Sensation and Perception

receptor cells

a specialized cell that responds to a particular energy or substance in the internal or external environment and converts it into a change in the electrical potential across its membrane

stimuli

a drug that enhances the excitability of neurons

labeled lines

each nerve input to the brain reports only a particular type of information

receptor potential/ generator potential

a local change in the resting potential of a receptor cell in response to stimuli, which may initiate an action potential

sensory transduction

the process in which a receptor cell converts energy in a stimulus into a change in the electrical potential across its membrane

Pacinian corpuscle/ lamellated corpuscle

a skin receptor cell type that detects vibration and pressure

Meissner’s corpuscles/ tactile corpuscle

a skin receptor that detects light touch, responding especially to changes in stimuli

Markel’s discs

a skin receptor cell type that detects light touch, responding especially to edges and isolated points on a surface

Ruffini corpuscles

a skin receptor cell type that detects stretching of the skin, more sparse, when we move fingers or limbs

free nerve endings

an axon that terminates in the skin and has no specialized cell associated with it

somatosensory system

a set of specialized receptors and neural mechanisms responsible for body sensations such as touch and pain

receptive field

the stimulus region and features that affect the activity of a cell in a sensory system

sensory adaptation

the progressive loss of receptor response as stimulation is maintained

phasic receptors

a receptor in which the frequency of action potentials drops rapidly as stimulation is maintained

tonic receptors

a receptor in which the frequency of action potentials declines slowly or not at all as stimulation is maintained (no adaption)

dorsal column system

a somatosensory system that delivers most of the touch stimuli to the brain via the dorsal columns of spinal white matter

dermatome

a strip of skin innervated by a particular spinal nerve

primary sensory cortex

the region of cortex that receives most of the information about that modality from the thalamus

nonprimary/ secondary sensory cortex

for a given sensory modality, the cortical regions receiving direct projections from primary sensory cortex for that modality

primary somatosensory cortex

primarily the postcentral gyrus of the parietal lobe, where the sensory inputs from the body surface are mapped

sensory homunculus

the size of each body part reflects the proportion of S1 devoted to that part

association areas

sensory areas that process a mixture of inputs from different modalities

polymodal neurons

a neuron upon which information from more that one sensory system converges

synesthesia

a condition in which stimuli in one modality evoke he involuntary experience of an additional sensation in another modality

pain

the discomfort normally associated with tissue damage

noiceptors

a receptor that responds to stimuli that produce tissue damage or pose the treat of damage

congenital insensitivity to pain (CIP)

mutation in gene SCN9A, requires constant monitoring

SCN9A

encodes a voltage-gated Na+ channel expressed in free nerve endings that serve as noiceptors

transient receptor potential type M3 (TRPM3)

found in some free nerve endings, that opens its channel in response to rising temperature

A delta (A8) fibers

a moderately large, myelinated, and therefore fast conducting axon that usually transmits pain information

C fibers

what TRPV1 receptors consist of, a small. unmyelinated axon that conducts pain information slowly and adapts slowly

anterolateral system/spinothalamic system

a somatosensory system that carries most of the pain information from the body to the brain

substance P

a peptide transmitter that is involved in pain transmission

cingulate cortex

where pain information is eventually integrated, a region of the medial cerebral cortex that lies dorsal to the corpus callosum

neuropathic pain

pain that persists long after the injury that started it has healed

gate control theory

spinal “gates” (modulation sites at which pain can be facilitated or blocked) control the signal that gets through to the brain

analgesia

absence or reduction of pain

endorphins

one of three kinds of endogenous opioids

naloxone

a potent antagonist of opioids that is often administered to people who have taken drug overdoses

placebo effect

relief of a symptom, such as pain, that results following a treatment that is known to be ineffective or inert

acupuncture

the insertion of needles at designated points on the skin to alleviate pain or neurological malfunction

decibels (dB)

a measure of sound intensity, perceived as loudness

hertz (Hz)

cycles per second, as of an auditory stimulus, perceived as pitch

transduced

to convert one form of energy to another

pure tone

a tone with a single frequency of vibration

amplitude

intensity, the force that sound exerts per unit area, which we experience as loudness

frequency

the number of cycles per second in a sound wave, measured in hertz

fundamental

the predominant frequency of an auditory tone

harmonics

a multiple of a particular frequency called the fundamental

timbre

the characteristic sound quality of a musical instrument, as determined by the relative intensities of its various harmonies

pinnae

the external part of the ear, funnels the soundwaves into the second part of the external ear

