Neurology Quiz: Motor Disorders & Limbic System

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Questions and Answers

What is decerebrate rigidity primarily due to?

Damage to the spinal cord

Overactivity of gamma efferent nerve fibers (correct)

Inhibition of sensory nerve pathways

Increased activity of alpha motor neurons

What characterizes paraplegia in flexion?

Persistence of the vestibulospinal tract

All descending tracts are severed (correct)

Diminished reflex responses

Increased tone of extensor muscles

What is the likely cause of paraplegia in extension?

Increased tone of the extensor muscles (correct)

Complete severance of all descending tracts

Decrease in extensor muscle tone

Failure of the vestibulospinal tract

Which function is NOT typically associated with the limbic system?

Motor coordination Signup and view all the answers

What might result from damage to the limbic system?

Anterograde amnesia Signup and view all the answers

What is the primary function of the cervical spine?

To confer structural support and flexibility Signup and view all the answers

Which of the following features characterizes normal spinal alignment?

Cervical lordosis Signup and view all the answers

What is the role of the fovea dentis in the spine?

To articulate with the odontoid process of the axis Signup and view all the answers

What stabilizes the atlanto-occipital junction?

The anterior and posterior atlanto-occipital membranes Signup and view all the answers

How many paired nerve roots does the spine convey?

30 Signup and view all the answers

What functions are primarily associated with the limbic system?

Emotional activities and memory preservation Signup and view all the answers

Which part of the hippocampal formation is considered the transitional zone?

Subiculum Signup and view all the answers

What is the relationship between the hippocampus and short-term memory?

Hippocampus is crucial for the formation of new memories Signup and view all the answers

Which condition is characterized by loss of recent memory and a tendency to fabricate stories?

Korsakoff Syndrome Signup and view all the answers

Which component of the limbic system is primarily involved in emotional behavior?

Amygdala Signup and view all the answers

What is a major function of the hypothalamus as part of the limbic system?

Regulation of emotional responses Signup and view all the answers

What major change is observed after bilateral removal of the hippocampus?

Loss of recent and short-term memory Signup and view all the answers

What best describes Kluver-Bucy Syndrome?

Absence of emotional response Signup and view all the answers

Which area is NOT considered a part of the limbic lobe?

Occipital lobe Signup and view all the answers

What is the primary output pathway from the amygdala associated with pleasure?

Ventral Amygdaloid path Signup and view all the answers

What best explains the initial center of the Papez circuit?

Alveus of the hippocampus Signup and view all the answers

Which structure is involved in transmitting signals from the hippocampus?

Fornix Signup and view all the answers

What neurotransmitter's reduction is linked to cognitive deficits in dementia?

Acetylcholine Signup and view all the answers

Which element of emotional processing bypasses the thalamus?

Smell Signup and view all the answers

What function does the anterior longitudinal ligament (ALL) primarily serve?

It prevents anterior dislocation. Signup and view all the answers

What describes the orientation of the lumbar vertebrae's spinous processes?

Horizontal Signup and view all the answers

How does the posterior longitudinal ligament (PLL) function when it ossifies?

It thickens and potentially compresses spinal structures. Signup and view all the answers

At which vertebral level does the spinal cord typically end in adults?

T12-L1 Signup and view all the answers

What is the role of the ligamentum flavum?

It prevents hyperflexion. Signup and view all the answers

What articulations does the sacrum make with the spine?

Articulates with L5 and the ilium Signup and view all the answers

What is the effect of intervertebral fanning in the thoracic region?

Increases the likelihood of disk herniation Signup and view all the answers

What is a characteristic load-sharing function of the sacrum?

It distributes weight between the spine and pelvis. Signup and view all the answers

What is the composition of the sacrum?

Five vertebrae fused together Signup and view all the answers

Which of the following describes the attachment behavior of the anterior longitudinal ligament?

It adheres to the periosteum of vertebral bodies. Signup and view all the answers

What occurs when the PLL ossifies?

It causes a narrowing of the spinal canal. Signup and view all the answers

What unique characteristic do the thoracic vertebrae exhibit compared to lumbar vertebrae?

Downward-facing spinous processes Signup and view all the answers

What is a distinctive feature of the coccyx?

It is a non-load-bearing structure. Signup and view all the answers

Which of the following is true regarding the ligamentous anatomy of the spine?

