Somatosensory Nervous System

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Questions and Answers

Which type of pain is transmitted via the paleospinothalamic tract?

Slow pain via C fibers (correct)

Acute thermal pain via C fibers

Mechanical pain via A-d fibers

Fast pain via A-d fibers

What is a known complication of a retrobulbar block?

Gustatory dysfunction

Retrobulbar apnea syndrome (correct)

Corneal abrasion

Intraocular pressure reduction

Which of the following agents is known to decrease intraocular pressure (IOP)?

Intubation

Inhalation anesthetics (correct)

Succinylcholine

Ketamine

Which of the following sensory modalities is primarily associated with the inner ear?

Hearing and balance Signup and view all the answers

Which type of receptor is specifically designed to detect temperature changes?

Thermoreceptor Signup and view all the answers

What principle explains how certain nerve fibers transmit only one modality of sensation?

Labeled line principle Signup and view all the answers

Which receptor is responsible for detecting deep pressure and vibration?

Pacinian corpuscles Signup and view all the answers

What effect does continued stimulation have on receptor adaptation?

Initial response is high but diminishes over time Signup and view all the answers

What do mechanoreceptors primarily detect?

Mechanical compression or stretching Signup and view all the answers

Which type of receptor would help you sense tissue damage?

Nociceptor Signup and view all the answers

What type of nerve fibers are classified as Type C?

Unmyelinated and small, with slow conduction Signup and view all the answers

Which sensory pathway crosses over at the medulla?

Dorsal column medial leminiscal system Signup and view all the answers

In differential blockade during neuraxial anesthesia, which type of fibers are typically blocked first?

Sympathetic fibers Signup and view all the answers

What is the primary characteristic of reciprocal inhibition?

Inhibition of opposing muscle groups when agonists muscles are activated Signup and view all the answers

Which of the following accurately describes temporal summation?

Increased signal from higher frequency nerve impulses in one nerve fiber Signup and view all the answers

Which type of sensory fibers are primarily involved with muscle spindles and Golgi tendon organs?

Type 1 fibers (Type A) Signup and view all the answers

Which statement about the anterolateral system is true?

Sensations cross at the anterior commissure before they ascend to the brain Signup and view all the answers

What does spatial summation refer to in the context of nerve signal transmission?

Increasing single strength is transmitted by using progressively greater numbers of nerve fibers Signup and view all the answers

What is transduction in the context of the nervous system?

Converting a sensory stimulus into an electrical signal that is transmitted to the CNS Signup and view all the answers

Which mechanoreceptor subtypes sense superficial tactile sensation?

All of the above Signup and view all the answers

Which mechanoreceptor subtypes sense deep tissue sensation?

All of the above Signup and view all the answers

Which mechanoreceptor subtype is involved in both superficial and deep sensation? (select 2)

Free nerve endings Signup and view all the answers

What sensations are associated with free nerve endings? (Select all that apply)

Pain Signup and view all the answers

What sensation is associated with electromagnetic receptors?

Vision Signup and view all the answers

What is receptor potential?

A change in membrane potential in response to a stimulus Signup and view all the answers

What mechanisms cause receptor potentials? (Select all that apply)

Mechanical deformation to open channels Signup and view all the answers

What is differential sensitivity in the context of sensory receptors?

Receptors are designed for specific stimuli and are unresponsive to other types of stimuli. Signup and view all the answers

The greater the receptor potential rises above threshold, the ____ the action potential frequency.

greater Signup and view all the answers

What occurs when a sensory receptor experiences intense stimulation?

Progressively less additional action potentials are propagated, allowing for a range of sensory experiences. Signup and view all the answers

What occurs to the action potential amplitude of sensory receptors under increased stimulation?

It initially rapidly increases but progresses less rapidly at high stimulus strength. Signup and view all the answers

How are receptors responsive to both weak and intense stimuli?

With progressively stronger stimulus strength, amplitude is diminished but the frequency of repetitive action potentials increase Signup and view all the answers

What is adaptation in the context of sensory receptors?

