NEU Exam 3 Terms

These flashcards cover key vocabulary related to the somatosensory and motor systems, aiding in understanding the underlying concepts.

Afferent Nervous System

The part of the nervous system responsible for sensory information coming into the central nervous system.

Efferent Nervous System

The part of the nervous system responsible for motor commands sent out from the central nervous system.

Inner-Ear Balance Organs

detect angular and linear accelerations of the head

Proprioception

The body's ability to sense its position and movement in space.

Somatosensory receptors

ganglion cells which act as primary sensory afferents, each include a receptor area, generator area, and a cell body leading to the central nervous system

Sensory Modalities

includes the sensory receptors responsible for detecting different types of stimuli including skin receptors, muscle and joint receptors, and visceral receptors

Visceral Receptors

include detection of pressure, temperature, and chemicals (ex: pH, O2), plus pain receptors found throughout the body except the central nervous system

Thermal Receptors

Sensory receptors that detect temperature changes.

Nociceptors

Sensory receptors that respond to harmful stimuli, causing a sensation of pain.

Merkel's Disk

A type of touch receptor responsible for detecting pressure and texture (small field size, slow adaptation)

Meissner Corpuscles

detect light touch and flutter (small receptive field, rapid adaptation)

Pacinian Corpuscle

A touch receptor sensitive to vibration (large receptive field, rapid adaptation)

Ruffini Endings

Receptors that detect stretch in the skin (large receptive field, slow adaptation)

Aa and Group I

proprioceptors of skeletal muscle with slowest speed (80 -120 m/sec) and largest diameter (13-20)

AB and Group II

mechanoreceptors of skin that transmit touch sensation with intermediate speed (35-75 m/sec) and moderate diameter (6-12 µm).

AO and Group III

nociceptors that detect pain and temperature, with fast conduction velocity (5-30 m/sec) and smaller diameter (1-5 µm).

C and Group IV

nociceptors (temperature, pain, and itch) with slowest conduction velocity (0.5-2 m/sec) and smallest diameter (0.2-1.5 µm) that transmit dull pain and temperature sensations.

Convergence

in the somatosensory system, a single neuron can receive information from many different neurons, often integrating signals from various receptors, pathways, or body regions

Dermatome

Each spinal nerve carries sensory information from a specific strip or segment of skin

Shingles

this condition, caused by reactivation of herpes zoster virus, expemplifies the segmental organization of dermatomes, causing symptoms along a dermatome’s skin area

Cortical Maps

representations of different body areas in the cortex, where each region corresponds to a specific part of the body.

Plastic

The cortical maps are __, indicating reorganization capabilities of the somatosensory cortex in response to injury or sensory experience

Ia Fibers

encode the velocity of stretch

Grp II fibers

encode the amplitude of the stretch

Muscle Spindles

Located within muscle fibers, acting as length detectors with Ia fibers (group I) and II fibers (group II) encoding length and stretch information respectively

Golgi Tendon Organs

Proprioceptors located in tendons that sense muscle tension and force.

Joint Receptors

embedded in joint cartilage acting similarly to touch receptors (Pacini and Ruffini type receptors)

Stretch Reflex

An involuntary response where muscles contract in response to being stretched.

Reciprocal Inhibition

how sensory information drives motor movement through inhibitory interneurons that inhibit antagonist muscles to facilitate movement

Ib Inhibition

A mechanism where activation of Ib afferent neurons inhibits alpha motor neurons of the same muscle, preventing excessive contraction.

Mechanical Nociceptors

sensory receptors that respond to intense pressure or sharp objects picked up by AO fibers when experiencing a sharp, localized “first pain”

Thermal Nociceptors

sensory receptors that respond to extreme heat or cold picked up by AO or C fibers when experiencing burning or stinging pain

Polymodal

sensory receptors that respond to chemical, thermal, or mechanical damage picked up by C fibers when experiencing dull, aching “second pain”

Silent (Sleeping) Nociceptors

sensory receptors that respond to normally inactive, but become sensitized after injury or inflammation picked up by C fibers when experiencing persistant or chronic pain

Muscle Spindles

Located within muscle fibers, acting as length detectors with Ia fibers (group I) and II fibers (group II) encoding length and stretch information respectively.

Nociceptive Pathways

Pain signals travel via two pathways. The rapid reflexive pathways that act quickly, while higher cortical pathways involve more complex processing

Nociception

Objective physiological detection of damage or potential harm that can be evidenced by visible symptoms such as swelling or redness that involves specialized receptors and neural pathways

Pain

a subjective experience influenced by social, environmental, and cultural factors. The perception of pain varies dramatically between individuals, influenced by upbringing and educational contexts

Ascending Pathways

Nociceptive signals cross within the spinal cord and ascend to the brain - pain signals cross at the spinal cord level while touch signals cross at the medulla

Descending Pathways

brain can influence the perception of pain (periaqueductal gray area in the brain) by modulating incoming pain signals

Postaglandins

target of NSAIDs → block COX → reduce pain and inflammation by lowering nociceptor’s activation threshold

Bradykinin

a potent inflammatory mediator formed from kininogen by kallikrein, that directly stimulates nociceptors and amplifies the effects of prostaglandins and histamine, leading to pain, vasodilation, and edema.

Histamine

released by mast cells during injury or allergic reactions, binds to H1 receptors on nociceptors, contributing to

itching, burning, and redness.

