receptors

Upcoming Test Information

• Test Date: Tuesday, the 25th

• Test Type: Test One

• Resources Available:

  • Prep materials on Canvas

  • Practice questions

  • Podcasts available for review

Action Potential

• Movement along the Axon: Action potentials can travel via two methods.

• Myelin:

  • Myelin is a fatty substance that insulates the axon.

  • No voltage-gated channels in the myelin segments.

• Nodes of Ranvier:

  • The gaps in the myelin sheath are called nodes.

  • Action potential jumps from node to node (saltatory conduction) for faster transmission.

  • Distance between nodes optimized to reach threshold potential (about -55mV).

Action Potential Dynamics

• The influx of sodium ions at nodes initiates the action potential.

• Action potentials occur via:

  • Graded potentials being subthreshold (less frequent) or superthreshold (more frequent).

  • Stronger stimuli generate more frequent action potentials.

Electrical to Chemical Communication

• Neurons Interaction:

  • When neurons communicate, action potentials reach synaptic bulbs, releasing neurotransmitters.

• Synaptic Transfer:

  • Action potential opens voltage-gated calcium channels.

  • Calcium ions enter the presynaptic neuron, triggering neurotransmitter release through exocytosis.

• Presynaptic vs. Postsynaptic cells:

  • Presynaptic neurons release neurotransmitters.

  • Postsynaptic neurons have receptors that respond to these neurotransmitters.

Key Concepts in Neurotransmitter Function

• Neurotransmitter Types:

  • Excitatory Neurotransmitters enable action potentials, while Inhibitory Neurotransmitters prevent them.

  • Example: Acetylcholine released at synapses is excitatory, binding to cholinergic receptors.

• Receptor Types:

  • Cholinergic receptors can be nicotinic (excitatory) or muscarinic (varying effects).

Inhibitory Mechanisms

• Acetylcholinesterase: Enzyme that breaks down acetylcholine in the synaptic cleft to prevent continuous stimulation.

Summary of Action Potentials' Characteristics

• Differences between graded potentials and action potentials:

  • Action potentials are all-or-nothing responses, while graded potentials vary in strength.

  • Action potentials travel long distances; graded potentials are limited to local effects.

Action Potential and Signal Coding

• The frequency of action potentials encodes the strength of a stimulus.

• Different types of ion channels contribute to excitatory or inhibitory postsynaptic potentials (EPSP or IPSP).

Closing Remarks

• Understanding the intricate details of action potentials, neurotransmitter function, and synaptic transmission is crucial for comprehending neural communication.