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BIOPSY EXAM 2
Terms in this set (117)
Vision is in your brain
· Each of our senses has specialized receptors that are sensitive to a particular kind of energy
· Receptors for vision are sensitive to ________
· Receptors _______ energy into electrochemical patterns so that the brain can perceive sights, sounds, smells, etc.
Law of ____________
· States that activity by a particular nerve always conveys the same type of information to the brain
o Example: impulses in one neuron indicate light; impulses in another neuron indicate sound
o If you stimulate a particular part of the brain responsible for vision using electrical stimulation, you can perceive something that is not there
· Which neurons ________, the ________ of response, and the _________ of response influence what we perceive
· Rub your eyes ---
o You have applied mechanical pressure to visual receptors, so it is perceived as light.
specific nerve energy
The eye and its connections to the brain
· The surface of the eye is opaque except for the _________
· Light enters the eye through an opening in the center of the iris called the __________,
· Light is focused by the _______ and the ___________ onto the rear surface of the eye known as the __________
o The retina is lined with ____________
Light from the left side of the world strikes the __________ side of the retina and vice versa
Light traveling pathway
· Light passes through a series of neural cells (____________, ____________, _________, and __________) then before it hits the receptors.
· ___________ receptors sense the light
· Receptor cells send messages to neurons called _________ cells
· Bipolar cells send messages to _________ cells that are even closer to the center of the eye
· The axons of ganglion cells join one another to form the _________ that travels to the brain
· Amacrine cells and horizontal cells are additional cells that receive information from bipolar cells and send it to other bipolar, ganglion, or amacrine cells
o They control the ability of the ganglion cells to respond to shapes, movements, or other specific aspects of visual stimuli
ganglion cells, amacrine cells, bipolar cells, and horizontal cells
· The optic nerve consists of the axons of _________ that band together and exit through the back of the eye and travel to the brain
· The point at which the optic nerve leaves the back of the eye is called the ___________ because it contains no receptors
o 120 million per retina
o most abundant in the _________ of the eye and respond to ___________ light
o Contain photopigment called __________ which is not useful in full sun
o When you walk into a dark room and it takes you a second to see, that period of _____________ is rhodopsin re-synthesizing in your rods
o One ganglion cell gets information from ___________ of rod cell receptors, so you lose a lot of detail. Because all the ganglion knows is that one of the many rods fired but does not know which one.
tens to hundreds
o 6 million per retina most abundant in and around the ____________
o Cones have 3 types of photopigment
§ __________ (3 types of it in humans)
§ essential for __________ & more useful in _________ light
o Though cones are outnumbered, they provide about 90% of the brain's input. This is because each cell has its own connection to a ________
· 20:1 Rods to cones may sound high but the ratio is higher in nocturnal animals
fovea (part of the eye that has the best focus)
Photopigments as signals
· chemicals contained by both rods and cones that release energy when struck by light
o Consist of __________ (vitamin A derivative) bound to __________ proteins
· Light energy converts 11-cis-retinal quickly into _________ and becoming unbound to opsin protein.
· Light is thus absorbed, and energy is released that activates second messengers within the cell
· Receptor cells are more active in the __________. Light closes the __________ channels
· In the dark, the receptors are inhibiting the bipolar cells with __________.
· With light, they close the sodium channels and release less glutamate inversely proportional to the light.
· So when light hits the receptor cell, it closes the sodium channel which stops the release of glutamate to bipolar cells. This stops the inhibition of the bipolar cells leading to it firing. The bipolar cells release an EPSP to ganglion cells which then also fires.
· The central portion of the retina is the _________ and allows for acute and detailed vision
o Packed tight with receptors (_________ are highly concentrated here)
o Nearly free of _____________ and __________
· Each receptor in the fovea attaches to a single bipolar cell and a single ganglion cell known as a midget ganglion cell
· Each cone in the fovea has a direct line to the brain which allows the registering of the exact location of the input
· Our vision is dominated by what we see in the fovea (70% of input)
· The arrangement of visual receptors in the eye is highly adaptive
o Example: predatory birds have a greater density of receptors on the top of the eye; rats have a greater density on the bottom of the eye
ganglion axons and blood vessels
· Dominated by _________ receptor cells
· large numbers of rods converge onto a single ___________ and ___________ cells
o Detailed vision is less in peripheral vision
o Allows for the greater perception of much fainter light in peripheral vision (summation)
ganglion and bipolar
Color vision and visible light
· We can see visual light between ________ and __________ nm
· Shorter than 400nm is __________
400 and 700 nm
Color vision-theory 1
· 3 types of cones and these respond differently to different __________ of light
o Short wavelength (blue)
o Medium wavelength (green)
o Long wavelength (red)
§ Called red because it's the only cone that goes into the red zone but has peak response in the yellow zone
· The __________of activity across the 3 cones is how we see different color lights
· More intense light increases the __________ of the color but does not change the ratio
There are variation in the number of different types of cones animals have and a variation in the differing amounts of each cone in a person.
· Long (red) and medium (green) are most __________
· Short (Blue) is evenly __________ but red and green are not!
