NUR 730: Sensation and Nervous System Study Guide

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Questions and Answers

Which type of fibers stimulate most sweat glands?

Sympathetic adrenergic fibers

Somatic fibers

Parasympathetic fibers

Sympathetic cholinergic fibers (correct)

What is the primary function of the baroreceptor reflex?

Regulating blood glucose levels

Facilitating sexual functions

Responding to changes in blood pressure (correct)

Controlling gastrointestinal secretions

Which reflex is primarily associated with the erection process?

Sympathetic reflex

Gastrointestinal reflex

Denervation reflex

Parasympathetic reflex (correct)

How does the body compensate for denervation injury?

Increased intrinsic tone in smooth muscle Signup and view all the answers

What commonly triggers autonomic dysreflexia following a spinal cord injury?

Bladder or bowel distension Signup and view all the answers

What is the effect of sympathomimetics on the autonomic nervous system?

Increase sympathetic activity Signup and view all the answers

What is the primary effect of anticholinergics in autonomic pharmacology?

Block the effect of acetylcholine Signup and view all the answers

What happens when sympathetic impulses are inhibited during the baroreceptor reflex?

Blood pressure returns to normal Signup and view all the answers

What should be avoided during eye surgery when a gas bubble is placed by the surgeon?

Nitrous Oxide (N<del>2</del>O) Signup and view all the answers

What is a common consequence of traction on extraocular muscles during surgery?

Oculocardiac Reflex Signup and view all the answers

Which cranial nerve is responsible for the afferent component of the Oculocardiac Reflex?

Trigeminal Nerve (CN V) Signup and view all the answers

What can occur as a complication of a Retrobulbar Block?

Retrobulbar Block Apnea Syndrome Signup and view all the answers

What effect do anesthetic agents have on Visual Evoked Potentials (VEP)?

They lower the amplitude and latency of the signal Signup and view all the answers

What is the incidence rate of corneal abrasions during non-ocular surgeries?

0.013% to 0.17% Signup and view all the answers

Which component of Cranial Nerve VIII is responsible for balance sensation?

Vestibular system Signup and view all the answers

What types of signals do hair cells in the cochlea send?

Auditory signals via the cochlear branch Signup and view all the answers

What is the direct connection formed by the vestibulospinal tract responsible for?

Balance control Signup and view all the answers

What is the primary treatment approach for Retrobulbar Block Apnea Syndrome?

Supportive management Signup and view all the answers

Which part of the nervous system is primarily responsible for regulating short-term responses and homeostasis?

Central Nervous System Signup and view all the answers

What is the main function of nociceptors?

Detect pain Signup and view all the answers

Which type of tactile receptor is known for adapting very quickly to stimuli?

Pacinian Corpuscles Signup and view all the answers

How does receptor adaptation occur?

Initial response is high but diminishes with continued stimulation. Signup and view all the answers

What is the purpose of 'spatial summation' in nerve transmission?

To recruit more nerve fibers as strength increases. Signup and view all the answers

Which type of fibers is responsible for dull pain and temperature sensations?

Type C fibers Signup and view all the answers

Which structure is part of the Anterolateral System of sensory pathways?

Thalamus Signup and view all the answers

Which of the following describes convergence in neuronal pools?

Signals from multiple sources excite a single neuron. Signup and view all the answers

Which brain region is primarily involved in the initiation of voluntary movement?

Precentral gyrus Signup and view all the answers

What is the role of myelination in nerve fibers?

It insulates fibers to increase conduction velocity. Signup and view all the answers

What is the main function of muscle spindles?

Provide sensory information about muscle length Signup and view all the answers

What type of paralysis is associated with lower motor neuron diseases?

Flaccid paralysis Signup and view all the answers

What is the difference between static position sense and kinesthesia?

Static position sense involves conscious perception; kinesthesia involves sensing rate of movement. Signup and view all the answers

What characterizes the labeled line principle in sensory modalities?

It denotes the specificity of nerve fibers to transmit one sensation. Signup and view all the answers

Which reflex causes withdrawal of a body part from a painful stimulus?

Flexor reflex Signup and view all the answers

What does 'reciprocal inhibition' in neural circuits refer to?

Simultaneous excitatory and inhibitory signals in opposing muscle groups. Signup and view all the answers

In which condition will an injury above the decussation result in paralysis?

Upper motor neuron disease Signup and view all the answers

Which type of receptor is most likely to be responsible for detecting changes in skin temperature?

Thermoreceptors Signup and view all the answers

How would you classify a movement disorder characterized by involuntary, slow, writhing movements?

Athetosis Signup and view all the answers

Which type of sensation does the term 'deep sensations' refer to?

