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Phys Neuro Part II


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if you are blind in only one eye? what do you lose?
monocular vision on that side which is the lateral 30
process of phototransduction in light and dark
in dark there is alot of cGMP in photoreceptor so this opens Na/K channels allowing Na to come into photreceptor to depolarize it and cause more glutamate to be released

When Light comes in, it changes the conformation of opsin (Photopigment molecule) this activates transducen which activates phosphodiesterase which in turn decreases cAMP so Na/K channels close and photoreceptor hyperpolarizes causing a decrease in glutamate release
what has more discs rods or cones?
rods meaning there are more photopigments and more sensitivety to light so you can see better at night
describe neural processing of retina
photoreceptors contact bipolar cells and bipolar cells synaptically contact ganglion cells.

ganglion cells make up optic n.,chiasm, and optic tract that leave the eye
only retinal cells that provide visual signal to brain
ganglion cells (they become optic n. tract, and optic chiasm)
describe retinal ganglia visual receptive field
2 types of retinal ganglia
1.on center ganglion cells- where if light falls on center of receptive field, neuron is excited. If light falls on surrounding, neuron is inhibited.

2.Off center- If light falls in center, neuron is inhibited. If light falls on the surrounding, neuron is activated

Ganglion cells fire most actively when the contrast is the highest
what does each hemiretina see in left eye?
nasal hemiretina sees left visual field, temporal hemiretina sees right visual field
What does each hemiretina see in the right eye?
the nasal hemiretina sees the right visual field and the temporal hemiretina sees the left visual field
since the L brain sees right visual field and the R brain sees the L visual field, how does this happen
at the optic chiasm the nasal hemiretina crosses over
lesion in L optic n.
lose vision in L eye

only lose monocular vision
Lesion at optic chiasm
lose crossing fibers so lose peripheral vision get tunnel vision
lesion of L optic Tract
lose R visual field
damage to parietal lobe what visual field is affected
since visual field is flipped you lose bottom of receptive field

pie in the sky defecit
Pathway of pupillary light reflex
retina->optic n.->optic chiasm->optic tract
->pretectal dorsal midbrain->edinger westphal n.->oculomotor n.->ciliary ganglion->circular m. of iris
transect L optic n. shine light into L eye
direct response-none

consenual response-none bc pathway is blocked
transcet L optic n. shine light into R eye
Direct respone-constricts

consenual respone-constricts
Transect L oculomotor n.
Shine light into L eye
direct respone-none

consenual respone-yes R consticts
Transect L occulomotor n. shine light into R eye
direct response yes

consenual respone-none
what CN can be tested by looking at the eyes?
Mydriasis pathway for response
hypothalmus and midbrain -> IML of SC -> superior cervical ganglion ->radial muscle contracts and this pulls on the pupil to dialate it
what innervates sensory for cornea?
Pathway for corneal blink reflex
someone touches cornea (ouch!) -> V1 ->spinal trigeminal n. -> facial n.
-> orbicularis oculi m to cause blink
What initiates blink reflex?
touch cornea, bright light (due to sensory component of optic n.) or loud sounds (caused by CN VIII)
Lesion in R V1

Touch R eye

whats the response?
no direct or consenual respone bc never felt it since sensory component is gone
Lesion in R V1

Touch L eye

Response of blink reflex?
Both eyes blink
Cut R facial nerve

Touch R eye

Blink response?
R eye wont blink but L eye will
production of aqueous humor is greater than the drainage causing increased intraocular pressure that damages optic disk which injures ganglion cell and causes blindness
Color blindness
occur mainly in men bc X linked

cant distinguish between red and green
Clouding of the lens

common in old people
Types of neurons in primary visual cortex
simple cells
direction selection neurons
complex cells
blob cells
describe simple cells in primary visual cortex
differs from ganglion cells bc see lines rather than circles

involved with determing motion of an object
direction selective neurons in primary visual cortex
responds to direction of a line moving across the receptive field in a certain direction only
What 2 cells types of the primary visual cortex are involved with determining motion of objects
simple cells and direction selective neurons
describe complex cells in primary visual cortex
determines shape of objects
Describe blob cells of primary visual cortex
have circular fields like ganglion cells

