Question

Graded potentials can

a) Only act as signals over short distances.
b) Only act as signals over long distances.
c) Only cause or prevent an action potential.
d) Act as signals over short distances and cause or prevent an action potential.
e) Act as signals over long distances and cause or prevent an action potential.

Answer 1

Graded potentials act as signals over short distances and can cause or prevent an action potential; they vary in size based on the strength of the stimulus and include generator, receptor, and postsynaptic potentials.

Step-by-step explanation:

Graded potentials are local changes in the membrane potential of a neuron's dendrites that are caused by various stimuli. These changes can be depolarizing or hyperpolarizing and their size depends on the size of the stimulus that causes it. Graded potentials include generator potentials, which occur in the dendrites of unipolar sensory neurons and can directly generate an action potential, and receptor potentials in specialized sensory cells that cause neurotransmitter release without an action potential. Additionally, there are postsynaptic potentials (PSPs), with excitatory PSPs depolarizing the membrane and inhibitory PSPs hyperpolarizing it.

Regarding the question's multiple-choice options, graded potentials fulfill several roles. They are instrumental in the signaling process that can lead to action potentials, depending on whether the summation of these local signals is enough to reach the threshold needed for an action potential. Notably, graded potentials act as signals over short distances and cannot carry signals across long distances like action potentials can due to their decremental nature.

Therefore, the correct choice for the question is: