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The <b>rubrospinal tract</b> crosses at which level?

Midbrain

Lateral corticospinal tract decussates at which level?

in the 1/3 of the medulla (AKA <b>caudal</b> medulla.

The ______________ tract is the dominant UMN tract, especially for skilled voluntary movements of the upper limbs.

Lateral corticospinal tract

Name three tracts that are part of <b>extrapyramidal motor system</b>.

1. <b>Rubrospinal</b> tract - from red nucleus of the <b>midbrain</b>
2. <b>Vestibulospinal</b> tract- from <b>vestibular</b> nuclei of <b>brain stem</b>
3. <b>Reticulospinal</b> tract- from reticulospinal nuclei of <b>brain stem</b>.

A change in response of muscle to electrical stimulation is the result of:

a. UMN damage
b. LMN damage

b. LMN damage

In an UMN damage, there is No change in response of muscle to electrical stimulation since muscle is <b>still innervated</b>.

<b>Flaccid</b> muscle paralysis is associated with:

a. UMN damage
b. LMN damage

b. LMN damage

Rapid, neurogenic type of muscle atrophy, also referred to as denervation atrophy

<b>spastic</b> muscle paralysis is associated with:

a. UMN damage
b. LMN damage

a. UMN damage

Slow disuse type of muscle atrophy

Increased or exaggerated deep tendon reflex is associated with:

a. UMN damage
b. LMN damage

a. UMN damage

(+) Babinski sign and (+) Hoffman's sign are associated with:

a. UMN damage
b. LMN damage

A. UMN damage

also:
(-) <b>cremasteric</b> reflex
(-) <b>abdominal</b> reflex

If fibriliation potentials are present, the damage is most likely:

a. UMN damage
b. LMN damage

b. LMN damage

Romberg's test

Test used to establish neurological function in which the person is asked to close his or her eyes and place their feet together. This test for body balance is positive if the patient sways when the eyes are closed. (<b>proprioception loss</b>)

Protopathic pathway

• Pain & temperature sensations
• <b>Mutlisynaptic</b> (low fidelity)
• Spreads into other systems including<b>Ascending reticular activating system, ARAS,</b> (for arousal) and <b>limbic system</b> (for emotion and sympathetic responses)
• Pathway crosses at <b>Spinal cord</b> level via anterior commissures.

Epicritic pathway

• Discriminative Senses (two-point tactile discrimination, vibration sense and conscious proprioception.)
• Few synapses, faithful transmission (high fidelity)
• Pathway crosses in <b>brain stem</b> (caudal medulla) via sensory decussation (decussation of medial leminscus)

Intermediate pathway

• Light touch sensation
• Has features of both protopathic and epicritic pathway
• Pathway crossed and uncrossed.

The protopathic pathway is associated with which tract?

spino.thalamic tract

Periaqueductal gray of midbrain (<b>Central gray</b>)

The tegmental gray matter that is located around the cerebral aqueduct; it plays a role in the suppression of pain and in defensive behavior.

Substantia gelatinosa

The tip of the dorsal horn. This region receives <b>collaterals</b> of the <b>smallest-diameter</b> myelinated (group A delta) and unmyelinated (group C) afferents that are associated with nociception.
These neurones are excitatory and use <b>glutamic acid </b>and the <b>peptide substance P</b> as neurotransmitters.
In the substantia gelatinosa, complex interactions occur with other types of afferent terminal, interneurones, and with <b>descending</b> pathways from the brain, which control the transmission of pain information to ascending spinothalamic and spinoreticular tract neurones distributed throughout the dorsal horn.

nucleus raphe Magnus

The main function of the magnus is mostly <b>pain mediation</b>; in fact it sends projections to the <b>dorsal horn</b> of the spinal cord to directly inhibit pain. The raphe magnus nucleus releases <b><u>enkephalin</u></b> when stimulated.

The <i>periaqueductal gray</i>, the epicenter of analgesia, sends efferent connections to the nucleus raphe magnus in when it is stimulated by <i>opiates</i> (endogenous or otherwise).