Blob cells determine color of object
Describe the overall organization of primary visual cortex
four main cell types are organized into cubes of cortex. Each cube analyzes a particular point in space and determines all of the important info of that area. Info from the cubes then flow to a higher order association cortex to interpret what you see. Info then goes into either the dorsal or ventral pathway
Dorsal pathway of primary visual cortex
goes to parietal lobe. It detects the location of the objects in space and allows detection of motion. Bilateral lesions make it imposible to percieve moving objects
Ventral pathway of priamy visual cortex
courses from the primary visual cortex toward the temporal lobe. It identifies objects. Lesions in this region lead to loss of recognition
what does frequency of sound waves determine?
pitch of sound you hear
What does amplitude of sound waves determine?
loudness of sound
outer ear structures
extneral auditory canal
tympanic membrane
gathers sound waves. helps determine location of sounds in space
external auditory canal
conducts sound waves to tympanic membrane
tympanic membrane
eardrum. vibrates at freqency of sound wave. conducts sound waves to middle ear by converting sound energy to mechanical displacements
Middle Ear structure
made of 3 small bones (malleus,incus, and stapes) the maleus is attached to the tympanic membrane and the stapes is attached to the oval window. the incus connects the malleus and stapes
How does middle ear amplify sound?
It acts as a lever system by acting as a lever and mostly by the force of sound waves that is pushed from the large tympanic membrane to the small oval window. Causes a 20x amplification
Purpose of auditory eustachian tube in middle ear
connects middle ear to pharynx and maintain middle ear at atmospheric pressure. tube is normally closed so with changes in altitude causes difference in pressure in middle ear so tympanic membrane moves and produces pain
describe attenuation (tympanic) reflex
there are 2 muscles in inner ear, the stapedius (innervated by CN VII) and tensor tympani (innervated by CN V). These muscles are activated during lound sounds to diminsh movement of middle ear bones to reduce damage to hair cells. Works best for loud sounds that last awhile instead of sudden loud sounds
Auditory portion of inner ear
Structure of cochlea
v. boney spiral with 3 fluid filled spaces; the scala vestibuli, scala tympani, and the scala media. The scala vestibuli and tympani contain perilymph and the scala media contains endolymph with lots of potassium.

At the apex of the cochlea, the scala media ends and the scala vestibuli and scala tympani join through space called helicotrema
how does cochlea transmit sound waves?
stapes action on oval window converts mechanical displacement to hydraulic displacement. The movement of fluid displaces the basilar membrane and this causes neuronal AP
in the cochlea, Since the noncompressible fluid is in a nonexpansible bone, where does fluid move?
round window prevents the fluid from coming out of the cochlea
Where do hi frequencies displace the basilar membrane of the cochlea?
at the base

the base is stiff and narrow and sensitive to hi frequencies
Where do lo frequencies displace the basilar membrane of the cochlea?
At the Apex

the apex is floppy and wide and sensitive to low frequencies
How are frequencies organized in basilar membrane of cochlea?
diff frequencies coded at different places along basilar membrane
describe structure of Organ of Corti
Attached to the basilar membrane are hair cells (receptor cells, not neurons) At the end of the hair cells, stereocilia attach the hair cells to the tectorial membrane which is on the edge of the cochlea. The stereocilia project into the endolymph of the scala media
How are hair cells in organ of corti depolarized?
remember that K+ conc in endolymph is hi and its lo in stereocilia. Tip links connects the stereocilia to the hair cells. When stereocilia move vertical toward tallest one there is enough stress on the tip links to keep K+ channels open so K+ moves into stereocilia causing DEPOLARIZATION. Ca+ also enters the cells so stereocilia can release the NT glutamate
How are hair cells in organ of corti hyperpolarized?
if stereocilia bend toward shortest stereocilia there is less tension on the tip lenghth and the K+ channels close and causes hyperpolarization
Whats in spiral ganglion?
spiral ganglion is in cochlea and it consists of bipolar cells and they synapse with the hair cells. this forms CN VIII
What does characteristic freqnecy of a neuron depend on?
hair cells that the neuron innervates (EX: if neuron innervates hair cells that is located tonotopically at the 8000 Hz level then neuron would be most sensitive to 8000Hz)
How does in cochlea respond to a louder intensity?
greater number of AP bc louder sound causes more movement of basilar membrane so more neurons will be activated
What encodes frequnecy of sound? What encodes loudness of sound?
frequency is encoded by which neurons are excited (location)

