Sensory Systems Lecture Notes

Flashcards covering the sensory systems, including receptor cells, chemoreceptors, mechanoreceptors, and photoreceptors.

How do sensory receptor cells convert stimuli into action potentials?

Sensory receptor cells transduce physical and chemical stimuli into neural signals, starting with a receptor protein that opens or closes ion channels, changing the membrane potential.

How do sensory receptor proteins respond to stimuli?

Sensory receptor proteins respond to stimuli by directly or indirectly opening or closing ion channels; chemoreceptors and photoreceptors influence ion channels indirectly by activating G proteins and second messengers.

What do sensory systems include?

Sensory systems include sensory cells, associated structures, and neural networks that process information.

What is sensory adaptation?

Diminishing response to repeated stimulation, enabling animals to ignore background conditions but remain sensitive to changing/new stimuli.

What are chemoreceptors?

Receptor proteins that bind to specific molecules (ligands), responsible for taste and smell, and monitor internal environments (e.g., CO2 levels in blood).

What is olfaction?

Sense of smell, involving olfactory receptors (neurons) in the nasal cavity.

What is an odorant?

Molecule that binds to a specific olfactory receptor protein on the cilia of olfactory receptor neurons (ORNs).

What are pheromones?

Chemical signals used to communicate among individuals of the same species (e.g., female silkworm moths releasing bombykol).

What is gustation?

Sense of taste, dependent on clusters of chemoreceptors called taste buds embedded in the tongue epithelium.

What are the five human tastes?

Salty, sour, sweet, bitter, and umami.

What are mechanoreceptors?

Sensory cells that respond to mechanical force by opening cation channels, registering intensity as a graded receptor potential.

What are the types of tactile receptors?

Merkel’s discs (adapt slowly, continuous touch), Meissner’s corpuscles (adapt quickly, change information).

What are some other types of tactile receptors?

Ruffini endings (deep, adapt slowly, low-frequency vibration), Pacinian corpuscles (deep, adapt rapidly, high-frequency vibration).

What is the function of mechanoreceptor cells in muscles, tendons, and ligaments?

Constant information to the CNS on limb position and stresses on muscles/joints, essential for posture and coordination.

What are muscle spindles?

Mechanoreceptors in muscle cells (stretch receptors) that generate action potentials when the muscle is stretched.

What is the function of the Golgi tendon organ in tendons and ligaments?

Provides information about the force generated by a contracting muscle and prevents muscle tearing.

What are hair cells?

Mechanoreceptors in auditory and vestibular systems with stereocilia that bend in response to pressure waves.

What are sounds?

Pressure waves collected by the pinnae and directed to the auditory canal.

What are the parts of the human ear?

Outer ear (pinna, auditory canal, tympanic membrane), middle ear (ossicles, eustachian tube), and inner ear (vestibular system, cochlea).

What is the middle ear?

Air-filled cavity connected to the throat via the eustachian tube; contains ossicles (malleus, incus, stapes).

What two sets of canals is the inner ear composed of?

Vestibular system (balance) and cochlea (hearing).

What is the Organ of Corti?

Sits on the basilar membrane and transduces pressure waves into action potentials; stereocilia are embedded in the tectorial membrane.

How do pressure waves affect the basilar membrane?

High-frequency waves flex the basal end; low-frequency waves flex the apical end.

What are the two main types of deafness?

Loss of function of tympanic membrane or ossicles (conduction); damage to inner ear or auditory nerve pathways (nerve).

What is the vestibular system?

Detects head position and movement, essential for balance and eye movements; includes semicircular canals and the vestibule (saccule and utricle).

What causes motion sickness?

Vestibular system and visual system produce conflicting information.

What is photosensitivity?

Sensitivity to light, based on visual pigments in photoreceptor cells that transform light energy into action potentials.

What are some examples of invertebrate visual systems?

Flatworms (eye cups for directional info), arthropods (compound eyes with ommatidia).

Describe the vertebrate eye.

Surrounded by sclera, includes the cornea, iris (controls light amount via pupil size), and lens (focuses images).

What is the retina?

Five layers of cells that light must pass through.

What are Opsins?

Proteins with 11-cis-retinal that absorb photons of light; rhodopsin is the most common opsin.

What are rod cells?

Highly light-sensitive, perceive shades of gray in dim light; depolarized in the dark and hyperpolarized in response to light.

What are cone cells?

Function at high light levels, responsible for high-acuity color vision.

How does light absorption close sodium channels in rod cells?

Rod cells have open Na+ channels in the dark, which close when rhodopsin absorbs light, activating transducin and PDE, leading to hyperpolarization.

Where are cone cells concentrated?

Located in the fovea, have low sensitivity to light.

What is color blindness?

Loss of function of one or more types of cone cells.

How is information processed in the retina?

Changes in photoreceptor membrane potential alter neurotransmitter release onto bipolar cells, affecting ganglion cell action potential firing.