Nervous System: Graded and Action Potentials

The difference in electrical charge between the inside and outside of a neuron's membrane.

The uneven distribution of ions, like sodium (Na+) and potassium (K+), across the neuron's membrane.

How easily ions can pass through the neuron's membrane, controlled by channels that act like gates.

Specialized proteins embedded in the neuron's membrane that open and close to allow specific ions to pass through.

The movement of ions across the membrane due to both concentration gradients and membrane permeability.

The ease with which ions flow through a channel.

The opening of a channel to allow ion flow.

The closing of a channel even when the activating stimulus continues.

The flow of electrical charge carried by an ion through a channel.

A type of potential that can be either excitatory or inhibitory, occurring mainly in dendrites and soma.

The process of a membrane potential becoming more positive.

The process of a membrane potential becoming more negative.

A graded potential that increases the likelihood of an action potential.

The area where an axon terminal meets its target cell, enabling communication between neurons.

The neuron that transmits the signal across the synapse.

The neuron that receives the signal from the presynaptic neuron.

The small gap between the presynaptic axon terminal and the postsynaptic cell.

The type of synapse where the axon terminal communicates with a dendrite of the postsynaptic neuron.

The type of synapse where the axon terminal communicates with the cell body of the postsynaptic neuron.

The region of the neuron where action potentials are initiated.

The fatty substance that insulates axons, speeding up the conduction of action potentials.

The gaps in the myelin sheath that allow action potentials to jump between nodes.

The mode of action potential conduction along myelinated axons, where the signal 'jumps' from node to node.

A type of synapse where electrical signals directly pass between cells through gap junctions, allowing for rapid and synchronized communication.

A type of synapse where chemical messengers (neurotransmitters) are released from the presynaptic neuron and bind to receptors on the postsynaptic cell, triggering a response.

Specialized channels formed by proteins (connexons) that directly link the cytoplasm of two cells, allowing for the flow of ions and small molecules.

Chemical messengers released by neurons that transmit signals across synapses, binding to receptors on target cells.

A neurotransmitter that is released at neuromuscular junctions, triggering muscle contraction.

Amino acids that act as neurotransmitters in the central nervous system, playing crucial roles in excitatory and inhibitory signaling.

A major excitatory neurotransmitter in the central nervous system, involved in learning, memory, and synaptic plasticity.

A major inhibitory neurotransmitter in the central nervous system, helping to regulate brain activity.

A group of neurotransmitters formed by modifying amino acids, including dopamine, norepinephrine, and serotonin, often involved in mood, emotions, and arousal.

Purines are a type of nitrogenous base found in nucleic acids. ATP (adenosine triphosphate) is an important energy carrier in cells. ADP (adenosine diphosphate) and AMP (adenosine monophosphate) are molecules involved in energy metabolism.

NO (nitric oxide) and CO (carbon monoxide) are gases with signaling roles in the body. They are called gasotransmitters and act as neurotransmitters.

Endorphins are neuropeptides, which means they are chains of amino acids linked together. They act as natural painkillers in the body.

Action potentials are electrical signals that travel along neurons. They have a fixed strength and follow an "all-or-none" principle, meaning they either fire completely or not at all.

The activation of voltage-gated sodium channels is responsible for the generation of an action potential. This means that the opening of these channels allows sodium ions to flow into the neuron, causing depolarization.

Repolarization of an action potential is caused by the opening of voltage-gated potassium channels. This allows potassium ions to flow out of the neuron, restoring the membrane potential.

During the absolute refractory period, a neuron cannot generate another action potential no matter how strong the stimulus is. This ensures that the signal travels in one direction along the neuron.

Gated channels are proteins embedded in the cell membrane that open or close in response to stimuli such as changes in voltage, chemical signals, or physical pressure. This allows for controlled movement of ions across the membrane.

Voltage-gated sodium (Na+) channels are concentrated at the Nodes of Ranvier, the gaps in the myelin sheath along an axon. This arrangement allows for rapid propagation of action potentials as the signal jumps from one node to the next.

The action potential travels along the axon without losing strength due to the sequential activation of voltage-gated sodium channels at each Node of Ranvier. This is referred to as "saltatory conduction".

The "all-or-none" principle states that an action potential either fires completely or not at all, regardless of the strength of the stimulus, as long as it reaches the threshold. So, as long as the stimulus triggers the threshold, the action potential will always fire with the same intensity.

The amplitude of an action potential remains consistent throughout its propagation down the axon, regardless of the strength of the initial stimulus, as long as the stimulus reaches the threshold. The action potential doesn't get stronger or weaker, it simply travels.

A "graded potential" refers to a localized change in the membrane potential that can vary in amplitude depending on the strength of the stimulus. They are typically triggered by stimuli like neurotransmitters.

A "threshold" is the minimum level of depolarization needed to trigger an action potential. It's like a tipping point where the cell commits to firing an action potential.

Sodium ions (Na+) rush into the cell through open voltage-gated Na+ channels during depolarization, causing the membrane potential to become more positive and generating the action potential.

Potassium ions (K+) move out of the cell through open voltage-gated potassium channels during repolarization, causing the membrane potential to return to its resting state. This helps restore the balance after the sodium influx.