Studied by 21 people
What are sensory receptors?
Cells that receive sensory information (a stimulus) from the environment
What do sensory receptors do?
Transduce different energy forms (pressure, temperature, chemical, light) into graded potentials that initiate action potentials
Afferent sensory input to CNS
What are the 5 classes of receptors?
Mechanoreceptors
Thermoreceptors
Photoreceptors
Chemoreceptors
Nociceptors ( Mary, Thought, Parry, Could, Notice)
What do mechanoreceptors do?
Respond to MECHANICAL stimuli, like touch or pressure
What do thermorecptors do?
Respond to cold/warmth (think *thermometer, temperature, cold/warm)
What do photoreceptors do?
Respond to light (think *good photos involves light)
Chemoreceptors
Respond to binding of particular CHEMICALS
Nociceptors
Respond to painful stimuli
What is receptor potential?
Graded potential in sensory receptor in response to environmental stimulus
What does transduction involve?
Opening of ion channels
If ______ at initial segment of axon reaches threshold, what happens?
depolarization; gated ion channels open -----> AP (electric signal) generated
What is adaptation?
Decrease in receptor sensitivity (responsiveness) during maintained stimulation
What does adaptation lead to?
Leads to decrease in AP frequency (rate) in afferent neuron despite continuous presence of a stimulus
Name the two types of adapting receptors:
Phasic or Fast-Adapting Receptors (think* PHAS=FAST)
Tonic or Slow-Adapting Receptors (think *TONE it down (slow))
What is the action of PHASIC receptors?
APs very quickly cease (come to an end) EXAMPLE: pressure when seated on a chair
Respond briefly before adapting to constant stimulus
What is the action of TONIC receptors?
persistent or slow decay of the firing of the APs. EXAMPLE: receptors in joint & muscle that maintain posture
What does somatic sensation include?
Touch, pressure, pain, temperature and senses of posture/movement
Name the two types of chemosenors:
Taste/Gustation
Smell/Olfaction
What does Gustation include?
Taste buds which are in the lingual papillae (the bumps on the tongue that come in various sizes and shapes)
What is a papilla?
small bump on the tongue
What are taste buds comprised of?
50-100 specialized epithelial cells called taste cells
Describe the connection between taste cells and taste categories
Each category of taste activates a specific taste cell
What happens during olfaction?
Odorants bind to membrane proteins, which are in the cilia. The cilia is attached to the dendrites of olfactory receptor neurons (bipolar neurons)
Axons of the receptor neurons synapse onto olfactory bulb of brain
Olfactory tract (grouping of axons) carries the afferent information to the brain
What interprets a specific odor?
The unique pattern of the binding of odorants and receptor proteins
Where do olfactory receptor cells synapse?
In the 2 olfactory bulbs
What is included within the VESTIBULAR System?
Structures are in inner ear
Sensation of: Head position, head movements (shaking head yes or no), and linear acceleration (xyz - straight line)
What do the otolith organs in the Vestibular Sensors include?
2 otolith organs, or maculae
Saccule and utricle
Mass of otoliths (calcium carbonate crystals) on top of a gelatinous substance
What do the otolith organs do?
Sense linear acceleration with respect to gravity (EX. jumping, bending down)
What do the semicircular canals in the Vestibular Sensors include?
3 semicircular canals (fluid-filled; endolymph)
Each canal has a crista (sensory organ in the ampulla)
Each crista has a gelatinous mass (cupula) on top which is pushed by endolymph movement
What do the canals do?
Sense angular acceleration of the head in 3 dimensions of space (X-Y-Z) to maintain balance
What does the Vestibular System do?
Detects changes in motion and position of the head
What causes a result in afferent activity?
The bending of hair cells in otolith organs and semicircular canals
What are OTOLITHS and what do they do?
They are tiny stones within the gelatinous substance. They cover the hair cells in the utricle and saccule which makes the gelatinous substance heavier.
What happens when the head is tilted forward?
Gravitational force causes the hair cells to bend, stimulating the sensory neurons
Describe the connection between the cupula, fluid and the hair cells
The position of the cupula in the semicircular canals makes the fluid movement to bend the cupula, stimulating the hair cells
In the auditory system, what does sound results from?
Vibration of gas, liquid, or solid molecules
What are sound waves?
Zones of atmospheric rarefaction (far apart) and compression
What do sound waves CAUSE when they reach the ear?
Movement of auditory structures, which is then transduced into action potentials
Frequency; what does it determine?
number of cycles per second of the sound wave
determine pitch (higher frequency, higher pitch)
Intensity; what does it determine?
amplitude of sound wave
determines loudness
What two things focus sound waves on the tympanic membrane (eardrum)?
