Unit 2: CNS Sensory Flashcards
what does structure determine
function
what symmetry do humans have
bilateral
organization of the nervous system
anterior or rostral
front part of a structure
posterior or caudal
back part of a structure
dorsal
pointing out of the back
ventral
pointing towards the ground
lateral
towards the side
medial
towards the middle
ipsilateral
same side of the body
contralateral
opposite side of the body
horizontal
a slice parallel to the ground
coronal (transverse)
a slice vertical from front to back
sagittal
- a slice perpendicular to the ground
- parallel to the neuraxis
hindbrain parts
- myelencephalon
- metencephalon
myelencephalon
- contains medulla oblongata
- contains nuclei that control vital functions (breathing and skeletal muscle tone)
metencephalon
- the cerebellum: receives information from sensory systems, muscles, and vestibular system; produce smooth movement
- pons: a large bulge on the brain stem involved in sleep and arousal
mesencephalon
- one of the 3 divisions of the brainstem
- basic physiological function (breathing, swallowing, heart beat)
- gates sensory and motor information
red nucleus
coordinates sensorimotor information
substantia nigra
cells make dopamine and project to basal ganglia
periaqueductal grey matter
involved in pain suppression due to high concentration of endorphins
forebrain parts
- diencephalon
- telencephalon (cerebrum)
diencephalon
- thalamus: interconnected nuclei receive information from the sensory systems (except olfactory) and relay information to sensory processing area in the cortex; learning and memory; slow sleep waves generated
- hypothalamus: 22 nuclei and pituitary gland, control the ANS and endocrine system; key aspects of behavior (feeding, sex, sleep, temp. regulation, emotional behavior)
telencephalon
- hemispheres separated by the longitudinal fissure
- hemispheres connected by the corpus callosum
- grey matter and white matter
how much of the cerebrum is hidden in the gyri and sulci
2/3
spinal cord function
- neuronal link between PNS and brain
- spinal reflex integration center
how many pairs of spinal nerves are there
31
dorsal root meaning
afferent sensory
ventral root mening
efferent motor
phrenology definition
- skull mimicks personality
- larger brain area (ex. forehead) indicates a greater tendency toward the faculty of that area
- not valid as a scientific theory
- first time a specific function was associated with a specific brain region
electrical stimulation
- Luigi Rolando (1809)
- provided proof that the CNS was electrically excitable and that brain functions are anatomically localized
case of Phineas Gage
- spike went through his skull
- profound personality changes after the accident
- personality improvement in Chile (using social and complex cognitive-motor skills)
case of Patient Tan
- diagnosed with epilepsy early in childhood
- admitted to hospital at 21, could only say “tan” twice in a row
- broca coined this disorder aphasia
- good comprehension
- broca reported softening in what would become known as broca’s area in a brain examination postmortem
who coined the term aphasia
paul broca
aphasi
absence of overt speech
paul broca patients
- patient tan
- patient lelong
case of patient lelong
- reduced productive speech at 84 after a stroke
- could only say 5 words (oui, non, tois, toujours, and lelo)
- lelong had a lesion in the same region as patient tan
broca’s area
the frontal lobe of the dominant sphere (left for most of righthanded people and half of left handed people)
who first described receptive aphasia
carl wernicke
receptive aphasia
- impaired comprehension of their own speech
- don’t realize their errors
- associated with stroke, trauma, tumor, infections, and degenerative brain disorders
wernicke’s area
a region of superior temporal gyrus in the dominant cerebral hemisphere
types of aphasia
- broca’s aphasia
- wernicke’s aphasia
- conduction aphasia
broca’s aphasia
difficulty in production of language
receptive aphasia
difficulty in comprehension of language
conduction aphasia
- due to damage of arcuate fasciculus
- patients are aware of their mistakes and try to fix them
arcuate fasciculus
the bundle of axons that connect broca’s area to wernicke’s area
case of patient h.m.