Loudness is coded by frequency of AP and number of neurons activated by sound
Pathway of central auditory processing
start at cochlea's spiral ganglion -> synapse bilaterally at the cochlear n. -> inferior colliculus via Lateral lemniscus -> medial geniculate n. _> primary auditory cortex
what is primary nucleus where horizontal sound localizaion occus?
Superior olivary n.

Can tell if sound comes from L or R
How does Superor olivary n. tell if sound comes from L or R?
there is a time delay with sound. Say sound comes from L side so sound will reach the L ear slightly earlier than the R ear so AP will be initiated earlier in L ear and move farther along axonal pathway than in R ear. Bc of arrangement of neurons in superior olivary n., there are neurons that discharge in response to delay between stimuli reaching ear, these are neurons that fire maximally when they get input from both ear simultaneously.
What determines vertical sound localization?
The pinna bc of its shape, sounds arriving from diffeent vertical levels vary so ear can sort out to determine amplitude of sound
Where is primary auditory cortex?
on superior temporal lobe. neurons here have tonotopic arrangement
Where is secondary auditory cortex?
surrounds primary auditory cortex. process input from primary auditory cortex and allows interpretation of sounds. This area is called Wernickes and is important for speech
conductive hearing loss
decrease conduction of sound from outer ear to inner ear

due to ear wax, perforation of tympanic membrane, otosclerosis
sensorineural hearing loss
due to loss of hair cells in inner ear

due to noise, drugs, tumors, presbycusis
ringing in ears or perception without stimulus

caused by CNS problem or auditory problem
treatments of hearing loss
hearing aid-with intack auditory system but w/inadequate numbers of hair cell, hearing aids amplify incoming sounds

Cochlear implant: if hair cells are dead, a cochlear implant has electrodes that stimulate cochlear nerve
structure and basic physiology of utricle and saccule
both have a sensory apparatus called a macula where the hair cells are . the hair cells contain one long cirlium with a bulbous end called a kinocilium with many stereocilia. All cilia project into a gelatinous substance wich contains Calcium carbonate. Head movement cause the crystals to move due to gravity and this moves cilia changing NT release from hair cells
What do otolith organs (saccule and utricle detect)
linear acceleration and displacement of the head
How does utricle and saccule work?
when head moves change in gravity of head so crystals move in gelatinous substance bending the cilia. movement of cilia toward kinocilium depolarizes and movement away from kinocilium hyperpolarizes

the macula in the utricle is arranged horizontally, the macula in the saccule is arranged vertically so that no matter which way the head moves you are depolarzing and hyperpolarizing something
anatomy of semicircular canals
3 of em oriented 90 degrees to one another

fluid in tube is endolymph

each canal has a buldge called an ampulla. There are hair cells within the ampulla. The cilia of the hair cells contian one kinocilium along with shorter stereocilia. The cilia project into gelatinous mass called the cupola that extends across the ampula. when the head moves the endolymph pushes on the cupola which then bends the cilia
What does semicircular canals detect?
angular acceleration, rotation of head
Function of semicircular canals
say the head rotates to the left, the inertia of the endolymph in the horizontal semicircular canal prevents it from following the rotation so it exerts a force in the directioni of the opposite rotatation of the inertia. the force of the endolymph is exerted against the cupola and this bends the cilia
give pathway of how the central vestibulra pathways influence eye movements
info leaves the semicircular canal through the vestibulocochlear n. (CN VIII) which goes and terminates in the vestibular nuclei in the medualla/pons

the vestibular n. connects to CN III,IV,and VI to coordinate eye movements
What innervates Lateral rectus? medial Rectus?
Lateral rectus innervated by CN VI