The reduction in the frequency of action potentials from a receptor when a constant stimulus is applied. Signup and view all the answers

Rapid receptors are associated with sensing ____ changes.

acute Signup and view all the answers

Slow adapting receptors sense ____ conditions in the body.

Constant Signup and view all the answers

Which of the following receptors are classified as slow adapting receptors? (select all that apply)

Baroreceptors Signup and view all the answers

What type of nerve fibers are postganglionic autonomic fibers?

Type C fibers Signup and view all the answers

What type of fibers are unmyelinated fibers that carry slow pain, itch, temperature, and crude touch sensations?

C fibers Signup and view all the answers

Somatic motor sensation and proprioception are transmitted by which type of nerve fiber?

A-alpha fibers Signup and view all the answers

A-alpha nerve fibers involved in proprioception are _ and __.

1a muscle spindle, 1b golgi tendon organ Signup and view all the answers

A-b and A-y fibers are associated with which numerical classification?

Class II Signup and view all the answers

Which ascending pathway utilizes A-beta fibers to transmit fine touch and pressure?

Dorsal column-medial lemniscal pathway Signup and view all the answers

What is the Erlanger-Gasser classification of type 3 fibers that transmit pain, cold, and touch information?

A-delta fibers Signup and view all the answers

Which ascending pathway transmits pain, cold, and crude touch sensations via A-d fibers?

Anterolateral Spinothalamic tract Signup and view all the answers

What is a neuronal pool?

A group of neurons that share common inputs, outputs, and functions Signup and view all the answers

What is a stimulatory field?

The neuronal area stimulated by each incoming nerve fiber Signup and view all the answers

What are facilitated neurons in a neuronal pool?

Subthreshold neurons that can reach threshold with further stimulus Signup and view all the answers

What is amplifying divergence in the nervous system?

Input signal spreads to an increasing number of neurons Signup and view all the answers

What is a benefit of divergence in multiple tracts?

Signal is transmitted to separate areas. Signup and view all the answers

What is the purpose of convergence in the nervous system?

To allow summation of information for the CNS to process different types of information Signup and view all the answers

What is an afterdischarge?

A prolonged output discharge that occurs after initial stimulus Signup and view all the answers

What occurs during synaptic afterdischarge?

A single input signal can cause a sustained output via a series of repetitive charges Signup and view all the answers

Where are reverberatory (oscillatory) circuits found in the human body?

In the respiratory drive Signup and view all the answers

Which nerve fiber transmits signals from free nerve ending tactile receptors? select 2

A-delta fibers Signup and view all the answers

What sensations are transmitted via the dorsal column medial lemniscal system? (Select all that apply)

Fine touch Signup and view all the answers

Which sensations are transmitted via the anterolateral system? (Select all that apply)

Pain Signup and view all the answers

Match the neuron with its location in the anterolateral pathway:

First order neuron = Dorsal root ganglia Second order neuron = Substantia gelatinosa Third order neuron = Ventral posterolateral nucleus of thalamus Signup and view all the answers

Match the neuron with its location in the dorsal column medial lemniscal pathway:

First order neuron = Dorsal root ganglia Second order neuron = Medulla Third order neuron = Ventral posterior lateral nucleus of thalamus Signup and view all the answers

What is the function of the fasciculus gracilis?

Medial tract of the DCML that transmits information from the lower body (below T6) Signup and view all the answers

What is the function of the fasciculus cuneatus?

:Lateral tract of the DCML that transmits information from the upper body (C2-T6) Signup and view all the answers

Which ascending pathway is noted for its rapid transmission speed?

Dorsal Column-Medial Lemniscal Pathway (DCML) Signup and view all the answers

Which somatosensory area plays the greatest role in sensation?

Somatosensory Area 1 Signup and view all the answers

Where is somatosensory area 1 located?

In the parietal lobe behind the central fissure in the postcentral gyrus Signup and view all the answers

What is the purpose of the homunculus in the nervous system?

