BCS110 UNIT 2

2 ways light can be thought of

particles/photons or waves

Visible light range for humans

380-760nnm

What do wavelength and intensity of light correspond to

wavelength is light Intensity is brightness

What can light do, what type of lens is the eye, what does this cause, what does the image in your eye look like

Bounce off: reflected Be bent: refracted Scattered: diffracted Absorbed Convex lens Light goes through the eye and is refracted (bent) into a focal point Flipped upside down

What is convex lens of eye made of, what is the correspondence between point in space and retina

cornea + lens 1:1

What is the process of accommodation, what muscles do it, what is each shape for

Change of shape of lens Ciliary muscles Flat for far objects Round for near objects

2 modes of vision, what is convergence, what is binocular disparity

Field of view and binocular vision (depth) convergence: eyes turn slightly inward when viewing objects Binocular disparity: difference in position of same image on the two retinas, used for depth perception

What do retinas do, what does “inside out” mean, what are the 5 layers, which are input and output

convert light to neural signals Inside out: light passes through several cell layers before reaching receptors 5 layers: receptors (rod and cone, input), horizontal cells, bipolar cells, amacrine cells, retinal ganglion cells (output)

Regions of retina, how big is good vision, what is completion

Fovea: high acuity area at center of retina Ganglion cell layers pulled aside Blind spot: no receptors where retinal ganglion axons exit eye (optic nerve) Good vision is size of moon What is completion: visual system fills in blind spot based on info from other eye or predictions from surrounding details

What are rods and cones (vision type and traits), how do they differ, which is higher in count, where is each, whats the duplex theory of vision, what is the difference in circuits, what does this cause

Photosensitive cells Rods are scotopic vision -high sensitivity in night time (needs 1 photon for activation) -low acuity and high convergence (bad vision) -no color Cones are photopic vision -low sensitivity in day time (needs 20 photons for activation) -High acuity, low convergence (good vision) -color vision Differ in anatomical ways (size, shape, number, location) and physiological ways More rods then cones Cones in fovea Rods outside fovea Duplex theory of vision: rods and cones mediate different types of vison Rods is multiple rods for 1 retinal ganglion Cone is 1 cone for 1 retinal ganglion cones have higher acuity due to the 1:1 ratio

3 types of cones in retina, what is trichromatic theory, what is the preferred color in back of eye

L cone: red M cone: Green S cone: Blue trichromatic theory: color is encoded in ratio of activity of 3 kinds of receptors Preferred: yellow, caused by red and green receptors

What is visual transduction and transmission, pathway (dark and light), whats their resting potential, what makes PSP into AP, what are indirect and direct transmission

Transduction: Conversion of physical stimulus (light or dark) to neural signal (psp). Happens when center cone is hyperpolarized, leading to decrease in glutamate, and releasing a g-protein to excite on-center bipolar. (light), or when it's depolarized, leading to increase in glutamate (dark) Transmission: In light, the lack of glutamate excites the on-center bipolar, which deactivates the metabotropic receptor and decactivates an inhibiting G-protein, which releases a neurotransmitter into the retinal ganglia, sending an AP. In dark, the influx of glutamate excites the off-center bipolar, which activates the ionotropic receptor, and allows sodium to flow in, depolarizing it and releasing at AP into the retinal ganglia. -40 mV Not the receptor, uses indirect transmission due to a lack of axon Indirect transmission: no axon to make AP Direct transmission: has an axon to make AP

What is the receptive field, what is center surround

Mechanism of output of retina to nervous system

Area of visual field within which it is possible for a visual stimulus to influence firing of neuron

Retina to primary visual cortex pathway name, what happens, where do axons decussate

Retinal geniculate striate pathway Signals from left field of both eyes goes to right primary visual cortex, signal from right field of both eyes goes to the left primary visual cortex Nasal part of visual tracts (axons) decussate at optic chiasma

Layers of LGN, function

Two channels: Parvocellular (P) layer: small cells, top 4 layers are color, detail, still, cones Magnocellular layer: large cells, bottom 2 layers are no color, motion, rods

