Chapter 16 Flashcards
What is a sensory receptor?
A structure specialized to detect a stimulus
What is a sense organ?
A structure combining nervous and other tissues to enhance the response to a certain type of stimulus
What is transduction?
Conversion of one form of energy to another. Such as stimulus energy to nerve signals
What is receptor potential?
The initial effect of a stimulus on a sensory cell. Can lead to firing of action potentials, or release of neurotransmitter depending on the sensory cell type
What is a sensation?
A subjective awareness of a stimulus, resulting when sensory signals reach the brain
Why might some sensory signals not reach the brain?
Because they get filtered out in the brainstem to prevent overstimulation
What types of information do sensory receptors transmit?
Modality, location, intensity, and duration
What is modality of a stimulus?
The type of stimulus or the sensation it produces
What determines modality of a stimulus?
Where the sensory signals end in the brain
What is the location of a stimulus?
Sensory neurons have receptive fields in which any stimulation triggers the same neuron to send signals to the brain. More sensitive areas have smaller receptive fields
What is the intensity of a stimulus distinguished by?
Which neurons are firing, how many neurons are firing, and how fast they’re firing
What is duration of a stimulus encoded by?
Encoded by changes in firing frequency with passage of time
What is sensory adaptation?
If receptors are exposed to a stimulus for a long time, the neuron fires slower over time and you become less aware of the stimulus
What are phasic receptors?
Receptors which generate bursts of action potentials when stimulated, then quickly adapt and reduce signaling
What are tonic receptors?
Receptors which adapt to extended stimulation more slowly and steadily, making you more aware of the sensation than w/ phasic receptors
How are receptors classified?
Stimulus modality, stimulus origin, and distribution of receptors in the body
What are exteroceptors?
Sensory receptors that sense stimuli external to the body
What are interoceptors?
Sensory receptors that sense stimuli internal to the body
What are proprioceptors?
Sensory receptors that detect position and movement of the body and its parts
What are general senses?
Distributed throughout the body
What are special senses?
Distributed solely in the head, innervated by cranial nerves, and employing complex sense organs
What do thermoreceptors detect?
Heat and cold
What do photoreceptors detect?
Light
What do nociceptors detect?
Pain
What do chemoreceptors detect?
Chemical changes
What do mechanoreceptors detect?
Physical movement
What are the unencapsulated nerve endings?
Free nerve endings, tactile discs, and hair receptors
What are the encapsulated nerve endings?
Tactile corpuscles, end bulbs, bulbous corpuscles, lamellar (Pacinian) corpuscles, muscle spindles, and tendon organs
Modality of free nerve endings?
Thermoreceptors and nociceptors
Modality of tactile discs?
Tonic, mechanoreceptors
Modality of hair receptors?
Phasic, mechanoreceptors
Modality of tactile corpuscles?
Light touch and thermoreceptors
Modality of end bulbs?
Light touch and thermoreceptors
Modality of bulbous corpuscles?
Tonic, mechanoreceptors
Modality of lamellar (Pacinian) corpuscles?
Phasic, for vibration
Modality of muscle spindles?
Mechanoreceptors
Modality of tendon organs?
Mechanoreceptors
What is sensory projection?
Transmission of info from a receptor (or receptive field) to a specific locality in the cerebral cortex for identification of origin
What are projection pathways?
The pathways followed by sensory signals to their destinations in the CNS. From first, second, and third order neurons
Where do first-order neurons lead?
To brainstem
Where do second-order neurons lead?
From brainstem to thalamus
Where do third-order neurons lead?
From thalamus to cerebrum
How do proprioception signals differ from others?
They don’t require third-order neurons; second-order neurons go all the way from brainstem to cerebrum
What is fast/first pain?
A sharp, stabbing pain at time of injury
What is slow/second pain?
Longer-lasting, dull and diffused pain
Where is somatic pain?
In the skin, muscles, or joints
Where is visceral pain?
In the viscera, due to stretch or chemical irritants
What is bradykinin?
