Science Section 3 Flashcards
When do you become aware of external stimulus
Only when the stimulus make its way up to the cerebral cortex that you become aware
What is phototransduction
when a receptor is activated by its preferred stimulus, the receptor is cell is depolarized leading to an action potential and or transmitter release
What cells transmit information out of the eye via action potentials potentials via their long axons
Retinal Ganglion Cells
Where is the blind spot in the eye
The point of where all these axons come together to exit out of the eye
What is the center of retina?
The center of the retina is called the fovea
What does the pupil do?
It the part of the eye that can dilate and contract to let light in
What functions do the pigmented epithelial cell have?
It has many functions as absorbing excess light, so it does not scatter and blur the images. and getting rid of the old, broken down segments of the photo receptors cells.
What are the two general photoreceptor cells
Rod & cones
How many cones are in cone systems are in a primate
There are three cones (Trichromantic) system
What do photoreceptor cells do when depolarized?
Release nuerotransmitter glutamate
why is the optic nerve considered a blind spot?
There are no photoreceptors there and no light can be transduced from this spot in the retina
Where do all the axons of the retinal ganglion cells come together?
The optic nerve
Amacrine cells can…
distribute information from one bipolar cell to many ganglion cells
Horizontal cells…
form connections between one central rod or cone to many other more distant photoreceptors and between several bipolar cells
Lateral Inhibition
refers to the capacity of excited neurons to reduce the activity of their neighbors, happens when a photoreceptor depolarizes a horizontal cell and the horizontal cell acts to inhibit the more distant bipolar cells
center-surround receptive fields
When neurons in the retina become stimulated, the neurons can choose to sharpen edges and enhance contrast in the images, creating clarity in the image
purpose of center-surround receptive fields
sharpen edges and enhance contrast in the images by amplifying the edges and borders
retinal edges in the fovea are very…
small, the horizontal cell connects fewer retinal ganglion cells to a single photoreceptor allowing highly acute vision
receptive fields in the peripheral parts f the retina are..
large and reduce less sharp vision
Once light has been transduced and processed the retinal ganglion cells…
transmit that information out the eye via action potentials down their long axons
retinofugal pathway
lating for feeling, the axons of the retinal ganglion exit at the back of the eye making up the optic nerve, and go all the ay back to the thalamus and then to the visual areas of the cerebral cortex
Optic chasim
the point where axons from both eyes come together as the cross targeting the thalamus on the opposite side of the head, named after the Greek letter “chi” which looks like an “X”
optic tract
the bundles of axons after reaching the optic chiasm, used to distinguish from the optic nerve
Left vs Right
Information about the left side of the world reaches the right side of the brain and vise versa
Binocular Vision
the central portion of the visual field seen by both eyes is represented by both sides of the brain, gives depth perception by the comparison of the difference in appearance seen by the right and left eye and calculating depth based off the different
lateral geniculate nucleus (LGN)
is a cluster of cell bodies in the thalamus (grey matter), specialized for processing visual input
LGN input layers
determine that the two eyes are not mixed; instead, the information is kept in distinct layers
Damage to the Ventral Extrastriate can cause…
Difficulty recognizing visual objects
What is Prosopagnosia?
Face blindness where the patient can’t recognize people by their face
What two parts make up the Inner Ear?
The Cochlea and Semicircular Canals
Where is the Primary Auditory Cortex located?
Within the Insular Cortex
What part of the brainstem calculates where a sound comes from?
The Nuclei of the Brainstem
Organ of Corti
where auditory transduction takes place
Hair Cells have an unusually low internal concentration of ______
Potassium
What is the auditory part of the thalamus called?
Medial Genniculate Nucleus (MGN)
A1
Primary Auditory Cortex
What is our oldest type of sense?
Chemical senses
What are the 5 types of taste?
sweet, sour, bitter, salty, and umami
What is the meaning of umami?
“deliciousness”
Who identified the taste of umami?
Japanese scientist Kikunae Idea in 1908
Umami is a major flavor of what food that is common in Japanese cooking?
