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Neuroscience > Exam 3 Part 1 - Clinical Scenarios and Other Notes > Flashcards

Exam 3 Part 1 - Clinical Scenarios and Other Notes Flashcards

1
Q

Five basic components of the reflex arc:

A

Receptor, afferent neuron, interneuron (sometimes), efferent neuron, and an effector

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2
Q

Characteristics of the Afferent Neuron

A

Pseudounipolar neuron - cell body is in a spinal ganglion, dendrite courses in a spinal nerve, axon enters the spinal cord in the dorsal root where it will bifurcate into ascending and descending branches

This is usually the primary neuron

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3
Q

Types of Interneuron Reflexes (3)

A

Intrasegmental: occur within the same level
Intersegmental: more than one spinal segment
- important here is the fasciculus propius
Contralateral: done by a commissural neuron that goes to the opposite side of the spinal cord

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4
Q

Where does an interneuron terminate?

A

Directly or indirectly on a ventral horn cell

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5
Q

Two Types of Efferent Neurons

A

Alpha (extrafusal) and Gamma (intrafusal) Motor Neurons

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6
Q

Where is the effector usually found?

A

At the motor end plate of a neuromuscular junction to promote some type of motor movement by way of extrafusal or intrafusal fibers

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7
Q

Encephalization

A

Moving functions up to the brain to say what to do (usually in the cortex)

Motor systems do not rely on this because they also have subcortical input

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8
Q

Examples of Myotatic Reflexes

A

Knee-jerk and jaw-jerk reflexes (monosynaptic)

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9
Q

Characteristics of the Myotatic Reflex

A 
Stimulus: rapid stretching of muscle
Receptor: neuromuscular spindle
Afferent: 1a neuron
NO INTERNEURON
Efferent: alpha motor neuron
Effector: extrafusal muscle
Response: contraction of muscle
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10
Q

Characteristics of the Pain Reflex

A 
(polysynaptic)
Stimulus: noxious stimulus (pain)
Afferent: primary neuron(?)
Interneuron: multiple
Efferent: alpha motor
Effector: extrafusal muscle
Response: withdrawal from stimulus
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11
Q

Characteristics of the Autogenic Inhibition Reflex (Golgi Tendon Reflex)

A 
Stimulus: excessive tension on tendon
Receptor: Golgi tendon organ
Afferent: 1b neuron
Interneuron: inhibitory
Efferent: alpha motor neuron
Effector: extrafusal muscle
Response: relaxation of muscle
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12
Q

Characteristics of the Reciprocal Inhibition Reflex

A

Stimulus: contraction of agonist muscle
Receptor: neuromuscular spindle
Afferent: 1a neuron
Interneuron: promotes agonist alpha motor neuron but inhibits antagonist alpha motor neuron
Efferent: alpha motor neuron
Response: contraction of agonist, relaxation of antagonist

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13
Q

Features of the Conscious Sensory Pathway

A

Primary neuron, secondary neuron, tertiary neuron, primary somesthetic cortex

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14
Q

Define “Lemniscal Systems”

A

Secondary axons that cross the midline

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15
Q

Where does the conscious sensory pathway end up? Unconscious?

A
  1. Cortex

2. Cerebellum

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16
Q

LMN are often referred to as ____

A

“Final common pathway” because without them, we have no way to respond to our physical environment

They are usually the last neuron that innervates the muscle

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17
Q

Alpha and Gamma Motor Neurons can be these kind of fibers:

A

SVE (going to branchiomeric muscles)

GSE (myotomic muscles)

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18
Q

Features of LMN Paralysis

A

Caused by the destruction of the motor neurons or the axons of cranial/spinal motor nuclei

Flaccid paralysis, areflexia, atonia, atrophy, fasciculations

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19
Q

Features of the Pyramidal System (Corticospinal Pathway)

A 
Primary motor cortex (precentral cortex)
Corticospinal tract
Mid-3/5 of the cerebral peduncle 
Pyramidal decussation
 - Lateral and anterior corticospinal tracts here
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20
Q

CST in the Pyramidal Decussation

A

In the lower medulla, there is partial decussation of fibers (85-90%) to form the lateral corticospinal tract (LCST) and the uncrossed fibers become the ACST

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21
Q

Lateral Corticospinal Tract (LCST)

A

Descends in the lateral funiculus and most fibers will terminate in UMN neuronal pools (intermediate gray)

In lower medulla, 85-90% of the fibers decussate at the pyramidal decussation

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22
Q

Unilateral Lesion of the LCST

A

IPSILATERAL paralysis/paresis of the distal limb musculature innervated by the spinal segments below the level of the lesion

(Similar to UMN paralysis symptoms)

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23
Q

Unilateral Lesion of the ACST

A

Minimal clinical effect…

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24
Q

Features of UMN Paralysis

A

Caused by interruption of the motor cortex corticospinal or corticobulbar tracts

Spastic paralysis of antigravity muscles
Hypertonia, hyperreflexia, Babinski sign, clonus, rigidity, disuse atrophy