The most potent pain chemical in the body, which makes us aware of injuries and activates a cascade of reactions that promote healing
What is referred pain?
When pain in a viscera feels as though it comes from a different region of the body due to convergence of neural pathways in the CNS
Structures involved in pain signals reaching from head to brain?
Trigeminal nerve, facial nerve, glossopharyngeal nerve, vagus nerve
Structures involved in pain signals reaching from neck to brain?
Spinothalamic tract, spinoreticular tract, and gracile fasciculus
What are analgesic mechanisms?
Pain-relieving mechanisms in the CNS
What are endogenous opioids?
Opioids produces by the body and secreted by the CNS, pituitary gland, and digestive tract. Relieves pain
What are THE endogenous opioids?
Enkephalins, endorphins, and dynorphins
Route of normal pain transmission?
Nociceptor stimulates second-order nerve fiber, releasing substance P -> second-order nerve fiber transmits signals to thalamus -> thalamus relays signals through third-order neuron to cerebral cortex
Route of pain modulation?
Hypothalamus + cerebral cortex signals feed into gray matter of midbrain for autonomic and conscious influences on pain perception ->midbrain relays signals to nuclei in medulla oblongata -> medulla issues serotonin-secreting analgesic fibers to spinal cord’s posterior horns -> analgesic fibers of posterior horns secrete enkephalins, inhibiting second-order neuron -> some fibers from medulla block release of substance P
What is the physical method of pain modulation?
Massaging the affected area, which works because pain-inhibiting interneurons in posterior horn receive input from the skin’s mechanoreceptors, so when you rub, you stimulate those m.ceptors which stimulate spiral interneurons to secrete enkephalins. Inhibiting second-order neurons
What papillae do not have taste buds?
Filiform and foliate (after age 3)
What papillae have taste buds?
Fungiform and vallate
What taste buds does the facial nerve get input from?
Anterior 2/3 of tongue
What taste buds does the glossopharyngeal nerve get input from?
Posterior 1/3 of tongue
What taste buds does the vagus nerve get input from?
Palate, pharynx, and epiglottis
What do proprioceptors do?
Limb position
What are taste buds found on?
Papillae
What kind of endings are temperature receptors?
Free nerve endings
Where are the olfactory receptors?
Roof of nasal cavity
Lining of inner eyelids?
Conjunctiva
Function of the iris?
Regulate pupil size
What pigment is in rods?
Rhodopsin
What pigment is in cones?
Photopsin
What is accomodation?
Changing shape of the lens for far and near vision
What is macular degeneration?
Blindness caused by abnormal blood vessel growth in retina
What is the tectorial membrane?
Where hair cells of the organ of Corti have their stereocilia embedded
What is referred pain?
Feeling of pain on the body surface that has its origin in an internal organ
What are semicircular canals for?
Rotational equilibrium
What are the sensory cells of gustation?
Taste buds
What are the chemical stimulants of gustation?
Tastants
Where are tastants?
All over the tongue, as well as on the cheeks, soft palate pharynx, and epiglottis
What are the bumps on the tongue?
Lingual papillae
Characteristics of filiform papillae?
Innervated, lack taste buds. Allow perception of food texture
Characteristics of foliate papillae?
Weak in humans. Adjacent to molar and premolar teeth. Have taste buds
Characteristics of fungiform papillae?
3 taste buds each. Widely distributed, respond to food texture
Characteristics of vallate papillae?
Arranged in a V at the back of the tongue. Only 7-12, but each has a TONNN of taste buds
What are taste hairs?
Apical microvilli which are receptor surfaces for tastants and project into taste pores
What kind of cell are taste cells?
Epithelial, they synapse with sensory nerve fibers
What are basal cells?
Stem cells that multiply and replace dead taste cells since they only last 7-10 days. They also may have a role in processing sensory info
What are supporting gustatory cells?
Cells that resemble taste cells but have no synaptic vesicles or sensory role
How does taste work?
Food dissolves in the saliva and floods the taste pore
5 main taste sensations?