Seaweed
The taste of umami is described as? And our sensory experience of chemical stimuli is based on what amino acid?
Its taste can be described as savory and is based on the amino acid L-glutamate
Sweet taste indicates the presence of?
Sugar and a food dense in calories
Sour foods indicate?
vitamins and minerals
Bitter tastes can warn us away from?
toxins
Salty foods are necessary for?
maintaining homeostasis
What are the bumps on your tongue called?
papillae
What is your organ of taste?
tastebuds
Where are tastebuds located in your tongue?
They can be found near/among the papillae and are in clusters of taste cells
What are tastebuds?
Barrel-shaped structures that consist of many sensory cells in clusters
What is a tastant?
a chemical particle in food that can be transduced by taste neurons
True or False? Each taste cell functions for multiple types of taste.
False. Each of the taste cell has one general type of taste receptor that is specific to one of the 5 basic tastes (i.e. the cell can be bitter or sweet but not both
True or False? Taste (gustatory) cell do not fire action potentials
True. They do not have to travel far until they reach the neuron which will then fire action potentials to send the signal to the brain. See Figure 53
Why do out taste cells become less responsive to continuous stimulus?
Because of sensory adaptation
dorsal column medial lemniscal (DCML) system
How touch and proprioception signals get sent from the tissues to the brain
Where is all somatosensation processed?
Primary Somatasensory Cortex
How does Pain and Temperature information get sent to the brain?
Anterolateral Spinothalamic System
M1
Primary Motor Cortex
Map or representation of the human body in the brain
Sensory Homunculus (From the latin Little Man)
What cells Synapse directly onto the muscles, causing involuntary movement?
Lower Motor Neurons
What is the most famous type of motor reflex?
Myotatic Reflex (Knee Jerk Response)
What functions are associated with the primary motor cortex (M1) and its related cortical areas?
Voluntary motion, planned sequences of action, and relaying commands to neurons to execute these functions
Where does the Corticospinal tract run from?
From Cerebral Cortex to the spine, beginning in the Primary Motor Cortex
Cerebellar deep nuclei
Provide output for the structure and the cerebellar cortex
is the circuitry system involved in learning
Yes, we learn through repetition in which our brain and body to ongoing motor command
What does the circulitry system do as organisms, interact with their environment
The sensory systems brings information of the world into the brain and motor system and the central nervous system brings behavioral commands out of the brain
how does the sensory system transduce environmental signals
It does this by the language of neurons, namely, action potentials and chemical neurotransmitters
Where does the visual system begin?
It begins in the photoreceptors of the retina, transducing light into an electrochemical signal
What does the cerebellum do?
It is the part of the brain not fully understood in the learning of the new motor task and skills
What does the Fastigial nucleus do ?
The Fastigial Nucleus receives input from sections of the cerebellar cortex and process vestibular, somatosensory auditory information, and visual information
What do indirect pathways do ?
Indirect pathways inhibit excess movement occurring that is not wanted.
Where does the Vestibulospinal tract originate?
It originates in the vestibular organs of the inner ear( such as semicircular canals) that provide information about the direction of gravity, spin and other forces on the body and head
Describe the transduction of salt tastants
1). Salt tastants enter the receptor cell through ion channels that are always open 2). This depolarizes the cell which causes voltage gated calcium channels to open 3). The opening causes an influx of calcium ions to enter the cell which then causes the release of serotonin filled vesicles
Describe the transduction of sour tastants
1). As the tastants are made of hydrogen ions, they enter the cell through open hydrogen channels 2). The influx of hydrogen and since the hydrogen ions inhibit potassium leak channels (which cause the membrane potential to become more neg. as a result of potassium leaving the cell) depolarizes the cell 3). Similarly salt, the depolarization causes the voltage gated calcium channels to open for in influx of calcium into the cell which in turn causes serotonin filled vesicles to be released into the synapse
How does the transduction of sour tastants differ from that of the salt tastants?
