Resting membrane potential and Action potentials

What are the three functional classes of neurons?

Afferent, efferent, interneurons.

What are key characteristics of neurons?

Long-lasting, nondividing, high-energy use.

Why do neurons need constant oxygen and glucose?

They use lots of energy.

What is the direction of Na+ electrical and concentration forces?

Both inward; low membrane permeability.

What is the direction of K+ electrical and concentration forces?

Electrical inward; concentration outward.

What determines membrane potential?

Ion gradients, permeability, and the Na+/K+ pump.

What determines membrane permeability?

Types and numbers of ion channels.

Which leak channels are more numerous at rest?

K+ leak channels.

Why is the inside of a resting cell negative?

K+ leakage and the Na+/K+ pump.

What is the Na+/K+ ATPase ratio?

3 Na+ out, 2 K+ in.

What are the approximate ion gradients listed in the study guide?

K+: 150 and 5; Na+: 15 mM.

How does K+ diffusion affect membrane potential?

K+ moves out; negative charge pulls it in.

What does the Na+/K+ pump mainly do?

Maintains ion gradients.

What is the Nernst equation used to determine?

An ion’s equilibrium potential.

What is an equilibrium potential?

When electrical and concentration forces balance.

What are excitable tissues?

Nerve and muscle tissue.

What are the two broad electrical signal types?

Graded potentials and action potentials.

What can electrical signals do in excitable tissues?

Carry messages and trigger contractions.

What kinds of events can trigger membrane responses?

Sound, light, chemicals, or electrical changes.

What must happen before an action potential begins?

The membrane reaches threshold.

Where does the action potential usually begin?

The axon hillock.

What are the four action potential phases?

Depolarization, peak, repolarization, hyperpolarization.

What causes depolarization?

Na+ enters the cell.

What occurs at the action potential peak?

Na+ channels close; K+ channels open.

What causes repolarization?

K+ leaves the cell.

What causes hyperpolarization?

Extra K+ leaves the cell.

What does all-or-none mean for action potentials?

Threshold reached means a full action potential.

Can a neuron produce multiple action potentials?

Yes, each has the same size.

What does nondecremental propagation mean?

The signal does not weaken.

How fast is a nerve action potential in the review slide?

About 0.001 second.

What is the absolute refractory period?

Another action potential cannot start.

What is the relative refractory period?

A stronger stimulus is needed.

Why does the relative refractory period occur?

K+ movement makes firing harder.

What is the study guide's summary of refractory periods?

Na+ channels reset; K+ causes extra negativity.

What triggers neurotransmitter release from a terminal?

Ca2+ enters after an action potential.

What do SNARE proteins do?

Help vesicles release neurotransmitters.

How are neurotransmitter signals ended?

Enzymes break them down or they are reabsorbed.

Does every neuron release the same neurotransmitter?

No, neurons release specific neurotransmitters.

What is an EPSP?

Excitatory signal; makes firing more likely.

Which ions can enter to create an EPSP in the study guide?

Na+, Ca2+, and Mg2+.

What is an IPSP?

Inhibitory signal; makes firing less likely.

Which ion movements can create an IPSP?

Cl- enters or K+ leaves.

What ion movement is shown for depolarizing postsynaptic potentials?

Positive charge enters.

What ion movements hyperpolarize a postsynaptic cell?

K+ leaves or Cl- enters.

What is acetylcholine (ACh)?

A neurotransmitter.

What enzyme degrades ACh?

Acetylcholinesterase (AChE).

Where can ACh be found?

Pre- and postsynaptic membranes.

What does sarin nerve gas interfere with?

Acetylcholinesterase.

What are the two ACh receptor types?

Nicotinic and muscarinic.

What is serotonin derived from and what does it do?

Tryptophan; affects mood and appetite.

How does serotonin activity vary with alertness and sleep?

Lower during sleep, higher when alert.

What do serotonin uptake blockers do according to the review?

Keep serotonin in the synapse.

What is associated with excess dopamine?

Schizophrenia, according to the review.

What is associated with dopamine deficiency?

Parkinson’s disease.

What is glutamate?

The main excitatory brain neurotransmitter.

What is GABA?

The main inhibitory brain neurotransmitter.

How do GABA receptors affect the membrane?

Cl- enters; the cell becomes more negative.

What drugs also bind to GABA-related receptors in the review?

Xanax and Valium.

What is glycine's role?

Inhibits signals in the spinal cord and brainstem.

What neurotransmitter process is linked with long-term potentiation and learning in the review?

The review links glycine-related cooperation with learning.

What are possible drug effects at a synapse?

Change release, breakdown, reuptake, or receptors.

What are the two types of action potential conduction?

Contiguous and saltatory.

What determines propagation to adjacent membrane?

Whether nearby membrane reaches threshold.

How does axon diameter affect conduction?

Larger axons conduct faster.

How do unmyelinated fibers conduct?

Contiguous conduction.

What is myelin made of and what does it do?

Lipid insulation around axons.

What are benefits of myelination?

Faster signals and less energy use.

Which cells make myelin in the CNS?

Oligodendrocytes.

Which cells make myelin in the PNS?

Schwann cells.

What are Nodes of Ranvier?

Gaps in myelin with many Na+ channels.

What is saltatory conduction?

Signals jump between nodes.

What is multiple sclerosis (MS)?

An autoimmune disease that damages myelin.

What age range is listed for MS symptom onset?

About 20–40 years.

What happens to myelin in MS?

Scars form; signals slow or stop.

What MS symptoms are listed in the review?

Vision problems, numbness, weakness, poor coordination.

What does the study guide say MS can affect?

Impulse speed, reflexes, and senses.

What is axonal transport?

Movement along axons using kinesin and dynein.