Human "color blindness"
· Also called ____________
· __________ is most common
o This occurs when long and medium cones produce the same __________
The trouble with trichromatic theory
· We have something called ____________ after images
· Stare at red in bright light then look at white. You will see green!
o Green becomes red
o Yellow becomes blue
o White becomes black
color vision deficiency
Color vision- theory 2
· 3 types of cones
o Short wavelength (blue)
o Medium wavelength (green)
o Long wavelength (red)
· This theory states that color is not just these cones are turning on and are combining to form a new color but that the brain has a mechanism that perceives color on a ___________ from red to green and another from yellow to blue
· A possible mechanism for the theory is that bipolar cells are _________ by one set of wavelengths and __________ by another
o For example, if you look at red, then the red receptor fires but inhibits green, but when your not staring at red anymore and look at the white, then the green receptor fires producing a green color
· But it seems to be more complicated than that!!
o There must be some __________ contribution since it is context-dependent
Opponent Process Theory
Color vision -theory 3
· ___________ adds on to the other 2 theory and suggests the cortex compares information from various parts of the retina to determine the brightness and color for each area
o Better explains color and brightness constancy
· We have different photopigment, and the ratio of the activity of those photopigments are important.
· The cells might be activating and inhibiting each other in different patterns
· Also, our brain is meddling around in how we see color.
Combined color theory
How does the brain really process all this information?
· At any given moment, your rods and cones send a quarter of a billion messages... you can't process that...
o An example of one way we deal with it is to highlight edges
o One way you do that is __________
· Lateral inhibition sharpens contrast to emphasize _________
· Receptors send messages to __________ the closes bipolar cells AND slightly ___________ their closest neighbors.
· The receptor cell that receives more light has a stronger inhibition on the lateral cells
· Rods and cones of the retina make synaptic contact with horizontal cells and bipolar cells
· _____________ are cells in the eye that make inhibitory contact onto bipolar cells
· Each receptor cell can pick up a little piece of information out in the world that is in its receptive field
· Our _____________ is responsible for piecing all the information together brain
Nerves travel back into processing areas
· Ganglion cell axons form the ____________
· The __________ is the place where the two optic nerves leaving the eye meet
· In humans, half of the axons from each eye cross to the _________ side of the brain in the optic chiasm
· Information from the temporal side is processed on the ____________ side
· Visual information is processed on the __________ half of the brain
· The right visual field hits the interior portion of the right eye and is carried to the __________ side of the brain and it also hits the exterior portion of the left eye (temporal side) and travels ipsilaterally to the brain. Same with left visual field
· Most ganglion cell axons go to the __________ (in the thalamus), a smaller amount to the __________(midbrain), and fewer to other areas
lateral geniculate nucleus
Vision in the superior colliculus
· This area is responsible for many of our ___________.
· The superior colliculus is what lets you seamlessly track objects using eye and head movements.
· Example, if you take your phone and move it around you can't read what is on the screen but if you move your head around and not the phone you can read what is on the screen.
Vision in the thalamus
· ______________ of the thalamus
o The __________ LGN receives input from the right visual field.
o The _________ LGN receives input from the left visual field.
· Acts as relay to __________
lateral geniculate nucleus
· The area responsible for primary visual processing
· Damage to Primary Visual cortex can cause:
o You can have cortical blindness while you still have blindsight
§ ___________: an ability to respond to visual stimuli that they report not seeing
§ If you have visual information going into the superior colliculus, then your visual reflex could be intact, but your visual perception is not.
§ Example, ducking when a ball is thrown at them even if they cannot see the ball
Primary visual cortex
Hubel and Wiesel's experiment
· They inserted recording electrodes in the primary visual cortex of the cat brain
· They showed cats different pictures hoping to get activity in their brains, but it turns out that the cats were not very responsive to any of the picture. but when they took the slide out of the projector and put a new slide in, one of the cats had cells that started firing
__________ in primary visual cortex 1 (V1) respond to lines of a certain _________.
__________ in V1 and V2 only respond if the line is moving in a certain __________.
· It turns out that we have these amazingly organized ___________ in the brain
· The cells responding to a particular slant pattern are arranged in the _____________.
· You have a cell that tells you that you're looking at a line that is up and down, side to side and so on.
ocular dominance columns.
How do you perceive the world?
· 80 brain regions contribute to vision
· Although you see something as a whole, your brain sees it as parts
Simple and complex cells work together
· simple cells become active when they are subjected to stimuli such as ________
· Complex cells then combine the information of several simple cells and detect the __________ and ________ of a structure.
· ____________ cells then detect endpoints and crossing lines from this position and orientation information,
· Then the brain's ___________ processes info for information association.
· So every set of cells is getting a little bit more information, and that information is coming from how the cells before it behaves.
position and orientation
Each visual cortex "understands" something more complex
· As we move through different levels of visual cortex, we get more information and understand something more complex. The primary visual cortex was just lines and by the time you get to V3 you are looking at form or motion.
· The ____________ identifies and recognizes objects. (what pathway)
· The _____________ tells us where the objects are and how they are moving. (where pathway)
· The dorsal stream goes through the ___________ lobe.
· It receives mostly ______ signals.
· This is how we locate objects.
o It is closely associated with the ___________ and __________ areas of the brain.
o This is where body motion and vision are integrated.
somatosensory and motor
· The ventral stream goes through the _________ lobe
· It receives mostly ________ signals.
