Sensory Systems Flashcards

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Questions and Answers

What do first order neurons conduct?

Impulses from the spinal cord

Impulses from the cerebral cortex

Impulses from the thalamus

Impulses from receptors of the skin (correct)

What do second order neurons carry information to?

Thalamus

What do third order neurons carry sensory information to?

Cerebral cortex

Referred pain is perceived as occurring on the skin surface.

True Signup and view all the answers

What are simple mechanoreceptors?

Sensory receptors that respond to mechanical forces, such as pressure or distortion. Signup and view all the answers

What are complex mechanoreceptors?

Specialized nerve endings which are encapsulated. Signup and view all the answers

A detectable change in the internal or external environment is known as a ______.

stimulus energy Signup and view all the answers

What is an adequate stimulus?

The form of energy a receptor is most responsive to. Signup and view all the answers

What is receptor potential?

Graded in sensory receptor membrane potential. Signup and view all the answers

What does labeled line coding refer to?

1:1 association of receptor with sensation. Signup and view all the answers

Match the mechanoreceptors with their functions:

Meissner's corpuscle = Fine touch Merkel's disks = Pressure/texture Ruffini endings = Sense stretch Pacinian corpuscle = Sense vibrations Signup and view all the answers

What is the function of free nerve endings in the skin?

They include hair follicles, nociceptors, and thermoreceptors. Signup and view all the answers

How do we encode the length of the stimulus in a first order sensory neuron?

Stimulus length = length of graded potential = length of bursts of action potentials. Signup and view all the answers

How is intensity encoded?

Amplitude of graded potential relates to frequency of action potentials. Signup and view all the answers

Tonic receptors adapt quickly to stimuli.

False Signup and view all the answers

Phasic receptors adapt slowly to stimuli.

False Signup and view all the answers

How do overlap and convergence of receptor fields influence sensory sensitivity?

Convergence can weaken two-point discrimination while overlap can create a larger receptive field. Signup and view all the answers

What is the function of sensory fiber type Aalpha (I)?

It is large diameter and myelinated, providing fast conduction for proprioception. Signup and view all the answers

What is the function of sensory fiber Abeta (II)?

It is large diameter and myelinated, responsible for fine touch. Signup and view all the answers

What is the function of Adelta fiber (III)?

It is small diameter, lightly myelinated, responsible for fast pain. Signup and view all the answers

What is the function of C (type IV) fiber?

It is small diameter and unmyelinated, responsible for slow pain. Signup and view all the answers

Differentiate between dermatome and receptive field:

Dermatome = Skin section for one DRG Receptive field = One axon Signup and view all the answers

What is lateral inhibition?

Domes of silence created by second order neurons via GABA. Signup and view all the answers

Map the dorsal column-medial lemniscal pathway.

First order neurons go to cuneate/gracilis nucleus ipsilaterally; second order neurons cross over and ascend in medial lemniscus to thalamus; third order neurons go from thalamus to primary sensory cortex. Signup and view all the answers

Map the spinothalamic pathway.

First order neurons synapse in dorsal horn; second order neurons decussate and ascend contralaterally; third order neurons go from thalamus to primary sensory cortex. Signup and view all the answers

Map the pathway that conveys fine touch sensation from the head/face.

First order neurons from trigeminal ganglion synapse onto second order neurons in the ipsilateral chief trigeminal nucleus; second order neurons cross over; third order neurons go from thalamus to primary sensory cortex. Signup and view all the answers

Where are the cell bodies of the first order sensory neurons of the face?

Trigeminal ganglion Signup and view all the answers

Explain the topographic organization of sensory transmission from the spinal cord to sensory cortex.

<Response Expected from Student> Signup and view all the answers

Map the pathway for pain and temperature of the face.

First order neuron from trigeminal ganglion descends to spinal trigeminal nucleus; second order neuron crosses and ascends contralaterally; third order from thalamus to sensory cortex. Signup and view all the answers

Study Notes

Neuron Types in Sensory Systems

First-order neurons carry impulses from skin receptors and proprioceptors to the spinal cord or brain stem, synapsing with second-order neurons.
Second-order neurons transmit information from the central nervous system to the thalamus and decussate, crossing to the opposite side of the CNS.
Third-order neurons relay sensory information from the thalamus to the cerebral cortex.

Pain Perception and Mechanisms

Referred pain occurs when visceral pain is felt on the skin, as visceral organs share sensory afferents with specific dermatomes (e.g., heart attack may cause shoulder and arm pain).
Lateral inhibition enhances contrast in sensory input through GABA activity by second-order neurons.

Mechanoreceptors

Simple mechanoreceptors include free nerve endings for pain and temperature, as well as hair follicles detecting mechanical stimuli.
Complex mechanoreceptors are specialized nerve endings encapsulated for more refined sensitivity, such as Meissner's corpuscles for light touch and Pacinian corpuscles for vibration.

Signal Processing and Encoding

Stimulus energy refers to detectable environmental changes processed into electrical signals via stimulus transduction.
Adequate stimulus is the form of energy to which a receptor is most responsive.
Receptor potential indicates the graded potential change in sensory receptor membranes.
Labeled line coding ensures a 1:1 association between receptors and sensations, maintaining specific sensory perceptions.

Skin Mechanoreceptors

Meissner's corpuscle detects fine touch.
Merkel's disks respond to pressure and texture.
Ruffini endings sense skin stretch, part of proprioception.
Pacinian corpuscles detect vibrations, often located in joints.
Free nerve endings encompass nociceptors (pain), thermoreceptors (temperature), and those in hair follicles.

Receptor Adaptation

Tonic receptors are slow to adapt (e.g., persistent pain or temperature sensation).
Phasic receptors adapt quickly, becoming less responsive after initial stimulation (e.g., feeling the texture of clothing).

Sensory Fibers

Aalpha fibers (I): Large diameter, myelinated; responsible for proprioception.
Abeta fibers (II): Large diameter, myelinated; convey fine touch sensations.
Adelta fibers (III): Small diameter, lightly myelinated; transmit fast pain and temperature signals.
C fibers (IV): Small diameter, unmyelinated; associated with slow pain.

Sensory Field Concepts

Dermatome represents skin regions related to a specific dorsal root ganglion (DRG).
Receptive field refers to the area influenced by one sensory neuron.

Sensory Pathways

Dorsal column-medial lemniscal pathway: First-order neurons ascend ipsilaterally, synapsing in the cuneate/gracilis nucleus; second-order neurons cross midline and ascend to thalamus; third-order neurons project to the primary sensory cortex.
Spinothalamic pathway: First-order neurons synapse in the dorsal horn upon entering the CNS; second-order neurons decussate and ascend to thalamus; third-order neurons transmit to sensory cortex.
Pathway for fine touch from head/face: First-order neurons from the trigeminal ganglion synapse in the ipsilateral chief trigeminal nucleus; second-order neurons cross over ascending to VPM of thalamus; third-order neurons project to the sensory cortex.
Pain and temperature pathway for face: First-order neurons descend into the ipsilateral spinal trigeminal nucleus; second-order neurons cross and ascend contralaterally to the VPM of thalamus; third-order neurons relay to sensory cortex.

Cellular Structures

First-order sensory neuron cell bodies for the face are located in the trigeminal ganglion, unlike the DRG for other body parts.

Topographic Organization

Sensory information follows a structured pathway from the spinal cord through multiple relay points to the sensory cortex, maintaining regional organization throughout the process.

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Description

Test your knowledge on the sensory systems with these flashcards. Learn the definitions and functions of first order and second order neurons as they relate to the nervous system. Perfect for students studying neuroscience or biology.