Anatomy Flashcards
At what level of the brain is the cerebral aqueduct? Pons?
Mesencephalon; Metencephalon
Need to know this for all structures
What is the key component to a reflex arc?
Interneuron:
- excitatory or inhibitory
- Intrasegmental
- Intersegmental
- Commissural (crosses)
What is an example of a monosynaptic reflex? These reflexes do NOT have an interneuron
Myotatic reflex, such as knee-jerk or jaw-jerk reflexes
What is the sequence of a myotatic reflex? (6)
Stimulus (rapid stretching of m.)--> Receptor (neuromuscular spindle)--> Afferent (Ia neuron)--> Efferent (a-motor)--> Effector (extrafusal m.)--> Response (contraction of m.)
Ex: Patellar reflex
What is the gamma efferent pathway involving supraspinal influences?
Ia afferent neuron--> interneuron--> Alpha motor neuron--> Infrafusal fiber of NMS--> Motor end plate
keeps NMS tight!
TQ:
Increased gamma activity leads to….
Decreased gamma activity leads to….
- Increased gamma activity=hypertonia and hyperreflexia
- Decreased gamma activity=hypotonia and hyporeflexia
The primary neuron is a ______________ neuron whose cell body is located in a ________ganglion. Central process enter CNS and bifurcates to ascend and descend a variable number of segments. Along its course it sends off collaterals to __________ for reflexes. The primary sensory fiber eventually terminates on a ___________ neuron.
- pseudounipolar neuron
- spinal ganglion
- interneurons
- secondary neuron
The secondary neuron is located in the ___________ (pain and temperature pathway) or in the ________ (proprioceptive pathway)
- Spinal cord
- Medulla
In a conscious sensory pathway, the secondary axon always decussates and ascends as a __________. It terminates upon a _______ neuron in the dorsal thalamus.
- Lemniscus
- Tertiary
T/F: A lemniscus is comprised of secondary neurons containing information from the same side.
FALSE: A lemniscus contains information from the opposite side!
The tertiary neuron is located in a nucleus of the dorsal thalamus. It projects to the ______ ________ ______ via the ________ ______.
- Primary somesthetic cortex
- Internal capsule
Motor neurons are the last link in a complex motor system that is built on basic reflex circuits. Therefore, lower motor neurons (LMN) are referred to as the “_______ ________ _______”
Final common pathway
T/F: Without LMN we have no way to respond to our physical environment.
True! LMN are the final effectors of the motor system. They are the ones directly connected to the muscle
What are the two types of LMN?
What does each innervate?
- Alpha motor neurons (innervate extrafusal/skeletal m.)
- Gamma motor neurons (innervate intrafusal/modified mm. of proprioceptive NMS)
T/F: Most descending fibers terminate in LMN pools
True! There is a somatotopic organization of the anterior horn
LMN have alpha and gamma motor neurons that innervate mm. of either __________ or _________ origin.
- Branchiomeric (SVE)
- Myotomic (GSE)
LMN innervate SVE mm., such as …..(2 examples)
- Trigeminal motor nucleus (mastication mm.)
- Facial motor nucleus (mm. of facial expression)
LMN innervate GSE mm., such as….(2 examples)
- Oculomotor nucleus (LPS, rectus mm., IO)
- Hypoglossal nucleus (intrinsic mm. of the tongue)
Pt presents with…Dx?
- Flaccid paralysis (limp)
- Areflexia (no reflex)
- Atonia (gamma motor n. tone gone)
- Atrophy (loss of stim.–>atrophy)
- Fasciculations (twitching or denervated m.)
LMN paralysis
Ex: pt with ALS - Hypoglossal n. gone… dysarthria due to paralyzed tongue
TQ: Pt presents with….Dx?
- Acute onset lasts b/t 2-4 days with fever, headache, vomiting, neck stiffness, and pain in the back limbs.
- Severe inflammation
- Vasodilation
- Edema
- Macrophage activity
- Neuronal death
- Astrocyte gliosis
Acute anterior poliomyelitis
-Selectively involves the LMNs of the anterior horns and CN motor nuclei
The pyramidal system of the conscious sensory pathway is the ___________ pathway.