Inputs to primary visual cortex, what is overepresented in visual cortex

LGN cells project to layer 4 of cortex P and M cells project to different subdivisions of layer 4 Cortical neurons continue to be monocular in layer 4 of primary visual cortex Central/foveal region of visual field is over represented in primary visual cortex

What are visual field deficits

Result from damage at different points along the primary visual pathway

Difference in receptive field of v1 neurons in layer 4 vs layers 1-3 and 5-6

layer 4 have concentric receptive fields with center surround organization Layer 1-3 and 5-6 neurons have rectangular receptive fields, and are orientation/edge sensitive

What happens in center-surround when center has light

Light hyperpolarizes and thus inhibits center, meaning no glutamate is released. On center bipolar cell: No glutamate to open potassium channels (excited), so on center depolarizes, and releases NT to on-center ganglion cell, that sends an AP to CNS Off center bipolar cell: No glutamate to open sodium channels, so off center is hyperpolarized (inhibited), and no AP is sent

what happens in center surround when center has no light

Lack of light causes depolarization and causes center to release glutamate On center cell: Glutamate oopens potassium chanels and hyperpolarizes the cell as potassium leaves, inhibiting it, and no APs are sent Off center cell: Glutamate opens sodium channels and causes depolarization, and NT are sent to off-center ganglion cells which release an AP into CNS

What type of receptors does On-center use

Metabotropic glutamate receptors

What type of receptors does off-cenmter use

Ionotropic receptors that open sodium channels

Where do biopolar cells receive direct and indirect input

Direct: photoreceptors above them (center) Indirect: horizontal cells surrounding photoreceptors (surround)

Receptive fields function

respond to more complex or specific stimuli

Dorsal stream

m pathways Where Behaviour Rod

Ventral stream

P pathways What Perception Cone

Function of auditory system, what dimensions of sound correlate to what in perception

Perceive sounds to localize and identify sounds in space

Amplitude: volume (what do you hear) Frequency: pitch (where is it) Complexity: timbre

What is a natural sound, what can it be broken down into, how does pitch relate to gendered voices

complex patterns of vibrations Components Sine waves 100 frequency spacing is male 200 frequency spacing is female

Pathway of sound propagation in the ear

Wave enters auditory canal, and strikes eardrum/tympanic membrane Ossicle (hammer, anvil, stirrup) vibrates (middle ear bones that act as an amplifier) Oval window vibrates Fluid cochlea set in motion Vibration of fluid dissipated at round window

Cochlea structure, what creates the up down motion in the middle scala

3 chambers (scala) divided by reissner membrane and basilar membrane Organ of corti sits on basilar membrane in middle scala Middle scala goes up and down due to the influx of cochlear fluid in the top chamber, spiraling around and exiting in the bottom chamber.

What does up and down movement in basilar membrane translate to, what happens to it as it goes down the basilar membrane, why

Up and down motion translates to frequency/pitch of sound Gets lower as it goes down the basilar membrane, because the start is stiff and vibrates easier, while the end is flexible and is not able to vibrate as much

Two types of hair cells in organ of corti, counts, what do they all have + location, what does up-down motion of basilar convert to in the structure

Inner hair cells, around 3500, Outer hair cells, around 14000

All have stereocilia on upper surface in or near tectorial membrane

Up down motion of basilar membrane convert to side to side motion of stereocilia

Transduction of sound-induced motion, what does the bending of the 2 hair cells do, what type of transduction and transmission in auditory system

Mechanotransduction: conversion of mechanical stimulus to electrical/chemical signal

Outer hair cells change length and augment (boost) basilar membrane motion, allowing potassium in as they bend

Inner hair cells release transmitter onto axons of auditory nerve, as they bend after outer hair cells bend

direct transduction, indirect transmission

What is tonotopic organization

The idea that auditory system structures are organized according to frequency

Pathway of ear to auditory cortex, including locations, where is decussation

cochleal nuclei (medulla) -> superior olive (pons) -> inferior colliculi (tectum) -> ipsilateral medial geniculate nuclei/MGN (thalamus) -> ipsilateral primary auditory cortex Decussates between medulla and pons

Where is auditory cortex located, what does it include, what type of organization does it have

temporal lobe Primary core (a1), up to 10 belt/secondary regions Tonotopic

What is left right sound localization cues, what does this result in, where does sound localization take place, how

sounds located off the midline reach two ears at different times and different intensities