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25
Q

Spinal Cord Injury (SCI)

A

Three phases following UMN lesions:

  1. Spinal shock = areflexia, atonia, flaccid paralysis
  2. Return of basic spinal reflexes = recovery from shock
  3. After 1-2 years, affected muscles will exhibit spasms of the extensors, flexors, or remain flaccid
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26
Q

Definition of Spasticity

A

Abnormal, passive resistance to movement in ONE direction

Brainstem facilitatory region = activates gamma motor neurons

Brainstem inhibitory region = inhibits gamma motor neurons (NOT active on its own)

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27
Q

Definition of Rigidity

A

Abnormal, passive resistance to movement in ALL directions (see this in Parkinson’s)

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28
Q

Decerebrate Rigidity

A

Spasticity of the extensors of both the upper and lower extremities - patients do NOT usually survive this

Spinal reflexes are still intact

Results from the loss of all structures rostral to pons

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29
Q

Decorticate Rigidity

A

Spastic hemiplegia of the flexors of the upper extremity and extensors of the lower extremity

Due to lesion/strokes of the internal capsule (ipsilateral) due to destruction of LCST and RST

Dependent on head position: when head is moved opposite to the affected side, the affected arm will flex more and the opposite arm will extend

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30
Q

Types of Pain and Their Tracts

A

Sharp, highly-localized (fast) pain = direct spinothalamic pathway (neospinothalamic, AD fibers)

Burning, dull, achy (slow) pain = indirect spinothalamic pathway (paleospinothalamic, C fibers)

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31
Q

Lesions of the Spinoreticular Fibers

A

These fibers receive input from C fibers and travel to the thalamus

Unilateral: no significant effect
Bilateral: may eliminate crude pain sensations

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32
Q

Primary Neurons in the Direct Spinothalamic Pathway

A

AD and C fibers which will terminate in the substantia gelatinosa and nucleus propius, respectively

They both will bifurcate to ascend and descend 2 spinal segments in each direction

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33
Q

What is the spinal lemniscus made up of?

A

LSTT joins with the VSTT and the spinotectal tract

SL will terminate in the VPL nucleus of the dorsal thalamus

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34
Q

All conscious sensory pathways project to the ____

A

Primary Somesthetic Cortex (post-central gyrus) in a somatotopic arrangement

CONTRALATERAL

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35
Q

Reticular Formation of the Thalamus

A

Plays a key role in consciousness (see this on EEGs)
“Battery of the cortex”
Keeps us awake/alert/attentive

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36
Q

Descending Branches of 1’ Neurons in Posterior Column (3)

A

Fasciculus triangularis = SACRAL
Fasciculus septomarginalis = LUMBAR
Fasciculus interfascicularis = CERVICAL

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37
Q

Depolarization of an sensory (afferent) neuron is called a ____

A

Generator Potential

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38
Q

Pacinian Corpuscle Characteristics

A
  • Receptor that responds to TOUCH
  • Histology: looks like an onion with alternating levels of membrane and fluid; axon pierces through the middle
  • Contains mechanosensitive Na+ channels
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39
Q

What happens at the receptor level once we touch something? (Pacinian example)

A

The layers of the corpuscle will deform to match whatever we are touching, activate the Na+ channels, and give off APs

If the stimulus continues, the action potentials will eventually die and the fluid will redistribute –> adaptation

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40
Q

What is an afterdischarge?

A

This happens when the removal of a stimulus triggers action potentials

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41
Q

How do we determine the stimulus intensity?

A

Look at the APs! The more there are, the higher the intensity.

If the intensity continues to increase, we will see patterned discharges (doublets/triplets)

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42
Q

Just Noticeable Difference

A

The smallest difference that can be detected, usually about 10%

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43
Q

Weber-Fechner Law and the New Formula

A

Originally said: perceived intensity = log (measured intensity)

Now: perceived intensity = K(measured intensity)^A where K and A are constants that depend on the type of receptor

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44
Q

Difference in Weber-Fechner Equation w/ Muscle and Cutaneous Senses

A

Muscle: both constants are close to 1 - perceived matches actual intensity well

Cutaneous: what we perceive may diverge from actuality

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45
Q

What is the mechanism behind pre-synaptic inhibition?

A

Axo-axonal synapse that causes reduced neurotransmitter release from the inhibited pre-synaptic terminal to control/modify the input

When activated, the neighboring neuron will release GABA –> releases chloride –> hyperpolarization

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46
Q

The only sense to pass the thalamus while we sleep is ____

A

HEARING!

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47
Q

Somatic Sensory Area 1 (S1)

A

Responsible for information about position sense as well as size and shape discrimination - processing is NOT complete here!