- hit his head while biking
- intractable epilepsy after the accident (blocking out often, convulsions, could no longer work)
- dr. scoville removed two finger-shaped slivers of tissue from his brain (anterior 2/3 of hippocampi, parahippocampal cortices, entorhinal cortices, piriform cortices, and amygdala)
- seizers stopped but developed severe anterograde amnesia (short term memory intact, no new long-term memories) and retrograde amnesia (could not remember events from 3-4 days before surgery and some events up to 11 years before)
- ability to form long-term procedural memories was intact (could learn new motor skills but not remember learning them)
unit of structure of the CNS
neurons
neuron - cell membrane
neuron - dendrites
neuron - cell body (soma)
neuron - axon
neuron - axon hillock
neuron - myelin sheath
neuron - node of ranvier
neuron - synaptic end bulbs
neuron - axon terminal
pre- and postsynaptic neurons - presynaptic neuron
pre- and postsynaptic neurons - neurotransmitters
pre- and postsynaptic neurons - receptors
pre- and postsynaptic neurons - postsynaptic neuron
pre- and postsynaptic neurons - synaptic cleft
pre- and postsynaptic neurons - synaptic vesicles
pre- and postsynaptic neurons - axon terminal
action potential
electrical signals sent over a long distance
a plasma membrane is a ________________ ______________ that is composed of:
- phospholipid bilayer
- phospholipids
- glycolipids
- cholesterol
- membrane protein
plasma membrane - extracellular matrix fibers
plasma membrane - glycoproteins
plasma membrane - carbohydrates
plasma membrane - glycolipid
plasma membrane - cytoplasm
plasma membrane - proteins
plasma membrane - cholesterol
plasma membrane - phospholipid
plasma membrane - cytoskeleton microfilaments
plasma membrane - intercellular space
phospholipid - hydrophobic tail
phospholipid - hydrophilic head
is the plasma membrane highly permeable?
no, it is selectively permeable
what do plasma membranes allow directly through
- gas (COs, O2, N2, etc.)
- small uncharged polar molecules (ethanol, etc.)
what do plasma membranes sometimes allow directly through
water (only in specific conditions)
what plasma membranes never allow directly through
- ions (K+, Ca2+, etc.)
- charged polar molecules (amino acids, ATP, etc.)
how do ions and charged polar molecules go across a plasma membrane
- simple diffusion
- facilitated diffusion (protein-mediated)
- active transport
which channel/carrier proteins are passive and which require energy
passive:
- facilitated diffusion
energy:
- active transport
passive transport
down concentration gradient
why does active transport require energy
it goes against the concentration gradient
electrochemical gradient
combination of concentration and charge differences across the membrane
facilitated diffusion
passive, down gradient using a protein channel or carrier
channel proteins
selective pore
carrier proteins
bind solutes tightly, undergo conformational changes
which transport maintains chemical imbalance necessary for life
active transport
charge (Q)
net imbalance in the number of positively and negatively charged particles
current (I)
- flow of electrically charged particles
- charged particles = ions
voltage (V)
- difference in charge between inside and outside of the cell
- represents an electrical potential energy gradient down which particles want to move
electrical gradient
- influenced by the overall electrical charge
- positive ions would flow toward negative charge
chemical gradient
- influenced by the individual concentration of a particular ion
- all ions move from high to low concentration
the direction that an ion moves depends on:
- overall net effect of electrical and chemical (electrochemical) gradients
- membrane permeability to ions (no channels = no movement)
how is the electrochemical gradient maintained
Na+-K+ pump
Na+-K+ pump
- maintains Na+ and K+ gradients across the plasma membrane
- abundant
- P-type transport ATPase
- phosphorylation changes the conformation of the pump, exposing binding side on the extracellular membrane
- ionic imbalance
ionic imbalance importance
- intracellular pH control
- osmotic control
- transport
- excitability
how much of a cell’s energy foes to powering the Na+-K+ pump
1/3
Na+-K+ pump step 1
binding cytoplasmic Na+ stimulates ATP
Na+-K+ pump step 2
phosphorylation causes conformational change
Na+-K+ pump step 3
Na+ is liberated outside and K+ binding sites are exposed inside
Na+-K+ pump step 4