The hydrogen in the sour tastants inhibit potassium leak channels. This prevents potassium from leaving the cell and, therefore, helps depolarizes the receptor cell
The hydrogen in the sour tastants inhibit potassium leak channels. This prevents potassium from leaving the cell and, therefore, helps depolarizes the receptor cell
No, they bind to GPCRs (G-protein-coupled receptors, aka metabotropic receptors) and those are not ion channels
Describe the transduction of umami (like L-glutamate) and bitter tastants
1). The tastants activates GPCRs that are embedded in the membrane of the cell 2). Thus, activating the PLC pathway which causes the production IP3 (second messenger) from phospholipase C (PLC– effector protein 3). IP3 then goes to cause an influx of calcium into the cell by binding to receptors in the endoplasmic reticulum 4). This depolarizes the cell which causes the release of serotonin-filled vesicles but it also causes the voltage-gated calcium channels to open which will cause the release of serotonin-filled vesicles across the synapse
Describe the transduction of naturally occurring sweet tastants (such as saccharides)
The taste cell is depolarized by the activation of the GPCRs which causes PLC to be activated which in turn splits into IP3 and DAG. Then, DAG activates PKA (second messenger) which will then close nearby potassium channels (keeping the membrane potential more positive).
In what foods are saccharides (like sucrose) found?
Fruit and carbohydrates
Transduction of artificial sweeteners (like saccharine)
They activate different G-proteins which will then activate PLC to produce IP3 (similar to the umami and bitter pathways)
What are the cranial nerves?
bundles of axons that connect the brain to the face and head
Do the regions in the head and face use the spinal cord to transmit signals to the brain?
No. Signals are transmitted to the brain by the cranial nerves
What are the three major cranial nerves?
Facial nerve (7), glossopharyngeal verbe (9), and the vagus nerve (10)
Where do the 7, 9, & 10 cranial nerves meet together?
They enter the brainstem together and target the gustatory nucleus in the medulla. Afterwards the axons project into the thalamus and then to the primary gustatory cortex
What is the primary gustatory cortex?
area in the insula cortex that is responsible for taste and flavor perception
Where can the primary gustatory cortex be found?
deep in the fissure between the temporal and parietal lobes, near the auditory cortex
What is the olfactory epithelium?
clusters of cells that line the top and back of the naval cavity that form specialized tissue and it is where olfactory receptors are found
What is the olfactory epithelium composed of?
Basal cells and support cells that provide structure. There are also olfactory [small] receptor neurons located there
Olfactory receptor neurons have specialized ____________ where airborne particles can bind to be transduced into a series of action potentials.
dendrites
How many olfactory neurons do human have?
12 million
What are odorants?
chemical particles in the air that cam be transduced
How are smell receptors able to detect smell?
They have dendrites that extend into the sensory epithelium with many hair like cilia that extend outwards and are covered with receptors for odorants to bind
Mucus layer that covers the olfactory epithelium
odorants, when inhaled into the sinus cavity, dissolve in the mucus layer that covers the olfactory epithelium. This breaks down the odorants into components that can be transduced.
What is the largest known gene family?
those that encode for odorant receptors
Are olfactory sensory neurons specialized to only detect specific odorants?
Yes, each type of neurons only have one type of of receptor on it cilia. This also means that bipolar cells are specialized.
What G-protein-coupled signaling system is used for smell transduction?
G^olf (G protein for Olfaction)
Smell signaling cascade process
1). the activated G protein sub unit begins by stimulating adenylyl cyclase (an effector protein) that produces cAMP (cyclic adenosine monophosphate) from pre-existing ATP inside the cell. 2). cAMP then binds to special cAMP ligand bound ion channels open which allows sodium and calcium to flow into the cell and, therefore, causes calcium voltage gated chloride channels to open, letting chloride out of the cell 3). All of this combined depolarizes the cell and causes it to fire an action potential that travels down the axon to the olfactory bulb
What is the olfactory bulb?
the extension of the brain underneath the frontal lobe that contains many nerves used for smelling
What is the cribriform plate?
odorants, when inhaled into the sinus cavity, dissolve in the mucus layer that covers the olfactory epithelium. This breaks down the odorants into components that can be transduced.
