Review 13 Flashcards
Eye Notes
- When in water, light becomes lurry.
- It is much curved than normal becasue of water replacing air
- Goggles give extra layerr to allow correct bending of light
Iris
- Part of eye that is colored.
2. Contract or expand a hole called pupil
Pupil
- Hoel controlled by iris
2. Bright - constricts and dark - expands
Vitreous Humor
- Light from pupil enters vireous humor
- Entering the posterior part of the eye
- Water, salt and protein (albumin)
- Suspends lens in place and protects the eye and prevents it from collapsing on itself
- transparent
Retina
- Coats entire back of eyeball
- Contain bunch of cells (collectively called photoreceptors) that convert light to neural impulses for brain
- Coated red
a. Camera eye flash can cause red-eye effect
b. 1st flash constricts pupil and 2nd flash takes image
c. Reduces red eye effect - Sends fibers at back of brain forming optic nerves and makes sense of it.
Choroid
- Network of blood vessels that nourish retina and cells of the eye
- Pigmented black and can absorb light not getting to the retina.
- Cats lack choroid and it is shiny and helps with night vision because it can reflect light onto the retina.
- Contains dimple filled with cones that are center of the macula and it is collectively called fovea and helps with detailed image.
Rod and Cones
- Photoreceptors
- Take and convert light to neural impulse
Rod:
a. 120 million
b. Found on periphery of retina
c. Great for night vision
d. Sensitive to light
e. Protein = rhodopsin
f. Slow recovery time
Cones:
a. 6-7 million
b. Color vision
c. Has red (60 %), green (30%), and blue (10%) cones
d. Centered in the fovea and retina
e. Fast recovery time
Phototransduction Cascade Summary involving Rod
Light shines -> Rod (normally turned on) turns off -> Bipolar cell turns on -> Retinal Ganglion cell turns on -> Optic nerve -> Brain
Process of Phototransduction Cascade
- Rods contain rhodopsin.
- Small molecule contained within the rhodopsin called retinal. When it is bent normally, it is called 11-cis retinal and when light shines, it becomes 11-trans retinal.
- This causes rhodopsin to change shape and begins a large cascade of events.
- Molecule called transducin (with alpha, beta, and gamma subunit) breaks away from rhodopsin
- alpha subunit binds to phosphodiesterase (PDE)
- PDE takes cyclic GMP to normal GMP
- This closes Na+ channel that are normally opened by cyclic GMP.
- Cell becomes hyperpolarized and rod turns off
- Bioplar cell has on-center and off-center. Off-center is turned on when retina is turned on and that makes the bipolar cell off but light turns off rod and turns on-center ona nd makes the cell turned on.
- Activates retinal ganglion cell
- Sends optic nerve to the brain.
LOOK AT AND DRAW A SUPERIMPOSED GRAPH OF RODS AND CONES
- Y -axis = receptor density
2. X axis has periphery and fovea and do not forget the blind spot.
How do nasal, optic nerve and chiasm, and temporal affect visual field processing?
Optic nerve converges and break away at the back of the ey called optic chiasm. Rays of light that land on retina on the temporal side do not cross to the other side of the brain but those that fall on the nasal side cross at the optic chiasm.
Feature detection and Parallel processing
Use of combination or breakdown of color, form, and motion to make sense of an image
The ability to experience the above three at the same time occurring without distinction is called parallel processing.
Color
- Ability is due to cones.
2. Use of red, green, and blue cones called Trichromatic theory of color vision
Form (Shape and Boundary)
- PARVO pathway
- Figures shape of object and details of objects when stationary
- Good spatial resolution
- Allows to see color stationary
- Poor temporal (motion) resolution
Motion
- MAGNO pathway
- Poor spatial resolution
- Good temporal resolution
- Does not encode colors
- When stationary, use PARVO, MAGNO will appear blurry
- When moving, use MAGNO, PARVO will appear blurry.
Hearing Important elements and Mechanism (What do they do)
- Needs pressurized sound waves and hair cells (receptors)
- Ear can breakdown two different sounds at the same time because waves travel at different lengths in the cochlear.
