2 nervous system

• What gives the plasma membrane its electrical properties?

  Ionic differences across the membrane and its selective ion permeability
• Which ion is the plasma membrane more permeable to?

  K+
• How does the resting membrane potential depend on K+?

  It depends on K+ diffusion out of the cell

  
• What is hyperpolarization in neurons?

  When the cytoplasm becomes more negative

  
• What factors can cause hyperpolarization?

  Exit of K+ and Cl- entry
• What is depolarization in neurons?

  When the cytoplasm becomes more positive

  
• What factors can cause depolarization?

  Na+ entry, Ca2+ entry, and changes in extracellular K+
• What are graded potentials?

  Small and localized changes on the membrane potential of dendrites

  
• How are the sizes of graded potentials related to stimuli?

  The size of graded potentials is proportional to the strength of the stimulus
• What is summation in the context of graded potentials?

  A second depolarizing stimulus occurs before the first disappears, leading to a larger depolarization
• What is the threshold for generating an action potential?

  • 55 mV

  
• What is temporal summation?

  The frequency of graded potentials received by the postsynaptic cell
• What is spatial summation?

  The proximity between graded potentials and their distance from the axon hillock
• Where is the action potential generated?

  At the axon's trigger zone, which has a high density of voltage-gated channels

  
• What is the nature of action potentials?

  They are large changes in membrane potential that propagate along the axon without changing magnitude

  
• What happens during the influx of Na+ through voltage-gated channels?

  It leads to depolarization of the membrane

  
• What is the absolute refractory period?

  It is the period during which the neuron is insensitive to further stimuli until repolarization is complete

  
• What is the relative refractory period?

  A stronger-than-threshold stimulus can initiate another action potential

  
• How does stimulus strength affect action potential frequency?

  The action potential frequency increases with the strength of the stimulus up to a maximal value

  
• What is continuous conduction in unmyelinated axons?

  It is the propagation of action potentials along the axon without myelin

  
• What is saltatory conduction in myelinated axons?

  It is the jumping of action potentials from node to node

  
• What factors affect the propagation speed of action potentials?

  Presence of myelin, thickness of myelin sheath, and axon diameter
• What is a synapse?

  A contact point between two cells
• What are the two types of synapses?

  Chemical and electrical synapses
• What occurs at a chemical synapse?

  The action potential triggers the opening of voltage-gated Ca2+ channels, leading to neurotransmitter release

  
• What are the steps involved in neurotransmitter release at a chemical synapse?

  1. Action potential arrives at the presynaptic terminal
  2. Voltage-gated Ca2+ channels open
  3. Influx of Ca2+ stimulates exocytosis of neurotransmitters
  4. Neurotransmitters bind to receptors on the postsynaptic membrane

  
• What are the characteristics of neurotransmitters?

  1. Synthesized in neurons and stored in synaptic vesicles
  2. Must be stimulated by an action potential for exocytosis
  3. Must bind to a specific receptor on the postsynaptic membrane
  4. Must evoke a response in the postsynaptic cell

  
• What are the two major categories of neurotransmitters?

  Ionotropic and metabotropic neurotransmitters
• What is an excitatory postsynaptic potential (EPSP)?

  It is the depolarization of the postsynaptic membrane due to Na+ permeability

  
• What is an inhibitory postsynaptic potential (IPSP)?

  It is the hyperpolarization of the postsynaptic membrane due to K+ and Cl- permeability

  
• What are neuromodulators?

  Substances released from neurons that influence the likelihood of an action potential being produced in the postsynaptic cell
• What is an axoaxonic synapse?

  A synapse between two axons in the CNS
• How does neuronal communication integrate multiple signals?

  Through the integration of excitatory and inhibitory signals

  
• What is temporal summation in neuronal communication?

  The frequency of action potentials received by the postsynaptic cell

  
• What is spatial summation in neuronal communication?

  The special distribution of action potentials received by the postsynaptic cell