17.Neuro_PT2_study_guide

Page 1: Normal Physiology of the Nervous System

Spinal Cord Functions

• Conveys Nerve Impulses

  • Connects brain to spinal nerves.

  • Upper Motor Neurons (UMN):

    • Originate in motor strip of cerebral cortex or brainstem.

    • Synapse with Lower Motor Neurons in spinal cord.

  • Lower Motor Neurons (LMN):

    • Cell bodies located in the spinal cord with axons extending into PNS.

    • Synapse with muscle fibers at the neuromuscular junction to stimulate contraction.

• Mediates Spinal Reflexes:

  • Important for maintaining posture, muscle tone, and protective responses to pain.

Reflex Arcs

• Neural Circuits in spinal cord that trigger specific motor responses without CNS input:

  • Involves the path:

    • Receptor senses stimuli → sensory neuron synapses with CNS interneurons → communicates with LMNs → activates effector organ response.

  • Sensory neurons also send pain information to higher CNS centers, where the reflex occurs before perception at higher brain levels.

Structure of the Spinal Cord

• Longitudinal Organization:

  • Organized into ascending/sensory tracts and descending/motor tracts.

• Segmental Organization:

  • Corresponds with spinal nerve roots to understand body parts innervated by each segment.

Pathological Changes and Predisposing Factors

• Pathological Changes: Damage to the cord affects nerve transmission and reflex activity.

• Predisposing Factors:

  • Trauma, cancer, infection, degenerative processes, etc.

• Nursing Problems: Assess specific effects related to the damage.

Page 2: Peripheral Nervous System Overview

Functions of the Peripheral Nervous System

• Transmission of impulses to and from CNS and peripheral tissues.

1. Somatic Nervous System

• Regulates Voluntary Activities:

  • Controlled by skeletal muscles.

  • Afferent/Sensory Pathways:

    • Carry sensory impulses to CNS.

  • Efferent/Motor Pathways:

    • Carry motor impulses to effector organs.

2. Autonomic Nervous System

• Regulates Involuntary Activities:

  • Controlled by organ systems.

  • Divisions:

    • Sympathetic System (Thoracolumbar Division):

      • Maintains automatic body functions and mediates “fight or flight” responses.

    • Parasympathetic System (Craniosacral Division):

      • In charge of “rest and digest” activities.

Common Alterations in Neural Function

• Alterations in Sensory Function: Pain

  • Description: An unpleasant sensory and emotional experience.

  • Most common reason for seeking health care:

    • Pain receptors translate stimuli into action potentials sent to the spinal cord.

Types of Afferent Neurons

• Large-Diameter, Myelinated A-delta Fibers:

  • Fast conduction speed, transmit sharp, localized pain.

• Small-Diameter, Unmyelinated C Fibers:

  • Slow onset, longer duration of diffuse, aching pain.

• Involved in pain transmission pathways:

  • Reflex circuits, reticular activating system, thalamus, cortex, limbic system.

Page 3: Pain and Its Assessment

Types of Pain

1. Referred Pain:

   • Pain felt in a different site from its origin, innervated by the same spinal nerve.

2. Endogenous Opioids:

   • Pain perception can be modified through endorphins and related substances.

   • Midbrain and brainstem regulate the release of opiates, inhibiting pain mediators.

Assessment Findings related to Pain

• Description of Pain:

  • Specifics not detailed but should include intensity, duration, and qualitative aspects.

• Physiologic Responses:

  • Acute Pain: Characteristic responses.

  • Chronic Pain: Different responses.

• Psychosocial Reactions:

  • Vary depending on the type and duration of pain

  • Influenced by pain threshold (intensity perceived as painful) and pain tolerance (maximum intensity endured).

Wind-up Phenomenon

• This involves sensitization processes related to chronic pain conditions.

Page 4: Autonomic Nervous System Description

Overview

• Maintains Homeostasis:

  • Governs involuntary functions through visceral organs and blood vessels.

• Neuronal Composition:

  • Both efferent and sensory input required.

• Integration:

  • Hypothalamus and brainstem integrate sensory information for homeostasis.

Divisions of the Autonomic Nervous System

1. Sympathetic System (SNS)

   • Functions in response to body’s stress needs and routine activities.

   • Sympathetic nerves originate from spinal cord (T1-L2) and include preganglionic and postganglionic neurons.

2. Parasympathetic System (PSNS)

   • Functions to conserve energy and replenish stores; opposite of SNS.

   • Characterized by long preganglionic neurons and short postganglionic fibers.

Neurotransmitters in Autonomic Nervous System

1. Cholinergic Receptors:

   • Acetylcholine works at these receptors:

     • Secreted by preganglionic and parasympathetic postganglionic neurons.

2. Catecholamines:

   • Norepinephrine and epinephrine act at adrenergic receptors, only present in SNS.

Page 5: Cholinergic and Adrenergic Receptors

Types of Cholinergic Receptors

1. Nicotinic Receptors: Present in autonomic ganglia and muscle end plates.

2. Muscarinic Receptors: Present on target cells of parasympathetic postganglionic fibers.

Types of Adrenergic Receptors

• Beta1: Mainly in the heart.

• Beta2: Located in bronchioles and sites with beta-mediated functions.

• Alpha1: On vascular smooth muscle (postsynaptic).

• Alpha2: Located in CNS (presynaptic) to regulate norepinephrine release.

Importance of Learning this Material

• Understanding the roles and interactions helps in managing conditions and clinical assessments related to neurological functions.

Page 6: Normal Physiology and Pathological Changes

Overview of the Spinal Cord

• Functions & Structure: Similar to previous pages with detailed references to UMNs and LMNs and mediating reflex arcs.

• Focuses on relay and organizational structures for sensory and motor pathways.

Pathological Changes

• Spinal Cord Damage:

  • Alters communication and reflex activity.

• Predisposing Factors: Examples include trauma, like fractures or penetrating injuries.

• Nursing Problems and Assessment Findings:

  • Example: Spinal cord injury effects vary by location (C4 and above vs lumbar injuries), assessing motor functions and complications like autonomic dysfunction.

  • Examples of Expected Findings:

    • Variability in head, shoulder, and lower extremity control based on injury levels.

    • Autonomic issues lead to conditions like postural hypotension and dysreflexia.