Neuron Structure and Action

Structure and Action of Neurons

• Identify key structural features of a neuron:
  • Cell body
  • Dendrites
  • Axon
• Summarize the changes in resting membrane potential that lead to the initiation and propagation of an action potential:
  • At rest, the membrane potential is polarized at -70mV
  • When positive (Na+) ions flow into the cell, the membrane potential depolarizes, moving closer to 0 mV
  • If the membrane potential reaches -50 mV, an action potential will be triggered
• Describe the "all-or-none" characteristic of an action potential and the Rate Law of action potentials:
  • The neuron firing is "all or none," meaning the frequency of firing determines the strength of the neural signal
  • Strong stimulus leads to faster threshold for activation, resulting in more frequent action potentials

Propagation of Action Potentials

• Ions flow in and out of the neuron membrane in the gaps between the myelin, causing the action potential to move faster

Synapse and Neurotransmission

• Describe the synapse, the mechanism of neurotransmitter release, and the activation of postsynaptic receptors:
  • Synapses enable communication between neurons
  • The structure of a synapse includes the terminal button, synaptic cleft, pre- and post-synaptic membranes, synaptic vesicles, and microtubules
  • Neurotransmitters are synthesized within the brain/neurons and are often called "chemical messengers"
• Explain how drugs influence synaptic transmission and neuron function:
  • Drugs can mimic or block the action of neurotransmitters
  • Agonists activate the receptor, while antagonists block it

Neural Excitation and Inhibition

• Describe excitatory and inhibitory postsynaptic potentials (EPSPs and IPSPs):
  • EPSPs depolarize the postsynaptic cell membrane, increasing the likelihood of an action potential
  • IPSPs hyperpolarize the postsynaptic cell membrane, decreasing the likelihood of an action potential
• Explain how EPSPs and IPSPs are integrated:
  • The combined effect of EPSPs and IPSPs is called neural integration
  • Each neuron integrates the signals from incoming neurons, and the sum of the excitatory inputs must be sufficiently greater than the inhibitory inputs to cause the membrane potential to pass the threshold of activation

Neurotransmitters and Receptors

• Describe the action of neurotransmitters at receptors:
  • Neurotransmitters bind to specific receptors, triggering a response
  • Receptors are very selective, and each receptor can generally only be activated by one neurotransmitter
• Explain how drugs work at receptors:
  • Drugs can act as agonists, activating the receptor like the natural compound, or as antagonists, blocking the receptor and preventing the natural compound from activating it