Located in the post-central gyrus

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48
Q

Somatic Sensory Area 2 (S2)

A

Receives inputs from S1 and is required for cognitive touch

  • stereognosis: mental perception of depth
  • determines whether something becomes a memory
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49
Q

Damage to Either S1 or S2

A

If S1 is damaged: WILL impair functioning of S2

If S2 is damaged: WILL NOT impair functioning of S1

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50
Q

Parieto-occipital-temporal (PTO) Association Cortex

A

Required for higher level interpretation of sensory inputs
- Receives inputs from S1 and S2

Functions: analysis of spatial coordination of self/objects and naming of objects

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51
Q

Law of Specific Nerve Energies

A

Stimulation of a sensory pathway leads to the perception of a sensation determined by the type of receptor activated

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52
Q

Law of Projections

A

No matter where it is activated, the perceived sensation is always referred back to the area of the body where the receptor is located

Example: hitting your funny bone activates the receptors there causing pain there

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53
Q

Lesion at the Dorsal Roots

A

Diminished motor reflexes and decreased muscle tonicity

In the sacral region = atonic bladder

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54
Q

Unilateral Lesion of Fasciculus Gracilis

A

IPSILATERAL loss of propioception and 2pt tactile discrimination as well as vibratory sensations from the lower half of the body/lower extremity

Partial lesions = dermatomal deficits at that level

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55
Q

Unilateral Lesion of Fasciculus Cuneatus

A

IPSILATERAL loss of propioception, 2pt tactile, and vibratory senses from the upper half of the body/upper extremity

Partial lesions = dermatomal deficits at that level

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56
Q

Transection about S2 interupts which tract?

A

Lateral Reticulospinal Tract (LRST)

Patient will be unable to voluntarily void his bladder
(after spinal shock, may eventually have automatic reflex voiding or a reflexive bladder)

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57
Q

Lesion of the LSTT

A

CONTRALATERAL loss of pain and temperature sensation TWO SEGMENTS BELOW the level of the lesion

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58
Q

Destruction of Anterior White Commissure

A

BILATERAL loss of pain and temperature sensations to the upper extremities

(yoke-like anesthesia)

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59
Q

Congenital Absence of C Fibers

A

Allows non-nociceptive fibers to CLOSE the gate making the person insensitive to pain

Disinhibition of the SG cell

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60
Q

Herpes Zoster

A

Shingles infection may compromise the non-nociceptive alpha and beta fibers allowing the nociceptive C fibers to OPEN the gate making the person have an increased sensitivity to pain from the affected dermatome

Often a transient compromise

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61
Q

Surgical Anterolateral Cordotomy for Treatment of Intractable Pain

A

Used to treat unilateral somatic pain - cuts the spinoreticular fibers of the indirect spinothalamic pathway

Transect the LSTT in the anterolateral quadrant - cut two segments above and on the opposite side of the pain

Crude sensations usually remain intact or are temporarily diminished

uses the denticulate ligaments as landmarks

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62
Q

Prefrontal Lobotomy

A

Prefrontal lobe is important in emotional response to pain

This procedure cuts the fibers connected to the remaining hemispheres

Result: patient loses anxiety and emotional component; they are INDIFFERENT but very aware of the pain

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63
Q

Syringomyelia

A

Cavitation of the central canal, usually in the cervical regions of the spinal cord - may be secondary to central cord syndrome or chiari malformations

Symptoms:

  • destruction of AWC with bilateral loss of pain/temp to upper extremities
  • destruction of LCST with spastic paralysis and UMN symptoms of lower extremity
  • destruction of AH leading to LMN symptoms to upper
  • destruction of posterior columns leading to ipsilateral anesthesia below lesion
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64
Q

Neurological Tests (3)

A
  1. Testing position sense = flex/extend finger
  2. Testing vibratory sense = activated tuning fork
  3. Testing stereognosis and 2pt discrimination = distinguish between 2 blunt tips of paper clip
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65
Q

Tabes Dorsalis Cause

A

Meningovascular inflammation secondary to a syphilis infection - lumbosacral nerves most often affected - leading to BILATERAL ischemic necrosis of the posterior columns and the dorsal roots at this level

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66
Q

Tabes Dorsalis Signs and Symptoms

A

Lightning pains are characteristic!

May also have: atonic bladder, slapping of the feet (locomotor ataxia), positive Romberg test, Argyll-Robinson pupil, swollen/distorted joints

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67
Q

Poliomyelitis

A

LMN DISEASE

Initially: severe inflammation, vasodilation, edema, and macrophagic activity
Then see astrocytic gliosis

Patients may eventually recover (nonparalytic polio) or not (paralytic polio)

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68
Q

Amyotrophic Lateral Sclerosis (ALS)

A

Cause is mostly unknown but may be due to glutamate metabolism defects, average onset is 66yrs

Death is due to bulbar paralysis (vital functions)

Involves both LMN (hypoglossal nucleus, nucleus ambiguus, facial motor nucleus) and UMN (degeneration of corticospinal tracts)