· This is how we recognize objects.
o It is closely associated with the language areas of the brain.
o Damage causes _________. (when you can not come of with the name of something)
temporal (auditory part of the brain)
3 types of shapes are hard wired
· Place (parahippocampus)
· Face (fungiform gyrus in inferior temporal cortex)
· Body (fungiform gyrus in inferior temporal cortex)
· It seems your brain learns to "average" the faces it sees and focuses on ___________
· Several brain areas are important, damage to any of these areas can cause _____________
o Cannot recognize faces even in their loved ones
Infant and face recognition
· Infants are extremely drawn to faces
o They are fixated on faces the most
· It turns out the face does not have to be normal looking for an infant to fixate on.
o As long as the eyes are on top, they prefer that face
· Animal studies have greatly contributed to the understanding of the development of vision
· Early lack of stimulation of one eye leads to synapses in the visual cortex becoming gradually __________ to input from that eye
· Early lack of stimulation of both eyes means that its __________ to form synapses but does not cause blindness.
· ___________ is a condition in which the eyes do not point in the same direction
o Usually develops in childhood
o Also known as "lazy eye"
o Happens if two eyes carry unrelated messages leading to the cortical cell leads to strengthens connections with only one eye
o Development of _____________ is impaired
· ___________ refers to a blurring of vision for lines in one direction caused by an asymmetric curvature of the eyes
o 70% of infants have astigmatism
stereoscopic depth perception
Perception- optical illusions help us understand how we see
· Our vision has ___________ which is when you brain corrects the color of something by assuming there is a filter there
· Area _________ of the visual cortex compares objects to their surrounding environment.
o It automatically adjusts how we perceive color (and brightness)
Perception - Motion
· Motion perception involves a variety of brain areas in all four lobes of the cerebral cortex but is often thought of as part of __________
· Several mechanisms prevent confusion or blurring of images during eye movements
o ___________ are a decrease in the activity of the visual cortex during quick eye movements
§ neural activity and blood flow decrease 75 ms before and during eye movements
· ___________ refers to the inability to determine the direction, speed and whether objects are moving
o Likely caused by damage in the _________
· Some people are blind except for the ability to detect which direction something is moving
o Area MT probably gets some visual input despite significant damage to area V1
Middle Temporal Cortex
· ___________ is a method of perceiving distance in which the brain compares slightly different inputs from the two eyes
· Relies on retinal disparity or the discrepancy between what the left and the right eye sees
· The ability of cortical neurons to adjust their connections to detect retinal disparity is shaped through ___________
· How can you tell how far away distant objects are?
o Visual context.
· Children are not very good at this.
Stereoscopic depth perception
· Your visual system is made up of different processing modules.
· Each module makes certain assumptions:
o Highlights and shadows represent the contours of an object.
o When a line suddenly changes directions, that means there is an edge or bend.
o Parallel lines converge as they get farther away.
o Closer objects cover up more distant objects.
· So optical illusions can happen when:
o Your dorsal "where" pathway detects motion even when there is none.
o Or when your line detectors think a line is slanted/curved when it's straight.
o Etc. Basically, your cortex registers something that isn't there.
· Optical illusions can also affect the ventral "what" pathway.
· Compressions and expansions of air (or water)
· __________- the number of compressions/sec (Hz)
o Related to ____________
· __________ - the energy of the sound, how high the waves are (db)
o Related to __________
· Frequency and pitch are related to but not exactly the same as pitch and volume
· Pure tones
o A single not being played
· Complex sounds
Sensation and perception
· Its not a 1 to 1 ratio when we compare frequency and pitch or amplitude and volume
o This picture illustrates that there are frequencies that we are more in tuned with. It just so happens that part is where the human voice frequency lie in.
o This picture also shows that we are more sensitive to change in frequency at certain frequencies compared to others
· The _________- the structure of flesh and cartilage attached to each side of the head
· Responsible for:
o Altering the reflection of sound waves into the middle ear from the outer ear
o Helps us to locate the source of a sound
· The ____________ vibrates at the rate of the sound waves
o Also known as the ___________
o Both outer and middle ear are air-filled
· Connects to three tiny bones called _________, _________, and ___________
· These bones act as a lever to transform waves into stronger waves to the ___________
o Oval window is a membrane in the inner ear
o The reason why we need to make the waves stronger is because the inner ear contains __________
(malleus/hammer, incus/anvil, & stapes/stirrup)
o snail shaped structure
o subdivided into 3 fluid filled structures.
· Stapes hit the oval window
· Waves travel through fluid in the ____________
· Vestibular canal connects with __________ and sends the waves through
· Both Canals vibrate the _________ which is where the auditory receptors are located!
· Vibrations make the __________ in the cochlea move.
· On the basilar membrane is the ___________
o Consist of 4 rows of specialized cells called _________
organ of Corti
· The base of the membrane near the oval window is __________.
o ____________ sounds make big waves here.
· The tip of the membrane at the end of the cochlea is ___________.
o _____________ sounds make big waves here.
· This differential responding to frequencies makes the cochlea ____________.
· __________ are the sensory neurons of the ear.
· They have many small stereocilia facing up toward the ____________
· They are activated when the shorter cilia lean toward the taller cilia.
· It is __________ gated, the movement of the hairs opens cation channels
o This releases neurotransmitters from the other end of the cell.
o This activates the sensory neuron, which sends an action potential to the brain.
o Law of specific nerve energies, the firing of that specific hair cell indicates a specific pitch
Hair cells (inner)
Outer hair cells
· Outer hair cells also sit on the basilar membrane, but they are attached to the _________. They can pull the tectoral membrane ___________ to the inner hair cells at specific points along the basilar membrane so you can focus your hearing on a particular frequency range. Because if the tectoral membrane is closer to the hair cell, smaller movement of the hair cell can cause them to hit their head on the tectorial membrane.