Results in: Sound from left is louder and faster in left ear, same idea for right.

takes place in Superior olive

using push pull

Where does pitch perception happen

A1 (primary auditory cortex)

Where are auditory signals conducted to, dorsal vs ventral streams

Auditory signals are conduced to two areas of association cortex -Posterior parietal assocation cortex -Prefrontal cortex Where (superior olive) vs. What (pitch center) Same as visual pathways

Interactions between auditory and visual system, what is McGurk effect

Some posterior parietal neurons have both visual and auditory receptive fields McGurk effect: vision effects way sounds are perceived

Lesions of auditory cortex effects

Unilateral legion: cant localize sounds Bilateral: problems with localization and pitch discrimination

What is conductive and nerve deafness caused by

Conductive: damage to ossicles Nerve: damage to cochlea

Is touch mechanoreceptors direct or indirect transmission

direct

what is exteroceptive system, examples

part of somatosensory system, external stimuli Touch pain temp

What is proprioceptive system, examples

part of somatosensory system, body position Muscles, joint balance

What is interoceptive system for

body conditions

4 types of touch mechanoreceptors, function, adaptation speed and diameter of each, what do they all have, where is the cell body, how does transduction and what type of transduction happen

meissner corpuscles: light touch, brief, small receptive merkel disks: light touch, ongoing, small receptive pacinian corpuscle: hard touch, brief, large receptive ruffini ending: hard touch, ongoing, large receptive All have axons and dendrites Dorsal root is where cell bodies are When you make physical contact, membrane of receptor and dendrites are deformed and ion channels open, letting Na+ in, this is direct transduction

where does transduction of pain and thermal stimuli occur

free nerve endings

what are pain receptors called, what stimuli do they respond to, what type of receptor responds to all

nociceptors mechanical, thermal, chemical polymodal

what are thermoreceptors sensitive to, what are the 2 types

temperature in innocuous ranges, warm and cold

what is transmission of pain and temperature receptors done through

myelined A delta fibers (rapid adapting) or unmyelinated C fibers (slow)

Distribution of exteroreceptors in body

Finger tips rich in mechanoreceptors with small diameters/receptive fields (meissner corpuscles and merkel disks)

High density of nociceptors (pain) in palm and sole

More cold then warm thermoreceptors, with high density in face and ears

where do fibers from cutaneous receptors gather and enter, what is dermatome

gather in nerves and enter spinal cord via dorsal roots Dermatome: area of body that is innvervated (supplied with nerves) from left and right dorsal roots of given segment of spinal cord

Where does touch system decussate

Dorsal column nuclei in medulla

what is dorsal-column medial leminscus pathway, where does is it decussate

Ascending tract that sends touch and muslce/joint info

First synapses and decussates in dorsal column nuclei of medulla

what is anterolateral system for, how many tracts, what happens

pain and temp First synapse in spinal cord ascending and descending tracts locus coeruleus in pons alerts body to pain superior colliculus in tectum makes body look at pain Periaquedectual gray in tegmentum modulates pain and sends signals down spinal cord VPN (ventral posterior nuclei): transmits pain into to somatosensory cortex

what are the 2 types of proprioceptors, location, what do they do, speed

golgi tendon: force of muscle, slow, in series with muslce fibres Muscle spindle: length of muscle, parallel with muscle fibers

proprioception from joints, what do they do, what are the types

4 types of mechnosensitive proprioceptors in joints respond to changes in angle, direction, velocity of joints slow adapting to stretch: golgi organ, ruffini ending fast: golgi-mazzoni corpuscle, paciniform corpuscle

What does vestibular system do, what structures, what system is it similar to,

monitors movement and position of head, giving sense of balance 2 structures: semicircular canals and otolith organs auditory

what do semicircular canals do, where is the push pull

detect turning movements of head, angular acceleration theres a canal for each axis, and there are pairs. When one canal's hair cells is excited, another canal is inhibited

what do otolith organs do

sense changes of head angle and linear accelerations

Tract of vestibular system, what info does inferior olive and cerebellum get from it