Usually see symptoms in the hands first, then moves up to the shoulder and chest

NO SENSORY DEFICITS - ONLY MOTOR PROBLEMS

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69
Q

Visceral Pain Fiber vs Visceral Reflex Fiber Location

A

Visceral pain: enter the spinal cord along its entire length via spinal nerves

Visceral reflex: enter the spinal cord at the cranial and sacral levels

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70
Q

Most fibers in the spinal visceral sensory pathway terminate in the ____

A

Visceral afferent nucleus (VAN) at sacral levels S2-4

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71
Q

Pathways that are projected from the VAN:

A

Visceral-somatic reflex pathway
Visceral-visceral reflex pathway
Spinoreticulothalamic pathway

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72
Q

Referred Pain

A

Almost any visceral pain may refer to a somatic region (at the level of the cortex)

Example: gall bladder pain may be referred to the area beneath the shoulder blade

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73
Q

Cranial Nerves that Contribute GVAs and Locations

A 
VII = soft palate
IX = posterior 1/3 tongue, oropharynx
X = larynx, pharynx, thoracic and abdominal viscera
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74
Q

Pathways that come off of the solitary nucleus:

A

Solitary-superior salivatory reflex pathway
Solitary-inferior salivatory reflex pathway
Solitary-dorsal motor nucleus (X) pathway
Solitary-nucleus ambiguus pathway

(and the solitary-reticular fibers and the solitary-hypothalamic pathway)

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75
Q

Solitary-Superior Salivatory Reflex Pathway

A

Innervates the lacrimal, submandibular, and sublingual glands

Response: increased lacrimation and salivation

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76
Q

Solitary-Inferior Salivatory Reflex Pathway

A

Innervates the parotid gland

Response: increased salivation

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77
Q

Solitary-Dorsal Motor Nucleus Pathway

A

Fibers sent to the dorsal motor nucleus of the vagus nerve which innervate the larynx, pharynx, thorax, and abdomen

biggest issue here is GERD/LES - HUGE parasympathetic pathway

Response: increased secretion

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78
Q

Solitary-Nucleus Ambiguus Pathway

A

Projects information to the NA via interneurons in the reticular formation to innervate the larynx and pharynx

Response: deglutition

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79
Q

Carotid Body Reflex

A 
Stimulus: Increased CO2
Afferent: Sinocarotid (Vagus)
Interneuron: Reticular Formation
Efferent: Phrenic
Effector: Diaphragm
Response: Increased ventilation
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80
Q

Carotid Sinus Reflex

A 
Stimulus: Increased BP
Afferent: Sinocarotid (Vagus)
Interneuron: RF
Efferent: Dorsal Motor Nucleus of Vagus
Response: Decreased cardiac contraction
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81
Q

Gag Reflex

A 
**cortically mediated, may be gone after stroke**
Stimulus: Touching pharyngeal mucosa
Afferent: Glossopharyngeal 
Interneuron: RF
Efferent: Pharyngeal branch of Vagus
Response: Gagging
82
Q

Laryngeal Expiration Reflex (LER)

A

Stimulus: to laryngeal mucosa
Afferent: internal branch of the superior laryngeal nerve (vagus)
Interneuron: RF (LRST) and LVST
— splits here and goes to nucleus ambiguus and the medial motor cell column —
1. Response: Expiratory cough epoch, airway clearing
2. Response: Expiratory “coughs” without inhalation

83
Q

During an LER cough episode, these sphincters should close in synchronization of the increased intra-abdominal pressure:

A

Lower esophageal sphincter, internal urethral sphincter, external urethral sphincter, anal sphincter, and inguinal canal

84
Q

Bladder Reflex

A

Stimulus: increased urine volume activate stretch receptors
Afferent: neurons at S2-4 travel to VAN
Interneuron: convey stimulus to SAN
Efferent: stimulate the bladder to contract
Response: voiding the bladder

85
Q

Atonic Bladder

A

Due to lesions of the dorsal roots of S2-4 or the dorsal funiculi (stops the afferent fibers)

Results in a flaccid bladder and increased capacity

86
Q

Reflex Bladder

A

Transection of the spinal cord above S2 interrupts the LRST to the SAN

Results in patient being unable to void his bladder

(this is the end result of spinal shock and why after an SCI they catheterize)

87
Q

Primary Gustatory Cortex is located where?

A

Opercular area of the post-central gyrus and the adjacent insular area

88
Q

Components of the Ascending Gustatory Pathway

A

SVA fibers from VII, IX, and X
Stimulus: food or fluid
Afferent: either VII or IX depending on where in the oral cavity the taste receptors
—these travel to the NTS and splits into inferior and superior salivatory nucleus—
Response: salivation

89
Q

Two types of fibers found within nociceptors:

A

A-delta (fast, sharp pain) and C fibers (slow, dull pain)

90
Q

When are the silent/sleeping nociceptors activated?

A

There are not normally active, but will activate in instances where there already is an injury and then that area gets damaged again.