· You can also push the tectoral membrane father away to reduce input from other sounds
· This decays in __________
___________ theory of audition
· The basilar membrane is like piano strings.... and use resonance
· fast and slow vibrations make different areas of the cochlea vibrate.
· This is the most influential explanation
o Various parts of the basilar membrane are ___________ to vibrate independently
_________ theory of audition
· Individual neurons fire at the rate of the vibration received.
o faster vibration makes the nerve cells fire faster.
· But if you account for the refractory period, max firing would be 100 Hz... much lower than our highest frequencies (20000 Hz).
· Both of these principles are used.
· For low frequency sounds (up to 100 Hz, below middle C) =we use both place and frequency theory
For high frequency sounds = place theory
· The quietest sound that you can perceive
o Varies with __________
· Most of our hearing is between 20 and 20000 hz
o Piano ranges from 27 - 4000 Hz
· Tone Deaf
o___________: the impaired detection of frequency changes (tone deafness)
o Associated with thicker than average auditory cortex in the right hemisphere but fewer connections from auditory cortex to the ___________
o This shows that the frontal cortex play a part in tone detection
· Perfect Pitch
o Very good at determining small changes in frequency
o Genetic predisposition may contribute to it
o the Main determinant is extensive musical training
o More common in tonal languages
· Age matters
o Children hear higher frequencies than adults
o the ability diminishes with age and exposure to loud noises
· ___________ hearing loss
o damage/impairment to the middle ear or tympanum.
o This can be corrected by a hearing aid or surgery.
o Congestion and infection can also cause conduction loss by filling the middle ear with viscous fluid.
· __________ hearing loss.
o Damage to the hair cells or auditory nerve
o Loud noise & music can damage the hair cells.
o _____________ is a common side effect.
o Damage to _________ hair cells can cause inability to focus on a particular sound
o High-frequency hair cells are lost first
Two categories of hearing impairment include:
o ______________/__________ occurs if bones of the middle ear fail to transmit sound waves properly to the cochlea
o Caused by disease, infections, or tumerous bone growth
o Normal cochlea and normal auditory nerve allows people to hear their own voice clearly
o Can be corrected by surgery or hearing aids that amplify the stimulus or cochlear implants
o __________/__________ results from damage to the cochlea, the hair cells, or the auditory nerve
o Can vary in degree
o Can be confined to one part of the cochlea
§ People can hear only certain frequencies
o Can be inherited or caused by prenatal problems or early childhood disorders
o Cannot be treated
Conductive/middle ear deafness
Nerve or inner-ear deafness
Cochlear implant (CI)
· A ___________: Put out in the environment and picks up sound from the environment.
o Attached to a __________ which selects and arranges sounds picked up by the microphone.
· A _________ and __________: receive signals from the speech processor and convert them into electric impulses.
· An ___________: lined inside the cochlea
o collects the impulses from the stimulator and sends them to different regions of the auditory nerve causing them to fire using electricity
· Hearing through a cochlear implant is different from normal hearing
o it allows many people to recognize warning signals, voices.
o BUT not music...
transmitter and receiver/stimulator
Nerve travels back into processing areas
· Neurons from the 2 cochlea make up the 8th cranial nerve- _____________
· Travels to ___________(midbrain)(duck when you hear loud sound before you know what it is) and _____________ (thalamus)
· Information from the thalamus is then relayed to the auditory cortex in the ___________ lobe
· Information is processed mostly __________.
medial geniculate nuclease
Hearing ventral and dorsal streams
o The __________ stream determines location
o The _________ stream is active when you are distinguishing or identifying sounds
The auditory cortex
· In vision you had orientation columns
· The auditory cortex provides a tonotopic map in which cells in the primary auditory cortex are more responsive to preferred tones. Some cells respond better to complex sounds than pure tones
Sound localization depends upon comparing the responses of the two ears
· Three cues:
o Louder to the closer ear
o Phase difference between the ears
o A sound coming from anywhere other than straight ahead or straight behind reaches the two ears at different phases of the sound wave. The difference in phase is a signal to the sound's direction. With high-frequency sounds, the phases can become ambiguous.
Time of arrival
Processing complex sounds
· Many association areas integrate sound and other sensory and cognitive information.
o The area we use to understand language is located near the auditory cortex. (also, partly responsible for language)
o Integrating sound and vision information is crucial for reading.
· Other cortical areas feed back into the auditory cortex.
o The prefrontal lobe feedback to the auditory cortex which lets you imagine sounds and get songs stuck in your head.
· Language is unique to humans.
o We have ___________ language.
§ That means we can use language to create new representations and meanings.
· Language is a __________ function.
o In most people*, it is processed on the left side of the brain.
· Different types of language tasks require the activation of different areas.
o Reading, listening and speaking all have unique patterns of activation.
