Chp. 10 Flashcards
Cillary muscles
Controls shape of lens to refract light in mammals and birds
A class of interneurons in the retina that receive info from rods & cones and pass them along to retinal ganglion cells
Bipolar cells
Class of cells in retina whose interneurons form optic nerve
Ganglion cells
Specialized retinal neurons that contact both the receptor cells and the bipolar cells
Horizontal cells
Uses rods, works in dim light
Scotopic system
Uses cones that permit color vision
Photopic system
Photon
A quantum of electromagnetic light in the range of wavelengths we call light
The central portion of our vision packed with the most photoreceptors and therefore the center of our gaze
fovea
Range fractionation
Cell specialize in specific ranges of light intensity
photo pigment in eye that splits into two
rhodopsin = opsin & retinal
Region of retina devoid of receptor cells because ganglion cell axons and blood vessels exit the eye ball there
optic disk
Cones vs. rods
Rods packed about 20 degrees on other side of the fovea,
Part of schotatic system.
Many rods are linked to one ganglion cell so high sensitivity but low acuity
Neurons inhibit their neighbors to enhance borders
Lateral inhibition
Part of the thalamus that receives info from the optic track and sends it to visual areas in the occipital cortex
lateral geniculate nucleus
Axons that start in the lateral geniculate nucleus and terminate in the primary visual cortex of the occipital lobe
Optic radiations
Visual cortex outside of the primary visual cortex, V2, V4 and the inferior temporal area
Extrastriate cortex
Respond best to an edge or a bar that has a particular width, edge and orientation
Simple cortical cells
A model of pattern analysis that emphasizes Fourier analysis of visual stimuli
Spatial-frequency filter model
Textures, illusionary contours
What features does area V2 respond to?
Concentric, radial stimuli and sinusoidal frequency gradings
What does area V4 respond to?
What area responds to motion
Area V5 or the medial temporal area
A region of cortex in which one eye or the other provides a greater degree of synaptic input
Ocular dominance column
A slab of visual cortex, about 0.5 mm wide, in which the neurons of all layers respond preferentially to one eye
Ocular dominance slab
The point at which two optic nerves meet
Optic Chiasm
Non-preferred stimulus
A stimulus that falls within a cell’s receptive field, but only affects its firing rate a little bit, if at al
Anti-preferred Stimulus
The stimulus that inhibits a neuron the most.
Visuotopic map
Each hemisphere of V1 contains topographic map of the contralateral hemifield
Organization of Lateral Geniculate Nucleus
Composed of six layers – ipsilateral eye: 2,3,5 – contralateral eye: 1,4,6
• Layers 1 & 2 are called “magnocellular” due to their large cell bodies
• Layers 3-6 are called “parvocellular” due to their small cell bodies
How do On-center bipolar cell function?
INHIBITED by glutamate (via a metabotropic glutamate receptor) so they become depolarized (disinhibited) when light hits the photoreceptor
How do Off-center bipolar cells function?
EXCITED by glutamate so they become hyperpolarized (less excited) when light hits the photoreceptor
How does amplitude work?
Propagation of small displacements of air molecules vs. large displacements
Equation of pitch
P = 1/frequency
Eardrum sci name
Tympanic membrane
Ossicles- names and functions
Malleus- hammer
Incus - anvil
Strapes- taps against soft membrane in the cochlea wall called the oval window
Condition where patients can perceive light and movement
They cannot verbally report if a visual object is shown, but if asked where the object is they may guess the object’s location better than expected by chance.
Cortical blindness
Unable to attend to the visual field contralateral from the lesion (e.g. ignore left side)
- Eat food only on right side of plane
- Dress/groom only one side of their body
Hemineglect
Brain regions involved in where pathway
Ventral stream
- Medial temporal area (also called v5)
- PP is the posterior parietal area (behind the primary somatosensory cortex in the parietal lobe)
Brain regions involved in what pathway
V4 is associational visual cortex lying near the border of occipital & temporal cortex
– IT is the inferior temporal cortex
Brain area that integrates sensory inputs and directed motor pathways for spatial cognition
Parietal Cortex
Term for the overall pattern of movement in the visual field
Optic flow
Types of optic flow
Translational
Radial
Rotational
Peri-Stimulus Time Histograms (PSTHs)
A peristimulustime histogram is a graph that shows how a neuron responds to a stimulus
• The x-axis of the graph is usually time, with time zero being the moment when a stimulus is turned on
• The y-axis is the response of the neuron, often measure by firing rate (spikes per unit time)
Organization of the medial temporal
MST neurons that respond to translational motion are directionally tuned
• Each MST cell prefers to respond to translational motion in one preferred direction
• Unlike V1 complex cells, MST cell have large receptive fields and respond to any moving stimulus, not just an oriented bar
• MST is topographically organized into directional columns
Face Blindness
Prosopagnosia
External ear
pinna
The ___________ transfer the force of the tympanic membrane’s vibration into vibrations of the membrane of the oval window, sending waves of vibration into the fluid that fills the cochlea
ossicles
Tympanic reflex
there are two muscles (tensor tympani and stapedius) that can damp the vibrations of the middle ear in response to loud sounds, to protect the ear from damage and adjust the gain of hearing
What is the purpose of the round window in the ear?
provides a “release valve” for increases in cochlear fluid pressure that occur when the oval window vibrates
What is the primary functional structure in the inner ear?
The bony labyrinth filled with endolymph
Parts of the bony labyrinth
- The semicircular canals contain the vestibular organs which sense head motion and position
- The cochlea contains hearing organ that senses sound vibration
What is the cochlea and what are its major divisions?
