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special senses
vision hearing smell taste equilibrium TERM 2
Sensory stimuli divided into...
DEFINITION 2 special senses (vision, hearing, taste, smell, equilibrium) somatic senses (touch, temperature, pain, itch, proprioception) TERM 3
proprioception
DEFINITION 3 awareness of body movement and position in space, mediated by muscle and joint sensory receptors called proprioceptors TERM 4
types of somatosensory receptors
DEFINITION 4 free nerve endings encapsulated nerve endings specialized receptor cells TERM 5
Free nerve endings as somatosensory
receptors
DEFINITION 5 simple receptors of naked nerve endings may have myelinated or unmyelinated axons
Encapsulated nerve endings as
somatosensory receptors
complex neuronal receptors nerve endings enclosed in connective tissue capsules TERM 7
specialized receptor cells as somatosensory
receptors
DEFINITION 7 most special senses: receptor cells release NT to sensory neurons to initiate action potential *Exception: smell receptors are neurons, other special senses use the specialized receptors TERM 8
4 types of sensory
receptors
DEFINITION 8 chemoreceptors mechanoreceptors thermoreceptors photoreceptors based on the stimulus to which they are most sensitive TERM 9
chemoreceptors
DEFINITION 9 chemical ligand binds to receptor (oxygen, pH, organic molecules) taste (gustation) and smell (olfaction) use chemoreceptors TERM 10
mechanoreceptors
DEFINITION 10 Respond topressure (baroreceptors), cell stretch (osmoreceptors), vibration, acceleration, sound hearing uses mechanoreceptors
Receptive field
property of an individual somatic sensory or visual neuron the specific physical area in which a sensory neuron can sense a stimulus the size of secondary receptive fields determines how sensitive a given area is to a stimulus e.g. 2-point discrimination test: more sensitive areas where can discriminate touch at points closer together, corresponding to smaller receptive fields TERM 17
Convergence of sensory
neurons
DEFINITION 17 multiple sensory neurons synapsing on one secondary neuron, creating a single large receptive field convergence of primary sensory neurons allows simultaneous subthreshold stimuli to sum at the secondary sensory neuron and initiate an AP more convergence -> larger receptive field -> less sensitive TERM 18
CNS integration of sensory
information
DEFINITION 18 Sensory info from spinal cord -> thalamus -> sensory areas of cerebral cortex **exception: olfactory info not thru thalamus, goes to olfactory bulb some sensory info -> directly to brainstem (via cranial nerves) visceral reflexes: integrated in brainstem/spinal cord - don't usually reach perception CNS able to modify level of awareness of sensory input - perceptual threshold TERM 19
perceptual threshold
DEFINITION 19 level of stimulus intensity necessary for us to be aware of a particular sensation TERM 20
modality of a stimulus
DEFINITION 20 nature of a stimulus indicated by which sensory neurons are activated and where neurons are terminated in the brain labeled line coding
4 properties of a stimulus CNS must
distinguish
nature (modality) location intensity duration TERM 22
Special senses - neuron termination in the
brain
DEFINITION 22 olfaction - olfactory cortex equilibrium - cerebellum vision - visual cortex in occipital lobe sound - auditory cortex in temporal lobe TERM 23
labeled line
coding
DEFINITION 23 1:1 association of a sensory receptor with a specific sensation ex: cold receptor AP always perceived as a cold signal, even if falsely depolarized or alternatively stimulated TERM 24
location of a stimulus
DEFINITION 24 determined according to which receptive fields activated auditory: depends on timing of receptor activation in each ear then calculated by brain lateral inhibition enhances contrast between center of receptive field and edges of the field population coding to calculate location and timing TERM 25
lateral inhibition
DEFINITION 25 process by which sensory neurons close to the stimulus are inhibited to intensify perception of the stimulus enhances contrast between the center of the receptive field and edges of the receptive field
Four somatosensory modalities
touch proprioception (self awareness in space) temperature nociception (pain and itch) TERM 32
Nociception
DEFINITION 32 pain and itch TERM 33
Projection of somatic perception to
somatosensory cortex/cerebellum
DEFINITION 33 secondary sensory neurons cross midline in spinal cord or medulla - brain processes information from opposite side of body Somatosensory pathways synapse in thalamus (other than olfactory - synapse in olfactory bulb) ascending tracts then terminate in the somatosensory cortex TERM 34
Touch receptors respond to many different
stimuli
