Ch12p4

• What is a synapse?

  Site of communication between a neuron and another cell
• What are the types of synapses?

  • Electrical
  • Chemical
• What is the difference between electrical and chemical synapses?

  Electrical synapses have direct contact; chemical do not
• Where are electrical synapses commonly found?

  In the eye and some brain areas
• How is a signal transmitted across a synapse?

  By chemical neurotransmitters across the synaptic cleft
• What happens in an electrical synapse when an action potential occurs?

  Action potential is always produced in the postsynaptic cell
• What determines if an action potential is produced in a chemical synapse?

  Amount and type of neurotransmitter released
• What is the first step in the chemical synapse process?

  Action potential arrives and depolarizes synaptic knob
• What occurs after neurotransmitter molecules are released in a chemical synapse?

  Neurotransmitter crosses synaptic cleft and binds to receptor
• What happens when ion channels open in a chemical synapse?

  Graded potential is produced in the postsynaptic cell
• What restores the resting potential membrane after neurotransmitter action?

  Neurotransmitter is removed from the synaptic cleft
• What neurotransmitter is used in cholinergic synapses?

  Acetylcholine (ACh)
• Where are cholinergic synapses commonly found?

  Neuromuscular junctions and many CNS synapses
• What happens when ACh binds to its receptor?

  Na+ enters, depolarizing the membrane
• What is the role of AChE in cholinergic synapses?

  AChE breaks down ACh into acetate and choline
• What are excitatory neurotransmitters responsible for?

  Causing depolarization of postsynaptic membranes
• What do inhibitory neurotransmitters do?

  Cause hyperpolarization of postsynaptic membranes
• What is the effect of ACh on skeletal muscle cells?

  Produces EPSPs by opening Na+ channels
• What is the effect of ACh on cardiac muscle cells?

  Produces IPSPs by opening K+ channels
• What is summation of postsynaptic potentials (PSPs)?

  • Integration of EPSPs and IPSPs
  • Occurs in the postsynaptic neuron
  • Influences action potential generation
• What is spatial summation?

  Stimuli occur at different locations on the membrane
• What is temporal summation?

  Stimuli occur at the same location but at different times
• What factors influence information processing at the cellular level?

  • Temperature
  • Oxygen/nutrients
  • Abnormal chemicals
  • Regulatory neurons
• What are some major neurotransmitters?

  Norepinephrine, serotonin, dopamine, glutamate, GABA
• What is the role of norepinephrine?

  Involved in consciousness and attention
• What is serotonin associated with?

  Mood, emotions, and body temperature
• What is dopamine's role in the brain?

  Motor control and reward system
• What is glutamate's function in the brain?

  Involved in memory and learning
• What is GABA's effect on neurons?

  Has an inhibitory effect on neurons
• What happens during synaptic fatigue?

  Neurotransmitter cannot be recycled fast enough
• What is synaptic delay?

  0.2-0.5 milliseconds between action potential and effect
• How does the number of synapses affect response time?

  Fewer synapses lead to faster response
• What is the relationship between reflexes and synapses?

  • Many reflexes involve only one synapse
  • Fewer synapses result in quicker reflex responses