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
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
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
4
Q
Where does an interneuron terminate?
A
Directly or indirectly on a ventral horn cell
5
Q
Two Types of Efferent Neurons
A
Alpha (extrafusal) and Gamma (intrafusal) Motor Neurons
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
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
8
Q
Examples of Myotatic Reflexes
A
Knee-jerk and jaw-jerk reflexes (monosynaptic)
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
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
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
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
13
Q
Features of the Conscious Sensory Pathway
A
Primary neuron, secondary neuron, tertiary neuron, primary somesthetic cortex
14
Q
Define “Lemniscal Systems”
A
Secondary axons that cross the midline
15
Q
Where does the conscious sensory pathway end up? Unconscious?
A
- Cortex
2. Cerebellum
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
17
Q
Alpha and Gamma Motor Neurons can be these kind of fibers:
A
SVE (going to branchiomeric muscles)
GSE (myotomic muscles)
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
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
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
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
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)
23
Q
Unilateral Lesion of the ACST
A
Minimal clinical effect…
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
25
Spinal Cord Injury (SCI)
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
26
Definition of Spasticity
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)
27
Definition of Rigidity
Abnormal, passive resistance to movement in ALL directions (see this in Parkinson's)
28
Decerebrate Rigidity
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
29
Decorticate Rigidity
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
30
Types of Pain and Their Tracts
Sharp, highly-localized (fast) pain = direct spinothalamic pathway (neospinothalamic, AD fibers)
Burning, dull, achy (slow) pain = indirect spinothalamic pathway (paleospinothalamic, C fibers)
31
Lesions of the Spinoreticular Fibers
These fibers receive input from C fibers and travel to the thalamus
Unilateral: no significant effect
Bilateral: may eliminate crude pain sensations
32
Primary Neurons in the Direct Spinothalamic Pathway
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
33
What is the spinal lemniscus made up of?
LSTT joins with the VSTT and the spinotectal tract
SL will terminate in the VPL nucleus of the dorsal thalamus
34
All conscious sensory pathways project to the ____
Primary Somesthetic Cortex (post-central gyrus) in a somatotopic arrangement
CONTRALATERAL
35
Reticular Formation of the Thalamus
Plays a key role in consciousness (see this on EEGs)
"Battery of the cortex"
Keeps us awake/alert/attentive
36
Descending Branches of 1' Neurons in Posterior Column (3)
Fasciculus triangularis = SACRAL
Fasciculus septomarginalis = LUMBAR
Fasciculus interfascicularis = CERVICAL
37
Depolarization of an sensory (afferent) neuron is called a ____
Generator Potential
38
Pacinian Corpuscle Characteristics
- 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
39
What happens at the receptor level once we touch something? (Pacinian example)
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
40
What is an afterdischarge?
This happens when the removal of a stimulus triggers action potentials
41
How do we determine the stimulus intensity?
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)
42
Just Noticeable Difference
The smallest difference that can be detected, usually about 10%
43
Weber-Fechner Law and the New Formula
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
44
Difference in Weber-Fechner Equation w/ Muscle and Cutaneous Senses
Muscle: both constants are close to 1 - perceived matches actual intensity well
Cutaneous: what we perceive may diverge from actuality
45
What is the mechanism behind pre-synaptic inhibition?
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
46
The only sense to pass the thalamus while we sleep is ____
HEARING!
47
Somatic Sensory Area 1 (S1)
Responsible for information about position sense as well as size and shape discrimination - processing is NOT complete here!
Located in the post-central gyrus
48
Somatic Sensory Area 2 (S2)
Receives inputs from S1 and is required for cognitive touch
- stereognosis: mental perception of depth
- determines whether something becomes a memory
49
Damage to Either S1 or S2
If S1 is damaged: WILL impair functioning of S2
If S2 is damaged: WILL NOT impair functioning of S1
50
Parieto-occipital-temporal (PTO) Association Cortex
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
51
Law of Specific Nerve Energies
Stimulation of a sensory pathway leads to the perception of a sensation determined by the type of receptor activated
52
Law of Projections
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
53
Lesion at the Dorsal Roots
Diminished motor reflexes and decreased muscle tonicity
In the sacral region = atonic bladder
54
Unilateral Lesion of Fasciculus Gracilis
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
55
Unilateral Lesion of Fasciculus Cuneatus
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
56
Transection about S2 interupts which tract?
