Sensory Pathways & The Somatic Nervous System

These flashcards encompass key terms and concepts related to sensory pathways and the somatic nervous system, providing a comprehensive review tool for the subject matter.

Peripheral Nervous System (PNS)

Links the central nervous system (CNS) to the outside world.

Sensory Receptors

Respond to internal and external stimuli and are sensitive to specific stimuli.

Receptor Field

Area monitored by a specific receptor; larger fields mean less fine-tuned sensations.

Sensation

Awareness of the stimulus (incoming information).

Perception

Interpretation or conscious awareness of the stimulus.

Simple Receptors

Receptors that provide information about general senses.

Complex Receptors

Receptors that form sense organs for vision, hearing, smell, and taste.

Adaptation

Reduction in sensitivity in the presence of a constant stimulus.

Peripheral Adaptation

Sensory receptors become less responsive to unchanging stimuli.

Central Adaptation

Conscious awareness of a stimulus disappears, restricting information reaching the CNS.

Proprioceptors

Receptors that do not adapt and monitor body position.

Tonic Receptors

Always active and slow adapting; rate of action potential changes with stimulus intensity.

Phasic Receptors

Normally inactive and fast adapting; active only when conditions change.

Mechanoreceptors

Generate impulses when deformed by touch, pressure, vibration, or stretch.

Tactile Receptors

Types of mechanoreceptors that respond to touch, pressure, and vibration.

Free Nerve Endings

Tonic mechanoreceptors that respond to touch and pressure over a large field.

Root Hair Plexus

Phasic mechanoreceptors that respond to movement of hair.

Tactile Discs (Merkel’s)

Tonic mechanoreceptors responsible for fine touch.

Tactile Corpuscles (Meissner’s)

Phasic mechanoreceptors sensitive to fine touch, pressure, and texture.

Lamellated Corpuscles (Pacinian)

Phasic mechanoreceptors detecting deep pressure and visceral sensations.

Ruffini Corpuscles

Tonic mechanoreceptors that detect pressure and skin or joint distortion.

Baroreceptors

Detect pressure changes in blood vessels and organs of the urinary, reproductive, and digestive systems.

Muscle Spindles

Proprioceptors found in skeletal muscles, monitoring stretch.

Golgi Tendon Organs

Proprioceptors that detect tension in tendons, similar to Ruffini receptors.

Receptors in Joint Capsules

Monitor movement, pressure, and tension in joints.

Thermoreceptors

Detect changes in temperature with more cold receptors than hot.

Chemoreceptors

Detect changes in chemical concentrations in body fluids.

Nociceptors

Receptors that cause the sensation of pain.

Fast Pain

Type A fibers that convey sharp or prickling pain.

Slow Pain

Type C fibers that convey burning or aching pain.

Exteroceptors

Receive stimuli from outside the body and are located near the body surface.

Interoceptors

Respond to internal stimuli from organs and blood vessels, detecting chemical changes, stretch, and temperature.

First-order Neuron

Carries impulse to the CNS with cell body located in dorsal root ganglion or cranial nerve ganglion.

Second-order Neuron

Located in spinal cord or brainstem; an interneuron synapsing with the first-order neuron.

Decussation

Crossing over to the opposite side of the CNS.

Third-order Neuron

Located in the thalamus; synapses with the second-order neuron.

Spinal Tracts

Conduct impulses between peripheral nerves and the brain.

Ascending Tracts

Sensory pathways that carry information to the brain.

Anterolateral Pathway

Pathway where first-order neurons synapse with second-order neurons in posterior gray matter.

Lateral Spinothalamic Tract

Part of the anterolateral pathway that transmits pain and temperature sensations.

Anterior Spinothalamic Tract

Transmits crude touch and pressure sensations.

Spinocerebellar Pathway

Carries information about muscle tone and posture to the cerebellar cortex.

Posterior Spinocerebellar Tract

Axons that do not cross over in the spinocerebellar pathway.

Anterior Spinocerebellar Tract

Most axons cross over in the spinocerebellar pathway.

Posterior Column Pathway

Contains fine touch and pressure sensations, body position information.

Fasciculus Gracilis

Inferior half of the spinal tracts involved in sensory processing.

Fasciculus Cuneatus

Superior half of the spinal tracts involved in sensory processing.

Somatic Nervous System (SNS)

Controls skeletal muscle activity.