binding K+ triggers the release of the phosphate
Na+-K+ pump step 5
release of phosphate restores original conformation
Na+-K+ pump step 6
K+ is released and Na+ binding sites are exposed in the cytoplasm
equilibrium potential
the electrical potential difference that exactly counterbalances diffusion due to the concentration difference
nernst equation
- electrical potential required to oppose the movement of an ion across a permeable membrane
- provides a measure of the chemical driving potential established by the concentration gradient for ion
gating definition
transition between conducting and non-conducting (open and closed) states of an ion channel
goldman equation
- defines membrane potential
- accounts for relative permeability of the ions
which axon was used to determine resting membrane potentials
squid giant axon
absolute refractory period
- a period of complete resistance to stimulation
- Na+ channel inactivation means after an action potential there is a brief period when no other action potentials can be generated
relative refractory period
- a period of partial resistance to stimulation
- lasts as long as K channels are open
- strong stimulus can trigger a new action potential
contiguous conduction
conduction of action potentials in unmyelinated axons
conduction speed definition
nerve impulse speed
conduction speed number
nerve impulse travels 1 meter in 0.1 seconds
c fibers job
carry sensory information
are c fibers myelinated
no
c fiber damage causes what
neuropathic pain
axon potential propagation speed depends on ….
how local currents spread
how local currents spread in axon potential propagation speed depends on
- internal resistance of the axon
- resistance of the axonal membrane
do narrow axons have high or low internal resistance
high
to get a faster axon potential propagation speed the axon could be ….
- wider
- myelinated to increase membrane resistance
myelin
a membrane component from glial cells that surrounds and insulates consecutive axon segments
saltatory conduction
the way an electrical impulse skips from node to node down the full length of an axon, speeding the arrival of the impulse at the nerve terminal
myelinated fibers in the PNS
schwann cells
myelinated fibers in the CNS
oligodendrocytes
consequence of demyelination
multiple sclerosis (MS)
multiple sclerosis
- autoimmune disease
- myelin sheath degenerates and forms hardened scars
- affected axons degenerate
- slowing and block of AP conduction
multiple sclerosis risk factors
- age (20-40 years old)
- sex (women)
- family history
- certain infections (Epstein-Barr infection aka mono)
- race (white)
- temperate climate
- vitamin d deficiency
- other autoimmune diseases (thyroid disease, psoriasis, type 1 disease)
- smoking
peripheral nervous system function
- sensory systems: detect external and internal stimuli
- higher brain regions: process and integrate different information and make decisions
- motor systems: execute decisions
pns
fibers (other than brain and spinal cord) that carry information between CNS and other body parts
PNS divisions
- afferent division
- efferent division
PNS types of afferent divisions
- visceral afferent
- sensory afferent
PNS afferent division
send information from internal and external environment to CNS
PNS visceral afferent
incoming information from internal viscera
PNS sensory afferent
- somatic: sensation from body surface and proprioception
- special senses: vision, hearing, smell, taste
PNS efferent division
send information from the CNS to muscles and glands
perception
conscious interpretation of external world derived from sensory input
does pure sensory input give true reality perception
no
why does pure sensory input not give true reality perception
- human receptors only detect a limited number of stimuli
- limited resolution (information channels are not high-fidelity records)
- information can be enhanced/suppressed when it reaches our brain
- brain interprets and distors information to extract conclusions
- interpretation affected by cultural, social, and personal experiences
stimulus
a change detectable by the body
different modalities of stimuli
heat, light, sound, etc.
stimulus receptors
structures at peripheral endings of afferent neurons
receptors function
convert stimuli into electrical signals
stimulus sequence
sensory system parts
sensory receptors, their axonal pathways, and perception target areas in the brain
modalities
different classes
specialized sensory receptors detect ….