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)
57
Lesion of the LSTT
CONTRALATERAL loss of pain and temperature sensation TWO SEGMENTS BELOW the level of the lesion
58
Destruction of Anterior White Commissure
BILATERAL loss of pain and temperature sensations to the upper extremities
(yoke-like anesthesia)
59
Congenital Absence of C Fibers
Allows non-nociceptive fibers to CLOSE the gate making the person insensitive to pain
Disinhibition of the SG cell
60
Herpes Zoster
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
61
Surgical Anterolateral Cordotomy for Treatment of Intractable Pain
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**
62
Prefrontal Lobotomy
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
63
Syringomyelia
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
64
Neurological Tests (3)
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
65
Tabes Dorsalis Cause
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
66
Tabes Dorsalis Signs and Symptoms
**Lightning pains** are characteristic!
May also have: atonic bladder, slapping of the feet (locomotor ataxia), positive Romberg test, Argyll-Robinson pupil, swollen/distorted joints
67
Poliomyelitis
LMN DISEASE
Initially: severe inflammation, vasodilation, edema, and macrophagic activity
Then see astrocytic gliosis
Patients may eventually recover (nonparalytic polio) or not (paralytic polio)
68
Amyotrophic Lateral Sclerosis (ALS)
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
69
Visceral Pain Fiber vs Visceral Reflex Fiber Location
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
70
Most fibers in the spinal visceral sensory pathway terminate in the ____
Visceral afferent nucleus (VAN) at sacral levels S2-4
71
Pathways that are projected from the VAN:
Visceral-somatic reflex pathway
Visceral-visceral reflex pathway
Spinoreticulothalamic pathway
72
Referred Pain
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
73
Cranial Nerves that Contribute GVAs and Locations
```
VII = soft palate
IX = posterior 1/3 tongue, oropharynx
X = larynx, pharynx, thoracic and abdominal viscera
```
74
Pathways that come off of the solitary nucleus:
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)
75
Solitary-Superior Salivatory Reflex Pathway
Innervates the lacrimal, submandibular, and sublingual glands
Response: increased lacrimation and salivation
76
Solitary-Inferior Salivatory Reflex Pathway
Innervates the parotid gland
Response: increased salivation
77
Solitary-Dorsal Motor Nucleus Pathway
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
78
Solitary-Nucleus Ambiguus Pathway
Projects information to the NA via interneurons in the reticular formation to innervate the larynx and pharynx
Response: deglutition
79
Carotid Body Reflex
```
Stimulus: Increased CO2
Afferent: Sinocarotid (Vagus)
Interneuron: Reticular Formation
Efferent: Phrenic
Effector: Diaphragm
Response: Increased ventilation
```
80
Carotid Sinus Reflex
```
Stimulus: Increased BP
Afferent: Sinocarotid (Vagus)
Interneuron: RF
Efferent: Dorsal Motor Nucleus of Vagus
Response: Decreased cardiac contraction
```
81
Gag Reflex
```
**cortically mediated, may be gone after stroke**
Stimulus: Touching pharyngeal mucosa
Afferent: Glossopharyngeal
Interneuron: RF
Efferent: Pharyngeal branch of Vagus
Response: Gagging
```
82
Laryngeal Expiration Reflex (LER)
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
During an LER cough episode, these sphincters should close in synchronization of the increased intra-abdominal pressure:
Lower esophageal sphincter, internal urethral sphincter, external urethral sphincter, anal sphincter, and inguinal canal
84
Bladder Reflex
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
Atonic Bladder
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
Reflex Bladder
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
Primary Gustatory Cortex is located where?
Opercular area of the post-central gyrus and the adjacent insular area
88
Components of the Ascending Gustatory Pathway
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
Two types of fibers found within nociceptors:
A-delta (fast, sharp pain) and C fibers (slow, dull pain)
90
When are the silent/sleeping nociceptors activated?
There are not normally active, but will activate in instances where there already is an injury and then that area gets damaged again.
