Action Potential 101

What is an action potential?

• A slow, permanent electrical signal in neurons

• A rapid, temporary electrical signal that travels along the membrane of a neuron

• A chemical signal that travels between neurons

• A static electrical charge in muscle fibers

In muscle contraction, what role does an action potential play?

• It releases sodium ions from the sarcoplasmic reticulum

• It travels along the sarcolemma, triggering the release of calcium ions

• It inhibits the release of calcium ions

• It causes the sarcolemma to contract directly

Answer explanation

In muscle contraction, an action potential travels along the sarcolemma, which triggers the release of calcium ions from the sarcoplasmic reticulum, essential for muscle contraction.

What is released from the sarcoplasmic reticulum during muscle contraction?

• Sodium ions (Na+)

• Potassium ions (K+)

• Calcium ions (Ca²⁺)

• Chloride ions (Cl-)

Answer explanation

During muscle contraction, calcium ions (Ca²⁺) are released from the sarcoplasmic reticulum. These ions play a crucial role in triggering the contraction process by interacting with the contractile proteins.

What is one reason why action potentials are important in the body?

• They allow neurons to rapidly transmit signals over long distances.

• They slow down muscle contractions.

• They prevent cognitive functions.

• They block sensory perception.

Answer explanation

Action potentials are crucial because they enable neurons to quickly transmit signals across long distances, facilitating communication within the nervous system and allowing for rapid responses to stimuli.

What principle do action potentials follow?

• All-or-none principle

• Partial-response principle

• Gradual-response principle

• Incremental principle

Answer explanation

Action potentials follow the all-or-none principle, meaning they either occur fully or not at all. This principle ensures that once a threshold is reached, the neuron fires completely, without partial responses.

What happens if the threshold for an action potential is not reached?

• An action potential does not occur at all.

• An action potential occurs partially.

• An action potential occurs gradually.

• An action potential occurs incrementally.

Answer explanation

If the threshold for an action potential is not reached, the neuron does not depolarize sufficiently, resulting in no action potential occurring at all. This means the signal is not transmitted.

What is an action potential?

• A slow rise and fall in voltage across a cellular membrane

• A rapid rise and subsequent fall in voltage or membrane potential across a cellular membrane

• A constant voltage across a cellular membrane

• A decrease in voltage across a cellular membrane

Answer explanation

An action potential is characterized by a rapid rise and subsequent fall in voltage across a cellular membrane, which is essential for nerve signal transmission. This distinguishes it from slower or constant voltage changes.

What is required to initiate a voltage response in a cell membrane?

• Insufficient current

• Sufficient current

• No current

• Excessive current

Answer explanation

A voltage response in a cell membrane requires a sufficient current to depolarize the membrane. Insufficient or excessive current will not effectively initiate this response, making 'sufficient current' the correct choice.

What happens if the current is insufficient to depolarize the membrane to the threshold level?

• An action potential will fire

• The membrane will become hyperpolarized

• An action potential will not fire

• The membrane will depolarize automatically

Answer explanation

If the current is insufficient to reach the threshold, the membrane will not depolarize enough to trigger an action potential. Therefore, an action potential will not fire.

Which types of cells are specialized for the conduction of electrical information?

• Neurons and muscle fibers

• Red blood cells and white blood cells

• Skin cells and bone cells

• Liver cells and kidney cells

Answer explanation

Neurons are specialized for transmitting electrical signals in the nervous system, while muscle fibers conduct electrical impulses to trigger contraction. Thus, neurons and muscle fibers are the correct answer.