Why are axons of olfactory receptors so fragile? And what happens when they are damaged?
They are so fragile because they are not one big sturdy nerve as they must first break apart to pass through the cribriform plate. If they damaged by a sheering action of the skull or car accident, it may lead to permanent lost of smell
What are glomeruli?
the clusters of nerve endings in the olfactory bulb where olfactory receptor neuron terminals meet the next neuron in the olfactory system
How many glomeruli are located in the olfactory bulbs?
Two-thousand
What is the purpose of the glomeruli?
It is where axons of many specialized receptor neurons converge onto a single glomerulus this keeps info. for that odor in a specific location in the olfactory bulb.
Besides the temporal lobe, where else is information sent in the brain?
Hippocampus and amygdala
What is population coding?
a method of representing stimuli by using the coordinated activities of a number of neurons working together (that respond to a little bit of many different kinds of odorants- such as a secondary taste cell that is part of the same axon that carries multiple taste senses) are used to identify and encode particular stimuli
How are we able to encode over a trillion possible smells?
As some neurons fire at a different intensity to the same stimulus, the same population of neurons can encode different smells
What are the dorsal columns of the DCML system?
Bands of myelinated axons (white matter)
What language/word does medial leminscus originate from?
The Greek word meaning “ribbon”
What is the pathway the medial lemniscus of DCML system is named?
the name for the pathway that passes through the brainstem on the way to the thalamus
Where do sensory axons enter the spinal cord?
through the dorsal root to join the white matter at the dorsal (top) part of the spinal cord
Where does information from the lower body travel in the DCML system? And where does it synapse in the spinal cord?
It travels in the middle of the dorsal column medial leminscus system and synapses at the bottom of the brainstem at the bottom of the brainstem in the gracile nucleus of the medulla
Where does information from the upper body travel in the DCML system? And where does it synapse in the spinal cord?
Information travels more to the side of the bundle (laterally) and synapses in the cuneate nucleus of the medulla (which is next to the gracile nucleus)
When does the information coming from the upper and lower body that is separated when in the spinal cord, become integrated?
At the brainstem (the first synapse and second neuron of the pathway). This means that the first neuron of the pathway can extend from your fingertip to your brainstem where it synapses onto the next neuron in the brainstem.
Where does information from the right side of the body cross to the left side? (and vice versa)
In the brainstem
Where is the final neuron of the pathway located?
In the ventral posterior later (VPL) nucleus of the thalamus
What is another name for the anterolateral spinothalamic system?
Spinothalamic tract (b/c information travels from the spinal cord to the thalamus
What type of sensory information travels up the anterolateral spinothalamic system?
Pain and temperature
Describe the process of pain and temp. information traveling up the spinal cord via the anterolateral spinothalamic system?
1). The sensory axons enter through the dorsal root 2). Then immediately synapse on to the second neuron in the pathway (grey matter or cell bodies) where information from one side of the body immediately crosses to the other side 3). Synapses onto the VPL nucleus of the thalamus 4). The third neuron from the thalamus travels to the primary somatosensory cortex with its soma still located in the thalamus
Where is the primary somatosensory cortex located?
Front of the parietal lobe
What is the somatotopic map?
Since the neurons in the DCML and anterolateral spinothalamic pathways and in the somatosensory cortex are arranged topographically so that parts of the human body are represented (not proportionally) and opposite sides of the body are represented
What parts of the body are overrepresented in the primary somatosensory cortex (S1)?
parts with highest density of mechanoreceptors (such as fingers, hands, lips, and tongue)
Where does involuntary movement and reflexes begin?
a sensory stimulus from the brainstem and spinal cord
Where does voluntary movement begin?
in the brain and perfectly planned out before it happens
Lower motor neurons release what as their neurotransmitter?
Acetylcholine
What is the space between the terminal of lower motor neurons and muscle?