91
Q

Ligand-gated receptors that alter the sensitivity of nociceptors:

A

Substance P, kinins, ATP, H+

92
Q

AD Fibers Neurotransmitter and Receptor

A

Releases EAAs that act primarily on non-NMDA receptors on secondary neurons in the spinal cord

93
Q

C Fibers Neurotransmitter and Receptor

A

Releases Substance P and EAAs that will bind to Neurokinin A and NMDA receptors

94
Q

Insular Cortex

A

Important for the interpretation of nociceptive inputs

Tells the body if it’s okay or not

Contributes to the autonomic responses to pain (asymbolia)

95
Q

Amygdala

A

Receives input from nociceptors and is particularly important for producing emotional components in response to pain

96
Q

Visceral Nociceptors

A

Travel with autonomic nerves and are thus responsible for the autonomic response to pain (diaphoresis and altered BP)

97
Q

Gate Theory of Pain (peripheral mechanism)

A

Somatic input can alleviate pain (might be by rubbing the area where the pain is)

Due to EAAs and Substance P being released from the interneuron within the spinal cord

98
Q

Rubbing the Skin Process

A
  1. AB fibers activated
  2. AB releases EAA and activates an inhibitory interneuron
  3. Interneuron releases glycine to inhibit activity of the secondary neuron

END RESULT: rubbing will decrease sensation of pain

99
Q

Pre-Synaptic Inhibition (descending mechanism)

A
  1. Neurons in the periaqueductal gray (PAG) activated by things like opiates, EAA, and cannabinoids
  2. Axons travel to midline raphe and release enkephalins
  3. Serotonin is released to activate inhibitory neurons
  4. Interneuron releases opiates on presynaptic terminal of C fiber
  5. Inhibition reduces Substance P from nociceptor
100
Q

Deep Pain Characteristics

A

Associated with periosteum and ligaments

Few AD fibers, many C fibers = dull pain

101
Q

Muscle Pain Characteristics

A

Caused by injury or ischemia during contraction

Both AD and C fibers are present = both types of pain

102
Q

Visceral Pain Characteristics

A

Poorly localized, caused by stretch receptors and often comes with referred pain

Few receptors (almost all C fibers)

103
Q

Chronic Pain Changes

A

Allodynia (non-noxious stimuli are now painful) and hyperalgesia (pain is out of proportion)

brain has learned pain too well

104
Q

Types of Cortical Reflexes

A

Placing reaction

Hopping reaction

105
Q

Types of Brainstem/Midbrain Reflexes

A

Vestibular
Righting reflex
Suckle, yawning
Eye/head

106
Q

Types of Spinal Reflexes

A

Stretch (myotatic)
Golgi tendon reflex
Crossed extensor

107
Q

Reflex Activity

A

Precise motions
Mediated at all levels of CNS
Rapid initiation
Elicited even during unconsciousness

108
Q

Volitional Activity

A

Originates in cortical areas associated with judgement, initiative, and motor control
Longer onset due to processing
Require conscious awareness

109
Q

Extrafusal Fibers

A

Outside of the muscle, the characteristic fibers that do the work

Innervated by alpha motor neurons

110
Q

Intrafusal Fibers

A

Sensory fiber in the center of the spindle that contracts at the ends

Contracting these fibers stretches the sensory portion and makes it more sensitive

111
Q

Sensory Component of the Intrafusal Fiber

A

There are NOT contractile, they are sensitive to length

Contains nuclear bag fiber (larger) and nuclear chain fiber (thinner)

112
Q

Motor Component of the Intrafusal Fiber

A

Same as skeletal muscle and control the length of the sensory portion

Innervated by gamma motor neurons

113
Q

Primary Afferent (1a fibers) in the Muscle Spindle

A

Innervates both the nuclear bag and nuclear chain

Large, myelinated, and sensitive to both length of muscle and how fast the length is changing

APs increase with stretch

114
Q

Secondary Afferent in the Muscle Spindle

A

Smaller, myelinated Group II fiber

Innervates ONLY the nuclear chain fiber

Sensitive only to the length of the muscle

115
Q

Alpha Motor Neuron

A

Large, heavily myelinated, innervates skeletal muscle

Responsible for activating muscle

Activity directly leads to motion

116
Q

Gamma Motor Neuron

A

Slightly smaller, slower than alpha and innervates the contractile portion of the muscle spindle

Controls sensitivity of muscle spindle

Activity does NOT directly lead to motion

117
Q

Golgi Tendon Organs

A

Innervated tendon with a bare nerve ending

Sends an afferent 1b fiber to the spinal cord

Releases EAAs to make interneurons release glycine

118
Q

Importance of 5HTC receptors in spinal shock recovery:

A

They are self-activating and release lots of calcium. If the neurons can restore input to the brain, the calcium can help recovery of reflexes. If not, the excess calcium will cause muscle spasm

119
Q

With the loss of the cortex, the brainstem inhibitory region is not activated leaving only the brainstem facilatatory region to dominate. This causes what?

A

SPASTICITY

Can give a patient GABA to help with this

120
Q

Where is the conus medullaris located and what is it responsible for?

