Neuro - Exam 3 - Review

Front 1

level at which orientation of brain changes

Back 1

level of thalamus (diencephalon)

rostral toward forehead/ventral toward feet

Front 2

major landmarks on dorsal surface of brainstem

Back 2

tectum: superior & inferior colliculi

trochlear nerve

4th ventricle & cerebellar peduncles

gracilis & cuneate tubercles

Front 3

superior colliculi

Back 3

part of tectum
processing of visual information (sensory and motor inputs)

involved in visual reflexes and control of eye movements

compression due to pineal gland tumor --> Parinaud Syndrome (paralysis of upward gaze)

Front 4

inferior colliculi

Back 4

part of tectum

processing of auditory information

Front 5

trochlear nerve

Back 5

CN IV

emerges from midbrain just caudal to inferior colliculus

innervates superior oblique of eye

only cranial nerve to exit dorsal surface of brainstem

Front 6

fourth ventricle

Back 6

rostral 2/3 --> dorsal aspect of pons

caudal 1/3 --> dorsal aspect of rostral medulla

Front 7

superior cerebellar peduncle

Back 7

connects cerebellum to thalamus

Front 8

middle cerebellar peduncle

Back 8

connects cerebellum to pons

Front 9

inferior cerebellar peduncle

Back 9

connects cerebellum to spinal cord

Front 10

gracilis and cuneate tubercles

Back 10

2 small elevations caudal to 4th ventricle that mark locations of nuclei gracilis & cuteatus

neurons in nuclei receive discriminative touch, proprioception, vibration via fasciculi gracilis & cuteatus

give rise to axons that cross midline and ascend to contralateral thalamus as medial lemniscus

Front 11

major landmarks on ventral surface of brainstem

Back 11

crus cerebri

pons
- pontine nuclei
- pyramids

Front 12

crus cerebri

Back 12

fibers continue rostrally with internal capsule

contain descending corticospinal and corticobulbar fibers to innervate motor neurons in spinal cord and brainstem

Front 13

pons

Back 13

pontocerebellar fibers

from neurons in ventral pons to contralateral cerebellum via middle cerebellar peduncle

Front 14

pontine nuclei

Back 14

receive descending cortical input

relation between cortex and cerebellum for coordination of movement

Front 15

pyramids

Back 15

caudal to pons

majority of fibers are descending corticospinal axons that originated in ipsilateral motor cortex & are destined for motor neurons in contralateral spinal cord

Front 16

location of pyramidal decussation

Back 16

caudal end of medulla

Front 17

75-90% of crossing fibers at pyramidal decussation

Back 17

descend in lateral funiculus as lateral corticospinal tract

--> voluntary movement of limbs

Front 18

major ascending pathways of brainstem

Back 18

dorsal column-medial lemniscus (DC-ML)

anterolateral system (ALS)

trigeminothalamic tract

spino/cuneocerebellar tract

Front 19

DC-ML

information

origin

Back 19

motion, vibration, position sense from body

origin = sensory receptors in limbs/trunk

Front 20

DC-ML

pathway

Back 20

origin - sensory receptors in limbs/trunk

1* neurons ascend w/in ipsilateral dorsal columns of cord, synapse on 2* neurons in nuc. gracilis/cuteatus of caudal medulla

2* neurons cross midline as internal arcuate fibers and ascend through brainstem as medial lemniscus to contralateral thalamus

3* neurons - contralateral thalamus to somatosensory cortex

Front 21

lesions affecting DC-ML

Back 21

spinal cord lesion --> ipsilateral loss of MVP

medial lemniscus (braintem) lesion --> contralateral loss of MVP

Front 22

anterolateral system

information

origin

Back 22

pain, temperature and crude touch from body

origin - sensory receptors in limbs/trunk

Front 23

anterolateral system

pathway

Back 23

1* neurons - receptors to SC

2* neurons - cross at level of entry, ascend through contralateral spinal cord and brainstem to thalamus

3* neurons - thalamus to somatosensory cortex

Front 24

anterolateral system

lesions

Back 24

spinal cord lesions --> contralateral loss of pain, temperature, crude touch

brainstem lesions --> contralateral loss of pain, temperature, crude touch

Front 25

trigeminothalamic tract

Back 25

MVP, pain, temp, crude touch from head

origin - three divisions of CN V

1* neurons - from trigeminal ganglion to trigeminal nucleus

2* neurons - trigeminal nucleus to contralateral thalamus via trigeminothalamic tract then to sensory cortex

Front 26

spino/cuneocerebellar tract

Back 26

movement and position sense from body

origin - deep tendons, joints

ends - ipsilateral cerebellar cortex

Front 27

major descending pathways of brainstem

Back 27

corticospinal (pyramidal) pathway

corticobulbar pathway

Front 28

corticospinal (pyramidal) pathway

information
origin

Back 28

voluntary movement of limbs

origin - motor cortex

Front 29

corticospinal (pyramidal) pathway

pathway

Back 29

1* fibers leave motor cortex, descend through internal capsule, sweep ventral to midbrain as crus cerebri

pentrate pons and form pyramids of medulla

at caudal medulla, most fibers cross and descend through spinal cord as lateral corticospinal tract to innervate motor neurons in ventral horns of cord

Front 30

corticobulbar pathway

Back 30

voluntary movement of msucles of facial expression, mastication and movement of head and tongue

origin - motor cortex

end - 2* neurons in brainstem motor nuclei

most fibers provide bilateral input to brainstem

fibers innervating motor neurons controlling musculature of lower face and tongue are crossed

Front 31

upper motor neurons

Back 31

neurons that give rise to a motor pathway but don't interact directly with target muscle

Front 32

upper motor neuron syndrome

Back 32

paresis (weakness) or plegia (paralysis) of muscle

spasticity (increased resisitance to passive stretch)

hyperreflexia

no wasting of muscles

positive Babinski

Front 33

lower motor neurons

Back 33

neurons whos axons innervate the target muscle (final common pathway)

Front 34

lower motor neuron syndrome

Back 34

paresis or plegia of muscle

flaccid paralysis/hypotonia

hyporeflexia (reduced DTRs)

muscle atrophy

fasciculations (spontaneous muscle twitching)

Front 35

primary blood supply to brainstem

Back 35

vertebrobasilar system

Front 36

blood supply to medulla

Back 36

anterior and posterior spinal arteries

posterior inferior cerebellar artery (PICA)

Front 37

blood supply to pons

Back 37

basilar artery (paramedian and circumferential branches)

anterior inferior cerebellar artery (AICA)

labyrinthe artery (branch of AICA, serves CN VII and CN VIII)

superior cerebellar artery (rostral pons at level of CN V)

Front 38

blood supply to midbrain

Back 38

superior cerebellar artery (Branch of basilar artery)

posterior cerebral artery (branch of basilar artery)

posteromedial group (central region, from posterior cerebral artery)

Front 39

Lateral Medullary (Wallenberg's) Syndrome

Back 39

blockage of PICA affects dorsal-lateral region of medulla

contralateral loss of pain & temperature from body (AL system)

ipsilateral loss of pain/temp from face (spinal trigeminal nucleus)

vertigo and nystagmus (vestibular nuclei)

loss of taste from ipsilateral half of tonue (nuc. solitarius)

hoarseness and dysphagia (nuc. ambiguus, CN IX, CN X)

Front 40

Parinaud Syndrome

Back 40

paralysis of upward gaze

compression of superior colliculus due to pineal gland tumor

Front 41

sensory/motor/both CN mnemonic

Back 41

Some Say Marry Money But My Brother Says Big Boobs Matter More

Front 42

Which two CNs attach directly to the forebrain (no brainstem component)

Back 42

CN I (olfactory)

CN II (optic)

Front 43

pathway of CN III fibers (from brainstem)

Back 43

brainstem --> red nucleus --> exit brainstem as CN III in interpeduncular fossa --> passes btw posterior and superior cerebellar arteries --> anteriorly w/in wall of cavernous sinus --> superior orbital fissure

