Sensory Systems, Motor Systems, and Integration (Reflexes)

Comprehensive vocabulary flashcards covering the anatomical structure of the spinal cord, somatosensory modalities, spinal reflex arcs, ascending sensory pathways, endogenous pain control mechanisms, and corticospinal/corticobulbar motor systems.

Conus Medullaris

The tapered terminal end of the spinal cord located at the L2-L3 vertebral level.

Mixed spinal cord nerve enter and exit the vetebral column through what?

Intervertebral foramen

Nerve plexuses are composed of axons from what of several spinal levels?

Ventral ramus

What is somatsensation?

Specialized somatic sensory neurons for touch pressure pain temp and propriceotion

All somats enter the spinal cord where?

Dorsal sensory root

Cauda Equina

The bundle of spinal nerve roots extending inferiorly from the conus medullaris within the vertebral canal.

Brachial Plexus

A network of nerve fibers formed by the ventral rami of spinal levels C5-T1 that provides motor and sensory innervation to the upper limbs.

What is proprioceotion?

Position sense

What are the two main propriceptors?

Muscle and tendon

What proprietor is found in joints?

Kinaesthetic receptors

Lumbosacral Plexus

A network of nerve fibers formed by the ventral rami of spinal levels L1-S4 that provides motor and sensory innervation to the lower limbs.

Dermatome

A specific area of skin supplied by somatic sensory neurons from a single, discrete spinal cord segment.

Somatosensation

Somatic sensory perception comprising five principal modalities: touch, pressure, proprioception, pain, and temperature.

Muscle Spindle

A specialized proprioceptor situated within skeletal muscle that detects changes in muscle length.

Tendon Organ

A proprioceptive sensory receptor located at muscle-tendon junctions that measures muscle tension and force.

What is a mono synaptic reflex?

A monosynaptic reflex is a reflex where the sensory neuron communicates directly with the motor neuron through one synapse.

Stretch Reflex

A monosynaptic, ipsilateral somatic reflex initiated by muscle spindle stretch that causes contraction of the stretched muscle.

What is a fast, involuntary and unplanned sequence of actions called?

Reflex

What does the integrating centre of the spinal cord do?

Relays impulses from sensory or motor neurons

Reciprocal Innervation

A reflex circuit organization in which the contraction of an agonist muscle is accompanied by interneuron-mediated inhibition of its antagonistic muscle group.

Crossed-Extensor Reflex

A polysynaptic reflex mechanism in which a painful stimulus induces an ipsilateral withdrawal reflex along with a contralateral extensor response to maintain body balance.

What is a ipsilateral reflex?

A withdrawal reflex to move away from a painful stimulus

What does the anterolateral pathway focus on?

Pain and temp

Where do all somats terminate?

Through the thalamus at the primary somat cortex

Dorsal Column-Medial Lemniscal Pathway

An ascending somatosensory tract that transmits fine touch, pressure, and conscious proprioception signals, decussating in the medulla.

Fasciculus Gracilis

The medial tract of the dorsal column conveying fine touch, pressure, and proprioception from the lower limbs to the gracile nucleus.

Fasciculus Cuneatus

The lateral tract of the dorsal column conveying fine touch, pressure, and proprioception from the upper limbs to the cuneate nucleus.

Anterolateral Pathway

An ascending sensory pathway, including the spinothalamic tract, responsible for transmitting pain and temperature sensations, decussating at the spinal cord level.

Which pathway is conscious?

Dorsal column/medial lemniscus pathways

Spinocerebellar Tract

An ascending sensory pathway that conducts subconscious proprioceptive inputs from muscle spindles and tendon organs directly to the cerebellum.

Gate Control Theory of Pain

A spinal mechanism of pain modulation where non-painful fast mechanoreceptive inputs (A fibers) stimulate inhibitory interneurons in the dorsal horn, closing the gate to slow C fiber pain transmission.

Periaqueductal Gray Matter (PAG)

A midbrain region central to endogenous pain control that projects descending pathways releasing opioids (endorphins and enkephalins) to inhibit nociceptive transmission in the spinal cord.

Corticospinal Tract

The primary voluntary motor pathway originating in the precentral gyrus that descends through the spinal cord to control muscles of the upper limbs, trunk, and lower limbs.

Corticobulbar Tract

A motor pathway originating in the primary motor cortex that projects to brainstem cranial nerve nuclei to control muscles of the head and neck.

Upper Motor Neuron (UMN)

A motor neuron with its cell body located in the primary motor cortex or brainstem whose axon descends via corticospinal or corticobulbar tracts to synapse onto lower motor neurons.

Lower Motor Neuron (LMN)

A motor neuron located in the anterior horn of the spinal cord or cranial nerve nuclei of the brainstem that directly innervates extrafusal skeletal muscle fibers.

Upper Motor Neuron Lesion

Damage to upper motor neurons or the corticospinal tract, leading to spastic paralysis characterized by hypertonia, hyperreflexia, clonus, and a positive Babinski sign.

Lower Motor Neuron Lesion

Damage to lower motor neuron cell bodies or peripheral axons, leading to flaccid paralysis characterized by hypotonia, hyporeflexia, fasciculations, and severe muscle atrophy.

Spastic Paralysis

A form of paralysis caused by upper motor neuron damage, characterized by increased muscle tone (hypertonia) and exaggerated tendon reflexes (hyperreflexia).

Flaccid Paralysis

A form of paralysis caused by lower motor neuron damage, characterized by loss of muscle tone (hypotonia) and loss of tendon reflexes (hyporeflexia).