0-1 Chapter 16 - sense Organs Flashcards
(275 cards)
sense organs
nerve tissue surrounded by other tissues that enhance response to certain type of stimulus
•added epithelium, muscle or connective tissue
transduction
the conversion of one form of energy to another
–fundamental purpose of any sensory receptor
receptor potential
small, local electrical change on a receptor cell brought about by an initial stimulus
•results in release of neurotransmitter or a volley of action potentials that generates nerve signals to the CNS
sensation
a subjective awareness of the stimulus
–most sensory signals delivered to the CNS produce no conscious sensation
Receptors Transmit Four Kinds of Information
Modality
Location
Intensity
Duration
Modality
type of stimulus or the sensation it produces
–vision, hearing, taste
labeled line code
all action potentials are identical. Each nerve pathway from sensory cells to the brain is labeled to identify its origin, and the brain uses these labels to interpret what modality the signal represents
Location
encoded by which nerve fibers are issuing signals to the brain
receptive field
area that detects stimuli for a sensory neuron
sensory projection
brain identifies site of stimulation
projection pathways
the pathways followed by sensory signals to their ultimate destination in the CNS
Intensity
encoded in 2 ways
Strength
frequency
Duration
how long the stimulus lasts
sensory adaptation
if stimulus is prolonged, the firing of the neuron gets slower over time, and we become less aware of the stimulus
phasic receptor
generate a burst of action potentials when first stimulated, then quickly adapt and sharply reduce or stop signaling even though the stimulus continues
tonic receptor
adapt slowly, generate nerve signals more steadily
Classification of Receptors by
modality
origin of stimuli
distribution
by modality
–thermoreceptors, photoreceptors, nociceptors, chemoreceptors, and mechanoreceptors
origin of stimuli
–exteroceptors -detect external stimuli
–interoceptors -detect internal stimuli
–proprioceptors -sense body position and movements
by distribution
–general (somesthetic) senses -widely distributed
–special senses -limited to head
•vision, hearing, equilibrium, taste, and smell
General Senses
structurally simple receptors
–one or a few sensory fibers and a little connective tissue
unencapsulated nerve endings
•dendrites not wrapped in connective tissue
–free nerve endings
–tactile (Merkel) discs
–hair receptors (peritrichial endings
free nerve endings
–for pain and temperature
–skin and mucous membrane
tactile discs
–for light touch and texture
–associated with Merkel cells at base of epidermis