Mechanism or Pattern: Pinna -> Auditory canal (external auditory meatus) -> Eardrum (Tympanic membrane) -> Malleus -> Incus -> Stapes -> Elliptical or oval window -> Fluid -> Cochlear -> Round (Circular) window -> Organ of corti (basilar and tectorial membrane) -> importance of motion of fluid
Auditory Sturucture Addition
Cochlear - Imagine unfolded - Stapes, organ of corti, fluid moving - Focus on organ of corti.
Organ of corti has upper and lower membrane moved up and down by motion of fluid. Focus is on hair cells in the middle
Hair cell blown up has Sharp point called hair bundle. When this is blown up, we see various tips called kinocilia attached by tip link.
Focus is on tip link
Tip Link
- Not exactly attached to the kinocilia
- Attached to a K+ gate
- AS kinocilia is moved back and forth, it is stretched
- Opens up the K+ gate which is outside flows into the cell.
- Ca2+ also flows becasue K+ makes its channels open
- Flow causes action potential to occur
- Activates spinal ganglion cell
- Cell stimulates another auditoru nerve that goes straight into he brain.
Auditory Processing
- Unroll cochlear to form base and apex (closer to inner cochlear). They are from high frequency to lower frequency.
- Sounds travel allong the cochlear and basilar tuning allows differentiation of sounds on frequency
- Mapping of sounds with lower or higher frequency on cochlear membrane is called tonotypical mapping.
Process:
- Sound gets into ear
- Sound travels through the cochlear and activates specific cells based on frequency.
- Cells activate and form auditory nerve to the brain.
- Brain ahs pimary auditory cortex and secondary auditory cortex.
- Prinary auditory cortex also has mapping of frequencies and receives all information from the cochlear.
Sensorineural Hearing loss and Cochlear implants
The condition has impaired ability to convert sound waves in auditory nerve to brain in a problem of CONDUCTION where cochlear implant tries to help.
Cochlear implants: Stimulator, receiver, transmitter, speech processor, and microphone.
Microphone gets sound and converts to electrical impulse through the speech processor. Speech processor gets information to the transmitter that sends it to the receiver which gives it to the stimulator that helps send to the cochlear and bolsters it.
Adaptation vs. Amplification
Adaptation - Downregulation. Change over time and responsiveness of sensory receptor to a constant stimulus e.g resting the hand on table.
Amplification - Upregulation. Ray of light or pain receptor can cause amplification of cells. Over-amplification can be bad that is, it can kill cells.
Somatosensory Homunculus
- Map of the body in the brain influential in mapping sensory information.
- particular part is the sensory strip in the middle of the cortex:
a. Informtion from all the body hits sensory strip and sent to the particular sensory strip specific for the location on the body.
b. Helpful to neurosurgeons.
How can we see or walk in a dark room
Proprioception and Kinesthesia
Proprioception
- Sense of position
- Subconscious and cognitive
- Originates from tiny sensors in parts of the body and muscle.
a. Called spindle with protein inside so when muscle stretches or contracts it does the same thing and sends it to the CNS. - Concerned with balance
Kinesthesia
- Movement focused
- Behavioral e.g. golf, baseball, etc.
- Not concerned with balance
Pain and Temperature Sensation and Response
Follow the same pathway.
Temperature - Thermoception - TrpV1 receptor - From molecules relased when cells are made to burst
Pain - Nociception - TrpV1 - through molecules like CAPSACIN on TrpV1
TrpV1 changes conformation in response to stimulus
Nerves attached to the TrpV1
- Fast:
a. Large axon
b. Myelinated
c. Fibers are called A-beta
d. Combination of less resistance and more conduction allows for increased speed - Medium:
a. Smaller than fast axon diameter
b. Less myelin
c. Do not conduct as quickly as fast
d. Fibers = A-delta - Slow:
a. Small diameter
b. Unmyelinated
c. Fibers - C (characterized by lingering pain)
Nostril
Opening allows air molecules to enter the nose and to the brain
Olfactory epithelium
Projects epithelial into nasal passage to pick up molecuels to the brain
Separated from the nasal passage by CRIBIFORM PLATE
Mechanism of smelling
Odor, GPCR, G protein causes cascade of events, and this also allows binding to ion channel that opens and makes it positve and causes action potential to the brain
Glomerulus and Mitral/Tufted Cell
Glomerulus specific
Taste Senses
- Sweet - GPCR
- Bitter - GPCR
- Umami - GPCR
- Sour - Ion Channel
- Salty - Ion channel
Labelled Lines Model
Each taste bud sends their information in axons separately to specific part of the brain
NOTES: GPCR activation leads to ion channel opening that triggers AP. Also, ion channel receptor is automatically triggered once molecule binds and causes AP to occur.