Lesioning the <b>lateral spinothalamic</b> tract on one side, results in loss of pain and temperature from the ______ side.

a. ipsilateral
b. contralateral

b. contralateral

(T/F) due to a lesion of <b>lateral spinothalamic tract</b> at the level of C5, the patient loses the sensation of pain and temperature from C5 down.

False. its actually from C6 down. this is due to <b>spreading of the pain transmission up and down one level.</b>

Cordotomy

procedure that severs a spinothalamic nerve tract (protopathic pathway) within the spinal cord to relieve intractable pain.

Syrinx

A fluid filled cavity

Syringomyelia

is a cavitation of the spinal cord causing <i><u><b>bilateral </b></u></i>loss of pain and temperature <b>at the level of the lesion</b>. More common in <b>cervical and upper thoracic</b> region.

Functions of <b>tegmentum</b>

1. Levels of consciousness and alertness
2. Awareness and spreading of pain (ARAS)- <u>innervates with protopathic pathway</u>.
3. Movement through upper motor neuron reticulospinal tracts
4. Automnomic functions (cardiovascular, respiratory)

note: Tegmentum is a general area within the brainstem. It is located between the ventricular system and distinctive basal or ventral structures at each level. It forms the floor of the midbrain whereas the tectum forms the ceiling.

how many synapses are in <b>epicritic pathway</b>?

3

Fasciculus gracilis

one of the sensory tract located in the dorsal column of the spinal cord which carries <b>descriminative</b> sensory information (epicritic pathway) from the lower limbs to the caudal medulla.

Fasciculus cuneatus

one of the sensory tract located in the dorsal column of the spinal cord which carries <b>descriminative</b> sensory information (epicritic pathway) from the <b>upper</b> limbs to the caudal medulla.

damage to the dorsal columns will most likely impair:

a. sensation of pain and temperature
b. the ability to detect vibration
c. the ability to voluntarily move your limbs
d. the deep tendon reflex.

b. the ability to detect vibration

(T/F) both protopathic AND epicritic pathways synaps in thalamus.

True

Tabes Dorsalis

» <b>Degeneration</b> of dorsal columns and dorsal roots due to <i>tertiary</i> syphilis.

<b>»Signs:</b>
• <b>Impaired proprioception</b> and locomotor ataxia. Charcot's joints, shooting lightning pain in the legs.
• <u>muscle power IS NORMAL</u>
• (-) Patelar reflex
• (-) Achilles reflex
• (+) Romberg sign → dorsal column disease

How can Cerebral disease be differentiated from Dorsal column disease?

<b>positive</b> Romberg's sign is an indication of Dorsal Column Disease

Amyotrophic Lateral Sclerosis (Lou Gehrig's disease)

thickening of tissue in the motor tracts of the lateral columns and anterior horns of the spinal cord. It involves both <b>LMNs</b> and <b>UMNs</b>.

How is light touch sensation transmitted to the cortex?

Light touch sensation from one side of the body are transmitted to higher levels on both sides of the spinal cord via:
» <u>the dorsal column</u> (on same side as stimulation).
» <u>ventral spinothalamic tract</u> (on side opposite to stimulation)

(T/F) Localized injury to one side of the spinal cord does NOT usually lead to the loss of light touch sensation.

True

how many neurons are involved in the intermediate pathway.

Depends:

3 for dorsal column pathway
2 for vental spinothalamic pathway

Brown-sequard syndrome

Damage to <b>half</b> of spinal cord which is associated with loss of pain and temperature sensation on <u>contralateral</u> side of body and loss of proprioception and discriminatory touch on <u>ipsilateral</u> side of body.

include damage to:
a. lateral corticospinal tract → ipsilateral UMN spastic paralysis
b. dorsal column → ipsilateral loss of epicritic sensation
c. Lateral spinothalamic tract → contralateral loss of pain and temperature

Poliomyelitis

Infalammatory viral infection, primarily destroys <b>LMNs</b> in the ventral horn, results in muscle weakness, flaccid paralysis, fibrillations, etc.

LMNs are also affected in <i>progressive infantile muscular atrophy (Werding-Hoffman disease) </i>and <i>Guillain Syndrom (postinfectious polyneuritis).</i>

Anterior Spinal Artery Occlusion

Damage to ventral two thirds of the spinal cord, usually spares the dorsal column and dorsal horn.

