Ch 2: Sensation and Perception Flashcards
Explain the structure and function of the organ of Corti.
The hearing apparatus
Housed in the middle scala of the cochlea, it rests on a thin flexible membrane (basilar membrane). It is composed of thousands of hair cells bathed in endolymph
What happens in the cochlea to allow us to hear?
Sound enters the cochlea through the oval window, causing vibrations in perilymph, which are transmitted to the basilar membrane. The round window permits perilymph to move around. The hair cells on organ of Corti convert the physical stimulus into an electrical signal to be carried to CNS
vestibule
the portion of the bony labyrinth containing the utricle and saccule. Used as part of the balancing apparatus and to determine orientation in 3D space
otoliths
resist motion of acceleration, bending and stimulating the underlying hair cells, which send a signal to the brain
semicircular canals
sensitive to rotational acceleration
Which cochlear structure is sensitive to linear acceleration?
vestibule
Which cochlear structure is sensitive to rotational acceleration?
semicircular canals
When you rotate your head, what is resisting this motion in the cochlea, bending the underlying hair cells?
ampulla
What is the role of inferior colliculus in the auditory pathway?
it is involved in the startle reflex and helps keep the eyes fixed on a point while the head is turned (vestibulo-ocular reflex)
What is the role of superior colliculus in the visual pathway?
it controls some responses to visual stimuli and reflexive eye movements
Describe the auditory pathway
hair cells < vestibulocochlear nerve < medial geniculate nucleus (MGN) of the thalamus < auditory cortex in temporal lobe for sound processing
some information sent to superior olive (localizes sound) and inferior colliculus (startle reflex, vestibulo-ocular reflex)
How do hair cells in the organ of Corti convert the physical stimulus into electrical signal?
When vibrations reach the basilar membrane, hair cells start swaying back and forth. This swaying causes the opening of ion channels, causing a receptor potential
Where in the cochlea would you most typically find vibrations of the basilar membrane if a high-frequency pitch was encountered?
close to the oval window
Where in the cochlea would you most typically find vibrations from low-frequency pitches?
at the apex, away from the oval window
how would the brain differentiate between pitches of sounds?
cochlea is tonotopically organized; high frequency pitches stimulate hair cells closer to the oval window, while high frequency pitches stimulate hair cells farther from the oval window (at the apex)
What is sensation
a raw signal from the receptors in the PNS forwarded to the CNS in the form of action potentials and neurotransmitters
what is transduction
the conversion of physical, electromagnetic auditory, and other information from our internal and external environment to electrical signals in the nervous system
aligns with sensation
What is perception
the processing of external sensory information and internal activities of CNS to make sense of its significance.
Helps us make sense of the world
What is the general sensory pathway in which a stimulus undergoes to be processed?
stimulus < receptors (sensory cells or nerve endings) < ganglia (transmits data from receptors to CNS) < projection areas, which further analyzes the sensory input
what is threshold
the minimum amount of a stimulus that renders a difference in perception
what is absolute threshold
the minimum of stimulus energy that is needed to activate a sensory system (a threshold in sensation, not perception). A stimulus below this threshold never reaches the CNS
how BRIGHT, how LOUD, how INTENSE a stimulus must be before it is sensed
What is the threshold of conscious perception
the minimum of stimulus energy needed for it to reach higher order brain regions that control attention and consciousness
a stimulus below this threshold arrives at the CNS, but are not perceived (subliminal perception)
What is the difference threshold or “just-noticeable difference”
the minimum difference in magnitude between two stimuli before one can perceive this difference
more important to focus on the ratio between change in stimulus and the original value rather than the actual difference (formalized by Weber’s Law)
What is Weber’s Law?
states that there is a constant ratio between the change in stimulus magnitude needed to produce a jnd and the magnitude of the original stimulus
for higher magnitude stimuli, actual difference must be larger to produce a jnd