The ligamentum flavum connects adjacent laminae. Signup and view all the answers

Where is the thinnest part of the spinal cord's ligament located?

Superiorly and laterally at each level Signup and view all the answers

What structure holds the nerve poles in place?

Filum terminale Signup and view all the answers

Which statement accurately describes the relationship of afferent and efferent pathways in the spinal cord?

Afferent pathways enter at higher levels and remain lateral than lower levels Signup and view all the answers

In which layers are first-order neuron cell bodies of the corticospinal tract predominantly located?

Layer V of the primary motor cortex Signup and view all the answers

What surrounds the small central canal filled with CSF in the transverse section of the spinal cord?

Gray matter Signup and view all the answers

Where does the conus medullaris terminate in adults?

L1-L2 Signup and view all the answers

Which of the following statements about spinal cord width is true?

It is widest in the cervical region Signup and view all the answers

Which part of the spinal cord is involved in the ascending sensory pathways?

Dorsal column-lemniscus Signup and view all the answers

What is the primary role of the paired denticulate ligaments?

Holding the spinal cord to the arachnoid and dural sheath Signup and view all the answers

Which ascending spinal tract is responsible for fine touch and proprioception?

Dorsal column-medial lemniscus Signup and view all the answers

Which of the following describes the flow of CSF from the fourth ventricle?

Into the central canal via obex Signup and view all the answers

Where do the axons of upper motor neurons travel after leaving the cortex?

Through the internal capsule Signup and view all the answers

What is the functional significance of the lumbosacral enlargement?

Motor functions of the lower extremities Signup and view all the answers

What is a distinguishing feature of the spinal cord's white matter?

Surrounds the gray matter Signup and view all the answers

Study Notes

Decerebrate Rigidity

Also known as decerebrate posturing
Caused by overactive gamma efferent nerve fibers to muscle spindles
Results from the release of these neurons from higher centers

Paraplegia in Flexion

Occurs when all descending tracts are severed
Reflex responses are flexor in nature
Tone of extensor muscles is diminished

Paraplegia in Extension

Domination of increased tone of extensor muscles over flexor muscles
Occurs due to incomplete severance of all descending tracts, with persistence of the vestibulospinal tract

Limbic System

A functional system of cortical and subcortical neurons
Interconnections form complex circuits involved in memory, behavior, and emotions
Damage to the limbic system can lead to anterograde amnesia, and inappropriate behavior and emotions

Limbic Lobe: The Limbus

Means "to border, fringe or ring"
Coined by Broca in 1878
Found in the medial surface of the cerebral hemisphere
Borders the corpus callosum and rostral brainstem
Includes:
- Cingulate gyrus and Subcallosal gyrus (anterior extension)
- Cingulum
- Septal regions
- Parahippocampal gyrus and Hippocampal formation

Limbic System Functions

Emotion activities
Preservation of species
Visceral activities
Mechanisms for memory

Hippocampal Formation

Involved in memory and learning
Three parts:
- Dentate gyrus
- Hippocampus proper (Ammon’s Horn)
- Subiculum (transitional zone between hippocampus and entorhinal area)
Resembles a seahorse
2 inches long
Located on the floor of the temporal horn of the lateral ventricle

Hippocampal Connections

Connect to:
- Cingulum to prefrontal, posterior parietal, and temporal association areas, and the entorhinal area of the parahippocampal gyrus
- Hippocampal formation via the cingulum from cerebral cortex

Hippocampal Function

Formation of new memories and learning
Bilateral removal can lead to loss of recent and short-term memory and the ability to learn
Anterograde amnesia
Signals are emitted to the hippocampal formation to rehearse memories until they are stored permanently for long-term memory

Alzheimer's Disease

Progressive dementia under the age of 65
Senile dementia over the age of 65
Marked by increasing forgetfulness
Loss of neurons in:
- Hippocampus (output to association cortices and diencephalon)
- Parahippocampal areas (input to hippocampus from association and limbic areas)
Decreases cholinergic innervation of the cerebral cortex
Reduction of hippocampal connections causes recent memory loss
The reduction of cholinergic innervation is due to the degeneration of large cholinergic neurons in the Basal Nucleus of Meynert in the anterior perforated substance -Substantia innominata
Absence of neocortical acetylcholine accounts for cognitive deficits