Corticospinal
The __________ tract descends through the corona radiata, internal capsule, cerebral peduncles, pons, and upper medulla. 85%-90% of the fibers decussate at the pyramidal decussation and forms the _______ _____________ _____. Most of the fibers terminate in LMN pools.
- Corticospinal tract (CST)
- Lateral corticospinal tract (LCST)
Unilateral lesions of the LCST result in (ipsilateral/contralateral) paralysis or paresis of the (proximal/distal) limb musculature innervated by those spinal segments below the level of the lesion.
- Ipsilateral
- Distal
For the corticospinal fibers that do NOT cross at the decussation, they continue as the ________________. Unilateral lesions have clinical effect.
Anterior corticospinal tract (ACST)
minimal clinical effect
The inability to play the piano may mean that you have issues with which tract? Why?
The lateral corticospinal tract (LCST)
This tract involves the precise individualized movements of the digits. A unilateral lesion of this group results in significant motor dysfunction of the distal extremities leading to clumsiness and weakness.
The anterior corticospinal tract and reticulospinal tract exert (unilateral/bilateral) influences upon ___ pools.
- Bilateral
- LMN
UMN paralysis is commonly due to interruption of what? (3)
Motor cortex
Corticospinal tracts
Corticobulbar tracts
Pt presents with S/S:
- Spastic paresis of the axial and proximal limb, upper extremity spastic paralysis of distal limb
- Hypertonia and hyperreflexia
- Babinski sign (fanning of toes)
- Clonus
- Rigidity
- Disuse atrophy
(Pt. flexed in upper extremity, extended and supinated in lower extremity with pigeon toed feet)
UMN paralysis
referred to as a spastic paralysis of the antigravity mm.
What are the 3 phases of physical events following UMN lesions?
1) Spinal shock with areflexia, atonia, flaccid paralysis
2) Wks-mo return of basic spinal reflexes (recovered from shock), but still spastic paresis and paralysis
3) 1-2 yrs, muscle spasms of the extensors, flexors, or flaccidity
Abnormal, passive resistance to movement in one direction is called?
Spasticity
Pt presents with…Dx?
- Paralyzed movements in hemiplegic, quadriplegic, or paraplegic distribution (not individual muscle)
- Atrophy of disuse (late/slight)
- Hyperactive DTR
- Clonus
- Clasp-Knife spasticity
- Absent abdominal/cremasteric reflexes
- Babinski sign
UMN lesion!
Pt presents with….Dx?
- Paralyzed individual mm. or sets of mm. in root or peripheral n. distrib.
- Atrophy of denervation (early/severe)
- Fasciculations
- Hypoactive or absent DTR
- Hypotonia
LMN lesion!
Pt presents with…Dx?
- LMN paresis and atrophy of intrinsic mm. of hands, followed later by the arms and shoulder mm.
- Dysarthria, dysphagia, and paresis of the tongue (LMN)
- Spastic paralysis, hyperflexia, and babinski sign due to corticospinal tract involvement (UMN)
- NO sensory deficits!
ALS (amyotrophic lateral sclerosis)
- cause unknown (glutamate metab?)
- Avg. onset=66 yo
LMN: Anterior Horn Cells, Hypoglossal Nucleus, Nucleus Ambiguus, Facial Motor Nucleus
UMN: Chronic, progressive degeneration of the Corticospinal Tracts
Name the region the fx belongs to:
-Ascending tracts for proprioception, 2 pt tactile discrimination, vibratory sensations
Posterior region:
Posterior columns
The distinct ascending tracts provide a “direct line” system to the _______ and _______.
What is this system called?
(Direct/Indirect) spinothalamic pathway
- Thalamus
- Cortex
Direct spinothalamic pathway
The direct spinothalamic pathways is a “labeled line” in that detailed sensory information from a specific part of the body has its own “direct-line wiring” to the thalamus and cortex. This is also called __________ ___________.
Somatotropic organization
Sharp-pricking, highly-localized pain is conveyed via the ______ _____________ pathway. This is part of the ______________ system.
Which type of primary neurons are involved?