It describes the distribution of motor and sensory functions across the cortex via 3rd order neuron transmission Signup and view all the answers

What are the two types of position sense?

Static position and kinesthesia Signup and view all the answers

Where do pain signals primarily terminate in the nervous system? (Select all that apply)

Reticular nuclei of the brainstem Signup and view all the answers

What lamina is the substantia gelatinosa associated with in the spinal cord?

Lamina II-III Signup and view all the answers

Match the dermatome with its associated landmarks:

Clavicle = C4 Nipple = T4 Xiphoid = T6 Umbilicus = T10 Tibia = L4 to L5 Perineum = S1 to S5 Signup and view all the answers

In herpes zoster, the pain and paresthesia are localized to what location?

Dermatome area Signup and view all the answers

What type of nerve fibers transmit fast pain via the neospinothalamic tract?

Aδ fibers Signup and view all the answers

What is unique about the adaptation of pain receptors?

They do not adapt at all. Signup and view all the answers

What is hyperalgesia?

An increased sensitivity to pain Signup and view all the answers

What is the primary neurotransmitter used in the neospinothalamic tract?

Glutamate Signup and view all the answers

What are the primary neurotransmitters used in the paleospinothalamic tract? (select 2)

Glutamate Signup and view all the answers

What is the mechanism behind referred pain?

Visceral pain fibers synapse in the spinal cord on second-order neurons receiving signals from the skin. Signup and view all the answers

Where do first order neurons in the neospinothalamic tract terminate?

Marginal layer (lamina 1) Signup and view all the answers

Where do first order neurons in the paleospinothalamic tract terminate?

Substantia gelatinosa Signup and view all the answers

Match each nerve fiber with the appropriate function

A-a = skeletal muscle, proprioception A-b = fine touch, pressure A-y = skeletal muscle tone A-d = fast pain, touch, temperature Signup and view all the answers

What nerve fiber types are preganglionic autonomic fibers?

Type B fibers Signup and view all the answers

Match the mechanoreceptor with its function

Meissner's corpuscle = 2-point discrimination, vibration Merkel's disc = continuous touch Ruffini's ending = proprioception, prolonged touch Pacinian corpuscle = vibration Signup and view all the answers

A patient screams in pain when you lightly touch her shoulder. What is this an example of?

Allodynia Signup and view all the answers

What is the normal intraocular pressure (IOP) range, and what is a commonly accepted elevated IOP threshold in glaucoma?

Normal IOP: 12-20 mmHg; Elevated IOP 60-70 mmHg Signup and view all the answers

Which of the following statements best describes the effect of anesthetic agents on visual evoked potentials (VEP)?

Anesthetic agents lower the amplitude and latency of the signal, making it difficult for the neurophysiologist to accurately assess pathway integrity. Signup and view all the answers

Which evoked potential is barely sensitive to anesthetics?

Brainstem auditory evoked potentials Signup and view all the answers

Study Notes

Peripheral Nervous System

Divided into Somatic Nervous System and Autonomic Nervous System.
Decussation refers to the crossing of nerve fibers.
Transduction is the process of converting sensory stimuli into electrical signals for the CNS.
Transmission involves conducting sensory impulses from the PNS to the CNS.

Types of Receptors

Mechanoreceptors respond to mechanical compression or stretching.
- Include free nerve endings, Meissner's corpuscles, tactile receptors, Ruffini's endings, and Pacinian corpuscles.
Thermoreceptors detect temperature changes.
Nociceptors identify tissue damage.
Electromagnetic receptors respond to light.
Chemoreceptors react to chemical changes.
Exteroceptors receive signals from body surfaces.
Proprioceptors provide information about body position.
Visceral receptors are associated with internal organs.
Deep receptors transmit information from deep tissues.

Sensory Processing

Sensation activation involves receptor stimulation and impulse transmission to the CNS.
Differential sensitivity leads to specific receptors for each sensation.
The labeled line principle states that certain nerve fibers transmit specific sensations only.