Goes to VPN in thalamus then somatosensory cortex proprioceptive

primary somatosensory cortex input, oeganization, distortion

contralateral input organized according to map of body distorted, more sensitive to tactile/position

organization of somatosensory cortex, what stream

4 strips each is a diff kind of sensory input outer: muscles and joints inner: skin dorsal stream: s1 to posterior paretial cortex

what do chemical senses do, what do olfaction and gustation look at

monitor chemical content in environment olfaction: airborne chemicals gustatory: chemicals in mouth

roles of chemical senses in nature

find food judge nutrition and safety of food avoid predators/hazards social communication/mating

where are olfactory receptor found, what unique abiliity do they have, how many types of receptors in humans, where are dendrites and how do odorant molecules bind

upper part of nose in nasal eptihelium they are regularly replaced via neurogenesis 300 types in humans dendrites in mucus, support cells create odorant binding protein that bring odorant molecules into mucus

Relationship between olfactory receptor protein molecule and odor sensitivity, how are scents differentiated and what is this called

receptors have 1 type of protein molecule, and 1 protein molecule can respond to multiple odors this is via the pattern of activity across other receptors, this is called population code

transduction of olfactory stimulus + type, what ion channels ion, depolarization type, how big and long is psp + cause,

uses metabotropic receptors and g proteins (indirect transduction)

activation opens ion channels (influx of Na+ and Ca2+, outflux of Cl-)

graded depolarization

depending on strenght and duration of odor 50mv, 1 second PSP (usually 5ms), caused by chloride leaving

How are olfactory receptors organized, where does axon of olfactory receptor terminate, where does olfactory glomerulus

Chemotopic organization Each glomerulus gets input from many receptors with the same protein, and are arranged in a chemotopic way mitral cell dendrites in olfactory glomeruli within olfactory bulb

Projections from olfactory bulb, 2 pathways

Olfactory tract projects bilaterally to piriform cortex above amygdala in medial temporal lobe, skipping thalamus 2 pathways from medial lobe Limbic system: odor linked memories via Proust effect Thalamus orbitofrontal cortex: conscious perception (flavor) in medial dorsal nucleus (MDN)

Organization of piriform cortex, how are epileptic seizures caused here

All glomeruli go to all parts of piriform cortex Population code happens through this to differentiate smells Most excitatory region of brain, so it's very stimulated and can cause seizures

what receptors are responsible for taste, what are the 5 basic tastes and which one is no nutrient, goal of taste system, what does flavor depend on

taste receptor cells sweet, sour, salty, bitter, umami. Bitter is no nutrients Goal is to determine if a food has nutrients or not flavor depends on 5 senses via ventral stream

taste bud groups in tongue, regional differences

filiform papilae: move food around vallate, foliate, fungiform papilae: taste bud for actual taste subtle regional differences, but most of tongue is sensitive to all tastes

which cells undergo neurogenesis

olfactory receptor cells and taste receptor cells

central taste pathway

gustatory afferent neuron -> ipsilateral solitary nuclei in medulla -> VPN in thalamus -> primary gustatory cortex in parietal cortex (taste) in secondary gustatory cortex in orbitofrontal lobe, chemical and non chemical info combines in ventral stream to make flavor

what are anosmia and ageusia

anosmia: inability to smell, caused by olfactory nerve damage, or tumor in olfactory tract leads to loss of interest in eating or depression ageusia: inability to taste

organization of sensorimotor function, how do signals flow

hierarchial association cortex at top, muslces at bottom signals flow between levels over multiple paths

relationship between motor output and sensory input

sensory input guides motor output

how does learning effect sensorimotor system

learning changes sensorimotor control from conscious to automatic

Two major areas in sensorimotor association cortex, what stream are they in

Posterior parietal assocation cortex (PPAC) dorsolateral prefrontal association cortex (DLPFAC) Dorsal stream

What is ppac, What does PPAC do, what info is needed, how does it get it

Posterior parietal association cortex launch movements needs: position of body parts location of target needs somatosensory, auditory and visual info dorsal stream

What does electrical stimulation of PPAC do, what are the 2 effects of damage to PPAC do, where does it output