Pinna and external auditory meatus (canal)
What does the focusing of sound waves cause?
Rockage of the malleus, incus, stapes. (Stapes is attached to the oval window of the cochlea)
Within the middle ear, where are the vibrations of the stapes transmitted?
The oval window which causes ripples in the cochlear fluid.
Name the order of Audition:
Tympanic membrane ----> ossicles ---> oval window ----> movement of fluid in cochlea -----> vibrations in basilar membrane (tonotopic)/ shearing between basilar membrane & tectorial membrane, bending hair cells in organ of Corti to depolarize them -----> NT release ----->APs in sensory neurons
What is comprised in Organ of Corti?
basilar membrane + hair cells + tectorial membrane
What is the Organ of Corti?
Where auditory transduction occurs in the cochlea
What happens within the organ of corti?
Ripples in the cochlear fluid causes the rasping of the tectorial membrane across the hair cells to bend them, causing depolarization. This causes NT to release and afferent signals to the CNS
What does low frequency cause?
Causes large vibrations in apical (at the top) cochlea
Low pitched sounds
(think *APEX like apical, low sounds at the top)
What does high frequency cause?
Causes large vibrations in basal (at the bottom) cochlea
High pitched sounds
(think * BOTTOM like basal, *high sounds at the bottom)
What does tonotopic mean?
Arranged by frequency
Where does light reflect off of?
The objects in the environment
Light has (blank)-like properties
Wave
What is wavelength and how is it measured?
The distance between 2 peaks, nanometers
What does wavelength correspond to?
Color
What is the visible spectrum?
Appx. 400-700 nm in humans
What do wavelengths do to stimuli?
Wavelengths constitute the stimuli transduced by the visual system.
Name the three layers (tunics) of the eye
Fibrous Tunic
Choroid
Retina
Describe the fibrous tunic
Outer connective tissue layer
Contains the Sclera and Cornea
Sclera
white
attachment of muscles that move eyeballs
Cornea
anterior region of sclera
clear
transmission of light
Describe the Choroid
beneath the sclera
contains the Pupil, Iris, Uvea, and Ciliary Muscle
Pupil
anterior opening for light entry into the eye (think *peephole)
Iris
pigmented muscle around pupil
used for pupillary dilation and constriction
dilation = let more light in, constriction = let less light in
Uvea
blood vessels
Ciliary Muscle
lens accommodation
changes lens shape to focus image on retina
Describe the Retina
posterior of eye
extension of brain
contains Photoreceptors
Photoreceptors
rods and cones for phototransduction
other neurons
Fovea
small region in retina w/ highest concentration of cones
greatest visual activity (ability to resolve fine details) (think *fovea = fine)
Optic Nerve
myelinated axons of ganglion cells in retina
afferent signals from eye to brain
Blind Spot
exit point for optic nerve -----> leaves retina
no photoreceptors = no transduction
Accommodation
changing of lens shape to focus light on retina
far vision: flattened lens
near vision: rounded lens (accommodation is AUTOMATIC, lens shape accommodates to light)
Where does visual transduction occur and what is it based on?
In the retina and is based on the images focused there by the cornea and lens
How are images on the retina perceived?
Upside down and are only a small fraction of the object's actual size
Describe the connection between ciliary muscles and lens
The contraction state of the ciliary muscle determines the amount of tension that the zonular fibers exert on the lens
What do contracted ciliary muscles determine?
Lower tension on zonular fibers and more rounded lens (think *opposite; contraction = lower tension)
What do relaxed ciliary muscles determine?
Higher tension on zonular fibers & more flattened lens (pulls ropes outward, causing lens to be flat and more tension on fibers
What does the contraction state of the ciliary muscle change?
Distant and close vision (distant = relaxed muscle) (close = contracted muscle)
What two items alter the location of image focus to correct for problems of eyeball length?
Corrective Glasses
Contact Lenses
What occurs before transduction by the rods and cones?
Light penetrates past the ganglion, bipolar and other cells
When are Photoreceptor Cells activated?
When light produces chemical change in photopigment molecules
Describe Rods
Most sensitive photoreceptors
Black and white vision
Vision in dim light
Describe Cones
Color vision (red, green, & blue sensitivity)
High resolution vision (fine detail, fovea) (think * color = cones)
What are the three types of cones?
S (blue) cone
M (green) cone
L (red) cone
What are the actions of the three cones?
Has photopigment that absorbs light in a specific range of wavelengths (in DIM light, ONLY RODS RESPOND)
Where are signals from the eyes processed?
In the visual cortex of the brain
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