Neuro

• Central Nervous System (CNS)


  Brain and spinal cord
• Peripheral Nervous System (PNS)

  Cranial nerves (originates from brain) & spinal nerves (originates from spinal cord)
• Nerve cells in CNS and PNS

  • Afferent neuron = sensory pathways; transmits TO the CNS
  • Efferent neuron = motor pathways; transmits FROM the CNS
• Neurons


  The functional cells of the nervous system (comprised of cell body, cytoplasm, dendrites, & axon)
• Myelin


  • Insulates nerve cells and ↑'s speed of impulse transmission
  • Myelin is necessary for neuronal survival
• Brain requires 15-20% of cardiac output
• Interruption of O2 to the brain results in almost immediate clinical manifestations and cell death within 4-6 minutes
• Glucose


  • Provides fuel for nerve cells
  • Neurons cannot store glycogen
  • Nerve cells can take up glucose without insulin
• Neurons communicate with each other

  Via synapses; the most common type of synapse is the chemical synapse (pre and postsynaptic membrane structures) – this is a one way communication method
• Presynaptic terminal


  Secretes neurotransmitters that bind to receptors at the postsynaptic gap
• Chemical messengers in the nervous system

  • Neurotransmitters
  • Acetylcholine
  • Norepinephrine
  • Serotonin
  • Dopamine
  • GABA
• Neurotransmitters


  • Can either be "inhibitory" or "excitatory" depending upon the type of receptor that the neurotransmitter binds to
  • Are broken down by one of three potential processes (for example, acetylcholinesterase is an enzyme that breaks down acetylcholine)
• Somatosensory system


  Provides the CNS with information about body sensations
• Sensory modalities


  • Body Position (Proprioception)
  • Pain
  • Temperature
  • Touch
• Sensory Unit


  Receptors distributed throughout the body relay information to the somatosensory system
• Sensory modalities


  • Stimulus Discrimination
  • Tactile Sensation
  • Thermal Sensation
  • Position Sensation [Proprioception]
• Sensory information


  • Travels via dorsal root ganglion neurons
  • The speed of impulse conduction varies depending upon the diameter of the nerve fiber
• Nerve fiber types


  • Type A Fibers (Myelinated, fastest speed of conduction)
  • Type B Fibers (Myelinated)
  • Type C Fibers (Unmyelinated, slowest rate of conduction)
• Dermatomal Pattern of Dorsal Root Innervation


  • Organizational pattern of 32-33 (depending upon resource) paired spinal nerves from coccyx to cervical region
  • Sensory and Motor Innervation
  • Dermatome: region of the body that is supplied by a single pair of dorsal root ganglia
  • Dermatome maps assist in assessing sensory deficits that may occur from neurologic damage such as a spinal cord injury
• Neural Pathways


  • Discriminative Pathway (Rapid transmission of sensory information such as discriminate touch)
  • Anterolateral Pathway (Provides transmission of sensory information such as pain, pressure, crude touch)
• Pain


  • #1 reason people seek medical care
  • "unpleasant sensory and emotional experience associated with actual and potential tissue damage" (International Association for the Study of Pain)
  • Pain distress is influenced by anxiety, culture, gender, age past experience, and expectations about pain relief
• Pain Theories


  • Specificity Theory (1895)
  • Pattern Theory (1929)
  • Gate Control Theory (1965 by Melzack and Wall)
• Gate Control Theory


  • Proposes a "gate" mechanism whereby pain signals travel through the spinal cord to the brain where they are processed and the individuals perceives the feeling of pain
  • If the gate is OPEN – pain signals pass through, get to the brain, and the individual feels pain
  • If the gate is CLOSED – pain signals are prevented from traveling to the brain, the individual does not feel the sensation of pain
  • Large diameter fibers (Type A fibers) get to the brain very quickly and if stimulated can limit pain transmission to the brain and decrease the perception of pain
• Pain Mechanisms and Pathways

  • Nociception = pain receptors
  • Withdrawal Reflex
• Pain Threshold and Tolerance

  • Threshold: point at which an individual "perceives" pain
  • Tolerance: "pain experience"; maximal amount of pain that an individual is willing to tolerate
• Types of Pain


  • Acute (Short timeframe, caused by tissue injury/damage, ANS response)
  • Chronic (May be continuous or intermittent, > 6 months, no ANS response, psychological/psychosocial response)
  • Cutaneous (Arises from superficial structures, sharp/burning)
  • Visceral (Originates from visceral organs, result of disease process)
  • Diffuse
  • Referred (Pain is apparent at a different location than the originating site)
  • Phantom (Perception of pain in a body part that is no longer present)
  • Neuropathic (Neurogenic, originating from the neurologic system)
• Pain Assessment


  • "OPQRST" (Onset, Provokes, Quality, Radiates, Severity, Time)
  • Pain is a personal, subjective experience that instruments have been developed to quantify pain based on the person's experience (ex. Visual analog scales, numeric pain intensity)
• Headache Causes


  • Foods
  • Medications
  • Nutritional habits
  • Alcohol
  • Menstrual cycles (hormonal related)
  • Emotional stress
  • Environmental stimuli
• Primary Headaches


  • Migraine (Familial tendency, more common in females, pathophysiology, subtypes, manifestations)
  • Cluster Headache (Uncommon, hereditary factor, affects men more than women, pathophysiology, manifestations)
  • Tension-Type Headache (Most common, associated with muscle tension, dull, aching pain, does not interfere with activities associated with daily life)
• Sudden onset of a severe, unrelieved headache may be a sign of a serious problem such as a tumor, infection aneurysm
• Common clinical complaint, headaches have numerous causes and are oftentimes difficult to diagnose, headaches may be a primary problem or secondary to disease states resulting in a headache as a symptom
• Motor Functions: The ability to execute coordinated skeletal muscle movement
• Migraine without Aura


  Visual disturbances (flickering lights, spots, loss of vision)
• Migraine without Aura Manifestations

  • Lasts 1-2 days
  • Unilateral or bilateral
  • Worsens with activity
  • N/V
  • Photosensitivity
  • Sensitivity to sound
  • Visual disturbances
• Cluster Headache


  • Uncommon
  • Hereditary factor
  • Affects men more than women
  • Pain happens in clusters over a period of time
• Cluster Headache Pathophysiology


  Unclear but thought to involve the hypothalamus, cerebral vasculature, ANS, & trigeminal nerve
• Cluster Headache Manifestations


  • Rapid onset; severe, unilateral pain
  • Lasts 15 minutes to 3 hours
  • Pain behind the eye
  • May have nasal congestion, runny nose, ptosis, eyelid edema
• Tension-Type Headache


  • Most common
  • Associated with muscle tension
  • Dull, aching pain
  • Does not interfere with activities associated with daily life
• Motor Functions


  The ability to execute coordinated skeletal muscle movement
• Levels of Hierarchy


  • Motor Cortex
  • Brain Stem
  • Spinal Cord