91
Ligand-gated receptors that alter the sensitivity of nociceptors:
Substance P, kinins, ATP, H+
92
AD Fibers Neurotransmitter and Receptor
Releases EAAs that act primarily on non-NMDA receptors on secondary neurons in the spinal cord
93
C Fibers Neurotransmitter and Receptor
Releases Substance P and EAAs that will bind to Neurokinin A and NMDA receptors
94
Insular Cortex
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
Amygdala
Receives input from nociceptors and is particularly important for producing emotional components in response to pain
96
Visceral Nociceptors
Travel with autonomic nerves and are thus responsible for the autonomic response to pain (diaphoresis and altered BP)
97
Gate Theory of Pain (peripheral mechanism)
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
Rubbing the Skin Process
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
Pre-Synaptic Inhibition (descending mechanism)
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
Deep Pain Characteristics
Associated with periosteum and ligaments
Few AD fibers, many C fibers = dull pain
101
Muscle Pain Characteristics
Caused by injury or ischemia during contraction
Both AD and C fibers are present = both types of pain
102
Visceral Pain Characteristics
Poorly localized, caused by stretch receptors and often comes with referred pain
Few receptors (almost all C fibers)
103
Chronic Pain Changes
Allodynia (non-noxious stimuli are now painful) and hyperalgesia (pain is out of proportion)
**brain has learned pain too well**
104
Types of Cortical Reflexes
Placing reaction
| Hopping reaction
105
Types of Brainstem/Midbrain Reflexes
Vestibular
Righting reflex
Suckle, yawning
Eye/head
106
Types of Spinal Reflexes
Stretch (myotatic)
Golgi tendon reflex
Crossed extensor
107
Reflex Activity
Precise motions
Mediated at all levels of CNS
Rapid initiation
Elicited even during unconsciousness
108
Volitional Activity
Originates in cortical areas associated with judgement, initiative, and motor control
Longer onset due to processing
Require conscious awareness
109
Extrafusal Fibers
Outside of the muscle, the characteristic fibers that do the work
Innervated by alpha motor neurons
110
Intrafusal Fibers
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
Sensory Component of the Intrafusal Fiber
There are NOT contractile, they are sensitive to length
Contains nuclear bag fiber (larger) and nuclear chain fiber (thinner)
112
Motor Component of the Intrafusal Fiber
Same as skeletal muscle and control the length of the sensory portion
Innervated by gamma motor neurons
113
Primary Afferent (1a fibers) in the Muscle Spindle
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
Secondary Afferent in the Muscle Spindle
Smaller, myelinated Group II fiber
Innervates ONLY the nuclear chain fiber
Sensitive only to the length of the muscle
115
Alpha Motor Neuron
Large, heavily myelinated, innervates skeletal muscle
Responsible for activating muscle
Activity directly leads to motion
116
Gamma Motor Neuron
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
Golgi Tendon Organs
Innervated tendon with a bare nerve ending
Sends an afferent 1b fiber to the spinal cord
Releases EAAs to make interneurons release glycine
118
Importance of 5HTC receptors in spinal shock recovery:
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
With the loss of the cortex, the brainstem inhibitory region is not activated leaving only the brainstem facilatatory region to dominate. This causes what?
SPASTICITY
Can give a patient GABA to help with this
120
Where is the conus medullaris located and what is it responsible for?
Location: LV1-2 interspace
Responsible for bladder and bowel control
121
Where is the cauda equina made up of and what is it responsible for?
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
Important Sensory Dermatomes
```
Thumb - C6
Little Finger - T1
Nipple - T4
Umbilicus - T10
Little Toe - S1
```
123
Important Motor Dermatomes
Deep reflexes: Biceps (C5), Brachioradialis (C6), Triceps (C7), Quads (L3), Gastroc (L5-S2)
124
Blood Supply to the Spinal Cord
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
How can the anterior artery of Adamkiewicz be compromised?
