Exercise 22+26: General Sensation, Olfaction and Taste Flashcards
Sensory receptors
Structures specialized to respond to stimuli
General senses
Touch, pressure, pain, temperature, stretch, movement, vibration.
General sensory receptors
React to touch, pressure, pain, heat, cold, stretch, vibration, and changes in body position.
Distributed throughout the body.
Special senses
Vision, hearing, equilibrium, smell, taste
Sense organs
A structure that combines nervous tissue with other tissues that enhance the response to a certain type of stimulus
Examples: ear, eye, or small localized groups of receptors
Exteroreceptors
Respond to stimuli arising outside the body
Found near the body surface
Sensitive to touch, pressure, pain, and temperature
Examples: simple cutaneous receptors in the skin; vision apparatus of the eye; includes the special sense organs
Interoreceptors (visceroreceptors)
Respond to stimuli arising within the body; found in the internal visceral organs and include stretch receptors (in walls of hollow organs), chemoreceptors, and others
Proprioceptors
Sense the position and movements of the body or its parts; occur in muscles tendons and joint capsules; monitor the degree of stretch of those structures
Free (naked) dendritic endings
Location: most body tissues; especially the epithelia and connective tissues (skin and mucous membranes)
Stimulus type: pain, heat, and cold
Merkel discs
Location: basal layer of epidermis of skin
Stimulus type: light touch and texture
Hair follicle receptors
Location: wrap around the base of a hair follicle
Stimulus type: light touch and bending of hairs
Meissner’s corpuscles (tactile corpuscles)
Location: dermal papillae of hairless skin
Stimulus type: light touch and pressue
Ruffini’s corpuscles (bulbous corpuscles)
Location: deep in dermis, hypodermis, and joint capsules
Stimulus type: deep pressure and stretch
Pacinian corpuscles (lamellar corpuscles)
Location: dermis, subcutaneous tissue, periosteum, tendons, joint capsules
Stimulus type: deep pressure, stretch, vibration
Muscle spindles
Location: skeletal muscle
Stimulus type: muscle stretch (proprioception)
(muscle spindle is a bundle of 7-8 modified muscle fibers)
Intrafusal cells
Specialized slender skeletal muscle cells found in muscle spindles. Nerve endings of sensory neurons coil around the intrafusal cells.
Tendon organs
Location: tendons
Stimulus type: tendon stretch, tension (proprioception)
(tendon organs are proprioceptors located a tendon)
Transducers
Sensory receptors act as transducers, changing environmental stimuli into nerve impulses that are sent to the CNS
Punctuate distribution
Sensory receptors have discrete locations and cluster at certain points
What are the four qualities of cutaneous sensation?
Tactile (touch), heat, cold, pain
Tactile two-point discrimination test
Tests tactile localization (ability to determine which portion of skin has been touched)
The greater the receptor density, the more precisely you would expect to locate point of stimulation
Two-point threshold
The smallest distance at which two points of contact can be felt
Adaptation
When a stimulus is applied for a long time without movement, the firing of the neuron slows down and conscious awareness of the stimulus declines or is lost
(ex: adapting to hot bath water)
Referred pain
Pain is perceived as coming from one area of the body when a different area is receiving the painful stimulus (pain is referred to a different area)
Projection
Transmission of information from a receptor to a specific location in the cerebral cortex
How are the senses of taste and smell related?
Receptors for taste and smell are both chemoreceptors (they respond to chemicals in aqueous solution (in saliva for taste, or in fluids of nasal membranes for smell)
Olfactory epithelium
Organ of smell, covers the superior nasal concha
What types of cells are found in the olfactory epithelium?
Olfactory receptor cells, supporting cells, and olfactory stem cells
What types of papillae are found on the tongue?
Filiform, fungiform, circumvallate, foliate
Taste buds
Located in papillae (peglike projections of the mucosa), found in fungiform and circumvallate mostly
Circumvallate papillae
Arranged in a V on posterior surface of tongue
Foliate papillae
Form parallel ridges on sides of tongue
Fungiform papillae
More numerous, mushroom shaped, contain about 3 tastebuds
Filiform papillae
Tiny spikes without tastebuds
Anatomy of a taste bud/what does each taste bud consist of
Gustatory epithelial cells (receptors for taste) that have gustatory hairs (long microvilli) that project through a taste pore Basal cells (dynamic stem cells) Supporting cells (insulate the receptor)
Taste bud
Contain specific receptors for taste
What are the five basic taste sensations?
Sweet, Salt, Sour, Bitter, Umami
What chemical substance elicits the taste sensation: sweet?
Alcohol, sugars, saccharin, and some amino acids
What chemical substance elicits the taste sensation: salt?
Metal ions
What chemical substance elicits the taste sensation: sour?
Hydrogen ions
What chemical substance elicits the taste sensation: bitter?
Alkaloids, such as quinine or nicotine
What chemical substance elicits the taste sensation: umami?
Glutamate (an amino acid)
What are other factors that influence taste (other than olfaction)?
Texture, temperature
Mechanoreceptors
Respond to touch, pressure, vibration, stretch and itch
Thermoreceptors
Sensitive to changes in temperature
Photoreceptors
Respond to light energy (e.g., retina)
Chemoreceptors
Respond to chemicals (e.g., smell, taste, changes in blood chemistry)
Nociceptors
Sensitive to pain-causing stimuli