different stimuli classes
exteroceptors
specialized neurons on the outside of the body
interoceptors
specialized neurons on the inside of the body
exteroceptors/interoceptors function
transduction
transduction
the process of converting energy from a stimulus into electrical signals via receptor/generator potential which triggers an action potential if thresholds are reached
photoreceptors sense and stimulus
- vision
- light
mechanoreceptors sense and stimulus
- touch, balance, proprioception, hearing
- mechanical energy (stretching muscle, hair cell movement)
thermoreceptors sense and stimulus
- temperature
- heat and cold
chemoreceptors sense and stimulus
- smell, taste
- specific chemicals (O2, etc.)
nociceptors sense and stimulus
- pain
- excessive pressure, temperature, specific chemicals
where do primary afferent axons enter
the spinal cord through the dorsal roots
where do primary afferent axon somas remain
spinal cord dorsal root ganglia
nerve fiber types
- Aα
- Aβ
- Aδ
- C
efferent motor nerve fibers
- Aγ
- B
which nerve fiber do skin receptors lack
Aα
are C fibers myelinated or unmyelinated
unmyelinated
nerve fiber axon diameter
bigger diameter = lower resistance
unmyelinated voltage regulated channels function
- account for ion leakage across the membrane
- conduct impulses slowly
where is there ion leakage in myelinated axons
Nodes of Ranvier
where is graded potential generated
in a receptor cell or free nerve ending
graded potential is proportional to …
stimulus strength
action potential is ….
all or nothing
receptor cell
free nerve ending
stimulus intensity is encoded in …
- actional potential frequency
- the number of activated receptors
single sensory unit stimulation weak versus strong simulus
multiple sensory unit stimulation weak versus strong stimulus
receptor potential
- occur in seperate receptor cells
- stimulus opens ion channels causing graded membrane potential
- receptor cell releases chemical messenger
- chemical messenger opens ion channels in afferent neuron action potential
- if threshold is reached, actional potential is generated
generator potential
- occur in specialized nerve endings
- stimulus opens ions channels causing local current flow
- local current flow opens ion channels in afferent neuron action potential
- if threshold reached, action potential is generated
receptive field
a region of space in which the presence of a stimulus alters the firing of that neuron
receptive field example
- hair in the cochlea
- skin
- retina
size and shape of receptive fields may change due to …
- connectivity (convergence, divergence, inhibition)
- synaptic properties
receptor transduction necessary components
- receptor must have specificity for the stimulus energy
- receptive field stimulation
- stimulus energy converted into a graded potential
- generator potential in the associated sensory neuron must reach threshold
adaptation
a change in sensitivity in the receptor cell to a long-lasting stimulus
types of adaptation
- PHASIC
- TONIC
PHASIC
- primarily by rapidly-adapting receptors
- pressure, touch, hearing, smell
- adapt quickly, respond less if stimuli remains constant
- allows us to shut out background noise
TONIC
- little adaptation by slowly adapating receptors
- pain, proprioception, chemicals in the blood or CSF
- adapt slowly, continue to respond even when stimulus remains constant
why is continuous input in TONIC useful
body needs to make sontinuous response to the information or the stimulus needs to be constantly evaluated
types of adaptational receptors
- proprortional receptors
- differential receptors
proportional receptors
provide continuous information about stimulus
differential receptors
signals changes in stimulus intensity
adaptation mechanisms types
- mechanical
- chemical
mechanical adaptation mechanisms
physical mechanical mechanism induces a receptor neuron response decrease
where are specialized receptor endings for mechanial adaptation mechanisms
in Pacinian skin cells
chemical adaptational
membrane enzymes or intracellular signalling mechanisms induce response termination
where is chemical adaptation mechanism common
olfactory response
phasic receptors of mechanical adaptation
- specialized receptor ending of concentric connective tissue layers
- sustained pressure causes layers to slip which dissipates stimulus intensity
phasic receptors of chemical adaptation
adaptation mediated by Ca2+:
- Ca2+ binding calmodulin decreases CNGC activity
- Ca2+ regulates AC III activity decreases cAMP
somatosensory system
neural sense concerned with body sensations
soma
greek word for body
somatosensory system divisions
- cutaneous (skin)
- visceral (internal organs and deep tissue)
- proprioception (body and limb awareness)
are somatosensory receptors distributed or concentrated
distributed
different somatosensory receptors respond to …
different stimuli modalities
touch begins at ….