Medial recturs innnervated by CN III
what eye muscles are activated and inhibited when you look to the right?
R Lateral Rectus and L medial Rectus are activated

R medial rectus and L lateral rectus are inhibibed
congjugate eye movements
eyes move together
Saccadees eye movement
fast movement of the eye from one fixation point to another
Smooth pursuit eye movements
slow movements that track a target across a visual field
fix eyes on obj but rotate head slowly, your eyes will try to maintain fixation of the object by a slow pursuit movement, eyes then move rapidly back to central position. the combination of both smooth pursuit movement and saccadic movemnt is nystagmus. The direction of nsystagmus depends upon the rapid movement
describe vestibuloocular reflex
reflex that maintains visual image on retina during head turning.

Ex: say head turns left, eyes must move to right to maintin image

so it will excite the L vestibular n. which will activate the R lateral rectus and the L medial rectus
lowest level of motor system hierarchy
alpha motor neurons that innervate skeletal m.
middle level of motor system hierarchy
brain regions that influence lowest level

includes sensorimotor cortex (corticospinal tract) BS, cerebellum, and basal ganglia

function is to execute movement of commandds intended by highest level. coordinate posture
Highest level of motor system of hierarchy
Brain regions that initiate desire to move

includes premotor and motor cortices and association areas of cortex and the limbic system

notifies lowere levels of the desired movements
what is involved in large m. movements and makes sure the right muscle is contracted and inhibited?
basal ganglia
2 major influences on alpha motor neuron
1. Brainstem (posture)
2. corticospinal system
motorneuron pool
all the motorneurons that inneravate a muscle
Motor unit
motorneuron and ALL its muscle fibers
2 ways to increase contraction of muscle by alpha motor neuron
1. increase frequency of AP in alpha motor neurons which will produce temporal faciliationa

2. recruitment of motor neurons is the most important way to increase force
Shoud muscles that perform small movements have more or less muscles per motor units?
should have few muscle fibers per motor neuron for example eye or finger
what is recruited first smaller or larger motorneurons?
smaller motorneurons are recruited first then larger ones.

example when you walk, smaller motorneurons, when you run start recruiting bigger motorneurons

size the motorneuron is proportional to AP size
what is the difference between large and small motorneurons
small motorneurons have less power but are more fatigue resistant

Large motor neurons have alot of power for a short amount of time bc they faigue quickly
2 major organs in muscle
1. muscle spindle which is sensitive to muscle length

2. golgi tendon which is sensitive to force and tension
describe muscle spindles
it is within the body of muscle and its encapsulated. It consists os specialized muscle fibers (intrafusal fibers) that signal the length of the muscle and the rate of change of length of the muscle.

The intrafusal fibers are innervated by Ia and II fibers that transmit lenght info to CNS

the ends of the intrafusal fibers are innervated by gamma motorneurons
What info does muscle spindles give to CNS?
muscle length. Example if muscle gets longer, sensory nerve endings stretch and there is an increase in AP of Ia and II fibers which tells the CNS how long the m. is
sensory neuron that always comes from the muscle spindle only
Ia fibers
what is the firing of Ia fibers proportional to?
length of muscle bc they are parallel to one another
function of gamma motor neurons
they innervate ends of muscle spindle. when it gets excited sends AP to ends of spindle and interfusal m. contracts. If you excite gamma motor neuron, it contract ends of spindle (pull each end of spindle) making the middle of the spindle longer which will increase the AP of the Ia fiber

gamma MN change the gain/sensitivity of the spindle bc spindles are only sensitive over a v. short range of movement. so now spindle sensitivity will change over entire range of movement
what does golgie tendon do?
senses tension of muscle.