· Understanding spoken language requires activation of the ____________ and ___________.
auditory cortex & Wernicke's area
Language: Wernicke-Geschwind Model
· If you are asked a question
o You get activation of __________ as your listening
· __________ (makes sense of the words)
· _________ (formulates articulation-what you are going to say back)
· _______________ is then used to speak the answer
Language is stored throughout the brain
· Nouns produce activity below Wernicke's area
· Verbs are impaired by damage to left premotor cortex. (tool names are here too)
· Cursing appears to have a different pathway than "normal" speech.
o Emotional centers such as the amygdala are activated.
o There is nevertheless some semantic to cursing*.
o Damage to the language system often leaves cursing intact
· ___________ aphasia: the inability to understand speech.
· ___________ aphasia: the inability to produce speech.
· _________ aphasia: the inability to integrate speech information.
o The ability to understand speech and form words, but words are randomly replaced with incorrect words.
· People with aphasia know what they want to say but they can't say it
The __________ system contributes to our sense of balance and head orientation.
· This is often called __________
· It gives us a sense of which way is up & how the head is moving.
· This lets us make compensatory eye movements to track objects and sense which way is up when the head is tilted/moving.
· The vestibular organs are located just above the ________.
The vestibular system
· The vestibular system contains three ___________ and two ___________.
o ____________ measure the acceleration of the head.
o The __________ measure what direction the head is tilted.
· Adaptation to movement is why you become dizzy after spinning in one direction.
· Otolith organs contain small stone-like crystals called the _________.
o Otoliths are denser than the fluid they reside on, so they press down on the _________ membrane.
§ This pressure triggers hair cells as you rotate your head which tells you about the position of your head.
· The two otolith organs are called the __________ and __________.
They are oriented ___________ to detect a wide range of head tilt directions
utricle and saccule
· When your vestibular system and your eyes are telling you different things about the world, this results in ___________
o If you read while in the car, your eyes think you're staying still while your vestibular system says you're moving.
o In free-fall (zero-g), the otoliths don't press down.
o When you get off of a merry-go-round, the fluid in your semicircular canals is still moving.
· If your vestibular system thinks you are spinning around, it gives you saccades.
o rapid movement of the eye between fixation points.
· A small piece of bone-like calcium breaks free and floats within the tube of the inner ear.
· Acts like an otolith but not the same density as one
· This sends the brain confusing messages about your body's position.
· There are no major risk factors.
o the condition may partly run-in families.
o prior head injury (even a slight bump to the head)
o inner ear infection
Benign paroxysmal positional vertigo
· A collective term for ________ signals from the body
o Touch, pain, temperature, kinesthesis (aka proprioception: meaning position of the limb)
· Skin is the largest organ
· Hand, tongue, and mouth have the most sensory receptors
· _________ of the receptors also gives us different size receptive field
o We have small receptive fields in the hand
o_________ the receptive field, the fewer number of receptors that converge onto a single neuron
Why is somatosensation important?
· Important to not hurt yourself
· Therapeutic uses: Premature babies have better outcomes for weight gain, and metabolism when they are given message therapy
· Message can be healing to muscle
· Pain is an important warning system
· Temperature to seek thermally safe environment
· Mechanical sensation for sexual and reproductive activities and for communication of thoughts and emotions
o Kinesthesis: coordinated in part by cerebellum
· Knowledge of the world that is derived from sensory receptors in skin, muscles, tendons, and joints, usually involving active exploration
o You rub you hand up and down the sweater to see if it is soft
· This is an active process: Action for perception (most active of 5 senses)
o Touch relies on action to get info (as opposed to vision or audition, which are more passive)
o We then use this knowledge (perception) to act
Action for perception
· We have multiple actions that we use to perceive an object via touch
· __________: feel an object to learn about it
o Different procedures tell you different things
· Lateral motion: identifies _________
· Pressure: identifies _______
· Static contact: identifies _________
· Unsupported holding: identifies _________·
Enclosure: identifies __________ and ___________
· Contour following identifies ____________ and ______
· DIFFERENT WAYS WE TOUCH IT WILL TELL US DIFFERENT THINGS
global shape and volume
global shape and exact shape
Perception for action
· Using somatosensation is also used to grasp and manipulate objects in a stable and coordinated manner and to maintain proper balance and posture
· Your fingers are adapted to be able to detect/extract certain features of objects
o Surface (rough/smooth)
o Density (hard/soft)
o Temperature (warm/cold)
· Touch receptors may be:
§ Used for Warm, cold and pain
o _________ receptors
o Eg . modified dendrites
§ Merkel disk
o elaborated neuron ending
· Stimulation of touch receptors opens _________ channels which trigger an action potential
Simple bare neuron ending
· Mechanoreceptors: activated by physical force
· Stretching or displacement of the skin causes them to open channels to activate them
· When they are activated, they send APs up the axon towards the _________
· The sensory neuron cell body is located in the __________
· These are __________ fibers- they go toward the CNS.
