OVERVIEW

• Functions of Nervous System: 1. Sensory input: sensory receptors respond to stimuli 2. Integration: brain and spinal cord process stimuli 3. Control of muscles and glands 4. Mental activity: brain 5. Homeostasis
• CELLS OF THE NERVOUS SYSTEM

  (Neuron)

  (Characteristics)

  • Nerve cells
  • Require oxygen and glucose
  • Receive input, process input, produce a response
• Neuron Structures

  • Dendrite: receives stimulus from other neurons or sensory receptors
  • Cell body: processes stimulus; contains a nucleus
  • Axon: transmits stimulus to a gland, muscle, organ, or other neuron
• Types of Neurons 8.2.1.3.1 Multipolar -"many dendrites and a single axon Ex. CNS and most motor neurons
• Types of Neurons

  Bipolar

  • many dendrites and a single axon
  • Ex. CNS and most motor neurons
• Types of Neurons

  Pseudo-Unipolar

  • one axon and no dendrites
  • Ex. Sensory neurons
• Glial Cells

  • Supporting cells for neurons
  • More numerous than neurons
  • Can divide to produce more cells
  • 5 types
• Types of Neuroglia 8.2.2.1.1 Astrocytes

  • star-shaped
  • most abundant
  • form blood-brain barrier (BBB)
• Types of Neuroglia

  Ependymal Cells

  • produce and circulate cerebrospinal fluid (CSF)
• Types of Neuroglia

  Microglia

  • help remove bacteria and cell debris from CNS
• Types of Neuroglia

  Oligodendrocytes

  • produce myelin sheath in CNS
• Types of Neuroglia

  Schwann cells

  • produce myelin sheath in PNS
• Myelin Sheaths - fatty, protective wrapping around axons and excellent insulator
• Nodes of Ranvier - gaps in myelin sheath where action potentials develop
• Saltatory conduction:

  • jumping of action potentials
  • Myelinated axons conduct action potentials more quickly (3-15 meters/sec) than unmyelinated due to Nodes of Ranvier
• Clinical Correlation: Multiple sclerosis - disease of myelin sheath that causes loss of muscle function
• Organization of Nervous Tissue: Gray matter - collection of dendrites and cell bodies White matter - collection of axons and their myelin sheath
• Resting Membrane Potential

  • Outside of cell is more + (Na+)
  • Inside of cell is more – (K+)
• Leak ion channels:

  • always open
  • K+ channels
• Gated ion channels:

  • closed until opened by specific signal
  • Na+ channels
• Action Potential

  • “Electricity” that cause depolarization and repolarization
  • Change resting membrane potential by activating gated ion channels
• Local Current: movement of Na+ which causes inside of cell to be more positive (depolarize)

  • If enough Na+ enters then threshold is reached and more Na+ channels open
• • Once threshold is reached all or none law applies
  • Action potentials continue until Na+ channels close, K+ channels open, and repolarization occurs
  • Sodium/potassium pump restores
• Synapse - where an axon attaches to a muscle, gland, organ, or other neuron involved with release of neurotransmitters

  Ex. Neuromuscular junction
• Reflexes - involuntary response to a stimulus
• Reflex arc- path reflex travels
• Components of Reflex Ars:

  1.Sensory receptors:

  • pick up stimulus
  • in skin 2. Sensory (afferent) neurons:
  • send stimulus to interneurons in spinal cord 3. Interneurons (Association) neuron:
  • located in CNS and connect to motor neurons
  • process stimulus 4. Efferent (motor) neurons:
  • send response to effector 5. Effector: muscle, gland, or organ
• Converging

  • two or more neurons synapse same neuron
  • allows info. to be transmitted in more than one
  • neuronal pathway to converge into a single pathway
• Diverging

  • axon from one neuron divides and synapses with more than one neuron
  • allows info. to be transmitted in one neuronal pathway to diverge into 2 or more pathways