--> superior branch

--> inferior branch

Front 44

pathway of superior branch of CN III

Back 44

superior branch

--> superior rectus muscle

--> levator palpebrae muscle

Front 45

pathway of inferior branch of CN III

Back 45

inferior branch

--> inferior rectus, inferior oblique, medial rectus

--> preganglionic parasympathetic fibers --> ciliary ganglion (postganglionic neurons) --> leave ganglion with sympathetic fibers from superior cervical ganglion) --> penetrate posterior globe --> run anteriorly to innervate ciliary and iris sphincter muscles

Front 46

tract by which ocular motor nuclei communicate (coordinated movement of eyes)

Back 46

medial longitudinal fasciculus (MLF)

Front 47

4 main causes of damage to CN III

Back 47

aneurysm of posterior cerebellar or superior cerebellar arteries --> pressure

tumor, trauma, hematoma --> displacement of brain --> stretching/compression

inflammation or infection of cavernous sinus

syphylitic and tuberculosis meningitis localize btw optic chiasm and temporal lobe

Front 48

Clinical presentations of CN III damage

Back 48

divergent strabismus
diplopia
ptosis
mydriasis
loss of pupillary light reflex
loss of accommodation
anterior alternating hemiplegia
Claude's syndrome

Front 49

Divergent strabismus

Back 49

outward deviation of eye

fom imbalance of muscles innervated by CN III and superior oblique/lateral rectus

difficulty moving eye fully up, down or in

Front 50

ptosis

Back 50

drooping eyelid

from lack on input to levator palpebrae

compensation by contracting frontalis muscle (CN 7) causing wrinkled forehead on affected side

Front 51

Mydriasis

Back 51

pupillary dilation

from loss of parasympathetic innervation to iris sphincter causing unopposed sympathetic innervation of iris radial muscles

Front 52

Loss of accommodation

Back 52

inability to increase curvature and refractive power of lens to see close objects

abnormal near response
pupillary constriction
accommodation (focusing power)
convergence of eyes due to bilateral input to MR

Front 53

Anterior Alternating Hemiplegia (Weber's) Syndrome

Back 53

lesion affects CN III and adjacent corticospinal fibers

ipsilateral ophthalmoplegia

contralateral hemiparesis (descending fibers cross at pyramidal decussation)

paralysis of contralateral lower face and tongue (if corticobulbar fibers are also affected)

Front 54

Claude's syndrome

Back 54

ipsilateral ophthalmoplegia (CN III)

contralateral hemiparesis (descending corticospinal tract)

contralateral paralysis of lower face and tongue (corticobulbar tract)

contralateral ataxia (rubrospinal tract)

Front 55

Trochlear nerve - overview

Back 55

arises from brainstem

only CN to exit from DORSAL surface of brainstem

longest intracranial pathway

only CN that CROSSES

damage to distal nerve --> ipsilateral effect

damage to nucleus --> contralateral effect

Front 56

Pathway of trochlear nerve

Back 56

trochlear nucleus (ventral to PAG at level of inferior colliculus) --> axons pass dorsally around PAG, cross, exit from dorsal surface of brainstem

--> passes btw posterior and superior cerebellar arteries --> turns anteriorly

--> runs in lateral wall of cavernous sinus --> enter orbit via superior orbital fissure

--> innervate superior oblique of contralateral eye

Front 57

actions of superior oblique

Back 57

depression
abduction
intortion

(look in, then down)

Front 58

3 major causes of damage to CN IV

Back 58

aneurysms of posterior and superior cerebellar arteries --> compression of nerve

inflammation w/in cavernous sinus

susceptible to surfical intervention in region of tentorium cerebelli during surgical approaches to midbrain

Front 59

Clinical presentations of CN IV damage

Back 59

diplopia

inability to direct eye downward, esp. when looking medially (difficulty reading, walking down stairs)

affected eye is extorted and elevated

compensation by tiliting head to side of normal eye

Front 60

Damage to trochlear NERVE --> head tilted toward ____ side

Back 60

Damage to trochlear NERVE --> head tilted toward NORMAL side

Front 61

Damage to trochlear NUCLEUS --> head tilted toward ____ side

Back 61

Damage to trochlear NUCLEUS --> head tilted toward AFFECTED side

Front 62

Pathway of abducens nerve

Back 62

abducens nucleus (in tegmentum of pons, just below 4th ventricle) --> axons course ventrally through tegmentum and basal (ventral) pons

--> exits brainstem at pont-medullary junction --> anteriorly over apex of petrous part of temporal bone --> traverses cavernous sinus --> enters orbit via superior orbital fissure --> innervates LR

Front 63

5 major causes of damage to CN VI

Back 63

vascular insufficiencies of basilary artery and/or its circumferential branches

compression against ridge of petrous part of temporal bone by increased intracranial pressure

4th ventricle tumor --> compression of CN VII over abducens nucleus --> affect upper and lower regions of face ipsilateral to injury

middle ear infections and inflammation of cavernous sinus

fractures of base of skull (close to floor of posterior cranial fossa)

Front 64

Clinical presentations of damage to CN VI

Back 64

convergent strabismus (eye directed inward due to unopposed action of MR)

diplopia

compensation by turning head toward affected side

middle alternating hemiplegia

Front 65

middle alternating hemiplegia

Back 65

ipsilateral ophthalmoplegia (CN VI)

contralateral hemiparesis (corticopinal tract)

Front 66

4 types of eye movements

Back 66

slow pursuit

saccadic

nystagmus

vergence

Front 67

slow pursuit

Back 67

slow

conjugate (same direction)

used to track objects

Front 68

saccadic eye movement

Back 68

rapid, jerky

voluntary or reflexive

brings objects of interest onto fovea of retina

Front 69

nystagmus

Back 69

rudimentary type of saccade

resets eyes on new target after having followed a previously moving target that has left field of view

2 phases: slow and fast (direction dictated by fast phase)

Front 70

spontaneous nystagmus

Back 70

neurological damage

damage to vestibular system or its main connections (cerebellum)

Front 71

vergence

Back 71

disconjugate (eyes move in opp. directions)

"near response" - necessary for viewing objects close up

controlled by bilateral input to oculomotor nuclei from supraoculomotor nucleus

Front 72

2 types of voluntary eye movements

Back 72

horizontal gaze

vertical gaze

Front 73

horizontal gaze

Back 73

controlled by neurons in PPRF

PPRF neurons driven by UMNs in contralateral frontal eye fields of the cortex

horizontal movement results from ipsilateral CN VI and contralateral CN III activation of LR and MR, respectively

Front 74

PPRF

Back 74

paramedial pontine reticular formation

aka: lateral gaze center

Front 75

frontal eye fields

Back 75

in cortex

project 2 populations of neurons in ipsilateral abducens nucleus

one pop --> ipsilateral CN VI to innervate LR muscle

other pop --> axons cross midline and ascend as part of the medial longitudinal fasciculus to innervate motor neurons in contralateral oculomotor nucleus

Front 76

vertical gaze

Back 76

controlled by rostral interstitial nucleus of MLF (riMLF)

recieves bilateral input from frontal eye fields

projects to oculomotor nucleus and to trochlear nucleus

Front 77

Vestibulo-ocular reflex (VOR)

Back 77

movement of the eyes in response to activation of the vestibular system (equal in magnitude, opp direction to head movement)

activated by hair cells in semicircular canals (angular acceleration) and otolith organs (linear acceleraton)

--> ipsilateral vestibular neuclei (via vestibular ganglion and CN VIII)--> contralateral abducens nucleus (innervates ipsilateral LR & contralateral MR via MLF and oculomotor nuc.)

Front 78

example of VOR:

turn head LEFT...