· Shallow layer sensors:
o __________ and ___________
§ These are used for fine detail and movement (stroking an object to explore its shape)
· Deep layer sensors:
o _____________ and ____________
§ Senses stretch
§ Perception of the shape of a grasped object
Meissner's corpuscle and merkel disk
Pacinian corpuscle and Ruffini endings
· These receptors are wrapped around ___________ so if the hair moves the receptor fires
· Degree of complexity varies
o Cat whiskers are very good unlike ours
· Usually __________ adapting
o Meaning if your hair initially touches your shoulder you will feel it, but then you don't feel it anymore because it adapted to it
· In ___________ just below epidermis...not as deep as Pacinian corpuscles
· ___________ receptive field
· __________ adapting
o Fire trains of APs when stimulus _________ and _________, not during maintenance
· The capsule is made out of ___________
· Fiber(s) of the nerve winds thru stacks of Schwann cells
· ___________ pressure compresses nerve endings w/in the stacks
· The Meissner corpuscle is abundant in fingertips
· They are very good for ___________
o Meaning if you wrap your around something you can determine what it is unlike using your hair
glabrous skin (hairless)
begins & ends
· Located on __________ and _________ skin in deep layers of dermis and subcutis
· Respond to 1 micron of skin indentation
· _________ receptive field
o Meaning a lot of Pacinian corpuscles converge onto a single neuron
· ___________ adapting
· Made of concentric layers of thin ___________ with fluid between the layers
· Quickly applied forces are transmitted thru __________ while maintained forces are not
o so responds upon application & withdrawal of stimulus, not maintenance, hence rapidly adapting
· Bad for sustained pressure; good for sudden force or rapidly changing mechanical stimulation (vibration)
· Force -> neuron's membrane is deflected -> channels become leaky to sodium -> action potential
· Onion like outer membrane provides mechanical support so it is resistant to gradual or constant pressure...so rapidly adapting. BTW, the other rapidly adapting receptor, Meissner corpuscle , works in a similar way
hairy and glabrous
· Widespread in:
o Subcutaneous tissue
o Other connective tissues
·____________ receptive field, ___________ adapting
· They have a __________ shaped capsule transverse by strands of ___________ connective tissue
· When the fibers enter the capsule, it branches, and small fibers are interspersed among collagenous strands
· When you apply tension to one or both ends of the terminal, the fibers become activated
· Deformation of ending maintained as long as tension is maintained, hence slowly adapting.
· Respond to pressure
· Different parts of the body have different sensitivities to touch.
o A group of sensory neurons that converge on the same neuron in the spinal cord form a __________.
· The more closely-packed these fields are, the more sensitive the area is to touch stimuli.
Women have better detail touch than men
· _________ is responsible for this
· Men and women generally have the same number of Merkel disks, but women tend to have smaller fingers
o Results in Merkel disks compacted into a smaller area
o More sensitive to feeling the distances between grooves
Temperature and thermoreceptors
· Warm and cold fibers are made of ___________
· Located in the dermis and epidermis in clusters also called ____________
o Warmth receptors are located _________ compared to cold
· They respond to __________ in skin temperature
o Normal skin is 30-36C (86-96F) ...neither type of fiber fires much in this range.
o Respond if the temp is higher or lower than neutral, or higher or lower than what skin is used to
o So, feeling temp is relative (try the hand in the bucket experiment!)
§ If you put your hand in lukewarm then you wouldn't feel it because its body temp. but if you put your hand in hot, then lukewarm then it would feel cold
· Temperature is sensed through_____________
o _____________ cation channels in cell membrane
o To detect such a large range of temps, probably need more than 1...turns out we have at least 6 different TRP channels for temp, all the TRP channels are tuned to a specific range of temperature.
o Extreme temperature on either end are considered painful
o BTW, some thermoreceptors also respond to chemicals!
free nerve ending
TRP (transient receptor potential channels)
Touch receptors to the brain
· Information from touch receptors in the head enters the CNS through the _________
· Information from receptors below the head enters the__________ and travel through the 31 spinal nerves to the brain
· Each spinal nerve has a sensory component and a motor component and connects to a limited area of the body
· __________: a skin area connected to or innervated by a single sensory spinal nerve
o They overlap meaning some sensory information goes to multiple spinal nerve so you don't get any dead zones
· Sensory information entering the spinal cord travel in well-defined and distinct pathways
· Example: touch pathway is distinct from pain pathway
· Various aspects of body sensations remain ____________ all the way to the cortex
· Various areas of the somatosensory thalamus send impulses to different areas of the somatosensory cortex located in the _____________
o Every sense goes through the thalamus except smell
· Different sub-areas of the somatosensory cortex respond to different areas of the body
· Damage to the somatosensory cortex can result in the impairment of body perceptions
· The homunculus corresponds to the areas of greatest innervation in humans.
· Different animals have different relative sensitivity.
· Rats investigate with their nose & mouth more than anything else.
o Each whisker has a large field of cortical representation.
o These are called ___________
· Pain is the experience evoked by a harmful stimulus, directs our attention, and holds it
· Pain sensation begins with the least specialized of all receptors called ________
· Some pain receptors also respond to acids, heat, or cold
o __________: a chemical found in hot pepper; stimulates these receptors
· Axons carrying pain info have little or no __________, so impulses travel slowly
· However, the brain processes pain information rapidly and motor responses are fast
· Mild pain triggers the release of ___________ in the spinal cord and stronger pain triggers the release of __________ and ____________
o Substance P results in the increased __________ of pain
bare nerve endings
glutamate and substance P
Pain receptors (nociceptors)
· They can be:
o Mechanical: pinching and cutting
o Thermal: hot and cold
o Polymodal: all mechanical and thermal plus chemicals released when tissue is injured
· The stimulus for pain is IN YOU: The receptors do not detect pain, they cause pain
· Pain is pure perception, and the stimulus is __________
· Lesion causes blood, the chemicals in the blood send information to the dorsal root ganglion and neurons which causes the release of ____________. This leads to more blood -> more pain -> more substance P
Pain and touch are not the same things
· They use different pathways
· Touch moves into the spinal cord and travels _________ and crosses to the contralateral side when they get to the thalamus.
