6.2.3 Synaptic Transmission

• What are the three main components of a synapse?

  Presynaptic neuron, cleft, postsynaptic neuron
• What is the synaptic cleft?

  Gap between neurons
• Where are receptors located in a synapse?

  Postsynaptic membrane
• Steps in the release of neurotransmitters

  1️⃣ Calcium influx

  2️⃣ Vesicle fusion

  3️⃣ Exocytosis
• Neurotransmitters diffuse across the synaptic cleft to reach receptors.
• What triggers the release of neurotransmitters into the synaptic cleft?

  Calcium influx
• What is the effect of excitatory receptors on the postsynaptic neuron?

  Increase firing likelihood
• Where are neurotransmitters released into during neurotransmission?

  Synaptic cleft
• What is signal transduction?

  Converting one signal to another
• In indirect signaling, second messengers like cAMP or IP3 activate enzymes such as kinases
• Calcium ions trigger the fusion of neurotransmitter-filled vesicles with the presynaptic membrane.


  True
• Which neurotransmitter binds to ion channel receptors in direct signaling?

  Acetylcholine
• Second messengers produced during indirect signaling include cAMP
• Steps in indirect signaling

  1️⃣ Neurotransmitter binds to GPCRs

  2️⃣ G proteins are activated

  3️⃣ Second messengers are produced

  4️⃣ Kinases are activated
• Acetylcholinesterase is an enzyme that degrades the neurotransmitter acetylcholine
• Excitatory neurotransmitters such as glutamate increase the likelihood of the postsynaptic neuron firing an action potential
• Match the neurotransmitter type with its effect on the postsynaptic neuron:

  Excitatory ↔️ Increases likelihood of action potential

  Inhibitory ↔️ Decreases likelihood of action potential

  Neuromodulatory ↔️ Modulates neuronal activity over time
• Chemical synapses are separated by a synaptic cleft
• Steps in neurotransmitter release

  1️⃣ Calcium influx

  2️⃣ Vesicle fusion

  3️⃣ Exocytosis
• The influx of calcium ions triggers the fusion of neurotransmitter-containing vesicles with the presynaptic membrane.


  True
• Match the receptor type with its effect on the postsynaptic neuron:

  Excitatory Receptors ↔️ Increase likelihood of action potential

  Inhibitory Receptors ↔️ Decrease likelihood of action potential
• Receptors are crucial for neurotransmission as they bind neurotransmitters and trigger a response in the postsynaptic neuron.


  True
• Which neurotransmitter binds to inhibitory receptors in the brain to reduce neuronal activity?

  GABA
• Signal transduction is the process by which a cell converts one type of signal into another
• What is a second messenger activated by G protein-coupled receptors in indirect signal transduction?

  cAMP
• Acetylcholinesterase breaks down acetylcholine into acetate and choline
• Which type of neurotransmitter decreases the likelihood of the postsynaptic neuron firing an action potential?

  Inhibitory
• Electrical synapses are connected via gap junctions
• What is the primary role of synaptic transmission in the nervous system?

  Neuron communication
• Order the roles of synaptic transmission in the nervous system.

  1️⃣ Facilitates neuron communication

  2️⃣ Transports sensory information

  3️⃣ Drives muscle control

  4️⃣ Supports higher cognitive functions
• Vesicles in the presynaptic neuron contain neurotransmitters
• Diffusion is the primary mechanism by which neurotransmitters travel across the synaptic cleft


  True
• Calcium ions (Ca2+) flow into the presynaptic terminal after an action potential.
• What is exocytosis in synaptic transmission?

  Release of neurotransmitters
• Calcium ions are essential for the fusion of vesicles with the presynaptic membrane


  True
• Receptors on the postsynaptic membrane can either excite or inhibit the neuron.
• GABA is an inhibitory neurotransmitter that reduces neuronal activity


  True
• Excitatory receptors increase the likelihood of the postsynaptic neuron firing an action potential.

  True
• Steps in indirect signaling during signal transduction:

  1️⃣ Neurotransmitter binds to GPCRs

  2️⃣ G proteins are activated

  3️⃣ Second messengers are produced

  4️⃣ Enzymes like kinases are activated
• Which part of the synapse releases neurotransmitters into the synaptic cleft?

  Presynaptic neuron