Back 78

turn head LEFT --> LEFT semicicular canals activated --> RIGHT abducens activated --> rotation of eyes to RIGHT

Front 79

Right-beating nystagmus

Back 79

lesion to LEFT vestibular nerve or nuclei

RIGHT vestibular nuclei in control

greater activity in RIGHT vestibular nuclei causes eyes to drift to LEFT

eyes snap back to RIGHT

Front 80

lesions affecting eye movements

Back 80

lesion of LEFT frontal eye fields

lesion of RIGHT PPRF

lesion of RIGHT abducens nucleus

Lesion of RIGHT abducens nerve

Lesion of LEFT vestibular nuclei or CN VIII

lesion of LEFT MLF (anterior internuclear ophthalmoplegia)

Front 81

Lesion of LEFT frontal eye fields

Back 81

eyes deviated tonically to LEFT (RIGHT FEF in control)

no atrophy o feye muscles (LMNs intact)

no diplopia (both eyes affected equally)

Front 82

lesion of RIGHT PPRF

Back 82

eyes deviated tonically to LEFT (RIGHT PPRF in control)

no atrophy of eye muscles (LMNs intact)

no diplopia (both eyes affected equally)

Front 83

Lesion of RIGHT abducens nucleus

Back 83

both eyes directed LEFT (loss of input to ipsilateral LR and crossed in put to contralaeral MR)

atrophy of RIGHT LR

No diplopia

Front 84

Lesion of RIGHT abducens nuerve

Back 84

RIGHT eye devated medially - can't be directed laterally

atrophy of RIGHT LR

diplopia (eyes affected unequally)

Front 85

lesion of LEFT vestibular nuclei or CN VIII

Back 85

RIGHT nystagmus (right side is in control, eyes drift slowly left, fast saccade to right)

LEFT staggering gait (vestibular input to tleft spinal cord reduced relative to right side input)

Front 86

Lesion of LEFT MLF

Back 86

anterior internuclear ophthalmoplegia

can't turn LEFT eye past midline to right

No atrophy of MR

diplopia when looking to RIGHT

nystagmus when trying to look RIGHT (R. eye turns R., then snaps back to reduce diplopia)

normal vergence

Front 87

Caloric test

warm water

Back 87

warm water in ear canal --> slow drive of eyes to opp. side -- fast return to same side

(coWS)

Front 88

Caloric test

cold water

Back 88

cold water in ear canal --> slow drift of eyes to same side --> fast return to opposite side

(COws)

Front 89

pupillary light reflex

constrition

Back 89

retina --> pretectum of midbrain (bilaterally) --> Edinger-Westphal nucleus (preganglionic parasympathetic neruons of CN III) --> ciliary ganglion --> iris sphincter (and ciliary mm) (loss of accommodation accompanies loss of papillary light reflex)

Front 90

pupillary light reflex

dilation

Back 90

hypothalmic neurons --> excite neurons in upper thoracic cord

--> axons to superior cervical ganglion

--> postganglionic axons follow internal carotid and CN III fibers to brain & orbit

Front 91

Lesions affecting pupillary light reflex

Back 91

unilateral lesion of optic nerve (CN II)

unilateral lesion of pretectum

unilateral lesion of Edinger-Westphal nucleus or CN III

Front 92

Unilateral lesion of optic nerve

Back 92

abnormal direct and consensual responses following stimulation of ipsilateral eye

normal direct and consensual responses following stimulation of contralateral eye

Front 93

unilateral lesion of pretectum

Back 93

abnormal direct and consensual responses following stimulation of ipsilateral eye

normal direct and consenaul responses following stimulationof contralateral eye

Front 94

unilateral lesion of Edinger-Westphal nucleus or CN III

Back 94

abnormal direct response, normal consensual response

abnormal consenual response, normal direct response following stimulation of contralateral eye

Front 95

information handled by primary neurons of trigeminal ganglion

Back 95

pain
temperature
touch

Front 96

peripheral processes of trigeminal ganglion -->

Back 96

--> ophthalmic branch (V1)
maxillary branch (V2)
mandibular branch (V3)

Front 97

where do central processes of trigeminal ganglion terminate?

Back 97

tregeminal nucleus
(extends over entire length of brainstem)

Front 98

nuclei within trigeminal nucleus

Back 98

mesencephalic nucleus of V

chief nucleus of V

spinal nucelus of V

Front 99

mesencephalic nucleus of V

Back 99

adjacent to PAG of midbrain

proprioceptive information from muscles of mastication

cell bodies located within brainstem

peripheral processes from muscle spindles enter brainstem via V3

central processes terminate in motor nucleus of V (establishes stretch reflex for control of jaw position and bite strength)

Front 100

alternative pathway for central processes from mesencephalic nucleus of V

Back 100

cross midline to join ventral trigeminothalamic tract (VTT)
to carry proprioception info to contralateral ventral posteromedial nucleus (VPM) of the thalamus then to sensory cortex

Front 101

chief sensory nucleus of V

Back 101

discriminatory tough, conscious proprioception, vibration from face and oral cavity (MVP)

primary neurons in trigeminal ganglion

second order neurons send axons across midline to vorm VTT

second order neurons from oral cavity form dorsal trigeminothalamic tract (DTT) ipsilaterally

VTT and DTT fibers ascend to ventral posteromedial nucleus (VPM) of thalamus then to ipsilateral somatosensory cortex

Front 102

VTT

Back 102

ventral trigeminothalamic tract

ascends near medial lemniscus and anterolateral system

Front 103

DTT

Back 103

dorsal trigeminothalamic tract

second order neurons from oral cavity
carry fibers from ipsilateral side

Front 104

spinal nucleus of V

location
information handled

Back 104

caudal pons to caudal medulla

pain&temp from face, forehead, mucous mb of nose, anterior 2/3 of tongue, hard and soft palates, nasal cavities, oral cavity, teeth, portions of cranial dura

Front 105

spinal nucleus of V

pathway

Back 105

primary neuron cell bodies in trigeminal ganglion

enter brainstem at level of chief sensory nucleus

form spinal tract of V & travel caudally to spinal nucleus of V

2* neurons cross midline to VTT

VTT --> VPM --> sensory cortex

Front 106

CN VII sends pain& temp info from where to spinal nucleus of V?

Back 106

ear (geniculate ganglion)

Front 107

CN IX sends pain & temp info from where to spinal nucleus of V?

Back 107

ear
posterior 1/3 of tongue
eustacian tube
upper pharynx (gag reflex)

(superior ganglion of CN IX)

Front 108

CN X sends pain & temp info from where to spinal nucleus of V?

Back 108

ear
lower pharynx
larynx
upper esophagus

(superior ganglion of CN X)

Front 109

what CN mediates sensory limb of gag reflex?

Back 109

CN IX

Front 110

corneal blink reflex

Back 110

involves chief sensory nucleus & spinal nucleus of V

stimuli include bright lights (CN II)
loud noise (CN VIII)
direct contact with cornea (CN V)

cause closure of both eyes due to bilateral innervation of each facial motor nucleus by CN V afferents

efferent side --> CN VII (orbicularis muscle, hook that pulls lid closed)

Front 111

damage to CN VII has what effect on corneal blink reflex?

Back 111

loss of reflex from ipsilateral eye

Front 112

trigeminal neuragia

Back 112

aka: Tic douloureux

peridos of excruciating pain caused by distribution of a divisionof the trigeminal system (usually maxillary division)

pain can be relieved by cutting pain and temp fibers within spinal tract of V

Front 113

motor nucleus of V

Back 113

motor innervation to muscles of mastication

located mid-pons, medial to chief sensory nucleus of V

receives proprioceptive infor from muscles of mastication and is part of reflex loops controlling jaw position & bite strength

receives input from auditory nerve and serves output to tensor tympani to protect tympatnic membrane from loud noise (acoustic reflex)

Front 114

damage to CN V
(types of lesions)

Back 114

unilateral lesions of descending corticobulbar pathway (UMN lesion)

unilateral lesions to motor nucleus of V or mandibular division (V3)

Front 115

Unilateral lesions of descending corticobulbar pathway:

Back 115

Unilateral lesions of descending corticobulbar pathway:

don't produce clear deficits b/c each nucleus of V is bilaterally innervated from motor cortex (normal innervation from one side makes up for lesion

Front 116

Unilateral lesions to motor nucleus of V or mandibular division (V3)

Back 116

results in lower motor syndrome deficits

paralysis and slow wasting of muscles of mastication

jaw deviates to weak side upon protrusion (imbalance of pterygoid muscles)

diminished bit strength (loss of temporalis muscle)

Front 117

lesions of the trigeminal system that result in sensory deficits

Back 117

VTT lesion

VTT and adjacent AL system lesions

chief sensory nucleus lesion

spinal nucleus and tract of V lesion

spinal nucleus and tract of V, and adjacent anterolateral system lesion

damage to root of CN V

Front 118

sensory deficits associated with VTT lesion

Back 118

contralateral loss of pain, temp, discriminative touch and proprioception from head