- Direct spinothalamic (fast pain)
- Neospinothalamic
- A-delta fibers (myelinated, fast)
Burning, deep, dull, aching, diffuse pain are conveyed via the ________ ____________ pathway. This is part of the _______________ system.
What type of primary fibers are involved?
- Indirect spinothalmic pathway (slow pain)
- Paleospinothalamic tract
- C fibers (unmyelinated, slow)
The primary fibers of the indirect spinothalamic pathway enter the spinal cord, bifurcate, and ascend and descend to a variable # of segment sin the dorsolateral fasciculus of Lissaur. Throughout its course it sends thousands of collateral terminals to the nucleus proprius. From the NP, the fibers may ascend as spinoreticular fibers within the fasciuclus proprius to the thalamus. The fasciculus proprius is part of the _________ _________, which surrounds the gray matter of the spinal cord.
Reticular formation
Unilateral lesions of the spinoreticular fibers do not result in significant sensory deficits because its too bilateral and diffuse to be affected. Bilateral lesions (spinal cord transections) may eliminate crude pain but if it is incomplete or at different levels then cannot eliminate the pain. What is this the basis of?
Neuroanatomical basis of persistent or intractable pain
The ______ ___________ pathway (fast pain) primary axon (A delta or C) enters the spinal cord, bifurcates, and ascends and descends 2 spinal cord segments (2 sensory dermatomes) in the dorsolateral fasciculus (Fasciculus of Lissaur). The secondary neuron is in the Substantia Gelatinosa (A delta) or nucleus proprius (C). The secondary fibers from the SG (A delta) sends axons through the anterior white commissure to ascend in the anterolateral funiculus as the lateral spinothalamic tract (LSTT). In the medulla, the LSTT joins the VSTT to form the spinal lemniscus. The secondary neurons of the spinal lemniscus terminate in the VPL nucleus of the dorsal thalamus, where the tertiary neurons project to the primary somesthetic cortex.
Note: only 1/3 of LSTT fibers reach the thalamus.
-Direct spinothalamic
The VPL nucleus receives sensory information from the contralateral 1/2 of the body via the ______ __________.
Spinal lemniscus
Contralateral loss of pain and temperature sensation two sensory dermatomal segments below the level of the lesion.
Where is the lesion?
(Unilateral/Bilateral) lesion of the ____
Unilateral lesion of the LSTT
Contralateral hemianalgesia and thermal hemianesthesia..
Where is the lesion?
(Unilateral/Bilateral) lesion of the ______ _________
Unilateral lesion of the spinal lemniscus
Grabbing a door handle is dependent on what type of crude tactile discrimination? (comprises roughness, texture, form, localization)
Passive touch = Ventral spinothalamic pathway
“I am in contact with something”
TQ: What type of touch is conveyed by the posterior column/medial lemniscal system (direct line for sensory)? It is associated with learning tactile discrimination, 2 pt tactile discrim, stereognosis (awareness of shape size and texture), proprioception, vibrations, and weight.
Active touch
“I am feeling a penny”
The _______ _____________ pathway conveys light passive touch, crude tactile sensations, and pressure. The central processes of primary neurons course through the medial division of the dorsal root, enters the posterior funiculus, bifurcates, and ascends 6-10 segments, while sending collateral terminals to secondary neurons in the ipsilateral NP and intermediate gray. The secondary neurons from the nucleus proprius cross the anterior white commissure and form an ascending tract (VSTT). In the medulla, the VSTT joins the LSTT to form the spinal lemniscus. The spinal lemniscus terminates on tertiary neurons in the VPL nucleus of the dorsal thalamus. Tertiary neurons project to the primary somesthetic cortex via the posterior limb of the internal capsule.
Ventral spinothalamic pathway (VST)
Clinically, unilateral lesions of the VSTT may be difficult to lose crude touch because fibers ascend in both the posterior (primary fibers) and anterolateral funiculi (secondary fibers). Also deficits of both the VSTT and spinal lemniscus may be masked by the intact _______________________.
Posterior column/medial lemniscal system
Primary neurons of the _____________________ system are the fastest and longest neurons in the sensory system. Some of these neurons extend from the tip of the toe to the medulla. (6 ft long in a basketball player at over 200 mph)
Posterior column/medial lemniscal system
Primary neurons of the PC/ML system enter the posterior column of the spinal cord and segregate into the appropriate fasciculus. If the information is from the lower extremity, the fibers will ascend in the __________ ________. If the information is from the upper extremity, the fibers will ascend in the __________ ________.
- Fasciculus gracilis
- Fasciculus cuneatus
What kind of information does the fasciculus gracilis convey and from where?
(Below dermatome __)
-Proprioception, 2-pt tactile discrimination, and vibratory sensations
-Lower extremities and body
(Below dermatome T6)
What kind of information does the fasciculus cuneatus convey and from where?
(Down to dermatome __)
-Proprioception, 2-pt tactile discrimination, and vibratory sensations
-Upper extremities and body;
(Down to dermatome T7)
T/F: The fasciculus cuneatus is not present in the spinal cord below the level of the 6th thoracic cord segment
True!
In the medulla, the secondary axons from the nucleus gracilis and cuneatus decussate as ________ _______ ______ and form the ______ _________, which terminates on the VPL nucleus.
- Internal arcuate fibers
- Medial lemniscus
Which spinocerebellar (unconscious) pathway deals with precise proprioception of individual muscles in the upper extremity? Lower extremity?
- Upper extremity: Cuneocerebellar tract
- Lower extremity: Dorsal spinocerebellar tract
Which spinocerebellar (unconscious) pathway deals with gross proprioception of the whole limb in the upper extremity? Lower extremity?
- Upper extremity: Rostral spinocerebellar tract
- Lower extremity: Ventral spinocerebellar tract
Pt presents with….Dx?
-loss of proprioception, 2-pt tactile discrimination on the right lower half of body and right lower extremity
right unilateral lesion of the fasciculus gracillis (ipsilateral loss of proprioception, 2 pt tactile discrim to the lower half of body/extremity)
Pt presents with….Dx?
-loss of proprioception, 2-pt tactile discrimination on the left upper half of body and left upper extremity
left unilateral lesion of the fasciculus cuneatus (ipsilateral loss of proprioception, 2 pt tactile discrim. to the upper half of body/extremity)
Pt presents with…Dx?
-loss of proprioception, 2-pt tactile discrimination on the right side of the body and limbs.
left unilateral lesion of the medial lemniscus
opposite side of body has loss of proprio and 2 pt
Pt presents with….Dx?
- hypotonia and/or atonia
- diminished motor reflexes
- atonic bladder and painless urine retention
-Lesion of the dorsal root
could be tabes dorsalis
Pt presents with...dx? spastic paralysis hyperreflexia hypertonia babinski sign clonus disuse atrophy
LCST (lateral corticospinal tract) lesion
Pt presents with:
- urinary retention
- later presents with reflex bladder
- LRST lesion
- Transection of spinal cord above S2
Pt presents with right sided loss of pain and temperature sensation from T8 dermatome to the toe. Dx?
Lesion of the left LSTT at T6 (lateral spinothalamic tract)
contralateral loss of pain and temperature sensation two sensory dermatomal segments below the level of the lesion
Pt presents with bilateral loss of pain and temperature sensations in the upper extremities. Dx?
Anterior white commisure lesion leads to yoke-like anestheisa (shoulder region)
Pt presents with....dx? flaccid paralysis areflexia atonia atrophy fasciculations
LMN paralysis via lesion of the anterior horn cells
Fibers in the medial division of the dorsal root enter the post. column and convey_______________; fibers in the lateral division of the dorsal root enter the dorsolateral fasciculus of lissaur and convey _____________.
proprioception, 2 pt tactile, and vibratory info
pain and temperature info
What dz allows the nonnociceptive fibers to “close” the gate, leading to insensitivity to pain.
congenital absence of C type fibers
disinhib of SG, decrease in C fibers close gate
What infection may compromise the non-nociceptive A α/β fibers, thereby allowing nociceptive C fibers to “open” the gate. The person has increased sensitivity to pain from the sensory dermatome of the affected nerve ex: mandibular.
