NERVOUS SYSTEM 2

• Functions of the Nervous System


  • Sensory Input
  • Integration
  • Homeostasis
  • Mental Activity
  • Control of Muscles & Glands
• Divisions of the Nervous System


  • CNS (Central Nervous System)
  • PNS (Peripheral Nervous System)
• Subdivisions of the PNS


  • Sensory Division (Afferent)
  • Motor Division (Efferent)
• Subdivisions of the Motor Division


  • Somatic Motor System
  • Autonomic System
• Branches of the Autonomic System

  • Sympathetic
  • Parasympathetic
• Effector Organs


  • Skeletal muscle
  • Smooth muscle
  • Cardiac muscle
  • Glands
• Neurons


  Receive stimuli and transmit action potentials to other neurons or effector organs
• Neuron Structure


  • Cell body (soma/perikarion)
  • Dendrites
  • Axon
• Types of Neurons


  • Multipolar
  • Bipolar
  • Unipolar
• Neuroglia (Glial Cells)


  • Astrocytes
  • Ependymal
  • Microglia
  • Oligodendrocytes
  • Schwann Cells
  • Satellite Cells
• Resting Membrane Potential


  When no more K+ can diffuse out of the cell because the negative ionic concentration within the cell won't allow it - equilibrium
• Local Current


  Area where Na+ channels briefly open and allow Na+ to rush into the cell - start of depolarization
• Depolarization


  Inside of the cell membrane becomes more positive - leads to a local potential
• Outcomes of Local Potential

  • If threshold is not met repolarization occurs
  • If threshold is met action potential occurs
• Action Potential


  Depolarization then repolarization of the entire cell in an all-or-none fashion - complete charge reversal across the cell membrane - in a nerve cell is non-detrimental (no loss in intensity from beginning to end)
• Action Potential Characteristics


  • Stronger stimulus will produce a greater frequency of action potentials not a greater amount (size of contraction)
  • Differentiation occurs because of frequency of depolarizations - graded response (light touch vs heavy touch)
• Unmyelinated Axons


  Conduct action potentials more slowly because depolarization and repolarization must move area by area (in a localized step-by-step way) across the entire cell (dendrite, soma, & axon) through the cytoplasm - refractory period (repolarization follows depolarization all the way down) - 2 meters per second
• Myelinated Axons


  Conduct action potentials more quickly because the potentials can jump from node to node (Nodes of Ranvier) instead of traveling the whole length of the axon - also called salutatory conduction - 120 meters per second
• Parts of a Synapse

  • Presynaptic terminal
  • Synaptic cleft
  • Postsynaptic membrane
  • Synaptic vesicles
• Neurotransmitters


  • Acetylcholine
  • Norepinephrine
  • Serotonin
  • Dopamine
  • Gamma-aminobutyric
  • Glycine
  • Endorphins
• Components of a Reflex Arc


  • Sensory receptor
  • Sensory neuron
  • Interneuron
  • Motor neuron
  • Effector organ
• Types of Neural Pathways


  • Converging
  • Diverging
• Spinal Cord


  • Located in the vertebral foramen
  • Consists of peripheral white matter and central grey matter
  • Has 3 protective coverings called meninges
• Columns of White Matter

  • Dorsal (posterior)
  • Ventral (anterior)
  • Lateral
• Types of Nerve Tracts


  • Ascending tracts
  • Descending tracts
• Gray Matter


  • Shaped like the letter H with posterior, anterior, and small lateral horns
  • The middle line of the H is called the gray commissure which allows for communication between the horns
• Components of a Spinal Nerve

  • Ventral root
  • Dorsal root
• Spinal Cord Reflexes


  • Stretch reflexes are the simplest reflex, in which muscles contract in response to stretching force
  • Withdrawal reflex (flexor reflex) removes a body part from painful stimulus
• Spinal Nerve Plexuses


  • Cervical Plexus
  • Brachial Plexus
  • Lumbosacral Plexus
• Major Nerves of the Brachial Plexus


  • Axillary nerve
  • Radial nerve
  • Musculocutaneous nerve
  • Ulnar nerve
  • Median nerve
• Major Nerves of the Lumbosacral Plexus


  • Obturator nerve
  • Femoral nerve
  • Tibial nerve
  • Common fibular nerve
• Regions of the Brain


  • Brainstem
  • Cerebrum
  • Cerebellum
  • Diencephalon
• Brainstem


  • Connection of spinal cord to brain
  • Contains several nuclei which control vital functions like heart rate, blood pressure, breathing
  • Damages to small areas can result in death
  • Location of nuclei for all but the first two cranial nerves
• Parts of the Brainstem


  • Medulla Oblongata
  • Pons
  • Midbrain
• Femoral nerve


  • Innervates the anterior thigh muscles and skin over anterior thigh and medial leg
• Tibial nerve


  • Innervates posterior thigh muscles, anterior and posterior leg muscles, most intrinsic foot muscles and skin covering the sole of the foot
• Common fibular nerve


  • Innervates lateral thigh and leg muscles, some intrinsic foot muscles, and skin covering the anterior and lateral leg as-well-as dorsal surface (top) of the foot
• Sciatic nerve - tibial and common fibular nerves bound together in a connective tissue sheath
• Brain - 4 major regions


  • Brainstem
  • Diencephalon
  • Cerebellum
  • Cerebrum
• Brainstem


  • Connection of spinal cord to brain - contains several nuclei which control vital functions like heart rate, blood pressure, breathing - damages to small areas can result in death - location of nuclei for all but the first two cranial nerves