Front 119

sensory deficits associated with VTT and adjacent AL system

Back 119

contralateral loss of pain, temp, discriminative touch and proprioception from head

contralateral loss of pian and temp from body

Front 120

sensory deficits associated with chief sensory nucleus

Back 120

ipsilateral loss of discriminative touch from head

Front 121

sensory deficits associated with spinal nucleus of tract of V

Back 121

ipsilateral loss of pain and temp from head

Front 122

sensory deficits associated with spinal nucleus and tract of V, and adjacent AL system

Back 122

ipsilateral loss of pain and temp from head

contralateral loss of pain and temp from body

lateral medullary (Wallenberg's) syndrome - vascular insufficiency of PICA

Front 123

sensory deficits associated with damage to root of CN V

Back 123

ipsilateral sensory and motor deficits from head

Front 124

general sensory component of Facial VII

Back 124

pain, temp, crude touch from external ear and auditory canal

primary neurons located in geniculate ganglion (petrous part of temporal bone)

enters brainstem via intermediate nerve

second order neurons in spinal nucleus of V send axons across midline via VTT to contralateral VPM then primary sensory cortex

Front 125

special sensory component of facial nerve

information
location of first-order neurons

Back 125

taste from anterior 2/3 of tongue

1* neurons in geniculate ganglion

Front 126

pathway of special sensory component of facial nerve

Back 126

1* neurons - geniculate ganglion

peripheral processes of CN VII travel w/ lingual branch of CN V3 w/in mandible then separate and form chorda typani

taste fibers join intermeidate nerve & general sensory fibers of CN VIII

together enter brainstem at cerebellopontine angle (pons)

2* neurons in rostral part of nucleus solitarius
--> VPM of thalmus via solitariothalmic tract (UNCROSSED)

Front 127

preganglionic parasympathetic fibers of facial nerve

Back 127

originate in superior salivatory nucleus of dorsal lateral pons

nucleus receives input from CN V, VII, IX, X (pain & temp from head) to cause tear formation and salivation

exit brainstem as part of CN VII

Front 128

after intermediate nerve of CN VII exits brainstem, it forms which two branches?

Back 128

preganglionic parasympathetics synapse in pterygopalatine ganglion --> lacrimal gland & nasal/oral mucuous mb's

OR
pregang. parasympathetics synapse in submandibular ganglion --> submandibular and sublingual salivary glands

Front 129

special visceral/brachial motor component of facial nerve

Back 129

innervate muscles of facial expression, stapedius

LMNs in motor nucleus of VII of caudal pons

UMNs in primary motor cortex
- bilateral input to region of motor nucleus that innervates forehead
- crossed input to lower face

Front 130

stapedius reflex

Back 130

from superior olivary nucleus

contraction or relaxation of stapedius muscle in response to damaging sounds

Front 131

causes of damage to CN VII

Back 131

cold temperatures

middle ear infections

tumor of fourth ventricle

surgery of parotid gland

trauma to side of face

Front 132

Clinical presentations of CN VII damage

Back 132

close assocation with CN VI and VIII - symptoms often seen together

Central facial paralysis

Bell's palsy

Front 133

Damage to CN VII is closely associated with damage to CN VI and CN VIII

Effects

Back 133

deficits in VI (lateral rectus) and VII (facial paralysis) suggest brainstem damage

deficits of VII (facial paralysis) and VIII (vestibulo-auditory deficits) suggest damage within internal auditory meatus

Front 134

central facial paralysis

Back 134

aka: central seven paralysis

unilateral damage to motor cortex or descending corticobulbar fibers in internal capsul and rostral brainstem

paralysis (no atrophy) of contralateral lower face muscles

NO functional deficits in upper face musclulature

Front 135

Bell's palsy

etiology

Back 135

injury to LMN in motor nucleus of VII or to VII itself (eg: herpes zoster in ear canal)

Front 136

Bell's palsy

symptoms

Back 136

flaccid paralysis and atrophy of ipsilateral upper and lower facial musculature
pain around ear
loss of corneal reflex
hyperacusis on affected side
loss of taste from atnerior 2/3 of tongue
loss of input to platysma

can't hold lips together, can't whistle

food in cheek b/c no buccinator activation

Front 137

Sensory deficits related to CN VII

Back 137

lesion of CN VII and lingual branch of CN V3 w/in mandible

lesion w/in chorda typani

lesion outside the stylomastoid foramen affecting only branchiomotor fibres of CN VII

lesion w/in the brainstem near the root of CN VII

Front 138

effects of lesion of CN VII and lingual branch of CN V3 w/in mandible

Back 138

loss of taste from anterior 2/3 of tongue

lack of secretion from submandibular and sublingual glands

loss of sensation from region served by lingual nerve

Front 139

effects of lesion w/in chorda tympani

Back 139

loss of taste from anterior 2/3 of tongue

lack of secretion from submandibular and sublingual glands

Front 140

effects of lesion outside stylomastoid formamen affecting only branchiomotor fibers of CN VII

Back 140

ipsilateral atrophy and paralysis of muscles of facial expression

Front 141

lesion within brainstem near root of CN VII

Back 141

loss of tast from anterior 2/3 of tongue
lack of secretion from submandibular and sublingual glands
loss of sensation from region served by lingual nerve

ipsilateral atrophy and paralysis of muscles of facial epxression

hyperacusis

dry eye

Front 142

hyperacusis

Back 142

loss of input to stapedius muscle

Front 143

vestibular nerve fibers of CN VIII

Back 143

head movement and position info from semicircular canals and otolith organs (sacule and utricle)

1* neurons in vestibular (scarpa's) ganglia

central fibers travel within internal auditory meatus w/ CN VII fibers

terminate in one of rou vestibular ncueli at brainstem

hair cell remains stationary and sterociliar are displaced by fluid movements in bondy canals - direction dependent

Front 144

Cochlear nerve fibers of CN VIII

Back 144

auditory info from cochlea

1* neurons in cochlear (spiral) ganglia
cnetral fibers travel w/in internal auditory meatus w/ CN VII fibers

terminate in dorsal and ventral cochlear nuclei at brainstem

displacement of basilar mb and hair cell body by sound waves on TM cause displacement of sterocilia - direction dependent

Front 145

auditory receptors

Back 145

hair cells of cochlea

Front 146

location of pirmary neurons of auditory nerve (CN VIII)

Back 146

cochlear (spiral) ganglion

Front 147

where do axons of auditory nerve end centrally?

Back 147

in dorsal and ventral cochlear nuclei

Front 148

2 structures that are part of auditory body in pons

Back 148

trapezoid body

superior olive

Front 149

2 auditory pathways

Back 149

(a) 1* neurons synapse on ventral cochlear nucleus --> 2* neurons travel to superior olive --> lateral lemniscus --> inferior colliculus

(b) 1* neurons synapse in dorsal cochlear nucleus --> 2* neurons travel trhough lateral lemniscus to inferior colliculus

both: from inf. colliculus --> medial geniculate nucleus --> primary auditory cortex

Front 150

what happens to auditory info in the superior olive?

Back 150

directional hearing

(minute differences in the timing and loudness of the sound in each ear are compared)

Front 151

what happens to auditory info in dorsal cochlear nucleus?

Back 151

analysis of quality of sound

e.g.: differentiates "bet" from "bat" and "debt"

Front 152

where is the medial geniculate located?

Back 152

part of thalamus

Front 153

localization of sound requires what?