A

Location: LV1-2 interspace

Responsible for bladder and bowel control

121
Q

Where is the cauda equina made up of and what is it responsible for?

A

Made up of dorsal/ventral roots which course through the lumbar cistern

If cut, causes loss of function to the lumbar plexus and LMN paralysis symptoms

122
Q

Important Sensory Dermatomes

A 
Thumb - C6
Little Finger - T1
Nipple - T4
Umbilicus - T10
Little Toe - S1
123
Q

Important Motor Dermatomes

A

Deep reflexes: Biceps (C5), Brachioradialis (C6), Triceps (C7), Quads (L3), Gastroc (L5-S2)

124
Q

Blood Supply to the Spinal Cord

A

Anterior spinal a. - most of the central gray matter
Posterior spinal a. - supply 75% of posterior column

Anterior artery of Adamkiewicz - major supply to the inferior 2/3 of the spinal cord

125
Q

How can the anterior artery of Adamkiewicz be compromised?

A

Secondary to thoracolumbar fracture, or from surgical repair of abdominal aortic aneurysms (AAA)

126
Q

The areas most frequently involved in ischemic necrosis of the spinal cord:

A

Areas adjacent to the enlargement at the upper cervical, thoracic, and lumbar regions

These are also vulnerable to a watershed infarction

127
Q

Four Fundamental Reflex Pathways

A

Myotatic, Autogenic Inhibition, Reciprocal Inhibition, and Gamma Efferent

128
Q

Characteristics of the Gamma Efferent Reflex

A

This pathway controls muscle tone and propioception

Key neuron in this pathway is the gamma motor neuron (if this decreases, see hypotonia and hyporeflexia)

Intrafusal muscle cells control the amount of tension and sensitivity of the spindles (the tighter, the more sensitive, the more information sent out)

Net result: alteration in muscle tone and reflexes and the maintenance of accurate proprioception

129
Q

Sensory Nuclei of the Spinal Cord

A

Substantia Gelatinosa (SG): pain/temp –> LSTT
Nucleus Propius (NP): pain/temp –> Fasciculus Propius
Nucleus Dorsalis: unconscious, thoracolumbar –> DSCT
VAN: visceral reflexes –> IG, RF
Intermediate Gray: sensorimotor –> ventral horn

130
Q

Motor Nuclei of the Spinal Cord

A 
MMCC: axial musculature
LMCC: extremity musculature 
Phrenic: diaphragm
Spinal Accessory: continuous with nucleus ambiguus
SAN: bowel and bladder
131
Q

Rexed’s Laminae

A

Layers of the grey matter in correlation to:
II = Substantia Gelatinosa
III-VI = Nucleus Propius
VII = Nucleus Dorsalis, Intermediate Gray
IX = LMCC, MMCC

132
Q

Medial and Lateral Divisions of the Dorsal Roots

A

Medial: highly myelinated propioceptive/vibrational fibers that enter the posterior columns

Lateral: enters the dorsolateral fasciculus of Lissaur and convey pain/temp

133
Q

Short Ascending Fibers of the Posterior Column

A

Components of the VSTT system for crude tactile/passive touch, send pressure info to thalamuc

134
Q

Long Ascending Fibers of the Posterior Column

A

Components of the PC/ML pathway for propioception/2pt tactile touch

135
Q

7 Parts of the Spinal Cord - MUST KNOW

A
  1. Dorsal Root
  2. Posterior Column
  3. LCST - UMN
  4. LSTT
  5. Anterior Horn - LMN
  6. AWC
  7. LRST
136
Q

Fasciculus Propius

A

Surrounds the periphery of the gray matter

Responsible as a sensorimotor integrator of intersegmental reflexes

Receives the reticulospinal and spinoreticular tract (slow pain pathway)

137
Q

Lesions of the Fasciculus Propius

A

Diffuse, bilateral nature of the FP means that a unilateral lesion won’t manifest clinical deficits

138
Q

Unilateral Lesion of Spinal Lemniscus

A

Contralateral hemianalgesia (loss of pain) and thermal hemianesthesia (loss of temp)

139
Q

Ascending Tracts (7)

A

LSTT, VSTT, Dorsal Spinocerebellar Tract (DSCT), Ventral Spinocerebellar (VSCT), ARAS, Spinotectal, Spino-olivary

140
Q

Dorsal Spinocerebellar Tract (DSCT)

A

Conveys unconscious precise propioceptive information from the inferior half of the body and lower extremities to the cerebellum

Originates in the ND and terminates in the anterior vermis of the cerebellum

141
Q

Ventral Spinocerebellar Tract (VSCT)

A

Conveys unconscious general propioceptive information from lumbosacral levels to the cerebellum

142
Q

Ventral Spinothalamic Tract

A

Conveys light touch, pressure, and crude tactile information

143
Q

Lateral Descending Group (2)

A

Lateral Corticospinal Tract (LCST) and Rubrospinal Tract (RST)

144
Q

Rubrospinal Tract (RST)