Korsakoff Syndrome

Loss of recent memory and tendency to fabricate false accounts of recent events
Caused by chronic alcoholism and nutritional deficiencies (Vitamin B deficiency)
Affects the hippocampus, mammillary bodies, and medial dorsal thalamic nuclei

Papes Circuit

Alveus of the hippocampus → Fimbria of the Fornix → Crux of the fornix→ Body of the fornix → Column of the fornix (anterior commissure) → Subiculum → Nuclei of the mamillary body → Mamillothalamic tract (bundle of Vicq d Azyr) → Anterior thalamic nucleus → Thalamocingulate radiation → Cingulate Gyrus

Emotion

Any feeling state
Includes: fear, anger, excitement, love, hate
Components:
- Perception
- Feeling
- Autonomic
- Affect
- Reflex

Amygdaloid Nucleus

The Amygdala
Involved in behavior and emotions
Almond-shaped, found beneath the uncus
Divided into:
- Large basolateral group
- Small corticomedial group
- Central group

Amygdaloid Nucleus Connections

Basolateral nuclei:
- Well-developed in humans
- Input from sensory areas of cerebral cortex and thalamus
Corticomedial nucleus:
- Poorly developed
- Input directly from olfactory bulb
- Via lateral olfactory stria
Central nucleus:
- Receives input from both basolateral and corticomedial nuclei

Amygdaloid Nucleus Functions

Programs appropriate behavioral responses
- Animals: primarily corticomedial nuclei
- Humans: purely non-olfactory experiences, from all parts of the cerebral cortex via the cingulum to basolateral nuclei
- Assess the nature of input, pass to the hypothalamus, other limbic centers, and cerebral cortex to elicit a response
Orbitofrontal and cingulum: perceive emotions
Hypothalamus: expresses emotions

Kluver-Bucy Syndrome

Absence of emotional response (fear, rage, aggression)
Compulsion to be overly attentive to all sensory stimuli and examine objects visually, tactilely and orally

Septal Region

Poorly developed in humans
Includes:
- Paraterminal gyrus
- Subcallosal area in front of lamina terminalis
- Septal nuclei
Receives input from the hippocampus
Reciprocal connections with the hypothalamus, amygdala, and cingulate gyrus

Septal Region Connections

Septal region and anterior hypothalamus to midbrain reticular system:
- Via medial forebrain bundle and stria medullaris
Stria passes dorsomedial thalamus to habenular nucleus
Habenulointerpeduncular tract (fasciculus retroflexus) to interpeduncular nuclei of the midbrain reticular formation

Septal Region Functions

Input to:
- Respiratory
- Cardiovascular
- Salivatory
- Other centers to respond to emotional events
Associated with reward or pleasure phenomenon
Connections may be modified by anti-psychotic drugs
May be involved in the euphoria associated with the use of narcotics
Damage can lead to a marked increase in sexual activity in elderly males

Limbic System Summary

Visceral brain
Ring
Crown
Subdivisions:
- Cortical
- Limbic Lobe
- Hippocampus
- Subcortical
- Amygdaloid Nucleus
- Septal Region
- Fornix
- Hypothalamus (MB)
- Olfactory
- Thalamus

Thalamus: The Sensory Relay Station

Relays sensory information for everything seen, heard, tasted, and touched to the cortex
Relates experience for memory storage

Smell

The only sense that bypasses the thalamus
Relayed directly to near the emotion amygdala and mammillary bodies

Inferior Articulating Processes

Lie medial to the superior processes
Correspondingly face laterally and somewhat anteriorly

Lumbar Vertebrae

Have the largest vertebral bodies
Carry the largest axial bones
Spinous process is oriented horizontally, compared to thoracic vertebrae where it faces downward

Adult Spinal Cord

Ends at the level of T12-L1

Anterior Longitudinal Ligament

Originates at the tubercle of the atlas’s anterior arch
Extends ventrally along the entire spinal column to the sacrum
Adherent to the periosteum of vertebral bodies and the ventral intervertebral anulus fibrosus ventrally
Restrains extension
Located anterior to the vertebral body
Prevents anterior dislocation

Sacral Spine

A triangular anteriorly concave bone
Bridges and shares loads between the spine and the pelvis
Articulates with:
- Superiorly: L5 (via facet articulations facing medially and posteriorly)
- Bilaterally: the ilium (via the synovial sacroiliac joints)
- Inferiorly: the non–load-bearing four-level coccyx

