Sensory Physiology Flashcards
What happens when you see, feel, smell, taste, or hear something?
A receptor receives a signal in the form of a molecule, light/sound waves, heat, physical deformation, or pain
Special senses
Involve specialized organs such as the inner ear, eye, nose, tongue
Vision, hearing, taste, smell, equilibrium
Somatic senses
Do not involve specialized organs
Touch, temperature, pain, itch, proprioception or kinesthesia
Types of receptors
Chemo
Mechano
Photo
Thermo
Types of sensory receptors/cells
Simple receptors - neurons with free nerve endings (dendrites) whose axons may or may not be myelinated; common locations - skin, nose, pain sensors
Complex neural receptors - neurons where nerve endings are enclosed in connective tissue capsules; more protected nerve endings allow for varied input; common for touch
Receptor cell (NOT a neuron) - cells that release neurotransmitter onto sensory neurons; fires a graded potential; ex: hair cells found in ear
Receptive fields
Skin surface where primary sensory neurons receive signals.
Convergent receptive fields - the receptive fields of multiple primary sensory neurons overlap to form one large secondary receptive field - allows simultaneous subthreshold stimuli to sum at the secondary sensory neuron and initiate an action potential - only one signal goes to the brain
Small receptive fields are found in more sensitive areas where fewer neurons converge; each stimulus activates separate pathways to the brain
Receptor adaptation
Adaptation is the decline of the electric responses of a receptor neuron over time in spite of the continued presence of an appropriated stimulus of constant strength
Tonic receptors - slowly adapting receptors
Phasic receptors - rapidly adapt to a constant stimulus and turn off
Skin sensory receptors
Includes both simple and complex receptors
Free nerve endings - temperature, noxious stimuli, hair movement
Meissner’s corpuscles - flutter, stroking
Pacinian corpuscles - vibration
Ruffini corpuscles - stretch of skin
Market receptors - steady pressure, texture
Primary sensory receptor for each sense
Smell - sensory neuron
Taste - receptor cell —> sensory neuron
Hearing - receptor cell (mechanoreceptors) —> sensory neuron
Vision - receptor cell (photoreceptors) —> sensory cell
Touch/pain/temp/itch - simple and complex sensory neurons
How do odorant molecules travel to the olfactory nerve?
Olfactory neurons in the nose have dendrites that protrude into the mucous layer of the nose. When odorant molecules dissolve into this mucous layer, they bind to receptors on the dendrites which causes information to be transmitted from the neuron (which is part of the olfactory nerve) to the olfactory bulb. G-proteins are involved in the olfactory neuron.
3 components of taste
Gustation - taste buds (50-100 taste cells)
Olfaction
Tactile sensation - from pill form papillae which are the bumps on the tongue
What is a taste bud?
A grouping of taste cells with an opening to the tongue surface called the taste pore. Each taste cell most likely senses only one type of ligand. Taste cells fire graded potentials in order to signal to primary sensory neurons.
Taste cells that use a GPCR
Sweet, umami, and bitter
Signal transduction in a sweet, umami, or bitter taste cell
A GPCR transmembrane protein binds sweet, umami, or bitter ligands. The G-protein is called gustucin. (Review how G-proteins initiate a cell signaling pathway). Ca2+ ions are released from the endoplasmic reticulum causing the cell to depolarize and trigger a graded potential which results in the release of ATP. ATP acts as a signal for the primary gustatory neurons and also as a paracrine signal for neighboring sour taste cells.
Essential roles of the external, middle, and inner ear
External - directing sound waves to the ear
Middle - converting sound waves into fluid waves
Inner - hair cells respond to fluid waves and signal is transmitted to the auditory nerve