golgi tendon has Ib fibers that generates AP proportional to AMOUNT OF TENSION (not length)

pull on muscle-tenses so AP caused by golgi tendon but contract m. LOTS more TENSION so more AP released by contracted muscle
only reflex with just one synapse in pathway
strethc reflex
stretch reflex pathway
muscle lengthens->spindle strectch->activates Ia fibers -> excite alpha motor neurson -> contract muscle
how is a strech reflex performed?
stretch reflex is initiated by tapping on a tendon, it activates the spindle which excites Ia fibers which excite alpha motor neurons which cause contraction of muscle

the other component of the stretch reflex comes from the muscle on the other side of the bone. interneurons inhibit the antagonistic m.
what is the stretch reflex important for every day?
to maintain posture
tendon reflex pathway
muscle tension increases -> golgi tendon Ib rease AP-> excite inhibitory neurons -> inhibit alpha motorneurons so muscle relaxes
Describe how tendon reflex works?
initiated by golgi tendon

if increase tension in muscle, Ib fibers are activated and they inhibit muscles by autogenic inhibition

the antagonist muscles are excited via interneurons
describe withdrawl reflex and the crossed extensor refex and how they work together
activation of pain fibers leads to flexion which causes withdrawl from the stimulus. so pain fibers basically excite flexors and inhibit extensors to permit withdrawl response

The crossed extensor reflex happens on the opposite side of the withdrawl (flexor) reflex. the crossed extensor reflex activates extensors and inhibit flexors to support you during withdrawl
2 types of movement disorders of the Basal ganglia
1. hypokinetic
2. hyperkinetic
hypokinetic disorders
reduced movements

get akinesia, bradykinesia
(slow movements)

muscle rigidity

reduction in thalamocortical projection activity
Parkinsons Disease
type of hypokinetic disorder

loss of dopamine in Substania

Resting Tremor

treat with L Dopa
hyperkinetic Disorders
dyskinesias (increase movement)


thalamocortical projection is enhanced
huntingtons disease
loss of caudate and putamen

Its inherited

To tread decrease dopamine
loss of subthalamic nuclei

reduces inhibion on thalmus to thalmocortical projection increases
index of cortex's EPSPs and IPSPs
Beta waves
Delta waves
deep sleep
EEG during awake state
beta and alpha waves
looks like awake beta and alpha waves
purpose of histamine
keeps you awake
GABA function in sleep cycle
inhibits histamine so you get sleepy
Orexin function in sleep cycle
allows you to stay awake all day and sleep all night
During awake state what is hi and what is lo?
and orexin are hi but GABA is lo
Durin non REM sleep, what is hi, what is lo/
GABA is hi

and orexin are lo
During REM sleep, what is hi, what is lo?
norepi, serotonin are lo

ACH and GABA are hi this causes dreaming and REM sleep
What is major circadian pacemaker?
suprachiamatic nucleaus

does light/dark cycle by retinohypothalmic pathway
What age group has highest REM sleep and goes into deeper sleep?
how long does sleep cycle last
90 min
when does deepes stages of sleep occur?
in early evening in the first or second cycle
What factor is very important for the sleep drive?
adenosine accumulates through day and it excites GABA in the VLPO making you feel sleepy
connection between sleep and immunie funciton
when you are fighting infection, you sleep more

muramyl peptides from bacteria, GHRF, prostaglandin, IL 1 all cause sleep
irresistible sleep attacks during the day.

pt enters REM wo other stages

due to loss of oxexin
loss of muscle tone
Sleep paralysis
pt becomes paralyzed when drift in or out of sleep
hypnogogic hallucinations
graphic dreams that occur at sleep onset
dysfunction of sleep
sleep walking but does NOt occur during REM occurs at stage 3 or 4 of sleep
REM behavior disorder
paralysis of REM does NOT occur so you can act out dreams
primary motivations
allow species to survive
the four fs
3.farenhiet (temp regulation)
Secondary motivations
choices you make for primary motivations

most of humans behavior
2 components of emotion
inner emotion

outer emotion-expression of emotion

you can supress the outer expression by you cant supress the inner emotion
what reguates motivations and emotions?
limbic system
papex circuit
core of limbic system

cingulate cortex (primary sensory cortex)
-> hippocampus ->mammilary body ->ant.nucleus of thalmus
->cingulate cortex
hippocampus primary role
Kluver bucy syndrome
bilateral destuction of temporal lobe