Salty, sour, sweet, bitter, umami
Why is salty an important taste?
Bc you need electrolytes
Why is sour an important taste?
To avoid spoiled food and overloading body’s acid-base balance
Why is sweet an important taste?
It’s more important for plants cuz they need glucose to grow
Why is bitter an important taste?
To avoid spoiled foods and because a lot of poisonous foods are bitter so you spit it out
Why is umami an important taste?
Motivates protein intake
What are some other tastes that are up for debate?
Oleogustus (fat) and water
What 3 nerves collect sensory input from the tongue?
Facial, glossopharyngeal, and vagus nerves
Taste pathway?
Taste buds -> nerve (facial or glossopharyngeal or vagus) -> medulla oblongata -> hypothalamus and amygdala OR thalamus and gustatory cortex
What is olfaction?
The sense of smell caused by odorants
Where is the olfactory mucosa?
Roof of the nasal cavity
What makes up the olfactory mucosa?
Olfactory cells + epithelial supporting cells and basal stem cells
What kind of cells are olfactory cells?
Neurons
What are olfactory hairs?
Cilia embedded in a layer of mucus which have binding sites for odor molecules
Anatomy of olfactory hair?
Embedded in layer of mucus, tapers at one end to an axon which collects into fascicles, exiting the nasal cavity via cribriform foramine in ethmoid bone
How many receptor types in each olfactory cell?
1, therefore it only binds 1 odorant
Where do olfactory fibers lead?
To olfactory bulbs where they synapse w/ dendrites called mitral cells and tufted cells
What are olfactory tracts?
Bundles of axons from the mitral and tufted cells which end in the primary olfactory cortex, skipping the thalamus
What are granule cells?
Neurons which inhibit mitral and tufted cells
Olfactory nerves go where?
To the olfactory bulb (through the ethmoid bone) and then to the olfactory tract
How is the cochlear nerve activated?
A vibration in the air moves into the auditory canal, causes tympanic membrane to vibrate, causes ossicles to vibrate, causes vibrations in cochlea, activates cochlear nerve
What is the pitch of a sound?
Frequency of sound waves, or how many times the tympanic membrane vibrates per second. Measured in hertz (Hz)
Lower vibrations means what for pitch?
Lower pitch
What is the loudness of a sound?
The amplitude of a vibration. Measured in decibels (dB). Over 90 is bad for your hearing
What happens in the outer and middle ear?
They transmit sound to the inner ear
What happens in the inner ear?
Vibrations are converted to nerve signals
What is the auricle?
Part of the outer ear, it’s the rim, helix, base, and ear lobe. What you picture when you hear ear basically
What is the external acoustic meatus?
Part of the outer ear. Collects soundwaves and brings them to the tympanic membrane
What makes up the middle ear?
Auditory tube (NOT THE MEATUS. remember.), and the auditory ossicles (malleus, incus, stapes)
What is the malleus often called?
The hammer
What is the incus often called?
The anvil
What is the stapes often called?
The stirrup
What does the stapes do?
It taps the oval window, causing fluid to vibrate and activate mechanoreceptors, whhich activate the cochlear nerve
Path of stapes’s effects?
Oval window -> scala vestibuli -> scala media -> scala tympani -> round window
What can endolymph be compared to, and why?
Intracellular fluid due to high potassium levels
What can perilymph be compared to, and why?
Cerebrospinal fluid due to low potassium levels
What happens to the stereocilia of the inner ear when mechanoreceptors are activated?
They shift over, opening potassium channels, causing depolarization
What is sensorineural deafness?
Death or damage to cochlear hair cells, so nerve cannot be activated
What is conductive deafness?
When sound can’t pass through the outer and middle ear into the inner ear due to blockage
Auditory pathway?
Auricle -> external auditory meatus -> tympanic membrane -> malleus -> incus -> stapes -> oval window -> auditory hair cells in the organ of corti, within the cochlear -> cochlear nerve -> medulla -> inferior colliculus -> thalamus -> primary auditory cortex in the temporal lobe
What is otitis media?