A

Originates from the red nucleus in the mesencephalon

In the midbrain, RST completely decussates

In the spinal cord, courses anterior to LCST and terminates in the IG

Major descending pathway of the extrapyramidal system

145
Q

Anteriomedial Descending Tracts (6)

A

ACST, LVST, MVST, MRST, LRST, and Tectospinal Tract

146
Q

Unilateral Lesion of a Lateral Descending Group Tract

A

Results in significant upper motor paralysis of the distal extremities

147
Q

Unilateral Lesion of the Anteromedial Descending Tract

A

Results in minimal effect on axial musculature

148
Q

Transection of the spinal cord between the levels of C5-6 results in _____

A

Bilateral paralysis of the upper and lower extremities (quadriplegia)

149
Q

Transection of the spinal cord between the levels of T1-L2 results in _____

A

Bilateral paralysis of the lower extremities (paraplegia)

150
Q

Lesion at C1-4

A

May disrupt the phrenic nucleus and result in respiratory depression or arrest

151
Q

Lesion Above T1

A

Horner’s Syndrome

152
Q

Lesion Above T2

A

Sweating and vasomotor disturbances of the body

153
Q

Lesion Above C5-T6

A

“Rocking horse” type of respiration = high thoracic and low cervical damage disrupting the MMCC

Intercostal muscles can’t assist in breathing

154
Q

Lesion Above S2

A

Reflex bladder

155
Q

Lesion Above S3-5

A

Incontinence - flaccid anal sphincter tone with bowel incontinence

156
Q

Brown-Sequard Syndrome

A

Unilateral transverse lesion/hemisection of the spinal cord usually due to a knife or tumor pressing on the cord

  1. Ipsilateral loss of prop./vibratory sensations from body below the lesion
  2. Ipsilateral spastic paralysis below the level of lesion
  3. Contralateral loss of pain/temp. from body 2 segments below the lesion

Destruction of the posterior columns, LSTT, LCST

157
Q

Subacute Combined Degeneration and Pernicious Anemia

A

Atrophy of the mucosal lining of the stomach causes absence of intrinsic factor = vitamin B12 deficiency

Results in the degeneration of the posterior columns and the pyramidal tracts

Symptoms: numbness and tingling in fingers/toes, bilateral loss of propioception, UMN paralysis signs

158
Q

Ascending fibers of V convey ____

A

Precise discriminative tactile information from the face

159
Q

Descending fibers of V convey _____

A

Pain (AD and C fibers) and temperature information from the face

160
Q

Fibers that go to the mesencephalic tract of V convey _____

A

Proprioceptive information of the face (unconscious and pressure info too)

161
Q

Where do the trigeminal sensory roots bifurcate?

A

In the middle cerebellar peduncle.

162
Q

All pain and temperature sensations as well as tactile information will terminate in one these these three sub nuclei:

A 
Subnucleus Rostralis (tactile from central region of the face)
Subnucleus Interpolaris (peripheral region of the face)
Subnucleus Caudalis (pain and temp from anterior half of head)
163
Q

The only nucleus in the CNS that is comprised of pseudounipolar neurons?

A

Mesencephalic Nucleus of V

164
Q

Trigeminal motor nucleus Innervates muscles derived from _____

A

Mesenchymal cells in the first branchial arch

165
Q

Where do secondary axons of the trigeminal pathway decussate and ascend?

A

Trigeminal Lemniscus

166
Q

Pathway that conveys C type slow pain fiber the subnucleus caudalis?

A

Trigemino-reticulo-thalamic Pathway

167
Q

Which nuclei in the trigeminal pathway project to the cerebellum?

A

Subnuclei Rostralis and Interpolaris

168
Q

Characteristics of the Trigeminocerebellar Tracts (2)

A

Afferent fibers from CN V will either:

  • ascend to the main sensory nucleus in the superior cerebellar peduncle and convey PRECISE info
  • descend to the subnuclei in the inferior cerebellar peduncle and convey CRUDE info

BOTH of these will go to the cerebellar vermis

169
Q

Unilateral lesion of the trigeminal nerve results it:

A

Anesthesia/loss of sensation to trigeminal dermatomes
Loss of jaw-jerk reflex
Atrophy of muscles of mastication
Loss of corneal reflex

170
Q

Brainstem lesion in the upper medulla that destroys the descending tract of V and secondary fibers in the spinal lemniscus results in:

A

Alternating Analgesia:

  • IPSILATERAL hemianalgesia of the face
  • CONTRALATERAL hemianalgesia of the body
171
Q

Unilateral destruction of the trigeminal nerve and corticospinal tract in the pons results in:

A

Alternating Trigeminal Hemiplegia:

  • IPSILATERAL trigeminal anesthesia
  • CONTRALATERAL spastic hemiplegia
172
Q

Trigeminal Neuralgia

A

Trigger zone on the head (cutaneous region) may initiate epileptic-like discharges from the subnucleus caudalis

Have intractable facial pain

Treatment: anticonvulsant medication or cryosurgery/tractotomy

173
Q

Connections of the Cochlear Nuclei (2)

A

Dorsal/Intermediate Acoustic Striae - these will ascend in the contralateral lateral lemniscus and terminate in the inferior colliculus

Ventral Acoustic Striae - forms the Trapezoid Body and terminate in the superior olivary nucleus (SON) and terminates in the inferior colliculus

174
Q

Primary Auditory Cortex is located in the:

A

Transverse and Superior Temporal Gyri

175
Q

Auditory Association Cortex is located where?

