Biological Bases of Behavior, Sensation, and Perception: Study Guide

Biological Bases of Behavior and Consciousness

Parts of a Neuron and Their Functions

Neurons are the fundamental units of the nervous system, responsible for transmitting information throughout the body. Each part of a neuron has a specific function:

• Cell Body (Soma): Contains the nucleus and organelles; responsible for the metabolic activities of the neuron.

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

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

• Myelin Sheath: Fatty layer that covers the axon, increasing the speed of impulse transmission.

• Terminal Branches of Axon: Endings that release neurotransmitters to communicate with other neurons.

Synapses and Action Potentials

Synapses are the gaps between neurons where communication occurs via neurotransmitters. The process of transmitting a signal across a synapse is essential for neural communication.

• Action Potentials: Electrical impulses that travel down the axon, leading to the release of neurotransmitters at the synapse.

• All-or-None Response: Neurons either fire completely or not at all; the strength of the action potential does not vary.

Example: When you touch a hot surface, sensory neurons fire action potentials that travel to your brain, resulting in a quick withdrawal response.

Neurotransmitters

Neurotransmitters are chemicals that transmit signals across synapses between neurons. They play a crucial role in regulating mood, behavior, and cognition.

• Dopamine: Involved in movement, motivation, and reward. Low levels are associated with Parkinson's disease; high levels with schizophrenia.

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

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

Reuptake: The process by which neurotransmitters are reabsorbed by the presynaptic neuron after transmission.

SSRIs (Selective Serotonin Reuptake Inhibitors): Medications that block the reuptake of serotonin, increasing its availability in the synapse.

The Nervous System

Types of Neurons

• Motor Neurons: Carry signals from the central nervous system to muscles and glands.

• Sensory Neurons: Transmit sensory information from receptors to the central nervous system.

• Interneurons: Connect neurons within the central nervous system.

Nervous System Divisions and Functions

• Central Nervous System (CNS): Brain and spinal cord; processes information and coordinates activity.

• Peripheral Nervous System (PNS): All nerves outside the CNS; connects the CNS to limbs and organs.

• Somatic Nervous System: Controls voluntary movements.

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

• Sympathetic Nervous System: Prepares the body for 'fight or flight' responses.

• Parasympathetic Nervous System: Promotes 'rest and digest' activities.

Endocrine System and Hormones

The endocrine system uses hormones to regulate bodily functions. Hormones differ from neurotransmitters in that they travel through the bloodstream and have longer-lasting effects.

• Pituitary Gland: The 'master gland' that controls other endocrine glands.

• Adrenal Gland: Produces adrenaline and cortisol, involved in stress responses.

Brain Regions and Structures

• Cerebellum: Coordinates movement and balance.

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

• Medulla: Regulates vital autonomic functions.

• Limbic System: Involved in emotion and memory. Key structures include:

  • Basal ganglia

  • Hippocampus

  • Thalamus

  • Hypothalamus

  • Amygdala

Lobes and Cortices of the Brain

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

• Cerebral Cortex: Outer layer responsible for higher-order functions.

• Frontal Lobe: Involved in decision-making, planning, and movement.

• Pre-Frontal Cortex: Associated with complex behaviors and personality.

• Parietal Lobe: Processes sensory information.

• Somatosensory Cortex: Receives sensory input from the body.

• Motor Cortex: Controls voluntary movements.

• Auditory Cortex: Processes sound information.

• Visual Cortex: Processes visual information.

Homunculus

The homunculus is a visual representation of the body within the brain, showing which areas of the cortex correspond to different body parts. It highlights the disproportionate representation of certain areas, such as the hands and face.

Neuropsychology

Neuroplasticity

Neuroplasticity refers to the brain's ability to change and adapt in response to experience, learning, or injury. It is greater in children but persists throughout adulthood.

Brain Lateralization

Brain lateralization refers to the specialization of the left and right hemispheres for different functions. For example, language is typically processed in the left hemisphere.

• Broca's Area: Involved in speech production.

• Wernicke's Area: Involved in language comprehension.

Neurological Disorders

• Traumatic Brain Injury (TBI): Damage to the brain caused by external force.

• Chronic Traumatic Encephalopathy (CTE): Progressive degeneration due to repeated head injuries.

• Meningitis: Inflammation of the protective membranes covering the brain and spinal cord.

• Amyotrophic Lateral Sclerosis (ALS): Progressive neurodegenerative disease affecting motor neurons.

• Alzheimer's Disease: Neurodegenerative disorder characterized by memory loss and cognitive decline.

Brain Imaging Techniques

• CT Scan: Uses X-rays to create detailed images of the brain.

• PET Scan: Measures metabolic activity using radioactive tracers.

• MRI: Uses magnetic fields to produce detailed images of brain structures.