the skin
layers of the skin
- epidermis (outer)
- dermis (inner)
glabrous definition
skin free from hair (palm of hands, soles of feet, face, and ears)
which receptor is most common in relation to touch
mechanoreceptors
somatosensory receptors
- meissner’s corpuscle
- merkel disc receptors
- ruffini ending
- pacinian corpuscle
- bare nerve endings
somatosensory receptors - meissner’s corpuscle
- respond to touch
- fine and discriminative touch in glabrous skin
somatosensory receptors - merkel disc receptors
fiber connected to an epithelial cell
somatosensory receptors - ruffini ending
slowly adapting touch receptor
somatosensory receptors = pacinian corpuscle
- rapidly adapting
- vibration sensor
somatosensory receptors - bare nerve endings
pain and hear stimulation
if a sensory neuron supplies a large area then …
touch discrimination will not be as fine
where are receptive fields identified
neurons of the autitory, somatosensory, and visual systems
more ? is dedicated to integrate information coming from the fingertips
brain tissue
somatosensory ascendant pathways
- 3rd order afferent
- 2nd order afferent
- 1st order afferent (primary sensory neuron)
3rd order afferent
- in thalamus
- project to primary somatosensory cortex
2nd order afferent
- in spinal cord
- synpase with 3rd order in thalamus
1st order afferent (primary sensory neuron)
- soma in peripheral sensory ganglion
- peripheral axon branch innervates receptors
- central axon synapses with 2nd order afferent neuron
dorsal column-medial lemniscal pathway carries information about …
- fine touch
- vibration (ex: hand moving over surface)
- stimuli moving on skin
dorsal column-medial lemniscal pathway
where does information from the dorsal column-medial lemniscal pathway decussate
the medulla
is the dorsal column-medial lemniscal pathway ipsilateral or contralateral
contralateral (left side of body to right cortex, and vice versa)
lateral inhibition function
highlight edges of stimulus (contrast enhancement)
lateral inhibition
a neuron’s response to a stimulus is inhibited by the excitation of a neighboring neuron
between two neurons which response will be inhibited
the weaker one
where is lateral inhibition common
vision and hearing
why is lateral inhibition good
enhances perception
in lateral inhibition, primary neuron response is _________________ to the stimulus strength
proportional
where does most somatosensory information get processed
primary somatosensory cortex
where is the primary somatosensory cortex located
parietal lobe
primary somatosensory cortex recieves inputs from….
ventral pallidum thalamic area
how responsive are neurons in primary somatosensory cortex to somatosensory stimuli
very
lesions in primary somatosensory cortex …
impair somatic sensation
what happens when primary somatosensory cortex is electrically stimulated
evokes somatosensory experiences
somatotopic representation
representation of body mapped on the cortical surface
homunculus
- distorted map
- hands, fingers, and face receive greatest representation
phantom limb syndrome
ascending pathways stimulate primary somatosensory cortex from adjacent representation but descendent pathways interpret incorrectly
why do somatosensory cortexes reorganize
- basis of experience
- somatosensory input
posterior parietal cortex function
different sensory modality traits converge for proper sensory representation
agnosia
inability to recognize an object even though simple sensory skills are normal
consequence of posterior parietal lesions
spatial neglect
spatial neglect
- ignore contralateral extrapersonal space
- deny body parts (incomplete dressing)
- incomplete copyings of drawing
- body centered (memory recall depends on view point)
is spatial neglect a simple sensory loss? explain
no, concerned with representing visual and somatosensory space and actions within it
pain
an unpleasant sensory or emotional experience associated with actual or potential tissue damage
nociception
processing information about damaging stimuli by the nervous system where perception occurs
nociceptors
free nerve endings found in every tissue in the body except the brain
when are nociceptors activated
- in the presence of intense thermal, mechanical, or chemical stimuli
- tissue irritation or injury (releases chemicals that stimulate nociceptors)
which fibers are connected to nociceptors
c fibers
spinothalamic pathway
steps of vision
- transmission and refraction of light by optics of the eye
- transduction of light energy into electrical signals by photoreceptors
- signal refinement by synaptic interactions within retinal neural connections
visual processing path
wavelength
the distance between two peaks of the electromagnetics wave
rainbow effect
when white light diffracts through a prism it splits into a rainbow
what does a mix of visual light wavelengths usually appear as
white light
properties of visual light
- reflection
- refraction
- absorption
visual light property - reflection
light bouncing off of a surface
visual light property - refraction
- light rays bending when traveling
- the eye acts as a camera bending the light to focus it in the retina
visual light property - absorption
- transfer of light energy to a particle
- photoreceptors in the retina contain pigments that absorb light reflected by objects
- black objects absorb all the visual light wavelengths, green absorb all except green, etc.