Sacral Spine (Continued)

Composed of five vertebrae fused both anteriorly and ventrally by early adulthood.
The mature sacrum encases its respective nerve roots in a central canal terminating around S4.
The sacral hiatus is found below the termination of the central canal.
Also known as the tail bone
Tip of sacral spine is the coccyx

Posterior Longitudinal Ligament

Restrains spinal flexion
Courses along the vertebral bodies dorsally from the axis (with its extension to the intracranial basion termed the tectorial membrane) to the sacrum
Primarily a stabilizer of adjacent levels
Its deep layers are wider and thinner than its superficial layers.
Located over the annulus fibrosus.
Superficial layer spans longer intervertebral intervals.
Ossification potentially:
- Thickens and expands in diameter
- Reduces space and narrows the spinal canal
- Compresses the spinal cord and nerves
- Increases risk of spinal injury

Ligamentum Flavum

Courses dorsal to the spinal cord.
Prevents hyperflexion.
Attaches the laminae of adjacent levels.
Thickness increases from the rostral most ligament at C2 toward the caudal ligament at L5–S1.
Thickest at its insertion in the posterosuperior caudal lamina and medially.
Thinnest superiorly and laterally at each level.
Has a deep, thin midline component that runs continuously throughout the spine in many people.

Spinal Cord and Spinal Nerves

Ensheathed in leptomeninges: -pia, arachnoid, and dura
Paired denticulate ligaments attach the spinal cord to the arachnoid and dural sheath.
- 20-22 pairs
The spinal cord is bathed in CSF which is in continuity with the intracranial subarachnoid compartment.
31 pairs of ventral and dorsal roots emerge from the spinal cord on each side per level.
Dorsal and ventral components combine into a mixed spinal nerve.
These components exit the spinal canal below their correspondingly named levels.

Spinal Cord and Spinal Nerves (Continued)

Due to the developmental ascent of the spinal cord relative to the vertebral column, there is a discrepancy in functional spinal cord segments relative to bony exit points in the vertebral column.
The conus medullaris is the termination of the spinal cord at L1-L2 in adults before fanning into the cauda equina.
It is attached to the sacrum via the filum terminale.

Spinal Cord Structure in Transverse Section

A small central CSF-filled canal, which is lined with ependyma.
Gray matter, which is butterfly-shaped and surrounds the CSF.
White matter, which surrounds the gray matter.

Spinal Cord: Width

Widest in the cervical region, due to the combination of its substantial dorsal horns serving the upper extremities and the afferent white matter dorsal fasciculi innervated at all inferior levels.
Lumbosacral enlargement is present from L2 to S3 because of this region's motor functions.

Filum Terminale

Holds nerve poles in place.
The central canal is filled with CSF; from the fourth ventricle, some CSF flows through a narrow passage called the obex and enters the central canal of the spinal cord.

Spinal Cord Tracts

Follow a medial-lateral topographic principle:
- Afferent pathways enter at higher levels and remain lateral than lower levels.
- Descending efferent tracts innervating lower levels remain lateral, whereas more proximal groups synapse medially onto gray matter more proximally.

Corticospinal Tract

Cortico (cortex) and Spinal (spine) “from cortex to spine,” meaning it’s a descending motor pathway.
The corticospinal tract or pyramidal motor tract has first-order neuron cell bodies predominantly in layer V of the primary motor (Brodmann area 4), premotor, and supplementary motor cortices of the brain.
The axons of these upper motor neurons travel through the corona radiata and posterior limb of the internal capsule, cerebral peduncle, and upper brainstem before decussating in the medullary pyramids and traveling in the contralateral lateral corticospinal tract dorsolaterally in the spinal cord.
A minority of axons descends instead as the ipsilateral anterior corticospinal tract, which lies just lateral to the anterior median fissure before crossing in the anterior white commissure at their level of termination.

Dorsal Column-Lemniscus

The cell bodies of sensory neurons reside in the dorsal root ganglia.

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Description

Test your knowledge on motor disorders such as decerebrate rigidity and various forms of paraplegia, alongside the functions of the limbic system. Discover how these conditions affect muscle tone and emotional behavior. This quiz covers important concepts in neurology related to the nervous system.