sense organs Flashcards
receptors
structures that detect stimuli
classification of receptors: modality
types of stimuli detected:
- thermoreceptors: temperature
- photoreceptors: light
- chemoreceptors: chemicals
- nociceptors: pain
- mechanoreceptors: pressure or stretch
classification of receptors: distribution of receptors in body
- general senses are widly distributed body senses
- special sense involve cranial nerves (complex)
classification of receptors: stimulus origin
- exteroceptors: from outside body
- interoceptors: from organs within the body
- proprioceptors: regarding prosition of the body
unencapsulated nerve endings
dendrites lacking connective wrapping:
free nerve endings
unencapsulated nerve endings:
- warm receptors
- cold receptors
- nocieptors
tactile (merkle) discs
unencapsulated nerve endings:
- light touch and pressure
hair receptors (pertrichial endings)
unencapsulated nerve endings:
- movement of hairs
encapsulated nerve endings
dendrites wrapped by glia or connective tissue
tactile (Meissner) corpusles
- encapsulated nerve ending
- oval mass in dermal papillae
- sense light touch and texture perception
end bulbs (Krause)
- encapsulated nerve ending
- similar to tactile corpuscles but located in mucous membranes
bulbous (Ruffini) corpuscles
- encapsulated nerve ending
- flat
- sense pressure, skin stretch, and join movement
lamellar (pacinin) corpuscles
- encapsulated nerve ending
- onion like
- sense deep pressure, stretch, tickle, and vibrations
muscle spindles
- encapsulated nerve ending
- fusiform
- sense skeletal muscle stretch
tendon organs
- encapsulated nerve ending
- leaflike
- sense tendon stretch caused by muscle activity
receptive field
area supplied by a single neuron
receptive field sizes
- neurons in different regions of body have recieptive fields of different size
- neurons with a small receptive field size (ex: skin of fingers) allow for fine 2-point discrimination
somatosensory projection pathways
- sensory signals are conveyed through the nervous system by pathways of neurons
- first-, second-, and third-order neurons carry the signals
first-order fibers
- fibers for touch, pressurem and propriception are large, myelinated, and fast
- fibers for heat and cold are small, unmyleinated and slow
second-order fibers
terminate in the contralateral thalamus
third-order fibers
project from thalamus to cerebrum
pain
- discomfort that makes us aware of injurious situations
- different nociceptors responsible for slow vs fast pain
- third-order neruons end in cerebral cortex
pain from the head
conducted by cranial nerves to the brain
pain from below head
travels via spinothalamic and spinoreticular tracts
referred pain
innacturate pain reception
pain from the viscera mistakenly thought to come from more superficial sites
gating of pain
innacturate pain reception
- pain signals from periphery never reach brain
- pain-relieving neurotransmitters can act on first-order neurons
taste buds locations
- tongue has the most
- some in soft palate, phsrynx, epiglottis, and cheeks
taste (gustation)
- taste buds
- lingual papillae
lingual papillae
surface projections on tongue
types of lingual papillae
- filiform
- folate
- fungiform
- vallate
filiform
- numerous
- tiny spikes
- no buds
folate
- ridges on tongue sides
- buds in children
fungiform
- mushroom shaped bumps
- have buds
vallate
- large bumps in a row at the back of the tongue
- have buds
taste buds contain
taste cells and taste pores
taste cells
- banana shaped
- taste hairs: receptor for taste modulate
- synapse with sensory nerve
taste pore
hole on epithelial surface of tongue
gustatory projection pathway to the cerebral cortex
second-order neruons in solitary nucleus of medulla
2 parallel pathways:
- hypothalamus mediates autonomic reflexes (ex: gagging)
- thalamus sends signals to cortex for conscious percetion of taste
nerves involved in gustatory projection pathway to the cerebral cortex
- facial (CN VII): anterior tongue
- glossopharyngeal (CN IX): posterior tongue
- vagus: (CN X): palaye, pharynx, epiglottis
smell (olfaction) contains
- olfactory mucosa
- olfactory neurons
- olfactory bulbs
olfactory mucosa
- roof of nasal canal
- contains 10-20 million olfcatory neruons
olfactory neruons
- have olfactory hairs (cilia) with binding site for ordor molecules
- olfactory cell’s axons make olfactory nerve (CN I)
olfactory bulb
swollen tips of olfactory tracts at base of frontal lobes
olfactory projection pathways
- signals do not pass through thalamus before stimulating primary olfactory cortex at medial side of temporal lobe
- secondary areas include insula, orbitofrontal cortex, hippocampus, amygdala, and hypothalamus
- evokes strong memories, emotions, and visceral reactions
outer ear
ear anatomy
- auricle (pinna)
- auditory canal with hairs, cerumen
middle ear
ear anatomy
- tympanic membrane (eardrum)
- tympanic cavity of temporal bone
- auditory (eustachian) tube
- auditory ossicles: malleus, incus, stapes
- oval windo
- muscles: stapedius, tensor tympani
inner ear anatomy
ear anatomy
- bony labyrinth: maze in temporal bone
- membranous labyrinth: tube within maze
- endolymph: fluid in membranous labrynth
- perilymph: fluid between membranous labyrinth and bone
- vestibule: utricle and saccule
- 3 semicircular canals
- cochlea: snal snaped
cochlear duct
inner ear anatomy
organ of hearing
- spirals around modiolus – an axis of spongy bone
- contains spiral organ with four rows of hair cells: one row of inner hair cells, three rows of outer hair cells
- stereocilia of hair cells project into tectorial membrane
- hair cells synapse with sensory neurons that form spiral ganglion and cochlear division of CN VIII
- contains endolymph
scala vestibuli
inner ear anatomy
- chamber above vestibular membrane
- begins near oval window
- contains perilymph
scala tympani
inner ear anatomy
- chamber below basilar membrane
- ends at round window that is covered by secondary tymapnic membrane
- contains perilymph
auditory function
muscles for eye movements
- Upward: superior rectus
- Downward: inferior rectus
- Lateral: lateral rectus
- Medial: medial rectus
rods
- night vision
- monochromatic- rhodopsin in discs in outer membrane
cone
- day vision
- trichromatic visions (Blue, green, yellow-orange)- photospins in parallel infolding of the membrane
differences between static and dynamic equilibrium and between linear and angular acceleration
- static: still
- dynamic equilibrium: moving
- linear acceleration: moving forwards or backwards
- angular acceleration: moving up and down or spinning