frontal eye anatomy - macula
frontal eye anatomy - fovea
frontal eye anatomy - temporal retina (lateral)
frontal eye anatomy - nasal retina (medial)
frontal eye anatomy - optic disk
frontal eye anatomy - blood vessels
lateral eye anatomy - suspensory ligament
lateral eye anatomy - ciliary body
lateral eye anatomy - conjunctiva
lateral eye anatomy - lens
lateral eye anatomy - pupil
lateral eye anatomy - aqueous humour
lateral eye anatomy - cornea
lateral eye anatomy - iris
lateral eye anatomy - vitreous humor
lateral eye anatomy - blood vessels
lateral eye anatomy - optic disc
lateral eye anatomy - optic nerve
lateral eye anatomy - fovea
lateral eye anatomy - sclera
lateral eye anatomy - retina
lateral eye anatomy - choroid
lateral eye anatomy - extrinsic eye muscle
cornea and lens optic function
diffract light (refraction) to focus it in the retina
the lens will accommodate to different ____________
distances
retina
a layer of photoreceptors cells and glial cells that captures incoming photons and transmits them along neuronal pathways as both electrical and chemical signals for the brain to perceive a visual picture
which nervous system is the retina a part of
CNS
most direct pathway from the retina to the brain
photoreceptors -> bipolar cells -> ganglion cells
which cells are the only ones that generate action potentials
ganglion cells
the only light-sensitive cells
photoreceptors
retina output
ganglion cell axons in the optic nerve that lead to higher CNS centers
laminar organization definition
the way certain tissues are arranged in layers
retina laminar organization
retina interneurons
horizontal and amacrine cells
horizontal cell function
modulate transmission from photoreceptors to bipolar cells
amacrine cell function
modulate transmission from bipolar cells to ganglion cells
photoreceptors
transform electromagnetic radiation into electrical signals
photoreceptor types
- rods
- cones
rods
- night vision
- one photopigment
- black/white vision
- many membrane disks
- low spatial resolution but very sensitive to light
cones
- daylight vision
- 3 photopigments
- color vision
- high spatial resolution but insensitive to light
- does not operate in dim light
fovea has ____ cones than rods
more
periphery has ____ cones than rods
less
central retina cell composition
individual photoreceptors feeding into individual ganglion cells
periphery cell composition
many photoreceptors converge into individual ganglion cells
periphery
- more rods and greater input
- higher sensitivity
- larger receptor fields
- lower resolution
why is there lower sensitivity in the fovea
- more cones and no convergence of input
- one photoreceptor into one ganglion cell
why is there higher resolution in the fovea
- no convergence of input
- one photoreceptor into one ganglion cell
- direct light input
which photopigment is in rods
rhodopsin
what do cone photopigments require to be activated
more energy
3 cone types
- red
- blue
- green
how many types of light is each cone sensitive to
one
result of all cones being equally active
white light
which photopigment is in cones
opsins
total number of cones in the eyes
6 million
total number of rods in the eyes
100 million
phototransduction
conversion of light energy into membrane potential changes
result of graded changes in membrane potentials
change in transmitter release rate
phototransduction in the dark
- membrane depolarization
- Ca2+ channels open
- high transmitter release rate
phototransduction in the light
- membrane hyperpolarization
- Ca2+ channels close
- decreased transmitter release rate
photoreceptor depolarization cause
dark (“current of Na+”)
photoreceptor depolarization process
- guanylyl cyclase produces cGMP in the dark
- cGMP binds and activates Na+ channels
- Na+ influx depolarizes the membrane
- membrane depolarization induces Glutamate liberation
photoreceptors hyperpolarization cause
light
photoreceptors hyperpolarization process
- absorption of light induces retinal cis isomer to become a trans isomer
