Essentials

A neuron fires if the the RMP + stimulus is greater than the threshold. Since −70 + 10 = −60 and −60 is NOT greater than −50, there is no action potential.

Additional Information

RMP is the resting membrane potential which is the electrochemcial difference when the cell is at equilibrium. Threshold is the minimum potential that must reach the axon hillock to trigger an action potential. Max potential is the most positive mV the cell reaches. Max potential is not needed to determine whether or not a neuron will fire.

Essentials

Acceptable answers are:

• Trigger zone/trigger zones
• Action potential/action potentials
• Tight junction/tight junctions
• Threshold
• Axon/axons

In order for your answer to have been marked correct, you needed to have at least 2 correct and 0 wrong.

Additional Information

The axon hillock is the part of the cell where membrane potentials from the dendrites are propagated to. If the potential is above the threshold at this point, then an action potential is created.

Essentials

A neuron fires if the the RMP + stimulus is greater than the threshold. In order to cross the threshold of −50, we need a stimulus of 20 (and a little) mV. Since we round to the nearest whole number, the answer is 20 mV. If the RMP was less negative than the threshold, then no stimulus would be needed - 0 mV.

Additional Information

If and only if the membrane potential crosses the threshold will an action potential be generated. Once an action potential is created, an all−or−none response is created.

Essentials

When channels are present, then we're able to establish an RMP as ions move in and out passively due to the electrochemical gradient and actively due to the sodium−potassium pump.

For additional practice, what would the relative concentrations be when the cell is depolarized?

Essentials

Local Potentials	Action Potentials
Graded Reversible Decremental Local Potential can be depolarizing or hyperpolarizing	All or none Irreversible Nondecremental Self-propagating Always depolarization

Additional Information

Local potentials occur on the dendrites and travel down towards the axon hillock. Local potentials can be positive (EPSPs) or negative (IPSPs). While traveling, local potentials lose their strength so not every local potential turns into an action potential.

An action potential occurs along the axon and travels towards the axon terminal. As it travels, more sodium and potassium gates open up, which allows it to self-propagate while also limiting the frequency of action potentials (absolute refractory period).

Essentials

Somatic effectors target skeletal muscles. Visceral effectors target glands, smooth muscles, and cardiac muscles.

Essentials

The adrenal medulla's sympathetic pathway still receives input from the preganglionic neuron but instead releases norepinephrine into the blood.

Additional Information

Essentials

These four cranial nerves belong to the parasympathetic system. If you had to pick one to know and memorize, the vagus nerve would be it. It's important to be able to recognize which cranial nerves are part of the parasympathetic nervous sytem.

Essentials

Norepinephrine is the neurotransmitter we normally associate with the sympathetic division of the nervous system. The sympathetic division is responsible for the fight-or-flight response. Under such conditions, we'd want to increase our heart rate to increase oxygen delivery to our tissues to outrun (maybe) a dinosaur.

Additional Information

Acetylcholine is the neurotransmitter we normally associate with the parasympathetic division of the nervous system. The parasympathetic division is responsible for the rest-and-digest response. What might happen to our heart rate if we added ACh?

Norepinephrine and acetylcholine with respect to the heart is an example of dual innervation - innervation by both the sympathetic and parasympathetic. What's another example of dual innervation that we've talked about?

Essentials

Cones are photoreceptor cells that detect color. Cones function under bright light. Rods are photoreceptor cells that function under low-light.

I remember that cones detect color because both start with C. I remember that they function under bright light because you see colors best when it is bright. Rods are all the opposite.