Iodine-Starch test is used for

Detection of Horner's syndrome

The signs of Horner's Syndrome are often:

a. ipsilateral
b. contralateral

a. ipsilateral

» drooping (ptosis, upper eyelid)
» Mitosis, constricted pupil
» Anhidrosis, [loss of sweating], face

Honer's Syndrome

Occurs due to disruption of <b>reticulospinal fibers</b> descending in the cord to activeate <i>preganglionic sympathetic</i> neuons in the <i>intermediolateral </i>cell column.

In the spinal cord damage, if the damage is below ___ then the upper limb will be spared. Damage to ___ or above will cause involvement in both the upper and lower limbs.

T1

Sympathetic nerves going to <b>face and orbits</b> are at which level?

T1-T3

Which CNs are purely motor? (5)

✓ CN 3 → Oculomotor n
✓ CN 4 → Trochlear n.
✓ CN 6 → Abducens n.
✓ CN 11 → Accessory n.
✓ CN 12 → Hypoglossal n

What is the only Purely sensory CN?

CN 8

Nucleus location: medulla (some pons)

CNs that are mixed (4)

✓ CN 5 → Motor nucleus of V
✓ CN 7 → Facial motor n.
✓ CN 9 → Nucleus ambiguus
✓ CN 10 → Nucleus ambiguus

Which of the following is the only purely motor parasympathetic CN?

a. CN3
b. CN 7
c. CN 9
d. CN 10

a. CN3 <span style="color: #ff0000;">✓</span>
b. CN 7
c. CN 9
d. CN 10

Which of the CNs have nucleus in the pons?

1. CN 6
2. CN 5
3. CN 7

Gag reflex and Carotid reflex are associated with which segment of brain stem?

medulla

Afferent sensory fibers (CN IX)
Efferent motor fibers (CN X)

(T/F) Medial lamniscus tract can only be found in the medulla.

False. Also in pons

__________are structures in the brainstem that carry and receive visceral sensation and taste from the facial (VII), glossopharyngeal (IX) and vagus (X) cranial nerves.

fasiculus and nuclues salitorius

geniculate ganglion

where the parasympathetic cell bodies of the facial nerve fibers are located

damage to which CN leads to loss of taste from the anterior 2/3 of tongue?

Facial

The abducens nucleus and facial nucleus are just anterior to what structure?

Facial colliculus

Thus compression of this structure leas to:
1. 6th nerve palsy (LMN)
2. Damage to <span style="color: #ff0000;">LMN</span> portion of Cn. 7
» Paralysis of muscles of facial expression
» can NOT close eye
» Bell's phenomenon
» Hyperacusis
» dysfunction of corneal reflex

Palsy

loss of the ability to move a body part.

Bell's palsy could be caused by compression of _________.

Facial colliculus

Damage to the base of pons can cause which of the following?

a. Bell's phenomenon
b. hyperacusis
c. medial strabismus (eye turns inward)
d. paralysis of the entire body.

a. Bell's phenomenon
b. hyperacusis
c. medial strabismus (eye turns inward) ✓
d. paralysis of the entire body. ✓

Damage to base of pons:
damage to 6th nerve (paralysis) and UMN of pyramidal tract (corticospinal fibers)

A patient has the following symptoms.

✓ Paralysis of facial muscles

The patients hearing and balance is normal as well as eye movement.

where is the site of damage?

it would be a <b> Bell's palsy</b>

which indicates damage at the </b>stylomastoid foramen</b>.

A patient has the following symptoms.

✓ disruption of balance and hearing
✓ inability to close his eyes
✓ dry eye (xerophalmia)
✓ Xerostomia
✓ Loss of taste from the anterior 2/3 of the tongue

Patient's eye movements are normal.

where is the site of damage?

