Lecture 2

• What are the main lines of communication in the nervous system?

  Neurons, brain, and ganglia
• What are the key structures of a neuron?

  • Cell body
  • Axon
  • Dendrites
  • Synapse
  • Neurotransmitter
• What is the role of glial cells in the nervous system?

  They provide physical and chemical support to neurons and maintain their environment
• What is the difference between the central nervous system (CNS) and the peripheral nervous system (PNS)?

  • CNS: brain (cerebrum, cerebellum, brainstem) and spinal cord
  • PNS: everything else that conducts nerve impulses outside of the brain and spinal cord (cranial & spinal nerves; ganglia)

  
• What do sensory neurons do?

  They carry information about changes in the external and internal environment to the CNS
• What is the function of interneurons?


  They connect to brain regions
• What is the role of motor neurons?

  They carry signals away from the CNS towards muscles to cause movement
• Ion Pumps and Channels Basics

  • Ions are unequally distributed between the interior and surrounding fluid
  • The interior of the cell is negatively charged relative to the outside
  • This difference in charge is called membrane potential

  
• What is the resting potential of a neuron?

  Between -60 and -80 mV
• How is resting potential formed in neurons?

  Through the sodium-potassium pump, which transports three Na+ out of the cell for every two K+ in
• What is osmoregulation in oceanic bony fishes?


  • Ion gradients drive salt secretion
  • In gills, pumps and channels expel salt from blood back into salt water
• How does the H+ gradient contribute to locomotion in bacteria?

  • The H+ gradient powers the flagellum
  • When protons re-enter the cell, they provide force that causes the flagellar motor to rotate
• What is a gated ion channel?

  Transmembrane proteins that allow ions to pass through the membrane in response to a stimulus
• What is a voltage-gated ion channel?


  A class of transmembrane protein that forms ion channels activated by changes in electrical membrane potential
• What happens during hyperpolarization?

  The membrane potential becomes more negative at a particular location on the neuron membrane
• What occurs during depolarization?


  The membrane potential becomes less negative (more positive)
• What is the difference between graded potential and action potentials?

  • Graded potential: shift in membrane potential that varies with stimulus strength and decays over time and distance
  • Action potential: massive change in membrane voltage that is constant in magnitude and can regenerate in adjacent regions

  
• How does the frequency of action potentials convey information?

  The frequency is proportional to signal strength
• What are the evolutionary adaptations of axon structure for conduction speed?

  • Wider axons allow less resistance to current
  • Electrical insulation (myelin sheath) increases conduction speed
• What is the role of myelin sheath in vertebrate axons?

  • Provides electrical insulation around the axon
  • Produced by oligodendrocytes in CNS and Schwann cells in PNS
• What are nodes of Ranvier?

  • Periodic gaps in the myelin sheath on axons
  • Facilitate rapid conduction of nerve impulses
• What is saltatory conduction?

  • Propagation of action potentials along myelinated axons from one node of Ranvier to the next
  • Increases conduction velocity of action potentials
• What is a synapse?


  • Place where information is transmitted between neurons
  • Most chemical synapses rely on neurotransmitter release by presynaptic neurons
• What happens to neurotransmitters after they trigger a response at the synapse?

  They are cleared from the synaptic cleft by diffusion or recaptured for recycling
• What are electrical synapses?

  Synapses that rely on the movement of electric current between neurons via junction gaps
• What is an EPSP?

  When depolarization brings the membrane potential toward threshold
• What is an IPSP?


  When the membrane potential moves further from threshold
• What is spatial summation?


  When several synapses occur at the same time, resulting in an additive effect
• What is temporal summation?


  • Occurs when a single EPSP synapse fires again before the resting membrane potential is fully restored
  • Results in an additive effect
• What is a neurotransmitter?

  Chemical messengers that carry messages from one nerve cell to the next
• How many different receptors can a single neurotransmitter bind to?

  More than 12 different receptors
• What is the chief neurotransmitter of the parasympathetic nervous system?


  Acetylcholine (ACh)
• 
  

  Glutamate: one of the several amino acids that can act as a neurotransmitter, is the most common neurotransmitter in the CNS
• What role does glutamate play in the CNS?

  It is the primary excitatory neurotransmitter and is involved in the formation of long-term memory
• What are biogenic amines?

  Neurotransmitters synthesized from amino acids, such as norepinephrine
• What is the role of norepinephrine in the nervous system?

  It is an excitatory neurotransmitter in the autonomic nervous system (PNS)
• What are endorphins?


  Short chain amino acids that act as neurotransmitters and natural pain relievers
• How do opiates affect the body?

  They mimic endorphins and produce similar physiological effects
• What is the role of nitric oxide (NO) in human males?


  It is released by certain neurons into erectile tissue during sexual arousal
• How does Viagra work?

  By inhibiting an enzyme that terminates the action of nitric oxide (NO)