- conformational change and transduction
- light activates rhodopsin and transducin
- transducin binding GTP activates PDE
- active PDE breaks down cGMP
- low levels of cGMP promote channel closing
- Na+ influx decreases, membrane hyperpolarizes
- hyperpolarization reduces glutamate release
what provides the isomers in photoreceptor polarization with conformational changes (trans to cis or cis to trans)
pigmented epithelium
rhodopsin components
opsin + retinal
transducin
a G protein
what polarizes bipolar cells
glutamate
bipolar cell types
- on center
- off center
on center bipolar cells are ________________________ by glutamate
hyperpolarized
off center bipolar cells are ________________________ by glutamate
depolarized
on center bipolar cells are ________________________ by light
depolarized
off center bipolar cells are ________________________ by light
hyperpolarized
on center bipolar cells
0 bound to glutamate during dark
- mGluR6 closes Na+ channels
- hyperpolarization reduces glutamate release, reduces mGluR6 binding, and allows Na+ channels to open
off center bipolar cells
AMPA/Kainate R expression
bipolar cell receptive field
area of retina where a stimulus will evoke a response
bipolar cell receptive field center
direct connect from photoreceptors
bipolar cell receptive field surround
connection from photoreceptors through horizontal cells
bipolar cell receptive field rule
whatever response is triggered in the center, the opposite will be triggered by the surround
ganglion cell receptive field
the area of a retina where a stimulus will evoke a response in that ganglion cell
ganglion cell receptive field rule
light in the center will have the opposite effect than light in the surround
ganglion cell types
- on center
- off center
on center ganglion cells
produce action potentials when light is shone on the receptive field center
off center ganglion cells
decrease action potentials when light is shone on the receptive field center
photoreceptors are always hyperpolarized by _______ but …. ?
- light
- action potential firing in the ganglion cell may increase or decrease
is the change in firing rate extremely high or low if receptive field center and surround are in the same illumination
there is no change (A,C, and E)
is the change in firing rate extremely high or low if receptive field center and surround are in the contrast
greatest difference (B and E)
antagonistic center/surround effect mediated by horizontal cells
- reduced hyperpolarization of center cone
- increased release of glutamate from center cone
- hyperpolarization of bipolar cell
- hyperpolarization and reduced firing of ganglion cell
what do horizontal cells regulate
the amount of transmitter released by photoreceptor onto bipolar cell
horizontal cell hyperpolarization
surround cone releases less glutamate onto horizontal cell
ganglion cell response reflect …
differences in contrast
vision neural level process
- light energy converted to membrane potential changes. in photoreceptor cells through opsin -> transducin -> PDE -> CNG Channel -> Glutamate
- glutamate information converted into membrane potential changes in bipolar (center on/off) and horizontal (surround on/off) cells
- processed information converted into action potentials. in ganglion cells
- transmitted to the brain via the optic nerve
systems of the ear
- auditory
- vestibular
vestibular system
- balance
- inform the brain of head and body position and how they are moving
auditory system
- hearing
- detect sounds, localize, and identify sound nuances
types of air that compose sound
- compressed air
- rarefied air
frequency unit and equation
cycles/second (Hz)
sound features
- pitch
- intensity
- timbre
pitch
- tone
- dependent on frequency
intensity
- loudness
- depends on amplitude
timbre
- quality
- depends on overtones
sound amplitude
decibels (dB)
auditory threshold
0 dB
speech freqeuncies
500-4000 Hz
auditory thershold varies with …
frequency