The patient has <b>acoustic neurinoma</b> which means the site of damage should be in the internal auditory meatus. The damage to the facial nerve can compress CN VIII and cause the symptoms of balance and hearing

✓ disruption of balance and hearing (VIII damage)
✓ inability to close his eyes (VII damage)
✓ dry eye (xerophalmia) (VII parasympathetic damage)
✓ Xerostomia (VII parasympathetic damage)
✓ Loss of taste from the anterior 2/3 of the tongue (VII sensory damage)

Which of the following can cause <u>6th nerve palsy</u>.

a. damage to the base of pons
b. damage to the abduncet nerve
c. compression of facial colliculus
d. Inflammation of internal auditory meatus
e. fracture of stylomastoid foramen

a. damage to the base of pons → ✓
b. damage to the abduncet nerve → ✓
c. compression of facial colliculus → ✓
d. Inflammation of internal auditory meatus → <span style="color: #ff0000;">Acoustic neurinoma</span>
e. fracture of stylomastoid foramen → <span style="color: #ff0000;">Bell's palsy</span>

A patients displays all the symptomes associated with facial nerve damage except hyperacusis. explain.

This is because the damage was most likely in the internal acustic meatus which means CN 8 was also damaged and therefore it is impossible to have hyperacusis if there is no hearing.

Bell's phenomenon

- when patient can't close eye, and the eyeball rolls upwards and outwards. occurs due to damage to cranial n. 7

Which nucleus is associated with parasympathetic activity of CN 7? which is associated with LMN activity of it?

Parasympathetic → Superior salivatory nucleus
LMT → Facial nucleus

This nucleus and its tract are associated with receiving general sensory information as well as pain and temperature in the brainstem.

Spinal tract of V

Wallenbergs

• <b>lateral</b> medullary lesion caused by <b>posterior inferior cerebral artery (PICA) occlusion,
• causes:
→ contralateral pain/temp deficits in body (damaged spinothalamic tract)
→ ipsilateral pain/temp deficit in face (damaged spinal tract V) → dysphagia (damaged nucleus ambiguus),
→ vestibular dysfunction (Vestibular nucluei)
→ ipsilateral Horner (reticulospinal fibers)

The sensory information of taste from the anterior 2/3 of the tongue enters which nuclues?

Nucleus solitarius in the caudal third of the pons.

The nucleus for what 2 cranial nerve is located at the same level as middle cerebellar peduncles ?

Facial (7) and abducent (6)`

The jaw jerk reflex or the masseter reflex is a reflex used to test the status of a patient's _________ nerve.

trigeminal (CN 5)
• It's a deep tendon reflex.

(+) Masseter reflex - UMN damage

Trigeminal nuclei (4)

★ Mesencephalic nucleus (pons/midbrain)
★ Cheif sensory nucleus V (pons)
★ Nucleus of spinal tract V (pons/medulla/spinal cord)
★ Motor nucleus of V (pons)

The cell bodoes for fibers in the <span style="color: #ff0000;">motor root</span>) branch of trigeminal are located in:

1. Motor nucleus → muscles of mastication

also included in V₃ are the <b>sensory fibers</b> that take <b>propioception from temporomandibular joint</b> to the <b><span style="color: #ff0000;">mesencephalic nucleus of V</span></b>. ★ It is also the <u>only</u> structure in the CNS to contain the cell bodies of a <b>primary afferent</b>, which are usually contained within ganglia (like the trigeminal ganglion).★

Which trigeminal nucleus is invovled in <b>massater reflex</b>?

1. Mesencephalic nucleus of V
2. Motor nucleus of V

Sensory neurons of the trigeminal mesencephalic nucleus sending axons to the trigeminal motor nucleus, which in turn innervates the masseter.

The cell bodies for fibers that carry tactile discrimination, light touch, pain and temperature of the face to the can be found in:

trigeminal ganglion

Which of the following is associated with the two-point tactile discrimination coming from the face?

a. trigeminal ganglion
b. sensory root
c. chief sensory nucleus of V
d. spinal tract of V
e. <u>dorsal</u> trigemino-thalamic tract
f. <u>ventral</u> trigemino-thalamic tract

a. trigeminal ganglion ✓
b. sensory root ✓
c. chief sensory nucleus of V ✓
d. spinal tract of V
e. <u>dorsal</u> trigemino-thalamic tract ✓
f. <u>ventral</u> trigemino-thalamic tract ✓ ★

★ receives fibers from the contralateral side. Therefore the two-point tactile discrimination sensation from one side is travels on <span style="color: #ff0000;">both</span> sides.