Sensation from deep tissues. Signup and view all the answers

Which of the following best describes cogwheel rigidity?

Intermittent resistance during passive movement. Signup and view all the answers

What are Golgi tendon organs primarily responsible for sensing?

Muscle tension Signup and view all the answers

Which type of cerebral palsy is characterized by the inability to control balance and coordination?

Ataxic cerebral palsy Signup and view all the answers

What does an increased deep tendon reflex (DTR) indicate?

Upper motor neuron disease Signup and view all the answers

Which motor tract primarily carries information for skilled voluntary movements?

Lateral corticospinal tract Signup and view all the answers

What condition is characterized by involuntary jerking or swinging motions of limbs?

Chorea Signup and view all the answers

Which type of paralysis results from damage to lower motor neurons rather than upper motor neurons?

Flaccid paralysis Signup and view all the answers

What does the precentral gyrus primarily involve?

Motor functions Signup and view all the answers

What is the purpose of using intraoperative spinal cord monitoring during spinal reconstructive surgery?

To identify ischemia and adjust the procedure Signup and view all the answers

Which technique specifically monitors the dorsal columns of the spinal cord?

Somatosensory evoked potentials (SSEPs) Signup and view all the answers

What should be avoided during Motor Evoked Potentials (MEPs) monitoring?

Neuromuscular blockers like vecuronium Signup and view all the answers

What is the primary function of the bispectral index (BIS) monitor?

To assess level of consciousness Signup and view all the answers

What does the wake-up test during surgery assess?

Motor function of the legs Signup and view all the answers

What is a characteristic of C fibers?

Very small postganglionic fibers with slow conduction Signup and view all the answers

Which statement about ECoG monitoring is true?

It can identify epileptogenic foci during seizure surgery. Signup and view all the answers

Study Notes

Nervous System Overview

The Nervous System (short term) and Endocrine System (long term) work together to regulate homeostasis.
Central Nervous System (CNS): consists of the brain and spinal cord.
Peripheral Nervous System (PNS): includes somatic (voluntary control) and autonomic (involuntary control) systems.
Autonomic Nervous System has three divisions:
- Sympathetic: triggers fight or flight response.
- Parasympathetic: controls rest and digest activities.
- Enteric System: governs digestion and enzyme secretion.

Key Terms

Afferent: sensory pathways directing information toward the CNS.
Efferent: pathways conveying information away from the CNS.
Decussation: crossing of nerve fibers.
Ipsilateral: sensory or motor functions occurring on the same side of the body.
Contralateral: functions occurring on the opposite side.
Transduction: conversion of sensory stimuli into electrical signals for transmission to the CNS.
Perception: conscious awareness of a sensory modality.

Types of Sensations

Main types include:
- Mechanoreceptive: detects touch and pressure.
- Thermoreceptive: senses temperature variations.
- Pain: activated by tissue damage.
Additional sensation types:
- Exteroreceptive: sensory information from the body surface.
- Proprioceptive: sense of body position.
- Visceral: sensory input from internal organs.

Specialized Sensory Receptors

Mechanoreceptors: respond to mechanical compression/stretching.
Thermoreceptors: identify temperature changes.
Nociceptors: detect tissue damage (pain).
Electromagnetic receptors: respond to light on the retina.
Chemoreceptors: sense taste, smell, and blood gas composition.

Tactile Receptors

Free Nerve Endings: spread throughout skin, detect touch, pressure, and pain.
Meissner's Corpuscle: found in non-hairy skin areas, sensitive to light touch and low-frequency vibrations.
Merkel's Discs: localized touch receptors providing continuous signals.
Ruffini's Endings: deeper tissue receptors, slowly adapting, detect continuous deformations.
Pacinian Corpuscle: sensitive to rapid pressure changes and vibrations.

Receptor Functionality and Adaptation

Receptor adaptation varies among types; rapid adaptors (e.g., Pacinian) respond to changes, while slow adaptors (e.g., Ruffini) respond to ongoing stimulus.
Neurons respond to specific stimuli, with the Labeled Line Principle ensuring each type of sensation is transmitted via designated nerve fibers.

Neuron Activation and Transmission

Receptor potentials arise from stimuli altering electrical membrane potentials, initiating action potentials when thresholds are reached.
Action potentials are defined by thresholds, frequency, and amplitude, influencing sensory experience intensity.

Divergence and Convergence

Divergence amplifies a signal across multiple nerve fibers.
Convergence allows signals from various inputs to combine, enhancing information processing.

Two-Point Discrimination

Ability to discern between two nearby stimuli; closer at fingertips (1-2mm) than on the back (30-70mm).