Back 153

auditory info conveyed to both sides of brain

Front 154

unilateral lesion of dorsal and ventral cochlear nuclei or CN VIII -->

Back 154

deafness in ipsilateral ear

Front 155

higher level lesions in CN VIII -->

Back 155

cause only subtle auditory deficits due to bilateral input

Front 156

function of vestibular nuclei

Back 156

vestibular nuclei maintain balance and stabilize visual image on retina during movements of head

Front 157

leson s of CN VIII, vestibular nuclei and descending pathways -->

Back 157

stumbling/falling toward side of lesion

Front 158

brachial motor component of CN IX

Back 158

innervates sylopharyngeus muscle (elevate larynx and pharynx during speaking and swallowing)

LMNs in rostral part of nucleus ambiguous (rostral medulla)

Front 159

preganglionic parasympathetics in CN IX

Back 159

arise from interior salivatory nucleus
- input from hypothalamus and olfactory system

synapse on otic ganglion

innervate parotid gland

Front 160

special sensory component of CN IX

Back 160

taste (posterior 1/3 of tongue)

1* order neurons in inferior ganglion of CN IX

central processes terminat on 2* order neurons in rostral part of nucleus solitarius

Front 161

general sensory component of CN IX

Back 161

pharynx, posterio 1/3 of tongue, eustachian tube, middle ear

1* neurons in inferior ganglion of IX

2* neurons in trigeminal nucleus and go to contralateral VPM via VTT

Front 162

visceral sensory component of CN IX

Back 162

baroreceptors for BP regulation
carotid sinus travels over CN IX (1* neurons in superior ganglion)

increase in BP --> increase in CN IX activity --> 2* neurons in caudal nucleus solitarius -->

CN X slows HR
increased activation of inhibitory neurons in nucleus solitarious reduce BP by inhibiting pregang parasymps in thoracic cord

similar respons in aortic arch by conveyed to caudal nuc. solitarius by CN X

Front 163

unlilateral lesions of rostral nucleus solitarius -->

Back 163

ipsilateral loss of taste

Front 164

unilateral lesions of caudal nucleus solitarius -->

Back 164

increased HR

Front 165

higher level lesions in CN VIII -->

Back 165

cause only subtle auditory deficits due to bilateral input

Front 166

vestibular pathways

Back 166

vestibular nuclei maintain balance and stabilize visual image on retina during movements of head

Front 167

leson s of CN VIII, vestibular nuclei and descending pathways -->

Back 167

stumbling/falling toward side of lesion

Front 168

brachial motor component of CN IX

Back 168

innervates sylopharyngeus muscle (elevate larynx and pharynx during speaking and swallowing)

LMNs in rostral part of nucleus ambiguous (rostral medulla)

Front 169

preganglionic parasympathetics in CN IX

Back 169

arise from interior salivatory nucleus
- input from hypothalamus and olfactory system

synapse on otic ganglion

innervate parotid gland

Front 170

special sensory component of CN IX

Back 170

taste (posterior 1/3 of tongue)

1* order neurons in inferior ganglion of CN IX

central processes terminat on 2* order neurons in rostral part of nucleus solitarius

Front 171

general sensory component of CN IX

Back 171

pharynx, posterio 1/3 of tongue, eustachian tube, middle ear

1* neurons in inferior ganglion of IX

2* neurons in trigeminal nucleus and go to contralateral VPM via VTT

Front 172

visceral sensory component of CN IX

Back 172

baroreceptors for BP regulation
carotid sinus travels over CN IX (1* neurons in superior ganglion)

increase in BP --> increase in CN IX activity --> 2* neurons in caudal nucleus solitarius -->

CN X slows HR
increased activation of inhibitory neurons in nucleus solitarious reduce BP by inhibiting pregang parasymps in thoracic cord

similar respons in aortic arch by conveyed to caudal nuc. solitarius by CN X

Front 173

unlilateral lesions of rostral nucleus solitarius -->

Back 173

ipsilateral loss of taste

Front 174

unilateral lesions of caudal nucleus solitarius -->

Back 174

increased HR

Front 175

how CN IX and CN X area also involved in respiration control

Back 175

chemoreceptors in carotid body (IX) and aortic body (X) respond to decreases in O2 tension and increases in areterial CO2

decreased PO2 or increased
PCO2 causes increase in activity of neurons in caudal part of nucleus solitarius --> increas in activtaion of phrenic nucleus

Front 176

bilateral lesions of medulla that affect caudal nucleus solitarius -->

Back 176

major respiratory and cardiovascular problems

Front 177

General sensory component of vagus nerve

Back 177

pain, temp and touch from pharynx, larynx, esophagus, EAM, TM

1* neurons located in superior ganglion of CN X

2* neurons in trigeminal nucleus

Front 178

special sensory component of vagus nerve

Back 178

taste from epiglottis

1* neurons in inferior ganglion of X

2* order neuron in rostral part of nucleus solitarius

Front 179

visceral sensory component of vagus nerve

Back 179

baroreception/chemoreception from aortic arch

1* neurons in superior ganglion of X

Front 180

3 taste pathways

Back 180

CN VII: anterior 2/3 tongue --> geniculate ganglion

CN IX: posterior 1/3 tongue --> inferior ganglion of IX

CN X: epiglottis --> inferior ganglion of X

Front 181

taste pathway starting at nucleus solitarius

Back 181

nucleus solitarius --> VPM of thalamus --> via solitariothalamic tract (uncrossed)

Front 182

motor components of vagus nerve

Back 182

arise from nucleus ambiguus & dorsal motor nucleus of X

LMNs in nucleus ambiguous innervate striated musculature of solf palate, pharynx, larynx, upper esophagus (speech & swallowing)

visceral motor from dorsal motor nucleus of X to innervate thoracic and abdominal viscera - efferent limb in regulation of respiration, CV function and GI activity

Front 183

Gag reflex

Back 183

contraction of both sides of pharyngeal musculature

sensory info enters braintem via CN IX and X

--> distributed to neurons in spinal nucleus of V

--> trigeminal neurons project bilaterally to nucleus ambiguus

Front 184

bilateral damage to nucleus ambiguus or CN X -->

Back 184

complete laryngeal paralysis and death

Front 185

unilateral damage to nucleus ambiguus (LMN)

Back 185

atrophy and paralysis of all palatine muscles except tensor veli palatini (innervated by CN V)

hoarseness, nasal speech, dysphonia, dysphagia, loss of gag reflex

risk of nasal reguritation

uvula deviates to NORMAL SIDE

Front 186

unilateral UMN damage

Back 186

no significant effects since corticobulbar input to nucleus ambiguus is bilateral

exception--> input to LMN that innervate uvula
(deviation of the uvula SAME SIDE as lesion)

Front 187

Cranial root of accessory nerve (CN XI)

Back 187

originates from caudal part of nucleus ambiguus

join CN X outside skull to innervate straited muscles of larynx

Front 188

Spinal root of Accessory nerve (CN XI)

Back 188

originates from motor neurons in ventral horn of cervical spinal cord (C1-C5)

ascend into skull via foramen magnum

exit skull though jugular foramen with IX and X

innervates SCM and trapezius

Front 189

lesion to CN XI fibers

Back 189

weakness and atrophy of SCM and trapezius

unilateral lesion --> head directed slighly to ipsilateral side (paralyzed side), can't turn head to opposite side, sagging of ipsilateral shoulder

Front 190

UMN lesion

Back 190

no noticeable effects (bilateral input)

Front 191

what does hypoglossal nerve innervate?

Back 191

intrinsic and extrinsic muscle of tongue (except palatoglossus - CN X)

cells originate in hypoglossal nuclei (midline under 4th ventricle)

axons exit brainstem as rootlets between inferior olivary nucleus and pyramids

Front 192

hypoglossal nuclei

Back 192

receives afferent input from neurons in nucleus solitarius and trigeminal nucleus (reflexes related to chewing, sucking, swallowing)

Front 193

unilateral lesion of hypoglossal nucleus or CN XII

Back 193

atrophy and paralysis of IPSILATERAL tongue musculature

tongue deviates to side lesion

Front 194

UMN lesion affecting hypoglossal nerve

Back 194

tongue deviates to CONTRALATERAL side

dysarthria (slurring speech, thick tongue)

contralateral hemiparesis, no atrophy if lesion involves descending corticospinal fibers

Front 195

LMN damage to CN XII and adjacent corticospinal tract

Back 195

inferior alternating hemiplegia
- ipsilateral paralysis & deviation of tongue
- contralateral hemiparesis

Front 196

Vestibulococlear System

location

Back 196

petrous part of temporal bone

Front 197

Vestibulocochlear system

components

Back 197

vestibular apparatus

cochlea

Front 198

vestibular apparatus

Back 198

semicircular canals (anterior, posterior, horizoneal) --> angular acceleration (head movement)

otolith organs (utricle and saccule) --> linear acceleration (head position)