Electrical Signals

Stimuli change the electrical membrane potential in receptors.
Action potentials follow an all-or-nothing principle.
Higher receptor potentials yield higher frequency of action potentials.
Intense stimulation can lead to diminishing additional action potentials.
The amplitude of action potentials increases with stimulus strength but less so at high intensities.

Pacinian Corpuscle

Structurally comprises a central nerve fiber surrounded by concentric layers.
Capable of sensing both light and deep pressure due to its mechanoreceptor properties.

Receptor Adaptation

Initial responses are strong but diminish with continued stimulation.
Receptors adapt at varying rates: rapid (e.g., Pacinian, hair receptors) and slow (e.g., baroreceptors, chemoreceptors).

Nerve Fiber Classification

Categorized by size, function, and myelination:
- Nerve diameter ranges from 0.5 to 20 micrometers.
- Nerve conduction velocity ranges from 0.5 to 120 m/s.
General classifications:
- Type A: myelinated, large, fast conduction.
- Type B: myelinated, small, in pre-ganglionic ANS.
- Type C: unmyelinated, small, slow conduction.
Sensory nerve classification:
- Types 1-3: myelinated fibers.
- Type 4: unmyelinated fibers.
- Type 1 fibers are large, myelinated, and fast (e.g., from muscle spindles).

Blockades and Summation

Differential blockade occurs in the order: sympathetic fibers first, sensory next, and motor last.
Spatial summation involves increasing signal strength through more fibers.
Temporal summation involves increased frequency of impulses in existing fibers.

Neuronal Pools and Connections

Divergence and convergence in neuronal connections allow signal modulation.
Reciprocal inhibition provides excitatory signals in one direction and inhibitory in the opposite, controlling muscle pairs.

Sensory Pathways

Most sensory inputs enter the spinal cord via dorsal roots.
Dorsal column medial lemniscal system: ascends and crosses at the medulla, for precise localization.
Anterolateral system: crosses then ascends, handling crude touch, pain, and temperature.
Anterior spinothalamic tract: crude touch sensation.
Lateral spinothalamic tract: conveys pain and temperature.

Dermatomes and Pain

Dermatomes:
- C4 = clavicles.
- T4 = nipples.
- T6 = xiphoid process.
- T10 = umbilicus.
- L4-L5 = tibia.
- S2-S5 = perineum.
Acute pain serves a protective function.
Fast pain transmitted via neospinothalamic tract with A-d fibers.
Slow pain transmitted via paleospinothalamic tract with C fibers.

Pain Pathways

Neospinothalamic tract: uses glutamate as an excitatory neurotransmitter; fast A-d fibers transmit mechanical and acute thermal pain.
Paleospinothalamic tract: employs glutamate and substance P; responsible for slow C fiber pain signaling.

Eye Anatomy and Visual Function

Components include the sclera, retina, cornea, iris, and lens.
Glaucoma is characterized by increased intraocular pressure.
Retrobulbar block can lead to complications like retrobulbar apnea syndrome.

Anesthetics and Eye Surgery

Agents increasing IOP: succinylcholine, ketamine, intubation.
Agents decreasing IOP: inhalation anesthetics, propofol, opioids, benzodiazepines.
Nitrous oxide (N2O) is contraindicated in eye surgeries.

Reflex and Sensory Responses

Oculocardiac reflex involves symptoms management during strabismus repair in pediatrics.
Visual evoked potentials assess visual pathways.
Corneal abrasions can occur, impacting vision and comfort.

Auditory and Balance Functions

Hearing is facilitated by the external and middle ears; balance involves the inner ear.
Gustation relies on taste buds, identifying five primary taste sensations.
Smell involves olfactory receptors in enhancing sensory experiences.

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Description

Test your knowledge on the peripheral nervous system, including its division into the somatic and autonomic nervous systems. This quiz also covers concepts like decussation, transduction, and transmission, along with the types of sensory receptors involved. Prepare to challenge your understanding of the complex workings of our nervous system!