Ion Channels and Depolarization

Ion Channels

• Ion channels are proteins embedded in the neuronal membrane that regulate the flow of ions (charged particles) in and out of the cell.
• There are two main types of ion channels:
  • Voltage-gated ion channels: open or close in response to changes in the membrane potential.
  • Ligand-gated ion channels: open or close in response to binding of a neurotransmitter or other signaling molecule.

Depolarization

• Depolarization is the decrease in the negative charge of the membrane potential, making it less negative.
• This occurs when there is an influx of positively charged ions (e.g. Na+ or Ca2+) or an efflux of negatively charged ions (e.g. K+).
• Depolarization can be triggered by:
  • Excitatory neurotransmitters binding to ligand-gated ion channels.
  • The opening of voltage-gated ion channels.

Neurotransmission

• Neurotransmission is the process by which a neuron communicates with another neuron or a muscle cell.
• This occurs when an action potential reaches the end of the neuron and releases neurotransmitters into the synapse.
• The neurotransmitters then bind to receptors on the postsynaptic neuron, causing a change in the membrane potential.

Repolarization

• Repolarization is the return of the membrane potential to its resting state, making it more negative.
• This occurs when there is an efflux of positively charged ions (e.g. K+) or an influx of negatively charged ions (e.g. Cl-).
• Repolarization is essential for the neuron to recover and be ready for another action potential.

Threshold Potential

• Threshold potential is the minimum membrane potential required to trigger an action potential.
• When the membrane potential reaches the threshold potential, voltage-gated ion channels open, allowing an influx of positively charged ions and triggering an action potential.
• The threshold potential is typically around -55mV to -70mV in most neurons.

Ion Channels

• Embedded in neuronal membrane to regulate ion flow in and out of the cell
• Two main types: voltage-gated and ligand-gated
• Voltage-gated: open or close in response to changes in membrane potential
• Ligand-gated: open or close in response to binding of neurotransmitter or signaling molecule

Depolarization

• Decrease in negative charge of membrane potential
• Occurs when positively charged ions (e.g. Na+, Ca2+) flow in or negatively charged ions (e.g. K+) flow out
• Triggers: excitatory neurotransmitters binding to ligand-gated ion channels or opening of voltage-gated ion channels

Neurotransmission

• Process of neuron communication with another neuron or muscle cell
• Occurs when action potential reaches end of neuron and releases neurotransmitters into synapse
• Neurotransmitters bind to receptors on postsynaptic neuron, changing membrane potential

Repolarization

• Return of membrane potential to resting state
• Occurs when positively charged ions (e.g. K+) flow out or negatively charged ions (e.g. Cl-) flow in
• Essential for neuron recovery and preparing for another action potential

Threshold Potential

• Minimum membrane potential required to trigger action potential
• Typically around -55mV to -70mV in most neurons
• Reached when voltage-gated ion channels open, allowing influx of positively charged ions and triggering action potential