- bony tube rolled up like a snail shell
-The cocheais subdivided into three parallel canals: scalavestibuli,
scalamedia,
scalatympani - separated from scala media by a soft flexible membrane called the basilar membrane
-When the oval window vibrates and sends waves of fluid pressure into the cochlea, the basilar membrane vibrates as well
Organ that sits atop the basilar membrane and contains hairs
organ of the Corti
Sterocilia
hair-like protrusions that transduce mechanical movements into nerve signals
On each hair cell, the tips of different stereocilia are joined to one another by tiny protein strands called _________
tiplinks
Tallest sterocillia
kinocilium
What concentration gradients are different for sterocilia
potassium gradients
What happens to sterocilia when they bend towards the kinocilium and what are the effects of that
Opening the K+ channels produces a graded receptor potential that DEPOLARIZES the hair cell! Why? Because the concentration gradient for K+ is high outside and low inside of the sterocilia
Do hair cells fire action potentials?
Hair cells do NOT fire action potentials!!!!! Depolarization of the somatic compartment opens voltage gated calcium channels, which triggers neurotransmitter release from the base of the hair cell
otoacoustic emissions
sound generated from the inner ear
How is the basilar membrane organized?
The basilar membrane is tonotopically organized, meaning that different parts of the basilar membrane vibrate in response to different sound frequencies • High frequencies vibrate the basilar membrane near its base, whereas low frequencies cause vibrations near the apex
What are spiral ganglion cell?
contains the cell bodies of 1st order bipolar sensory neurons that form the auditory nerve
What are the two parts of the bony labyrinth and what are there functions?
The cochlea - contains sound sensing organs
semicircular canals - contain vestibular organs
Three parallel canals in the cochlea
scala vestibuli
scala media
scala tympani
What is the basilar membrane
The scala tympani is separated from the scala media by a soft flexible membrane called the basilar membrane
Is the relationship between the brain and ear unidirectional or bidirectional and why?
bidirectional because the ear is very sensitive and the brain has to tune its sensitivity based on the ambient amplitude of the stimuli
What is the tectorial membrane?
potassium-rich Gelatin like substance that the top of the steriocillia are embedded in
What happens to the steriocillia when they are bent towards the kinocilium?
mechanically gated K+ channels open, the cell depolarizes, produces a graded potential, Depolarization of the somatic compartment opens voltage gated calcium channels, triggers neurotransmitter release from the base of the hair cell, The neurotransmitter binds to receptors on the afferent vestibular or cochlear nerve
Area of skin innervated by a single spinal neuron
Dermatome
5 sectional of spine + areas they cover
Cervical- arms and back of head Thoracic - back and stomach Lumbar - lower back and front of legs Sacral - buttocks and back of legs Coccygeal - pelvis and groin
Which area of somatosensation enters brain through cranial instead of spinal neurons
Facial somatosensation info
Name of cells that carry info from spinal cord to body and vise versa
Dorsal roots - carry info into spinal cord
Ventral roots - relay commands from spine to muscles
How many pairs of spinal neurons are there
31
What are the two main divisions of grey matter in the spinal cord and what types of neurons to they contain?
Dorsal Horn (contains sensory interneurons) – Ventral Horn (contains motor neurons)
What are the two main ascending tracks in the spinal cord and what information to they relay?
-Dorsal columns relay touch and
proprioceptive information to the brain
– Anterolateral (or spinothalamic) tract relays
pain and temperature information to the brain
What are generator potentials and what causes them?
Stretching of cell membranes (discriminative touch) opens mechanically gated sodium channels and causes excitatory potentials called generator potentials
What are the four main discriminative touch mechanoreceptors and what stimuli do they respond to?
Pacinian Corpuscle - pressure + vibration
Meissner’s Corpuscle - light touch
Merkel’s discs - light touch
Ruffini endings - pressure + vibrations
How are the receptive fields of the four main mechanoreceptors in discriminative touch characterized and how fast do they each adapt to stimuli?
Pacinian Corpuscle - fast, large, vague
Meissner’s Corpuscle - fast, small + sharp
Merkel’s discs - slow, small + sharp
Ruffini endings - slow, large + vague
What stimuli do free nerve endings record and how are their axons (somatosensory afferents) characterized?
temp + pain, unmyleneated, thin fiber (C)
What kind of axon do touch receptors use?
A beta - Second thickest, myelinated
What kind of sensation is relayed by the thickest axon?
Propioception in muscle fibers uses A alpha axons (thick but myelinaded)
What are the two kinds of propioceptors?
-muscle spindle organs (found in muscle) - detect muscle stretch
-golgi tendon organs (found in ligaments)
sense joint angle and position
How does the brain tell the difference between light and firm touches?
Different sensory neurons have different intensity thresholds (“range fractionation”)
What brain regions would process sensory information from the right side of the body?
The dorsal horn -> medulla -> left thalamus -> somatosensory cortex
How is the somatosensory cortex organized?
Forms a somatotopic map of the contralateral side of the body
What region of the brain processes whisker sensation in rodents?
barrel cortex
What kind of receptive fields do neurons in the somatosensory cotex have?
Center-surround (excitatory) center, inhibitory surround
Three main types of nociceptor
-Cool methol receptor - activated by methol, dull pain, low temperatures
-transient vanniloid receptor) is activated by
medium temperatures (and capsaicin!)
- transient receptor potential type M3
is activated by high temperatures
What type of axon do the three nocicpetors use?
CMR1 - c-fibers
TRPV1 - c-fibers
TRPM3 - a - delta fibers
What kind of animal spreads capsaicin seeds and why?
Birds do because their vanniloid receptors are NOT sensitive to capsaicin