Exam 4 Bio

• Spinal cord


  Anatomy, spinal nerves, somatic reflexes
• Spinal cord anatomy


  1. Protective structures

  2. External anatomy

  3. Internal anatomy
• Protective structures


  • Vertebral column
  • Meninges
• Meninges


  Dura mater, arachnoid, pia mater
• Spinal cord enlargements


  • Cervical
  • Lumbar
• Conus medullaris


  End of the spinal cord (near L1 and L2 vertebra)
• Cauda equina


  Branching of the spinal nerves
• Filum terminale


  Extension of the pia mater after the last spinal nerve
• Plexuses


  • Cervical
  • Brachial
  • Lumbar
  • Sacral
  • Coccygeal
• Internal anatomy of the spinal cord

  • Anterior median fissure
  • Posterior median sulcus
  • Gray and white commissures
  • Central canal
  • Anterior, posterior & lateral gray horns
  • Anterior, posterior & lateral white columns
• Posterior (dorsal root) ganglion


  Cell bodies of sensory neurons
• Ganglion


  Group of cell bodies in PNS
• Spinal nerve


  Ventral and dorsal roots meet
• White matter


  • Posterior white column
  • Lateral white column
  • Anterior white column
• Sensory and motor tracts

  • Fine limb control
  • Head position / balance / posture
  • Limb trunk / position, deep touch
  • Vibration, visceral pain
• Spinal nerves


  • Cervical (C1-C8)
  • Thoracic (T1-T12)
  • Lumbar (L1-L5)
  • Sacral (S1-S5)
  • Coccygeal (Co1)
• Connective tissue coverings of spinal nerves

  Epineurium, perineurium and endoneurium
• Rami of spinal nerves

  • Posterior (dorsal) ramus
  • Anterior (ventral) ramus
  • Meningeal ramus
  • Ramus communicans
• Plexuses


  A network of axons
• Dermatome


  A specific area of the skin that receives sensory input from a pair of spinal nerves
• Dermatome map


  A diagram of the cutaneous regions innervated by each spinal nerve
• Dermatomes overlap their edges as much as 50%
• Necessary to sever or anesthetize three successive spinal nerves to produce a total loss of sensation in one dermatome
• Reflex


  An automatic, sudden, involuntary response to a stimulus
• Types of reflexes


  • Somatic reflex
  • Autonomic reflex
• Where integration takes place

  • Spinal reflex
  • Cranial reflex
• Reflex arc


  The pathway followed by nerve impulses that produce a reflex
• Parts of a reflex arc

  • Sensory receptor
  • Sensory neuron
  • Integrating center
  • Motor neuron
  • Effector
• Stretch reflex


  1. Causes contraction of a skeletal muscle in response to stretching of the muscle

  2. Monosynaptic reflex (two neurons make one synapse)

  3. Patellar or knee-jerk reflex
• Muscle spindle


  Stretch receptors embedded in skeletal muscles
• Proprioceptors


  Specialized sense organs to monitor position and movement of body parts
• Golgi tendon organ


  Nerve fibers entwined in collagen fibers of the tendon
• Tendon reflex


  1. Polysynaptic reflex

  2. Ipsilateral

  3. Control muscle tension by causing muscle relaxation when muscle tension is great

  4. Sensory receptors - Golgi tendon organs
• Flexor (Withdrawal) Reflex


  1. Polysynaptic reflex

  2. Ipsilateral

  3. Intersegmental - uses more than one segment of the spinal cord

  4. Stepping on a tack (stimulus) -> Pain receptor = sensory nerve impulse -> activation of the interneuron -> activation of the motor neuron ->muscle contraction ->withdrawal of the leg
• Crossed Extension Reflex


  1. Polysynaptic reflex

  2. Contralateral reflex

  3. Intersegmental

  4. Reciprocal innervation: Contraction of muscles that extend joints in the opposite limb in response to a painful stimulus
• Vocabulary to remember


  • White matter
  • Gray matter
  • Ganglion
  • Nucleus
  • Nerve
  • Nerve tract
• Chapter 16: Sense Organs

  • Sensation
  • Sensory receptors
  • Somatic sensations
  • Sensory pathways
  • Special senses
  • Olfaction
  • ii) Gustation
  • iii) Vision
  • iv) Hearing
  • v) Balance & Equilibrium
• General Senses include somatic sensations (tactile, thermal, pain, and proprioceptive) and visceral sensations. They are scattered throughout the body and have simple structures.
• Special Senses include smell, taste, vision, hearing and equilibrium. They are concentrated in specific locations in the head and have anatomically distinct structures. They have complex neural pathways.
• Sensory Receptors


  Conscious and subconscious awareness of changes in the external or internal environment