How can one trick the brain?
- What happens if sweet receptor is but in salty cell? And other scenarios?
Types of Taste buds
- Fungiform - probably localized in anterior
- Foliate - Sides
- Circumvollate - back or posterior
Most taste buds are found in the front or anterior and least in the back or posterior. Each bud has all the taste buds senses.
Pheromones Intro
- Specialized olfactory cues
- Carries some sort of response in animal smelling them.
- Chemical signal by one member of a specie and is sensed by another memeber of the species and triggers a response
Importance: mating, fighting, and chemical communication.
Pheromones and Organisms
- Humans rely little on pheromones and so do not have an accessory olfactory bulb with other organisms have.
- Olfactory epithelial goes to olfactory bulb and accessory olfactory epithelial goes to accessory olfactory bulb.
Accessory Olfactory Epithelium
- Has structure called Vomeronasal system
- System as a zone with an apical cell and a basal cell which have receptors to molecules and function as GPCR
- Basal is below zone on vomeronasal system and apical is on the zone. Basal attaches to vomeronasal system through an extension
- Pathway is molecule -> sensor -> axon -> glomerulus -> mitral/tufted cell -> Amygdala
Amount in and out of cell
Inside: K+ = high Na+ = Low Cl- = Low HCO3- = Low Ca2+ = Low
Outside K+ = Low Na+ = high Cl - = high HCO3- = High Ca2+ = high
Receptors for Acetylcholine and Acetylcholine
Acetylcholine - released into neuromuscular junction, causes the post-synaptic cell to depolarize, arousal
Nicotinic - on postganglionic cells and on skeletal muscles, allow Na+ Influx.
Muscarinic - on effectors of parasympathetic nervous system, bind G protein linked receptors
GABA
Inhibitory neurotransmitter that causes Cl- to flow into post-synaptic cell
Functions in the brain
Serotonin
Produced from tryptophan, regulates mood, appetite, and sleep, dreaming
Plays a role in depression and mania. Also has some cognitive functions, including memory and learning.
Dopamine
Role in reward motivated behaviors, smooth movement and posture. schizophrenia and parkinson’s disease.
Norepinephrine
Alertness and vigilant concentration, fight or flight, role in depression and mania
Adrenergic receptors
Endorphins
Painkillers similar to morphine
NTs removal in the Synaptic cleft
a. Neurotransmitters are degraded by enzymes, ie Acetycholinesterase hydrolizes achetocholine.
b. Reuptake carriers pump back in, ie serotonin, dopamine, and norepinephrine reuptake.
c. Neurotransmitters diffuse out of synaptic cleft
Excitatory Post-Synaptic Potentials
Na+ influx, depolarize cell, and activate AP
Inhibitory Post-Synaptic Potentials
Cl- influx, hyperpolarize cell, and inhibit AP
Temporal Summation
Excitatory stimuli over time by a single neuronal stimuli occurring frequently in order to
achieve action potentials (frequency)
Spacial Summation
Excitatory stimuli by multiple neurons to achieve action potentials (number of neurons)
Threshold Potential and All or none response
Threshold potential: the minimum amount of depolarization which will cause a burst of Na + into the cell and cause an action potential
All-or-none response: the plasma membrane has to reach a threshold potential and once and only if that is reached and action potential will proceed and will always have the same magnitude.
