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).

    2. 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.