6 phemonemna
1. visual agnosia
2. oral tendencies
3. increase seeking behavior
4. hypersexuality
5. loss of fear (docile)
6. increased vocal activity
role of amygdala
fear response

involved in rage and aggresion

attaches emotional significance to events
function of prefrontal cortex and anterior cingulate cortex
cortical areas responsible for experiencing emotion
Primary function of hypothalmus
emotional expression

it connects autonomic and somatic groups to mediate emotional responses
function of ventral striatum
helps select the appropriate behavior for a situation
primary thalmic n. associated with the limbic system
mediodorsal thalamic n.
four major reward centers
1.dorsal pons
2.ventral tegmental area
3.lateral hypothalmus
4.septal areas

interconnected by medial forebrain bundle
common NT of reward centers

most important NT related to mood
describe unique case of phineus gage
pole through frontal cortex
changes personality

found that frontal lobes are involved in expression and experience of emotion
disorder of limbic

treat w/ drugs that block reuptake of norepi,dopamine,or serotonin
disorder of limbic/mood

depression and mania
too much dopamine

so must decreae dopamine to treat
primary sensory cortices
areas reciving sensory input from thalmus
Primary motor cortex
area producing final motor ouput
unimodal sensory association cortex
association cortex that integrates info related to a single sense
Unimodal motor association
premotor and supplementary motor regions
Multimodal association cortex
integrates multiple sense

analyzes sensory and motor output
3 types of multimodal association cortices
1. Posterior association area-integrates info from several sensory modalities

2.Anterior association area- prefrontal cortex. Allows thinking and planning

3. Limbic-gives emotional content to sensory info
general flow of info from sensory input to motor output
sensory receptors->primary sensory cortex->Unimodal sensory association cortex-> Posterior and limbic association areas-> Anterior association areas-> Unimodal motor association area-> Primary motor cortex -> Skeletal m. movement
Function of L and R hemisphere reguarding language
L side control speech

R side control non verbal and prosody
language disorder due to brain damage
Lesion of Broca
Motor aphasia

problem with generating words but the person can understand the language so the person is aware they have a problem
Lesion of Wernicke
Sensory aphasia

pt cant understand words and has trouble making sense but does not know they have a problem
Conduction aphasia
problem with arcuate fasciculus

pt is fluent and can comprehend speech but they cant repeat words
explicit (declarative memory
memories for facts and events

to recall it you have to consciousessly think about it
episodic memory
recollection of a persons experieces. Memory of events
Sementic memory
knowledge. memory of facts
implicit (nondeclarative) memory
recalled memories unconcsiously
procedural memory
type of implicit memory

knowledge of how to do thing
Previous exposure of something allow you to recall it faster
Nonassociative memory
person learns aspects of a single stimulus. The process is automatic
person is used to stimulus its learned to be unimportant
Response to stimulus gets larger with each repition
Associative memory
Requires a relationship between stimuli
operant conditioning
positive or negative reinforcement alters response
What type of memory does the cerebellum store?
implicity memory associated with muscles

ex:vestibuloocular reflex and the conditined eyeblink
whay type of memory does the neostriatus store?
procedural memory
Where are explicit memories stored?
multimodal association cortex
How is memory stored/
sensory input comes in medial temporal lobe

the amygdala attaches emotion to sensory input

the hippocampus distributes the memory to the proper regions of cortex
Anterograde Amnesia
inability to learn new info
Retrograde amnesia
inability to retrieve info
Lesion in medial temporal lobe
aterograde amnesia but you can recall previous memories

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