Front 199

cochlea

Back 199

Organ of Corti --> sound transduction

Front 200

Properties of sound

Back 200

transmission

pitch & intensity

sensitivity

Front 201

transmission of sound

Back 201

transmitted as disturbance of air molecules

regions of high pressure and low pressure

individual molecules don't travel far but disturbance can be passed for miles

disturbances --> sound waves that transmit sound energy to ears

Front 202

pitch

Back 202

frequency (Hz)

Front 203

intensity of sound

Back 203

amplitude (dB)

Front 204

sensitivity of sound

Back 204

detectible by humans: 20-20,000 Hz

optimal for humans: 1000 - 4000 Hz

Front 205

primary auditory structures

Back 205

auricle and EAM

TM

ossicles and middle ear

cochlea and inner ear

Front 206

auricle and EAM - function in hearing

Back 206

capture sound and direct to tympanic membrane (TM)

Front 207

tympanic membrane (TM)

Back 207

pressure-sensitive

separates external from middle ear

where sound pressure wave is transduced into mechanical motion

Front 208

ossicles and middle ear

Back 208

bones transmit energy from TM to oval window of cochlea
(1) malleus contacts TM
(2) incus - 2nd in chain
(3) stapes --> smallest, contacts oval window

sound pressure amp'd 20x by shape & arr. of ossicles and surface area ratio of TM to oval window

Front 209

sensitivity of ossicles controlled by

Back 209

tensor tympani (CN V) --> alters tension of malleus on TM

stapedius (CN VII) --> alters tension of stapes on oval

Front 210

function of eustachian tube

Back 210

balances air pressure btw middle ear and atmosphere

Front 211

primary auditory organ

Back 211

cochlea and inner ear

Front 212

3 fluid compartments of inner ear

Back 212

scala vestibuli

scala tympani

scala media

Front 213

scala vestibuli of inner ear

Back 213

separated from middle ear by oval window (initiation of fluid wave energy)

perilymph (high Na, low K)

Front 214

scala tympani of inner ear

Back 214

continuous with scala vestibuli

separated from middle ear by round window (dissipation of fluid wave energy)

perilymph (high Na, low K)

Front 215

scala media

Back 215

separated from scala vestibuli by Reissner's membrane

separated from scala tympani by Basilar membrane

endolymph (low Na, high K)

Front 216

mechanical steps in hearing

Back 216

sound pressure waves deflect TM
--> ossicle and oval window convert sound waves to fluid waves in scala vestibuli
--> pressure waves in scala vestibuli are translated to scala media via Reissner's membrane

--> movement of basilar membrane and organ of Corti (dependent on sound frequency, tonotopic org. of basilar mb)
--> sound intensity coded by amplitude of mb deflection
--> hair cells in organ of Corti (1* receptor neurons) move and distort stereocilia
--> sterocilia distorition causes either depol. or hyperpolarization

Front 217

describe proximal end (base) of basilar membrane

Back 217

stiff

sensitive to HIGH frequencies

Front 218

describe distal end (apex) of basilar membrane

Back 218

flexible

sensitive to LOW frequencies

Front 219

Electrical steps in hearing

Back 219

aka: sensory transductino by hair cells

stereocilia are in endolymph (high K)
(1) deflection toward tallest stereociliar --> opening of mechanically-gated K channels --> depol.
(2) deflection away from tallest sterocilia --> closing of K channels --> hyperpolarization

cell bodies of hair cells are in perilymph (low K)
have voltage-gated Ca channels that open during depol. to facilitate NT release

Front 220

Central auditory pathways

common through 2* neurons

Back 220

receptor cells are inner and outer hair cells or organ of Corti

1* neuron of auditory nerve are in spiral ganglion

2* neurons in dorsal and ventral cochlear nuclei of brainstem

Front 221

central auditory pathway through dorsal cochlear nucleus

Back 221

from dorsal cochlear nucleus, 2* axons cross midline and asend as lateral meniscus

terminate on 3* neurons in infeior colliculus

4* neurons in medial geniculate of thalamus

final termination on neurons in auditory cortex

Front 222

central auditory pathway through ventral cochlear nucleus

Back 222

2* axons from ventral cochlear nucleus synapse on 3* neurons in left and right superior olive

3* neurons ascend via lateral lemniscus to inferior colliculus

4* neurons from inferior colliculus project to ipsilateral medial geniculate nucleus

final termination in auditory cortex

Front 223

2 main factors encoding auditory information

Back 223

frequency determination
- place coding (neurons along path are tonotopically in register w/ receptor cells of basilar mb)

intensity determination
- firing rate
- # active neurons

Front 224

2 factors in sound localization

Back 224

horiztonal plane (requires both ears)
- low freq tones detected by interaural time delay
- determined at level of superior olive

vertical plane (unilateral input sufficient)
- interaural timing & intensity not change significantly
- pinna of ear is important

Front 225

labyrinths and fluids in vestibular apparatus (4)

Back 225

bony labyrinth

membranous labyrinth

perilymph

endolympth

Front 226

bony labyrinth of vestibular apparatus

Back 226

houses vestibular apparatus

contains membranous labyrinth

Front 227

membranous labyrinth

Back 227

closed, fluid-filled

contains sensory apparatus

Front 228

perilymph

Back 228

btw bony & membranous labyrinth

high Na, low K

bathes vestibular portion of CN VIII

Front 229

endolymph

Back 229

fills membranous labyrinth

bathes sensory receptors of auditory and vestibular systems

low Na, high K

disturbance in distribution or ionic content --> vestibular pathology

Front 230

Semicurcular canals in each vestibular apparatus

Back 230

horizontal - medial to lateral in petrous part of temporal bone
- angled 30* above horizon; become horizontal when head is tilted forward

anterior - oriented vertical and orthogonal to horizontal canal

posterior - oriented vertical and orthogonal to horizontal
- parallel to anterior canal of opposite apparatus

Front 231

Otolith organs

Back 231

linear acceleration of head/body

utricle - orientation similar to horizontal semicircular canal
- signals accelerations planar to horizon

saccule - orientation similar to ant/post semicircular canals
- signals vertical and gravitational accelerations

Front 232

Structure of semicircular canal hair cells

Back 232

ampulla of each canal

cell bodies in crista contain 80 stereocilia and one tall kinocilium
- Type 1 cells - apex of crista
- Type 2 cells - peripheral

crista and sterocilia encased in cupula (gelatinous mass)

cupula attached to roof and walls of ampulla

Front 233

general activation pathway of semicircular canal hair cells

Back 233

movement of head causes movement of endolymph --> deflection of cupula --> displacement of stereocilia and kinocilium --> depol. or hyperpolarization

Front 234

what happens with respect to horizontal semicircular canals when head turns LEFT?

Back 234

Head turns LEFT -->

depolarization of sterocilia in LEFT ampulla

hyperpolarization of sterociliar in RIGHT ampulla

Front 235

Otolith hair cells

Back 235

maculae of utricle and saccule
similar to cristae of semicircular canals
sterocilia covered w/ gelatinous mb
otolith mb has otoconia (CaCO3 Xstals) - more dense than endolymph
most sensitive to gravity and linear acceleration
receptors inactive when head is upright

Front 236

receptors of otolith hair cells

Back 236

utricle - horizontal orientatin of macula (kinocilia adjacent to striola)
- sensation of forward, backward, lateral tilt of head

saccule - vertical oritentation of macula (kinocilia distant to striola)
- sensation of gravity and vertical motion of head

Front 237

Central vestibular common pathway

Back 237

sensory receptor = hair cells (semicircular/otolith)

1* neurons of CN VIII --> scarpa's (vestibular) ganglion

2* neurons --> vestibular nuclei of brainstem

3* neurons --> targets

Front 238

vestibular nuclei of brainstem responsible for...

Back 238

nuclei responsible for coordination of visual and postural reflexes

Front 239

targest of vestibular nuclei efferents

Back 239

motor nuclei related to eye movements (III, IV, VI; nuclei communicate via MLF)

vestibulocerebellum
spinal cord
reticular formation
thalamus
contralateral vestibular nuclei

Front 240

vestibular nuclei receive proprioceptive info from...?