A

Parieto-occipto-temporal (POT) association cortex and is linked directly to the Superior Longitudinal Fasciculus

176
Q

Superior Olivary Nucleus Complex has two parts:

A

Medial = localizes sound

Lateral = give rise to olivocochlear efferents to influence the Organ of Corti

177
Q

Lesion of the Primary Auditory Cortex

A

Difficulty in localizing sounds but DOES NOT result in hearing loss

178
Q

Unilateral Lesion of the Cochlear Nerve

A

IPSILATERAL complete deafness

179
Q

Unilateral Lesion of the Central Auditory Pathway

A

Bilateral diminution of hearing that is more prominent in the contralateral ear

Includes: lateral lemniscus, inferior colliculus, brachium, medial geniculate body

180
Q

Conduction Aphasia

A

Lesion of the arcuate fasciculus

Fluent language disorder characterized by difficulty reading aloud, paraphasia, anomia

May also be present with right hemiparesis and hemianopsia, along with orofacial apraxia

181
Q

Lesion in the POT Association Cortex

A

Results in Auditory Agnosia = inability to comprehend auditory information

182
Q

Damage to Wernicke’s Area in the Dominant Hemisphere

A

Results in Fluent Paragrammatical Aphasia = inability to comprehend the spoken or written word and may have circumlocution of language (create their own words)

183
Q

Clinically, lesions of the visual system are ALWAYS described in terms of their ______

A

Visual field deficits

184
Q

The visual field projects an ______ image onto the retinal field.

A

Inverted and Reversed

185
Q

Fibers from temporal hemiretina _______ in the optic chiasm where as fibers from the nasal hemiretina _____ in the chiasm

A

DO NOT CROSS

CROSS

186
Q

The Rule of L’s

A

Lower hemiretina projects to:

  • lateral part of the lateral geniculate body
  • loop of Meyer
  • lingual gyrus
187
Q

Optic radiations travel from _____

A

The lateral geniculate body to the primary visual cortex

188
Q

Homonymous Visual Fields

A

Corresponding halves of visual fields

Ex. Temporal field of one eye and the nasal field of the other

189
Q

Heteronymous Visual Fields

A

Noncorresponding visual fields

Ex. Temporal field of one eye and the temporal field of the other eye

190
Q

Unilateral Lesion of the Optic Nerve

A

Monocular Blindness

191
Q

Bilateral lesion of the lateral aspect of the optic chiasm leads to:

A

Binasal Hemianopsia = heteronymous blindness in the nasal fields of each eye

can also be unilateral if caused by atherosclerosis of the ICA

192
Q

Unilateral lesion to the lateral aspect of the optic chiasm results in:

A

One-sided Nasal Hemianopsia

Ex. Lesion of the temporal retina on the left eye = left nasal hemianopsia

193
Q

Midline lesion of the medial portion of the optic chiasm results in:

A

Bitemporal Hemianopsia = can’t see in either of the temporal fields

often caused by pituitary tumors

194
Q

Unilateral lesion of the lateral geniculate body, complete optic radiations, or visual reflexes results in:

A

Contralateral Homonymous Hemianopsia = in one eye, can’t see in the temporal field, and in the other, can’t see in the nasal field

Ex. Lesion of the right LGB means that you can’t see out of your left eye temporal region or right eye nasal region

195
Q

Unilateral lesions of the loop of Meyer usually results in:

A

Contralateral Superior Quadrantanopia - can’t see out of one of the superior quadrants, same side on both eyes

may be caused by a tumor or infarction in the posterior temporal lobe

196
Q

Unilateral lesion of the visual cortex results in:

A

Incongruent Contralateral Homonymous Hemianopsia with macular sparing = these are asymmetrical and have the macular area still intact

This may also be due to PCA obstruction

197
Q

What types of lesions will leave the visual reflexes intact?

A

Lesions of the pathway from the LGB and the primary visual cortex

198
Q

Visual Agnosia and Associative Visual Agnosia

A
  1. Rare condition –> unable to visually recognize objects or pictures
  2. Infarction of the occipital lobe due to PCA occlusion –> cannot name an object but understands what it is
199
Q

Voluntary Movements of the Eye

A

Controlled by the frontal eye fields in the middle frontal gyrus

Influences the LMNs of CN 3, 4, and 6

200
Q

Nonvolitional Eye Movements

A

Controlled by the occipital eye fields in the visual association cortex

Influences the LMNs of CN 3, 4, and 6

Neuroscience (4 decks)

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