Which of the following is associated with the light touch sensation coming from the face?

a. trigeminal ganglion
b. sensory root
c. chief sensory nucleus of V
d. spinal tract of V
e. <u>dorsal</u> trigemino-thalamic tract
f. <u>ventral</u> trigemino-thalamic tract

a. trigeminal ganglion ✓
b. sensory root ✓
c. chief sensory nucleus of V ✓
d. spinal tract of V ✓
e. <u>dorsal</u> trigemino-thalamic tract ✓
f. <u>ventral</u> trigemino-thalamic tract ✓

Which of the following is associated with the pain and temperature sensation coming from the face?

a. trigeminal ganglion
b. sensory root
c. chief sensory nucleus of V
d. spinal tract of V
e. <u>dorsal</u> trigemino-thalamic tract
f. <u>ventral</u> trigemino-thalamic tract

a. trigeminal ganglion ✓
b. sensory root ✓
c. chief sensory nucleus of V
d. spinal tract of V ✓
e. <u>dorsal</u> trigemino-thalamic tract
f. <u>ventral</u> trigemino-thalamic tract

the two-point tactile discrimination and light touch information from the face synaps in _______ nucleus of V in middle 1/3 of pons and then travel up to ____ through __________ and ____________.

The two-point tactile discrimination and light touch information from the face synaps in <b>chief sensory nucleus of V</b> in middle 1/3rd of pons and then travel up to <b>ventral posteromedial nucleus of thalamus</b> (VPM) through <b>dorsal</b> and <b>ventral</b> trigeminothalamic tracts.

(T/F) only pain and temperature sensations from the face reach the thalamus bilaterally.

False.

Which of the following from the <b>face</b> reach the thalamus (VPN) bilaterally?

a. two-point tactile discrimination
b. light touch
c. pain and temperature

a. two-point tactile discrimination ✓
b. light touch ✓
c. pain and temperature

pain and temperature → descends <b>ipsilaterally</b> in the spinal tract of V eventually synapsing in the <span style="color: #ff0000;">nucleus of the spinal tract of V</span> → ascends <b>contralaterally</b> to thalamus in ventral trigeminothalamic tract.

A lesion in the <b>ventral</b> trigeminothalamic tract will cause:

» Contralateral loss of pain and temperature

which sensation is NOT associated with trigeminal ganglion?

a. two-point tactile discrimination
b. light touch
c. proprioception
d. pain and temperature

c. proprioception (is associated with mesencephalic nucleus)

★ Also travels to thalamus bilaterally!

Obex

Position at which the fourth ventricle empties into the central canal of the caudal medulla.

What CNs have sensory preganglionic neurons synapsing in the <b>nucleus of spinal tract of V</b>?

CN 5, 7, 9 and 10

★ additional pain and temperature information from the
head enters the spinal tract of V from the cranial nerves
7,9,10.

What is the extend of <b>nucleus of spinal tract</b>?

from medulla/pons border down to C4

Neuralgia

acute spasmodic pain along the course of one or more nerves

The spinal tract of V fibers from the light touch turn off and synaps in nucleus of spinal tract of V ______ the obex.

a. above
b. below

a. above

Corneal reflex

Afferent limb → spinal tract of V
Interneurons → Nucleus of spinal tract of V
Efferent limb → facial nuclei

Damage to the <b>motor root of V</b> results in <span style="color: #ff0000;">ipsilateral</span> LMN paralysis of the muscles of mastication, causing deviation of the mandibule to the paralyzed side. Why?

because of unopposed action of intact pterygoid muscles.

Tic Douloreux

Stabbing pain over branches of the trigeminal nerve.

<u>Surgical treatment</u>:

<b>1. retrogasserian rhizotomy - </b>transection of a portion of the sensory root of V (between trigeminal ganglion and the pons).

<b>2. medullary tractomy -</b> trasection of the spinal tract of V in the medulla <b><span style="color: #ff0000;">below</span></b> the obex using tuberculum cinereum as a guide.

The nucleus for cranial nerve 4 (trochlear n.) is found at which level of brain stem?