what do low and high frequencies require to be audible
higher sound levels
what sounds can humans not hear and give examples
- infra sound (whales, muscles moving)
- ultra sound (bats)
auditory system process
3 main parts of the ear
- outer ear
- middle ear
- inner ear
outer ear features
- pinna (auricle)
- auditory canal
ear - pinna
ear - auditory canal
middle ear features
- ossicles: malleus, incus, stapes
- tympanic membrane
ear - ossicles
ear - tympanic membrane
inner ear features
- labyrinth/semicircular canals
- oval window
- round window
- auditory-vestibular nerve
- cochlea
ear - labyrinth/semicircular canals
ear - oval window
ear - round window
ear - auditory-vestibular nerve
ear - cochlea
auditory system pathway
- cochlea
- brainstem
- thalamus
- primary auditory cortex
middle ear amplification features
- malleus
- incus
- stapes
- oval window
- cochlea
- eustachian tube
- tympanic membrane
- auditory canal
oval window pressure </> tympanic membrane pressure
>
pressure equation
force/surface
middle ear - malleus
middle ear - incus
middle ear - stapes
middle ear - eustachian tube
what connects the malleus to the skull
tensor tympani muscle
what connects the stapes to the skull
stapedius muscle
attenuation reflex
- after a loud sound, tensor tympani muscle and stapedius muscle tense, impairing amplification system
- protective reflex
- adaptation to loud sounds
- not hearing our own speech
ear - tensor tympani muscle
ear - stapedius muscle
cochlea features
- bony cochlear wall
- scala vestibuli
- scala media
- tectorial membrane
- basilar membrane
- scala tympani
- spiral ganglion
- vestibular membrane
- organ of corti
- cochlear branch of vestibulocochlear nerve
(transverse section) cochlea - bony cochlear wall
(transverse section) cochlea - scala vestibuli
(transverse section) cochlea - scala media
(transverse section) cochlea - tectorial membrane
(transverse section) cochlea - basilar membrane
(transverse section) cochlea - scala tympani
(transverse section) cochlea - spiral ganglion
(transverse section) cochlea - cochlear branch of vestibulocochlear nerve
(transverse section) cochlea - organ of corti
(transverse section) cochlea - vestibular membrane
(coronal section) cochlea - oval window
(coronal section) cochlea - round window
(coronal section) cochlea - tectorial membrane
(coronal section) cochlea - basilar membrane
(coronal section) cochlea - organ of corti
(coronal section) cochlea - cilia
(coronal section) cochlea - auditory nerves
(coronal section) cochlea - perilymph
(coronal section) cochlea - endolymph
where do the scala vestibuli and scala tympani communicate
the apex of the cocohlea
where does the perilymph flow
from vestibuli to tympani when stapes taps the oval window
where does the endolymph flow
inside the scala media
where is the basilar membrane widest and most flexible
the apex
are individual frequencies detected by the same parts of the cochlea
no
where in the cochlea are high frequencies detected
near oval window (stiff)
where in the cochlea are low frequencies detected
near apex wide (flexible)
organ of corti parts
- outer hair cell
- stereocilia
- tectorial membrane
- reticular lamina
- modiolus
- spiral ganglion
- auditory nerve
- inner hair cell
- rods of corti
- basilar membrane
organ of corti - outer hair cell
organ of corti - stereocilia
organ of corti - tectorial membrane
organ of corti - reticular lamina
organ of corti - modiolus
organ of corti - spiral ganglion
organ of corti - auditory nerve
organ of corti - inner hair cell
organ of corti - rods of corti
organ of corti - basilar membrane
inner ear transduction process
- upward displacement of basilar membrane creates force that laterally
displaces stereocilia - mechanical displacement of the stereocilia in a lateral direction cause hair cell depolarization
- downward displacement of the basilar membrane creates force that results in
lateral displacement of the stereocilia in the opposite direction (hyperpolarization of the
hair cell)