Proprioception

Two subcategories:
- Static: body positioning awareness.
- Kinesthesia: movement perception.
Located in joints and muscles via specialized receptors.

Nerve Transmission

Nerve fibers classified by size, function, and myelination, influencing conduction velocities (0.5-120 m/s).
Type A fibers (myelinated) are fast; Type C fibers (unmyelinated) are slow.
Different responses to local anesthetics based on axon diameter and fiber type.

Sensory Pathways

Sensory input typically enters the spinal cord through dorsal roots.
Ascends via Dorsal Column (Medial Lemniscal System) or Anterolateral System, differentiating in spatial orientation and types of sensations conveyed.

Dorsal Column-Medial Lemniscal System

Composed of large myelinated fibers with rapid conduction velocities.
Responsible for conveying touch, vibration, and proprioception to the brain; crosses at the medulla.

Dorsal Column Pathway

Sensory fibers differentiate, ascending medially or synapsing in spinal gray matter before continuing to the brain.### Intubation and Anesthesia
Inhalation anesthetics, Propofol, Opioids, and Benzodiazepines decrease intraocular pressure (IOP).
Nitrous oxide (N2O) is contraindicated in eye surgery if a gas bubble is being placed, as it can expand in air-filled spaces.

Oculocardiac Reflex

Triggered by traction on extraocular muscles, can cause bradycardia, ventricular ectopy, or ventricular fibrillation.
Elicited by retrobulbar block through Trigeminal (CN V) and Vagus (CN X) nerves.
Management includes removing the stimulus, deepening anesthetics, and administering Atropine or Glycopyrrolate.

Retrobulbar Blocks

Retrobulbar Block Apnea Syndrome is rare; local anesthetic can spread to the optic nerve sheath, causing unconsciousness and apnea.
Treatment is primarily supportive, involving intubation/ventilation and management of cardiac arrhythmias.

Visual Evoked Potentials (VEP)

Evaluated during surgeries with risk of cranial nerve II damage, such as transsphenoidal hypophysectomy.
Sensitive to anesthetics, which can affect signal amplitude and latency, complicating assessment of neuronal pathways.

Corneal Abrasions

The most frequent ocular injuries in non-ocular surgeries, occurring at an incidence of 0.013% to 0.17%.

Hearing and Balance

Cranial Nerve VIII has two parts: the cochlear portion for hearing and the vestibular system for balance.
Cochlear structure includes hair cells that respond to sound vibrations, sending signals via the cochlear branch.
The vestibular system contributes to balance, with direct links to motor neurons ensuring postural stability.

Motor Pathways

Lateral corticospinal tract originates from the precentral gyrus, carrying motor commands down to the spinal cord.
Most fibers decussate in the lower medulla, while some remain ipsilateral.

Muscle Control and Intrinsic Feedback

Muscle spindles in skeletal muscles detect stretch and send information to the brain, while Golgi tendon organs monitor muscle tension.
Feedback from these mechanisms informs motor control and adjustments.

Reflex Responses

Flexor reflex involves withdrawal from painful stimuli, with rapid neural pathways activating necessary muscles and inhibiting opposing muscles.

Clinical Relevance of Motor System Disorders

Upper motor neuron diseases show enhanced reflexes and muscle tone with positive Babinski signs.
Lower motor neuron diseases exhibit diminished reflexes, flaccid paralysis, and muscle atrophy.
Paralysis location relates to the decussation level: injuries above lead to contralateral paralysis, while below results in ipsilateral effects.

Movement Disorders

Ataxia involves coordination loss, while hyperkinesis indicates excessive movement.
Conditions like cerebral palsy, arising from upper motor neuron damage, disrupt motor functions and are not progressive.

Autonomic Nervous System Responses

Baroreceptor reflex regulates blood pressure through sympathetic and parasympathetic activity.
Summary reflexes include gastrointestinal responses to food and sexual reflex actions.

Denervation and Autonomic Dysreflexia

After denervation injury, smooth muscle tone can compensate, improving vessel constriction.
Autonomic dysreflexia occurs after spinal cord injuries above T6, leading to unregulated sympathetic responses, risking severe hypertension and strokes.

Autonomic Pharmacology

Drugs can either stimulate or inhibit autonomic nervous system functions.
Sympathomimetics and cholinomimetics enhance sympathetic and parasympathetic activities, respectively, while antagonists counter these effects.
The action of drugs depends on their interaction with specific receptors.

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Description

Prepare for Exam 2 in NUR 730 with this study guide focused on sensation, motor functions, and the nervous system. Explore the distinctions between the central and peripheral nervous systems, including their roles in regulating homeostasis and controlling bodily functions.