Sensory Pathways and Somatic Nervous System Overview

A set of 75 question-and-answer flashcards covering sensory receptors, sensory and motor pathways, types of stimuli, and neural control mechanisms in the somatic nervous system.

What is the primary role of the somatic nervous system (SNS)?

To control contractions of skeletal muscles.

What are sensory pathways?

Series of neurons that relay sensory information from receptors to the CNS.

In neural terminology, what is a sensation?

Arriving information from receptors to CNS

What is perception?

Conscious awareness of a sensation.

Name the general senses. (6) (T-P-V)

Touch, Temp, Pain, Pressure, Proprioception, Vibration

List the special senses.

Olfaction, gustation, vision, equilibrium, and hearing.

Define receptor specificity.

The characteristic sensitivity of a receptor to a particular type of stimulus.

How does receptive-field size affect stimulus localization?

A larger receptive field makes a stimulus harder to localize.

What is transduction in sensory processing?

When receptor turns stimulus into AP

What type of adaptation occurs in the peripheral nervous system?

Peripheral adaptation.

What type of adaptation occurs in the central nervous system?

Central adaptation.

Describe tonic receptors.

Tonic receptors are slow-adapting and always active, give info background stimulation.

Describe phasic receptors.

Usually inactive, fast adapting receptors that respond to stimulus changes

What information do exteroceptors provide?

Information about the external environment.

What do proprioceptors report?

Positions of skeletal muscles and joints.

What do interoceptors monitor?

Visceral organs and their functions.

Name the four classes of general sensory receptors by stimulus type.

1. Nociceptors

2. Thermoreceptor

3. Mechanoreceptor

4. Chemoreceptor

Where are nociceptors especially common? (4)

Skin, Joint capsule, Periostea of bone, blood vessel wall

Which fiber type carries fast pain?

Myelinated Type A fibers.

Which fiber type carries slow pain?

Unmyelinated Type C fibers.

Where are thermoreceptors found? (4)

Hypothalamus, Dermis, SKM, Liver.

What type of ion channel do mechanoreceptors use?

Mechanically gated ion channels.

What three sensations are provided by tactile receptors? (3)

Touch, pressure, and vibration.

What do baroreceptors detect?

Pressure changes in blood vessels and hollow organs.

What do proprioceptors monitor?

Positions of joints and skeletal muscles.

What stimulates chemoreceptors? (2)

Water- and lipid-soluble chemicals in body fluids.

Which two arterial structures contain peripheral chemoreceptors? (2)

Carotid bodies and aortic bodies.

What information do first-order neurons carry?

Sensory info from the receptor to the CNS.

Where are second-order neurons located?

In the spinal cord or brainstem.

Where are third-order neurons located?

In the thalamus.

List the three major somatic sensory pathways.

Spinothalamic, posterior column, and spinocerebellar pathways.

What sensations are carried by the spinothalamic pathway? (4)

Crude touch, pressure, pain, and temperature.

Which spinothalamic tract carries pain and temperature?

The lateral spinothalamic tract.

What is referred pain?

Perception of pain in an uninjured area because it shares spinal segments with the source.

What sensations are carried by the posterior column pathway? (4)

Fine touch, , pressure, proprioception, and vibration.

Which fasciculus carries sensations from the lower body?

The gracile fasciculus.

What is a sensory homunculus?

A map showing how the primary sensory cortex represents body regions.

What does the spinocerebellar pathway send and to where?

Proprioceptive information to the cerebellum.

Do posterior spinocerebellar fibers cross the midline?

No, they remain on the same side (ipsilateral).

How many times can anterior spinocerebellar tract fibers cross over?

Twice—once in the spinal cord and once in the cerebellum.

Which medullary nucleus processes visceral sensory information? :(

The solitary nucleus.

Which cranial nerves carry visceral sensory input to the solitary nucleus?

Cranial nerves V, VII, IX, and X.

What two neurons form every somatic motor pathway?

An upper motor neuron and a lower motor neuron.

Where is the cell body of an upper motor neuron located?

In a CNS processing center such as the primary motor cortex.

What is the effect of lower motor neuron damage?

Loss of voluntary and reflex control over its motor unit.

Name the three integrated motor pathways.

Corticospinal, medial, and lateral pathways.

What is another name for the corticospinal pathway?

The pyramidal system.

Where does the corticospinal pathway begin?

Pyramidal cells of the primary motor cortex.

List the three pairs of corticospinal tracts.

Corticobulbar, lateral corticospinal, and anterior corticospinal tracts.

What movements are controlled by corticobulbar tracts?

(what type of movement, of what muscles (5)

Conscious movement of the eyes, jaw, face, and some neck and pharynx muscles.

Where do lateral corticospinal tract axons decussate?

At the pyramids of the medulla oblongata.

Where do anterior corticospinal tract axons cross over?

In the anterior white commissure at their target spinal segment.

What is the motor homunculus?

A map of primary motor cortex showing control areas and amount of fine motor control needed.

What is the primary function of the medial pathway? controls muscle ___, and ___ movement of (3)

Control muscle tone and gross movements of the neck, trunk, and proximal limbs.

Which tracts compose the medial pathway? (3)

Vestibulospinal, tectospinal, and reticulospinal tracts.

Which nuclei give rise to vestibulospinal tracts?

Vestibular nuclei.

What do vestibulospinal tracts help maintain?

Posture and balance in response to head movements.

From which structures do the superior and inferior colliculi receive sensory input?

Superior colliculi receive visual input; inferior colliculi receive auditory input.

Through which tracts do colliculi influence motor output?

Tectospinal tracts.

What is the reticular formation's role in motor control?

It sends uncrossed reticulospinal tracts that influence muscle tone and reflexes.

What does the lateral pathway control? (3)

Muscle tone and precise movements of distal limbs.

Which tract is the principal component of the lateral pathway?

The rubrospinal tract.

Where do rubrospinal tract axons originate?

In the red nuclei of the midbrain.

What is the function of basal nuclei in movement?

Provide background patterns and adjust voluntary motor commands.

How do basal nuclei influence movement via the cortex?

By sending axons to the premotor cortex to modify corticospinal instructions.

How do basal nuclei influence movement via brainstem pathways?

By altering excitatory or inhibitory output of reticulospinal tracts.

Which three types of input does the cerebellum monitor?

Proprioceptive, visual, and vestibular information.

How does the cerebellum improve movement with practice?

By learning through trial and error, fine-tuning complex movements over time.

Name the six types of tactile receptors in the skin.

Free nerve endings, root hair plexus, tactile discs, bulbous corpuscles (Ruffini), lamellar corpuscles (Pacinian), and tactile corpuscles (Meissner).

Which tactile receptor best detects initial movement of hairs?

Root hair plexus nerve endings.

Which tactile receptors are extremely sensitive to shape and texture?

Tactile discs.

Which tactile receptor responds to deep pressure and high-frequency vibration?

Lamellar corpuscle (Pacinian corpuscle).

Where are tactile corpuscles most abundant?

Eyelids, lips, fingertips, nipples, and external genitalia.

What do Golgi tendon organs monitor?

Tension during muscle contraction at muscle-tendon junctions.

Which receptor monitors pressure in distensible organs and adapts rapidly?

Baroreceptors.