· Pain crosses to the _________ half of the spinal cord and travels up the spinal cord into the brain
· _________ pathways cross to a tract ascending the contralateral side of the spinal cord
· Pain-sensitive cells in the spinal cord relay information to several areas of the brain
o ___________ cortex responds to painful stimuli, memories of pain, and signals that warn of impending pain
· Central nuclei of the thalamus, amygdala, hippocampus, prefrontal cortex, and cingulate cortex are associated with _________ associations
· Opioid mechanisms are systems that are sensitive to opioid drugs and similar chemicals
o Activating opiate receptors blocks the release of __________ in the spinal cord and in the ____________ area of the midbrain
· ___________ dumps substance P so you have to remake it so you do not feel pain OR can damage the actual pain receptor
· Cannabinoids are chemicals related to marijuana that also block certain kinds of pain
o Act mainly in the periphery of the body
· The spinal cord areas that receive messages from pain receptors also receive input from _______ receptors and from axons descending from the _________
o These other areas that provide input can close the "gates" and decrease pain perception. So, non-pain stimuli around it can modify the __________ of the pain
· Pain signals ascend the pain pathway and reach conscious awareness in the thalamus & cortex.
· "Descending" pathways can keep the CNS from receiving pain signals.
o They close the gate to pain.
· The CNS activates neurons that release ____________.
o This blocks the release of _____________
o This keeps pain signals* from getting in.
· So you can use your touch fibers to reduce pain or you can use your brain to block pain by thinking about something else
· A placebo is a drug or other procedure with no pharmacological effect
· Decreases pain perception by decreasing the brain's ___________ response to pain perception, not the sensation itself
· Decreases response in _________ cortex but not in the ___________ cortex
· Certain receptors become potentiated after an intense barrage of painful stimuli
o Leads to increased sensitivity or chronic pain later
· Emotional pain resembles physical pain in many regards:
o Increased activity in the __________cortex when someone felt left out of an activity
o People taking acetaminophen (Tylenol) reported less incidences of hurt feelings and social pain
· Itch is not pain
· The release of _________ by the skin produce itching sensations
o Activates a distinct pathway in the spinal cord to the brain
o Impulses travel slowly along this pathway (half a meter per second)
· Pain and itch have an ___________ relationship
o __________ increase itch while _________ decrease itch
· Poorly understood
· Maybe social communication
· The laughing is not normal laughter in that it doesn't predict subsequent laughter
· Most people do not like to be tickled
We use chemical cues for the 3 main tasks we have as critters
· Taste and Smell are one of the ways we understand the world
· Olfaction is the sense of smell
· refers to the detection and recognition of airborne chemicals that contact the membranes inside the nose
variation in scent detection
· A human can follow a scent trail to some extent, and we get better with practice
· A Dog can smell an oncoming seizure by detecting chemical change in the body
· Olfactory receptors
o located on _________ which extend from the cell body into the mucous surface of the __________
· Vertebrates have hundreds of olfactory receptors
o highly responsive to some related chemicals and unresponsive to others
· the receptors in your nose work via a __________ pathway
o Longer to onset 30 ms+
o Longer lasting, several seconds - several minutes
o Wide variety of neurotransmitters (dopamine, norepinephrine, serotonin, GABA and glutamate)
o Well suited for enduring effects like taste, smell, or pain
Olfactory receptor protein
· The olfactory receptors are transmembrane receptors
· Proteins in olfactory receptors respond to chemicals outside the cells and trigger changes in __________ inside the cell
· G protein then triggers chemical activities that lead to action potentials
How does smell work?
· __________ depolarize olfactory receptors in the nasal cavity.
· Odorants are small, hydrophobic, airborne molecules.
· Olfactory receptors send APs to _______ in the olfactory bulb.
o Glomerulus is a synapse between the olfactory cell and cells in the olfactory bulb called the _________
· Each glomerulus reacts to multiple odors.
· The __________ of glomerulus activation is unique to each odor.
· The olfactory receptors cells move past the ___________ to reach the glomerulus
Smell in the brain
· Smell goes from the glomeruli directly to the _________ cortex which is the olfactory cortex.
o Unlike all other senses, it doesn't make a stop in the ________.
· It also projects directly to the ____________.
o This provides an immediate emotional reaction (e.g., disgust) to certain odors.
The dangers in olfaction
· Olfactory receptors are replaced approximately every ________ but are subject to permanent impairment from massive damage
· Receptors regenerate within a month
· The olfactory epithelium has __________ enzymes similar to the liver.
o This is to protect the ________ from toxic smells
· What is a big deal is that the odorants can get pass the cribriform plate and start to damage brain cells
· The __________ is a set of receptors located near the olfactory receptors that are sensitive to pheromones
· Pheromones are chemicals released by an animal to affect the _________ of others of the same species
· The VNO and pheromones are important for most mammals, but less so for humans
o The VNO is tiny in human adults and has no receptors
· Humans unconsciously respond to some pheromones through receptors in the _____________
o The smell of a woman's sweat (especially when she is near ovulation) increases testosterone in human males.
o This is different from other pheromonal drives because it doesn't change behavior, it only alters the physiological response
o The best-documented example is female cycle synchronization
vomeronasal organ (VNO)
Retro nasal olfaction
· Important for our food selection; linked to __________
· When you eat food, the smell of the food travels up the throat and into your nasal cavity.