• fMRI: Measures brain activity by detecting changes in blood flow.

Consciousness

Selective Attention and Inattentional Blindness

Consciousness is the awareness of ourselves and our environment. Selective attention refers to focusing on a particular stimulus while ignoring others, whereas selective inattention is the failure to notice certain stimuli. Inattentional blindness occurs when we fail to perceive an unexpected stimulus in our field of vision.

Sleep

Circadian Rhythm and Sleep Stages

The circadian rhythm is the body's internal clock that regulates sleep-wake cycles. The pineal gland and melatonin play key roles in maintaining this rhythm.

• Stage 5 Sleep/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: Difficulty falling or staying asleep.

• Sleep Apnea: Breathing interruptions during sleep.

• Narcolepsy: Sudden, uncontrollable episodes of sleep.

• Parasomnias: Abnormal behaviors during sleep, such as nightmares, night terrors, and somnambulism (sleepwalking).

Sleep Stages

• Stage N1: Light sleep.

• Stage N2: Deeper sleep.

• Stage N3: Deepest, most restorative sleep.

Research shows that sleep loss negatively affects cognitive performance, mood, and physical health.

Sensation and Perception

Definitions and Processes

• Sensation: The process by which sensory receptors receive stimuli from the environment.

• Perception: The interpretation and organization of sensory information by the brain.

Sensation and perception are closely related but distinct processes. Sensory receptor cells transduce energy into neural impulses, which are then interpreted by the brain.

Thresholds and Sensory Adaptation

• Absolute Threshold: The minimum stimulus intensity required for detection.

• Difference Threshold (Just Noticeable Difference): The smallest change in stimulus intensity that can be detected.

• Sensory Adaptation: Reduced sensitivity to constant stimuli over time.

Vision

• Cones: Photoreceptors responsible for color vision and detail.

• Rods: Photoreceptors sensitive to low light.

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

Visual stimuli are processed in the occipital lobe. The visual cortex interprets light waves as images.

Color Vision

• Subtractive Color Mixing: Mixing pigments, resulting in darker colors.

• Additive Color Mixing: Mixing light, resulting in lighter colors.

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

• Opponent-Process Theory: Suggests color perception is controlled by opposing pairs (e.g., red-green, blue-yellow).

Audition (Hearing)

• Ear Structure: Includes the outer ear, middle ear (bones: ossicles), and inner ear (cochlea, vestibular organs).

• Auditory Nerve: Transmits sound information to the brain.

• Sound Localization: Determining the source of a sound using cues such as time and intensity differences.

• Deafness: Can be conductive (problems with sound transmission) or sensorineural (damage to inner ear or nerve).

Somatosensation

• Kinaesthesia: Sense of body movement.

• Vestibular Sense: Sense of balance and spatial orientation.

• Tactile Sense: Sense of touch.

• Phantom Limb Syndrome: Sensation of pain or movement in a limb that has been amputated.

Perception and Gestalt Principles

• Top-Down Processing: Perception driven by cognition and prior knowledge.

• Bottom-Up Processing: Perception driven by sensory input.

• Gestalt Principles: Rules for organizing visual information, including proximity, similarity, closure, continuity, and figure-ground.

Depth Perception

• Monocular Cues: Interposition, linear perspective.

• Binocular Cues: Retinal disparity, convergence/divergence.

Eye Structures

• Pupil: Regulates the amount of light entering the eye.

• Lens: Focuses light onto the retina.

• Retina: Contains photoreceptors (rods and cones).

• Optic Nerve: Transmits visual information to the brain.

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

Gustation and Olfaction

• Chemical Senses: Taste and smell; called chemical senses because they detect molecules in the environment.

• Taste Buds: Sensory organs for taste; detect sweet, sour, salty, bitter, and umami flavors.

• Relationship Between Smell and Taste: These senses work together to create flavor perception.

HTML Table: Comparison of Nervous System Divisions

Division	Main Function	Example
Central Nervous System (CNS)	Processes information, coordinates activity	Brain interpreting sensory input
Peripheral Nervous System (PNS)	Connects CNS to limbs and organs	Reflex actions
Somatic Nervous System	Controls voluntary movements	Moving your arm
Autonomic Nervous System	Regulates involuntary functions	Heartbeat, digestion
Sympathetic Nervous System	Prepares body for action	Fight or flight response
Parasympathetic Nervous System	Promotes rest and recovery	Slowing heart rate after stress

Key Equations

• Action Potential: $V = V_{rest} + (I_{stimulus} \times R)$

• Threshold: $I_{stimulus} \geq I_{threshold}$

Additional info: Academic context and definitions have been expanded for clarity and completeness. Table entries and equations are inferred from standard psychology curriculum.