Secondary to thoracolumbar fracture, or from surgical repair of abdominal aortic aneurysms (AAA)
126
The areas most frequently involved in ischemic necrosis of the spinal cord:
Areas adjacent to the enlargement at the upper cervical, thoracic, and lumbar regions
These are also vulnerable to a watershed infarction
127
Four Fundamental Reflex Pathways
Myotatic, Autogenic Inhibition, Reciprocal Inhibition, and Gamma Efferent
128
Characteristics of the Gamma Efferent Reflex
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
Sensory Nuclei of the Spinal Cord
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
Motor Nuclei of the Spinal Cord
```
MMCC: axial musculature
LMCC: extremity musculature
Phrenic: diaphragm
Spinal Accessory: continuous with nucleus ambiguus
SAN: bowel and bladder
```
131
Rexed's Laminae
Layers of the grey matter in correlation to:
II = Substantia Gelatinosa
III-VI = Nucleus Propius
VII = Nucleus Dorsalis, Intermediate Gray
IX = LMCC, MMCC
132
Medial and Lateral Divisions of the Dorsal Roots
Medial: highly myelinated propioceptive/vibrational fibers that enter the posterior columns
Lateral: enters the dorsolateral fasciculus of Lissaur and convey pain/temp
133
Short Ascending Fibers of the Posterior Column
Components of the VSTT system for crude tactile/passive touch, send pressure info to thalamuc
134
Long Ascending Fibers of the Posterior Column
Components of the PC/ML pathway for propioception/2pt tactile touch
135
7 Parts of the Spinal Cord - MUST KNOW
1. Dorsal Root
2. Posterior Column
3. LCST - UMN
4. LSTT
5. Anterior Horn - LMN
6. AWC
7. LRST
136
Fasciculus Propius
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
Lesions of the Fasciculus Propius
Diffuse, bilateral nature of the FP means that a unilateral lesion won't manifest clinical deficits
138
Unilateral Lesion of Spinal Lemniscus
Contralateral hemianalgesia (loss of pain) and thermal hemianesthesia (loss of temp)
139
Ascending Tracts (7)
LSTT, VSTT, Dorsal Spinocerebellar Tract (DSCT), Ventral Spinocerebellar (VSCT), ARAS, Spinotectal, Spino-olivary
140
Dorsal Spinocerebellar Tract (DSCT)
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
Ventral Spinocerebellar Tract (VSCT)
Conveys unconscious general propioceptive information from lumbosacral levels to the cerebellum
142
Ventral Spinothalamic Tract
Conveys light touch, pressure, and crude tactile information
143
Lateral Descending Group (2)
Lateral Corticospinal Tract (LCST) and Rubrospinal Tract (RST)
144
Rubrospinal Tract (RST)
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
Anteriomedial Descending Tracts (6)
ACST, LVST, MVST, MRST, LRST, and Tectospinal Tract
146
Unilateral Lesion of a Lateral Descending Group Tract
Results in significant upper motor paralysis of the distal extremities
147
Unilateral Lesion of the Anteromedial Descending Tract
Results in minimal effect on axial musculature
148
Transection of the spinal cord between the levels of C5-6 results in _____
Bilateral paralysis of the upper and lower extremities (quadriplegia)
149
Transection of the spinal cord between the levels of T1-L2 results in _____
Bilateral paralysis of the lower extremities (paraplegia)
150
Lesion at C1-4
May disrupt the phrenic nucleus and result in respiratory depression or arrest
151
Lesion Above T1
Horner's Syndrome
152
Lesion Above T2
Sweating and vasomotor disturbances of the body
153
Lesion Above C5-T6
"Rocking horse" type of respiration = high thoracic and low cervical damage disrupting the MMCC
Intercostal muscles can't assist in breathing
154
Lesion Above S2
Reflex bladder
155
Lesion Above S3-5
Incontinence - flaccid anal sphincter tone with bowel incontinence
156
Brown-Sequard Syndrome
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
Subacute Combined Degeneration and Pernicious Anemia
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
Ascending fibers of V convey ____
Precise discriminative tactile information from the face
159
Descending fibers of V convey _____
Pain (AD and C fibers) and temperature information from the face
160
Fibers that go to the mesencephalic tract of V convey _____
Proprioceptive information of the face (unconscious and pressure info too)
161
Where do the trigeminal sensory roots bifurcate?
In the middle cerebellar peduncle.
162
All pain and temperature sensations as well as tactile information will terminate in one these these three sub nuclei:
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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)
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163
The only nucleus in the CNS that is comprised of pseudounipolar neurons?
Mesencephalic Nucleus of V
164
Trigeminal motor nucleus Innervates muscles derived from _____
Mesenchymal cells in the first branchial arch
165
Where do secondary axons of the trigeminal pathway decussate and ascend?
Trigeminal Lemniscus
166
Pathway that conveys C type slow pain fiber the subnucleus caudalis?
Trigemino-reticulo-thalamic Pathway
167
Which nuclei in the trigeminal pathway project to the cerebellum?