· Up to 90% of flavor discrimination is based on ____________.
Taste vs flavor
· Taste refers to the stimulation of the ___________, which are receptors on the tongue
· Our perception of flavor is the combination of both __________
o Taste and smell axons converge in the ___________
taste and smell
· Each part of the tongue is capable of detecting ________ of the taste sensations.
· Sweet, salty, sour, bitter, and umami
o Some are arguing for fat, starch, water, and calcium
· Receptors for taste are _________ cells, not a neuron but attaches to one
o These can be rebuilt because if you eat something hot, you destroy them, but the taste receptors come back.
· Taste receptors have excitable membranes that release neurotransmitters to excite neighboring neurons
· Taste receptors are replaced every __________ to _______ days
10 to 14 days
· __________ are structures on the surface of the tongue that contain the taste buds
· Each papillae may contain up to ten or more _____________
· Each taste bud contains approximately 50 receptors
· Most taste buds are located along the _________ edge of the tongue in humans
· Inside the taste bud you can see these pores.
· The pores are where the ___________ cells are located
· In order to taste something, the food has to be dissolved by saliva and go into the taste pores to reach the taste receptor
· TASTE ARE _________ WHILE SMELL IS ____________
· Different taste buds are better at detecting different tastes.
· This is due to differing distributions of ____________.
· There are also taste buds in the __________ and on the roof of a rat's mouth.
· Taste cells detect ____________ via membrane receptors.
· When the tastant interacts with the cell, it __________ the taste cell.
· This causes neurotransmitter release to the taste neurons.
· These neurons send the taste signal to the brain through the ___________.
tastants (taste molecules)
Chemoreceptors are different for different taste
· Ion channels
· Metabotropic receptor
Taste - Salty and Sour
· Taste cells that detect salty flavor depolarize in the presence of ___________
o Sodium ions enter the cell through a channel.
· Cells that detect sour flavor depolarize in the presence of _____________.
o H+ blocks the _________ channel.
o Potassium builds up, depolarizing the cell.
· ___________ receptor
o G-protein coupled receptor (GPCR)
· Heterodimer of _________ and __________ subunits
· Heterodimer of _________ and ________ subunits
· Umami receptors are very similar to sweet receptors.
· The different protein subunit makes the receptor respond to either sugars or glutamate.
T1R2 and T1R3
T1R1 and T1R3
· Family of ~30
· __________ subunits
· Distinct from sweet and umami receptors
· There are many different bitter receptors on the tongue.
· Each receptor responds to a different type of bitter molecule.
o Often plant toxins.
o Diverse array of molecules.
· Bitter sensations can produce a strong __________
· _________ nerve carries taste information the anterior two-thirds that nerve is also called the ___________
· _____________ nerve carries taste information the posterior tongue and throat
· Taste nerves project to a structure in the medulla known as the _________________
o Projects information to various parts of the brain
· It is believed that the unique combination of neurons that each food stimulates is what gives each food a unique taste.
chorda tympani nerve
nucleus of the tractus solitarius (NTS)
· The ____________ nerve (a cranial nerve) detects burning sensations in the nose and mouth.
· This includes spicy foods that contain capsaicin.
· This includes abrasive odors such as ammonia.
· This sensation is distinct from normal taste and smell.
Taste neurons in the nerve
· The nerve is a bundle of neurons that travel to the brain
· Some of the nerves are ___________
o They fire to specific taste
· Some are ___________
o They fire to more than one type of taste
Taste in your brain
· Various areas of the brain are responsible for processing different "taste" information
· The ______________ projects to the ___________ portion of the thalamus
· The thalamus projects to the _________, or the _______________
o The somatosensory cortex responds to the touch aspect of food
· Each hemisphere of the cortex is also responsive to the ____________ side of the tongue
NTS (nucleus of the tractus solitarius)
primary gustatory cortex
· The insular cortex, amygdala, and the PVN (paraventricular nucleus in the hypothalamus) all respond strongly to taste.
· If you give a rat a treat and then inject it with something that makes it feel sick, then it will avoid that type of treat in the future.
· This is called _____________
· It is so powerful; it can be learned after only one trial.
conditioned taste aversion.
Taste variation in people
· ____________ and ___________ can account for some differences in taste sensitivity
· Variations in taste sensitivity are related to the number of ___________ near the tip of the tongue
· ____________ have a higher sensitivity to all tastes and mouth sensations in general
o They have a higher density of taste buds
· There are "taste" receptors in your gut and brain too!
o These taste receptors are similar in shape and function in terms of interacting with compounds such as glucose
o The taste receptors in the brain probably detect glucose for food and in the gut, they detect toxins to determine whether you should evacuate them or not
Genetic factors and hormones
Taste is fun
· Toothpaste contains sodium lauryl sulfate
· Intensifies bitter and weakens sweet
· After brushing, your sweet receptors are still modified by the SLS.
· Synsepalum ducificum (miracle fruit)
o Binds to sweet receptors and make it sensitive to hydrogen ions
o Causes sour to be sweet
· Gymnema sylvestre
o Sugar becomes tasteless
· The experience of one sense in response to stimulation of a different sense
o Estimates suggest 10% of 6-7-year-olds, though it develops gradually out of it
· Caused by axons from one cortical area branching to another cortical area
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