Action Potential in Neurons

Action Potential

• Definition: A rapid change in the electrical potential of a cell, typically in excitable tissues such as neurons and muscle cells.
• Characteristics:
  • Depolarization: A rapid increase in the membrane potential from a negative to a positive value.
  • Repolarization: A rapid decrease in the membrane potential back to a negative value.
  • Threshold: The minimum potential required to trigger an action potential.
• Phases:
  1. Resting phase: The membrane potential is at a stable negative value.
  2. Depolarization phase: The membrane potential rapidly increases due to an influx of positively charged ions (Na+).
  3. Repolarization phase: The membrane potential rapidly decreases due to an efflux of positively charged ions (K+).
  4. Refractory period: A period during which the cell is unable to generate another action potential.

Neurophysiology

• Definition: The study of the functions and properties of neurons, including the generation and transmission of electrical signals.
• Key concepts:
  • Dendrites: Receive synaptic inputs from other neurons.
  • Cell body: Contains the nucleus and the majority of the cell's organelles.
  • Axon: Carries the action potential away from the cell body.
  • Terminal buttons: Release neurotransmitters into the synapse.
• Types of neurons:
  • Sensory neurons: Transmit information from sensory receptors to the CNS.
  • Motor neurons: Transmit information from the CNS to muscles or glands.
  • Interneurons: Integrate and process information within the CNS.

Muscle Physiology

• Definition: The study of the functions and properties of muscle tissue, including contraction and relaxation.
• Types of muscle:
  • Skeletal muscle: Voluntary muscle that is attached to bones and helps move the body.
  • Smooth muscle: Involuntary muscle that is found in the walls of hollow organs and helps move substances through them.
  • Cardiac muscle: Involuntary muscle that is found in the heart and helps pump blood.
• Muscle contraction:
  • Excitation-contraction coupling: The process by which an action potential triggers muscle contraction.
  • Sliding filament theory: The theory that muscle contraction occurs due to the sliding of actin and myosin filaments past each other.

Synaptic Transmission

• Definition: The process by which a neuron transmits information to another neuron or to a muscle or gland cell.
• Steps:
  1. Neurotransmitter release: The terminal button of the presynaptic neuron releases neurotransmitters into the synapse.
  2. Neurotransmitter binding: The neurotransmitters bind to receptors on the postsynaptic neuron or muscle cell.
  3. Postsynaptic potential: The binding of neurotransmitters triggers a change in the postsynaptic membrane potential.
  4. Integration: The postsynaptic neuron or muscle cell integrates the information from multiple synaptic inputs.
• Types of synapses:
  • Chemical synapses: Use neurotransmitters to transmit information.
  • Electrical synapses: Use direct electrical connections to transmit information.

Electrophysiology

• Definition: The study of the electrical properties of cells and tissues, including the generation and transmission of electrical signals.
• Techniques:
  • Electrophysiology recording: The use of electrodes to record electrical activity from cells or tissues.
  • Patch clamp: A technique used to record electrical activity from individual ion channels.
• Concepts:
  • Ion channels: Proteins that allow ions to flow across the cell membrane.
  • Membrane potential: The electrical potential difference across the cell membrane.
  • Electrical conduction: The transmission of electrical signals through tissues.

Action Potential

• Rapid change in electrical potential of a cell, typically in excitable tissues such as neurons and muscle cells.
• Characteristics: depolarization, repolarization, and threshold.
• Phases: resting phase, depolarization phase, repolarization phase, and refractory period.

Phases of Action Potential

• Resting phase: stable negative membrane potential.
• Depolarization phase: rapid increase in membrane potential due to influx of positively charged ions (Na+).
• Repolarization phase: rapid decrease in membrane potential due to efflux of positively charged ions (K+).
• Refractory period: period during which the cell is unable to generate another action potential.

Neurophysiology

• Study of functions and properties of neurons, including generation and transmission of electrical signals.
• Key concepts: dendrites, cell body, axon, and terminal buttons.
• Dendrites receive synaptic inputs from other neurons.
• Cell body contains the nucleus and the majority of the cell's organelles.
• Axon carries the action potential away from the cell body.
• Terminal buttons release neurotransmitters into the synapse.

Types of Neurons

• Sensory neurons: transmit information from sensory receptors to the CNS.
• Motor neurons: transmit information from the CNS to muscles or glands.
• Interneurons: integrate and process information within the CNS.

Muscle Physiology

• Study of functions and properties of muscle tissue, including contraction and relaxation.
• Types of muscle: skeletal muscle, smooth muscle, and cardiac muscle.
• Skeletal muscle: voluntary muscle that is attached to bones and helps move the body.
• Smooth muscle: involuntary muscle that is found in the walls of hollow organs and helps move substances through them.
• Cardiac muscle: involuntary muscle that is found in the heart and helps pump blood.

Muscle Contraction

• Excitation-contraction coupling: process by which an action potential triggers muscle contraction.
• Sliding filament theory: theory that muscle contraction occurs due to the sliding of actin and myosin filaments past each other.

Synaptic Transmission

• Process by which a neuron transmits information to another neuron or to a muscle or gland cell.
• Steps: neurotransmitter release, neurotransmitter binding, postsynaptic potential, and integration.
• Neurotransmitter release: terminal button of the presynaptic neuron releases neurotransmitters into the synapse.
• Neurotransmitter binding: neurotransmitters bind to receptors on the postsynaptic neuron or muscle cell.
• Postsynaptic potential: binding of neurotransmitters triggers a change in the postsynaptic membrane potential.
• Integration: postsynaptic neuron or muscle cell integrates the information from multiple synaptic inputs.

Types of Synapses

• Chemical synapses: use neurotransmitters to transmit information.
• Electrical synapses: use direct electrical connections to transmit information.

Electrophysiology

• Study of electrical properties of cells and tissues, including the generation and transmission of electrical signals.
• Techniques: electrophysiology recording, patch clamp.
• Concepts: ion channels, membrane potential, and electrical conduction.
• Ion channels: proteins that allow ions to flow across the cell membrane.
• Membrane potential: electrical potential difference across the cell membrane.
• Electrical conduction: transmission of electrical signals through tissues.