Caudal portion of the midbrain

Subdivision of the midbrain in cross section

<b>1. tectum -</b> 'roof', superior and inferior colliculi
<b>2. Cerebral aqueduct -</b> with surrounding preaqueductal gray (central gray)
<b>3. Cerebral peduncle </b>- divided into:
<b> a. tegmentum-</b> sensory tracts, extrapyramidal tracts, cranial nuclei, <span style="color: #ff0000;">★</span>red nucleus, decussation of the superior cerebellar peduncle
<b> b. substantia nigra-</b> part of functional cerebellar peduncle
<b> c. crus cerebri -</b> descending motor fibers

Tectum

is a region of the brain, specifically the <span style="color: #ff0000;">dorsal</span> part of the mesencephalon (midbrain). This is contrasted with the tegmentum, which refers to the region ventral to the ventricular system.
<span style="color: #ff0000;">★</span>It is responsible for auditory and visual reflexes.

red nucleus

► Part of tegmentum of midbrain
► It is the main route for the <b>mediation</b> of voluntary movement. It is responsible for large muscle movement such as the arms and the legs as well as for fine motor control.

► Its associated with <span style="color: #ff0000;">rubrospinal tract</span>

Superior oblique muscle

depresses and ABducts the eye (down and out)

In <b>unilateral</b> involvement of trochlear nerve, the head tilts to the side ____________ to compensate.

a. of the lesion
b. opposite of the lesion

b. opposite of lesion

The left superior oblique m. will be paralyzed if the lesion occurs in the left side of:

a. tectum
b. tegmentum

tectum

Red nucleus can be found in which portion of mid-brain?

at the level of <b>superior</b> colliculus

The _____________, by most classifications, is everything in the mesencephalon/midbrain except the tectum.

cerebral peduncle

Crus cerebri

Ventral aspect of the midbrain containing principally corticospinal, corticobulbar, and corticopontine tracts.

Extend of medial lemniscus

(T/F) Lateral lemnsicus terminates at thalamus.

False

Lateral lemniscus fibers synaps in <b>inferior colliculus</b> with cell bodies of neurons that travel up to thalamus. Associated with hearing.

Obstruction of which artery can lead to damage to pons and midbrain?

basilar artery

location of Oculomotor Nuclear Complex

Oculomotor Nuclear Complex = Occlumotor nucleus (motor) + Edinger-Westphal nucleus (parasymphathetic)

anterior to <b>peracqueductal grey</b> and posterior to red nuclues at the level of superior colliculus in the midbrain.

Weber's syndrome

► Is a form of stroke characterized by the presence of an oculomotor nerve palsy and <b>contralateral</b> <i>hemiplegia</i>.

A patient has the following symptoms:

✓ Ptosis of left eye
✓ Mydriasis of the left eye
✓ inability to read things in close distance
✓ inability to move his right arm and leg

What is the diagnosis?

Weber's disease

ipsilateral third nerve palsy + contralateral UMN paralysis.

The location of the damage is in the <b>crus cerebri</b> at the level of <b>superior</b> colliculus.

Cause » damage to <b><span style="color: #ff0000;">★Posterior cerebral artery</span></b>

Damage of which artery can lead to <b>Weber's syndrom</b>?

Posterior Cerebral Artery (PCA)

Compression of the <b>dorsal</b> midbrain, usually due to a pinealoma, resulting in the inability to <u>raise</u> the eyes above the horizontal plane.

Parinaud's syndrome

cuase ► due to <b>dorsal</b> compression of midbrain.

__________ is inability to raise the eyes above the horizontal plane while _____________ is the inability to adduct the eye during lateral gaze.

» Parinaud's syndrome (Vertical Gaze Center)
» Inter.nuclear ophthalmoplegia (Medial longitudinal fasciculus)

Medial longitudinal fasciculus

Internuclear ophthalmoplegia

based on a lesion of the MLF -> prevents adduction of the eye on the side of the lesion during attempted lateral gaze (convergence is not affected)

Lateral gaze center is located in which nucleus?

abducens nucleus

(T/F) in patients with <b>internuclear ophthalmoplegia</b> the convergence remains normal.

True

Damage to the right MLF causes ______ internuclear ophthalplegia.

Right

the picture shows the LEFT internuclear ophthalplegia

____________ m. contracts causing the pupil constrict.

Sphincter pupillae

Optic radiation

fibres running from the lateral geniculate nucleus to the visual cortex.