Cytokines and chemokines

signaling proteins released by immune cells that promote binflammation, nociceptor sensitization, and immune cell recruitment

Substance P and CGRP

amplify swelling and inflammation

Dorsal Column (gracile and cuneate fasciculi)

a spinal cord tract that crosses in medulla which are responsible for fine touch, vibration, and proprioception

Spinothalamic Tract

a spinal cord tract that carries pain and temperature sensations, crossing over within 1-2 segments in the spinal cord

Substantia Gelatinosa

A dorsal horn region in the spinal cord that filters and modulates incoming pain signals, determining their intensity and transmission to the brain.

Dorsal Column-Medial Lemniscal Pathway

the neural pathway that transmits fine touch, vibration, and proprioceptive information from the body to the brain, synapsing in the medulla before ascending to the thalamus.

Spinothalamic Pathway

the pathway responsible for transmitting pain and temperature sensations from the spinal cord to the thalamus.

Brown Sequard Syndrome

results from hemisection (damage to one side) of the spinal cord. It causes ipsilateral (same-side) loss of motor control, proprioception, and vibration sense below the injury, and contralateral (opposite-side) loss of pain and temperature sensation below the injury.

Referred Pain

The convergence of afferent sensory neurons firing in spinal cord leads to the misinterpretation of pain signals, which can result in sensations occurring in areas distant from the source of the actual injury. Typically in same area.

Inflammatory Response

when tissue damage occurs, a cascade of inflammatory signals is triggered, leading to swelling, redness, and pain. This serves to amplify nociceptive signals to ensure awareness of injury

Gate Control Theory

A theory suggesting that non-painful input closes the gate to painful input, thus modulating pain perception.

Periaqueductal Gray

nucleus of the brain stem

Somatotopy

The mapping of the body's surface sensations to specific areas of the primary somatosensory cortex.

Placebo Effect

activate’s the brain’s endorphin system, triggering endogenous opioid release in pain-modulating regions of the CNS. This natural opioid activity suppresses pain transmission - demonstrating that belief and expectation can produce real, measurable biochemical analgesia

Premotor

learns from previous experience, works with supplementary motor areas to plan and coordinate movements.

Primary Motor

Actually does the action and is responsible for executing voluntary motor commands, directly influencing muscle contractions.

Supplementary Motor

succession of movements that are planned and organized in sequence, contributing to the coordination of complex actions.

Dorsal Horn

afferent sensory that goes up the spinal cord to process sensory information.

Reflex activity

innate, species-specific, and stereotypical (examples: knee-jerk reflex when the pattelar tendon is tapped)

Automatic Activity (Rhythmic Motion)

involuntary and rhythmic, and coordinated by cerebellum

Voluntary Activity

conscious, goal-directed actions require planning from higher brain centers, involving higher-level brain areas (like frontal cortex)

Postural Activity

maintaining posture against gravity, involving continuous muscle tone and contraction

Electromyography

measures electrical activity of muscles to assess the functionality of motor neurons and neuromuscular control during activities

Monosynaptic reflex arc

involves a single synapse between a sensory and motor neuron (ex: the knee-jerk reflex)

Disynaptic Reflex Arc

contains two synapses, involving a inhibitory interneuron (ex: withdrawal reflex)

Reflexes

involuntary, unplanned sequences of movements elicited by sensory stimuli that rely on neural pathways called reflex arcs

Knee-Jerk

Triggered by tap on the knee detecting through muscle patients, processed in the spinal cord, leading to a quick contraction of the quadiceps

Newborn Walking Reflex

a primitive reflex, present at birth until ~2 months, where a baby appears to "step" when held upright with feet touching a surface, serving as a precursor for later voluntary walking and indicating a healthy nervous system.

Neural Plasticity

The ability of the nervous system to change its activity in response to intrinsic or extrinsic stimuli.

Basal Ganglia

A group of nuclei in the brain that coordinate voluntary movements.

Epidermal-Dermal Border

Area where skin receptors are located, important for sensory reception.

White Matter

tracts to send information; include: axons and myelin sheath

Grey Matter

Cell bodies

Sulcus

brain grooves

Gyrus

Bumps in brains

Somatosensory

between the central sulcus and the postcentral gyrus

Cerebellum

A structure located at the back of the brain that is the “clock” on central nervous system that is responsible for coordination, balance, and fine motor skills.

Layers of the Cerebellum

Molecular Layer, Granular Layer, Pak

Molecular Layer

outermost layer, has climbing fibers that run through the cerebellum, ties everything together all information between the two layers

Purkinje Layer

middle layer, contains Purkinje cells that integrate signals from the molecular and granular layers, playing a crucial role in motor coordination.

Granular Layer

innermost layer, contains dense clusters of granule cells that receive input from mossy fibers and send axons to the molecular layer.

Motor Cortex

closer to the frontal lobe and responsible for planning, controlling, and executing voluntary movements.

Central Sulcus

divide between the motor cortex and somatosensory cortex

Somatosensory Cortex

between the central sulcus and the postcentral gyrus

Reflex Arc

demonstrate various types of reflexes (monosynaptic, polysynaptic) illustrating how sensory input is processed quickly to yield motor responses

Pyramidal Tract (Motor Tract)

efferent - goes through the brain and spinal cord to facilitate movement and coordination within the peripheral nervous system

Parkinson’s Disease

a result of the loss of dopamine in the substantia nigra (which makes dopamine)

El Dopa

patients with Parkinson’s are prescribed this, it is an agonist for dopamine that allows there to be more dopamine

Deep Brain Stimulation

It provides electrical signals to the globus paladus and the subthalamic nucleus, helping to alleviate motor symptoms and improve quality of life for those affected by Parkinson's Disease.