PSY1BNB WEEK 1 – Sensory Systems, Introduction, Taste, & Smell

These flashcards cover key vocabulary terms and definitions related to sensory systems, taste, and smell as introduced in the first week of the Sensory Systems lecture.

What is sensation?

The physical process where sense organs detect environmental stimuli and send that information to the brain

What is perception?

The brain’s active, continuous process of selecting, organizing, interpreting, and consciously experiencing sensory input

Difference between sensation and perception

Sensation = detecting energy; Perception = interpreting and giving meaning to that energy

Main functions of sensory systems

Detect and translate physical energy or chemicals into neural signals (sensory transduction)

What is sensory transduction?

Conversion of physical or chemical energy into a neural signal

What are sensory receptor organs?

Specialized cells that convert sensory energy into neural activity

What is an adequate stimulus?

The specific type of stimulus a sensory organ is adapted to detect (e.g. light for eyes, sound for ears)

Examples of adequate stimuli

Light → vision; Sound → hearing; Chemicals → taste/smell; Pressure → touch

How are sensory systems classified?

By modality and adequate stimulus type (mechanical, visual, chemical, electrical, magnetic)

Mechanical sensory examples

Touch, pain, hearing, vestibular (balance)

Chemical sensory examples

Smell and taste

Electrical and magnetic sensory examples

Electroreception (detecting electric fields) and magnetoreception (detecting Earth’s field)

Restricted range of responsiveness

Each receptor type responds to only a narrow range of stimulus energies

How do receptor cells trigger action potentials?

Stimulus → graded potential → if threshold reached → action potential

What ions move during an action potential?

Na⁺ enters, K⁺ leaves, temporarily reversing membrane polarity

Why are action potentials “all-or-nothing”?

Once threshold is reached, a full action potential always occurs; strength encoded by firing rate

What is firing rate?

Number of action potentials per second; increases with stimulus intensity

How does the brain recognize sensations?

Via labeled-line pathways—distinct nerve tracts for each sensory modality

How many cranial nerves exist?

12 pairs (some sensory, some motor, some mixed)

How many spinal nerves exist?

31 pairs; dorsal roots = sensory, ventral roots = motor

Stimulus intensity coding

Stronger stimuli → higher action-potential frequency

Stimulus location coding

Determined by which receptor cells are activated and their position

What is adaptation?

Reduced receptor response during constant stimulation

What is suppression?

Reduction of sensory input via accessory structures or top-down brain control

What are neural relays?

Pathways transmitting sensory info from receptor to cortex, often via the thalamus

What is a receptive field?

The specific area where a stimulus alters activity in a sensory neuron

What is attention in sensory processing?

Selective focus that enhances processing of certain stimuli

What is coding in sensory systems?

Patterns of action potentials representing stimulus features

What is range fractionation?

Different receptors respond to different intensity ranges, allowing wide-range encoding

What are tonic receptors?

Respond slowly and show little adaptation

What are phasic receptors?

Rapidly adapt to constant stimuli

What are the five basic tastes?

Sweet, sour, salty, bitter, and umami

Possible sixth taste

Fats (lipid detection)

Where are taste receptors located?

Within taste buds on papillae of tongue, mouth, and throat

Taste receptor cell lifespan

≈ 2 weeks

Why is the “tongue map” inaccurate?

All regions can detect all five tastes, though sensitivity varies

How are salty and sour tastes detected?

Ionotropic receptors directly respond to Na⁺ or H⁺ ions

How are bitter, sweet, and umami detected?

Metabotropic GPCR receptors activated by molecules → neurotransmitter release

Which cranial nerves carry taste info?

Facial (VII), Glossopharyngeal (IX), and Vagus (X)

Where is taste processed in the brain?

Gustatory cortex → integrates with other senses in orbitofrontal cortex

Role of orbitofrontal cortex

Combines taste, smell, and visual cues to form flavor perception

How many odors can humans discriminate?

Up to about 10 000

Main functions of smell

Detect airborne chemicals for food safety, predators, mates, and social signals

Why does olfactory sensitivity vary?

Differences in receptor number and gene variants across species and individuals

What is the olfactory epithelium?

Tissue in nasal cavity containing receptor neurons that project to the olfactory bulb

Describe olfactory transduction

Odorant binds GPCR → depolarization → action potential to olfactory bulb

What does the olfactory bulb do?

First relay that organizes odor information before sending it to cortex

How is odor information coded?

Unique combinations of receptor activations create distinct odor perceptions

How is smell linked to memory and emotion?

Olfactory pathways connect to limbic areas like amygdala and hippocampus

What is chemosensory dysfunction?

Reduced or lost ability to smell or taste (anosmia, age-related loss, disease marker)

Which diseases can smell loss indicate?

Neurodegenerative conditions such as Parkinson’s or Alzheimer’s disease

How does aging affect olfaction?

Olfactory sensitivity declines with age

Learning outcomes for sensory systems

Distinguish sensation vs perception; explain transduction, receptor functions, and neural coding

Learning outcomes for taste and smell

Explain taste receptor mechanisms, involved cranial nerves, and olfactory pathways to cortex