Middle ear infection due to throat illness travelling up the auditory tube
What is otosclerosis?
Fusion of auditory ossicles due to inflammation (from recurring ear infections) that prevents their free vibration
What is static equilibrium?
Perception of orientation of the head while the body is stationary
What is dynamic equilibrium?
Perception of motion or acceleration
What is linear acceleration?
A change in velocity in a straight vertical or horizontal line
What is an angular acceleration?
A change in the rate of rotation
What does the vestibular apparatus do?
Part of the inner ear, it maintains static and dynamic equilibrium
What do semicircular ducts do?
They contain fluid which spins with movement and activates mechanoreceptors. Dynamic equilbrium
What does the vestibule do?
Controls static equilibrium and linear acceleration (of dynamic equilbrium)
What do otoliths do?
When you move your ehad, they push gel down which moves stereocilia of mechaboreceptors and activates potassium channels
What is tinnitus?
Ringing of ears due to cochlear nerve degeneration
What is meniere’s syndrome?
A disorder of the cochlear and semicircular canals which causes vertigo, nausea, and vomiting
What does the auditory/eustachian tube do?
Aerate and drain middle ear
What are the fluid-filled chambers of the cochlea?
Scala vestibuli, scala media, and scala tympani
Accessory organs of the eye?
Eyebrows, eyelids, eyelashes, conjunctiva, extrinsic muscles, lacrimal apparatus
What is the conjunctiva?
The inner lining of the eyelids that covers the anterior surface of the eyeball. Very innervated and vascular
What do extrinsic muscles do?
Pull eyeball to look at objects and maintain the eyeball’s shape
What is strabismus?
Cross-eyedness due to eye rotating medially or laterally
Neural components of the eye?
Optic nerve and retina
What is the macula lutea and fovea centralis?
Part of the retina, they are the visual axis and the center of the macula respectively
What is responsible for our finely detailed sight?
Fovea centralis of the macula
What are rods?
Scotopic vision and peripheral vision but most importantly our light-dark vision
What are cones?
Color and photopic vision but most importantly our color vision
What length cones make red?
Long wave
What length cones make green?
Medium wave
What length cones make blue?
Short wave
Why does colorblindness happen?
Congenital lack of one or more cones
How do we see? What’s the basic pathway
Photoreceptor -> bipolar cell -> ganglion cell -> optic nerve
What happens with our eyes in the dark?
Photoreceptors generate their own action potentials and release a neurotransmitter inhibiting the bipolar nerve, so it can’t activate the optic nerve
What happens with our eyes in the light?
Photoreceptors are activated, inhibitory neurotransmitter is not released, meaning bipolar cell can release its neurotransmitter, activating ganglion cell, activating optic nerve
What is rhodopsin?
Visual pigment of the rods
What is photopsin?
Visual pigment of the cones. Different amino acid sequence than rhodopsin but otherwise really similar
Visual pathway?
Light goes into cornea -> aqueous humor -> anterior segment -> lens -> vitreous humor -> cornea -> lens -> retina -> bipolar cells -> ganglion cells -> optic nerve -> optic chiasm -> thalamus -> visual cortex of occipital lobe
Whtt does the optic chiasm do?
It takes half the nerves from each eye and mixes them. So pre-chiasm its 100% left and 100% right but post-chiasm its 50/50 and 50/50 so you don’t lose a whole eye’s vision if it gets damaged, you lose half of each
What is near response?
Adjustment to close-range vision. Convergence of eyes, constriction of pupil, and accomodation of lens
What are cataracts?
Lens fibers darken with age, fluid-filled bubbles and clefts full of debris appear between the fibers, clouding the lens
What is glaucoma?
Elevated pressure within eye due to obstruction of scleral sinus or improper drainage of aqueous humor. Causes death of retinal cells bc of lack of oxygen
Layers of eyeball from outermost to innermost?
Sclera, choroid, retina
What are the components of the fibrous tunic?
Cornea and sclera
