Sensory Transduction

Sensory Transduction

conversion of physical stimuli into electrochemical signals for transmission to the CNS

Epithelial Cells

specialized cells that form the lining of various surfaces and cavities in the body; cannot form own AP

Receptor Potential

Local chance in the sensory Vm; determines the rate and pattern of AP firing in a sensory neuron, which can then propagate to the CNS

External Sensation

Detection of stimuli from outside the body; includes vision, hearing, touching, smelling, tasting

Internal Sensation

Detection of stimuli from internal organs and tissues; ie balance, body position, movement, pain, internal milieu

Chemoreception Mechanisms

Chemoreceptors detect external and internal chemicals, facilitating taste (gustation) and smell (olfaction), as well as monitoring internal chemical states like blood pH and oxygen levels.

Chemorecptors

respond to external or internal extracellular chemical and generate a receptor potential

Papillae

small, nipple-like structures on the tongue's surface that contain taste buds

Taste Buds

small sensory organs located on the tongue that are responsible for detecting the five basic tastes: sweet, sour, salty, bitter, and umami.

Taste Receptor Cells

respond to chemical stimuli from food and send signals to the brain via the somatic nervous system.

Microvilli

hair-like structures that interact with dissolved food molecules (tastants) through a small opening called a taste pore, allowing for the detection of taste signals.

Olfactory Receptor Neurons

in the olfactory epithelium detect odorants via GPCRs, initiating action potentials that transmit smell information to the brain.

Olfactory Epithelium

a specialized epithelial tissue located in the nasal cavity that is involved in the sense of smell; It contains olfactory receptors that detect and transmit olfactory information to the brain

Cornea

the transparent front part of the eye that covers the iris, pupil, and anterior chamber

Lens

a transparent, biconvex structure located behind the iris of the eye that focuses light onto the retina, allowing for clear vision

Retina

a thin layer of tissue located at the back of the eye, containing cells that are sensitive to light and trigger nerve impulses that pass via the optic nerve to the brain, where a visual image is formed.

Iris

colored part of the eye that surrounds the pupil and controls the amount of light entering the eye.

Pupil

the black circular opening in the center of the iris of the eye that regulates the amount of light entering the eye

Ocular Muscles

a group of six muscles that control eye movement

Photoreceptor Cells

highly specialize neurons on outer surface of retina that transduce and amplify the detection of photons into a receptor potential; hyperpolarized by light and depolarized by dark

Interneurons

type of neuron located entirely within the central nervous system (CNS) that serves as a connector between sensory neurons and motor neurons.

Rods

Specialized for monochromatic dark adapted vision

Cones

Specialized for color sensitive light adapted vision

Fovea

Small pit in retina that receives center of focus

Photopigments

GPCRs that respond to protons

Mechanotransduction by Hair Cells

Relied on by hearing and vestibular sensation

Hair Receptor Potential Process

Displacement of the endolymph relative to the hair cell causes the bundle of villi to bend, and this affects the hair cell Vm; Movement toward the kinocilium priduces a depolarizing receptor potential and movement away from the kinocilium produces a hyperpolarizing receptor potential

Stereovilli

specialized hair-like structures found on the surface of sensory cells in the inner ear and the vestibular system; play a crucial role in hearing and balance by converting mechanical stimuli into electrical signals.

Kinocilium

tallest of a bundle of sterovilli

Endolymph

Found inside the membranous labyrinth; Similar to ICF; h: Plays a critical role in hearing and balance by facilitating the conversion of sound vibrations into electrical signals that the brain interprets.

Perilymph

Located in the bony labyrinth, surrounding the membranous labyrinth and filling the spaces between it and the bone; Similar to ECF; Acts as a cushion for the delicate structures of the inner ear and transmits sound vibrations from the outer ear to the endolymph

Outer Ear

Visible portion of the war and external auditory canal

Middle Ear

Eardrum and ossicles

Inner Ear

Oval window, round window, eustachian tube and membranous labyrinth

Afferent Sensory nerve

Information from the inner ear is transmitted to the brain via a cranial nerve

Otolithic Organs

Sense linear acceleration and position of the head

Ear Receptor Potential

Linear Acceleration: inertia of the otoconia displaces the membrane, deflecting the stereovilli, which produces a receptor potential

Angular Acceleration: Sudden rotation of semicircular canals, the endolymph stays behind which displaces the cupula and this bends the hair cell bundle which produces a receptor potential

Semicircular Canals

Sense angular acceleration caused by sudden head rotations

Skin Mechanoreceptors

specialized for rapid vibrations, slow vibrations, or constant pressure, and for deep pressure or light touch

Thermoreceptive Neurons

Detect Cold and Hot mostly extreme

Nociceptors

Pain receptors that produce pain as a warning that body tissue is being damaged

Proprioception

Perception of the position and movement of the body

Sensory Modalities

include external sensations and internal sensations as well as

unconscious internal signals for autonomic regulation

Photoreceptor Function

Photoreceptors in the retina (rods and cones) convert light into receptor potentials through photopigments, facilitating vision under different light conditions and color detection.

Phototransduction Process

Phototransduction involves GPCR activation in photoreceptors, leading to cGMP hydrolysis, closing of cation channels, hyperpolarization, and reduced neurotransmitter release in response to light.

Mechanotransduction in Hair Cells

Hair cells in the auditory and vestibular systems transduce mechanical stimuli into electrical signals via bending of stereovilli, activating ion channels and generating receptor potentials.

Skin Somatic Receptors

The skin contains various somatic receptors, such as mechanoreceptors for touch and vibration, thermoreceptors for temperature changes, nociceptors for pain, and proprioceptors for body position.

Synaptic Integration and AP Encoding

Sensory receptor cells generate receptor potentials that

modulate the firing rate and pattern of action potentials in sensory neurons, encoding information for transmission to the CNS.