The reflex pathway mediating pupillary constriction

Light signals are relayed through the midbrain <span style="color: #ff0000;">pretectum</span>, to preganglionic parasympathetic neurons in the<i> Edinger-Westphal</i> nucleus, and out through the parasympathetic outflow of the oculomotor nerve to the ciliary ganglion. Postganglionic neurons then innervate the smooth muscle of the <b>pupillary sphincter</b>.

Argyll-Robertson pupil

Disorder in which the pupil reacts to accommodation but not to light.

Cause ► Bilateral damage to pretectal nuclei

In this case, the light reflex pathway is damaged but the the accomodiation pathway is intact. note: accomodoation pathway does not include the <b>pretectal nuceli</b>.

Shining the light in one eye will lead to a __________ light reflex.

a. ipsilateral
b. bilateral

b. bilateral

both pupils will constrict in this case

Light reflex:

retina → optic n. → optic chiasm → optic tract- <b><u>pretectal nuclei</b></u> → BOTH Edinger-Westphal nuclei → preganglionic parasympathetic nerve fibers in oculomotor nerves → ciliary ganglia → postganglionic parasympathetic nerve fibers → sphincter pupillae m. → constriction of both pupils.

Vestibular (subcortical) centers for eye movement

responsible for coordination of eye movements associated with inner ear.

direct response vs. consensual response

Direct response- response of the light stimulated eye

Consensual response- response of the unstimulated eye.

Can unilateral damage to the pretectal nuclei cause <b>Argyll-Robertson pupil</b>?

No because each pretectal nuclei projects to both Edinger-Westphals. So we need a <b>bilateral</b> damage.

location of pretectal nuclei

immediatel <b>rostral</b> to the superior colliculus and contains the posterior commissure with the adjacent pretectal nuclei.

Posterior commissure

Fibers important in eye movement and control of pupillary size.

Saccule

A bed of sensory cells situated in the inner ear. It translates head movements into neural impulses which the brain can interpret.
It's sensitive to<b> linear </b>translations of the head, specifically movements<b> up and down</b> (think about moving on an elevator). When the head moves vertically, the sensory cells of the saccule are disturbed and the neurons connected to them begin transmitting impulses to the brain. These impulses travel along the vestibular portion of the eighth cranial nerve to the <b><u>vestibular</b></u> nuclei in the brainstem.

Utricle

Found in the inner ear. It plays a role in equilibrium.

(T/F) Unilateral damage to the CNS portion of auditory system leads to a relatively <B>minor</b> hearing loss.

True

Patients often have difficulty <u>locating direction</u> of the source of sounds and in understanding speech in areas of high background noise.

Primary auditory gyrus

Transverse temporal gyrus (areas 41, 42) in the temporal lobe.

Damage to which of the following is considered <B>nerve portion</b> type of auditory damage?

a. tympanic membrane
b. inner ear fluid
c. organ of Corti
d. Choclear nuclei in rostral medulla
e. lateral lemniscus
f. inferior colliculus

a. tympanic membrane
b. inner ear fluid
c. organ of Corti ✓
d. Choclear nuclei in rostral medulla
e. lateral lemniscus
f. inferior colliculus

Correct order of pathway in central portion of auditory system

Lateral lemniscus (crossed and uncrossed) → Inferior colliculus → inferior brachium → medulla geniculate nucleus of the thalamus → Auditory radiation → transverse temporal gyrus in temporal lobe

(T/F) the auditory information from ONE ear ascends in tracts on BOTH sides of the brain.

True

at the point o lateral lemniscus

Rinne's test

It compares perception of sounds, as transmitted by air or by bone conduction through the mastoid. Thus, one can quickly suspect conductive hearing loss.

» should be accompanied with Weber's test

(T/F) In individuals suffering from conductive deafness, in the weber's test, the sound is louder in affected ear since distraction from external sounds is reduced in that ear

True

Inflammation of middle ear (otitis media) can lead to what kind of deafness?

conductive

Otosclerosis

Hereditary disorder in which ossification of the labyrinth of the inner ear causes tinnitus and eventual deafness.
AKA <b>fixation of stapes</b>.

★ A form of conductive deafness.

