Lecture 2/28

What direction does the action potential travel due to the inactivation gate and refractory period?

The action potential can only travel forward.

What ion must enter the neuron to hit threshold during an action potential?

Sodium (Na+) must enter the neuron.

What happens to the sodium channels at peak potential during an action potential?

The sodium channels inactivate.

Why is the action potential always the same magnitude?

Because of the inactivation gate closing at a certain voltage.

What determines the strength of the signal in the nervous system?

The number of neurons activated and the frequency of their firing.

What type of gated channels are found in the axon?

Voltage-gated sodium channels.

What type of gated channels are found on the cell body and dendrites?

Chemically gated channels.

What is the role of calcium in muscle contraction?

Calcium binds to troponin to initiate muscle contraction.

What are the two types of muscle fibers mentioned that have different metabolic capacities?

Type I and Type II (fast twitch) motor fibers.

What is the significance of the refractory period during an action potential?

It ensures that action potentials only travel in one direction.

How does a weak stimulus differ from a strong stimulus in terms of activating motor fibers?

A strong stimulus is required to activate fast twitch type II motor fibers.

What is the result of stimulating an action potential at the axon hillock?

An action potential is generated and travels down the axon.

What indicates a stronger signal when comparing soft and loud sounds?

Higher frequency of action potentials and more sensory neurons activated.

How do chemically gated channels differ from voltage-gated channels?

Chemically gated channels can be either excitatory or inhibitory, while voltage-gated channels are always excitatory.

What happens to the membrane potential as the action potential propagates through the cell body?

The change in membrane potential decreases due to cytoplasmic resistance.

What must happen to the ion channels for an action potential to reset?

The membrane potential must drop below a certain threshold.

What allows the inactivation gate of sodium channels to reset?

The membrane potential needs to decrease sufficiently to enable a conformational change.