Neuromuscular junction
Describe the process of movement from the muscles
1). Lower motor neurons release ACh to the receptors in the muscles cells 2). Which causes the muscle cells to depolarize 3). Voltage-gated calcium channels open which allows calcium to flow into the cell 4). This causes the filaments inside the myofibrils to slide past each other which shortens the myofibrils 5). Resulting in the entire muscle cell contracting to shorten which moves the limb
In the absence of what neurotransmitter causes muscles to relax?
ACh
What are upper motor neurons?
neurons with cell bodies in the motor regions of the brain that carry motor commands down the spinal cord to synapse on the lower motor neurons
Where are cell bodies of lower motor neurons?
in the spinal cord or brainstem (portion for the face and neck) with axons extending out into the vertebrae forming the ventral spinal root (bottom)
What are muscle spindles?
stretch receptors buried in skeletal muscle that detect the length of a muscle and report this to the brain for proprioception, or body position perception
What are myofibrils?
long fibers of protein filaments that make up a muscle
What is an important function of the motor and premotor cortex?
mapping out which muscles and limbs need to be given a motor command in order to complete a certain movement
What is the premotor cortex?
an area of the cerebral cortex found in the back of the frontal lobe where motor commands are planned out before they are executed
What pathways for voluntary movement are considered the lateral motor system?
Corticospinal and rubrospinal tract (the corticobulbar system is often included as well)
What is the corticobulbar system?
controls brainstem nuclei their innervate cranial muscles to control voluntary movement of facial muscles (does not run through the spinal cord)
Describe the pathway of the corticospinal tract
1). Beginning in the primary motor cortex, the axons descend through the white matter (lateral side) of the brain and brain stem forming triangular bumps on the underside of both medulla 2). At the bottom of the medulla, the pathway decusses to the other side of the spinal cord (from the right to left) where they synapse on lower motor neurons in central grey matter of the spinal cord
What pathway are the longest neurons in the body found?
the corticobulbar system
What is the rubrospinal tract of the lateral motor system?
this pathway begins in the red nucleus (small region) in the midbrain of the brainstem and crosses sides in the midbrain
What is the function of the rubrospinal tract in humans?
it is responsible for the control of muscle tone
What is the name of the place where a stimulus can be detected by a sensory receptor?
The receptive field
True or false. You’re aware of a stimuli before it reaches your cerebral cortex.
FALSE
When does myopia occur?
Myopia occurs when the distance between the cornea and the retina is too long, causing nearsightedness as the image focus falls in front of the retina.
What is the choroid’s job?
The choroid brings oxygen and nutrients to the photoreceptor cells.
Why are Rods (type of photoreceptor) ideal for nighttime vision?
Rods are ideal for nighttime vision because they tend to have more discs, making them more sensitive to low levels of light.
What type of wave is usually perceive as blue?
Cones absorb short waves of light and perceive them as blue.
What happens when light is absorb by the opsin?
When light is absorb by the opsin causes a conformational change in the molecule found inside, which alters the molecule’s shape, which activates the opsin.
How can someone with face blindness recognize someone?
By their clothes, jewelry, audio cues, tattoos
What is parallel processing?
stimulus features doing sensory transduction are kept in separate “information channels”
What are Ossicles?
three include malleus, incus, stapes which increase pressure so soundwaves can be processed
What does the tectorial membrane do?
it is rigid which causes a shearing action which is the mechanism from auditory transduction
What are the five tastes of the human body?
sweet, sour, salty, bitter, and UMAMI
To which people is UMAMI unfamiliar and why
Americans, because it is usually found in Japanese cooking
how is a taste created
through the depolarization of a sweet cell through either a natural TASTANT (taste a particle of food that binds to taste receptors) or through some other mechanism.