Acoustic neurinoma / Vestibular schwannoma leads to what kind of deafness?

a. conductive
b. nerve
c. central

a. conductive
b. nerve ✓
c. central

Is a benign primary intracranial tumor of the myelin-forming cells of the vestibulocochlear nerve (CN VIII).

Drugs, prolonged exposure to loud noise, rubella in utero, and again are all factors that can lead to ___________ deafness.

nerve deafness

Damage to the peripheral portion of auditory system can lead to:

a. ipsilateral conductive deafness
b. contralateral conductive deafness
c. ipsilateral nerve deafness
d. contralateral nerve deafness

a. ipsilateral conductive deafness ✓
b. contralateral conductive deafness
c. ipsilateral nerve deafness ✓
d. contralateral nerve deafness

Static labyrinth

STATIC labyrinth = macula utricle, macula sacculi
• <b>LINEAR</b> acceleration/deceleration
• Proper alignment of head, eyes, body relative to gravity (posture)

saccule - The smaller of the two membranous sacs in the vestibule of the inner ear; it contains a specialized mechanoreceptor, a maculae, for the detection of static equilibrium.

utricle - The larger of the two membranous sacs in the vestibule of the inner ear; it contains a specialized mechanoreceptor, a maculae, for the detection of static equilibrium.

Kinetic Labyrinth

• Consists of three semicircular canals and their <b>crisae ampullaris</b>.
• Evaluates <b> ANGULAR </b>movements of head.

What type of neuronal cell bodies are there in the <b>vestibular ganglion</b>?

<span style="color: #ff0000;">bipolar*</span> with processes in <b>cristae ampullaris and in <u>vestibular nucleus</u> of medulla as well as <u>cerebellum</u>.

*A bipolar cell is a type of neuron which has two extensions. Bipolar cells are specialized sensory neurons for the transmission of special senses. As such, they are part of the sensory pathways for smell, sight, taste, hearing and vestibular functions.

A damage to the vestibular ganglion will most likely cause:

a. loss of hearing
b. loss of balance

b. loss of balance

similar symptoms could be obtain due to damage of vestibular nuclei

Damage to which structure will may cause improper alignment of head, eyes and body relative to gravity (posture)?

a. Macula
b. Cristae ampullaris
c. Vestibular ganglion

a. Macula ✓
b. Cristae ampullaris ✗ → they function in restoration of balance and movement of eyes to maintain ★<u>orientation</u>★ when falling.
c. Vestibular ganglion ✓

Vestibular nuclei projects to: (4)

1. Cerebral cortex - <span style="color: #ff0000;">conscious</span> awareness of position and movement of head

2. Cerebellum

3. Spinal cord via

a. <span style="color: #ff0000;">Lateral</span> vestibulospinal tract <b>IPSILATERAL</b>
b. <span style="color: #ff0000;">Medial</span> vestibulospinal tract <b>BILATERAL</b>

4. Gaze center of the brainstem - via ascending portion of the MLF.

Fibers of MLF

» abducens nucleus → Occlumotor nucleus (Midbrain)
» vestibular nucleus → Vertical gaze center (Midbrain) + abducens gaze center nucleus.
» (Descending portion) vestibular nucleus → <b>medial vestibulospinal tract</b>.

What happens if the <b>lateral vestibulospinal tract</b> is damaged?

Lateral Vestibulospinal tract is associated with <b>static labyrinth</b> thus upon damage, the patient would fall <span style="color: #ff0000;">to the SAME side</span>.

What is the <u>only</u> bilateral projection of fibers from the vestibular nucleus?

Medial vestibulospinal tract

projection to abducens nucleus is contralateral.

When you are about to fall, you will automatically lift your arm to protect yourself from falling on your face. Which spinal cord tract is responsibe for this?

Medial vestibulospinal tract

vestibular nucleus → MVT → LMN in the head and arms.

Activation of cells in the left vestibular nucleus leads to eyes turning to which direction?

opposite direction (right)

Most common form of spina bifida

Spina bifida <b>occulta</b>- defects in the vertebral arches, minor, most common of all bifidas (15-25% population)

Most common form of spina bifida <b>cystica</b>

Meningomyelocele- both meninges and spinal cord protrude.

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