Neuron functions and more neuron types

Q: What maintains the resting membrane potential in neurons?

A: Separation of charge: negative inside, positive outside the membrane.

Q: What are graded potentials, and where do they occur?

A: Small, brief voltage changes in dendrites/soma; size matches stimulus strength.

Q: What causes an action potential to fire?

A: Summation of graded potentials reaches threshold at the trigger zone.

Q: How do action potentials differ from graded potentials?

A: They are all-or-none, large, uniform, and travel long distances.

Q: What increases the speed of action potential conduction?

A: Large axon diameter and myelination.

Q: What happens at the axon terminal?

A: Neurotransmitters are released into the synaptic cleft.

Q: What is the role of afferent neurons?

A: Carry sensory information into the CNS.

Q: What is the role of efferent neurons?

A: Send motor or autonomic signals from the CNS to the periphery.

Q: What do interneurons do?

A: Connect neurons to each other within the CNS.

Q: What are end feet of astrocytes responsible for?

A: Structural support, blood-brain barrier maintenance, neurotransmitter clearance.

Q: What is a glial scar (astrogliosis)?

A: Astrocyte reaction to CNS injury; they wall off the damaged area.

Q: How do astrocytes maintain CNS homeostasis?

A: Regulate ion levels and release lactate into interstitial fluid.

Q: What activates resting microglia?

A: Inflammation or tissue damage in the CNS.

Q: What immune functions do active microglia perform?

A: Phagocytosis and antigen presentation.

Q: What is antigen presentation in microglia?

A: Display of digested debris to stimulate immune responses.

Q: What do ependymal cells produce and move?

A: Cerebrospinal fluid (CSF); cilia help circulate it.

Q: What barrier do ependymal cells form?

A: A leaky barrier between CSF and interstitial fluid.

Q: What type of epithelium are ependymal cells?

A: Simple cuboidal.

Q: How do oligodendrocytes myelinate CNS axons?

A: One cell wraps segments on multiple axons.

Q: What are nonmyelinating oligodendrocytes?

A: Glia that do not form myelin sheaths.

Q: How do Schwann cells differ from oligodendrocytes?

A: Each Schwann cell myelinates only one axon segment in the PNS.

Q: What are nonmyelinating Schwann cells?

A: Cells with troughs where small PNS axons rest.