The MGN is made up of _____
sub-regions
What does the MGN influence
the direction and maintenance of direction
where does sound enter the auditory neural pathway
the cochlear nerve and cochlear nuclei
What is the rubrospinal tract
it is a smaller component of the lateral motor system that in a human carries a good percentage of voluntary movement
where does the vestibulospinal tract originate
in the vestibular organs of the inner ear
where does the tectospinal tract originate?
the roof or tectum of the midbrain section of the brainstem where visual input is mixed with auditory and somatosensory inputs
Where does the reticulospinal tract arise from
recticular formation found in the pons segment of the brainstem
what does the reticulospinal tract do?
targets the torso and legs, extends the muscles there to combat gravity and hold yourself up
what does the tectospinal tract do?
forms your cohesive map of the world, is how you known where things are
what is the basal ganglia
the willingness to initiate movement from a still state
what does damage to the basal ganglia cause?
leads to motor impairments such as shuffling gait when walking which is just too little movement when walking
How many neurons does the Cerebellum contain?
more than half the brains neurons
what is the output for the structure of the Cerebellum?
the cellular deep nuclei
cervical spinal cord (Anterolateral Spinothalamic Pathway)
Pain and temperature information from upper body
Lumbar spinal cord (Anterolateral Spinothalamic Pathway)
Pain and temperature information from the lower body
Cervical Spinal Cord (DCML Pathway)
Mechanosensory receptors from the upper body
Lumbar Spinal Cord (DCML Pathway)
Mechanosensory receptors from the lower body
information from the upper and lower body is kept together or separate within the spinal cord?
separate
in the anterolateral spinothalamic system sensory axons enter the dorsal root and immediately synapse in the grey or white matter withing the spinal cord?
Grey matter
anterolateral comes from…
the word anterior, meaning front or before
Information in the anterolateral spinothalamic system run all together or separate?
All together in the same bundle of axons
The absence of acetylcholine from the lower motor neurons work to…
lengthen the muscle and/or relax that part of the body
motor planning
mapping out which muscles and limbs need to be given a motor command
neurons in a motor area are highly active before or during movement
these neurons are highly active before any movement is initiated and can be used to predict behavior before it occurs
3 ventromedial tracts
vestibulospinal tract, reticulospinal tract, tectospinal tract
Ventromedial Pathways
The motor pathways found in the center bottom of the spinal cord direct torso and trunk muscles and are responsible for posture and balance.
What is the epidermis?
The epidermis is the outermost layer of skin in mammals and serve as a thin barrier to water and pathogens.
What type of mechanoreceptors feature a slow adapting property?
Ruffini ending and Merkel disk.
What is glabrous skin?
Hairless skin like the one found on your hands, fingers, lips, and the soles of your feet.
What does it mean that mechanoreceptors are sensitive to mechanical input?
It means that when their nerve endings are pushed, poked, or physically deformed, channels are pulled open to allow ions to flow in, triggering an action potential.
How are the thirty spinal segments divided?
They are divided into four major groups: cervical, thoracic, lumbar, and sacral. This segmented organization of the spinal cord matches
the segmented organization of the skin from which the signals are carried.
What is dermatome?
All the skin that is innervated by one level or segment of the spinal cord.
what dose the latin word fugit mean?
fleeing
true or false? the retinofugal Pathway delivers to multipe areas of the brain stem
True
after the bundle of nerves cross they are part of __________.
optic trac
true or false are there general cells for detecting fine detail and color?
False they are specialized cells
what direction is the image facing when it enters the human eye?
upside down and backwards
free nerve intercept what type of info? (skin receptors)
pain
merkel disk endings intercept what type of info?
Perception of shape, texture
Meissner’s corpuscle endings intercept what type of info?
motion detection, grip control
Ruffini endings intercept what type of info?
Skin stretch, tangential force
Pacinian corpuscle endings intercept what type of info?
Perception of vibrations
the Cervical is in charge of ________ are of the body.
arms and collar bone area
the theoracic is in charge of ________ are of the body.
the torso and inner arms
the lumbar is in charge of ________ are of the body.
legs and feet
the Sacaral is in charge of ________ are of the body.
crotch and outer area of feet
what is nociception?
which is the neural processing of injurious stimuli in response to tissue damage.