Subnuclei Rostralis and Interpolaris
168
Characteristics of the Trigeminocerebellar Tracts (2)
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
Unilateral lesion of the trigeminal nerve results it:
Anesthesia/loss of sensation to trigeminal dermatomes
Loss of jaw-jerk reflex
Atrophy of muscles of mastication
Loss of corneal reflex
170
Brainstem lesion in the upper medulla that destroys the descending tract of V and secondary fibers in the spinal lemniscus results in:
Alternating Analgesia:
- IPSILATERAL hemianalgesia of the face
- CONTRALATERAL hemianalgesia of the body
171
Unilateral destruction of the trigeminal nerve and corticospinal tract in the pons results in:
Alternating Trigeminal Hemiplegia:
- IPSILATERAL trigeminal anesthesia
- CONTRALATERAL spastic hemiplegia
172
Trigeminal Neuralgia
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
Connections of the Cochlear Nuclei (2)
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
Primary Auditory Cortex is located in the:
Transverse and Superior Temporal Gyri
175
Auditory Association Cortex is located where?
Parieto-occipto-temporal (POT) association cortex and is linked directly to the Superior Longitudinal Fasciculus
176
Superior Olivary Nucleus Complex has two parts:
Medial = localizes sound
Lateral = give rise to olivocochlear efferents to influence the Organ of Corti
177
Lesion of the Primary Auditory Cortex
Difficulty in localizing sounds but DOES NOT result in hearing loss
178
Unilateral Lesion of the Cochlear Nerve
IPSILATERAL complete deafness
179
Unilateral Lesion of the Central Auditory Pathway
Bilateral diminution of hearing that is more prominent in the contralateral ear
Includes: lateral lemniscus, inferior colliculus, brachium, medial geniculate body
180
Conduction Aphasia
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
Lesion in the POT Association Cortex
Results in Auditory Agnosia = inability to comprehend auditory information
182
Damage to Wernicke's Area in the Dominant Hemisphere
Results in Fluent Paragrammatical Aphasia = inability to comprehend the spoken or written word and may have circumlocution of language (create their own words)
183
Clinically, lesions of the visual system are ALWAYS described in terms of their ______
Visual field deficits
184
The visual field projects an ______ image onto the retinal field.
Inverted and Reversed
185
Fibers from temporal hemiretina _______ in the optic chiasm where as fibers from the nasal hemiretina _____ in the chiasm
DO NOT CROSS
CROSS
186
The Rule of L's
Lower hemiretina projects to:
- lateral part of the lateral geniculate body
- loop of Meyer
- lingual gyrus
187
Optic radiations travel from _____
The lateral geniculate body to the primary visual cortex
188
Homonymous Visual Fields
Corresponding halves of visual fields
Ex. Temporal field of one eye and the nasal field of the other
189
Heteronymous Visual Fields
Noncorresponding visual fields
Ex. Temporal field of one eye and the temporal field of the other eye
190
Unilateral Lesion of the Optic Nerve
Monocular Blindness
191
Bilateral lesion of the lateral aspect of the optic chiasm leads to:
Binasal Hemianopsia = heteronymous blindness in the nasal fields of each eye
**can also be unilateral if caused by atherosclerosis of the ICA**
192
Unilateral lesion to the lateral aspect of the optic chiasm results in:
One-sided Nasal Hemianopsia
Ex. Lesion of the temporal retina on the left eye = left nasal hemianopsia
193
Midline lesion of the medial portion of the optic chiasm results in:
Bitemporal Hemianopsia = can't see in either of the temporal fields
**often caused by pituitary tumors**
194
Unilateral lesion of the lateral geniculate body, complete optic radiations, or visual reflexes results in:
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
Unilateral lesions of the loop of Meyer usually results in:
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
Unilateral lesion of the visual cortex results in:
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
What types of lesions will leave the visual reflexes intact?
Lesions of the pathway from the LGB and the primary visual cortex
198
Visual Agnosia and Associative Visual Agnosia
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
Voluntary Movements of the Eye
Controlled by the frontal eye fields in the middle frontal gyrus
Influences the LMNs of CN 3, 4, and 6
200
Nonvolitional Eye Movements
Controlled by the occipital eye fields in the visual association cortex
Influences the LMNs of CN 3, 4, and 6