DEFINITION 34 touch receptors = most common receptors in body free nerve endings - noxious stimuli Parcinian corpuscles - vibration Meissener's corpuscles - flutter/stroking Runffini corpuscles - stretch Merkel receptors - pressure/texture TERM 35
Temperature receptors
DEFINITION 35 terminate in subcutaneous layers cold receptors: sense lower than body temperature ( C) warm receptors: sense above body temperature to about 45C (above - pain receptors activated) initial response - changing temp; sustained response - ambient temp
Nociceptors
free nerve endings respond to chemical, mechanical, or thermal stimuli perceived as pain and itch modulated by local chemicals like substance P TERM 37
Substance P
DEFINITION 37 peptide secreted by primary sensory neurons mediates inflammatory response - inflammatory pain (increased pain sensitivity at tissue damage site) TERM 38
Nociceptor pathways
DEFINITION 38 reflexive protective responses integrated in spinal cord: some responses to irritants , such as the withdrawal reflex , are protective spinal reflexes (don't require integration in the brain) ascending pathway to cerebral cortex becomes conscious sensation as pain or itch TERM 39
itch
DEFINITION 39 mediated by nociceptors caused by histamine activated C fibers TERM 40
Fast pain
DEFINITION 40 mediated by nociceptors sharp, localized transmitted rapidly by small, myelinated fibers
olfactory receptor cells
in olfactory epithelium primary sensory neurons that synapse with secondary sensory neurons in olfactory bulb olfactory receptor cell axons - Cranial nerve I (olfactory nerve) live about 2 months, replaced by new cells whose axons must find way to olfactory bulb TERM 47
Olfactory pathway
DEFINITION 47 Olfactory receptor cells Cranial nerve I Olfactory bulb Olfactory tract Olfactory cortex Cerebral cortex, Limbic system secondary sensory neurons in olfactory bulb process info 2 and higher-order neurons project from olfactory bulb to olfactory cortex (bypasses thalamus) parts lead to amygdala and hippocampus, parts of limbic system involved in emotion/memory TERM 48
Olfactory transduction
DEFINITION 48 odorant receptors: GPCRs that activate cAMP production -
open ion channels -> depolarize -> AP brain uses info from 100s of olfactory receptor cells in different combos -> perception of many different cells (population coding) TERM 49
5 basic taste sensations
DEFINITION 49 sweet sour - triggered by H+ salty - for Na+ bitter - warning of potentially toxic components umami TERM 50
Umami
DEFINITION 50 savory taste associated with the AA glutamate and some nucleotides enhances flavor of foods
taste buds
located on dorsal surface of tongue composed of taste cells and support cells joined near apical surface with tight junctions taste ligands create calcium signal that releases serotonin or ATP TERM 52
Taste transduction
DEFINITION 52
- taste cells: non-neuronal cells that interact with taste ligands salty and sour - membrane channels sweet/umami/bitter - GPCRs
- interaction -> intracellular Ca2+ signal -> activates 1 sensory neuron- population coding - senstation perceived depends on cells most strongly responding TERM 53
Type III presynaptic cells
DEFINITION 53 taste cells for salty and sour taste signal created by ligand binding receptor membrane channel release serotonin by exocytosis TERM 54
Type II taste receptor
cells
DEFINITION 54 taste cells for sweet, bitter, and umami GPCR activates G protein gustducin -> calcium signal -> ATP released through gap junction-like channels TERM 55
senses of the ear
DEFINITION 55 vestibular complex of inner ear = 1 sensor for equilibrium remainder of ear used for hearing
inner ear
vestibular apparatus with its semicircular canals - sensory transducer for equilibrium cochlea - membranous coiled tube within bony cavity containing sensory receptors for hearing; oval window and round window branches of cranial nerve VIII - vestibulocochlear nerve - lead from inner ear to brain TERM 62
oval window
DEFINITION 62 membranous disk in cochlea stapes is attached TERM 63
round window
DEFINITION 63 membranous disk in cochlea separates the liquid-filled cochlea from air-filled middle ear TERM 64
hearing
DEFINITION 64 perception of energy carried by sound waves brain's interpretation of the frequency, amplitude, and duration of sound waves that reach our ears TERM 65
Pitch
DEFINITION 65 brain translates frequency (# of sound waves/sec, Hz) into pitch frequency of sound waves determines displacement of basilar membrane, location of activated hair cells -> codes pitch low frequency -> displace more flexible distal end -> low pitch high frequency -> max displacement near oval window -> high pitch
loudness
our interpretation of sound intensity function of wave height - amplitude (dB) encoded by frequency of AP in sensory neuron (loser -> more rapid APs) influenced by sensitivity of individual's ear TERM 67
hair cells
