16.Neuro_PT1_study_guide

Alterations in Neural Function

Overview of the Nervous System

  • Functions:

    • Works alongside the endocrine system to direct and integrate all body systems.

    • Information Processing:

      • Receives data from internal and external environments via sensory pathways.

      • Processes this information to determine responses.

      • Transmits information back to effectors (muscles, glands) via motor pathways.

Divisions of the Nervous System

  • Central Nervous System (CNS):

    • Processes information; key for emotions, memory, cognition, and learning.

      1. Brain

      2. Spinal Cord

  • Peripheral Nervous System (PNS):

    • Transmits impulses to and from CNS and peripheral tissues.

      1. Somatic Nervous System:

      • Regulates voluntary activities through skeletal muscles.

      • Pathways:

        • Afferent/Sensory pathways (carry impulses to CNS).

        • Efferent/Motor pathways (carry motor impulses to effectors).

      1. Autonomic Nervous System:

      • Regulates involuntary activities through organ systems.

      • Divisions:

        • Sympathetic System (Thoracolumbar Division):

          • Maintains homeostasis and mediates 'fight or flight' reactions.

        • Parasympathetic System (Craniosacral Division):

          • Manages 'rest and digest' activities.

Normal Physiology of the Nervous System

Communication in Neurons

  • Method of Communication:

    • Through action potentials at synapses.

    • Types of Synapses:

      • Electrical Synapses:

        • Ions pass through gap junctions for direct transmission.

      • Chemical Synapses:

        • Action potential triggers neurotransmitter release from presynaptic membranes.

        • Neurotransmitters diffuse across synaptic cleft to postsynaptic receptors.

Types of Neurotransmitters

  • Examples:

    • Amino Acids: Glutamate, GABA.

    • Peptides: Endorphins, enkephalins, substance P.

    • Monoamines: Serotonin, dopamine, norepinephrine, epinephrine.

    • Action:

      • Effects depend on the receptor type (can be excitatory or inhibitory).

Pathological Changes Affecting Synapses

  • Electrical Synapses:

    • Disruption can occur due to electrolyte or pH imbalances, alteration of the sodium-potassium pump.

  • Chemical Synapses:

    • Problems may arise from neurotransmitter production or release issues, changes in receptor site numbers or sensitivity.

Supporting Cells of the Nervous System

  • Types of Supporting Cells:

    • In CNS: Glial cells (oligodendroglia, astroglia, microglia, ependymal cells).

    • In PNS: Schwann cells, satellite cells.

  • Functions:

    • Protection:

      • CNS: Contributes to blood-brain barrier (protects from harmful substances).

      • PNS: Forms sheaths around nerve cells, preventing diffusion of large molecules.

    • Metabolic Support:

      • Supplies glucose and metabolic support to neurons (no glycogen stores in neurons).

    • Myelination:

      • Forms myelin sheaths (Schwann cells in PNS, oligodendroglial in CNS) to enhance propagation speed of nerve signals (saltatory conduction).

Pathological Changes in Supporting Cells

  • Blood-Brain Barrier Defect: Increased permeability due to trauma or infection.

  • Demyelination: Results in reduced signal conduction efficiency.

Brain Structure and Functions

  • Cerebrum Functions:

    • Cerebral Cortex:

      • Frontal: Motor control, Broca's area (language).

      • Temporal: Auditory processing, parts of Wernicke’s area.

      • Occipital: Visual processing cortex.

      • Parietal: Somatosensory cortex for sensory information.

    • Basal Ganglia: Coordinates gracefulness, posture, and muscle tone.

  • Diencephalon:

    • Thalamus: Integrates signals between cortex and brainstem, aids in wakefulness (RAS).

    • Hypothalamus: Hormonal secretion, regulates pituitary and autonomic nervous system; manages sleep, appetite, thirst, temperature.

  • Cerebellum: Coordinates movement and balance.

  • Brainstem:

    • Comprises midbrain, pons, medulla; regulates autonomic functions, respiratory centers, cardiac and swallowing responses.

Brain Protection

  • Structural Protections:

    • Cranium: Protects brain physically.

    • Meninges: Three membranes covering the brain:

      • Pia mater (covers surface, contains blood vessels).

      • Arachnoid mater (spider-web-like, contains CSF).

      • Dura mater (tough outer layer with additional folds for protection).

    • Cerebrospinal Fluid (CSF): Circulates around the brain and spinal cord, cushioning, nourishing, and maintaining a stable environment.

Pathological Changes in Brain Function

  • Conditions:

    • Hypoxia/ischemia, increased intracranial pressure (ICP) due to trauma, tumors, or vascular changes.

    • Monro-Kellie Hypothesis: ICP compensation through volume shifts of the components.

Cerebral Circulation

  • Blood Supply:

    • Internal carotid arteries (front), vertebral arteries (back) supply blood.

    • Blood vessels anastomose to form the Circle of Willis, ensuring circulation continuity.

  • Pathological Changes:

    • Cerebrovascular disease affecting cerebral blood flow, risk factors for strokes include age, race, and health conditions.

    • Stroke Types:

      • Ischemic: Related to thrombosis or embolism.

      • Hemorrhagic: Due to blood vessel rupture.

Nursing Problems and Interventions

  • Examples of Disorders:

    • Stroke, seizures, neurological deficits.

    • Assessments for cerebrovascular issues (both ischemic and hemorrhagic strokes) include patient history and physical examination.