CNS

Central nervous system that includes the brain and spinal cord.

Lower Motor Neuron

Neuron located in the brainstem or spinal cord nucleus that activates skeletal muscles.

Corticospinal Pathway

Pathway that controls voluntary movement.

Corticobulbar Tracts

Neurons that synapse with lower motor neurons in cranial nerves controlling head and neck muscles.

Lateral Corticospinal Tracts

Pathway where axons cross over near the medulla.

Anterior Corticospinal Tracts

Pathway where axons cross lower in the spinal cord.

Medial Pathways

Control gross movements of the trunk and proximal limbs for balance and posture.

Vestibulospinal Tract

Pathway that maintains balance.

Tectospinal Tract

Coordinates head and neck movement in response to visual and auditory stimuli.

Reticulospinal Tract

Maintains muscle tone while conscious.

Lateral Pathway

Controls voluntary movements of distal limb muscles.

Rubrospinal Tract

Pathway for involuntary impulses to skeletal muscles controlling tone and posture.

Motor Homunculus

Graphical representation of motor areas in the brain showing areas that cause muscle contraction.

Sensory Homunculus

Graphical representation of sensory processing areas in the brain.

Basal Nuclei

Subcortical nuclei that adjust the activity of upper motor neurons.

Upper Motor Neurons

Neurons in the CNS that control lower motor neurons.

Inhibitory Effect

Effect of basal nuclei preventing unnecessary movements.

Huntington’s Chorea

Disorder causing abnormal movement due to basal nuclei dysfunction.

Parkinson’s Disease

Disorder causing too little movement due to basal nuclei dysfunction.

Fine Touch

Sensory perception of delicate sensations due to small receptor fields.

Temperature Sensation

Perception generated by thermoreceptors detecting heat and cold.

Pain Sensation

Perception generated by nociceptors in response to harmful stimuli.

Tactile Disc Function

Detects fine touch through small, localized sensations in skin.

Proprioceptor Function

Provides information about body position and movement.

Central Nervous System Function

Processes and integrates information from the sensory and motor pathways.

Two-point Discrimination

Ability to discern two distinct points on the skin, depending on receptor density.

Pressure Sensation

Perception of force applied to the skin, mediated by various mechanoreceptors.

Dorsal Roots

Sensory roots that bring information from peripheral nerves to the spinal cord.

Gray Matter

Areas of the CNS where neuronal cell bodies are concentrated.

Brainstem Function

Acts as a relay center for sensory information and motor control.

Cingulate Gyrus

Part of the brain associated with emotional processing and pain perception.

Thalamus Function

Acts as a relay station for sensory impulses before they reach the cortex.

Motor Unit

The basic unit of movement consisting of a motor neuron and the muscle fibers it innervates.

Cerebellar Cortex

Part of the brain involved in coordination and balance.

Corticobulbar Pathway Function

Involved in the control of facial and neck muscles.

Lateral Corticospinal Tract Function

Controls movement of the limbs through voluntary motor pathways.

Anterior White Commissure

Area where some corticospinal axons cross over to the opposite side of the spinal cord.

Reticular Formation

Network in the brainstem involved in regulating wakefulness and filtering incoming stimuli.

Bilateral Projection

Refers to how sensations and motor control influence both sides of the body equally.

Spinal Cord Function

Transmits signals between the brain and peripheral nervous system.

Nerve Ganglia

Clusters of neuronal cell bodies located outside the CNS.

Action Potential

A rapid rise and fall in voltage or membrane potential across a cellular membrane.

Neurotransmitter

Chemical messenger that transmits signals across a synapse.

Endorphins

Hormones produced by the body that act as natural painkillers.

Somatosensory Cortex

Region of the brain responsible for processing sensory input from the body.

Lower Motor Neuron Function

Targets skeletal muscles for voluntary movement.

Upper Motor Neuron Function

Regulates lower motor neurons to facilitate voluntary movements.

Pain Pathway

The route through which nociceptive information is sent to the brain.

Ventral Horn of Spinal Cord

Contains lower motor neurons that send axons out to skeletal muscles.

Efferent Neurons

Neurons that carry signals away from the CNS to effectors like muscles.

Afferent Neurons

Neurons that transmit sensory information to the CNS from sensory receptors.

Integration Center

Part of the nervous system where sensory input is processed and a motor response is generated.