DEFINITION 67 non-neuronal sensory receptors for auditory system (hearing) and vestibular system (equilibrium) in ears cilia known as stereo cilia on apical surface of hair cells TERM 68
sound transmission in ear
DEFINITION 68 waves strike tympanic membrane -> become vibrations -> energy transferred to 3 bones of middle ear (vibrate, amplification) Stapes vibrates oval window -> fluid waves in cochlea fluid waves push on membrane of cochlear duct, bending hair cells -> open ion channels -> electrical signal electrical signal -> NT release NT creates AP in sensory neurons -> cochlear nerve to brain energy from waves transfers across cochlear duct -> tympanic membrane, dissipated back into middle earat round window TERM 69
parallel fluid filled channels of cochlea
DEFINITION 69 vestibular duct cochlear duct tympanic duct TERM 70
vestibular duct
DEFINITION 70 channel in cochlea scala vestibule, stairway entrance filled with perilymph
hair cell signal transduction
at rest: ~10% ion channels open - tonic signal sent by neuron excitation: hair cells bend one direction -> depolarization -> increase AP frequency in associated sensory neuron inhibition: hair cel bends in opposite direction, closing ion channels -> hyper polarize -> decrease AP wave pattern converted to pattern of APs going to CNS TERM 77
localization of sound
DEFINITION 77 higher function, requires sensory input from both ears - computation by brain based on time between signals TERM 78
auditory pathways
DEFINITION 78 cochlear nerve -> medulla, pons, midbrain, and thalamus before terminating in auditory cortex information from both ears goes to both sides of the brain TERM 79
equilibrium
DEFINITION 79 state of balance mediated through hair cells in vestibular apparatus and semicircular canals of inner ear non-neuronal receptors, respond to changes in rotational, vertical, and horizontal acceleration and positioning gravity and acceleration provide force that moves cilia TERM 80
Vestibular apparatus
DEFINITION 80 membranous labyrinth series of interconnected endolymph-filled chambers provides info about movement and position in space 2 saclike otolith organs (saccule and utricle) and three semicircular canals
otolith organs
part of vestibular apparatus for linear acceleration and head position sensory structures: maculae , consistof hair cells embedded in gelatinous mass known as otolith membrane as well as calcium carbonate and protein particles called otoliths gravity/acceleration cause otoliths to slide, pulling otolith membrane with them bending the hair cell cilia and setting off signal utricle: sense forward acceleration/deceleration and head tilt saccule: sensitive to vertical forces TERM 82
semicircular canals of vestibular
apparatus
DEFINITION 82 three semicircular canals that connect to the utricle at their bases end of each has enlarged chamber - ampulla , which contains a sensory structure known as a crista Crista consists of hair cells and gelatinous mass, cupula, in which the hair cells are embedded as head turns: drag of endolymph bends cupula opposite direction from which the head is turning sense rotational acceleration in various directions TERM 83
Meniere's disease
DEFINITION 83 excessive accumulation of endolymph (in cochlear duct) causes dizziness and nausea TERM 84
Equilibrium pathway
DEFINITION 84 hair cells in vestibular apparatus receive signal sensory neurons either synapse in vestibular nuclei of medulla or run without synapsing to the cerebellum cerebellum is primary site for equilibrium processing collateral pathways run from medulla to cerebellum or upward through reticular formation and thalamus descending pathways from vestibular nuclei go to certain motor neurons involved in eye movement - help keep eyes locked on object as head turns TERM 85
primary site for equilibrium processing
DEFINITION 85 cerebellum
zonules
inelastic ligaments in the eyes that suspend the lens attach lens to ciliary muscle TERM 92
aqueous humor
DEFINITION 92 low protein plasma-like fluid secreted by the ciliary epithelium supporting the lens fills anterior chamber in front of lens TERM 93
vitreous body (vitreous
humor)
DEFINITION 93 clear, gelatinous matrix fills vitreous chamber behind the lens helps maintain shape of eyeball TERM 94
sclera
DEFINITION 94 outer wall of eyeball (white of eye) made of connective tissue TERM 95
cornea
DEFINITION 95 transparent disc of tissue continuous with the sclera light enters anterior surface of eye through
lens function
bends light to focus it on the retina TERM 97
retina
DEFINITION 97 light sensitive lining of eye layer that contains photoreceptors TERM 98
optic disk
DEFINITION 98 blind spot region where optic nerve and blood vessels (central retinal artery and vein) leave the eye TERM 99
fovea
DEFINITION 99 region of sharpest vision lateral to optic disk small dark spot TERM 100
macula
DEFINITION 100 narrow ring of tissue surrounding fovea center of the visual field