Causes patients to experience intent to perform an action

Apraxia: inability to make requested movement
Contralateral neglect: inability to respond to stimuli contralateral to lesion outputs to DLPFAC

secondary motor cortex (m2) and frontal eye field

DLPFAC input, function, what stream inputs through what cortex, whats the output

PPAC

when intent to move is made, forms a plan of action and anticipates consequences


also gets input from ventral stream via ventrolateral PFC, which is the termination site of ventral stream

secondary motor cortex

secondary motor cortex (m2) inputs, major regions, function, output

primarily DLPFAC, also PPAC premotor, supplementary, cingulate converts general plan of action into specific sets of instructions, during planning or imagining of movements outputs to m1 (primary motor cortex)

Primary motor cortex function, what converges here, what does it launch

controls execution of movements cortical sensorimotor signals converge at m1 launches medullary tract, and signals depart from cortex

m1 organization, distortion, how is feedback received, what happens if you electrically stimulate m1, effect of small and big lesions

organized in somatotopic manner (body map of parts of body) distortion in that most of m1 is dedicated to intricate movements, like hand and face movements each site receives feedback from S1 (primary somatosensory) from receptors in muscles and joints that the sites influence if you stimulate it, 1 group of neurons/area in m1 = 1 particular movement (through many muscles) Small lesions have a minimal effect, large lesions disrupt ability to move one body part independently of other body parts

what are mirror neurons, what is it the basis of

neurons active in m1 when observing actions, where the body doesn't move due to low level of activity neural basis of learning by imitation

what do cerebellum and basal ganglia do, what do they do during cortical damage

coordinate and modulate movement allows for visually guided responses despite cortical damage

cerebellum motor command input, motor performance feedback input, function

motor commands come from m1 and brainstem motor nuclei

motor performance feedback input comes from somatosensory and vestibular system involved in coordination

cerebellum circuit (motor plan, proprioceptive info, correction commands)

motor plan: M1 -> pontine nuclei -> middle peduncle -> cerebellum proprioceptive info: medial leminscus -> inferior olive -> inferior peduncle -> cerebellum correction commands: cerebelum -> red nuclei cerebellum -> ventrolateral nuclei (VLN) in thalamus -> M1

Components of basal ganglia

striatum globus pallidus subthalamic nucleus substantia nigra

Basal ganglia 2 major pathway function

direct: excitation, facilitates motor programs in m2 that are adaptive for present task indirect/hyper-direct: inhibition, inhibits competing motor programs

basal ganglia 2 major pathways

direct: yes m2 sends instructions to striatum, substantia nigra says yes to striatum, striatum inhibits GPi, so thalamus (VAN) can say yes to m2 indirect/hyper direct: m2 sends instruction to striatum, substantia nigra says yes to striatum, striatum knocks out GPe which turns on GPi, inhibiting thalamus (VAN) so it says no to m2

Basal ganglia diseses cause and effect

Parkinsons: loss of dopaminergic neurons in substantia nigra, leads to automatic no (only indirect pathway functions) Huntington's: loss of striatum neurons in indirect pathway, leads to automatic yes.

touch, pain, temp, muscles and joints method of tranduction and transmission with ions involved

transduction: receptors are physically deformed, which lets Na+ in for touch/muscle/joint and Ca2+ in for pain/temp

touch, muscle, joint ascending pathway

Dorsal column nuclei -> VPN -> somatosensory cortex -> dorsal + ventral streams (PPAC and VLPFAC)

pain + temp ascending pathway

Locus coeruleus -> superior coliculi -> periaquductal gray -> VPN -> somatosensory cortex -> dorsal and ventral streams (PPAC, VLPFAC)

visual ascending pathway, method of transduction + transmission + ions involved and their movement

retina -> LGN -> visual cortex layer 4 -> inferotemporal cortex -> dorsal and ventral streams (PPAC, VLPFAC) indirect transduction via G protein that blocks Na+ from entering indirect transmission, as retinal ganglia cells send APs

auditory ascending pathway, method of transduction + transmission + ions involved and their movement

ear -> superior olive -> inferior colliculi -> MGN -> Auditory cortex + pitch center -> dorsal and ventral stream (PPAC AND VLPFAC) direct transduction via ion channels breaking from hair cell deformation, letting K+ in indirect transmission because auditory ganglial cells send APs