ear canal/ auditory canal

the tube leading from the pinna to the tympanic membrane

inner ear

the cochlea and vestibular apparatus

middle ear

the cavity between the tympanic membrane and the cochlea

tympanic membrane/eardrum

the partition between the external ear and the middle ear

ossicles

three small cones (incus, malleus, stapes) that transmit vibration across the middle ear, from the tympanic membrane to the oval window

oval window

the opening from the middle ear to the inner ear

cochlea

a snail-shaped structure in the inner ear canal that contains the primary receptor cells for hearing (scala vestibuli, scala media, scala tympani)

organ of Corti

a structure in the inner ear that lies on the basilar membrane of the cochlea and contains the hair cells and terminations of the auditory nerve

auditory sensory cells/hair cells

named for stereocilia that protrude from the top of the cell and transduce vibrational energy from the cochlea into neural activity

basilar membrane

a membrane in the cochlea that contains the principal structures involved in auditory transduction

tectorial membrane

membrane on the organ of Corti

stereocilia

a tiny bristle that protrudes from a hair cell in the auditory or vestibular system

inner hair cells (IHCs)

positioned closer to the central axis of the coiled cochlea (3500 of them)

outer hair hells (OHCs)

positioned farther from the central axis of the coiled cochlea (12000 of them)

vestibulocochlear nerve

cranial nerve VIII, which runs from the cochlea to the brainstem auditory nuclei

IHC afferents

action potentials that provide perception of sounds (95% of fibers leading to the brain)

IHC efferents

lead from the brain to the ICHs, allow the brain to control the responsiveness of IHCs

OHC afferents

convey information about the mechanical state of the basilar membrane, not perception of sounds themselves

OHC efferents

ability to change their length almost in simultaneously, modifies the stiffness of regions of the basilar membrane

cochlear nuclei

brainstem nuclei that receive input from auditory hair cells and send output to the superior olivary nuclei

superior olivary nuclei

brainstem nuclei that receive input from both right and left cochlear nuclei and provide the first binaural analysis of auditory information

inferior colliculi

paired grey matter structures of the dorsal midbrain that processes auditory information

medial geniculate nuclei

either of left and right nuclei in the thalamus that receive input from the inferior colliculi and send output to the auditory cortex

tonotopic organization

the organization of auditory neurons according to an orderly map of stimulus frequency, from low to high, auditory neurons take part in this

primary auditory cortex (A1)

the cortical region, located on the superior surface of the temporal lobe, that processes complex sounds transmitted from lower auditory pathways

taste buds

a cluster of 50-150 cells that detects tastes, found in papillae

papillae

a small bump that projects from the surface of the tongue, contains most of the taste receptor cells

microvilli

fine fibers, extend from the taste receptor cells into a tiny pore, where they come in contact with things that can be tasted

gustatory system

the sensory system that detects taste , information is carried in the facial nerve (VII), glossopharyngeal nerve (IX), vagus nerve (X)

retina

the receptive surface inside the eye that contains photoreceptors and other neurons

transduction

the conversion of one form of energy to another, such as from light to neuronal activity

cornea

the transparent outer layer of the eye, whose curvature is fixed

refraction

the bending of light rays by a change in the density of a medium, such as the cornea and lens

lens

a structure in the eye that helps focus an image on the retina

ciliary muscles

one of the muscles that control the shape of the lens inside the eye

accommodation

the process by which the ciliary muscles adjust the lens to bring nearby objects into focus

myopia/nearsightedness

the inability to focus the retinal image of objects that are far away

extraocular muscles

one of the muscles attached to the eyeball that controls its position and movements

photoreceptors

a neural cell in the retinal that responds to light

rods

a photoreceptor cell in the retinal that is most active at low levels of light

cones

any of several classes of photoreceptor cells in the retina that are responsible for color vision

bipolar cells

an interneuron in the retina that receives information from rods and cones and passes the information to the retinal ganglion cells

optic nerve/ cranial nerve II

the collection of ganglion cell axons that extends from the retina to the brain

ganglion cells

any of a class of cells in the retina whose axons from the optic nerve

horizontal cells

a specialized retinal cell that contacts both photoreceptors and bipolar cells

amacrine cells

a specialized retinal cell that contacts both bipolar cells and ganglion cells and is especially significant in inhibitory interactions within the retina

scotopic system

a system in the retina that operates at low levels of light and involves the rods

convergence

the phenomenon of neural connections in which many cells send signals to a single cell

photopic system

a system in the retina that operates at high levels of light, shows sensitivity to color, and involves the cones