Neuro part 1

Nervous System Overview

• Function:

  • Receives sensory information from the body

  • Processes this information to determine appropriate responses

  • Transmits information back to effector organs (muscles, glands, etc.) via motor pathways

Divisions of the Nervous System

Central Nervous System (CNS)

• Components:

  • Brain: Main processing unit for emotions, memory, learning

  • Spinal Cord: Relays information to/from the body

Peripheral Nervous System (PNS)

• Function:

  • Transmits impulses to/from CNS/peripheral tissues

  • Divided into two main pathways:

    • Somatic Nervous System:

      • Regulates voluntary activities (skeletal muscles)

      • Afferent: Carries sensory impulses to CNS

      • Efferent: Carries motor impulses to effector organs

    • Autonomic Nervous System:

      • Regulates involuntary activities (organ systems)

      • Sympathetic: Activates "fight or flight" response

      • Parasympathetic: Activates "rest and digest" response

Neurons and Synapses

Neurons

• Communication Method:

  • Action potentials at synapses enable communication

• Types of Synapses:

  • Electrical Synapses:

    • Current-carrying ions pass through gap junctions quickly

  • Chemical Synapses:

    • Action potentials trigger the secretion of neurotransmitters from presynaptic terminals which diffuse across the synaptic cleft to bind to postsynaptic receptors

Neurotransmitters

• Functions:

  • Determine action based on receptor type binding (excitatory/inhibitory)

Supporting Cells in Nervous System

Glial Cells (CNS) and Schwann Cells (PNS)

• Functions:

  • Provide protection (blood-brain barrier)

    • Protects brain from harmful substances

  • Offer metabolic support for neurons (store glycogen)

  • Form myelin sheath to increase nerve conduction speed

Brain Anatomy

Cerebrum

• Cerebral Cortex Functions:

  • Frontal Lobe: Motor control, Broca's area (speech production), complex thought

    • Expressive Aphasia: inability to produce speech

  • Temporal Lobe: Auditory processing, Wernicke's area (language comprehension)

    • Receptive Aphasia: inability to understand language

  • Occipital Lobe: Visual processing

  • Parietal Lobe: Somatosensory processing

Diencephalon

• Thalamus: Integrates signals between cortex and brainstem

  • Affects higher brain functions

• Hypothalamus: Regulates hormones, sleep, hunger, body temperature

Cerebellum

• Maintains smooth movement, posture, balance

Brainstem

• Controls autonomic functions, includes midbrain, pons, and medulla

  • Medulla: Major sensory and motor tracts crossover

Protection of the Brain

Membranes and Fluid

• Meninges:

  • Dura Mater: Tough protective layer

  • Arachnoid Mater: Web-like structure with cerebrospinal fluid (CSF)

  • Pia Mater: Thin covering on the brain surface

• Cerebrospinal Fluid:

  • Produced in ventricles, provides cushioning, nourishment, and waste removal

Intracranial Pressure (ICP)

• Causes: Hypoxia, focal/global damage

• Monro-Kellie Doctrine:

  • Relationship between brain tissue, CSF, and blood volume

• Brain Herniation: Complications from increased ICP leading to compression of brain tissue

Stroke

Types of Stroke

• Ischemic Stroke: Decreased blood flow due to clotting

• Hemorrhagic Stroke: Bleeding in the brain

• Transient Ischemic Attack (TIA): Temporary decrease in blood flow, can be a warning sign

• Symptoms of CVA: May include paralysis, sensory deficits, and impaired judgment

Seizures

Types of Seizures

• Provoked Seizures: Due to identifiable causes

• Unprovoked Seizures (Epileptic): No identifiable cause

  • Can be chronic and recurring

• Types of Generalized Seizures:

  • Petit Mal: Short, non-convulsive

  • Grand Mal (Tonic-Clonic): Loss of consciousness, muscular contractions

Brain Function: Right vs Left Hemisphere Damage

Right Hemisphere Damage

• Symptoms:

  • Hemiplegia (left side paralysis)

  • Spatial-perceptual deficits, impulsive behavior, and neglect of left side

Left Hemisphere Damage

• Symptoms:

  • Hemiplegia (right side paralysis)

  • Speech/language impairment, slow cautious behavior, aware of deficits

Key Concepts

• Increased ICP: Can cause ischemia and brain herniation

• Brain Ischemia: Results from high ICP, disruptive blood flow

• AVM (Arteriovenous Malformation): Can lead to hemorrhagic stroke due to high-pressure blood flow into thin walls