Back 240

spinal cord

Front 241

which tracts carry proprioceptive info to vestibular nuclei

Back 241

lateral and medial vestibulospinal tracts

Front 242

lateral vestibulospinal tract - function

Back 242

muscle tone for postural adjustments of body

Front 243

medial vestibulospinal tract - function

Back 243

muscle tone for righting of head

Front 244

disturbances of vestibulocochlear system

Back 244

acoustic neuroma

vascular disturbances

vestibular deficits

cochlear deficits

Meniere's disease

Front 245

Acoustic neuroma

Back 245

most common cause of damage to VIII

derived from schwann cell that myelinates VIII

often affects auditory and facial nerve (VII)

Front 246

Vascular distrubances of vestibulocochlear system

Back 246

blockage of labyrinthine artery (branch of AICA)

vestibular, auditory and facial function can be affected

Front 247

Vestibular deficits

Back 247

dizziness

nausea

loss of balance

unstable gait

Front 248

Cochlear deficits

Back 248

tinnitus

loss of hearing

Front 249

Meniere's disease

Back 249

abnormal endolymph volume --> distention of membranous labyrinth

vertigo
nystagmus
nausea
tinnitus
unstable posture and gait
swelling reduced w/ diuretic, low salt diet, shunt to drain excess fluid

Front 250

Major components of mammalian visual system

Back 250

retina
dorsal lateral geniculate nucleus of thalamus (dLGN)
striate cortex
superior colliculus
pretectum
suprachiasmic nucleus of hypothalamus

Front 251

retina

Back 251

neural tissue for light capture and image processing

photoreceptors - input neurons

ganglion cells - output neurons (from optic nerve and tract)

Front 252

dorsal lateral geniculate nucleus of thalamus

Back 252

multi-layered nucleus, primary target for retinal axons

axons of LGN neurons project to striate cortex

Front 253

striate cortex

Back 253

primary target for LGN neuron afferents

neurons organized into columns of ocular dominance and orientation selectivity

visual info relayed to surrounding areas for additonal processing

Front 254

superior colliculus

Back 254

layered structure in midbrain

input from large retinal ganglion cells

orients movements of head and eyes (visual reflexes of head)

Front 255

pretectum

Back 255

just rostral to tectum

reflexive control of pupil and lens

Front 256

suprachiasmic nucleus of hypothalamus

Back 256

dorsal to optic chiasm

regulation of circadian rhythms

Front 257

Layers of eye

Back 257

sclera - tough outer covering - support and protection

choroid - middle vascular layer - supplies outer retina, ciliary body, iris

retina - light sensitive, neural component - occupies posterior 2/3 of eye

Front 258

chambers of eye

Back 258

anterior - btw cornea and pupil, aqueous humor

posterior - btw pupil and lens, aqueous humor

vitreal - posterior to lens, vitreous humor

Front 259

refractive elements of eye

Back 259

cornea

lens

ciliary body

Front 260

cornea

Back 260

modified sclera

avascular

optically clear

site of pirmary refraction

Front 261

lens

Back 261

avascular

optically clear

greater curvature --> incrased refractive power

Front 262

ciliary muscle/body

Back 262

anchors lens via suspensory ligaments

provides accommodation via parasympathetic innervation (III)

Front 263

light control - 2 structures

Back 263

iris

pupil

Front 264

how does iris function in light control

Back 264

iris - highly vascular, pigmented

pupillary dilation - sympathetic innervation fo radial muscles (superior cervical ganglion)

pupillary constriction - parasympathetic innervation of iris constrictor muscle (CN III)

Front 265

where does sympathetic innervation for iris come from

Back 265

postganglionic sympathetics in superior cervical ganglion

Front 266

where does parasympathetic innervation for iris come from

Back 266

parasympathetics in CN III

Front 267

retinal landmarks

Back 267

optic disc - blind spot - entry/exit for inner retina vessels & exit point of axons

fovea - pit in central retina - only cone photoreceptors - high visual acuity due to small neurons and one-to-one synaptic connections

Front 268

blood supply to inner retina

Back 268

central retinal artery and vein (from ophthalmic artery)

Front 269

blood supply to outer retina

Back 269

long and short posterior ciliary arteries, vorticose veins

Front 270

fluids of the eye

Back 270

vitreous humor

aqueous humor

Front 271

vitreous humor

Back 271

gelatinous mass in posterior region

relatively static

Front 272

aqueous humor

Back 272

ultra-filtrate of blood in anterior and posterior chambers

provides nutrients & removes metabolites from lens/cornea

released from ciliary processes --> exits posterior chamber via pupil --> circulates in anterior chamber --> resorbed into venous system via trabecular meshwork & canal of Schlemm

balanced inflow/outflow maintains pressure at 16 mmHg

decreased outflow --> in creased risk for glaucoma

Front 273

factors affecting image quality

Back 273

light intensity
cloudy optical media
uveitis
retinal disease
astigmatism
presbyopia
hyperopia
myopia

Front 274

causes of cloudy optical media

Back 274

corneal infection

cataract

Front 275

uveitis

Back 275

inflammation of iris, ciliary body, choroid

Front 276

4 types of retinal disease

Back 276

macular degeneration

glaucoma

diabetic neuropathy

retinitis pigmentosa

Front 277

astigmatism

Back 277

assymetric curvature of cornea

Front 278

presbyopia

Back 278

loss of accommodation with age

Front 279

hyperopia

Back 279

farsightedness

corrected with convex lens

Front 280

myopia

Back 280

near sightedness

corrected with concave lens

Front 281

primary neuronal components of retina

Back 281

direct pathway:
- photoreceptors --> bipolar cells --> ganglion cells --> LGN --> visual cortex

indirect pathway:
- photoreceptor --> horizontal/bipolar cells --> amacrine cells --> ganglion cells

Front 282

retinal layers

Back 282

pigment epithelium
outer nuclear layer
outer plexiform layer
inner nuclear layer
inner plexiform layer
glanglion cell layer
nerve fiber layer

Front 283

pigment epithelium of retina

Back 283

contains melanin

metabolic support for photoreceptors

reduces light back scatter

Front 284

outer nuclear layer of retina

Back 284

location of photoreceptor cell bodies

Front 285

outer plexiform layer of retina

Back 285

site of photoreceptor-biplor-horizontal cell synaptic connection

Front 286

inner nuclear layer of retina

Back 286

location of horizontal, bipolar and amacrine cell bodies

Front 287

inner plexiform layer of retina

Back 287

site of bipolar-amacrine-ganglion cell synaptic connections

Front 288

ganglion cell layer of retina

Back 288

location of retinal ganglion cells (output)

Front 289

nerve fiber layer of retina

Back 289

unmyelinated axons of retinal ganglion cells

(myelination starts just posterior to optic disk)

Front 290

Glial cells of the retina

Back 290

Muller cells - primary glia of retina
- end feet form inner and outer limiting membranes of retina
- maintain retinal homeostasis (Glu/K/Ca control)

Microglia

astrocytes (associated w/ vasculature)

Front 291

types of photoreceptor cells

Back 291

rods

cones

Front 292

rods

Back 292

rectangular
sensitive to low levels of light (scotopic/dark to mesopic/starlight)
high convergence (many inputs to single bipolar cell)
low spatial resolution
low density in fovea
achromatic

Front 293

cones

Back 293

cone-shaped
high sensitivity w/in mesopic to photopic range
low convergence
high spatial resolution
high density in fovea
trichromatic (short/blue - medium/green - long/red)

Front 294

phototransduction

Back 294

converstion of light to electrical signals

pigment in disc mb absorbs photon
--> activation of G protein
--> increased cGMP phophodiesterase (PDE)
--> reduced levels of cGMP in photoreceptor outer segment
--> closing of cGMP-dependent Na+ channels in cell mb
--> hyperpolarization of photoreceptor
--> reduction in amount of Glutamate NT released by receptor

Front 295

what happens to photoreceptors' distal disks after activation

Back 295

photoreceptors shed distal disks after activation

new disk is added to proximal end

pitment epithelium removes discarded disks - ergo, close association btw pigment epithelium and photoreceptor outer sements

