lecture 5 notes

What are the parts of a neuron and their locations?

Neuron cell bodies are found within the Central Nervous System (CNS), in peripheral ganglia, and in the walls of the intestine.

What is the function of dendrites in a neuron?

Dendrites increase the surface area of the neuron cell body and are specialized for receiving synaptic signals from other neurons.

What is the initial segment in a neuron?

The initial segment is the base of the axon that contains a high density of voltage-gated sodium channels, playing a crucial role in generating action potentials.

How do neurons integrate excitatory and inhibitory inputs?

Neurons receive both inhibitory and excitatory inputs, which they sum at any given moment. If the majority of inputs open potassium (K) channels, the membrane potential is pushed towards equilibrium potential for K (Ek), reducing the likelihood of generating an output, indicating an inhibitory signal.

What is the threshold in the context of action potentials?

The threshold is the membrane potential level that must be reached for an excitatory postsynaptic potential (EPSP) to trigger an action potential.

Describe the event that initiates an action potential

An action potential is generated when the membrane depolarization at the initial segment reaches a critical threshold, leading to the opening of voltage-gated sodium channels.

What governs the functioning of voltage-gated sodium channels?

Voltage-gated sodium channels are activated by changes in membrane voltage; they open during depolarization allowing sodium ions to enter the cell, which drives the membrane potential towards sodium equilibrium potential (ENa).

What is the role of voltage-gated potassium channels?

Voltage-gated potassium channels open when the membrane becomes positively charged, allowing potassium (K) ions to flow out of the cell down their electrochemical gradient, repolarizing the membrane towards potassium equilibrium potential (Ek).

What is undershoot in the context of action potentials?

Undershoot refers to the periods during which the membrane potential becomes more negative than the resting membrane potential due to prolonged opening of voltage-gated potassium channels.

What are the absolute and relative refractory periods?

The absolute refractory period is when it is impossible to generate another action potential, while in the relative refractory period, a new action potential can be triggered but is more difficult due to the high concentration of potassium ions within the cell.

What features characterize action potentials?

Action potentials are characterized by being of a consistent size (all-or-none), meaning they do not vary in amplitude; information is conveyed by the frequency of the action potentials, encoding intensity differences between stimuli.

What occurs at the axon terminal once an action potential reaches it?

When an action potential travels to the axon terminal, it triggers the release of neurotransmitters, which can be excitatory or inhibitory, influencing the activity of the next neuron.