Herpes zoster infection (shingles)
inhib of SG, A fibers opens gate
While undergoing an anterolateral cordotomy to treat intractable pain of LSTT, the surgeons will cut the cord ________above and on the ________side of the area of pain.
two segments above and on the opposite side
Pt presents with left sided analgesia and left sided thermal anesthesia?
Right unilateral lesion of the spinal lemniscus
T/F: You can have a peripeheral n. lesion of the spinal lemniscus
FALSE: CANNOT get peripheral n. lesion with the spinal lemniscus. Pain and temperature only!
______plays a significant role in the emotional importance and response we have to pain
prefrontal lobes
Pt presents with….dx?
CC: progressive bilateral weakness of her upper extremities of 3-4 years
1) bilateral loss of pain and temperature sensations in the upper extremities***
2) spastic paralysis, hyperreflexia, hypertonia of the lower extremity
3) flaccid paralysis, atrophy, areflexia, atonia of the upper extremity
4) loss of proprioception and 2 pt tactile sensations
Syringomyelia: gross cavitation of the central canal affecting the cervical region of the spinal cord. As the lesion extends laterally into the LSTT, deep pain impaired first!
Destruction of:
1) anterior white commisure (LMN)
2) lateral corticospinal tracts (UMN)
3) anterior horn (LMN)
4) posterior columns
__________axons are all primary axons and therefore result in ipsilateral deficits. Lesions of secondary axons are contralateral deficits.
Posterior column
Pt presents with…Dx?
- Lightning pains from lower limbs for several years
- Atonic bladder (urine retention)
- Broad base gait with slapping of the feet
- (+) Romberg test
- Argyll Robertson pupil: pupils unreactive to light, but constrict during accommodation
Tabes dorsalis! a meningiovascular inflammation of the blood vessels as they pierce through the pia at the junction of the dorsal roots and posterior columns. Occurs in tertiary syphilis.
T/F: The spinal cord level is always the same as the vertebral body level.
FALSE: The more superior you are the more they are equal.
Ex: T9 vertebral body=T10 spinal cord
At what vertebral level does the spinal cord end?
L1-L2 interspace
Conus medullaris level changes with age.
What a. supplies the central area of the spinal cord?
anterior spinal a. (off vertebral)
What a. supplies the posterior portion of the spinal cord?
Posterior spinal a.
Pt presents with big pulsatile mass on the spinal cord leading to neuronal dysfunction, including spastic paraplegia and hyperactive neurons.
Arteriovenous malformation (AVM): no capillary bed between the a. and v.
What may be compromised secondary to repair of AAA leading to paraplegia?
The great anterior a. of Adamkeiwicz
Spinal cord trauma may interrupt the blood supply to the spinal cord, especially in those vulnerable regions served by two arterial supplies, such as….
areas at C2-3, T1-4, L1
The result of ischemic necrosis of the spinal cord is…
partial or complete transection of the spinal cord
The gamma efferent pathways controls…
muscle tone and proprioception
Alpha and gamma motor neurons are ____________, which means they directly innervate a muscle
lower motor neurons
The net result of the gamma efferent pathway is an alteration in ___________and reflexes, and the maintenance of accurate proprioceptive (position-sense) output from the ___________.
muscle tone
neuromuscular spindles
Both hypertonia and hypotonia result in a decrease in the degree and accuracy of movement performed by an affected muscle, and a change in reflex activity. Proprioceptive cues and resultant reflexes are distorted. Which pathway is involved?
The gamma efferent pathway
The gamma efferent pathway keeps the NMS toned during contraction , which is necessary for….
accurate proprioceptive information! Need accurate proprio. to have accurate motor activity.
Name the location and function of the sensory nucleus: substantia gelatinosa (SG)
Posterolateral tip of the dorsal horn at all spinal levels
Pain/temperature pathway
Name the location and function of the sensory nucleus: nucleus proprius (NP)
Mid-portion of the dorsal horn
Pain/temperature pathway
Name the location and function of the sensory nucleus: nucleus dorsalis (clarke's column)
C8-L2
Unconscious proprio.
Name the location and function of the sensory nucleus: visceral afferent (VA) nucleus
T1-L2, S2-4
Visceral sensory integration
Name the location and function of the sensory nucleus: intermediate gray (IG)
All spinal levels
Sensorimotor integration center