Front 296

3 types of bipolar cells

Back 296

rod bipolar

ON cone bipolar

OFF cone bipolar

Front 297

rod bipolar cell

Back 297

depolarize in response to light

do not contact ganglion cells directly - first activate rod amacrine cell that -->
--> inhibitory (glycine) NT synapse with OFF ganglion cells
-->electrical excitatory synapse with ON ganglion cells

Front 298

ON cone bipolar cell

Back 298

increase activity as illumination increases

form synaptic connections with ON ganglion cells in inner plexiform layer

optimal stimulus for ON bipolar/ganglion cell = light positioned spatially in cell's receptive field center

Front 299

OFF cone bipolar cell

Back 299

increase activity as illumination decreases

form synaptic connections w/ OFF ganglion cells in inner plexiform layer

optimal stimulus for OFF bipolar/ganglion cell --> stimulus darker than background

(movement of dark spot to surroundings decreases response)

Front 300

receptive field organization

Back 300

photoreceptors --> uniform field

bipolar/ganglion cells --> antagonistic center-surround

Front 301

antagonistic center-surround of bipolar/ganglion cells

Back 301

generated by lateral inhibition at level of photoreceptor-horizontal-bipolr synaptic arrangement within outer plexiform layer (OPL)

provides visual system with ability to detect spatial contrast

important for detection of edges and borders

Front 302

spatial contrast

Back 302

comparison of the amount of light hitting a certain area of the retina with the average amount falling on the immediately surrounding area

Front 303

amacrine cells

Back 303

wide-spreading dendritic processes

impose temporal modulation to ganglion cell responses
sustained response

involved in detection of movement and analysis of direction of movement

Front 304

4 ways that amacrine cells impose temporal modulation to ganglion cell responses

Back 304

sustained response - ganglion cell maintains activity as long as stimulus is present

transient response - ganglion cell shows initial change in activity, but rapidly returns to baseline even though stimulus is still present

linear spatial response - ganglion cell only response to particular phase (light/dark) of a stimulus that is change w/ time

non-linear spatial response - ganglion cell responds to change in stimulus phase, rather than a preference for one phase or the other

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ganglion cells

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output neurons

located near inner surface of retina in ganglion cell layer

axons (unmyelinated) course surface of retina to exit at optic disc

3 classes: midget, parasol, small-field bistratified

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midget ganglion cells

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80% of total

aka: P cells (axons project to neurons in paravocellular layers of LGN)

small cell bodies, v. compact dendritic trees

highest density is in foveal region

form one to one synaptic cxns w/ bipolar cells in fovea

involved w/ high spatial resolution analysis

chromatic - provide red-green sensitivity

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parasol ganglion cells

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10% of total

aka: M cells (axons project to neurons in magnocellular layers of LGN)

large cell bodies, wide-spreading dendritic trees

uniformly distributed across retina

low spatial resolution

high temporal resolution (motion analysis)

achromatic

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small-field bistratified ganglion cells

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5-8% of total

large cell bodies, medium sized dendritic trees

uniformly distributed across retina

spatial/temporal properties unknown

chromatic - shortwave/blue sensitivity

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central visual pathway

outline

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retina --> dorsal lateral geniculate nucleus (dLGN) --> primary visual cortex

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True or False: Retinal axons form no synapses prior to reaching higher brain centers.

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TRUE

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pathway of retinal axons from retina to higher brain centers

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optic nerve (btw optic disc and optic chiasm)

optic chiasm (near pituitary, fibers from nasal retina of each eye corss and project to opp. side of brain)

optic tract (btw optic chiasm and higher brain targets)

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2 projections comprising pathway of retinal axons

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retino-geniculate projection

geniculo-cortical projection

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spatial organization of the eye

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retina divided into hemi-retinae and quadrants by vertical meridian and horizontal meridian

vertical meridian --> nasal and temporal hemi-retinae

horizontal meridian --> superior and inferior hemiretinae

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visual world as seen by each eye

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visual field - amount of visual space seen by each eye

lens inverts visual world in nasal-temporal and superior-inferior directions

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visual world as seen by both eyes

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binocular visual field - 2/3 of visual space is seen by neurons in both eyes

monocular visual fields - most lateral regions of visual space (viewed by most nasal part of each retina)

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organization of the retinogeniculate projection

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axons of ganglion cells in nasal hemi-retina of each eye cross at level of optic chiasm and project to LGN on contralateral side

axons of ganglion cells in tmeporal hemiretina of each eye project ipsilaterally

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True or False: retinal information from each eye is still separated at LGN?

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TRUE

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magnocellular (M cell) layers

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ventral layers 1 and 2

contain large neurons

retinal input from parasol reticular ganglion cells

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parvocellular (P-cell) layers

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dorsal layers 3 through 6

contain small neurons

retinal input from midget ganglion cells

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projection pattern of small-field bistratified ganglion cells

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thin, interlaminar regions of nucleus

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pathway by which visual world is "retinoptically" represented within central visual pathway

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adjacent points in visual space
--> adjacent point on retina
--> adjacent points in LGN
--> adjacent points in visual cortex

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geniculo-cortical projection

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axons of LGN relay neurons carrying visual information from LGN to primary visual cortex (2nd synaptic site in central visual pathway)

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optic radiations

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fiber bundles comprising the geniculo-cortical projection

fibers carrying info from superior visual field (inferior retina) --> ventral --> lower bank of calcarine fissure

fibers carrying info from inferior visual field (superior retina) --> dorsal --> upper bank of calcarine fissure

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retinoptic organization with respect to geniculo-cortical projection

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central retina --> caudal pole of occipital lobe

peripheral retina (nasal or temporal) --> rostral pole of occipital lobe

superior visual fields (lower retina) --> lower bank of calcarine fissure

inferior visual fields (upper retina) --> upper bank of calcarine fissure

left visual world --> right visual cortex

right visual world --> left visual cortex

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Lesion of RIGHT optic NERVE -->

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loss of vision in RIGHT eye

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Lesion of OPTIC CHIASM (only crossed fibers) -->

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bitemporal hemianopsia (tunnel vision)

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Lesion of RIGHT optic TRACT -->

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contralateral homonymous hemianopsia

'(affected fibers: nasal retina of left eye and temporal retina of right eye)

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Lesion of optic radiation fibers in Meyer's loop (right lower quadrant of each eye) -->

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contralateral superior quadrantanopia (one quadrant)

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Lesion of upper bank of calcarine fissure -->

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contralateral inferior quadrantanopia

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lesion of lower bank of calcarine fissure -->

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contralateral superior quadrantanopia

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Lesion of uppr and lower banks of calcarine fissure -->

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contralateral hemianopsia with macular sparing (central vision intact)

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damage to macula -->

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loss of central vision

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termination pattern of geniculo-cortical axons

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axons of geniculate neurons terminate in layers IV and VI of visual cortex

Stria of Gennari --> dense termination in layer IVc

ocular dmoinance columns --> eye specific bands of segregated info in cortex

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receptive field organization of cortical neurons

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geniculo-cortical axons enter visual cortex and form synaptic contacts with stellate cells in layer IVc

stellate cells have antagonistic ON/OFF center-surround organization

stellate neurons activate cortical neurons outside IVc that prefer stimuli that differ wrt orientation, length, direction of movement

cells of like orientation preference reside in discrete cortical columns

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3 types of stellate neurons

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simple

complex

hypercomplex

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how are cortical neurons of like orientation preference arranged?

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in discrete cortical columns

columns are arranged orthogonal to ocular dominance columns and orientation preferences of adjacent columns are sequential through 180*

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higher order processing w/in visual cortex

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visual neurons in retina, LGN, layer IVc are monocular

information from monocular neurons converges on layers II, III, IVb --> binocular neurons (depth perception)

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what is the only region in the brain that demonstrates binocularity?

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visual cortex

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serial vs. parallel processing of visual stimuli

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parasol ganglion cells and M cell pathway = "where is it"

midget ganglion cells and P cell pathway = "what is it" and color

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pathway from visual info entering cortex to

motion

form/color

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visual info entering cortex activates neurons in primary visual cortex (V1, area 17)

--> extrastriate cortex
- visual signals usually sent via either dorsal or ventral stream for extrastriate processing

dorsal stream - medial temporal area (motion)

ventral stream --> inferior temporal cortex (form and color)