement and vivid dreams; also called "paradoxical sleep" because the brain is active while the body is relaxed.

• Sleep Disorders: Insomnia, sleep apnea, narcolepsy, nightmares, night terrors, somnambulism (sleepwalking).

Example: Chronic sleep deprivation can impair cognitive function and increase the risk of health problems.

Sensation and Perception

Basic Concepts

Sensation and perception are processes that allow us to interpret and respond to our environment.

• Sensation: The process by which sensory receptors and the nervous system receive and represent stimulus energies from the environment.

• Perception: The process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events.

• Sensory Receptor Cells: Specialized cells that detect specific types of stimuli (e.g., light, sound, pressure).

• Absolute Threshold: The minimum stimulation needed to detect a particular stimulus 50% of the time.

• Difference Threshold (Just Noticeable Difference): The minimum difference between two stimuli required for detection 50% of the time.

• Sensory Adaptation: Diminished sensitivity to a constant stimulus over time.

Example: After wearing a watch for a while, you may stop noticing its presence due to sensory adaptation.

Vision

Vision is the sense that allows us to perceive light, color, and movement.

• Cones: Photoreceptor cells responsible for color vision and detail.

• Rods: Photoreceptor cells sensitive to low light levels.

• Feature Detection: The process by which the brain identifies specific components of visual stimuli.

• Color Vision Theories:

  • Trichromatic Theory: Proposes three types of cones sensitive to red, green, and blue.

  • Opponent-Process Theory: Proposes that color perception is controlled by the activity of two opponent systems: a blue-yellow mechanism and a red-green mechanism.

  • Additive vs. Subtractive Color Mixing: Additive mixing involves combining light of different colors; subtractive mixing involves combining pigments.

Example: The afterimage effect supports the opponent-process theory of color vision.

Audition (Hearing)

Audition is the sense of hearing, which involves the detection of sound waves and their interpretation by the brain.

• Outer, Middle, and Inner Ear: Structures that collect, amplify, and transduce sound waves.

• Cochlea: Spiral-shaped organ in the inner ear that converts sound vibrations into neural signals.

• Auditory Nerve: Transmits auditory information to the brain.

• Types of Deafness: Conductive (problems with the ear structures) and sensorineural (damage to hair cells or auditory nerve).

Example: Hearing aids can help with conductive deafness but not sensorineural deafness.

Other Senses

• Kinaesthesia: Sense of body movement and position.

• Vestibular Sense: Sense of balance and spatial orientation.

• Tactile Sense: Sense of touch.

• Phantom Limb Syndrome: Sensation that an amputated limb is still present.Perception

Perception involves interpreting sensory information to form a meaningful understanding of the world.

• Top-Down Processing: Perception driven by cognition; using prior knowledge to interpret sensory information.

• Bottom-Up Processing: Perception based on the physical features of the stimulus.

• Gestalt Principles: Rules describing how we organize visual information into meaningful wholes.

  • Proximity

  • Similarity

  • Closure

  • Continuity

  • Figure-ground

• Depth Perception: Ability to perceive the world in three dimensions using monocular (e.g., interposition, linear perspective) and binocular cues (e.g., retinal disparity).

• Perceptual Illusions: Misinterpretations of sensory information.

Example: The Müller-Lyer illusion demonstrates how context can influence perception of line length.

Structures of the Eye

• Pupil: Opening that regulates the amount of light entering the eye.

• Lens: Focuses light onto the retina.

• Retina: Contains photoreceptor cells (rods and cones).

• Optic Nerve: Transmits visual information to the brain.

• Blind Spot: Area where the optic nerve leaves the eye; no photoreceptors present.

Gustation and Olfaction

Gustation (taste) and olfaction (smell) are chemical senses that detect molecules in food and the air.

• Taste Buds: Sensory organs on the tongue that detect sweet, sour, salty, bitter, and umami flavors.

• Olfactory Receptors: Detect airborne chemicals; closely linked to taste perception.

Example: A cold can reduce your sense of taste because it impairs your sense of smell.

Table: Comparison of Nervous System Divisions

Division			Main Function	Example
Central Nervous System (CNS)	Processes information, coordinates activity	Brain interprets sensory input
Peripheral Nervous System (PNS)	Connects CNS to limbs and organs	Motor nerves move muscles
Somatic Nervous System	Controls voluntary movements	Raising your hand
Autonomic Nervous System	Regulates involuntary functions	Heartbeat, digestion
Sympathetic Division	Prepares body for action	Increased heart rate when scared
Parasympathetic Division	Conserves energy, calms body	Slowed heart rate after stress

Key Equations

• All-or-None Law of Action Potentials: $\text{If the threshold is reached, the neuron fires at full strength; if not, it does not fire at all.}$

• Weber's Law (Difference Threshold): $\frac{\Delta I}{I} = k$ Where $\Delta I$ is the change in stimulus intensity, $I$ is the original intensity, and $k$ is a constant.

Additional info: Some explanations and examples have been expanded for clarity and completeness based on standard introductory psychology textbooks.